Liquid crystal elastomers are a class of soft materials that can change shape in response to stimuli such as light or heat — making them promising for applications in soft robotics, wearable and biomedical devices, smart textiles and more. But designing compositionally uniform elastomers that can change into different shapes in response to just one stimulus has been challenging and has limited the application of these potentially powerful materials.&nbsp;Now, researchers from the&nbsp;<a href="https://seas.harvard.edu/">Harvard John A. Paulson School of Engineering and Applied Sciences</a> (SEAS) have developed a way to program liquid crystal elastomers with the ability to deform in opposite directions just by heating — opening up a range of applications.&nbsp;The research was published in&nbsp;<a href="https://www.science.org/doi/10.1126/science.adq6434" target="_blank">Science</a>.&nbsp;“We have shown that by encoding multiple phase transitions within a single material, we can create scalable, easy to fabricate systems capable of achieving various deformations and shape changes without the need of complex designs or composite materials,” said&nbsp;<a href="https://seas.harvard.edu/person/joanna-aizenberg">Joanna Aizenberg</a>, the Amy Smith Berylson Professor of Materials Science and Professor of Chemistry &amp; Chemical Biology at SEAS and senior author of the paper.&nbsp;The team used an approach that combined theoretical modeling,&nbsp;chemical modifications, and mechanics of polymer-polymer interactions to design the system. They began by orienting liquid crystal monomers, which could be bonded together to form polymer chains, along one direction in a magnetic field. The monomers, which were designed with long molecular tails and long linkers, would dangle at the side of polymer chains — like the pendulum of a clock.When exposed to UV light, the oriented molecules tether together and form polymer chains. The process of polymerization contracts and puts strain on the material, squeezing those aligned monomers into a zig-zag, chevron-like pattern of polymers.&nbsp;The researchers found that when they increased the temperature, those chevron-shaped polymers flattened and stacked into flat layers. If they increased the temperature further, those layers transformed into a randomly coiled state — like a pile of spaghetti. When they lowered the temperature back down, the random polymers reformed into flat layers then back into chevrons.&nbsp;“With soft actuators, we need deformations to be reversible so we can cycle them many, many times,” said Milan Wilborn, a PhD candidate in Aizenberg’s lab and co-first author of the paper. &nbsp;“And we demonstrated that we can switch between these three phases at high frequency, moving quickly between each deformation state.”The researchers also demonstrated that by aligning the molecules in different directions before polymerization, they could encode different shape changes into the material, including flat sheets that move like the fins of stingrays and jellyfish by morphing into saddles and domes. &nbsp;“What is so powerful about this research is we have this single, soft material which can achieve opposite deformations. So at room temperature, the material is flat, then it forms a saddle when the polymers are stacked in flat layers and then transforms into a dome when the polymers become random,” said Wilborn. “We’re really excited about using these materials as soft actuators for bioinspired motions.”These transformations respond to not only temperature, but also light and solvent, making them useful for applications from smart textiles to temperature-regulating robotic skins.&nbsp;This research was co-authored by Yuxing Yao, Baptiste Lemaire, Foteini Trigka, Friedrich Stricker, Alan H. Weible, Shucong Li, Robert K. A. Bennett, Tung Chun Cheung, Alison Grinthal, Mikhail Zhernenkov, Guillaume Freychet, Patryk Wąsik, Boris Kozinsky, Michael M. Lerch and Xiaoguang Wang.It was supported by the US Department of Energy, Office of Science, Basic Energy Sciences and the Harvard University Materials Research Science and Engineering Center (MRSEC).

Researchers encode multiple shapes into simple material

Shape-changing soft material for soft robotics, smart textiles and more

In the holiday movie The Grinch, makeup artists are reported to have spent several hours each day encasing Jim Carrey’s face with prosthetics to create the iconic grumpy, green-furred creature. Such elaborate prosthetics, often made possible by materials like silicone rubbers, may have now found an unexpected yet beneficial biomedical engineering application, according to a new study from Texas A&amp;M University.<a href="https://www.nature.com/articles/s41598-024-76652-y" rel="noopener" target="_blank">Published in the journal Scientific Reports</a>,&nbsp;researchers have created realistic, skin-like replicas made of Ecoflex, a type of silicone rubber that can potentially serve as a platform to evaluate risks of bacterial infections from intravenous catheters and test wearable sensors, among other biomedical applications. The study found that EcoFlex-based skin replicas can be engineered to mimic actual skin textures, wettability, and elasticity, simulating the conditions where bacteria grow and adhere.“We think that the material holds tremendous promise for studying infections at the insertion site due to bacteria that are naturally occurring on the skin,” said Majed Othman Althumayri, a graduate student in the Texas A&amp;M Department of Biomedical Engineering and primary author of the paper. “Our goal was to create a skin-like material with ingredients that can be purchased off the shelf. Ecoflex is not just easy to use, it can be cured quickly with minimum additional steps, making it very convenient.”&nbsp;There are roughly a million bacteria per square centimeter of human skin. The most common of them is Staphylococcus, particularly the species Staphylococcus epidermidis, which is considered a typical resident of the skin microbiome. Infections often happen when there is a cut, break or wound on the skin, allowing the bacteria to enter the bloodstream. In fact, a relatively common infection in hospitals comes from surgically inserting tubes or catheters into veins. Each year, around 80,000 catheter-related bloodstream infections happen in intensive care units alone, underscoring its public health significance in the United States.“We have been slow in finding solutions for preventing infections from intravenous catheters,” said Althumayri. “A reason could be that we lack good platforms to test new catheter designs or &nbsp;wearable biosensor technologies and train staff so that the number of infections can be reduced.”&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734481767784-News-BMEN-Hands3Long-16Dec2024.jpg" style="width: 100%px;" class="fr-fic fr-dib">Hand replica made of Ecoflex. | Image:&nbsp;<cite id="isPasted">Courtesy of Majed Othman Althumayri</cite>To address this gap, the researchers turned to Ecoflex 00-35, a fast-curing, biocompatible rubber used for various applications, including prosthetics for special effects. First, they created molds of common intravenous insertion sites, such as the elbows, hands and forearms. Then, by pouring Ecoflex into the molds that contained artificial bones and tubes acting as veins, the researchers created skin-like replicas.&nbsp;Next, the researchers tested if the Ecoflex skin replicas had properties that matched that of real skin. They measured the replicas’ wettability, bacterial adhesion and mechanical properties, such as elasticity and resilience. The researchers found that the Ecoflex models could replicate human skin roughness within a 7.5% error margin. Further, high-resolution imaging showed that bacteria could adhere to the skin replica and grow on it.&nbsp;Then, in a key experiment, the researchers simulated an intravenous catheter insertion into an Ecoflex hand replica that they created. This artificial hand effectively modeled phases of bacterial growth, showing promise that these replicas can be used for implementing infection control measures and improving the design of medical devices like catheters.However, the researchers noted that their current experiments do not entirely model real-world conditions.&nbsp;“Developing realistic skin models that can mimic the human skin is an important initial step,” said Dr. Hatice Ceylan Koydemir, corresponding author on the study and assistant professor in the Department of Biomedical Engineering with a research program housed within the Texas A&amp;M University Center for Remote Health Technologies and Systems. “But we think that incorporating additional elements, like body fluids and other clinically relevant situations, in future experiments will bolster our findings and further validate Ecoflex’s potential for medical applications.”Other contributors to the research include Azra Yaprak Tarman, a graduate student in the Department of Biomedical Engineering.This study was partly sponsored by the National Institute of General Medical Sciences (one of the National Institutes of Health), the Department of Defense Office of Naval Research and the National Science Foundation-funded&nbsp;<a href="https://tees.tamu.edu/research/initiatives/paths-up.html" rel="noopener" target="_blank">Engineering Research Center PATHS-UP</a>. Researchers also received additional support from the Department of Biomedical Engineering, the Center for Remote Health Technologies and Systems, the Texas A&amp;M Engineering Experiment Station, the AggieFab Nanofabrication Facility, and the Soft Matter Facility.

Graduate student Majed Othman Althumayri demonstrates an Ecoflex cast of his hand. | Image: Emily Oswald/Texas A&M Engineering

In a new study, Texas A&M researchers have used a skin-like material as a platform for investigating infections from intravenous catheters.

Prosthetic Material Could Help Reduce Infections from Intravenous Catheters

Let's start with the Properties of Aluminum AlSi10Mg (3.2382)1. High Strength and Hardness: AlSi10Mg is renowned for its high strength and hardness. The addition of magnesium and silicon enhances its mechanical properties, making it suitable for applications that require both durability and strength.2. Good Thermal Properties: The alloy exhibits excellent thermal conductivity, which is crucial for applications in high-temperature environments. This property makes it effective in managing heat dissipation, especially in components subjected to thermal stresses.3. Good Processability: The presence of silicon in AlSi10Mg improves the viscosity of the melt pool during additive manufacturing. This enhances the alloy's processability compared to pure aluminum, allowing for more precise and efficient 3D printing.4. High Corrosion Resistance: AlSi10Mg offers excellent resistance to corrosion, which is essential for parts exposed to harsh environments. This property ensures the longevity and reliability of components, especially in aerospace and automotive applications.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734430992551-2-min.jpg" style="width: 100%px;" class="fr-fic fr-dib"> Applications of Aluminum AlSi10Mg (3.2382)1. Aviation and Aerospace: In the aerospace industry, AlSi10Mg is valued for its high strength-to-weight ratio, thermal conductivity, and corrosion resistance. It is commonly used in structural components, engine parts, and other critical applications where performance and reliability are paramount.2. Automotive: The alloy is used in automotive parts where high strength and lightweight properties are essential. It is particularly useful for producing parts that need to withstand stress while contributing to overall vehicle efficiency.3. Prototype Cast Parts: AlSi10Mg is ideal for producing prototype cast parts. Its good processability and mechanical properties make it suitable for creating functional prototypes that can be tested in real-world conditions.4. Serial Parts: The alloy is also used in serial production, where it can be employed to manufacture components in bulk. Its ability to maintain strength and quality over large production runs makes it a popular choice for various serial applications.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734430973728-1-min.jpg" style="width: 100%px;" class="fr-fic fr-dib"> Physical and Mechanical PropertiesTensile Strength: In its as-built condition, AlSi10Mg exhibits a tensile strength of approximately 400 N/mm². This high strength ensures that parts made from this alloy can endure significant stresses and loads.Heat Treatment: The alloy can undergo a P6 heat treatment process to achieve enhanced ductility. This treatment allows for improved performance in applications where flexibility and resistance to cracking are important. To sum it up..Aluminum alloy AlSi10Mg (3.2382) stands out in metal 3D printing for its high strength, good thermal properties, and excellent processability. Its suitability for aviation, automotive, and prototype applications highlights its versatility and reliability. As industries continue to innovate and push the boundaries of material performance, AlSi10Mg remains a key material, offering a blend of strength, processability, and durability for a wide range of advanced manufacturing needs.

AlSi10Mg (3.2382) is a high-performance material widely used in metal 3D printing for various advanced applications. Let's take an in-depth look at its properties, applications, and mechanical characteristics.

Aluminum AlSi10Mg (3.2382) in Metal 3D Printing: Key Insights

In this guide, we cover all the different types of polymer FDM 3D printing filament, from standard grades like PLA and ABS to advanced high-performance filaments like PEEK and fiber-reinforced materials.

