Evaluating Evidence from a CNC Machining Supplier
This guide is for buyers, supplier quality engineers and engineering leads deciding whether a CNC supplier is who and what it says it is.
Websites, brochures and trade profiles all make claims. The sections below separate claims from evidence, explain what each kind of evidence can and cannot show, and suggest a verification sequence scaled to the risk of the part.
Claims and Evidence Are Different Things
Supplier information falls into a few kinds of claim: who the company is, where it manufactures, what resources it has, which work it performs itself, how it controls quality and what it has made before. Each claim fits in a sentence. Evidence is something you can check independently or watch happen, that is specific to the claim and recent enough to rely on.
Most evaluation errors come from accepting evidence for one claim as proof of another. A factory photo shows a building, not that your part will be made there. A machine list shows stated resources, not the tolerance a finished part will hold. A certificate shows that a management system was audited for a defined scope at a defined site, not that every process or location is covered. Match each piece of evidence to the claim it can support.
Related: About mgz
What Each Kind of Evidence Can and Cannot Show
Read the table as a map from evidence to the claim it supports. No single row verifies a supplier; several rows together, consistent with one another, begin to. An inconsistency between rows, such as a different company name on the certificate and the invoice, is itself one of the most useful findings an evaluation can produce.
| Evidence | What it can verify | What it does not verify |
|---|---|---|
| Business registration record | Legal entity, registered address and status | Manufacturing ability or the actual production site |
| Photos and recorded video | That a site and equipment exist somewhere | Location, ownership, or that the footage is current |
| Live video walk-through | A site operating now, steered by your requests | Process control or the records behind the work |
| Equipment list | Stated resources to compare with your part | Tolerances, capacity or which machine runs your part |
| Management system certificate | An audited system for a stated scope and site | Every process, site or subcontractor |
| Redacted document samples | The format and fields you would receive | That your order will receive the same |
| Trial order with full records | Conformance of real parts to your drawing | Consistency across later batches |
Related: Factory and production
Confirming the Legal Entity Behind the Quote
Start with the entity you will contract with and pay. In many countries a public business register can be searched by name or registration number; in China, for example, company registration details can be checked on the national enterprise credit information system. The aim is simple: the same entity should appear on the quote, the contract, the invoice, the certificates and the payment details.
the registered name and registration number match across quote, contract and invoice.
the registered address and the production address are both stated, and any difference is explained.
the relationship between a brand or website name and the legal entity is stated.
certificates name the same entity and cover the production address.
the beneficiary name matches the contracting entity.
Related: About mgz
Trading companies
a sales company in front of a factory is common and not a problem in itself. Ask which entity manufactures, which one contracts and who is responsible for conformance.
Checking the Site Through the Work, Not the Building
A live video walk-through is a low-cost way to check a site, provided you steer it.
Workpieces with visible identification say more about a site than a wide view of idle machines.
Ask to start at the entrance or signage and walk continuously to the production area rather than cutting between rooms. Ask to see machines running with workpieces and their identification visible. Then request something unscripted: a specific record from the inspection area, the underside of a part, or the material store.
Look for consistency with the other evidence. Equipment in view should resemble the equipment list, workpieces should resemble the part families the supplier describes, and the inspection area should fit the measuring methods quoted. Where the part or the program carries higher risk, a site audit by your own team or a third party adds what video cannot, such as time with the people who plan and inspect the work.
Related: Factory and production
Manufacturing Scope: In-House, Subcontracted and Your Part
Few machining suppliers perform every operation themselves. Heat treatment, plating, anodizing, painting and some inspection are commonly subcontracted, and that is normal. What a buyer needs is the boundary: for this part, which operations happen at the site you checked, which are sent out and to whom, and who is responsible for the result and the records of each.
Ask for the proposed route for your part rather than a general capability list. A credible answer names the operations in sequence, the site or subcontractor for each, and how parts and records come back. Check whether certificates you were shown also cover the subcontracted work, and agree whether a change of subcontractor needs your notice. A blanket 'all processes in-house' deserves the same follow-up questions as any other claim.
