How to Print TPU Through the Bambu AMS (and When You Can’t)
Flexible filament and the AMS are natural enemies: the AMS feeds filament by pushing it through meters of tubing, and soft TPU responds to pushing by buckling, stretching and jamming. There is exactly one TPU designed to survive that path — Bambu’s stiff “TPU for AMS” — and this guide covers when to use it, its actual profile numbers, and what to do with every other TPU spool you own.
The one hard rule
Never feed regular TPU through the AMS — not even 95A. Only the dedicated “TPU for AMS” material (shore hardness 68D) is AMS-compatible. Everything else — 85A, 90A, 95A, any brand — goes on the external spool holder, fed directly to the extruder. A soft spool loaded into an AMS slot doesn’t fail immediately; it fails mid-print, deep in the feed path, and unjamming TPU from AMS internals is nobody’s favourite afternoon.
Why hardness is the whole story: the AMS pushes filament from behind, through long PTFE tubes, around bends, past the buffer and into the extruder. Push on a stiff strand and it transmits the force; push on a soft one and it buckles like wet spaghetti, wedging itself against the tube walls. At 68D, TPU for AMS is closer in stiffness to a rigid filament — stiff enough to be pushed, while still far more flexible than PLA in the printed part.
68D vs regular TPU: what you gain and lose
The printed parts differ. A 95A phone bumper is rubbery and squashable; a 68D part is better described as tough and bendy — think stiff living hinges, flexible clips and vibration-tolerant mounts rather than squishy grips. If the part must feel like rubber, you need soft TPU and the external spool holder; no AMS setting changes that.
Baseline: the two profiles side by side
Bambu ships separate profiles, and the differences show exactly what the AMS path demands (X2D-generation values):
| Setting | TPU for AMS (68D) | Generic TPU (soft) |
|---|---|---|
| Nozzle temperature | 230 °C | 230 °C |
| Allowed nozzle range | 220–240 °C | 200–250 °C |
| Bed, textured PEI | 35 °C | 35 °C |
| Bed, SuperTack | 0 = incompatible | 0 = incompatible |
| Retraction | 0.4 mm at 10 mm/s | 0.8 mm at 10 mm/s |
| Max volumetric speed | 18 mm³/s | 12 mm³/s |
| Flow ratio | 0.97 | 1.0 |
| Part cooling fan | 20–40 % | 100 % |
Read the volumetric row: the stiff material can be pushed through the nozzle 50 % faster than soft TPU, which is most of why AMS TPU prints feel almost like printing a normal filament. The shorter 0.4 mm retraction and both profiles’ deliberately slow 10 mm/s retraction speed follow the same logic as all TPU: gentle, minimal filament reversal so nothing buckles or grinds.
Note the plate rule carried over from regular TPU: no TPU on the SuperTack plate — Bambu marks the combination incompatible (bed temperature 0) because TPU can bond hard enough to tear the coating. Textured PEI at 35 °C is the home plate for both variants.
Setup that actually matters
Select the right profile, not generic TPU. Pick the TPU-for-AMS filament profile when the spool is in the AMS — the generic TPU profile’s 12 mm³/s limit and 0.8 mm retraction are tuned for soft TPU on the external holder, and running the AMS material on them just leaves speed on the table (while running soft TPU on the AMS profile actively causes jams).
Bambu Studio: the filament dropdown on the Prepare screenDry it before it matters: 8 hours at 70 °C. TPU in every hardness is thirsty, and wet TPU strings, bubbles and welds itself into blobs. If you own an AMS model with a drying function (AMS 2 Pro, AMS HT), drying in place before the print is the convenient path; otherwise use a filament dryer. 70 °C is also the ceiling — TPU cannot take more. Details in the drying guide.
Slow down for quality. Even at 68D, TPU rewards patience: if walls look starved at full speed, lower the max volumetric speed a few mm³/s rather than raising temperature first — flexibles under-extrude long before they overheat.
Bambu Studio: Filament settings → Filament → Max volumetric speedPrinting soft TPU instead: the external-spool checklist
If the part needs real squish, skip the AMS entirely:
- Mount the spool on the external holder and feed it through the direct PTFE path to the extruder — short and straight is the whole point.
- Make sure the spool unwinds freely: any drag on soft filament turns straight into under-extrusion.
- Use the generic TPU profile (230 °C, 0.8 mm retraction, 12 mm³/s) and accept that TPU always strings a little — dry it and lower the temperature before fighting retraction.
The full soft-TPU playbook — the five hard rules, adhesion quirks and brand cheat sheet — is in our TPU printing guide.
If the AMS still struggles
Loading or unloading failures with TPU for AMS usually trace to the same suspects as any AMS feed issue: a worn or kinked PTFE tube, debris in the buffer, or a tangled spool. Bambu’s AMS troubleshooting pages (linked below) walk the mechanical checks; just resist the temptation to “fix” a feed problem by switching to a softer spool — that direction only gets worse.
Frequently asked questions
Can I print regular TPU through the Bambu AMS?
No — never feed regular TPU through the AMS, not even 95A. Only Bambu's dedicated "TPU for AMS" (shore hardness 68D) is AMS-compatible; every softer TPU of any brand goes on the external spool holder, fed directly to the extruder. A soft spool in an AMS slot doesn't fail immediately — it fails mid-print, deep in the feed path, where unjamming TPU is a miserable job.
What settings does Bambu's TPU for AMS profile use?
The X2D-generation profile runs a 230 °C nozzle (range 220–240 °C), 35 °C textured PEI bed, 0.4 mm retraction at 10 mm/s, 18 mm³/s max volumetric speed, flow ratio 0.97 and 20–40 % part-cooling fan. That volumetric limit is 50 % higher than soft TPU's 12 mm³/s. The SuperTack plate is marked incompatible — TPU can bond hard enough to tear its coating.
Do I need to dry TPU before printing it through the AMS?
Yes, if in doubt — TPU in every hardness is thirsty, and wet TPU strings, bubbles and welds itself into blobs. Dry it 8 hours at 70 °C, which is also the ceiling TPU tolerates. If you own an AMS model with a drying function (AMS 2 Pro or AMS HT), drying in place before the print is the convenient path; otherwise use a filament dryer.
Flexible print not coming out right?
Answer five quick questions about your printer, filament and build plate, and our rule engine turns them into a prioritized fix list with exact slicer values — the same knowledge these guides are written from.
Get a personalized fix list in 2 minutes — free Works with Bambu Studio, OrcaSlicer, PrusaSlicer and Cura. No account needed.Sources
- TPU Printing Guide — Bambu Lab Wiki
- AMS filament loading & unloading failure troubleshooting — Bambu Lab Wiki
- Filament drying guide for AMS 2 Pro and AMS HT — Bambu Lab Wiki