What Material Is Used for 3D Printing? A Guide to Polymer FDM Filaments

<h2 id="isPasted">Understand the Future of Metal 3D Printing</h2>The Metal 3D Printing Technology Report is your essential guide to the latest advances, applications, and real-world insights into additive manufacturing with metal. Packed with detailed case studies, &nbsp;practical information, and interviews with industry leaders, this report reveals how metal 3D printing is transforming industries and pushing the boundaries of manufacturing.Read the intro to the report <a href="https://www.wevolver.com/article/metal-3d-printing-technology-report">here</a> and an excerpt from chapter 4 below.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734355340345-froala_1733828027720-5%2BRising%2BTrends%2Bfor%2BAI%2BAdoption%2Bin%2BManufacturing%2B%281920%2Bx%2B500%2Bpx%29.png" style="width: 100%px;" class="fr-fic fr-dib"><iframe id="JotFormIFrame-243032488553458" title="Metal 3D Printing Report" allowtransparency="true" src="https://form.jotform.com/243032488553458" frameborder="0" style="min-width: 100%; max-width: 100%; height: 690px; border: none;" scrolling="yes" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true"> </iframe><h2 dir="ltr">Introduction</h2>Metal 3D printing opens up design opportunities due to its high level of geometrical freedom. However, like all technologies, it requires design for manufacturability (DFM) considerations, taking into account the physical constraints of the equipment and materials. In 3D printing, this design strategy is referred to as design for additive manufacturing (DfAM). Most major CAD software providers provide DfAM tools (as well as 3D printing simulation tools), as 3D printing hardware is now widespread.<h3 dir="ltr">Design opportunities</h3>Compared to other metal manufacturing processes like machining, casting, and forging, 3D printing offers a number of design advantages, including:<ul><li dir="ltr">Design freedom: Designs are unhindered by cutting tool access and other conventional manufacturing constraints; limitations (e.g. support structures to support overhangs) are minimal in comparison.<ul><li dir="ltr">Multi-axis design freedom: Some DED systems offer multi-axis material deposition, enabling printing of unsupported overhangs and further design freedom.</li></ul></li><li dir="ltr">Internal structures: Additive process allows for complex internal geometries and precise density control, giving a high level of control over part strength, weight, flexibility, and other characteristics, as well as allowing for cooling and fluid flow channels.</li><li dir="ltr">Lightweighting: Partly hollow designs allow for lightweighting of parts that would otherwise be conventionally manufactured.</li><li dir="ltr">Organic shapes: Generative design software can create complex, interlocking, or curved parts that mimic organic shapes.</li><li dir="ltr">Part consolidation: Metal 3D printing can be used to consolidate assemblies into simple parts, increasing production efficiency, improving performance, and increasing part service life.</li></ul><h3 dir="ltr">Design limitations</h3>Metal 3D printing offers a high level of design freedom, but it suffers from a handful of limitations. Some of these are technology-specific. For example, design for metal extrusion is governed by the limitations of both polymer extrusion printing and part sintering. Some limitations in metal 3D printing design include:<ul><li dir="ltr">Thermal stresses: Since most metal 3D printing technologies require high temperatures, part design must minimize thermal stresses. This may be achieved by introducing corner radii, avoiding thin sections, etc.</li><li dir="ltr">Shrinkage: Several metal 3D printing technologies require sintering, which results in part shrinkage as voids are removed. This should be factored into design to ensure part dimensions fall within acceptance tolerances.</li><li dir="ltr">Trapped powder: Powder bed processes can result in powder trapped within hollow sections unless design allows the powder to escape.</li><li dir="ltr">Overhangs, bridges, supports: Supports are often required to support overhangs and bridges. Top-heavy or unbalanced designs may sag or deform during sintering or heat treatment.</li><li dir="ltr">Feature size: Processes like extrusion and binder jetting have a limited minimum feature size.</li></ul><h2 dir="ltr">Tools for DfAM</h2>Advanced CAD software may include tools for metal 3D printing design such as design validation, performance analysis, lattice generation, and topology optimization. Simulation tools for validating designs may be incorporated into CAD, CAE, CAM, or distinct process simulation software. Simulation of 3D printing processes typically involves advanced thermal modeling. Research shows that both topology optimization and generative design tools can be adopted at the early stages of 3D printing design to either create a geometry driven by functional requirements or to redesign components to make them lighter and stronger.<h3 dir="ltr">Generative design</h3>Generative design is the use of algorithmic software to create novel designs based on user-defined constraints. It is generally employed during the conceptual design stage. While generative design is not unique to metal 3D printing, metal 3D printing is one of the few processes that can easily realize a broad range of generated designs. Altair Sulis is one example of a DfAM tool that uses generative design to generate AM-optimized designs.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733927613980-design+for+metal.png" style="width: 100%px;" class="fr-fic fr-dib">3D Systems company Oqton’s 3DXpert industrial 3D printing software. Image credit:&nbsp;<a href="https://oqton.com/posts/3dxpert-space-exploration/" id="isPasted">Oqton</a><h3 dir="ltr">Topology optimization</h3>Topology optimization is a design strategy for optimizing the structure of a printed part, generally to reduce weight while maintaining strength. Unlike generative design, it is used to optimize specified shapes instead of creating designs from scratch. As with generative design, however, the freeform nature of 3D printing means that most designs can be realized. Software such as 3D Systems 3DXpert provides topology optimization tools for metal printing.<h3 dir="ltr">Lattice generation</h3>Lattice structures are a key feature of metal 3D printing as they serve to maximize strength and minimize mass and cannot easily be produced using other manufacturing processes. Software can be used to automatically generate printable lattice structures within predefined boundaries. Siemens NX CAD is an example of an application that incorporates lattice generation for metal 3D printing design.<h2 dir="ltr">Get your report now</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734355363801-froala_1733828027720-5%2BRising%2BTrends%2Bfor%2BAI%2BAdoption%2Bin%2BManufacturing%2B%281920%2Bx%2B500%2Bpx%29.png" style="width: 100%px;" class="fr-fic fr-dib"><iframe id="JotFormIFrame-243032488553458" title="Metal 3D Printing Report" allowtransparency="true" src="https://form.jotform.com/243032488553458" frameborder="0" style="min-width:100%;max-width:100%;height:690px;border:none;" scrolling="yes" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true"> </iframe><a href="https://www.wevolver.com/article/metal-3d-printing-technology-report"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734355421527-1734355421527.png" class="fr-fic fr-dii"></a> <a href="https://www.wevolver.com/article/chapter-1-core-metal-3d-printing-technologies"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734355370353-1734355370353.png" class="fr-fic fr-dii"></a><a href="https://www.wevolver.com/article/the-metal-3d-printing-technology-report-chapter-1-core-metal-3d-printing-technologies"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734355370459-1734355370459.png" class="fr-fic fr-dii"></a><a href="https://www.wevolver.com/article/the-metal-3d-printing-technology-report-chapter-3-post-processing-for-metal-am"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1734355370376-1734355370376.png" class="fr-fic fr-dii"></a>

Metal 3D printing offers significant design opportunities with its high geometrical freedom, but it requires careful design for additive manufacturing (DfAM) to address equipment and material constraints, a process supported by DfAM and 3D printing simulation tools in most major CAD software.

The Metal 3D Printing Technology Report: Chapter 4: Design for Metal 3D printing

From entry-level FDM machines to industrial-grade metal printers, this guide demystifies the many types of 3D printers available to businesses and consumers.

