What is Shore hardness?

Shore hardness measures material flexibility on a scale. Shore A is for soft materials (rubber, TPU) where lower numbers = softer. Shore D is for harder materials. TPU 95A is the most common flexible filament — similar to a car tyre in hardness.

Can I print TPU on a Bowden printer?

TPU 95A and harder (98A) can work on Bowden setups if you print very slowly (10-15mm/s), use a short Bowden tube, and disable retraction. Softer TPUs (85A, 90A) generally require a direct drive extruder.

How does infill affect flexibility?

Lower infill makes flexible prints even more flexible. 10-20% infill with 2 walls gives maximum flex. 100% infill makes TPU prints nearly solid and much stiffer. The infill pattern also matters — gyroid and grid flex more evenly than lines.

What print settings work best for TPU?

Print at 20-30mm/s, 220-240°C nozzle, 50°C bed, no retraction or minimal (0.5-1mm at 25mm/s). Disable Z-hop. Use direct drive if possible. Print with 2-3 walls and 10-20% infill for best flexibility.

3DPrintCalcs

Flexibility Calculator — Shore Hardness & Flex Properties

Calculate shore hardness and flex properties for TPU and flexible filaments.

Material

Select the material type

Infill

Percentage value

Wall Thickness

Total thickness of outer walls

Part Width

Width measurement

Part Length

Length measurement

How We Calculate This

Flexibility Calculations

Effective modulus = Base flex modulus x Infill factor x Wall factor
Infill factor = 0.3 + (Infill% / 100) x 0.7
Deflection = Force x Length³ / (48 x Modulus x Moment of inertia)
Moment of inertia = Width x Thickness³ / 12

The deflection estimate uses simplified beam theory to predict how much a flat part will bend under a 1kg load. Lower modulus and thinner walls result in more deflection (more flexible).

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.