Choose a material for flexible parts

Flexible parts include gaskets, seals, phone cases, grips, bumpers, hinges and wearable straps. They have to bend, stretch or squash, then return to shape thousands of times. Choosing one is mostly about matching softness and stretch to the job.

What fails in flexible parts

• Tearing starts at sharp corners, thin edges and holes.
• Compression set means a seal squashed for a long time stops springing back, and starts to leak.
• Layer splitting happens in FFF parts flexed across layer lines.
• Wrong hardness. A gasket that is too hard will not seal. A grip that is too soft feels vague and wears fast.

Which properties matter

Shore hardness is the main number. It measures how far a standard indenter sinks into the surface. Soft rubbers use the Shore A scale; harder plastics use Shore D. A higher number means harder, but only within the same scale. Our guide to Shore A vs Shore D explains how they overlap.

Elongation at break tells you how far the material stretches before it snaps. For seals and hinges, more stretch usually means more forgiveness. Tensile strength matters for straps and parts that are pulled. A low Young’s modulus means a part feels soft and bends easily.

Material families that usually work

• TPU is the workhorse flexible filament. It is tough, abrasion-resistant and comes in a wide range of hardnesses.
• Other TPEs and soft blends can go softer than TPU but are harder to print.
• PP is not rubbery, but it is the classic choice for living hinges because it survives repeated folding.
• Elastomeric resins give fine detail and smooth surfaces for seals, soft-touch prototypes and models.
• Flexible powders such as TPU for SLS or MJF make lattices and complex soft parts with no supports.

Process considerations

In our catalog there are 25 flexible filaments, 31 flexible resins and 8 flexible powders.

1. Filamen 2415–2,000
2. Resin 3035–391
3. Serbuk 8280–440

Bar = terendah hingga tertinggi, titik = median. 62 bahan, terus daripada pangkalan data kami. Skala log.

FFF is cheap and tough, but soft filaments need a direct-drive extruder and slow speeds. Resin gives the best surface and detail, though elastomeric resins usually tear more easily than TPU. Powder gives isotropic, durable parts and is ideal for lattices that tune softness through geometry.

Design and post-processing tips

• Round every corner. Fillets stop tears from starting.
• Use geometry to tune softness. Infill density, wall count and lattices change how soft a part feels as much as the material does.
• Orient flex lines along layers in FFF so bending does not pull layers apart. See print orientation.
• Dry your TPU. Wet filament strings and prints weak parts.
• Post-cure elastomeric resins as specified. Under-cured parts stay tacky and weak.

A shortlist from our data

We flag 69 materials as flexible. These stretch the furthest before breaking:

When you compare hardness, check the scale letter on each value. A Shore D value is much harder than the same number on Shore A.

Common mistakes

• Comparing Shore A and Shore D numbers directly.
• Picking by elongation alone. A very stretchy material can still tear easily at a notch.
• Printing soft TPU on a Bowden setup at full speed.
• Ignoring compression set for seals that stay squashed.

See all flexible materials