Types of 3D Printers: The Ultimate Guide to Additive Manufacturing Technologies

<h2 id="isPasted">Understand the Future of Metal 3D Printing</h2>The Metal 3D Printing Technology Report is your essential guide to the latest advances, applications, and real-world insights into additive manufacturing with metal. Packed with detailed case studies, &nbsp;practical information, and interviews with industry leaders, this report reveals how metal 3D printing is transforming industries and pushing the boundaries of manufacturing.Read the intro to the report <a href="https://www.wevolver.com/article/metal-3d-printing-technology-report">here</a> and an excerpt from chapter 3 below.&nbsp;<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzMzODI4MDc1ODA0LTUgUmlzaW5nIFRyZW5kcyBmb3IgQUkgQWRvcHRpb24gaW4gTWFudWZhY3R1cmluZyAoMTkyMCB4IDUwMCBweCkucG5nIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 100%px;" class="fr-fic fr-dib"><iframe id="JotFormIFrame-243032488553458" title="Metal 3D Printing Report" allowtransparency="true" src="https://form.jotform.com/243032488553458" frameborder="0" style="min-width: 100%; max-width: 100%; height: 630px; border: none;" scrolling="no" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true">&nbsp;&nbsp; </iframe>Metal additive manufacturing generally requires extensive post-processing to achieve fully dense, usable parts. Processes that deposit metal mixed with a binder matrix (binder jetting, extrusion) are the most dependent on post-processing to achieve desired part characteristics, since the as-printed (green) parts are not fully metal. However, all processes, including powder bed fusion and DED, require some degree of post-processing.In this chapter, we separate metal AM post-processing into four categories: debinding and sintering, CNC machining and milling, heat treatment, and quality assurance. (Another essential process, support removal, is not included due to its relative simplicity.) The first three of the three categories are concerned with the physical alteration of the printed parts to bring about the desired shape or material characteristics, while quality assurance is concerned with inspection. Metal 3D printing workflows may use any combination of the described post-processing techniques or other workflow-specific techniques not mentioned here.<h3 dir="ltr">Debinding and sintering</h3>Printed metal parts made using binder jetting or material extrusion consist of both metal and a sacrificial binder material, so the binder must be removed to create a true metal part (as with metal injection molding (MIM)) before sintering to strengthen and densify the part. Exceptions include HP’s Metal Jet binder jetting technology, whose binder decomposes during sintering and which therefore does not require debinding. Sintering results in a degree of (anisotropic) part shrinkage, which must be factored into part design.Binder is removed from metal parts using catalytic, solvent, thermal debinding, or a combination of the three. The appropriate method generally depends on the material and its binder.<div dir="ltr" align="left"><table><tbody><tr><td>Process</td><td>Description</td><td>Advantages</td><td>Disadvantages</td></tr><tr><td>Catalytic debinding</td><td>Uses catalytic acid vapor, typically 98.5% nitric acid gas, to turn binder into vapor that can be blown away</td><td>Fastest method</td><td>Environmental and safety risks</td></tr><tr><td>Solvent debinding</td><td>Uses liquid organic solvents like hexane to remove binder</td><td>Fast method</td><td>Requires complex preparation and planning</td></tr><tr><td>Thermal debinding</td><td>Uses furnace to slowly soften binder and enable its removal</td><td>Simplest and safest method</td><td>Slow and can introduce stresses to metal</td></tr></tbody></table></div>A key advantage of thermal debinding is that the same furnace can be used for debinding and sintering. A lower temperature is used for debinding (usually under 500°C) before a higher temperature is introduced for sintering (usually above 1000°C). Several 3D printer manufacturers supply debinding and sintering furnaces that can be used for post-processing of metal parts. Another advantage of thermal debinding is that furnaces can be brought in-house with relative ease. By contrast, parts that require catalytic debinding (those produced using BASF Ultrafuse filament, for example) may need to be shipped to a third-party debinding specialist.Debinding and sintering equipment producers include:<ul><li dir="ltr">Desktop Metal: Introduced its PureSinter high-purity vacuum in 2024, which is capable of sintering titanium to 98% density. Compatible with binder jetting, material extrusion, and traditional techniques like MIM.</li><li dir="ltr">Markforged: Supplies the Wash 1 solvent debinding station (along with a separate sintering furnace) for use with its Metal X 3D printer. Uses Opteon SF-79 solvent.</li><li dir="ltr">The Virtual Foundry: Wisconsin company supplying Filamet metal filament and sintering kilns (Virtual Foundry, FireX, FireX Max) with temperatures up to 1288°C.</li></ul><h3 dir="ltr">Heat treatment</h3>The rapid heating and cooling of metal additive manufacturing processes produce “heterogeneous microstructures and the accumulation of internal stresses,” the effect of which can be reduced via heat treatment. Heat treatment can remove internal stresses and improve hardness and fatigue strength. Without heat treatment, 3D printed metal parts are significantly outperformed by traditionally made (machined, cast, forged) equivalents. Heat treatment can be applied to parts made using a variety of technologies, including LPBF, DED, and binder jetting.Different heat treatment processes may suit different metals. Some of the major heat treatment processes for 3D printed metal parts are outlined in the table below. Other processes like annealing, normalizing, and precipitating hardening may also be used on certain metals.<div dir="ltr" align="left"><table><tbody><tr><td>Process</td><td>Description</td></tr><tr><td>Solution treatment</td><td>Heating of parts to high temperature followed by rapid cooling</td></tr><tr><td>Stress relieving</td><td>Heating of parts followed by controlled cooling to alleviate residual stresses</td></tr><tr><td>Hot isostatic pressing (HIP)</td><td>Simultaneous isostatic pressurization and heating of parts to high temperature to densify and remove internal defects</td></tr></tbody></table></div>A handful of companies specialize in the heat treatment of metal 3D printed parts, providing services or manufacturing hardware such as furnaces and presses. Most companies in this field are established and previously provided heat treatment for conventionally manufactured metal parts.Heat treatment companies include:<ul><li dir="ltr">Paulo: Missouri-based heat treatment expert founded in 1943. Provides HIP and other services.&nbsp;</li><li dir="ltr">Quintus Technologies: High-pressure machine manufacturer based in Sweden. Supplies HIP equipment to Paulo and others.</li></ul><h3 dir="ltr">Surface finishing</h3>Surface finishing technologies and techniques may be used for post-processing of metal parts produced using any metal additive manufacturing technology. Surface finishing techniques include but are not limited to sanding, abrasive blasting, vibratory finishing, dry electropolishing, and CNC machining.<ul><li dir="ltr">Sanding: Metal 3D printed parts may be subject to manual or automated sanding to remove surface imperfections. For parts produced using binder jetting or material extrusion, sanding the green part prior to debinding and sintering can increase surface quality.</li><li dir="ltr">Blasting: Abrasive media blasting is another common post-processing technique for parts produced using LPBF and other technologies. Advantages of media blasting include speed and minimal impact on part dimensions. Media may include glass beads or alumina.</li><li dir="ltr">Vibratory finishing: Tumbling is used to smooth the surface of metal parts and increase hardness. It requires less manual supervision than media blasting and can produce equivalent or better results. Chemically accelerated vibratory surface finishing or superfinishing is a related low-cost process in which a chemical solution is used to coat the metal, helping to remove peaks while maintaining valleys.</li><li dir="ltr">Dry electropolishing: The patented DryLyte process from DLyte uses an electrical flow to create an ion exchange that removes material only from roughness peaks, keeping edges intact and accessing hard-to-reach corners.</li><li dir="ltr">Machining:&nbsp;CNC machining can be used to turn near-net-shape parts into final parts, achieve tighter tolerances on critical features, improve dimensional accuracy, and produce the desired surface finish. Suitable machines include 3-axis, 4-axis, and 5-axis machining (milling) centers, as well as electrical discharge machining (EDM) centers.</li></ul><h3 dir="ltr">Quality assurance</h3>Quality assurance is an important area of post-processing for metal parts, particularly end-use or production parts in fields like aerospace, as parts must meet regulatory standards set by relevant industrial bodies. Traditional equipment like coordinate measurement machines (CMMs) may be used to assess dimensional accuracy, while internal inspection using CT scanners and other equipment is especially important as the microstructure and porosity of printed metal parts can vary. Automated quality assurance solutions are becoming more common as manufacturers look to make additive manufacturing as efficient as possible on the production line.Key quality assurance processes for metal 3D printing include part measurement using CMMs and non-destructive testing methods like computed tomography (CT), ultrasonic testing, and conductivity testing, which are critical for analyzing the internal structure of printed parts. Other quality assurance processes that are not technically part of the post-processing stage include in-process monitoring, material selection and testing, and statistical process control.<blockquote>“One of the big advantages of designing for metal AM is topology optimization, which allows you to take advantage of minimalist designs and minimal material usage to create the strongest and lightest parts. But you often run into these organic shapes and designs that are very difficult to inspect,” explains Matt Schmidt, Senior Solutions Engineer at Xometry. “How do we know that we have accomplished everything in that print to match the performance that we dictated during the optimization process? For that, 3D scanning becomes very critical, as does high-resolution CMM for evaluating the tolerances of 3D prints. CT and x-ray scans are also very important to study part microstructure and detect any porosity, voids or gaps in parts that could result in potential failures.”</blockquote>Companies providing quality assurance solutions include:<ul><li dir="ltr">QC Labs: Non-destructive testing service provider to additive manufacturing and CNC machining users. Uses various technologies including CT scanning, ultrasonic testing, and digital radiography.</li></ul>Theta Technologies: UK company specializing in non-destructive testing equipment. Its systems use nonlinear resonance technology to detect internal flaws in metal parts.<hr><a href="https://www.wevolver.com/article/metal-3d-printing-technology-report"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733839566614-1733839566614.png" class="fr-fic fr-dii"></a> <a href="https://www.wevolver.com/article/chapter-1-core-metal-3d-printing-technologies"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733839566622-1733839566622.png" class="fr-fic fr-dii"></a><a href="https://www.wevolver.com/article/the-metal-3d-printing-technology-report-chapter-1-core-metal-3d-printing-technologies"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733839566628-1733839566628.png" class="fr-fic fr-dii"></a><a href="https://www.wevolver.com/article/the-metal-3d-printing-technology-report-chapter-3-post-processing-for-metal-am"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733839566634-1733839566634.png" class="fr-fic fr-dii"></a> Get the full report immediatley by downloading below.&nbsp;<img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzMzODI4MTk4MzMwLURPV05MT0FEIEJFTE9XLnBuZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 100%px;" class="fr-fic fr-dib"><iframe id="JotFormIFrame-243032488553458" title="Metal 3D Printing Report" allowtransparency="true" src="https://form.jotform.com/243032488553458" frameborder="0" style="min-width: 100%; max-width: 100%; height: 630px; border: none;" scrolling="no" class="fr-draggable" data-lf-form-tracking-inspected-kn9eq4roawkarlvp="true" data-lf-yt-playback-inspected-kn9eq4roawkarlvp="true" data-lf-vimeo-playback-inspected-kn9eq4roawkarlvp="true">&nbsp;&nbsp; </iframe>

In this chapter, we separate metal AM post-processing into four categories: debinding and sintering, CNC machining and milling, heat treatment, and quality assurance. 

