First Article Inspection — What It Is, When It Happens, and What We Verify Before a Production Run Begins
The first unit off a production line is not the same as the first unit that will ship to a customer. The difference between them is found in the First Article Inspection.
Before a new product enters mass production, before a new tool or mold is approved for use, before a production line resumes after a significant change — there is a moment of verification. That verification is the First Article Inspection (FAI).
FAI is a comprehensive inspection of the first production units from a new or modified process. It is not a quality gate for catching defects in an established line. It is a confirmation that the process is correctly set up, that the materials and components are what they should be, and that the first units off the line conform to the product specification. If FAI passes, the process is approved for production. If FAI fails, production does not begin until the root cause is found and corrected.
This article is written from the perspective of an LED therapy device OEM manufacturer — sharing how we structure and conduct FAI, which characteristics we verify, how we document the results, and when FAI is required.
When FAI Is Required — The Five Triggers
FAI is not a one-time event. It is required every time a process is established or re-established. The five standard triggers are:
Trigger 1: New product introduction When a new product design moves from prototyping to production, FAI is performed on the first production units to confirm that the production process is producing parts that match the design intent. This is the most common FAI scenario and the highest-stakes version — a new product has no production history, and the first units set the baseline for the production process.
Trigger 2: New tooling, mold, or fixture approval When a new mold is cut, a new tool is machined, or a new fixture is built, the first units produced with that tooling undergo FAI. Tool wear, machining tolerances, and fixture alignment all affect dimensional conformance — and the first units reveal whether the tooling was built to specification. For LED therapy devices, the silicone injection mold and the PCB housing mold are the two most critical tooling elements that require FAI before each new mold cavity or new mold set is approved.
Trigger 3: Process change When a production process parameter is changed — for example, the reflow profile for the PCB assembly, the injection molding temperature or pressure for the silicone housing, or the LED placement angle — FAI is required to confirm that the process change does not introduce new nonconformances. Even minor process changes can have unexpected effects on product conformance.
Trigger 4: Material or component change When a supplier change is made, when a material lot changes significantly, or when a component specification is revised, FAI confirms that the change does not affect product conformance. For LED therapy devices, changing the LED chip manufacturer, changing the silicone compound formulation, or changing the battery cell supplier all require FAI — because each of these changes can affect performance characteristics that are not always visible in casual inspection.
Trigger 5: Extended production downtime or re-location When a production line is idle for an extended period (typically more than 30 days), when tooling is moved, or when the production line is relocated, FAI is required before production resumes. Equipment that sits idle can drift out of specification — particularly temperature-dependent processes like reflow soldering and silicone molding.
What FAI Verifies — The Five Verification Categories
FAI is comprehensive by design. Unlike AQL sampling, which is focused on statistical lot acceptance, FAI is focused on the full verification of every significant product characteristic. There are five categories:
Category 1: Dimensional verification Every critical and major dimension is measured and recorded. For LED therapy devices, critical dimensions include: the silicone mask cavity internal dimensions (affecting user fit), the LED board mounting hole locations (affecting light uniformity), the battery compartment internal dimensions (affecting battery fit and safety clearance), the overall device thickness and weight (affecting ergonomics), and the charging port alignment and depth (affecting charging reliability).
Measurement tools used depend on the tolerance: outside micrometers and calipers for general dimensions, thread gauges for threaded features, coordinate measuring machines (CMM) for complex geometries, and Go/No-Go gauges for functional fit checks.
Category 2: Material verification Every material that affects safety, function, or durability is verified against the approved material specification. For LED therapy devices, material verification includes: the silicone compound Shore hardness (affecting skin comfort), the silicone color and transparency (affecting light transmission), the housing material type and flame retardancy rating (affecting electrical safety), and the battery cell model and capacity (affecting run time and safety).
Material verification is confirmed through certificates of conformance (CoC) from the material supplier, combined with in-house verification tests for critical material properties (hardness, color, thickness).
Category 3: Functional verification Every function that is defined in the product specification is tested and the results recorded. For LED therapy devices, functional verification includes: LED output irradiance measurement (confirming therapeutic dose), LED wavelength measurement (confirming correct channel wavelengths), touch controller function (on/off, intensity levels, timer), battery charge and discharge cycle performance, and thermal management performance (battery temperature during operation at maximum ambient).
Category 4: Cosmetic verification Every visible surface is inspected against the approved golden sample (reference unit). Cosmetic verification is subjective by nature — which is why golden samples are essential for FAI. The golden sample is a production-equivalent unit that has been approved by the customer as the reference for cosmetic acceptability. Any deviation from the golden sample that is noticeable under normal viewing conditions is a cosmetic nonconformance.
For LED therapy devices, cosmetic verification covers: the surface finish of the silicone (no flash, no sink marks, correct texture), the LED lens clarity and alignment, the label placement and legibility, the color consistency of all visible components, and the overall appearance of the device packaging.
Category 5: Documentation and traceability verification The first article unit must be traceable to the production conditions under which it was made. Documentation verification confirms that the Device History Record contains: the material lot numbers used in the first article unit, the production line and operator, the production date, the measurement results for all verified characteristics, and the acceptance decision with the name of the authorizing inspector.
The AS9102 Framework — How FAI Is Structured
The aerospace industry developed AS9100-series standards, and AS9102 (First Article Inspection) is the most widely referenced FAI standard in precision manufacturing. Even for non-aerospace manufacturers, AS9102 provides a useful three-part structure:
Part 1 — Part Number and Characteristic Verification Records the part number, revision level, and the complete list of characteristics to be verified. Each characteristic is classified as Critical, Major, or Minor (matching the defect classification used in AQL inspection). The measurement instrument and measurement method are recorded for each characteristic.
