Documentation for Machined Parts: Drawings, Certs and Reports
Short answer: a well-documented machined order includes a controlled drawing, a material certificate that traces the raw stock, an inspection report covering the key dimensions, and a certificate of conformity. Regulated industries add a first article inspection report (FAI) and, where required, PPAP. Buyers should ask which documents ship by default and which cost extra, because "we can provide anything" usually means nothing is standard.
Documentation is the part of a machined order that nobody notices until it is missing. When a part fails in the field, when an auditor asks for traceability, or when a customer's quality system demands records, the drawing and certificates are what stand between you and an unanswerable question. Here is what each document is, when you actually need it, and how to build the request into your RFQ so nothing gets bolted on later.
What Machined Part Documentation Actually Covers
Documentation falls into three families. The first is the design definition: the drawing and 3D model that say what the part is. The second is material and process evidence: the certificates that prove the raw material and treatments are what you specified. The third is verification evidence: the inspection reports and conformance statements that prove the finished parts meet the drawing.
A mature supplier controls all three and can retrieve them later. A weaker supplier sends parts with a packing slip and calls that documentation. The difference shows up years later, when you need to prove a part was made from certified material and no one can find the record.
The Core Documents for a Machined Order
| Document | Purpose | Typical default? |
|---|---|---|
| 2D drawing / 3D model | Defines geometry, tolerance, finish | Always, customer-supplied |
| Material certificate (EN 10204 3.1) | Traces the metal to heat/lot with test results | Usually on request |
| Certificate of conformity (CoC) | Supplier declares parts meet spec | Often default |
| Dimensional inspection report | Records measured key dimensions | Default at good shops |
| First article inspection (FAI) | Full verification of a first part | On request |
| PPAP package | Full production-part approval, 18 elements | Automotive, on request |
| RoHS / REACH declaration | Confirms restricted substances | On request |
The pattern to notice: the drawing is yours, the inspection report is the shop's basic proof, and everything else is a request you should make deliberately rather than assume.
Drawings: What a Machined Part Drawing Must Show
A drawing that a factory can quote and inspect from is a specific thing. It shows the part geometry with a consistent unit (state mm or inches, do not mix), a defined tolerance scheme, and callouts for every dimension that matters.
Two tolerance systems are common. A general tolerance block such as ISO 2768-mK covers dimensions without individual callouts, and the block tells the shop how much variation is acceptable by default. Individual callouts, and geometric dimensioning and tolerancing (GD&T) symbols, override that block for critical features. If you do not specify a general tolerance, the shop has to assume the tightest reasonable interpretation and price accordingly, which raises your cost for no reason.
The drawing should also carry the material spec, surface finish callouts and any notes on burrs, edges and heat treatment. Revision control matters as much as content: a drawing without a revision number cannot be controlled, and an outdated revision is a common source of wrong parts. Our CNC machining tolerances guide covers how to call out tolerances cleanly, and the RFQ quote guide shows how a complete drawing speeds up quoting.
Material Certificates and Traceability
A material certificate is the paper trail from your part back to the metal it was made from. The most trusted format is EN 10204 3.1, which includes actual test results from the casting or mill heat, witnessed by an independent party. A 2.2 certificate is a non-specific declaration without test results, and a 2.1 certificate is simply a statement of compliance from the manufacturer.
| Certificate type | What it contains | When to require |
|---|---|---|
| EN 10204 3.1 | Heat-specific test results | Pressure, safety or regulated parts |
| EN 10204 2.2 | Non-specific, based on internal tests | General commercial confidence |
| EN 10204 2.1 | Statement of compliance only | Low-risk, non-critical parts |
| Mill test report (MTR) | Chemistry and mechanical properties | Material verification generally |
Why does this matter? Because material mix-ups are real. A substitution from 304 to 303 stainless, or from a certified alloy to a cheaper grade, machines fine and fails in service. A 3.1 certificate ties every part batch to a specific heat of metal with recorded chemistry and mechanical properties. For critical parts, insist on it and keep it. Our article on material certificates for CNC parts goes deeper on how to read one.