The Metal 3D Printing Technology Report: Chapter 3: Post-processing for Metal AM

An FDM 3D printer is a great tool for making all manner of parts and products. The technology is particularly notable for its ability to create hollow or complex geometries on demand. However, the geometry and design of a print is only part of the equation, materials are a major consideration when planning a 3D printing project. The choice of 3D printing filament will influence all sorts of factors, including the cost of a project, the appearance of a print, and, most importantly, the mechanical properties of the final part. For example, if you are looking to make a flexible object, such as a wearable or gasket, it is imperative that you work with a filament that has flexible properties.Polylactic acid (PLA), while the most commonly used filament today, is not known for its flexibility. In fact, the material is highly rigid and in some cases even brittle. This means that it can fracture when stressed, with little deformation before breaking. In this article, we’ll be diving deeper into PLA’s properties to understand if it can be more flexible. We’ll also be looking at flexible filaments that can be used as an alternative to PLA when flexibility is needed.<h2 dir="ltr">PLA filament properties&nbsp;</h2>Neat PLA filament is a rigid thermoplastic known for its easy printability and high strength. Despite a tensile strength of around 50 MPa (<a href="https://www.wevolver.com/article/comparison-of-pla-abs-and-petg-filaments-for-3d-printing" target="_blank">ABS, for comparison has a tensile strength of about 30 MPa</a>), PLA is rigid, offering little flexibility and can actually become more brittle if subjected to stress over time or under extreme conditions. To put that into perspective, PLA has among the lowest elongation at break measurements of the common 3D printing filaments.&nbsp;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733489740277-3d_printed_objects_on_table.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="PLA 3D prints in different colors">PLA is the most commonly used 3D printing filament, though it is not known for its flexibility.What is elongation at break? Elongation at break is a material property that refers to the ability of a material to stretch or elongate before it breaks or fractures. It is typically expressed as a percentage of the material's original length and is a measure of ductility or plasticity. In a standard tensile test, a sample of the material is pulled in tension until it breaks. The elongation at break is calculated by measuring the change in length of the sample and dividing it by the original length, then multiplying by 100.Of course, the specific elongation at break measurement varies depending on the brand of filament used, print settings such as infill and print speed, and geometry of the 3D print.[2] Generally speaking, however, this is how the most common 3D printing filaments compare when it comes to flexibility:<div dir="ltr" align="left"><table><tbody><tr><td>3D Printing Filament</td><td>Elongation at Break (%)</td></tr><tr><td>PLA</td><td>1-6%</td></tr><tr><td>ABS</td><td>20%</td></tr><tr><td>PETG</td><td>15-30%</td></tr><tr><td>TPU</td><td>300–700%</td></tr></tbody></table></div>Another key property of <a href="https://www.wevolver.com/article/pla-bed-temperature" target="_blank">PLA is its low melting point</a> and glass transition temperature. This means that the material is easy to process on a desktop FDM 3D printer, since it does not necessarily require a heated print bed or high nozzle temperatures (PLA prints best between 200-220 °C). However, the polymer’s low glass transition temperature of 60 °C also means that printed PLA components cannot be used in applications that require heat resistance.&nbsp;Recommended reading:<a href="https://www.wevolver.com/article/is-pla-food-safe" target="_blank">&nbsp;Food-grade 3D printing: Is PLA Food-Safe?</a><h2 dir="ltr">PLA+, Flexible PLA, and Soft PLA</h2>As we’ve seen, neat PLA is not known for its flexibility, however there are some PLA 3D printing products that have been engineered for increased flexibility through the use of special additives. For example, PLA+ (or PLA Plus) is an enhanced version of PLA that integrates plasticizers and toughening agents for better impact resistance and some degree of flexibility. Generally, PLA+ is not highly flexible, but it is somewhat more flexible than standard PLA. It is also designed to be tougher, more impact-resistant, and less prone to breaking under stress. For applications where true flexibility is required, however, PLA+ is still limited. For example, eSun’s PLA+ 3D printing material has an elongation at break of 20%, comparable to ABS.Flexible PLA is a variation of PLA mixed with flexible materials, such as thermoplastic elastomers (TPE) or thermoplastic polyurethane (TPU). It retains the ease of use associated with PLA, offering low printing temperatures and reduced warping. Flexible PLA filament can stretch and return to its original shape, making it suitable for gaskets, wristbands, and protective covers or phone cases. While it’s easier to print than highly flexible filaments like TPU or TPE, it is still more rigid than those materials.Soft PLA is another type of filament that typically combines PLA with other additives to improve elasticity and bendability, making it ideal for items like soft toys, flexible parts, or protective covers. However, "soft" in this context doesn't mean highly flexible—the material is still relatively rigid compared to true flexible filaments. It’s worth noting that while Soft PLA is more flexible than neat PLA, the material does not have the same elasticity as elastomers such as TPU.Recommended reading: <a href="https://www.wevolver.com/article/tpu-vs-pla" target="_blank">TPU vs PLA: Choosing Between Flexible and Rigid Filament for 3D Printing</a><h2 dir="ltr">Flexible alternatives to PLA filament</h2>For applications that require a high degree of elasticity, such as footwear, orthopedic models, tubes, seals, and more, there are elastomer filaments like TPU and TPE to consider.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733489800010-3d_printer_creating_object+%281%29.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="3D printing footwear flexible filament">Flexible filaments are useful for 3D printing wearables, such as footwear.<h3 dir="ltr">TPU and TPE Filaments</h3>TPU (thermoplastic polyurethane) is a highly flexible, rubber-like 3D printing filament known for its elasticity, strength, and abrasion resistance. It is a type of thermoplastic elastomer (TPE), meaning it combines the flexibility of rubber with the processing ease of a polymer. TPU can stretch significantly and return to its original shape, making it ideal for parts that require high durability, impact resistance, and flexibility.Key Features of TPU:<ul><li dir="ltr">Flexibility &amp; Elasticity: TPU can stretch in the range of 600% of its original length without breaking, making it perfect for flexible and elastic parts like phone cases, shoe soles, gaskets, and bumpers.</li><li dir="ltr">Durability: TPU is highly abrasion-resistant, tear-resistant, and impact-resistant, which gives it a long lifespan even in harsh conditions.</li><li dir="ltr">Chemical Resistance: It also has good resistance to oils, greases, and various chemicals.</li></ul>Recommended reading: <a href="https://www.wevolver.com/article/what-is-tpu-material-in-3d-printing-material-properties-applications-and-technologies" target="_blank">What is TPU Material in 3D printing: material properties, applications, and technologies</a>TPE (thermoplastic elastomer) is a flexible 3D printing filament that combines the elasticity and rubber-like properties of traditional elastomers with the processability of thermoplastics. Like TPU (a similar material), TPE is designed to provide high flexibility, stretchability, and reliability in applications requiring soft, bendable parts.Key Features of TPE:<ul><li dir="ltr">Flexibility and Softness: TPE can stretch significantly, offering rubber-like elasticity. It is commonly used to print parts like soft toys, wearables, gaskets, flexible hinges, and grips.</li><li dir="ltr">Durability: TPE is abrasion-resistant, impact-resistant, and has excellent fatigue resistance, making it suitable for items that endure frequent bending or compression.</li><li dir="ltr">Chemical Resistance: TPE is resistant to oils, greases, and various chemicals, offering good durability in environments where such substances are present.</li></ul>The main drawbacks of using elastic 3D printing filaments is that they are a) more expensive than PLA spools and b) they are more challenging to 3D print. Specifically, TPU and TPE’s elasticity can cause issues like <a href="https://www.wevolver.com/article/3d-printer-stringing" target="_blank">stringing</a>, <a href="https://www.wevolver.com/article/how-to-clean-3d-printer-nozzle" target="_blank">clogs, or jamming</a>, especially with Bowden extruders, which struggle to push flexible filament through the tube. Direct-drive extruders are therefore recommended for smoother printing. Flexible filaments also require slower print speeds (typically 20-30 mm/s) and lower <a href="https://www.wevolver.com/article/cura-retraction-settings" target="_blank">retraction settings</a> to avoid extrusion problems. Additionally, TPU and TPE print at higher temperatures compared to PLA. TPE and TPU also come with more limited post-processing options that more rigid filaments.Ultimately, while PLA is user-friendly and forgiving, TPU demands more careful settings and attention during printing for optimal results. Below are some 3D printing tips for flexible filaments:3D Printing with TPU:<ul><li dir="ltr">Print Settings: TPU requires slower print speeds (typically around 20-30 mm/s) to prevent issues like stringing or clogging. It also requires lower retraction settings due to its flexibility.</li><li dir="ltr">Print Temperature: TPU filament prints best at 224–250 °C.</li><li dir="ltr">Extruder Compatibility: Direct-drive extruders are generally recommended for TPU, as Bowden setups may struggle with the filament’s flexibility.[1]</li></ul><h3 dir="ltr"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733489815675-man_using_3d_printer.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="Man troubleshooting 3D printer">TPE and TPU can be tricky to 3D print and makers should be aware of problems like stringing and nozzle clogs.</h3><h3 dir="ltr">Polypropylene (PP)</h3>Polypropylene (PP) filament is flexible, but it has a distinct set of characteristics compared to other flexible filaments like TPU or TPE. Polypropylene is a lightweight, durable, and flexible thermoplastic known for its high impact resistance, chemical resistance, and fatigue resistance. It can bend and stretch without cracking, making it ideal for applications like hinges, living hinges, containers, and flexible parts that need to withstand repeated stress.In tests, PP filament has demonstrated an elongation at break in the range of &gt;800% and an elongation at yield in the range of 35%.[3] It also tends to be more challenging to print due to its low surface adhesion and tendency to warp. PP generally requires a heated bed (around 100-110°C) and sometimes a heated chamber for optimal results.&nbsp;<h2 dir="ltr">Conclusion</h2>In the end, while PLA is a popular and easy-to-use filament, it is not particularly flexible and can become brittle under stress. For applications requiring flexibility, alternatives like PLA+, Flexible PLA, and Soft PLA offer some improved flexibility, though they are still not as elastic as elastomeric materials. TPU and TPE are a suitable option for applications that require flexibility, such as phone cases, gaskets, or wearables. However, they come with their own set of challenges, including difficult printing conditions, higher temperatures, and more intricate print settings. Materials like Polypropylene (PP) offer flexibility with high impact and chemical resistance but can also be tricky to print. Ultimately, the choice of filament depends on the specific requirements of the project, including flexibility, durability, and ease of printing. For maximum flexibility and durability, TPU and TPE are recommended, but users should be prepared for a steeper learning curve compared to PLA.<h2 dir="ltr">Frequently Asked Questions (FAQs)</h2><h4 dir="ltr">Q: Is PLA flexible?</h4>A: No, PLA is a rigid filament and is not known for its flexibility. It is brittle and can break under stress with little deformation. It has a low elongation at break (1-6%), meaning it doesn’t stretch much before snapping.<h4 dir="ltr">Q: What is PLA+ and how flexible is it?</h4>A: PLA+ (or PLA Plus) is an enhanced version of PLA that incorporates toughening agents and plasticizers for better impact resistance and some flexibility. PLA+ has an elongation at break of around 20%, making it tougher and more resilient than standard PLA but still not highly flexible.<h4 dir="ltr">Q: What is Flexible PLA?</h4>A: Flexible PLA is a blend of PLA mixed with elastomers like TPU or TPE, making it more flexible than regular PLA. It is suitable for items like gaskets and phone cases. However, it is still more rigid than true flexible filaments and lacks the stretchability of materials like TPU or TPE.Q: What are the challenges of 3D printing with TPU and TPE?A: TPU and TPE filaments are more challenging to print compared to PLA due to their flexibility, which can cause issues like stringing, clogs, and jamming, especially with Bowden extruders. These filaments require slower print speeds (around 20-30 mm/s) and lower retraction settings to avoid extrusion problems. Additionally, TPU and TPE require higher print temperatures and are less forgiving during the post-processing stage compared to rigid filaments like PLA.<h2 dir="ltr">References</h2>[1] Flexible Materials Guide [Internet]. Simplify3D, 2024. Available from: <a href="https://www.simplify3d.com/resources/materials-guide/flexible/" target="_blank">https://www.simplify3d.com/resources/materials-guide/flexible/</a>&nbsp;[2] Leite M, Fernandes J, Deus AM, Reis L, Vaz MF. Study of the influence of 3D printing parameters on the mechanical properties of PLA.[3] Ultimaker PP Technical data sheet [Internet]. UltiMaker, April 20, 2022. Available from: <a href="https://um-support-files.ultimaker.com/materials/2.85mm/tds/PP/Ultimaker-PP-TDS-v3.00.pdf" target="_blank" data-lf-fd-inspected-kn9eq4roawkarlvp="true">https://um-support-files.ultimaker.com/materials/2.85mm/tds/PP/Ultimaker-PP-TDS-v3.00.pdf</a>&nbsp;

The most commonly used 3D printing filament, PLA is not known for its flexibility. We explore why that is and list some alternative 3D printing materials can be used when flexibility is needed.

Flexible 3D printer filaments: is PLA flexible?

