SLA Resin · Industrial 3D Printing

Flexible 50A Resin

A soft, translucent SLA elastomer at 50A Shore durometer, for prototyping parts normally made from soft rubbers and silicones. Parts bend, stretch, and compress through repeated cycles without tearing, and spring back quickly.

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55A

Shore Hardness

Soft, squeezable feel

160%

Elongation at Break

Stretches without tearing

3.1%

Compression Set

At 70 °C, recovers its shape

12.3 kN/m

Tear Strength

Holds up to repeated cycles

Real Flexible 50A Parts

Actual Formlabs SLA prints in Flexible 50A Resin, not renders.

Group of soft translucent parts printed in Formlabs Flexible 50A Resin, including a hand model, an anatomical heart, a lattice cube, an insole form, a mask and coral models, on a blue background — Anatomical models, wearable forms and lattices printed in Flexible 50A.

Soft translucent ribbed bellows parts printed in Formlabs Flexible 50A Resin on a dark surface — Ribbed bellows parts in the translucent as-printed finish.

Summary & Key Takeaways

Genuinely Soft: 55A Shore hardness, the softest material we print, in the range of soft rubbers and silicones.
Recovers Its Shape: A 3.1% compression set at 70 °C, so parts do not stay squashed after sustained compression.
Translucent: Prints translucent, which suits soft tissue anatomy and medical models where internal features must show.
Softness Costs Strength: 3.4 MPa tensile strength and 12.3 kN/m tear strength; choose Flexible 80A V2 when parts must resist tearing.

Compare Flexible 50A to Other 3D Printing Materials

A quick, scannable comparison against the other flexible materials we print. All values are shown at once; use the buttons to focus on one comparison at a time.

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Shore hardness, tensile strength, elongation at break, and tear strength for Flexible 50A Resin versus Flexible 80A Resin V2 and SLS TPU 90A.
Property	Flexible 50A	Flexible 80A V2	TPU 90A SLS
Shore hardness	55A	83A	90A
Tensile strength	3.4 MPa	10 MPa	8.7 MPa
Elongation at break	160%	230%	310%
Tear strength	12.3 kN/m	28 kN/m	See TDS
Support structures	Removable supports for overhangs	Removable supports for overhangs	None required

Why Choose Flexible 50A Resin?

The softest material we print, and the closest thing to a cast silicone that comes off a printer.

Silicone-Like Softness

At 55A Shore hardness, parts squeeze and conform the way soft rubber and silicone do, which makes it the right choice for wearables, soft-touch buttons, and anything that contacts the body.

Recovers After Compression

A 3.1% compression set at 70 °C means parts return close to their original thickness after being held compressed, so seals and pads used in prototypes keep working across repeated test cycles.

Translucent for Anatomical Models

The translucent finish lets internal channels and embedded features read through the wall, which is why it is a common choice for soft tissue anatomy and surgical rehearsal models.

Flexible 50A Design Rules (DFM) at a Glance

Formlabs SLA design guidelines for Form 3 and Form 4 generation printers, adjusted for elastomers. Check your CAD feature dimensions against these limits before uploading your file.

Min. wall thickness (supported · unsupported)	1.5 mm for both
Min. embossed detail	0.2 mm
Min. engraved detail (width & depth)	0.3 mm
Min. hole diameter	1.0 mm
Min. drain hole diameter	2.5 mm
Clearance between separate or moving parts	0.5 mm min
Max. unsupported overhang	5.0 mm · 10° min. angle from level
Max. single-part build size	353 × 196 × 350 mm

Branching vascular model with thin translucent branches printed in Formlabs Flexible 50A Resin — A branching vascular model. Thin unsupported branches are the hardest case for the minimums here.

Source: Formlabs SLA design specifications for Form 3 / Form 4 generation printers, adapted to hold walls to a higher minimum than Formlabs' published figures. Flexible 50A is the softest material we print, so it is the least tolerant of thin features: walls below the minimum tear during support removal, and unsupported spans sag under their own weight. Back thin membranes with a thicker frame wherever the geometry allows. These are general guidelines; cross-section, hole depth, and part geometry can shift the safe minimums for a specific design. Maximum build size reflects our largest-format SLA printer; actual build size depends on which machine your order routes to.

Frequently Asked Questions

Everything you need to know about designing, ordering, and using Flexible 50A parts on Form Now.

What is Flexible 50A Resin?

Flexible 50A Resin is a soft, translucent stereolithography (SLA) elastomer from Formlabs with a 50A Shore durometer, intended for prototyping parts normally produced with softer rubbers and silicones. Parts bend, stretch, and compress through repeated cycles without tearing and spring back quickly to their original shape.

How soft is Flexible 50A Resin?

Flexible 50A Resin measures 55A on the Shore A hardness scale, making it the softest material we print. For comparison, Flexible 80A Resin V2 is 83A and SLS TPU 90A is 90A, both noticeably firmer.

What is Flexible 50A Resin used for?

Flexible 50A Resin is commonly used for wearables and straps, compressible buttons, soft tissue anatomy and medical models, soft-touch grips, and prototypes of parts that would be cast in silicone or soft rubber.

Should I choose Flexible 50A or Flexible 80A V2?

Choose Flexible 50A when the part must be genuinely soft and squeezable at 55A Shore hardness. Choose Flexible 80A V2 when it needs to be firmer and much more tear resistant: 83A Shore hardness, 28 kN/m tear strength against 12.3 kN/m, and 10 MPa tensile strength against 3.4 MPa.

Does Flexible 50A stay compressed after being squeezed?

No. Its compression set at 70 °C is 3.1%, so parts recover close to their original thickness after sustained compression, which is what lets prototype seals and pads survive repeated test cycles.

What are the minimum wall thickness design rules for Flexible 50A?

We recommend a minimum wall thickness of 1.5 mm for elastomeric resins, higher than the 1.0 mm we hold rigid resins to, because thin elastomer walls tear and distort during support removal. Holes should be at least 1.0 mm in diameter. Maximum single-part build size is 353 x 196 x 350 mm.