# TPU Filament for 3D Printing: Shore Hardness Explained

> What is TPU filament for 3D printing? What 85A and 95A Shore hardness feel like, how to design flexible parts, print temperatures, and the $0.25/g rate.

Source: https://x3dstudios.com/blog/tpu-explained  ·  2026-10-18  ·  Updated: 2026-10-23  ·  X3D Studios  ·  9 min read

TPU filament for 3D printing is thermoplastic polyurethane: a rubber-like plastic that prints on a normal FDM printer but comes out squishy instead of rigid. How squishy is set by one number, the Shore hardness, which for printable grades runs from about 85A (bendy, like an inner tube) to 95A (firm, like a shoe sole). It is the material behind phone bumpers, gaskets, wheels, straps, and anything that has to flex thousands of times without cracking, and it prints at $0.25 per gram all-in on our farm.

## What Is TPU Filament for 3D Printing?

Most filaments are one long, stiff polymer chain. TPU is a block copolymer: it alternates hard segments that hold the part's shape with soft segments that let it stretch. Pull on a TPU part and the soft blocks uncoil; release it and the hard blocks pull everything back. That is why TPU stretches several times its own length and springs back, while PLA snaps.

The ratio of hard to soft blocks is the recipe knob a filament maker turns, and the resulting firmness is reported as a durometer reading. That reading is the single most useful spec on a TPU spool, more useful than tensile strength or elongation, because it is the property you feel in your hand the moment you pick the part up.

## Shore Hardness: The Number That Matters

Shore hardness is measured by pressing a standardised spring-loaded needle into the material and reading how far it sinks. Soft materials use the Shore A scale, hard ones the Shore D scale. A reading of 95A means "95 on the A scale" — firm rubber. Above roughly 100A the A scale runs out of room and hardness is quoted in Shore D instead, which is where nylons and rigid plastics live.

![Shore A hardness bar chart: rubber band 25A, pencil eraser 50A, bike tire tread 70A, TPU 85A, TPU 95A, skateboard wheel 98A](https://x3dstudios.com/blog-images/tpu-explained/shore-hardness-scale.svg)

*Printable TPU clusters in the top quarter of the Shore A scale — firmer than most people expect.*

That last point surprises people. TPU is described as "flexible filament", so first-time buyers imagine something like a rubber band. A 95A print is closer to a skateboard wheel: it bends, it absorbs impact, it will not hold a crease, but you cannot squash it between two fingers. If you want genuinely squishy, you have to ask for it by number.

| Durometer | Feels like | Prints like | Typical parts |
| --- | --- | --- | --- |
| 70A–80A | A soft eraser, deforms under a thumb | Hard: slow, fussy, direct drive only | Squeeze toys, soft pads, damping feet |
| 85A | A bicycle inner tube | Slow but reliable | Gaskets, seals, soft bumpers, wearables |
| 95A | The sole of a running shoe | The shop standard, most forgiving | Phone cases, straps, grips, hinges |
| 98A and up | A skateboard wheel | Almost as easy as PETG | Wheels, rollers, flexing snap tabs |

> **TIP** — The material picker offers one flexible option, Flexible TPU. If your part needs a particular durometer, ask at /contact before you order and we will tell you which grade is on the spool and whether another can be sourced. Describing the feel helps: "as firm as a shoe sole" or "soft enough to squeeze shut".

## Geometry Changes the Feel More Than the Spool Does

A durometer number describes the raw plastic, not the printed object. An FDM part is a shell with a lattice inside, so two prints from the same spool can feel completely different depending on how they were sliced. This is the part that trips up people coming from injection moulding, and it is also the most useful design lever you get.

- Infill density is a hardness dial. A 15% gyroid TPU block squishes like foam; the same block at 60% feels nearly solid.
- Wall count sets the skin. Two perimeters flex; four perimeters resist. Most of a flexible part's stiffness lives in the walls, not the core.
- Wall thickness beats material choice. A 1.2 mm TPU wall is floppy, a 3 mm wall in the same 95A filament is stiff. Change the model before you change the spool.
- Direction matters. TPU stretches happily along the layer lines and delaminates when pulled across them, so orient the flex axis with the layers.