Thermoplastic Polyurethane (TPU) has become a favorite material for hobbyists and professionals in FDM/FFF 3D printing due to its unique combination of flexibility, durability, and versatility. However, successfully 3D printing with TPU requires a thorough understanding of its thermal properties, including the average TPU glass transition temperature, extrusion temperature, and bed temperature settings. In this article, we’ll explore these factors in-depth, providing the knowledge you need to get the best results with TPU filament.<h2 dir="ltr">What is TPU Filament?</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733862510698-3d_printer_extruder_closeup.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="tpu">TPU filament is the most common flexible material for FDM 3D printingTPU, or Thermoplastic Polyurethane, is a versatile elastomer that bridges the gap between flexible rubber and rigid plastics. Known for its flexibility, durability, and abrasion resistance, TPU has become a cornerstone material in 3D printing for applications that require both elasticity and strength. This is partly because other elastomeric materials — rubber and silicone, for example — are not suited to the 3D printing process.[1]This thermoplastic material is categorized under flexible filaments, alongside TPE (Thermoplastic Elastomer) and TPA (Thermoplastic Polyamide). TPU stands out due to its balance of mechanical properties, offering a level of rigidity and ease of printing that TPE often lacks. It is highly resistant to wear, chemicals, and environmental factors like UV exposure, making it a reliable choice for both consumer and industrial applications.<h3 dir="ltr">TPU Brands and Availability</h3>Many reputable filament manufacturers produce TPU, each offering unique formulations tailored for different applications. For example:<ul><li dir="ltr">NinjaFlex: Known for its superior flexibility and resilience, ideal for wearables and gaskets.</li><li dir="ltr">SainSmart TPU: Offers a balance of affordability and quality, suitable for hobbyists and professionals alike.</li><li dir="ltr">Fillamentum Flexfill: Renowned for its consistent diameter and color options, making it a favorite for detailed prints.</li></ul><h3 dir="ltr">Beyond Filaments: TPU in Powder Form</h3><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733862520789-industrial_3d_printer.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="pls">SLS is another 3D printing technology that can be used for TPU partsTPU isn’t limited to filament-based printing. It is also available in pellets for injection molding and as a powder for use in Selective Laser Sintering (SLS) printers and other professional additive manufacturing systems.[2] SLS TPU powders enable high-precision, flexible parts with consistent mechanical properties throughout. This makes them ideal for industrial applications, such as producing prototypes, seals, and complex geometries that are difficult to achieve with filament-based methods.As the market for TPU expands, newer formulations continue to emerge, offering enhanced features like improved heat resistance, conductivity, or biodegradability, further broadening the scope of what TPU can achieve in 3D printing.Recommended reading: <a href="https://www.wevolver.com/article/tpu-vs-pla" target="_blank">TPU vs PLA: Choosing Between Flexible and Rigid Filament for 3D Printing</a><h2 dir="ltr">Advantages of TPU and Other Flexible Filaments</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733862529656-red_rubber_rings.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="seals">Seals and gaskets are parts that can be made from TPUTPU and other flexible materials provide important advantages in 3D printing. Some are obvious, while some are less well known to beginners.<h3 dir="ltr">Flexibility and Elasticity &nbsp;</h3>One of TPU’s standout features is its exceptional flexibility, elasticity, and elongation. It can stretch significantly under tension and return to its original shape without permanent deformation, making it perfect for dynamic or load-bearing applications like hinges, gaskets, and flexible connectors. This property also makes TPU ideal for wearable devices and soft robotics, where adaptability and resilience are essential.<h3 dir="ltr">Durability &nbsp;</h3>TPU is highly durable, offering excellent resistance to wear, tear, and impact. Unlike rigid plastics that may crack or break under stress, TPU absorbs energy and rebounds, significantly enhancing the lifespan of printed parts. This high impact strength is why TPU is often used in protective cases, shoe soles, and automotive components that endure heavy use.<h3 dir="ltr">Chemical Resistance &nbsp;</h3>Another significant advantage of TPU is its resistance to oils, greases, and various solvents.[3] This chemical resistance makes TPU suitable for industrial applications where exposure to harsh substances is common, such as seals, gaskets, and fluid-handling components.<h3 dir="ltr">Versatility &nbsp;</h3>TPU is available in various shore hardness levels, allowing users to choose between soft, highly elastic formulations and stiffer, more rigid variants. (Fillamentum, for example, offers TPU with a shore A of 92 or 98.) This versatility makes TPU adaptable to a wide range of projects, from flexible prototypes to robust end-use parts.<h3 dir="ltr">Shock Absorption &nbsp;</h3>Thanks to its elastomeric properties, TPU excels at absorbing and dissipating energy. This characteristic makes it an excellent material for vibration dampers, shock absorbers, and protective padding. Products like smartphone cases or sports equipment often utilize TPU for this reason, ensuring protection against impacts.<h3 dir="ltr">Weather Resistance &nbsp;</h3>TPU can withstand prolonged exposure to environmental elements like UV rays and moisture without significant degradation. This property makes it a reliable choice for outdoor applications, such as weatherproof enclosures, seals, and grips.<h3 dir="ltr">Printing Adaptability &nbsp;</h3>While flexible filaments can be challenging to print, TPU is among the most user-friendly options in this category. Compared to TPE, TPU offers improved rigidity, which minimizes common printing issues like filament buckling or clogging. This makes it more accessible to users with less advanced 3D printer setups.<h3 dir="ltr">Soft Touch and Comfort &nbsp;</h3>The tactile qualities of TPU are another advantage. Its soft-touch surface and rubber-like feel make it comfortable to handle, which is why it’s commonly used in grips, ergonomic tools, and wearable technology.<h3 dir="ltr">Cost-Effective Prototyping &nbsp;</h3>For industries requiring flexible and durable prototypes, TPU offers a cost-effective solution. Its ease of processing and broad compatibility with FDM printers reduce production times and costs compared to traditional manufacturing methods for elastomeric parts.With its extensive list of advantages, TPU stands as one of the most versatile and practical materials for 3D printing, enabling a diverse range of functional and aesthetic applications.Recommended reading: <a href="https://www.wevolver.com/article/strongest-3d-printer-filament" target="_blank">Strongest 3D Printer Filament: Choosing Between PC, Nylon, TPU, and Others</a><h2 dir="ltr">Thermal Properties of TPU</h2><img src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNzMzMTc0NTAwMDMwLTYxcFJxVUI2ZEFMLl9TTDEwMDBfLmpwZyIsImVkaXRzIjp7InJlc2l6ZSI6eyJ3aWR0aCI6OTUwLCJmaXQiOiJjb3ZlciJ9fX0=" style="width: 100%px;" class="fr-fic fr-dib" alt="ninjaflex">Popular TPU filament Ninjaflex has a recommended printing temperature of 225–250°C (credit: NinjaTek)Understanding TPU's thermal properties is essential for successful 3D printing. These properties influence how the filament behaves during heating, extrusion, and cooling.<h3 dir="ltr">TPU Glass Transition Temperature (Tg)</h3>The glass transition temperature (Tg) of TPU is low, typically around -30°C depending on its formulation. This low Tg is a defining characteristic of TPU’s flexibility and resilience at room temperature. But why is TPU’s Tg so low compared to other thermoplastics like <a href="https://www.wevolver.com/article/pla-vs-abs" target="_blank">PLA or ABS</a>?The answer lies in its chemical structure. TPU consists of alternating soft and hard segments. The soft segments are made of polyether or polyester chains, which are highly flexible and contribute to the material’s elasticity. These segments have low intermolecular forces, allowing the polymer chains to move freely even at low temperatures. As a result, TPU remains soft and pliable well below freezing, making it ideal for applications in cold environments.In contrast, the hard segments provide strength and thermal stability but are dispersed throughout the material in such a way that they do not significantly elevate the Tg. This structural balance between flexibility and durability is what sets TPU apart from rigid thermoplastics.<h3 dir="ltr">TPU Melting Point&nbsp;</h3>TPU does not have a sharp melting temperature but softens over a temperature range, typically 200°C to 250°C.<h3 dir="ltr">TPU Heat Resistance</h3>Although TPU remains flexible at low temperatures, its heat resistance is limited, with most formulations softening significantly above 60–80°C. This makes TPU unsuitable for high-temperature applications without modification. Some TPU filaments have higher heat resistance. For example, Formfutura's Python Flex 98A material is heat-resistant up to 138°C.<h2 dir="ltr">TPU Print Temperature Settings</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733862555601-3d_printer_extruder.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="nozzle">The nozzle temperature for TPU tends to be in the range of 200–240°CPrinting TPU requires precise control of several temperature settings and other printing parameters, including the nozzle temperature, bed temperature, and potentially the use of a heated chamber.<h3 dir="ltr">Nozzle Temperature</h3>The recommended extrusion temperature for TPU generally ranges from 200°C to 240°C, depending on the brand and formulation. Some popular brands and their temperature ranges include:<ul><li dir="ltr">NinjaFlex: 225–250°C</li><li dir="ltr">SainSmart TPU: 200–220°C</li><li dir="ltr">Fillamentum Flexfill: 220–240°C</li></ul>Choosing the correct nozzle temperature is essential to ensure proper layer adhesion, minimize defects, and maintain the mechanical properties of the printed part. Printing TPU at a temperature that is too low can lead to under-extrusion, resulting in weak parts and poor surface quality. Insufficient heat prevents the material from flowing smoothly, causing inconsistent extrusion and gaps between layers. On the other hand, excessively high temperatures can cause stringing, oozing, or even thermal degradation of the 3D printing filament, leading to brittle prints or discoloration. &nbsp;To optimize nozzle temperature, it's advisable to start in the mid-range of the manufacturer’s recommendation and adjust incrementally in 5° steps. Observing the filament flow during a test print can help identify the ideal setting for your printer and filament combination.Due to its flexibility, TPU is prone to kinking or compressing inside the extruder, which can lead to clogs. To avoid this issue, ensure that the filament path is constrained and that your extruder gears are not overly tightened. Using a direct drive extruder can help by minimizing the distance TPU travels between the drive gear and the nozzle. Additionally, keeping the nozzle clean and free of residue is crucial. Periodic maintenance and using higher-quality TPU filaments with consistent diameter tolerances can significantly reduce the risk of clogs.Proper nozzle temperature and care are key to unlocking TPU’s full potential, enabling smooth extrusion and reliable results across a wide range of applications.<h3 dir="ltr">Bed Temperature</h3>A heated bed can play an important role in achieving successful prints with TPU. A heated bed can enhance first-layer adhesion and minimize issues like warping or lifting, which can compromise print quality. For most TPU filaments, a bed temperature in the range of 40–60°C is recommended, though the exact setting depends on the filament brand and the specific printer setup. &nbsp;When printing with TPU, adhesion to the build plate is essential due to its tendency to contract slightly as it cools. A heated bed provides a stable thermal environment, keeping the base layers adhered to the surface during the printing process. For best results, pairing a heated bed with an adhesive surface like PEI, a glue stick, or specialized printing sheets designed for flexible filaments can further improve reliability. &nbsp;Maintaining a consistent bed temperature is especially critical for larger prints or parts with wide, flat bases, as these are more prone to warping. If your printer struggles with adhesion despite proper heating, adjusting the first-layer height and speed, combined with careful leveling of the build plate, can make a significant difference. &nbsp;While TPU is more forgiving than some rigid filaments like ABS when it comes to warping, neglecting the heated bed can lead to uneven layers or poor surface quality, especially for prints requiring high precision.<h3 dir="ltr">Enclosure</h3>Unlike materials like ABS, TPU does not require a closed chamber for printing. However, maintaining a consistent ambient temperature can improve results, particularly for large or intricate prints. If warping occurs, a partially enclosed printer or chamber may help.<h2 dir="ltr">Conclusion</h2>Printing with TPU can be challenging, but understanding its thermal properties and fine-tuning your printer settings can lead to excellent results. Besides, there's virtually no flexible and reliable alternative at its price point for extrusion-style 3D printing. From its low glass transition temperature to its wide extrusion range, TPU offers unmatched flexibility and durability for various applications. By mastering its print temperatures and bed settings, you can unlock the full potential of this versatile filament.<h2 dir="ltr">Frequently Asked Questions</h2>What is the ideal nozzle temperature for TPU?Most TPU filaments print well between 200–240°C, depending on the brand and formulation. Always refer to the manufacturer’s recommendations.Do I need a heated bed to print TPU?While not always mandatory, a heated bed up to about 60°C can improve adhesion and reduce warping, especially for large prints.Can TPU be printed on a Bowden extruder?Yes, but it’s more challenging due to TPU's flexibility. A direct drive extruder is generally recommended for better control.Does TPU require a closed chamber?No, TPU does not require a closed chamber, but consistent ambient temperatures can improve print quality for large or detailed prints.How does TPU compare to TPE?TPU is generally easier to print and offers greater durability, while TPE is softer and more flexible. TPU is a better choice for wear-resistant applications.<h2 dir="ltr">References</h2>[1] Miron VM, Lämmermann S, Çakmak U, Major Z. <a href="https://www.sciencedirect.com/science/article/pii/S2452321621002511" target="_blank">Material characterization of 3d-printed silicone elastomers</a>. Procedia Structural Integrity. 2021 Jan 1;34:65-70.[2] Yuan S, Shen F, Bai J, Chua CK, Wei J, Zhou K. <a href="https://www.sciencedirect.com/science/article/abs/pii/S0264127517301272" target="_blank">3D soft auxetic lattice structures fabricated by selective laser sintering: TPU powder evaluation and process optimization</a>. Materials &amp; Design. 2017 Apr 15;120:317-27.[3] Backes EH, Harb SV, Pinto LA, de Moura NK, de Melo Morgado GF, Marini J, Passador FR, Pessan LA. <a href="https://link.springer.com/article/10.1007/s10853-023-09077-z" target="_blank">Thermoplastic polyurethanes: synthesis, fabrication techniques, blends, composites, and applications</a>. Journal of Materials Science. 2024 Jan;59(4):1123-52.

