A machine list shows available resources, not whether a supplier can repeatedly deliver the functional relationships on a robot-part drawing. Unit price and one successful sample are also incomplete evidence.
Use a representative drawing to evaluate technical understanding, then review the planned datum chain, fixture, measurement, outside processes, change control and transition to production.
Supplier risks and evidence
| Risk | Underlying gap | Evidence to request |
|---|---|---|
| First article passes, production varies | No repeatability validation | Process route, first-article report and pilot data |
| Low price creates rework | Datum, treatment or inspection omitted | Quotation assumptions, DFM and risk list |
| Old revision is produced | Weak change control | Revision receipt, withdrawal and reapproval records |
Test understanding of functional requirements
A capable supplier asks about assembly datums, material state, geometric tolerances, treatment and critical features. A representative drawing should prompt specific questions about thin walls, deep pockets, coaxial bores or finishing allowance.
Expect DFM with reasons and boundaries
Useful DFM explains the effect on access, clamping, measurement or cost and separates mandatory changes from optional improvements. Features that cannot change need a credible process and verification plan.
Review real fixtures, datum strategy, inspection evidence and change control rather than equipment lists alone.
Review fixtures and process repeatability
Inspect soft jaws, locating elements, setup transfer, rough/finish separation, tool-life rules and first-piece approval on similar work. Ask how the process survives operator, machine and shift changes.
Match measurement to the tolerance
Owning a CMM does not prove every feature is measurable. Review program, fixture, environment, uncertainty and traceability, plus optical, form or scanning capability for micro holes, thin walls and freeform surfaces.
Validate outside processes and production launch
Heat treatment, coating, grinding and special tests remain part of the supplier's responsibility. Before release, confirm approved subcontractors, incoming/outgoing checks, material source, capacity, tooling, sampling and packaging through a pilot lot.
Capability is demonstrated by a traceable chain from material and process planning to inspection and pilot production.
Summary
Select a robot machining supplier through demonstrated process understanding and evidence, not machines or price alone. A real drawing, first-article package and pilot lot reveal whether the complete chain is repeatable.
FAQ
Does owning a five-axis machine prove strong capability?
No. Programming, fixtures, measurement, people and repeatable data on similar parts are also required.
Is the lowest quotation always the highest risk?
No, but confirm whether the saving comes from a better process or from omitted operations and quality requirements.
Is pilot production needed after a good sample?
Yes for most critical work. A pilot exposes tool-life, cycle, measurement and subcontractor variation that one sample cannot.
Ready to get a quote for your CNC machined parts?
Submit your engineering drawings to qiancj@oemach.com. We support prototype sampling and small-batch production with strict tolerance control.