Real materials. Real testing. Real validation.

Functional prototypes are built in real production materials so they behave like production parts — ABS injection plastic, aluminum CNC, steel machined. Display prototypes are usually 3D-printed PLA or PU cast — they look like the final product but don't have production material properties. Functional prototypes pass drop testing, survive thermal cycling, pass regulatory submission, and reveal real engineering issues.

CNC for metal parts, always — there's no 3D printing equivalent for real aluminum or steel mechanical behavior in most cases. CNC for plastic parts when you need specific material properties (PEEK, Ultem, PTFE). 3D printing (SLS or MJF nylon) is excellent for plastic functional prototypes — nylon PA12 parts behave very similarly to injection-molded nylon. MJF HP prints are production-grade for many nylon applications.

SLS and MJF nylon parts pass most drop tests comparable to injection-molded nylon — we've seen MJF PA12 parts survive 1.5m drops intact. SLA resin prints fail drop testing (brittle). FDM ABS prints fail at layer lines. For drop testing, specify SLS or MJF; avoid SLA and FDM.

If the part mates with production parts (screws, bearings, interface features), the mating tolerances matter. Default to ±0.1 mm on mating features, ±0.2–0.5 mm on cosmetic features. For precision mechanical (cam followers, bearing fits), ±0.025 mm on critical. For electrical enclosure parts, ±0.3 mm is usually adequate.

Depends on the regulatory agency and the device class. For FDA 510(k) submission, functional prototypes must be built using the same materials and processes as production (though possibly in lower quantity). UL testing can be performed on functional prototypes if they represent the production design. We provide material certificates and documentation for regulatory submission.

Engineering review: 3–10 parts. Internal testing (drop, thermal, vibration): 5–20 parts (multiple failure modes). Beta user testing: 50–200 parts. Regulatory submission: 10–50 parts typical. We scale the process to quantity — CNC for small batches, 3D printing for medium, rapid injection molding for 500+.