This article explores the thermal properties of TPU, including TPU glass transition temperature, extrusion and bed temperatures, and best practices for successful 3D printing.

TPU Glass Transition Temperature, Printing Temperature, and Other Thermal Considerations

Able to store carbon to offset emissions and prevent soil degradation and pollution, charcoal-like <a href="https://www.climatehubs.usda.gov/hubs/northwest/topic/biochar">biochar</a> could offer a sustainable solution to a lot of environmental challenges — if its production can be made greener. Supported by a three-year, $799,883 grant from the U.S. Department of Agriculture (USDA) National Institute of Food and Agriculture, an international team led by researchers at Penn State will address the so-called “dark side” of biochar, assessing the threat of organic contaminant residues in biorefinery char products.Biochar comprises organic waste material and is made by&nbsp;pyrolysis, a process that involves heating the organic material in a limited oxygen environment. While biochar has significant potential for use as a soil amendment and for carbon sequestration, its manufacturing process can produce harmful compounds if it is not designed and executed properly.“While the title of our research project — ‘The Dark Side of Biochar: Addressing the Threat of Organic Contaminant Residues in Biorefinery Char Products’&nbsp;— may sound ominous, our main goal is to help make sure that problems don’t crop up in the making of biochar,” said team leader <a href="https://abe.psu.edu/directory/dec109">Daniel Ciolkosz</a>, associate research professor of agricultural and biological engineering in the <a href="https://agsci.psu.edu/">Penn State College of Agricultural Sciences</a>. “That way, we can help ensure that biochar lives up to its potential as a positive and beneficial bio-based product.”&nbsp;The goal of the research is to identify and test design and optimization strategies for biorefineries to produce biochar without the presence of dangerous organic compounds such as such as benzene, hexane and toluene, Ciolkosz explained. As part of their work, the researchers are assessing how these contaminants are created and disposited in biochar, as well as evaluating treatment processes to remove them.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1732755846164-biochar-in-hand-low-rez.jpg" style="width: 100%px;" class="fr-fic fr-dib">The goal of the project is to help ensure that biochar lives up to its potential as a positive and beneficial bio-based product, the researchers said. Credit: Penn State. Creative Commons“If process conditions aren’t right and these toxic compounds are produced, workers could be exposed to harmful conditions and the biochar could end up being a source of contamination, reducing its applicability and acceptability for widespread use,” he said. “This project will characterize the emission of harmful organic compounds from biomass during conversion to biochar in a biorefinery, and its redeposition on the biochar.”In the study, researchers will use biomass feedstocks, such as crop and forestry residues, algae and municipal organic waste, from various sources in experiments designed to assess emissions and contaminant levels resulting from biochar manufacture. They also will evaluate engineered treatment processes for contaminant removal and utilization. Based on their findings, they’ll analyze the overall performance of biorefineries and develop strategies for design and optimization of biorefineries that include biochar in their product mix.Other members of the research team include Juliana Vasco-Correa, Penn State assistant professor of agricultural and biological engineering; Andrzej Białowiec, Wrocław University of Environmental and Live Sciences, Poland; David DeVallance, Commonwealth University of Pennsylvania; and Thomas Causer, Advanced Torrefaction Systems.

An international team led by Penn State researchers aims to mitigate toxic organic compounds produced in manufacturing of the biomaterial known as biochar

Researchers to study how to make carbon-storing product safer, more sustainable

Plastic injection molding is the most common production process for simple plastic parts with thin walls. It is fast, cheap, and ideal for mass production. However, an injection molding machine is a complex piece of equipment, and the process is prone to a few specific problems that can lead to part defects.Injection molding defects can significantly impact the quality and performance of manufactured products — or render them completely unusable and destined for the scrapheap. This can in turn lead to increased production costs, reduced efficiency, and compromised product reliability. For manufacturers, addressing these issues is key to maintaining quality standards and ensuring customer satisfaction.Understanding plastic injection molding defects involves identifying their causes, diagnosing their presence, and implementing preventive measures. This article looks at some of the most common injection molding defects, examining why they occur and how to prevent them.<h2 dir="ltr">What Are Injection Molding Defects?</h2><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733143119052-yellow_black_plastic_parts.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="parts">Because they are made quickly and affordably, molded parts can exhibit defectsInjection molding defects are imperfections or anomalies that occur during the manufacturing process of molded products. These defects can manifest in various forms, such as surface blemishes, structural inconsistencies, or dimensional inaccuracies. They can undermine the functionality, aesthetics, and durability of the finished products, often leading to increased waste and production costs.[1]Proactively identifying and mitigating defects can save resources, reduce operational costs, and lead to high-quality parts. By prioritizing defect management, manufacturers can enhance their competitiveness and foster sustainable production practices.<h2 dir="ltr">Common Types of Injection Molding Defects</h2>Injection molding is a highly efficient manufacturing process, but it is not without its challenges. Defects can arise at various stages of production, affecting the functionality, aesthetics, and overall quality of the final product. Below are some of the most frequent defects encountered in injection molding, along with their causes and implications:<h3 dir="ltr">Sink Marks</h3>These are shallow depressions or dimples that form on the surface of molded parts, often around thicker sections of material. Sink marks occur when the material inside the part cools and shrinks unevenly, pulling the surface inward. They are commonly caused by insufficient packing pressure, inadequate cooling time, or poor mold design features such as inconsistent ribs.[2]<h3 dir="ltr">Warping</h3>Warping is the unwanted bending or twisting of molded parts after ejection from the mold. It is primarily caused by uneven cooling rates across the part, leading to residual stresses that distort the shape. Warping can also result from improper material selection, as some polymers are more prone to shrinkage and deformation than others.<h3 dir="ltr">Short Shots</h3>A short shot happens when the molten material does not completely fill the mold cavity, resulting in incomplete or missing sections of the part. This defect is often caused by inadequate injection pressure or obstructions within the mold. It can also occur if the mold is poorly vented, preventing the material from flowing freely.<h3 dir="ltr">Flash</h3>Flash is an excess layer of material that seeps out of the mold cavity along the mold parting line or around ejector pins. This defect can occur if the mold is not clamped tightly enough or if the clamping force is uneven. Flash can also result from excessive injection pressure or worn mold components that allow material to escape.<h3 dir="ltr">Burn Marks</h3>Burn marks are darkened or charred areas on the surface of molded parts, typically caused by trapped air overheating during the injection process. These marks are usually found near sharp corners, flow path ends, or areas where air cannot escape the mold cavity. Factors contributing to burn marks include high injection speeds, insufficient venting, or improper gate design.<h3 dir="ltr">Flow Lines</h3>Flow lines are visible streaks or patterns on a molded part’s surface, caused by the cooling and solidification of material as it flows through the mold. These defects are often linked to inconsistent injection speeds, material temperature, or poor mold design. Although flow lines are typically cosmetic, they can indicate potential weaknesses in the part.<h3 dir="ltr">Delamination</h3>Delamination refers to the peeling or separation of surface layers on a molded part, resulting in a flaky or brittle texture. This defect is sometimes caused by contamination of the material, such as moisture or foreign particles. It can also occur if incompatible materials or additives are used together or if the material experiences excessive shear stress during molding.<h3 dir="ltr">Jetting</h3>Jetting appears as wavy, worm-like lines on the surface of molded parts, caused by irregular material flow of the molten plastic. This defect occurs when molten material is injected too quickly or at an improper angle, leading to turbulence rather than smooth filling. Jetting can also result from incorrect gate design or insufficient mold temperature. Proper flow rate and gate positioning can help mitigate this issue.<h3 dir="ltr">Voids</h3>Voids are small cavities or air pockets that form inside molded parts, often reducing their structural integrity. They typically occur due to uneven cooling, excessive material shrinkage, or trapped air during the molding process. Poorly designed runners or gates and insufficient holding pressure can exacerbate the issue. Adjusting cooling profiles and improving mold venting can help prevent voids.<h3 dir="ltr">Knit Lines</h3>Knit lines, also known as weld lines, are visible seams where two flow fronts of molten material meet but fail to fully fuse. This defect is often caused by insufficient material temperature or pressure, long flow paths, or improper gate placement. While sometimes purely cosmetic, knit lines can compromise strength. Enhancing material flow and optimizing mold design can reduce their occurrence.Recommended reading: <a href="https://www.wevolver.com/article/the-pros-and-cons-of-3d-printing-low-run-injection-molds" target="_blank">The pros and cons of 3D printing low-run injection molds</a><h2 dir="ltr">Root Causes of Injection Molding Defects</h2><h3 dir="ltr">Material-Related Causes</h3><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1733143131103-colorful_plastic_pellets.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="injection molding materials">Some injection molding materials are more defect-prone than othersThe type and quality of plastic materials used in injection molding play a role in determining the success of the process. Factors such as moisture content, contamination, and material compatibility can directly influence the occurrence of defects.<ul><li dir="ltr">Moisture Content: Excess moisture in raw molding materials can lead to defects like voids, bubbles, or delamination in the finished product. Certain plastics, such as polycarbonate and nylon, are hygroscopic and require proper drying before use to prevent moisture-related issues.</li><li dir="ltr">Contamination: Foreign particles or impurities in the material can cause surface blemishes, inconsistent textures, or reduced structural integrity. For instance, contamination with incompatible polymers or dust can result in brittle or uneven parts.</li><li dir="ltr">Material Selection: Some materials are simply more prone to certain defects than others. For example, polypropylene may exhibit sinking, fiber-filled plastics may warp, and moisture-filled nylon can sputter and create various defects.</li></ul><h3 dir="ltr">Process-Related Causes</h3>The parameters used during the injection molding process also greatly affect the quality and consistency of the final product. Variations in temperature, pressure, and injection speed can introduce defects if not carefully controlled.<ul><li dir="ltr">Temperature: Inconsistent or incorrect material temperatures can lead to issues such as burn marks, short shots, or material degradation. For instance, excessive melt temperature can cause thermal degradation, resulting in discoloration or reduced material strength.</li><li dir="ltr">Pressure: Insufficient or excessive injection pressure (back pressure and/or holding pressure) can lead to defects. Low pressure may cause short shots or incomplete filling of the mold cavity, while excessive pressure can lead to flash or damage to the mold.</li><li dir="ltr">Injection Speed: The speed at which material is injected into the mold impacts the flow and cooling dynamics. High injection speeds may trap air within the mold, causing burn marks, while low speeds can lead to flow lines or incomplete filling.</li></ul><h3 dir="ltr">Design-Related Causes</h3>Product and mold design are important factors in the success of the injection molding process. Poor design choices can lead to a variety of defects, impacting both the structural integrity and aesthetic quality of the molded part.<ul><li dir="ltr">Wall Thickness: Uneven or excessively thick walls can cause defects such as sink marks, warping, or voids. For example, parts with inconsistent wall thickness may cool unevenly, leading to residual stresses and dimensional inaccuracies.</li><li dir="ltr">Rib Design: Improper rib placement or dimensions can result in defects like sink marks or weld lines. Ribs that are too thick relative to the surrounding walls can create localized shrinkage, causing surface imperfections and weakened structural areas.</li><li dir="ltr">Gate Location: The placement of gates in the mold affects the flow of molten material. Poorly positioned gates can lead to defects such as flow lines, air traps, or incomplete filling. Researchers have argued that gate location is one of the most important considerations for minimizing wastage and energy costs and consequently increasing sustainability.[3]</li></ul>Recommended reading: <a href="https://www.wevolver.com/article/what-are-injection-mold-sprues-runners-and-gates" target="_blank">What are injection mold sprues, runners, and gates?</a><h2 dir="ltr">Identifying, Diagnosing, and Predicting Defects</h2><h3 dir="ltr"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1732650534151-mold-and-inserts-large-1920x1080-v2.jpg" style="width: 100%px;" class="fr-fic fr-dib" alt="moldflow">Flow simulation tools like Autodesk Moldflow can prevent defects (image credit:&nbsp;<a href="https://www.autodesk.com/ca-en/products/moldflow/" target="_blank" rel="noopener noreferrer">Autodesk</a>)Visual Inspection</h3>Visual inspection is a fundamental step in identifying defects in molded parts. By systematically examining parts after production, manufacturers can detect and address quality issues early.<ul><li dir="ltr">Examine Surface Quality: Look for visible imperfections such as sink marks, burn marks, or flash. These defects often indicate problems with material flow, temperature, or mold clamping.</li><li dir="ltr">Check for Dimensional Accuracy: Measure critical dimensions to detect warping, short shots, or shrinkage. Variances in size can compromise the fit and functionality of the part.</li><li dir="ltr">Inspect Weld and Flow Lines: Observe areas where material flows meet or change direction. Flow lines may appear as streaks or discolorations, while weld lines can signal weakened structural points.</li><li dir="ltr">Assess Overall Consistency: Compare parts from the same production run to identify variations. Inconsistent quality across parts can highlight issues with process parameters or mold design.</li></ul><h3 dir="ltr">Advanced Diagnostic Tools</h3>Advanced diagnostic tools play a crucial role in identifying and analyzing defects in injection molding processes (or predicting them in advance). These technologies provide deeper insights into the root causes of defects, enabling manufacturers to make informed adjustments and improve quality.<div dir="ltr" align="left"><table><tbody><tr><td>Tool</td><td>Description</td><td>Benefits</td><td>Limitations</td></tr><tr><td>Thermal Imaging</td><td>Detects temperature variations across the molded part and within the mold during the injection process. Identifies areas prone to uneven cooling (e.g., warping, sink marks).</td><td>Non-invasive&nbsp;Real-time analysis&nbsp;Easy identification of thermal inconsistencies</td><td>Limited detection of internal defects&nbsp;Cannot identify material-related issues</td></tr><tr><td>X-ray Inspection</td><td>Examines the internal structure of molded parts, detecting voids, inclusions, or incomplete filling not visible externally.</td><td>High precision&nbsp;Assesses material integrity</td><td>High cost&nbsp;Requires specialized equipment and expertise</td></tr><tr><td>Flow Simulation Software</td><td>Models the flow of molten material within the mold, predicting issues like air traps, weld lines, or improper filling. Optimizes mold design and process parameters.</td><td>Prevents defects proactively&nbsp;Reduces costly trial-and-error processes</td><td>Requires accurate input data&nbsp;Demands significant computational resources</td></tr></tbody></table></div><h1 dir="ltr">Material Quality Assurance Checklist</h1>Prevention of injection molding defects largely comes down to skilled part design and machine operation. However, choosing the right materials and ensuring their proper handling can also help to prevent injection molding defects. Material properties such as viscosity, thermal stability, and moisture absorption can significantly impact the quality of molded parts.Some best practices when obtaining and handling materials for injection molding include:<ul style="list-style-type: circle;"><li dir="ltr">Verify material certification and supplier quality standards.</li><li dir="ltr">Inspect raw materials for signs of contamination, discoloration, or damage.</li><li dir="ltr">Test moisture content before processing and ensure it meets the manufacturer’s specifications.</li><li dir="ltr">Conduct small-scale trial runs to confirm material performance under intended processing conditions. Adhering to these practices helps ensure material integrity and minimizes the likelihood of defects during injection molding.</li></ul><h1 dir="ltr">Conclusion</h1>Effectively managing injection molding defects requires an understanding of their causes and the proactive implementation of preventive measures. Manufacturers can enhance product quality by selecting the appropriate materials, optimizing injection molding processes, and designing molds thoughtfully. These efforts not only minimize production costs but also ensure the reliability and consistency of molded parts.Recommended reading: <a href="https://www.wevolver.com/article/3d-printing-vs-injection-molding" target="_blank">3D printing vs injection molding: process, materials, applications</a><h1 dir="ltr">Frequently Asked Questions (FAQs)</h1>Q: What are the most common injection molding defects?A: Common defects in injection molded parts include sink marks, warping, short shots, flash, burn marks, and flow lines. Each arises from different factors such as material properties, processing conditions, or mold design.Q: How does material selection impact defect prevention?A: Material properties such as moisture absorption, thermal stability, and viscosity significantly affect defect risks. Selecting materials suited to the application and process conditions is essential for defect prevention.Q: What role does process monitoring play in reducing defects?A: Process monitoring helps detect anomalies in real time, ensuring consistent quality. Tracking parameters such as temperature, pressure, and cooling rates allows for early adjustments to avoid defects.Q: Can flow simulation software help prevent defects?A: Yes, flow simulation software models the material's behavior within the mold, predicting potential issues like air traps, weld lines, or incomplete filling. This helps optimize mold design and processing parameters.&nbsp;Q: Why is mold design critical to defect prevention?A: Mold design determines how material flows, cools, and solidifies. Features like gate placement, wall thickness, and rib design directly impact defect risks and product quality.<h1 dir="ltr">References</h1>[1] Chen YM, Liu JJ. <a href="https://www.sciencedirect.com/science/article/pii/S0736584599000058" target="_blank">Cost-effective design for injection molding</a>. Robotics and computer-integrated manufacturing. 1999 Feb 1;15(1):1-21.[2] Gruber DP, Berger G, Pacher G, Friesenbichler W.<a href="https://www.sciencedirect.com/science/article/abs/pii/S0142941811000717" target="_blank">&nbsp;Novel approach to the measurement of the visual perceptibility of sink marks on injection molding parts</a>. Polymer testing. 2011 Sep 1;30(6):651-6.[2] Huszar M, Belblidia F, Davies HM, Arnold C, Bould D, Sienz .<a href="https://www.sciencedirect.com/science/article/pii/S2214993715000093" target="_blank">&nbsp;Sustainable injection moulding: The impact of materials selection and gate location on part warpage and injection pressure</a>. Sustainable Materials and Technologies. 2015 Sep 1;5:1-8.

