TPU print settings: practical guide to flexible 3D printing

TPU (thermoplastic polyurethane) is a flexible filament used for phone cases, gaskets, cable tidies, hinges, and any part that needs to absorb shock or bend without snapping. It prints at similar temperatures to PLA but behaves very differently, and most of the trouble people run into comes from applying standard PLA or PETG settings without adjustment.

This guide covers the key settings, common failure modes, and what to do when TPU refuses to cooperate.

Hardware: direct drive versus Bowden

The single most important variable before you touch any slicer setting is your extruder setup.

TPU is soft and compressible. In a Bowden system the filament travels through a long PTFE tube between the extruder motor and the hotend. That gap acts like a spring — when you try to push or retract the filament, it compresses slightly, causing under-extrusion, stringing, and inconsistent flow. Printing TPU on a Bowden machine is possible at Shore hardness 95A (the most common, semi-rigid grade) but requires patience and low speeds. Softer grades such as 87A are much harder to manage on Bowden.

A direct-drive extruder, where the motor sits directly above the hotend, eliminates most of that compliance. If you have a choice, use it. Machines such as the Bambu Lab A1 and P1 series, Creality K1 and K2, and the Prusa MK4 all have direct-drive setups and handle TPU well. Older Ender 3 models with stock Bowden setups are workable at low speeds but may need an extruder upgrade for consistent results.

Dual-drive extruders (BMG-style) grip the filament on both sides and handle flexible materials noticeably better than single-drive designs.

Temperature

Nozzle: Start at 220 °C and adjust in 5 °C steps. Most TPU filaments print between 215 °C and 240 °C. If the print looks rough or under-extruded, increase temperature. If you are getting blobs or the filament smells burnt, lower it. Check your filament manufacturer's datasheet — Shore 95A TPU often prints cooler than Shore 87A.

Bed: TPU can print on an unheated bed with the right surface, but 30–50 °C improves first-layer adhesion. Textured PEI spring-steel sheets, rough powder-coated PEI, and clean glass with a thin coat of PVA glue stick all work well. Avoid the smooth PEI side at bed temperatures above 40 °C — TPU can fuse to the surface and you risk tearing the coating when removing the part.

Print speed

Speed is where most people go wrong. TPU is not rigid and cannot be pushed through the hotend at the same pace as PLA.

• First layer: 10–15 mm/s
• Perimeters (outer walls): 15–25 mm/s
• Infill: 20–30 mm/s
• Travel: 100–150 mm/s — fast travel is fine, it is extrusion that must be slow

If you push past 35–40 mm/s on a standard hotend you will likely see under-extrusion, inconsistent walls, or the extruder grinding the filament. High-flow hotends (Bambu X1C, Creality K2) can run somewhat faster, but 25–30 mm/s remains a safe starting point for a new filament.

Retraction

This is the most counterintuitive part of printing TPU.

Because the filament is elastic, large retraction distances cause it to stretch and then snap back, leaving a compressed plug in the nozzle. The result is under-extrusion after every travel move.

Direct drive: 0–1 mm retraction at 25–35 mm/s. Start at 0.5 mm and reduce if you still see stringing after adjusting temperature. Many people get cleaner results with retraction disabled entirely for TPU.

Bowden: 3–5 mm at 25 mm/s. Longer distances compensate for tube compliance, but beyond 6–7 mm you will grind the filament.

Stringing on TPU is usually better tackled by raising the nozzle temperature by 5 °C (reduces filament viscosity so it cuts more cleanly), reducing retraction distance, and enabling combing or avoid-crossing-perimeters in your slicer so the nozzle stays over the part during travel.

Cooling

Moderate cooling helps TPU bridging and reduces stringing, but heavy cooling at low print speeds can cause the nozzle to drag the still-soft previous layer. A fan at 40–60% is a reasonable starting point. On small or intricate models you can push to 80–100%. Reduce it if you see layer delamination or rough surfaces.

Unlike PLA, TPU does not usually need zero fan on the first layer. A gentle airflow of 20–30% from the first layer upward is fine.

Layer height and wall count

TPU's flexibility means thin-walled parts are springy and thick-walled parts are stiff. Design intent drives these choices more than material limits, but some general guidance:

• Layer height: 0.2 mm is reliable. 0.3 mm is fine for functional parts where surface finish is not critical. Below 0.15 mm, TPU can have trouble with consistent extrusion at the low speeds involved.
• Wall count: 3–4 perimeters for flexible, compliant parts. 6–8 perimeters for parts that should resist deformation. Phone cases and gaskets typically use 3 perimeters with 10–20% gyroid or honeycomb infill.
• Top and bottom layers: 4–5 layers is usually sufficient. Reducing to 3 can leave flat surfaces uneven on flexible materials.

Infill

For flexible parts, use gyroid or honeycomb infill at 10–20%. These patterns deform gracefully under load without stress concentrations. Rectilinear or grid infill at the same density will feel stiffer and may crack at crossing points under repeated flexing.

For parts printed in TPU that should be rigid but impact-resistant (brackets, bumpers), 40–60% gyroid works well.

Flow rate calibration

TPU's compressibility means the slicer's default volumetric flow assumptions can over-extrude slightly. Print a single-wall calibration cube at 0.4 mm nominal wall thickness and measure the result. If walls are consistently 10–15% thicker than expected, reduce flow rate by that amount in your filament profile. Start at 95% and adjust from there.

Common problems

Grinding at the extruder: Speed is too high, or the idler tension is too tight. Reduce speed first. If grinding continues, back off the idler screw slightly — flexible filament buckles if pinched too hard.

Spaghetti or under-extrusion mid-print: Often caused by the filament tangling on the spool. TPU is springy and can snag on itself or loop under adjacent coils. Feed from a dry box with a consistent tension path, or use a spool holder that allows free rotation without the spool wobbling.

Stringing: Reduce retraction distance (not increase it), raise temperature by 5 °C, and enable combing in your slicer to keep the nozzle over the part during travel moves.

First layer not sticking: Increase bed temperature by 5 °C, clean the bed with isopropyl alcohol, and slow the first layer to 10 mm/s. A light coat of PVA glue stick on glass helps on stubborn surfaces.

Warping on large flat parts: Enclosing the printer to maintain a warm ambient temperature helps, even though TPU does not warp as severely as ABS. A brim of 5–8 mm is usually enough for large footprints.

When to mail it in

If you need a TPU part printed but do not own a suitable printer, or your machine is not cooperating with flexible filament despite trying the settings above, Hark Tech can print TPU parts as a mail-in service. Upload your STL file for an instant quote, or get in touch via the contact page if you have a specific requirement — unusual geometry, a large part, or a combination of rigid and flexible materials in the same assembly. Turnaround is within a few working days, and all orders include tracked return postage.