A worked example: a phone bumper that feels too rigid rarely needs softer filament. Dropping from three walls to two and from 20% to 10% infill makes the same 95A model noticeably easier to stretch over a phone, and it takes a couple of grams off the billable weight at the same time. /blog/3d-printing-infill-explained covers what each density does to weight, strength and price.

## Designing Parts That Print Well in TPU

TPU is forgiving about impact and unforgiving about geometry. The filament behaves like a spring in the extruder — push it and it compresses before it moves — so anything that demands sharp starts and stops of the flow tends to blur. It also squashes into a fit rather than butting up against it, which changes every clearance you designed; /blog/3d-printing-tolerances-guide has the starting numbers for FDM gaps.

1. Keep walls at 1.6 mm or more unless you specifically want floppy. Thin TPU walls print fine and feel like nothing.
2. Avoid long bridges and steep overhangs. Molten TPU sags and will not tension across a gap the way PLA does; supports also stick to it far more stubbornly.
3. Expect softer detail. Small embossed text, crisp chamfers, and fine surface texture come out rounder than in PLA. Oversize engraved features rather than raised ones.
4. Design in clearance. TPU parts squash into a fit, so a press-fit that was perfect in PLA will be tight and hard to remove.
5. Do not ask TPU to be rigid. Snap-fit latches that should click and stay put will creep and relax. Print the rigid half in PETG and the flexing half in TPU.
6. Round every internal corner. Sharp corners concentrate stress in a part that is designed to bend, and that is where a flexible print eventually tears.

> **WARNING** — TPU is strongly hygroscopic — it absorbs moisture from the air faster than PLA or PETG. A wet spool prints with popping, stringing, and a rough, foamy surface. Every flexible spool on our farm gets dried before it goes on a machine, which is a large part of why TPU prints come out clean here and fail at home.

## How TPU Prints on the Farm

Flexible filament needs a direct-drive extruder — the motor has to grip the filament right above the nozzle, because a long push tube lets the material buckle instead of feed. Our Bambu H2S and P2S machines are direct drive, which is the precondition for running TPU at all.

Beyond that, TPU is a patience material. It runs at a fraction of PLA's speed, uses little or no retraction to avoid jamming, and prints best with slow, steady flow. Plan on a TPU part occupying a printer noticeably longer than the identical part in PLA — which matters for your lead time, not your bill, because our per-gram rate already covers normal machine time.

One thing worth knowing before you order: TPU prints in one colour. The AMS cannot feed flexible filament through its long guided path, so the farm runs TPU from each printer's external spool, one spool per job. A multi-colour project uploaded in TPU prints in a single colour; for multi-colour flexible parts, print the rigid colours in PLA or PETG and the flexible piece separately. /blog/multi-color-3d-printing-explained covers how the AMS handles colour changes, and /docs/materials lists what each material can do.

## TPU Filament Settings and Temperatures

If you are printing TPU yourself, these are the ranges most 95A filaments are happy in. Always start from the numbers printed on your own spool, because blends differ:

| Setting | Typical for 95A TPU | Why |
| --- | --- | --- |
| Nozzle temperature | 220–240 °C | Hot enough to flow, cool enough not to string badly |
| Bed temperature | 35–60 °C | TPU sticks well; too hot and it fuses to PEI |
| Print speed | 15–40 mm/s | Fast feeding makes soft filament buckle in the extruder |
| Retraction | Off, or under 1 mm | Long retractions stretch and jam flexible filament |
| Part cooling | Moderate, 30–60% | Helps overhangs without weakening layer bonds |
| Drying | 4–6 hours at about 50 °C | TPU absorbs moisture fast; wet TPU strings and pops |

Softer grades (85A and below) want the slow end of every range and a direct-drive extruder with a constrained filament path. On the farm we slice TPU with Bambu's Generic TPU preset for the exact printer it runs on, so you do not set any of this when you order — but it explains why a TPU part spends longer on a printer than the same shape in PLA. /blog/why-we-dry-filament covers the moisture side.