Injection molding problems like sink marks and flash can be prevented by addressing their most common causes. This article serves as a basic troubleshooting guide.

Injection Molding Defects: Causes, Identification, and Prevention

Caltech researchers from campus and JPL have collaborated to devise a method for coating lithium-ion battery cathodes with graphene, extending the life and performance of these widely used rechargeable batteries.These efforts have led to a promising discovery that may improve lithium-ion battery performance and reduce reliance on cobalt, an element frequently used in lithium-ion batteries that is difficult to source sustainably.<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1732324120515-Boyd_David-Graphene-GEN-WEB.width-450+%281%29.jpg" style="width: 100%px;" class="fr-fic fr-dib">Graphene Encapsulated Nanoparticles (GEN). Nanoparticle silica (SiO2) is encapsulated with graphene using the Caltech low temperature process. The GEN is then dry-coated onto the cathode of a lithium-ion battery to improve performance. Credit: David BoydCaltech senior research scientist David Boyd has worked over the past decade to develop techniques for manufacturing graphene, a one-atom thick layer of carbon that is incredibly strong and conducts electricity more readily than materials such as silicon. In 2015, Boyd and colleagues discovered that <a href="https://www.caltech.edu/about/news/caltech-scientists-develop-cool-process-make-better-graphene-45961">high-quality graphene could be produced at room temperature</a>. Prior to this, the production of graphene required extremely high temperatures, up to 1,000 degrees Celsius.After this breakthrough, the hunt was on for new applications for graphene. Recently, Boyd teamed up with Will West, a technologist at JPL, which Caltech manages for NASA. West specializes in electrochemistry and, in particular, in the development of improved battery technologies. Boyd and West set out to see if graphene could create an improved lithium-ion battery. Now they have shown that it can."Demonstrating a reliable trend in battery-cell performance requires consistent materials, consistent cell assembly, and careful testing under a range of conditions," says Brent Fultz, Caltech's Barbara and Stanley R. Rawn, Jr., Professor of Materials Science and Applied Physics. "It is fortunate that the team was able to do this work so reproducibly, although it took some time to be sure."The lithium-ion battery, first introduced to the market in 1991, has revolutionized how we use electricity in our daily lives. From our cell phones to electric vehicles, we rely on lithium-ion batteries as a comparatively cheap, energy-efficient, and, most importantly, rechargeable energy source on the go.Despite its successes, there is room for improvement in lithium-ion battery technology. For example, Boyd says, "Tesla engineers want a cost-effective battery that can charge quickly and operate for a longer period of time between charges. That's called the charge-rate capability."West adds: "The more times you can charge a battery over its lifetime, the fewer batteries you have to use. This is important because lithium-ion batteries make use of limited resources and disposing of lithium-ion cells safely and effectively is a very challenging task."An important feature of lithium-ion batteries is how they perform after many cycles of charging and use. Batteries work by creating chemical energy between the two ends of the battery—the cathode and the anode—and converting it into electrical energy. As the chemicals in the cathode and those in the anode function over time, they may not fully recover to their original condition. A common problem is the dissolution of transition metals from the cathode material which is particularly severe in cathode materials with high manganese content, though less so for high cobalt content cathode materials."As a result of unwanted side-reactions that occur during cycling, transition metals in the cathode gradually end up in the anode where they get stuck and reduce the performance of the anode," Boyd explains. This transition metal dissolution (TMD) is a reason why expensive cobalt-bearing cathodes are used instead of inexpensive high manganese content cathodes.A further challenge for lithium-ion batteries is that they require metals that are expensive, scarce, and not always <a href="https://unctad.org/system/files/official-document/ditccom2019d5_en.pdf" data-lf-fd-inspected-kn9eq4roawkarlvp="true">mined responsibly</a>. A significant amount of the global supply of cobalt, in particular, is concentrated in the Democratic Republic of the Congo, and much of that cobalt is extracted by so-called <a href="https://www.npr.org/sections/goatsandsoda/2023/02/01/1152893248/red-cobalt-congo-drc-mining-siddharth-kara">artisanal miners</a>: freelance workers, including children, who engage in dangerous and demanding physical labor for little to no pay.The search has been on for ways to increase battery performance while also reducing or eliminating the use of cobalt and still preventing TMD.Enter graphene. Engineers previously knew that carbon coatings on a lithium-ion battery's cathode could slow or stop TMD, but developing a method to apply these coatings proved difficult. "Researchers have tried to deposit graphene directly onto the cathode material, but the process conditions typically needed to deposit graphene would destroy the cathode material," Boyd explains. "We investigated a new technique for depositing graphene on the cathode particles called dry coating. The idea is that you have one 'host' substance of large particles and a 'guest' substance of tiny particles. By mixing them under certain conditions, the system can undergo a phenomenon known as 'ordered mixing' in which the guest particles uniformly coat the host particles."Dry-coating technology has been in use since the 1970s in the pharmaceutical industry to extend the life of tablets by protecting them from moisture, light, and air.Boyd recalls thinking "This is a good idea we might be able to use with graphene! We can first manufacture graphene guest particles—graphene encapsulated nanoparticles (GEN)—using our room-temperature method, and then dry coat a very small amount of it (1 percent in weight) onto the host cathode material so that graphene effectively covers and protects the cathode."Dry coating the cathode with a graphene composite proved successful in the lab. The graphene coating sharply reduced TMD, simultaneously doubled battery cycle life, and allowed the batteries to function across a somewhat wider temperature range than previously possible. This result surprised researchers. It was assumed that only a continuous coating could suppress TMD and that a dry coating composed of particles could not. In addition, because graphene is a form of carbon, it is widely available and environmentally friendly.This method has additional benefits for the battery industry. "Battery factories are very expensive. A lot of money has been invested into them," Boyd says. "So it's very important that improved battery technologies are scalable and can fit into the workflows of existing battery manufacturing. We can take almost any cathode material and add in just a small amount of our GEN, run it for a few minutes in the dry mixer, and it will reduce transition metal dissolution and improve charge-rate capacity.""This is also an advance for coating technologies in general," Boyd says. "It opens up a lot of possibilities for the use of dry coatings."The paper detailing this research is titled "Suppression of Transition Metal Dissolution in Mn-Rich Layered Oxide Cathodes with Graphene Nanocomposite Dry Coatings" and was published on November 1, 2024, in the Journal of The Electrochemical Society. Co-authors include Boyd; Fultz; Cullen M. Quine (PhD '23); Caltech staff research scientist Channing Ahn; and West and Jasmina Pasalic at JPL. Research was supported by gifts from Lewis and Diane van Amerongen and Charles Fairchild. Equipment was provided by Graph Energy Inc. Experiments carried out at JPL were supported by NASA.

