TPU printing problems: buckling, stringing, poor feeding

This guide is for TPU prints that won't feed, buckle or wrap around the extruder gears, string, under-extrude or won't come off the plate. It collects what Bambu Lab, Prusa, NinjaTek, Polymaker, Siraya Tech, Overture, SUNLU and eSUN say, scoped to the product or printer each one names. It doesn't repeat our guides on which hardness and extruder suit each other. For that, read TPU compatibility and TPU hardness explained first. Start here:

Check the hardness against your printer first

Some TPU problems are hardware limits, not settings. Bambu's TPU guide says "TPU with a hardness of 85A or higher is recommended," because softer TPU "bends easily during feeding, which can cause filament buckling, tangling, or unstable extrusion." It also says "Bambu Lab printers do not currently support printing with TPU filaments rated below 85A hardness." On Bambu printers, TPU 85A isn't compatible with the A1 series or with 0.4 mm nozzles. Prusa says "the softer the filament is, the harder it is to print."

Our TPU compatibility guide covers how hardness, extruder type and feeding systems fit together.

Buckling and tangling at the extruder

Idler tension: the makers disagree

These are each maker's advice for its own printers and filaments. Change tension in small steps, one test at a time.

Loading and extruding slowly

Bambu's A, P and X series TPU guides all say to load slowly. Its X-series guide says: "When clicking the extrusion button on the screen, do not click continuously all the time, otherwise TPU will get tangled in the extruder gear and cause clogging." Once the gears have gripped the filament, Bambu says to keep clicking slowly until it extrudes evenly before printing.

Bambu lists "extruder clogging (Filament bending, causing a clog in the extruder gear; disassemble the extruder and remove the clogged filament)" as a common TPU problem. Before printing TPU on the A1 series, it says to check and clean the extruder, and to replace a worn extruder gear, "otherwise, there may be issues with filament slipping."

eSUN says "flexible materials are relatively soft and more prone to deforming at the extruder gears," and "you will need to lower the printing speed to reduce this extrusion deformation."

Prusa printers with a filament sensor

• CORE One+ and CORE One L. Prusa says a hardware switch on the side filament sensor case loosens the sensor lever. Move the latch to the front, the side marked with an x, to load flexible filament, and to the back to tighten it again.
• XL. Prusa says the XL "has a long path from the loading to the extruder nozzle," so flexible filament needs special attention, and points to a printable flex filament bypass.
• Automatic filament change. Prusa says it "might not work properly with flexible filaments."

If the extruder clicks or skips while printing TPU, our extruder clicking guide covers the other causes.

Feeding resistance: spool, path and extruder type

Bambu's A2L guide says "because TPU is highly flexible and tacky, feeding resistance must be minimized during printing. Excessive resistance (e.g., from an overly long PTFE tube) can easily lead to extruder gear slipping, filament wear, or even feeding interruptions." What Bambu says to do on its printers:

1. Raise the spool. "All filaments must have the spool elevated (the spool's discharge port should be higher than the toolhead's load port) to ensure smooth loading," per the A-series guide.
2. Use a large dry box. Bambu says TPU spools can widen from about 65.4 mm to 69.4 mm after drying, which can make them rub inside a 4 L dry box, so it "strongly" recommends the 5.8 L box and feeding from its side opening.
3. Check the spool turns. If you feel resistance while loading, Bambu says to check that the spool rotates smoothly in its container.
4. On the X series and P1 series, feed TPU 85A directly. Bambu's P-series guide says to load 85A "directly from above the printer into the extruder (loading through the PTFE tube is not supported)."
5. On the P series with TPU 90A, Bambu recommends placing the model "in the middle towards the front of the heatbed to reduce friction between the filament and the PTFE tube."

Does TPU need a direct-drive extruder?

Several TPU makers say what extruder their product needs:

• Polymaker PolyFlex TPU95: "Direct extruder with a gear ratio mechanical advantage highly recommended."
• Polymaker PolyFlex TPU90: "Direct extruder with a gear ratio mechanical advantage required." For both, Polymaker says "Make sure your printer is not setup as Bowden - any large gap between your extruder and hotend will cause printing issues."
• eSUN eTPU-95A: its data sheet recommends "a short-range two-wheel reduction extruder designed for flexibility," says eTPU-95A is "usually difficult to print on a remote extrusion machine," and suggests a remote extruder "can try to print at a slower speed at 20mm/s or even slower."
• Siraya Tech Flex TPU 85A: "optimized for FDM printers equipped with direct drive extruders." Siraya says to "mount the filament directly above the extruder" for the shortest path from spool to extruder.

