Intro: Why TPU is worth mastering
Thermoplastic polyurethane (TPU) is the go-to flexible filament for functional parts — seals, straps, bumpers and wearables. But because it behaves differently to PLA or PETG, many beginners hit problems: stringing, jams, poor dimensional accuracy. This guide helps UK makers quickly diagnose the most common mistakes and apply practical fixes so you waste less filament and produce reliable parts.
Top beginner mistakes and how to fix them
Mistake 1 — Using standard extruder settings
TPU needs different temperatures, speeds and retraction than stiff filaments. Fix it:
- Start at 210–230°C (check your filament data sheet). Bed 40–60°C for better adhesion.
- Slow your print speed. 20–30 mm/s for detailed parts, up to 40 mm/s for larger, simple objects.
- Reduce retraction: for direct-drive 0.5–2 mm; for Bowden 2–4 mm. Sometimes disabling retraction for short moves reduces jams.
Mistake 2 — Wrong printer hardware setup
Flexible filaments are more forgiving on a direct-drive extruder. If you have a Bowden setup, the long PTFE tube lets the filament compress and buckle.
- Best: use a direct-drive or convert to a short Bowden (small PTFE gap).
- Ensure the filament path is constrained and low-friction — add a filament guide and a proper spool holder to avoid snags.
Mistake 3 — Poor feeder tension and nozzle choice
Too much or too little extruder tension causes slipping or grinding.
- Adjust the spring tension so the drive gear bites but doesn’t deform the filament.
- If printing a lot of abrasive TPU (many TPU blends are mildly abrasive) use a hardened steel nozzle; brass wears quickly.
Mistake 4 — Bed adhesion and part deformation
TPU can lift or curl on corners if adhesion is poor or cooling is too strong.
- Use a clean PEI sheet, BuildTak or a PVA glue stick for quick adhesion.
- Apply a brim for small contact areas. Start with low fan (20–40%) after the first couple of layers.
Quick comparison: direct drive vs Bowden for TPU
| Setup | Pros | Cons |
|---|---|---|
| Direct drive | Consistent feeding, lower retraction, fewer jams | Heavier hotend, slightly more moving mass |
| Bowden | Lighter carriage, faster acceleration possible | Needs higher retraction, risk of compression and jams |
Actionable calibration checklist
- Calibrate e-steps and flow: print a single-wall cube, measure wall thickness and adjust extrusion multiplier.
- Print a temperature tower for your specific TPU spool in 5°C increments to find best layer bonding without excess ooze.
- Run a retraction test: start low and increase in 0.5 mm steps until stringing reduces but no under-extrusion appears.
- Print a small functional stress piece (hinge or gasket) and test real-world fit — adjust tolerances by ±0.1–0.2 mm as needed.
Pitfalls to watch
- Old or wet TPU: moisture causes bubbles and weak print surfaces. Store spools dry or use a filament dryer at 40–50°C for a few hours.
- Aggressive cooling: too much fan makes layers brittle; too little can deform small features.
- Expect dimensional differences: flexible parts compress; design allowances into holes and snaps.
Conclusion
TPU prints reliably once you apply a few principled changes: slow speeds, conservative retraction, good filament path and the right nozzle. If you print functional parts regularly, consider upgrading to a direct-drive kit and a hardened nozzle. For UK makers, I recommend testing with a small affordable spool and a calibration routine before committing to larger quantities — and check product pages for specific temperature and drying advice.
FAQ
1. Is TPU hard to print?
No — but it is different. With slower speeds, minimal retraction and a good filament path, most printers handle TPU well.
2. What print settings should I start with?
Try 210–230°C hotend, 40–60°C bed, 20–30 mm/s print speed, low retraction (0.5–2 mm direct-drive).
3. Can I use a Bowden printer?
Yes, but expect to tune retraction and consider a shorter PTFE tube or a filament guide to reduce buckling.
4. How do I stop stringing?
Reduce print temperature slightly, lower retraction distance and dry the filament. Retraction speed and coast settings can also help.
5. Do I need a special nozzle?
Not always — but if you print abrasive TPU blends frequently, a hardened steel nozzle extends life compared with brass.
6. How should I store TPU?
Keep spools sealed with desiccant in a dry box or use a filament dryer before printing to avoid moisture-related defects.
If you want specific product recommendations (TPU spools, hardened nozzles or direct-drive kits), I can point you to tested options and setup guides tailored for your printer model.