Caltech researchers from campus and JPL have collaborated to devise a method for coating lithium-ion battery cathodes with graphene, extending the life and performance of these widely used rechargeable batteries.

Graphene Builds a Better Battery

As the world struggles to reduce greenhouse gas emissions, researchers are seeking practical, economical ways to capture carbon dioxide and convert it into useful products, such as transportation fuels, chemical feedstocks, or even building materials. But so far, such attempts have struggled to reach economic viability.New research by engineers at MIT could lead to rapid improvements in a variety of electrochemical systems that are under development to convert carbon dioxide into a valuable commodity. The team developed a new design for the electrodes used in these systems, which increases the efficiency of the conversion process.The findings are reported today in the journal&nbsp;Nature Communications, in a paper by MIT doctoral student Simon Rufer, professor of mechanical engineering Kripa Varanasi, and three others.“The CO2 problem is a big challenge for our times, and we are using all kinds of levers to solve and address this problem,” Varanasi says. It will be essential to find practical ways of removing the gas, he says, either from sources such as power plant emissions, or straight out of the air or the oceans. But then, once the CO2 has been removed, it has to go somewhere.A wide variety of systems have been developed for converting that captured gas into a useful chemical product, Varanasi says. “It’s not that we can’t do it — we can do it. But the question is how can we make this efficient? How can we make this cost-effective?”In the new study, the team focused on the electrochemical conversion of CO2 to ethylene, a widely used chemical that can be made into a variety of plastics as well as fuels, and which today is made from petroleum. But the approach they developed could also be applied to producing other high-value chemical products as well, including methane, methanol, carbon monoxide, and others, the researchers say.Currently, ethylene sells for about $1,000 per ton, so the goal is to be able to meet or beat that price. The electrochemical process that converts CO2 into ethylene involves a water-based solution and a catalyst material, which come into contact along with an electric current in a device called a gas diffusion electrode.There are two competing characteristics of the gas diffusion electrode materials that affect their performance: They must be good electrical conductors so that the current that drives the process doesn’t get wasted through resistance heating, but they must also be “hydrophobic,” or water repelling, so the water-based electrolyte solution doesn’t leak through and interfere with the reactions taking place at the electrode surface.Unfortunately, it’s a tradeoff. Improving the conductivity reduces the hydrophobicity, and vice versa. Varanasi and his team set out to see if they could find a way around that conflict, and after many months of work, they did just that.The solution, devised by Rufer and Varanasi, is elegant in its simplicity. They used a plastic material, PTFE (essentially Teflon), that has been known to have good hydrophobic properties. However, PTFE’s lack of conductivity means that electrons must travel through a very thin catalyst layer, leading to significant voltage drop with distance. To overcome this limitation, the researchers wove a series of conductive copper wires through the very thin sheet of the PTFE.“This work really addressed this challenge, as we can now get both conductivity and hydrophobicity,” Varanasi says.Research on potential carbon conversion systems tends to be done on very small, lab-scale samples, typically less than 1-inch (2.5-centimeter) squares. To demonstrate the potential for scaling up, Varanasi’s team produced a sheet 10 times larger in area and demonstrated its effective performance.To get to that point, they had to do some basic tests that had apparently never been done before, running tests under identical conditions but using electrodes of different sizes to analyze the relationship between conductivity and electrode size. They found that conductivity dropped off dramatically with size, which would mean much more energy, and thus cost, would be needed to drive the reaction.“That’s exactly what we would expect, but it was something that nobody had really dedicatedly investigated before,” Rufer says. In addition, the larger sizes produced more unwanted chemical byproducts besides the intended ethylene.Real-world industrial applications would require electrodes that are perhaps 100 times larger than the lab versions, so adding the conductive wires will be necessary for making such systems practical, the researchers say. They also developed a model which captures the spatial variability in voltage and product distribution on electrodes due to ohmic losses. The model along with the experimental data they collected enabled them to calculate the optimal spacing for conductive wires to counteract the drop off in conductivity.In effect, by weaving the wire through the material, the material is divided into smaller subsections determined by the spacing of the wires. “We split it into a bunch of little subsegments, each of which is effectively a smaller electrode,” Rufer says. “And as we’ve seen, small electrodes can work really well.”Because the copper wire is so much more conductive than the PTFE material, it acts as a kind of superhighway for electrons passing through, bridging the areas where they are confined to the substrate and face greater resistance.To demonstrate that their system is robust, the researchers ran a test electrode for 75 hours continuously, with little change in performance. Overall, Rufer says, their system “is the first PTFE-based electrode which has gone beyond the lab scale on the order of 5 centimeters or smaller. It’s the first work that has progressed into a much larger scale and has done so without sacrificing efficiency.”The weaving process for incorporating the wire can be easily integrated into existing manufacturing processes, even in a large-scale roll-to-roll process, he adds.“Our approach is very powerful because it doesn’t have anything to do with the actual catalyst being used,” Rufer says. “You can sew this micrometric copper wire into any gas diffusion electrode you want, independent of catalyst morphology or chemistry. So, this approach can be used to scale anybody’s electrode.”“Given that we will need to process gigatons of CO2 annually to combat the CO2 challenge, we really need to think about solutions that can scale,” Varanasi says. “Starting with this mindset enables us to identify critical bottlenecks and develop innovative approaches that can make a meaningful impact in solving the problem. Our hierarchically conductive electrode is a result of such thinking.”The research team included MIT graduate students Michael Nitzsche and Sanjay Garimella, &nbsp;as well as Jack Lake PhD ’23. The work was supported by Shell, through the MIT Energy Initiative.This work was carried out, in part, through the use of MIT.nano facilities.

A conceptual schematic of the new woven electrode design. Researchers wove a series of conductive copper wires (the brown-orange pipe) through a very thin membrane to reach the catalyst. Image: Courtesy of the researchers, edited by MIT News

A new electrode design boosts the efficiency of electrochemical reactions that turn carbon dioxide into ethylene and other products.

Engineers make converting CO2 into useful products more practical

Developing an economy that produces net zero carbon emissions not only involves “capturing” carbon dioxide but changing it and putting it to use in new forms.&nbsp;Engineers at Washington University in St. Louis are heavily in the business of “carbon conversion” with multiple projects working on systems to pull carbon dioxide in and put it to good use.Most recently, the Department of Energy (DOE) has awarded $29 million in grants for “carbon management” technologies, including $1.5 million of those funds going to&nbsp;<a href="https://engineering.washu.edu/faculty/Xinhua-Liang.html">Xinhua Liang,</a> professor of energy, environmental &amp; chemical engineering in WashU's McKelvey School of Engineering.&nbsp;Previously, Liang&nbsp;<a href="https://engineering.washu.edu/news/2023/Carbon-negative-concrete-products-to-be-formed-from-upcycled-waste.html">received $2 million from the DOE</a> to convert CO2 to concrete products, and this continues that work, with a twist. Liang and his colleagues have developed a thermocatalytic process that could yield useful parts for increasingly ubiquitous lithium-ion batteries that power electric cars and other devices. Liang will fine-tune this process with his co-principal investigator, Miao Yu, a professor in the Department of Chemical and Biological Engineering at the University at Buffalo.&nbsp;The grant will fund Liang’s development of a low-carbon process to convert CO2 to valuable high-quality carbon nanotubes (CNTs). These nanotubes have “similar properties as commercial CNTs,” noted Liang, making them not only useful as potential anodes in batteries but doing so at a much more affordable price, a key component to scaling up these technologies.&nbsp;Lithium-ion batteries are composed of three main components: the anode (negative terminal), cathode (positive terminal) and electrolyte solution in between. The cathodes are typically made of lithium metal oxide, but the anode uses graphite, which is a form of carbon. CNTs are expected to have better performance than graphite as an anode material in lithium-ion batteries. But CNTs can be expensive to apply.But with Liang’s thermocatalytic process, they’ve drastically reduced that expense. They are taking CO2, converting it into an intermediate molecule and then a final conversion to a carbon nanotube with high capacity and high conductivity that makes it ideal for batteries. Carbon nanotubes can also be used in making composite metals and can be used in polymers and concrete products that Liang is also working on.“In order to commercialize this process, there is still a long way to go,” he adds.They will deliver a laboratory-scale prototype system capable of producing 20 grams per day of CNTs, according to the grant. Liang estimates that it could be ready for commercial use in a decade.&nbsp;But so far, they have found a way to lower the cost of CNT production from $100 per kilogram to less than $10.“This is the main advantage of our technology,” Liang said.

A 3D rendering of a carbon nanotube. Carbon dioxide can be turned into carbon nanotubes for use in lithium ion batteries and other potential products. (Image: Shutterstock)

A researcher at Washington University in St. Louis has received a grant of $1.5 million to convert CO2 into carbon nanotubes that could be used in lithium-ion batteries

Converting CO2 to solid carbon yields benefits for batteries and more

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