The robotics part decision tree

CNC-machine these:

Joint housings, actuator brackets, gearbox enclosures. Need stiffness + dimensional precision + threaded interfaces — 3D printing won't hold up to repeated loading.
Bearing seats, shaft mounts, encoder holders. Tolerance to ±0.025 mm or tighter — beyond what FDM/SLA produces reliably.
Linear guide rails + carriages. Hardened steel ground to tight flatness — only achievable via grinding or hard milling.
Custom end-effectors (grippers, vacuum mounts). Repeated cycles + impact loads demand aluminum or steel, not plastic.

3D print these:

Mockup enclosures, cosmetic shells, cable guides
Wire routing channels, sensor mounting brackets (non-load-bearing)
Prototype gripper fingers (final version may need machining)
Custom mounts for off-the-shelf components

Sheet metal fab these:

Frame elements (CNC frames are overkill; bent + welded aluminum is 3× cheaper)
Wire shrouds, large cover panels, mounting plates
Brackets for electrical enclosures

Common robotics CAD mistakes

Over-tightening tolerances. ±0.005 mm everywhere adds 4× to cost. Tighten only the features that interface with bearings, shafts, or mating parts.
Designing for 5-axis when 3-axis works. Adding undercut features that force 5-axis machining can double cost. Sometimes splitting a part into two 3-axis machinable halves is cheaper.
Forgetting electrical considerations. Aluminum is conductive. If you need EMI shielding, specify it. If you need isolation, specify it.
Skipping the BOM material check. 6061-T6 vs 7075-T6 cost difference is small per part, but 7075 hardens faster and machines worse. Don't use 7075 unless you actually need the strength.

Sourcing for a 5-person team

Robotics startups usually don't have a procurement team. Make the supplier work for you:

Use shops with instant quoting so you can iterate on cost without emails.
Pick no-MOQ shops for v1/v2 so you're not stuck with bad parts in volume.
Build relationships with one or two shops that understand robotics — they'll catch DFM issues your generic shop won't (e.g. "this bearing seat would benefit from a relief groove for ease of installation").
Ask for sample inspection reports on your first order so you know the shop's real capability.

Ginwate has been a long-term supplier to several robotics OEMs including arms, AGVs, and humanoid platforms. See our robotics solutions or get a quote with your part.

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