AMS and other automatic feeders

Bambu's Notes for AMS say to "avoid using AMS to print flexible materials, including TPU, TPE," because "they may get stuck inside the AMS feed tube." Its TPU guide says only TPU for AMS works with the standard feeding of all AMS models. With TPU 85A, 90A and 95A HF, the AMS HT can only be used as "a sealed and drying chamber," fed through its dedicated TPU outlet. Bambu's TPU 95A HF store page, though, lists "All AMS Series NOT Compatible." Overture says "it is not recommended to use TPU with AMS," because it "can cause feeding issues, jams, or inconsistent extrusion inside the system."

How fast should you print TPU?

The speeds the makers give vary widely by product.

Prusa says that with higher speeds "you risk clogging the nozzle or tangling filament into the gears." Polymaker adds that on "a stock, older style printer" it would "recommend printing VERY slow." Overture's spec table lists a speed below 250 mm/s, but its own TPU printing tips give 20–40 mm/s.

Should you use retraction with TPU?

The makers don't agree on retraction for TPU.

Prusa's reason for keeping it low: "With lower retractions, there is a lower risk of clogging the nozzle or filament tangling." Start from the setting your filament's maker gives, and change it in small steps.

Stringing and oozing

NinjaTek says stringing "commonly occurs with flexible filaments." Bambu's TPU guide gives four fixes, in this order:

1. Print sequence by object. Cut down travel moves, using "Print sequence By object" or fewer models on the plate.
2. Lower the nozzle temperature by about 5 °C. Bambu says "excessive nozzle temperature may cause oozing," and after lowering it, to reduce the maximum volumetric flow rate by 0.4 mm³/s.
3. Adjust retraction, adding 0.2 mm if leaking is severe.
4. Dry the filament fully.

NinjaTek's advice is similar: increase travel speed, and reduce the nozzle temperature in 5° steps, because "the cooler the temperature, the less oozing you will see." Siraya says to "adjust retraction settings and print speed" and check the filament's moisture. Polymaker's TPU90 tips say to "dry the filament first, then tune retraction and travel settings if there is stringing."

Siraya says its black Flex TPU 85A "often performs better at slightly cooler temperatures" than the white, and that printers with shorter melt zones may need the top of its 200–225 °C range. Our stringing guide covers temperature and retraction tests in more detail.

Under-extrusion and clogs

Bambu's fixes for under-extrusion with TPU are to reduce print speed, check for feeding resistance, check the filament is dry, and check the hotend for residue. It also says to turn off Flow Dynamics Calibration before printing TPU.

• Use a clean nozzle. Bambu says to use a new nozzle or a dedicated TPU hotend, or cold-pull an old one first. It says a hotend previously used with carbon or glass fiber filaments "will greatly increase extrusion resistance and easily cause clogging," and recommends 3–5 cold pulls before printing TPU. If you need a new nozzle, our replacement nozzle shortlist groups parts by printer. NinjaTek says a partial clog from previous rigid filament is "common if switching from ABS or other high-temperature rigid materials."
• Clear a clog. NinjaTek says to "set nozzle to max temp or 250°C (whichever is lower). Feed material until you see a good, even flow from the nozzle."
• Long print runs. eSUN says "residue may build up in the nozzle during long print runs," and recommends cleaning filament, or replacing the nozzle and throat tube.
• Nozzle size. Bambu doesn't support TPU on a 0.2 mm nozzle. Polymaker says PolyFlex "will be very difficult to print with a small nozzle diameter." Siraya recommends a nozzle larger than 0.2 mm, with the best results typically on 0.4 mm. Bambu's store page for TPU 95A HF lists the 0.2 mm stainless steel nozzle and Cool Plate SuperTack as not compatible.

Our under-extrusion guide and clog diagnosis guide cover the general checks.

Drying

Bambu says "moist TPU can cause stringing, bubbles, and weak layer adhesion. Drying before printing is essential." The makers' settings for their own TPU:

A few warnings from the makers:

• Don't overdry Overture TPU. Overture says to "avoid extended drying times, as this can lead to the filament becoming brittle and unsuitable for printing."
• Siraya doesn't recommend a filament dryer for its TPU, "because heating cannot maintain a uniform temperature throughout the dryer."
• Bambu's AMS 2 Pro "may not be able to fully dry TPU," so Bambu says to use the heatbed or AMS HT instead. It also says the static drying mode is "not suitable" for TPU.
• Storage. Bambu says to keep TPU below 20% RH in a sealed box with desiccant. Siraya says below 15% humidity is ideal for prolonged storage.

Our wet filament guide covers how to tell if a spool is damp.

