What is TPU filament?
TPU stands for Thermoplastic Polyurethane, an elastomer that combines the properties of rubber and plastic. The material is soft and pliable, yet it springs back to its original shape after being deformed. This makes it fundamentally different from rigid filaments like PLA or PETG, which are designed to hold their shape.
You probably already have something made of TPU at home. A clear, bendable phone case is often made of TPU. You can print that same material in filament form to create custom flexible parts.
The properties of TPU
TPU is popular because of a unique combination of properties you won't find in hard filaments.
The material is very flexible and elastic: you can stretch and bend it significantly, and it will bounce back. It’s also impact-resistant, so it absorbs shocks and bumps well without breaking. TPU is also exceptionally wear-resistant, making it suitable for parts that slide against each other or are subjected to repeated stress.
Furthermore, TPU is resistant to oil, grease, and many chemicals, and it is highly water-resistant. It performs reasonably well against UV and cold, though it isn't a standout in those areas. For long-term outdoor use in direct sunlight, ASA is a better choice.
In terms of temperature, TPU is moderate: it’s not a material you would choose for heat-resistant parts. For most flexible applications, that’s not an issue, but don’t count on it for parts that get really hot.
Shore hardness: how soft or stiff is TPU?
With flexible filaments, it’s all about Shore hardness. This value indicates how soft or stiff the material feels, and you’ll usually see it as a number followed by an A, such as 85A or 95A. The lower the number, the softer and more elastic the material.
- Shore 85A is soft and rubbery, similar to a shoe sole. Very flexible, but more difficult to print.
- Shore 95A is the most popular variant. It offers the best balance between flexibility and printability, making it the standard choice for most TPU prints.
- Shore 98A is stiffer and holds its shape better, making it suitable for parts that need to flex a little but mostly retain their form.
Not sure which hardness you need? For most applications, 95A is the safe bet: it's flexible enough and reliable to print.
You can also influence the final stiffness of your print through your design. More walls and a higher infill make a TPU part stiffer, while a lower infill results in a softer, more compressible feel.
Printing with TPU: what to keep in mind
TPU prints differently than rigid filament. Because the material is flexible, it can compress in the printer's feed system, a bit like a spring. This requires some adjustments, but with the right approach, TPU is easy to print.
Here are the most important points. Print slowly, as a low print speed prevents the filament from buckling or feeding inconsistently. A direct-drive extruder (where the drive is right above the hotend) offers much better control over flexible material than a system with a long Bowden tube.
Keep retraction low, as too much pulling back on flexible filament leads to clogs. It's better to tackle stringing—those fine wisps between parts—with a higher travel speed rather than more retraction.
Finally, TPU is hygroscopic, meaning it absorbs moisture from the air. Damp TPU results in dull, brittle prints with stringing, so storing it in a sealed container with desiccant makes a noticeable difference in quality.
TPU vs. TPE: what's the difference?
TPU and TPE are often mentioned in the same breath, and for good reason: TPU is actually a specific type within the broader TPE (Thermoplastic Elastomer) family. Both are flexible plastics that you can print just like regular filament.
The main difference lies in how easy they are to work with. TPE is a catch-all term and can be much softer and more elastic, which also makes it harder to print.
TPU is sturdier, holds its shape better, and is more wear-resistant, making it the more practical and reliable choice for 3D printing. If you come across the term TPE, always check the Shore hardness to see how flexible it actually is.
What is TPU used for?
The combination of flexibility, wear resistance, and shock absorption makes TPU suitable for applications where rigid plastics fall short. Common examples include flexible protective covers and phone cases, seals and gaskets, anti-slip parts and grips, shock and vibration dampers, and bumpers or protective edges.
In general, choose TPU when a part needs to flex, dampen, spring, provide grip, or absorb an impact. For rigid, dimensionally stable parts, you're better off with a hard material like PETG or ABS.
Frequently asked questions about TPU
Is TPU strong and durable?
Yes. TPU is wear-resistant, impact-resistant, and long-lasting because it is flexible and doesn't break easily. It is also resistant to oil, grease, and many chemicals, and it is recyclable. For parts that endure a lot of movement or stress, it is a durable choice.
Is TPU water-resistant?
Yes, TPU is naturally resistant to water and moisture, making it suitable for seals. Keep in mind: due to the layer structure of an FDM print, microscopic channels can form. For a truly waterproof application, print with high infill or apply a coating.
Is TPU difficult to print?
TPU is trickier than PLA, but definitely doable. It requires slow printing, low retraction, and preferably a direct-drive extruder. If you choose a harder variant like 95A or 98A, it prints much easier than the soft 85A.
Is TPU heat-resistant?
To a limited extent. TPU is not a heat-resistant material, so you wouldn't choose it for parts that get hot. For most flexible applications at room temperature or outdoors, that is not an issue.
Which Shore hardness should I choose?
For most applications, Shore 95A is the best choice: flexible enough and easy to print. Choose 85A if you want a truly soft, rubbery result, and 98A if the part needs to be stiffer and hold its shape better.
Get your part printed in TPU
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