Key takeaways
- The Shore A scale measures how far an indenter sinks. The lower the number, the softer — 85A is clearly softer than 95A.
- A part's stiffness depends on its geometry as much as on its material.
- TPU 85A can't be printed on a Bowden machine. That's a hardware constraint, not a settings problem.
- A polyester or polyether base decides whether the part resists oil better or water better.
The question is almost always asked wrong. People ask "which one is softer" when the useful question is "how far must my part give under what force". Those produce different answers, because the softness of a printed part depends on its geometry at least as much as on its material.
What Shore A measures
A Shore test presses a standard metal indenter into the surface with a standard force and measures how far it sinks. The A scale is for soft materials, the D scale for hard ones. The lower the number, the deeper the indenter sinks, so the softer the material.
- 85A — close to a running-shoe sole or a fridge door seal. You can squeeze it with your fingers.
- 95A — close to a trolley wheel or a drive belt. You need to press hard to see it give.
- Above 60D — rigid plastic territory, no longer an elastomer.
The numbers, side by side
| TPU 95A (PolyFlex TPU95) | Nearest soft grade (PolyFlex TPU90) | |
|---|---|---|
| Shore hardness (ISO 7619-1) | 95 A | 90 A |
| Elongation at break (ISO 37) | 551 % | 592 % |
| Tensile strength (ISO 37) | not published | 30.1 MPa |
| Density (ISO 1183) | 1.20–1.24 g/cm³ | 1.12 g/cm³ |
| Tear strength, abrasion | not published | not published |
| Print speed | 15–35 mm/s | 10–20 mm/s |
| Extruder | Direct drive preferred | Direct drive required |
The most important row is the empty one. Tear strength is what decides how long a gasket lasts — it measures resistance to an existing tear spreading, not the force needed to snap an intact sample — and none of the manufacturers we checked publish it for 3D printing TPU. DIN abrasion is the same. If your part is a gasket that is fitted and removed often, or a wheel running on concrete, ask your supplier for both figures before ordering; if they don't have them, test on the part itself. For wheels, feet and anything that slides on a surface, 95A lasts noticeably longer.
The softer grade isn't the more durable one. With TPU, softer means it tears more easily and wears faster.
Why 85A is so hard to print
Filament in an extruder acts as a column under compression: the drive gear pushes from above, the nozzle resists below. A stiff material transmits the force down. A very soft one buckles in the gap between the drive gear and the nozzle's throat — like pushing a piece of string instead of a stick.
- Direct drive is mandatory for 85A, because the filament path has to be short and tight. A Bowden machine has a long tube, and 85A buckles inside it.
- Keep retraction small. Under 1 mm for 95A and close to zero for 85A. An elastic material stretches and springs back instead of retracting.
- Speed is a real limit. Not a surface-quality issue — exceed it and the print fails, because the filament buckles and jams.
Starting settings
- TPU 95A
- Nozzle 220–235 °C · bed 40–60 °C · fan 50 % · 15–35 mm/s · dry 60 °C / 6 h
- TPU 85A
- Nozzle 215–230 °C · bed 35–50 °C · fan 60 % · 10–20 mm/s · dry 55 °C / 6 h
The question few people ask: polyester or polyether base
TPU is a block copolymer of hard and soft segments. The soft segment can be a polyester or a polyether, and that choice decides the part's weak point more than the Shore number does.
- Polyester-based TPU resists oil, grease and abrasion better — suits parts in a machine shop.
- Polyether-based TPU resists water, humidity and mould better — suits parts that are submerged or used outdoors in damp conditions. In a tropical climate, that is worth weighing for long-lived parts.
Which one to choose
By the part
- Gaskets and seals fitted and removed often
- 95A — firmer, so edges tear less readily; tear strength isn't published, so test it
- Grips, feet, bumpers
- 95A — wears more slowly and prints twice as fast
- Cable strain relief
- 95A — needs moderate elasticity, not softness
- Soft-touch overmould, vibration damping
- 85A — the feel in the hand is the main requirement
- Prosthetic liners, wearable devices
- 85A — has to conform to the body
If you've never printed TPU, start with 95A and read the guide to printing TPU before buying an 85A spool. Full settings are on each grade's data sheet.
Frequently asked
What is Shore A hardness?
A hardness scale for elastomers: a standard metal indenter is pressed into the surface with a standard force, and the depth is converted to a number from 0 to 100. The lower the number, the softer. TPU 85A can be squeezed with your fingers; TPU 95A needs a firm press before it gives.
Can I use TPU 95A instead of TPU 85A?
Often, if you redesign rather than swap directly. Thinner walls and lower infill make a 95A part give as much as a more solid 85A part, while keeping twice the print speed. What you can't replace is the feel of the surface in the hand.
Why can't TPU 85A be printed on a Bowden printer?
Because soft filament buckles in the long tube between the extruder and the nozzle instead of transmitting the force — like pushing a piece of string. A direct-drive machine has a short, tight path that avoids this, which is why 85A lists direct drive as a hard requirement.
Does TPU need drying?
Yes. TPU absorbs a meaningful amount of moisture, and water in the melt causes bubbles, stringing and a pitted surface. Dry 95A at 60 °C for 6 hours and 85A at 55 °C for 6 hours. In a humid climate, a spool left open for a few days is enough to see the difference.
Can TPU be used outdoors?
Reasonably well, but mind the base. Polyether-based TPU resists water and mould better and suits damp outdoor parts; polyester-based resists oil and abrasion better but can hydrolyse when soaked in warm water for long periods. For parts in years of direct sun, ask which base it is before choosing.