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

Infill

Wall Thickness

Part Width

Part Length

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.