Part 2 — Measurement Results Records the actual measured value for each characteristic. For attribute characteristics (pass/fail, go/no-go), the result is simply pass or fail. For variable characteristics (dimensional measurements), the actual measured value is recorded. Any characteristic that does not meet the specification is flagged as a nonconformance.
Part 3 — Inspection Summary Summarizes the FAI results: the overall disposition (accepted, conditionally accepted with deviations, or rejected), the nonconformance list, the corrective actions taken, and the authorization signatures. The Part 3 form is the official record of the FAI decision.
FAI Process at RainbowDO — Step by Step
Step 1: Trigger identification Before production begins, identify whether FAI is required by reviewing the five triggers. If any trigger is met, FAI is mandatory — regardless of whether the production run is large or small.
Step 2: Sampling Select a minimum of 3 units from the first production run for FAI. Three units are sufficient to detect unit-to-unit variation and to identify whether a defect is a systemic process issue or an isolated anomaly.
Step 3: Full dimensional inspection Measure all critical and major dimensions per the inspection plan. Record all results in the Part 2 form. Any dimension outside tolerance is a nonconformance — document and initiate corrective action.
Step 4: Material verification Collect and verify all material certificates. Perform hardness, color, and thickness verification on the silicone components. Verify battery cell model and capacity against the approved component specification.
Step 5: Functional testing Run the complete functional test protocol on each FAI unit. Record irradiance, wavelength, charge/discharge performance, and thermal performance for each unit. Calculate unit-to-unit variation — any single unit that fails functional criteria is a nonconformance.
Step 6: Cosmetic inspection Compare each FAI unit against the golden sample under standard lighting conditions. Any cosmetic deviation that is visible under normal viewing conditions is a nonconformance — photograph and document the deviation.
Step 7: Documentation review Verify that the Device History Record is complete and traceable. Confirm that all material lot numbers, production conditions, and measurement results are recorded.
Step 8: FAI disposition Complete the Part 3 summary. If all characteristics pass: FAI accepted, production approved. If nonconformances are found: FAI rejected, root cause analysis required, corrective action required, FAI re-inspection required after corrective action.
Step 9: Production release Only after FAI is formally accepted is the production lot released for shipping. No lot ships on the basis of a pending FAI — even if the units look correct visually.
FAI and AQL — How They Work Together
FAI and AQL serve different purposes at different stages of the production lifecycle:
| Aspect | FAI | AQL |
|---|---|---|
| When | Before production begins or after a change | During ongoing production |
| Scope | Every significant characteristic | Statistical sample |
| Purpose | Verify process setup is correct | Verify lot meets quality standard |
| Trigger | Five defined triggers | Every production lot |
| Decision | Accept / Reject / Conditional | Accept / Reject |
| Documentation | AS9102 three-part form | Inspection record |
FAI clears the process. AQL monitors the process. They are complementary — not interchangeable. A lot that passes AQL but has not been through FAI after a process change may contain systematic nonconformances that AQL sampling will not reliably detect.
First Article Inspection — Common Questions
Q1: We ran FAI and found one minor dimension out of tolerance on one unit. The rest of the units look fine. Can we still accept the FAI?
No — not if the characteristic is classified as Critical or Major. FAI is not a pass-or-fail decision on the overall lot; it is a verification that every characteristic meets specification. One out-of-tolerance dimension on any unit triggers a nonconformance report, a root cause investigation, and a corrective action. Only Minor characteristic deviations may be dispositioned as “use-as-is” or “repair” — and only with formal written approval from the authorized quality representative. For Critical and Major characteristics, the process must be corrected and the affected units re-inspected before FAI is accepted.
Q2: Our supplier says they ran FAI internally and it passed. Do we need to run it again?
Yes — supplier FAI and incoming FAI are two different events. Supplier FAI verifies that the supplier’s process is correctly set up. Incoming FAI (performed on the customer side) verifies that the received parts meet your product specification, not just the supplier’s. The two specifications may differ, the measurement methods may differ, and the acceptance criteria may differ. Additionally, incoming FAI verifies that the parts arriving are the ones that passed the supplier’s FAI — parts can be damaged or mixed during transit. The cost of running incoming FAI is always lower than the cost of a field failure caused by a nonconforming part that was not inspected on receipt.
Q3: How do we handle FAI for a product with a large number of individual characteristics — like a complex LED assembly with 50+ measurement points?
For complex assemblies, prioritize the FAI characteristics into three tiers. Tier 1 (all characteristics must pass): Safety-critical dimensions, regulatory-specified characteristics, and any characteristic that is listed in the customer’s product specification as a critical requirement. Tier 2 (first inspection; may be reduced to monitoring after stable production): Secondary dimensional and functional characteristics that affect product performance but are not safety-critical. Tier 3 (first inspection; may be eliminated if supplier has a strong quality history): Cosmetic and non-critical characteristics that are verified by AQL inspection during ongoing production. The FAI report documents all three tiers — but the disposition decision is based on Tier 1 results, with Tier 2 and Tier 3 results recorded for reference and trend tracking.
This article is written from the perspective of an LED therapy OEM manufacturer that conducts First Article Inspection before every new product launch, every new tool approval, and every significant process or material change. The FAI structure referenced follows the AS9102 three-part form framework. Specific FAI protocols, characteristic lists, and acceptance criteria should be defined in the product’s Quality Inspection Plan and Device Master Record.