Why TPU Is Different From Every Other Filament
TPU (Thermoplastic Polyurethane) is the flexible filament most people reach for when a part needs to bend, absorb impact, or grip. Where PLA snaps and PETG creases, TPU stretches — it can be compressed, twisted and dropped without cracking. That flexibility is also exactly why it has a reputation for being "hard to print."
The material itself is not the problem. TPU fails on printers that were tuned for rigid filament: too much retraction, too much speed, too much tension. Once you understand the three things that make TPU behave differently, it prints as reliably as PLA.
The three properties that change everything
- Compressibility. Flexible filament buckles sideways under pressure instead of pushing straight. Any gap between the drive gear and the nozzle is a place where the filament will fold.
- Friction. TPU drags inside long PTFE tubes. The longer the path, the more resistance, and the more likely the extruder slips.
- Flexibility after printing. A finished TPU part bends — so it needs walls, not infill, to be strong.
Shore Hardness: Which TPU Should You Buy?
The number after "TPU" is its Shore hardness. Lower numbers are softer and more flexible; higher numbers are firmer and easier to print.
| Shore | Feel | Typical uses | Print difficulty |
|---|---|---|---|
| A85 | Soft, rubber-like | Phone cases, grips, gaskets, wearables | Hardest — direct drive strongly recommended |
| A90 | Balanced flex | Seals, bumpers, vibration dampers, prosthetics | Moderate |
| A95 | Firm, semi-flexible | Functional parts, wheels, tool handles, hinges | Easiest — prints well on most machines |
If this is your first flexible filament, start at A95. It behaves close enough to rigid filament that a standard profile will work, while still giving you real flexibility. When you need more give, step down to A90 or A85.
ANTINSKY's flexible range covers all three: TPU 95A (12 colors, the everyday choice), TPU 90A (11 colors, the balanced middle), and TPU 85A for the softest parts. There is also a high-speed variant, TPU 95A HS, and a lightweight TPU-LW 90A that prints noticeably lighter parts.
TPU Print Settings (Starting Points)
These are safe starting values for a 0.4 mm nozzle on a direct-drive printer. Tune from here — do not copy them blindly onto a Bowden machine.
| Setting | Value | Notes |
|---|---|---|
| Nozzle temperature | 220–240 °C | Higher = better layer bonding. Start at 230 °C |
| Bed temperature | 40–60 °C | PEI or textured plate works well; no glue needed |
| Print speed | 20–30 mm/s | Slow is the single biggest factor. A95 can reach 40 mm/s |
| Retraction distance | 0.4–1 mm (direct) | Bowden: 1–2 mm maximum, or disable entirely |
| Retraction speed | 20–25 mm/s | Fast retraction pulls soft filament out of shape |
| Flow rate | 95–100 % | Reduce slightly if layers look over-squished |
| Fan | 50–100 % | Full fan after the first layers |
| Layer height | 0.2 mm | 0.1–0.25 mm all work; avoid extremes |
| Infill | 15–25 % | Use more walls instead — see below |
Direct drive vs Bowden for TPU
Short filament paths are the difference between "TPU prints great" and "TPU jams every time." A direct-drive extruder sits right above the nozzle, so there is almost no room for filament to buckle. On a Bowden setup with a long PTFE tube, you have three options: reduce speed to 15–20 mm/s, increase tension on the drive gear, or print a flexible-filament-friendly extruder upgrade.
Walls beat infill
TPU parts fail along infill lines, not walls. If a part needs to be flexible and durable:
- Set perimeters to 4–6 walls (1.6–2.4 mm).
- Keep infill at 10–20 % — it barely contributes to flexible part strength.
- Use gyroid or cubic infill; avoid grid, which crosses and creates weak points.
Dry Your TPU — Every Time
TPU is hygroscopic: it absorbs moisture from the air, and wet TPU prints with pops, bubbles, poor layer adhesion and a rough surface. Store it sealed with desiccant, and dry before use if the spool has been open more than a few days.
| Method | Temperature | Time |
|---|---|---|
| Filament dryer (recommended) | 50–60 °C | 4–8 hours |
| Oven | 50 °C | 6–10 hours (verify your oven's accuracy first) |
A dedicated dryer such as the FilaBox or the larger FDC12 Dryer Cabinet lets you dry and print from the same unit, which removes the "dry it, then watch it absorb water again" problem. For the full drying workflow, see our guide on how to dry 3D printer filament.
TPU Troubleshooting: The Five Failures You Will Actually Hit
1. Filament buckles or jams at the extruder
Cause: too much back pressure — speed too high, temperature too low, or a long Bowden path.
Fix: drop speed to 20 mm/s, raise nozzle temperature 5–10 °C, reduce retraction distance. Loosen the idler tension slightly: over-tightening squashes the filament oval and makes it bind.
2. Stringing and oozing
Cause: TPU keeps flowing when the extruder pauses.
Fix: reduce retraction speed (20 mm/s), enable "wipe on retract," and lower temperature to the bottom of the range. Some stringing on flexible filament is normal — clean it with a heat gun or sharp blade.
3. Layers separate or the part splits
Cause: printing too fast and too cool, so the previous layer is already solid when the next arrives.
Fix: raise temperature to 235–240 °C, slow to 20 mm/s, and increase flow to 100–102 %.
4. Poor first layer / part lifts off the bed
Cause: bed too cold, or a flexible first layer being pulled by the nozzle.
Fix: bed 50–60 °C, slower first layer (10–15 mm/s), and a slightly higher first-layer flow. Textured PEI holds TPU well; if you use glue, use it as a release agent rather than an adhesive.
5. Finished part is too stiff (or too floppy)
Cause: geometry dominates flexibility, not the filament alone.
Fix: for more flexibility, reduce wall count to 2 and infill to 10 %; for more rigidity, go to 6 walls and 30 % infill. Changing walls moves flexibility far more than switching between 90A and 95A.
Design Rules for Flexible Parts
- No thin flat sections. Anything under 1.2 mm thick will curl. Design 1.6 mm minimum.
- Round the corners. Sharp internal corners concentrate stress and tear first.
- Think in cross-sections. A TPU part's stiffness scales with the cube of its thickness — doubling wall thickness makes it roughly eight times stiffer.
- Print orientation matters. Layers bond weaker than the filament itself, so orient the part so bending happens along the layers, not across them.
Frequently Asked Questions
Can I print TPU on a Bowden printer?
Yes, with limits. Keep speed under 20 mm/s, retraction short or off, and prefer A95 over softer grades. Longer PTFE tubes make soft TPU progressively harder.
Does TPU need an enclosure?
No. TPU prints fine in open air. An enclosure mainly helps with ABS and ASA.
Which build plate is best for TPU?
Textured PEI works best — it grips without adhesive and releases cleanly once cool. Smooth glass with glue also works. Avoid printing TPU directly on a bare smooth PEI sheet if you have had tearing issues.
How long does a TPU print take?
Roughly two to three times longer than the same model in PLA, because of the lower speed. Budget accordingly for large parts.
Can TPU and PLA share a nozzle?
Yes, but purge thoroughly. Residual PLA in a TPU print creates hard specks; residual TPU in a PLA print can clog. Purge 100 mm of the new material before starting.
The Short Version
Print TPU slow (20–30 mm/s), hot (230–240 °C), with almost no retraction, and dry the spool first. Use walls rather than infill for strength, and choose hardness by application: A95 for functional parts, A90 for seals and dampers, A85 for soft grips. Do those things and TPU stops being the difficult filament.
Browse the full flexible range: TPU 95A · TPU 90A · TPU 85A · TPU 95A HS