TPU Filament Guide: Shore Hardness Explained
TPU is the most common flexible filament and the only one most printers will run without modification. The trick is that TPU is not one thing. The hardness number on the spool changes what you can use it for.
How Shore hardness works
Shore A is the scale for soft elastomers; Shore D is for harder plastics. The higher the number, the firmer the print. Anything 95A and below feels rubbery. 98A starts to feel like a stiff bumper. The D-scale TPUs feel like a flexible plastic, not a rubber.
The hardness range we stock
| Hardness | Feel | Typical use |
|---|---|---|
| TPU 85A | Soft rubber | Gaskets, soft grips, watch bands |
| TPU 90A | Soft, slightly firmer | Phone cases, wearables |
| TPU 95A | Medium flex (most common) | Wheels, straps, hinges, drone tyres |
| TPU 95A HF | High flow 95A | Faster prints, same flex |
| TPU 98A | Firm flex | Semi-rigid hinges, shoe inserts, bumpers |
| TPU 64D | Semi-rigid | Snap covers, living hinges |
| TPU 70D / 75D | Rigid | Tough functional parts with slight flex |
| Silk TPU 95A | 95A with silk finish | Decorative flex |
Print settings that work
- Slow your speed: 15 to 30 mm/s for soft TPUs, up to 40 to 60 mm/s for HF variants
- Low retraction: 0.5 to 2 mm typical for direct drive, often zero
- Direct drive extruder strongly preferred for soft TPUs; Bowden tubes buckle the filament
- Nozzle 220 to 240 C; bed 40 to 60 C with glue or PEI
- Print walls thicker (3+) for the right firmness on functional parts
- Dry the spool before printing; TPU absorbs moisture quickly