First Article Inspection (FAI): What to Check Before Mass Production

First article inspection is the cheapest quality gate in manufacturing. Here is what a proper FAI should include — full dimensions, material, surface and appearance, function and assembly, and the gauges that do the checking — how to run it, and why it so often fails.

Why FAI Matters

First article inspection (FAI) is the practice of taking the first part produced after setup — or after any significant change — and checking it thoroughly against the drawing before the rest of the run is made. It is the cheapest quality gate in manufacturing, because a problem found on part one costs a setup adjustment, while the same problem found at final inspection costs an entire batch.

FAI answers a specific question: is this process, with these tools and this program, capable of making a conforming part? If the answer is yes, and it is documented, the following parts can be judged by sampling, and that sampling has a known baseline to compare against. If the answer is unclear, or the FAI is skipped, the entire run rests on an assumption — that the first parts are probably fine.

It matters most where mistakes are expensive to fix: castings with investment in tooling, machined parts with tight tolerances and dedicated fixtures, and assemblies where several components must fit together. It also matters whenever something changes — a new supplier, a new machine, a revised drawing or a fresh lot of material.

What FAI Should Check

A thorough FAI is more than a dimensional check. It confirms that the part is right in every way the drawing and purchase order require. The five areas below are the ones that catch the most problems, and together they form the backbone of any serious first-off review.

1. Full Dimensional Report

Every dimension, tolerance and geometric requirement on the drawing should be measured and reported on a ballooned drawing — the drawing marked up with numbered balloons that match the numbered lines of the report. Key and critical characteristics should be measured on the actual production part, not on a sample prepared for the occasion, and the report should show the nominal, the tolerance, the measured value and the instrument used.

2. Material Certification

Confirm the material is what the drawing specifies. That means a material certificate issued to EN 10204 3.1 where required, checked against the specification, and supported by chemical verification such as PMI where the part is critical. The heat or lot numbers on the certificate should match the marks on the part and the paperwork that travels with it.

3. Surface and Appearance

Check surface finish against the specified Ra value, look for casting or forging defects that the acceptance standard either allows or rejects, and confirm that coating, plating or paint meets the requirement. Appearance defects that matter functionally — porosity on a sealing face, a crack at a stress riser — belong on the FAI report, not hidden behind a quick 'looks fine'.

4. Function and Assembly

Where the part has a function, test it. Gauges, threads, fits and interfaces should be checked against the mating part wherever possible, so that you find out at part one whether it assembles, rather than at the customer. Any functional test specified by the drawing or the purchase order should be performed and recorded, with the result going onto the report alongside the dimensional data.

5. Fixture and Gauge Verification

The instruments and fixtures used to check the part are part of the FAI too. Confirm that gauges and measuring instruments carry valid calibration, that fixtures and check gauges are themselves verified, and that the CNC program and its revision match the drawing revision. A perfect part measured with a wrong gauge is not evidence — it is a false pass.

How to Run and Sign Off an FAI

Set the expectation before production. The purchase order or a quality plan should state that no mass production begins until the first article is approved in writing. The supplier produces the first part, or a small first-off sample, measures it fully, and submits a report together with the ballooned drawing, the material certificate and any test results.

You, or an independent inspector on site, then review the submission. Check that every balloon has a measured value, that values fall inside tolerance, that the instruments used were calibrated, and that nothing has been left blank or marked 'see sample'. Where you cannot verify remotely, arrange for the review to happen at the factory before the line restarts — our guide to quality control and inspection in China covers how that is arranged.

Approval should be written and specific: it approves the part, the process, the drawing revision and the tooling it was made with. If any of those changes later, the approval lapses and a new FAI is required. A first article approval that is verbal, or that names the supplier but not the revision, is worth little when a dispute arises. A supplier that understands this discipline is easier to run; see our guide to supplier audits in China for how to check that competence before you order.

Common Reasons FAI Fails

When an FAI is rejected, the cause is usually one of a handful of recurring mistakes. Watch for these on the next submission.

• The drawing was ballooned incompletely, leaving dimensions unreported.
• Measurements were taken with instruments that are out of calibration or too coarse for the tolerance.
• A golden sample was prepared specially, not taken from the actual production run.
• The material certificate does not match the heat number on the part, or the chemistry was never verified.
• Geometric tolerances and surface finish were omitted because they are hard to measure.
• Approval was given verbally, or against the wrong drawing revision.

Most FAI failures are reporting failures rather than manufacturing failures — and a reporting failure is exactly the kind a buyer can catch by reading the report carefully instead of glancing at the part and signing. The same discipline underpins a wider factory assessment; our supplier audit checklist shows how it fits into a full review.

It also helps to agree in advance how the first article will be measured. Fix the instruments, the datum scheme and the report format before the part is made, so that the submission arrives complete rather than in a drawn-out exchange. A little preparation at the planning stage removes most of the friction from the review.

Conclusion

First article inspection is the moment when an assumption becomes evidence. Verify every dimension, confirm the material, check surface and function, and make sure the gauges doing the checking are themselves trustworthy. Approve in writing, against a named drawing revision, and require a fresh FAI whenever the process changes. Do that, and mass production starts from a known-good baseline instead of a hopeful one. For more guides on buying from China, browse the GRDH blog; if you are still choosing a supplier, start with how to verify one before ordering.