Quality control, tolerances and inspection
Boyang Hardware inspects 100% of production parts before shipment, including full visual inspection against a documented standard inspection procedure, rather than sampling a batch. Inspection uses a 3D coordinate measuring machine, an optical projector, vernier calipers and height gauges. Every shipment is accompanied by a dimensional inspection report against the drawing and a material certificate for the heat or lot used. Achievable tolerance is 0.1 mm to 0.001 mm depending on feature and process.
Tolerance capability
The table below states what each process normally holds and what it can achieve when the part, material and fixturing allow it. Both columns describe production capability, not a guarantee for any specific drawing: on a real part the achievable tolerance depends on the feature, the material, the wall thickness and how many set-ups the part needs.
| Process | Normally held | Best achievable | Limited by |
|---|---|---|---|
| 3-axis CNC milling | ±0.02 mm | ±0.01 mm | Set-up count, tool deflection, fixturing rigidity |
| 4-axis CNC milling | ±0.01 mm | ±0.005 mm | Rotary axis accuracy; fewer set-ups improve it |
| 5-axis CNC machining | ±0.01 mm | ±0.005 mm | Tool reach and part rigidity, not the machine |
| CNC turning | ±0.01 mm | ±0.005 mm | Slender parts deflect; support is the constraint |
| Turn-mill combination | ±0.01 mm | ±0.005 mm | Feature position across the turned diameter |
| Grinding | ±0.005 mm | ±0.001 mm | Heat generation and wheel condition |
| Wire cut EDM | ±0.005 mm | ±0.002 mm | Wire diameter and spark gap |
| Die casting, as cast | ±0.05 mm | ±0.03 mm | Die wear, thermal contraction, draft |
| Injection moulding | ±0.05 mm | ±0.02 mm | Shrinkage variation and gate position |
| Metal stamping | ±0.10 mm | ±0.05 mm | Tool wear over the press run |
Inspection workflow
Inspection happens at five points, not one. The purpose is to catch a problem while it is still a process problem rather than a shipment of scrap.
- Incoming material check. Grade and dimensions are verified against the material certificate before the material enters production, so a substitution error at the mill is caught before it is machined into a part.
- First article inspection. For a new part or a changed drawing, the first part off the machine is measured in full against every dimensioned feature on the drawing. Nothing in the batch is run until the first article is accepted.
- In-process inspection. Critical dimensions are measured during the run at intervals set by the part, so tool wear is corrected during production rather than discovered at the end.
- Final 100% inspection. Every part is measured and visually inspected against the documented standard inspection procedure. Batch sampling is not used as a substitute for this step.
- Packing and documentation. Parts are packed to the agreed method and the inspection report, material certificate and any finish certificates are issued with the shipment.
Inspection equipment
| Equipment | Used for | Why not a caliper |
|---|---|---|
| 3D coordinate measuring machine (CMM) | Dimensional verification of complex geometry, true position, profile and features that are difficult to reach | A caliper measures distance between two accessible surfaces; a CMM measures position relative to defined datums |
| Optical projector | Profile comparison of small parts, radii, thread form and turned profiles | Non-contact, so it measures delicate or burr-sensitive edges without deflection |
| Vernier calipers | General linear dimensions, in-process and at final inspection | Fast; appropriate for general dimensions but not for specification-critical features |
| Height gauge | Datum-based height and step measurement on a surface plate | Establishes dimensions from a datum, which is how the drawing is dimensioned |
Documents supplied with a shipment
| Document | Supplied | Contents |
|---|---|---|
| Dimensional inspection report | Standard | Measured values against the dimensions specified on the drawing |
| Material certificate | Standard | Chemistry and mechanical values for the heat or lot used |
| First article inspection record | New parts | Full measurement of every dimensioned feature on the first accepted part |
| Finish certificates | Where applicable | Certificates for outsourced plating, anodising or heat treatment |
| Certificate of conformity | On request | Statement that the parts conform to the drawing and purchase order. State the requirement at quotation |
When something is out of tolerance
A part that fails inspection is not shipped and is not quietly mixed back into the batch. The sequence is:
- The part is quarantined and the affected production lot is identified by traceability back to the material lot.
- The deviation is measured and documented, so the actual size is known rather than the fact of failure.
- The deviation is communicated to the customer before a decision is made, with the measured values and the number of parts affected.
- Disposition is agreed in writing: accept as-is if the part is still functional, rework, or remake. Nothing is decided unilaterally.
- The cause is corrected — tool wear, fixture, programme or operator technique — and the correction is verified on the next parts before the run resumes.
Verification status of the claims on this page
Published here without qualification, because each item is directly observable or documented:
- Machine inventory — 54 machine tools, counted individually
- Inspection equipment — 3D CMM, projector, calipers, height gauges
- 100% inspection before shipment, against a documented standard inspection procedure
- Dimensional report and material certificate supplied with shipments
Handled differently:
- Certification (ISO 9001, RoHS). Recorded on the company's Made-in-China storefront. Certificate number and certification scope are provided on request with a quotation. The website states the certification name only where it can be evidenced, so the request route is given instead of a badge.
- Third-party inspection. Buyers may nominate an inspection agency. Confirm the requirement at quotation so it can be scheduled into the inspection plan rather than added after the parts are made.
If you need any claim above evidenced before placing an order, ask for it in writing and it will be supplied or corrected. Full verification record →
Questions about quality
Is inspection sampled or 100%?
100% of production parts are inspected before shipment, including 100% visual inspection against a documented standard inspection procedure. Sampling is used only for incoming material checks, where a mill certificate already provides lot-level evidence.
Do you provide a dimensional inspection report?
Yes, as standard with every shipment, showing measured values against the dimensions specified on the drawing. Material certificates are supplied at the same time.
Which dimensions end up on the inspection report?
Every dimension called out on the drawing where a report is required, plus the features identified as critical at quotation. If an assembly depends on a specific fit, mark that dimension and it is reported explicitly rather than left to a general note.
What happens if parts arrive out of specification?
Contact the company with photographs and measurements. The lot is traced through the material lot and inspection record, the cause is established, and disposition — rework, replacement or credit — is agreed. Parts that fail inspection at the factory are never shipped in the first place.
Can I place one of my own inspectors at the factory?
Buyer visits and inspection visits are accepted. Tell us the window when the order is placed so the schedule and access can be arranged.
Have a drawing with critical fits?
Mark the dimensions the assembly depends on. They come back with an achievable tolerance per feature and the inspection method for each.