A first article inspection (FAI) is a production validation step in which a supplier fully measures and documents the first part (or a sample from the first batch) produced by a new or changed process, and the buyer reviews that documentation before releasing volume work. For CNC parts, the FAI answers one question: does the process that will make thousands of pieces actually produce a part that matches the drawing? For buyers, the deliverable is not a promise — it is a report you can check.
What an FAI Report Should Contain
A useful FAI package has three layers: the ballooned drawing, the measurement results, and the evidence behind them. Treat each as a separate review item, because a report can pass the first two and still hide gaps in the third. An FAI is typically a purchase order requirement placed on the supplier by the purchaser, so the scope of what it must cover is ultimately defined by the contract rather than by the supplier’s preference. If the terminology of inspection reporting is new to you, our buyer guide to inspection reports and checks covers the broader document set that an FAI sits within.
The Ballooned Drawing
Every dimension, tolerance, note, and specification on the drawing is assigned a numbered balloon. The balloon number becomes the index that ties each requirement to the measurement that satisfies it. When you review a ballooned drawing, check that the balloon count matches the drawing’s actual set of requirements — not a convenient subset. A report that balloons only “critical” features is a flag, because an FAI is meant to verify every parameter of the process rather than only the tightest tolerances.
Ask what revision the balloons were drawn against. If the drawing revision changed after the FAI, the inspection no longer describes the part you will receive. The clarity of the source drawing drives everything downstream, so it is worth confirming the drawing requirements a shop needs before quoting are complete.
Measurement Results
Measurement results should list, for each balloon, the nominal, the tolerance, the measured value, the pass/fail result, and the instrument used. Dimensional characteristics such as size, shape, and feature location are normally verified with calibrated instruments — coordinate measuring machines (CMMs), calipers and micrometers, or go/no-go gauges. For each instrument, the report should reference calibration status; an uncalibrated result is an opinion, not a measurement.
Compare the reported values against the drawing, not against the supplier’s summary. One of the most common review findings is a value that sits outside the tolerance band but was recorded as conforming. Sampling also matters: if the first article was measured from a sample rather than the very first part, confirm how the sample was selected and whether it is representative.
Material Evidence
Dimensional compliance alone does not prove the part is correct. The FAI should carry material evidence: the mill certificate or material test report for the lot used, with the alloy designation and condition traceable to the part. Depending on the requirement, material testing may also cover hardness, conductivity, or other properties. Where the specification calls for a particular grade or temper, confirm the certificate matches it and that the certificate is for the same heat or lot as the material consumed.
Special Processes
Special processes — heat treatment, plating, passivation, anodizing, welding, and similar operations — often cannot be fully verified by dimensional inspection after the fact, and they frequently change the part’s surface finish and final dimensions. Their conformance is usually demonstrated by process records and, where applicable, certification from an approved processor. In aerospace and medical work, undefined special processes may be handled by an approved subcontract supplier such as an accredited testing or metrology laboratory; this is a separate activity from the dimensional FAI and should be documented as such. Ask which special processes were applied to the first article, who performed them, and what evidence accompanies each.
Deviation Handling
A first article is not expected to be perfect. The question is whether every nonconformance is documented and dispositioned. Look for a deviation or concession record that states the requirement, the actual condition, the root cause, and the disposition — use-as-is, rework, or scrap — with the buyer’s approval where the contract requires it. Undocumented deviations are the single most dangerous finding in an FAI review, because they transfer risk to the buyer without notice. When tolerances interact across an assembly, a single conforming-but-marginal feature can still cause a fit problem, which is why tolerance stack-up review belongs next to the FAI discussion.
Standards Context and Their Boundaries
What an FAI must contain depends on the industry and the contract, not on a single universal rule. In the aerospace industry, the SAE AS9102 Aerospace First Article Inspection Requirement is the North American standard, documented on Form 1 (Part Number Accountability), Form 2 (Product Accountability), and Form 3 (Characteristic Accountability); the Japanese equivalent is SJAC9102 and the European equivalent is EN9102. More generally, FAI can serve the process validation requirement of a quality management system such as ISO 9001, EN9100, or AS9100. This article is not certification-specific: the checklist above applies to a general precision CNC sourcing context, and any claim of compliance must be verified against the actual contract and the applicable revision of the standard.
A Buyer’s Review Checklist
- Is the ballooned drawing complete and drawn against the current revision?
- Does every balloon have a measurement result with nominal, tolerance, actual value, and pass/fail?
- Are the instruments identified and their calibration status current?
- Was the measured part the true first article, or a documented sample of the first batch?
- Is material evidence traceable to the lot used, with the correct alloy and condition?
- Are special processes listed with processor and supporting records?
- Is every deviation documented and dispositioned with the required approval?
- Does the package state the standard or specification it is being issued against?
How to Use the FAI Before Volume Release
Treat the FAI as a gate, not a formality. Define up front which report form and which standard apply, request the package before approving volume production, and record your review conclusions in writing. If a supplier cannot show the balloon index matching the measurement table, that is not a paperwork detail — it means the evidence chain is broken, and the cheapest place to fix it is before the first production run, not after. The same discipline applies when a process changes later: a re-qualification FAI on the changed process protects both sides from a defect that only appears in volume.
