TPU 95A Thermoplastic polyurethane, Shore 95A (TPU 95A)

TPU (thermoplastic polyurethane) is a rubber-like plastic that can be melted and printed like any other filament. It behaves like a firm rubber: it bends, stretches and springs back, and it absorbs knocks that would crack a rigid part. When you hold a TPU 95A print it feels like a skateboard wheel or a tough phone case rather than a soft gasket or a gummy sweet.

The “95A” is a Shore hardness rating, measured by pressing a standard indenter into the material and reading how far it sinks. The Shore A scale is used for rubbers and soft elastomers, and the Shore D scale (with a sharper indenter) for harder, more plastic-like materials; on both scales a higher number means harder. The two scales overlap, so QIDI ranks TPUs from hardest to softest as 77D, 70D, 55D, then 95A, 85A, 83A and below. In practice 95A is the firm end of “rubbery”: flexible in thin sections, surprisingly stiff in thick ones.

We offer 95A and nothing softer, for a printer reason rather than a commercial one. QIDI's TPU guide says grades of “85A, 83A, or lower should not be printed using QIDI printers”, because very soft filament gets squashed by the extruder gears and jams. The Max4 FAQ likewise names 95A as the recommended hardness. If your design calls for a genuinely soft, squishy feel (a typical earbud tip or a soft-touch seal), FDM TPU 95A will feel harder than you expect and molded silicone or a softer cast urethane is the honest answer.

There are harder flexible options too. The QIDI Box multi-material unit accepts hard TPU 64D, and QIDI's glass-filled TPU-GF is rated 67 Shore D: these feel more like a tough, slightly springy plastic than a rubber and suit parts such as impact-absorbing brackets. At the other extreme, QIDI's TPU-Aero is a foaming TPU whose effective hardness can be tuned from 85A down to 65A by print temperature and flow; it is a niche option for lightweight cushioning and is printed only by arrangement. Standard TPU 95A itself is fed to the printer from an external spool, not through the QIDI Box.

TPU's value is toughness and recovery, not raw strength. Polymaker's PolyFlex TPU95 data sheet lists an elongation at break around 551 % in the XY plane, which means a printed strip can stretch to several times its length before it tears. Its Young's modulus of about 33.6 MPa is tiny compared with rigid plastics, which is why the part bends instead of cracking. Stress at 300 % strain is around 21 MPa, so it takes real force to stretch it that far.

Unlike rigid filaments, TPU fuses so well between layers that the usual weak plane is far less of a concern. FDM parts are still somewhat weaker across layers (the Z direction) than along them, a property called anisotropy, so if a TPU part will be stretched hard in one direction, orient it so the stretch runs along the layers where possible. For bending parts such as hinges and clips, lay the flexing section flat on the bed so it bends across the layer lines rather than peeling them apart.

Stiffness in TPU is mostly set by geometry and print settings rather than the material alone. The same 95A filament can produce a floppy strap or a near-rigid block depending on wall count, infill percentage, infill pattern and thickness. That gives you a design lever: tell us how firm the part should feel, and we can tune perimeters and infill, or print test coupons at different settings so you can choose by hand.

The main mechanical weaknesses are creep and compression set. Under steady load or long-term squeeze (a gasket clamped for months, a foot carrying a heavy machine), TPU slowly flattens and doesn't fully spring back. Design seals and feet with generous contact area and modest compression, and treat them as replaceable wear parts.

TPU 95A sits low in our heat ratings. It doesn't melt at moderate temperatures, but it softens progressively as it warms, so it loses firmness and takes a set more readily when hot, especially under load. QIDI doesn't publish an HDT (heat deflection temperature, the temperature at which a loaded test bar bends a set amount) for its TPU95A-HF, and for flexible materials HDT is rarely meaningful anyway because they deflect under load at room temperature.

If you need flexible parts that tolerate more heat, ask about harder grades. QIDI's TPU-GF, a 67 Shore D glass-filled TPU, lists a Vicat softening temperature of 157.3 °C (the temperature at which a loaded needle sinks into the material), though it is much stiffer than 95A. For cold use, TPU generally stays flexible well below freezing, which is one of its advantages over rigid plastics that turn brittle.

Like most polyurethanes, ordinary TPU is not formulated for long-term outdoor UV exposure. Sunlight generally causes yellowing and, over longer periods, surface stiffening and fine cracking. For parts that live outdoors, choose black where possible, avoid thin sections that would degrade quickly, and plan to replace them periodically. If the part does not need to flex, ASA is our go-to outdoor material.

TPU generally resists oils and greases well, which is why it shows up in seals and hoses. Polymaker rates PolyFlex TPU95 good against oils and greases, fair against weak acids and alkalis, and poor against strong acids and strong alkalis.

Solvents such as acetone and some fuels can generally swell or attack polyurethanes, and long immersion in hot water can slowly degrade them (polyurethanes can hydrolyze). Short splashes of isopropyl alcohol for cleaning are usually tolerated, but if your part will live in gasoline, brake fluid, cleaning chemicals or sunscreen, send us the product name and we'll suggest a soak test on a sample before you order a batch.

TPU is hygroscopic, meaning it absorbs moisture from the air; QIDI lists a saturated water absorption of 1.62 % for its TPU95A-HF. Wet filament prints with bubbles, stringing and a rough, weakened surface, so we dry it before printing (QIDI suggests 70–80 °C for 4–6 hours). Finished parts are much less affected than raw filament: a printed TPU part used in damp conditions generally stays flexible and functional, but very long immersion, especially in hot water, is not recommended.

TPU 95A prints with a slightly satin, rubbery surface and visible layer lines. Fine stringing between features is normal for flexible filament; QIDI's own wiki notes that drying reduces but doesn't eliminate it, and we remove it during cleanup.

Sharp corners come out slightly rounded and small features can look soft, because the material is elastic as it's laid down. Supported overhangs leave a rougher underside, and support removal is harder than on rigid plastics because TPU bonds strongly to itself; we prefer orientations that avoid supports altogether.

Post-processing options are limited. TPU doesn't sand well (it smears and pills rather than cutting cleanly), and it doesn't hold paint well because the paint cracks when the part flexes; flexible paints exist but are best tested on a sample. Vapour smoothing is not something we offer for this material.

We clean up strings and support witness marks by hand, and trimming flash with a sharp blade works well. Heat-set inserts can be pressed in, but because TPU is soft they hold poorly under torque; for fastening, a captured nut, a molded-in rigid insert or a clamp design is usually better. Annealing is not a meaningful process for TPU 95A, and QIDI lists it as not recommended.

Expect looser dimensional tolerance than rigid materials. TPU is printed slowly and with careful flow control, but elastic stretch during extrusion, slight over-extrusion at corners and bulging on thin walls all make tight fits harder to hit. Holes typically print a little undersized; the good news is that a flexible part can often be stretched over a slightly oversized boss.

Measure critical TPU parts the way they will be used. A gasket compressed in a groove or a sleeve stretched over a handle behaves differently from the free part on the bench. For press fits and seals we suggest a quick test print with two or three interference values before ordering quantities.