TPU print settings for Bambu Lab A1, P1S and X1C that actually work

TPU is one of the more useful filaments to have on hand: gaskets, phone bumpers, vibration feet, watch straps, drone parts, tool grips. It is also the filament most likely to make a Bambu Lab printer behave oddly the first time you load it, because the soft filament path that works fine for PLA does not always tolerate a 95A shore rubber.

This article covers what I have found to actually work on the Bambu Lab A1, A1 Mini, P1S and X1C, where the printers differ, and where the official profiles need a small nudge. Settings below assume a generic 95A TPU (the most common variety). Softer TPUs (85A, 75A) need slower speeds and almost always need direct-spool feeding rather than the AMS.

Will TPU even run through your Bambu

Before touching any slicer setting, the mechanical question matters more than the temperature:

• A1 and A1 Mini: direct drive, short filament path. Handles 95A TPU well. Softer than about 90A becomes marginal.
• P1S and X1C: Bowden-style path from the AMS to the toolhead. The AMS itself is the bottleneck, not the hotend. Bambu officially supports TPU for AMS only for their own 95A TPU on a refillable spool, and even then it is fussy. Anything softer than 95A should be fed from the external spool holder, not the AMS.
• AMS Lite (A1 series): more forgiving than the original AMS because the path is shorter and the buffer is gentler, but still happiest with 95A and above.

If the filament feels noticeably squishy when you pinch it, assume the AMS will jam eventually and feed externally from the start. It saves an hour of debugging.

Temperatures

Generic 95A TPU lives in a narrower window than PLA. The Bambu generic TPU profile is a reasonable starting point, but most third-party TPUs (Sunlu, Polymaker, Overture, eSun) want a touch more heat than the default.

• Nozzle: 230-240 C for the first layer, 225-235 C for subsequent layers. If you see stringing or layer scarring, drop 5 C before changing anything else.
• Bed: 45-55 C is plenty. TPU sticks aggressively to a clean textured PEI plate at these temperatures. Above 60 C the first layer can deform.
• Chamber (X1C / P1S): do not actively heat. Leave the door open if anything. TPU does not need a hot chamber and the AMS prefers cooler ambient.

Always dry the filament. TPU is hygroscopic, and a damp spool will pop, string and underextrude regardless of how good your settings are. 50 C for 6-8 hours in a filament dryer is normal. If you have not used the spool in a fortnight, dry it again.

Speed and flow

This is where the Bambu defaults are too optimistic for TPU. The marketing speeds for PLA do not transfer.

• Outer wall: 20-30 mm/s. Slower if the part is small or detailed.
• Inner wall: 30-40 mm/s.
• Infill: 40-60 mm/s. Higher is possible but you will hear the extruder skip first.
• Travel: 150-200 mm/s is fine. Travel is not the bottleneck.
• Max volumetric speed: 4-6 mm3/s for 95A. Softer TPU drops to 2-3 mm3/s. The Bambu slicer respects this and will slow the print automatically if you set it correctly, which is more reliable than tweaking each individual speed.

Flow rate (extrusion multiplier) usually wants to come down very slightly: 0.96-0.98 for most generic 95A TPU. Run a flow calibration in Bambu Studio rather than guessing.

Retraction and stringing

TPU strings. It will always string more than PLA. The aim is to keep it manageable, not eliminate it.

1. A1 / A1 Mini (direct drive): retraction 0.6-1.0 mm at 30-40 mm/s. More than this and you get under-extrusion on the next move. 2. P1S / X1C with external spool: retraction 0.8-1.4 mm. The longer path tolerates slightly more, but pushing past 1.5 mm causes blobs more often than it stops stringing. 3. Z-hop: 0.2-0.4 mm. Helps with stringy parts but slows the print. 4. Wipe on retract: enable it. 5. Coasting: leave it off. It causes more problems with TPU than it solves.

If you still get strings, the fix is almost always drying the filament or dropping the nozzle temperature by 5 C, not chasing retraction values.

Cooling, walls and infill

• Part cooling fan: 50-80%. Full blast can cause layer separation on tall thin parts; too little and overhangs sag. Start at 60%.
• Walls: 3 perimeters minimum for functional parts. TPU strength comes from walls, not infill.
• Infill: 15-25% gyroid for flexible parts, 30-40% for parts that need to hold a shape. Gyroid keeps the part feeling like TPU; grid or rectilinear at high density makes it feel like a brick.
• First layer: 0.2-0.24 mm height, 100% flow. Squish matters more for TPU than any other filament. If the first layer is not properly fused to the plate, the nozzle drags soft filament around and the print fails within ten minutes.

Plate choice and adhesion

The Bambu textured PEI plate is the right answer for TPU. Do not use glue stick. Do not use the smooth high-temperature plate without a release agent because TPU bonds to it permanently and can tear chunks of PEI coating off when you remove the part.

If parts will not release from the textured plate after cooling, put the plate in the freezer for ten minutes. They will pop off cleanly.

Common failure modes

• Extruder clicking or skipping: filament too soft for the path, speed too high, or filament damp. In that order.
• Print looks under-extruded only in the middle of a layer: max volumetric speed set too high.
• Stringing got worse mid-print: filament absorbing moisture from the room. Dry it.
• Part welded to the plate: smooth plate or too-hot first layer. Use textured PEI and 45-55 C bed.
• AMS keeps trying to retract and reload: TPU not supported on AMS at this softness. Feed externally.

When to mail it in

If the printer extrudes fine with PLA but skips, grinds or jams every time you load TPU, the problem is usually mechanical: a worn extruder gear, a slightly out-of-spec PTFE tube, or an AMS that needs the buffer springs adjusting. None of that is fixed by tweaking slicer settings, and chasing it through trial and error gets expensive in wasted filament.

Hark Tech is mail-in only, UK-based, and works on Bambu Lab A1, A1 Mini, P1S and X1C. If you want a second pair of hands on a printer that will not cooperate with flexible filament, get in touch via the contact page with a short description of the symptoms and which printer you have. Turnaround is usually within a few working days once the printer arrives.