How to Print TPU Flexibles on the Kobra 3 Without Clogs
kobra3tpuflexibledirect drive
TPU is rubbery, bendy, and incredibly useful — but it can be a nightmare if you don't slow down. The Kobra 3's direct drive handles it well with the right approach.
Why TPU Clogs
TPU is soft and compressible. Too much back pressure and it buckles in the feed path before the nozzle. The solution: go slow enough that there's minimal back pressure at all times.
Settings
| Setting | Value |
|---|---|
| Nozzle temp | 225–235°C |
| Bed temp | 40–50°C |
| Print speed | 25–35 mm/s |
| First layer speed | 20 mm/s |
| Retraction | 0–0.8 mm |
| Retraction speed | 20 mm/s |
| Cooling fan | 30–50% |
Key Rules
- No ACE Pro for TPU — load single channel direct into the extruder
- Minimize retraction — TPU compresses instead of retracting cleanly, causing blobs
- Never exceed 40 mm/s — speed is the number one cause of TPU clogs
- Keep bowden path clear — any resistance = buckling
Shore Hardness Guide
| Hardness | Print Speed | Notes |
|---|---|---|
| 95A (firm) | 30–35 mm/s | Easiest TPU to print |
| 87A (medium) | 25 mm/s | Good balance |
| 82A (soft) | 20 mm/s | Needs care |
| 70A (very soft) | 15 mm/s | Extremely slow, often clogs |
If It Clogs
- Heat nozzle to 240°C
- Manual extrude slowly — if resistance, stop
- Do a cold pull at 90°C
- If blocked, remove nozzle and clear with acupuncture needle
Post-Printing
TPU parts are sticky — don't stack them. Store flat. PEI release is usually good without glue stick.