Robot hardware is iterated in metal more than most products, because the thing being validated is rarely the shape — it is stiffness, backlash, mass at the end of an arm and whether the wiring still fits after the third revision. SkillsProto builds those parts in one plant in Shenzhen: CNC machining to ±0.005 mm on bearing bores and datum faces, 3-7 working day lead times, MOQ 1, plus sheet metal chassis, injection molded covers, vacuum cast batches from 10 to 500, and FRP shells for lightweight structures.
The parts robot teams send us
| Part | Process | Material we quote first | Notes that change the cost |
|---|---|---|---|
| Joint and motor brackets | CNC | 6061-T6, 7075-T6 where load is high | Bearing bore concentricity, bolt pattern to the gearbox face |
| End effector fingers and jaws | CNC or SLS / MJF | Aluminium, PA12, or PU cast resin | Grip surface texture, compliance, part-specific geometry |
| Structural frame plates | Sheet metal or CNC | 5052 / 6061 sheet, or machined plate | Flatness across the mounting face, hole pattern accuracy |
| Gearbox and reducer housings | CNC | 6061, sometimes 7075 | Bore alignment across two faces is the critical feature |
| Sensor and camera mounts | CNC or SLA | Aluminium or tough resin | Repeatable datum for calibration |
| Cable management and covers | Vacuum casting or injection molding | ABS-like PU, ABS, PC | 10-500 pieces without tooling, or aluminium tool from ~300 |
| Lightweight arm shells | FRP / carbon fibre | Carbon or glass layup | Stiffness-to-mass, 7-15 days for the first article |
| Base plates and risers | CNC | Aluminium or steel | Flatness and threaded hole accuracy |
Where the tolerance money goes on a robot part
Robots fail in dimension chains, not in single features. A bracket that holds ±0.005 mm on a bore but sits on a face that is 0.1 mm out of flat will still bind the bearing. So we recommend a short list of what to tighten:
1. Bearing and shaft bores — call the fit (H7/g6 or your own convention) and we machine and measure to it. This is where ±0.005 mm belongs.
2. Mating faces to gearboxes and rails — flatness and hole position, not general tolerance. A positional tolerance on the bolt pattern is worth more than a blanket ±0.02 mm.
3. Datum features used for calibration — if a camera mount is re-calibrated on every unit, its repeatable datum matters more than its cosmetic surface.
4. Everything else — leave at ISO 2768-m or ±0.05 mm. It is cheaper, faster, and does not change the test result.
Iterating fast: the three-revision pattern
Most robot parts go through three physical revisions, and the process choice should follow the revision, not stay fixed:
- Revision 1 — printed or machined single part in the real material, 2-7 days, to check fit and cable routing. If the design is genuinely unstable, print it: SLS PA12 in 2-4 days costs less than a machined part you will scrap.
- Revision 2 — machined with the corrected datums, 3-7 days, and this is the one that goes on the arm under load. One or two parts.
- Revision 3 — the repeatable build: 10-500 covers by vacuum casting, sheet metal frames with a proper hole pattern, machined brackets against a fixture so units interchange.
Because all seven processes are in one plant, revision 3 can mix processes in one BOM and one shipment rather than three suppliers and three freight bills.
Weight, and why FRP shows up on arms
Every gram at the end of an arm costs torque, battery and cycle time. Where a machined aluminium shell is over-specified for the load, an FRP or carbon fibre laminate off a machined or printed pattern gives the same envelope at a fraction of the mass. It is slower than CNC — 7-15 days for the first article — but for an arm segment or a mobile robot body panel it is often the difference between a 6 kg and a 3.5 kg system.
The two-week iteration loop
Robot teams that move fastest tend to run a two-week loop: send geometry on day one, get a quote with written DFM notes inside 24 business hours, receive machined parts in 3-7 working days, test them on the arm in the second week, and release a corrected revision immediately after. Because there is no allocation step between quoting and machining, the engineer who quoted the job is the one releasing it to the floor, so a mid-revision change does not go back through a broker. For urgent single parts a 48-hour expedite is available, and DDP transit to the UK, EU or US adds 3-5 days, so a full loop from drawing to tested part is realistically two to three weeks door to door.
What to send us
STEP or DWG geometry, a PDF drawing with the datums marked, quantity, material, finish, and one line on what the part has to survive — load, cycle count, temperature, or just a fit check. If there is a bought-in component in the assembly (gearbox, rail, encoder), its model helps more than its datasheet, because that is what we will machine against.
Frequently Asked Questions
How fast can you deliver a machined robot bracket?
CNC parts ship in 3-7 working days, with a 48-hour expedite for urgent single parts. Printed parts are 2-4 days. DDP transit to the UK, EU or US adds 3-5 days on top of the build time.
Can you hold bearing fits and bore alignment?
Yes. ±0.005 mm on critical CNC features, and we recommend calling the fit explicitly (for example H7) plus any positional tolerance on bolt patterns. Bore alignment across two faces is machined in one setup wherever the geometry allows, which is the reliable way to get it right.
What is the minimum order quantity?
MOQ is 1 piece on machined and printed parts. Vacuum casting covers 10-500 pieces without tooling, and injection molding from aluminium tooling becomes practical from a few hundred parts upward.
Can you build a full robot chassis, not just brackets?
Yes. A chassis BOM that mixes sheet metal panels, machined plates and moulded or vacuum cast covers is quoted as one package, built in one plant and shipped as one DDP consignment. This is usually cheaper and faster than splitting it across three suppliers.
Do you make the electronics or wiring?
No. We build the mechanical parts — brackets, frames, housings, covers and enclosures that carry the electronics. Send the PCB or connector model and we machine or mould the geometry around it.
Can you repeat a part months later to the same print?
Yes. We keep the geometry, the setup notes and the FAI report from the original order, so a reorder months later matches the approved first article. Say "repeat of previous order" in the RFQ and we will pull the file.
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