## What TPU Costs

TPU prices at $0.25 per gram, all-in: filament and normal machine time in one number, no separate setup fee. That is thirteen cents a gram over PLA, so a TPU part costs a little over twice the same shape in PLA, which on the small parts TPU is usually used for still means a few dollars. Billable weight rounds up to the whole gram and there is a $1.00 minimum per part, which in TPU only catches parts of 4 g or less.

![Bar chart of four TPU parts and their PLA equivalents: drone skid pair 34g $8.50 vs $4.08, phone bumper 22g $5.50 vs $2.64, watch strap 18g $4.50 vs $2.16, gasket ring 7g $1.75 vs $1.00](https://x3dstudios.com/blog-images/tpu-explained/tpu-part-cost.svg)

*TPU costs thirteen cents a gram more than PLA. On a 22-gram phone bumper that is $2.86.*

| Part | Weight | TPU at $0.25/g | Same part in PLA |
| --- | --- | --- | --- |
| Gasket ring, 90 mm | 7 g | $1.75 | $1.00 (minimum) |
| Watch strap | 18 g | $4.50 | $2.16 |
| Phone bumper | 22 g | $5.50 | $2.64 |
| Drone skid pair | 34 g | $8.50 | $4.08 |
| Set of 8 chair feet | 48 g | $12.00 | $5.76 |

Shipping is $7 flat anywhere in the US and free over $49.50, which at $0.25 a gram is about 200 g of TPU. Express is $15 and never free. Order five or more of the same part and a 5% bulk discount applies, ten or more takes 10% off. The full rate card, including the 1.75× multiplier for premium 0.1 mm layers, lives on /pricing.

## Ordering a Flexible Print

Upload your model at /print in STL, GLB or 3MF (a sliced plate as .gcode.3mf) — OBJ is not accepted, so convert first if that is what you have. The quote comes from a real OrcaSlicer slice of your actual geometry wherever possible, not a bounding-box guess, which matters more for TPU than for anything else: a sparse flexible lattice and a solid block of the same shape differ enormously in weight, and only a real slice knows which one you uploaded.

The build volume is 340 × 320 × 340 mm, big enough for most flexible work in one piece. If you send a pre-sliced G-code file it goes through automated safety validation before any printer touches it, and while the job runs an operator watches it on a live camera. We are in Austin, Texas; normal print ships in 4–5 business days, or 1–2 with Priority print ($5 at checkout).

If you are still deciding whether flexible is even the right answer, /blog/pla-vs-petg-vs-abs-vs-asa-vs-tpu puts all five materials side by side. The short version: if the part is supposed to bend by design rather than by accident, TPU is the only one of the five that qualifies.

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## FAQ

### What Shore hardness should I pick for a phone case?

95A. It is firm enough to hold its shape on the shelf and to grip the phone without stretching out over time, and soft enough to absorb a drop. An 85A case works too but tends to feel slack after a few months of being pulled on and off. Below 85A a case is hard to keep on the phone at all.

### Is TPU stronger than PLA?

It fails differently rather than being straightforwardly stronger. TPU is far tougher: it absorbs impact, survives repeated bending, and stretches instead of shattering. PLA is far stiffer: it resists a load without deflecting, where TPU simply moves out of the way. For a bracket that must not bend, PLA or PETG wins. For a part that gets dropped, stepped on, or flexed daily, TPU wins outright.

### Can TPU be used outdoors?

Reasonably well. TPU handles moisture and holds up in sunlight much better than PLA or ABS, which is why it appears in tires, cable jackets, and phone cases. For a part that lives in permanent direct sun year-round and must not fade or go brittle, ASA is the purpose-built choice — but ASA is rigid, so if the part also has to flex, TPU is your only option and it will do the job.

### Does TPU filament need to be dried?

Yes, and a wet spool is almost always why a TPU print comes out stringy and rough. TPU pulls water out of the air quickly, and that water flashes to steam in the nozzle, producing popping sounds, whiskers between features, and a foamy surface. Drying the spool, typically 4–6 hours at about 50 °C, fixes it. If a dried spool still strings, the next most common causes are printing too fast and using retraction settings copied from a PLA profile, both of which make flexible filament buckle in the extruder rather than feed.

[Price a flexible part in seconds](https://x3dstudios.com/print)