Urethane Casting

20-50 parts.
Silicone molds.
No tooling cost.

Q: How does urethane casting work?

1. Create master pattern via CNC or 3D print (SLA for best surface finish). 2. Embed master in silicone rubber — silicone cures around master. 3. Cut open silicone mold, remove master. 4. Close mold, inject urethane resin into cavity. 5. Cure urethane, open mold, remove part. 6. Clean mold, repeat for next part. Total cycle 1-4 hours per part depending on size and resin.

Q: Mold life and quantity limits?

Silicone molds typically produce 20-50 parts before degradation. Degradation factors: cumulative heat from exothermic urethane curing, parting line wear, release agent buildup. For larger quantities, multiple molds created from same master. Above 200 parts, rapid injection molding typically more economical.

Q: Dimensional accuracy vs injection molded?

Urethane casting: ±0.3% typical (so 100 mm part = ±0.3 mm). Injection molding: ±0.1% (so 100 mm = ±0.1 mm). Urethane has more shrinkage and less consistent dimensional control. For functional testing: adequate. For precision fit-critical applications: may require dimensional compensation in master, or may indicate CNC machining is better choice.

Q: Surface finish possible?

Surface finish from silicone mold replicates master surface. SLA master = Ra 2-5 µm smooth. CNC master = Ra 0.8 µm or polished. Secondary polishing of master enables very smooth urethane parts. For cosmetic parts, master pattern finish determines final part appearance.

Q: Cost comparison?

Master pattern: $50-200 (SLA master) or $200-1,000 (CNC master). Silicone mold: $200-1,500 depending on complexity. Each cast part: $15-80 depending on resin and size. Total for 25 parts: typically $2,000-8,000. Compare to: CNC 25 parts at $100-400/part = $2,500-10,000. Or: rapid injection mold $5,000-10,000 + $5-10/part = $5,125-10,250. Urethane often competitive for 10-50 part runs.

Q: Lead time?

Simple urethane casting program: master pattern 3-7 days + silicone mold 2-3 days + casting 25 parts 2-3 days = 2-3 weeks total. Complex parts: up to 4 weeks. Rush possible to 10-12 days. Compare to rapid injection molding which takes 4-6 weeks total for first parts.

Urethane casting for 20-50 part production runs. Silicone (RTV) rubber molds created from 3D printed or CNC master pattern. Urethane resins mimic ABS, PC, nylon, rubber elastomers. Perfect gap between 3D printed prototypes and injection molded production.

Urethane Casting Quote Rapid injection molding

20-50 parts Silicone molds ABS/PC/nylon equivalents 2-3 week delivery

01 · Urethane resins

Resin options by equivalent plastic.

Urethane resins are formulated to mimic the mechanical properties of common injection-molded thermoplastics. Choose based on the production material your final part will be made from.

ABS equivalent

Rigid · impact

Mimics ABS mechanical properties. Most common urethane for functional prototypes. White, black, or custom colors.

PC equivalent

Transparent · tough

Transparent polycarbonate-equivalent urethane. For clear prototypes needing high impact strength.

Nylon equivalent

Tough · wear

Mimics nylon 6/6 mechanical properties. For wear-prone or flexible parts.

Rubber 30-90A

Flexible · elastomeric

Silicone or TPU-like elastomeric urethanes. Shore A 30-90 hardness. Gaskets, seals, soft-touch parts.

Glass-filled

Rigid structural

Glass-filled urethanes for structural prototypes requiring higher modulus than unfilled.

Heat resistant

150 °C service

Higher-temperature urethanes for prototypes testing in elevated temperature applications.

Food grade

FDA compliant

Food-contact urethanes for food service prototypes.

Medical grade

USP Class VI

Biocompatible urethanes for non-implantable medical device prototypes.

02 · When urethane casting wins

Where urethane casting excels.

10-50 part runs

Sweet spot quantity — too many for CNC/3D printing, too few for injection tooling

Multiple material testing

Single silicone mold can cast multiple urethane resins — test properties without tooling changes

Rapid product launches

3D print master → silicone mold → 25 parts in 2 weeks. Get to market fast

Color testing

Easy to cast in different colors from same mold — no dye blending, direct resin coloring

Consumer product prototypes

Realistic cosmetic prototypes in production-like material for customer validation

Investor demo units

Professional-quality demo units for pitches, trade shows, customer meetings

Medical device prototypes

Pre-clinical samples in appropriate biocompatible resin

Overmolded prototypes

Multi-material parts (rigid + rubber) — difficult in injection molding at prototype scale

Low-volume production

End-use production for specialty or premium products with lifetime volumes < 500