Related: Quality and inspection
Document Samples, Certificates and Trial Orders
Documents show how a supplier works when nobody is watching. Ask for redacted samples of the records you would receive and read them as you would read your own: fields, revision references, measured values and signatures. Then check any certificate at its source, through the issuing body or the accreditation body behind it, rather than relying on a PDF someone sent you.
Inspection report sample: part, revision, characteristic, method, result and coverage fields present.
Material record sample: heat or lot number, specification, condition and results, with the issuer visible.
Certificate check: holder name, site address, scope, issuing body and validity confirmed at the source.
Trial order: a small order on a real drawing with the full records you would require later.
References: past work shown with permission, with the work actually performed stated.
Redaction done well
samples are usually redacted to protect other customers. One that removes names but keeps fields and values intact gives you more to check than a blank template.
A Verification Sequence Scaled to Risk
Verification costs time on both sides, so scale it to the part.
Each stage adds evidence, and the approval records the scope actually checked — concept illustration
A simple bracket for an internal fixture may justify a desk review and a trial order. A part that decides the function of an RF assembly, or sits in a regulated program, may justify every step including a site audit. Either way, record what was checked and the scope the approval covers.
Approval should name what it covers: the entity, the site, the operations and the part families checked. A supplier approved for simple brackets has not been verified for cavity housings with plated contact faces, and a later order outside that scope deserves its own review rather than an assumption carried over from the first one.
Related: Manufacturing cases · Case template: drawing requirement to inspection acceptance
- 01Desk review
entity, consistency of names and addresses, certificate check.
- 02Live walk-through
site, equipment and work in progress, steered by your requests.
- 03Document review
redacted samples and the route proposed for your part.
- 04Trial order
real parts and full records against your drawing.
- 05Site audit, where justified
processes, records and people, in person.
Related Pages
Continue with the closest related part family or guide.
Waveguide Drawing Requirements and Tolerances
Which waveguide features, datums, finish conditions and acceptance checks to define on the drawing before a machining quote.
Specifying Surface Roughness on Machined Parts
Choosing the roughness parameter, placing callouts on functional surfaces, stating the condition and checking the result on received parts.
Surface Finishing and Dimensional Requirements
How finishes change size, how to state before- or after-finish dimensions, threads and masking, and which records show the finished condition.
Supplier Evidence Questions
Is a verified badge on a trade platform enough?
Treat it as a starting point and find out what the platform actually checked. Some badges reflect a business registration check, some an on-site visit by a third party, some little more than a paid membership. Read the verification report if one exists, and still confirm the entity, the site and the scope yourself.
How can we tell whether factory photos are current and genuine?
Photos on their own rarely settle it. Look for consistency between photos, the equipment list and a live walk-through, and ask for a specific new image, such as a named workpiece beside its current job card or a particular machine from a stated angle. Footage you steer in real time is much harder to borrow than a gallery.
Can we ask a supplier for customer references?
Yes, but expect limits. Many customers do not allow their names to be shared, and an honest supplier will say so rather than show logos without permission. Ask instead for anonymized examples described by part family, material, features, and the work and records the supplier actually produced.
What should we send for a trial order?
A real drawing at a released revision, a quantity large enough to show the route, and the records you would require on production orders. Agree confidentiality and the file exchange method first, and state the acceptance criteria in advance, so the trial tests the supplier against the same expectations as a later order.
Discuss Your Supplier Evaluation
Tell us which evidence your evaluation requires, such as entity details, a site review, document samples or a trial order on a real drawing.
Sales contact (pending)
Name, role and photo to be confirmed
Drawings are optional for an initial discussion.
Start with the information you have; file exchange can be arranged afterward.
Name to be confirmed
Sales, company name to be confirmed
- The information and arrangements available can then be confirmed for your request.
Project Inquiry
Fields marked are required.