Bed adhesion and removal

With TPU, the makers worry about parts sticking too well as much as not sticking.

• Bambu Lab. Bambu says "except for the Cool Plate SuperTack, all other types of plates are compatible with TPU filaments," and that SuperTack "may result in overly strong adhesion." Its X-series table lists no glue for TPU 85A and 90A on the Smooth and Textured PEI plates, and glue for TPU 95A HF and TPU for AMS. Its A-series guide for TPU 90A says not to use adhesive on the Textured PEI plate, because it "may become overly sticky," and that other plates need adhesive. Bambu gives a bed temperature of 30–35 °C for TPU 85A and 90A. Its general filament guide table marks the Cool Plate as not recommended for TPU, while its A-series guide lists it as recommended for TPU 90A, so check the guide for your exact filament and printer.
• Prusa. "If you print on a smooth or satin sheet, apply a separation layer on it (glue stick or Kapton tape should work)." Prusa says its powder-coated textured sheet doesn't need one, and that some very soft flex materials "can bond to the bed too much and require the use of glue stick on the bed as a separator to prevent PEI damage."
• NinjaTek. "Glue and/or blue painter's tape is suggested if not using a heated bed."
• Siraya Tech. PEI or glass with a glue stick, and for poor adhesion, a glue stick or hairspray, or a slightly higher bed temperature.
• SUNLU. 50–60 °C with glue, on a PEI plate per its data sheet.

To remove a stuck TPU print, Bambu says "do not use excessive force," and to "gently lift one corner of the model to create a small gap, spray isopropyl alcohol into the gap, and then slowly peel the model away from the build plate." See also our print stuck to the bed guide and PEI sheet damage guide.

Supports and tall parts

• Support material. Bambu says "when printing TPU, PLA is recommended as the support filament," and to use light-colored PLA such as white, or a color close to the model, to reduce staining. To remove PLA support interfaces, it says to open a small gap at the edge, spray alcohol into the joint, wait, then separate slowly.
• Support gaps. Prusa suggests increasing the support Z distance to 0.3 mm and the XY separation to at least 100%.
• Single-extruder printers. Polymaker suggests orienting the model to minimize supports, or placing them where they won't show.
• Overhangs. eSUN says flexible materials have poorer cooling, and "it is highly recommended to add supports for overhang and bridging areas."
• Tall, thin models. Bambu says these aren't recommended, because TPU "is relatively soft" and the model "may wobble, leading to print failure."

Unloading TPU on Bambu printers

• X and P series: Bambu's store page for TPU 85A and 90A says not to press Unload when switching filaments, "as this may cause uncut TPU residue to get stuck in the extruder." Heat the nozzle to 250 °C, then retract and pull the filament out by hand.
• A series and A2L: manual unloading after heating is required. Bambu's A2L guide says to cut off the melted end right after unloading.
• H2 series: Bambu says pressing Unload for auto-retraction is allowed, and to maintain the filament cutter at the right inlet if you print TPU regularly.

A sensible order

1. Confirm your printer and nozzle support the TPU's hardness.
2. Dry the filament to its maker's setting.
3. Reduce feeding resistance: raise the spool, check it turns freely, shorten the path.
4. Load slowly, and check idler tension for your printer.
5. Print at the filament maker's speed, not your PLA speed.
6. Set retraction from the filament maker's numbers, and change it in small steps.
7. For stringing, reduce travel, then adjust temperature in 5 °C steps.
8. Clean or replace the nozzle if it was used for fiber-filled filament.

Checklist

• Hardness is one your printer maker supports (85A or harder on Bambu printers).
• Filament dried, and stored below 20% RH with desiccant.
• Spool turns freely and sits higher than the extruder inlet.
• Not fed through an AMS unless it's Bambu TPU for AMS.
• Extruder clean, gears not worn, and idler tension set per your maker.
• Print speed inside the filament maker's range.
• Retraction set from the filament maker's numbers.
• Clean nozzle in a size your maker supports (on Bambu printers, never 0.2 mm, and 0.6 mm or larger for TPU 85A).
• Build plate and glue match the maker's advice, and no Cool Plate SuperTack on Bambu printers.
• Parts removed gently, using isopropyl alcohol if Bambu's method suits your plate.

How this guide was checked

This is a research-based guide. We haven't run these tests for it. Every setting, quote and recommendation comes from the Bambu Lab, Prusa Research, NinjaTek, Polymaker, Siraya Tech, Overture, SUNLU and eSUN pages and data sheets listed in the sources, retrieved on 2026-10-13. Settings are kept to the product or printer each page names, and where makers disagree we show both. Read more in our editorial standards.

TPU: what to check before you buy a spool ↗