Inspection Reports, FAI and PPAP
A dimensional inspection report records the measured values of the key dimensions against the drawing, usually with the nominal, the tolerance and the actual reading. At a good shop this ships with each batch by default. It is the single most useful document for confidence, because it shows what was actually checked rather than promising that something was.
A First Article Inspection report is more thorough. It verifies every dimension and note on the drawing on the first part produced, and it is signed as evidence that the process can make the part correctly before volume runs begin. If a dimension is out of tolerance on the FAI, you find out before you have a thousand parts, not after.
PPAP, or Production Part Approval Process, is the automotive-style package with eighteen elements including process flow, PFMEA, control plan and measurement system analysis. It is heavy and expensive but sometimes unavoidable. Ask yourself honestly whether your program needs it, because many buyers request PPAP out of habit and pay for paperwork that adds no value to their application. Our CMM inspection guide explains the measurement that backs these reports.
Why Documentation Costs Money, and Where to Save
Documentation is not free. A 3.1 material certificate requires buying certified stock and preserving the heat number through machining. An FAI consumes inspection hours before production starts. PPAP can take days of engineering time. Each of these is real labour, and a supplier that offers them all at no charge is either eating the cost or not actually doing them.
The honest approach is to match the paperwork to the risk. A non-critical bracket for an internal prototype needs a drawing and a basic inspection report, nothing more. A safety part in a machine under load needs a 3.1 certificate and an FAI. A production automotive part needs PPAP. Paying for a full PPAP package on a low-risk part is waste; skipping a 3.1 certificate on a pressure part is negligence. Decide by consequence of failure, then tell the supplier exactly what you need.
Documentation and the RFQ: What to Send and What to Request
Build the documentation list into your RFQ so it is priced from the start, not added as a surprise. State which standard the drawing follows, whether you need a 3.1 material certificate, whether you need an FAI, and whether you need a certificate of conformity with each shipment. If your industry demands PPAP or a specific declaration such as RoHS or REACH, say so.
Then confirm what ships by default. A supplier that includes a dimensional inspection report with every batch is giving you real value, because it means the parts were measured and the data is documented. A supplier that cannot produce that report on request is telling you something about its process control.
At BQUQ we control drawings by revision, manage material traceability, and ship each batch with a dimensional inspection report as standard. Higher-level documents such as 3.1 certificates, FAI reports and PPAP are available on request and quoted up front. Send your drawing with a note on the documentation your quality system requires, and we will reply within 12 working hours with the capability and the paperwork path.
Frequently Asked Questions
Q: What documents should come with a machined parts shipment?
A: At minimum a dimensional inspection report covering key features, plus a packing list. Many buyers also require a certificate of conformity and a material certificate. Regulated industries add a first article inspection or PPAP package.
Q: What is the difference between a 3.1 and a 2.2 material certificate?
A: An EN 10204 3.1 certificate includes heat-specific test results with independent verification, while a 2.2 certificate is a non-specific declaration based on internal testing without those results. Critical or regulated parts should use 3.1.
Q: Do I need a first article inspection report?
A: If your part has critical features or you are placing a volume order, yes. An FAI verifies every dimension on the first part before production ramps, catching a process problem before it becomes a batch of scrap.
Q: Is a certificate of conformity the same as an inspection report?
A: No. A certificate of conformity is a declaration that the parts meet the specification, while an inspection report records actual measured values against the drawing. The report is stronger evidence because it shows the data.
Q: Can you provide PPAP documentation?
A: Yes, on request, including the standard elements such as process flow, control plan and measurement system analysis. PPAP is heavy, so we confirm scope and cost up front rather than assuming it is needed.
Related Resources
- Material Certificates for CNC Parts: How to Read Them — 3.1 versus 2.2 and what traceability really means.
- CNC machining services — parts machined, inspected and documented to your quality system.
- About BQUQ — ISO9001 source factory in Dongguan with four production lines under one roof.
- Contact — send your drawing and documentation requirements for a quote within 12 hours.
Authored by the BQUQ Engineering Team. BQUQ is an ISO9001-certified source factory in Dongguan, China, running CNC machining, metal stamping, custom springs, heat sink and collet lines under one roof. Send drawings to sc@bquq.com or WhatsApp +86 13713157787 for a quote within 12 working hours. www.bquq.com
