Silicone mold. Aluminum tool. 10 vs 1000 parts.

Typical break-even: 100-300 parts depending on part complexity. Urethane: per-part cost dominated by labor (cast each part individually). Rapid injection: tool cost amortized over parts. At 50 parts: urethane clearly cheaper. At 200 parts: parity. At 500+ parts: rapid injection clearly cheaper. For quantities 100-300, quote both and decide based on material requirement (real plastic vs simulated).

Urethane: simulates mechanical properties of ABS, PC, nylon, etc. But it's urethane — different thermal behavior, different UV stability, different chemistry. For visual/mechanical validation: adequate. For: (1) hot-service testing, (2) long-term UV exposure, (3) specific plastic chemistry, (4) regulatory compliance (medical device, food contact) — real production plastic needed. Use rapid injection for those.

Urethane casting: design change means new master, new silicone mold. Master cost $200-2,000, mold $200-1,000. Relatively cheap to iterate. Timeline: 1-2 weeks per iteration. Rapid injection: design change means tool modification ($500-3,000 for minor changes, $5,000+ for major). Timeline: 2-3 weeks per iteration. For rapid iteration with multiple design changes: urethane is faster and cheaper.

Common: start with urethane casting for 20 parts (functional validation), transition to rapid injection once design freezes (next 2,000 parts), eventually to steel tooling if volume justifies. Each step validates before bigger investment. We support this progression — same customer relationship through all stages. Risk reduction at each stage.

Urethane: some part-to-part variation from manual casting. Color consistency typically within 5-10% across mold. Dimensional variation ±0.3% typical. Rapid injection: excellent consistency from automated process. Color uniform, dimensions ±0.1% typical. For demos and marketing photos, urethane is adequate. For consistent functional testing or customer-facing production: rapid injection.

All standard thermoplastics: ABS, PC, PP, PE, nylon, POM, PEEK, Ultem, PPS, TPE, TPU. Aluminum tool handles plastic melt temperatures from 180°C (LDPE) to 400°C (PEEK). Glass-filled and abrasive resins wear aluminum tool faster (3,000-8,000 shots vs 20,000 unfilled). For most plastic materials, rapid injection matches properties customer would see in production.