Last updated: 2026-09-01 · 5 min read

What Is a First Article Inspection (FAI) — and How Is It Different from a T1 Mold Trial?

A First Article Inspection (FAI) is a comprehensive dimensional and functional verification of the first production parts — typically 3–30 pieces — produced under production conditions (stable process, final mold, specified resin, documented parameters). The FAI verifies that the manufacturing process, not just the mold, produces parts that conform to every dimension on the engineering drawing.
A T1 mold trial verifies that the mold functions (fills, ejects, cycles); an FAI verifies that the process produces conforming parts. The T1 happens at the mold maker’s facility; the FAI happens at the production facility (which may be the same location or a different one).

Warpage — Part deformation after ejection caused by uneven shrinkage. Amorphous resins warp less (0.4–0.7% shrinkage). Semi-crystalline resins warp more (1.0–2.5% shrinkage). Fix: uniform wall thickness, balanced cooling, optimized gate location, adequate packing pressure. See also related guide.

Key Facts

  • The FAI is performed under production conditions — the same machine, same resin lot, same process parameters, same operator, and same ambient conditions that will be used for the production run. Parts molded during a T1 (at the mold maker’s facility, with trial resin and trial parameters) are not FAI parts because the conditions are not representative of production.
  • The FAI measures every dimension on the engineering drawing — typically 50–200 dimensions per part, including critical dimensions (fit, function, assembly), reference dimensions (overall size, wall thickness), and cosmetic dimensions (surface profile, parting-line location). The T1 report measures critical dimensions only (typically 20–50 dimensions).
  • The FAI documentation follows the AS9102 format (aerospace standard, widely adopted across industries) — a three-form package: Form 1 (part number accountability), Form 2 (product accountability — raw material, specifications, special processes), and Form 3 (characteristic accountability — every dimension measured against the drawing with actual values recorded).

    • Warpage — Part deformation after ejection caused by uneven shrinkage. Amorphous resins warp less (0.4–0.7% shrinkage). Semi-crystalline resins warp more (1.0–2.5% shrinkage). Fix: uniform wall thickness, balanced cooling, optimized gate location, adequate packing pressure. The related guide covers adjacent topics.

    T1 vs FAI Comparison

    Aspect T1 Mold Trial First Article Inspection
    Purpose verify mold function verify process conformance
    Location mold maker’s facility production facility
    Conditions trial parameters, trial resin production parameters, production resin
    Sample quantity 5–20 shots 3–30 parts (per drawing)
    Measurements 20–50 critical dimensions every dimension on drawing
    Documentation trial report (internal format) AS9102 format (3 forms)
    Acceptance mold maker + customer engineer customer quality department

    What the FAI Report Includes

  • Form 1 — Part Number Accountability: lists the part number, revision level, drawing date, and the serial numbers or lot identification of the FAI samples. This form links the FAI to the specific engineering drawing revision and ensures that the inspection was performed against the correct revision.
  • Form 2 — Product Accountability: documents the raw material (resin grade, lot number, supplier certificate of conformance), any special processes (annealing, post-mold conditioning, secondary operations), and the production equipment used (machine ID, mold ID, process-parameter printout). This form establishes traceability from the finished part back to the resin lot and the molding machine.
  • Form 3 — Characteristic Accountability: lists every dimension from the drawing with the nominal value, the tolerance, the measured value (actual), and the measurement method (CMM, optical comparator, caliper, go/no-go gauge). Every characteristic is marked pass or fail. A balloon drawing (a copy of the drawing with numbered callouts for each dimension) accompanies Form 3.

    • When Is an FAI Required?

    1

    New part — first production run

    The first production run of a new part requires a full FAI. The T1 and T2 mold trials verified the mold; the FAI verifies that the production process (machine, resin, parameters, operator) produces conforming parts.

    2

    Process change — machine, resin lot, or parameter change

    If the production machine changes (different tonnage, different screw), the resin lot changes (different melt-flow index), or the process parameters change significantly (injection speed, hold pressure, cooling time), a partial or full FAI may be required depending on the customer’s quality requirements.

    3

    Mold modification — after T2 or engineering change

    If the mold was modified after T1 (steel-safe changes, insert replacements, gate modifications), the next production run requires an FAI to verify that the modification did not introduce dimensional changes beyond the drawing tolerance.

    4

    Production interruption — after extended downtime

    If production was interrupted for more than 12 months (or the customer’s specified interval), a new FAI verifies that the process is still capable after the extended downtime. The mold may have been in storage, the machine may have been serviced, and the operator may have changed.

    Frequently Asked Questions

    Is an FAI the same as PPAP (Production Part Approval Process)?

    No. PPAP is the automotive-industry standard (AIAG PPAP 4th edition) that includes the FAI as one of its 18 required elements. PPAP also includes the process flow diagram, PFMEA, control plan, MSA (measurement system analysis), and initial process capability study (Cpk). An FAI alone is not a PPAP submission — the FAI is the dimensional-verification component within the larger PPAP package.

    How many parts are required for an FAI?

    The sample quantity is specified by the customer — typically 3–30 parts. Three parts are sufficient for a simple part with few critical dimensions; 30 parts are required when the customer needs a statistical process capability study (Cpk calculation requires a minimum of 30 data points per characteristic). The FAI samples must be produced consecutively (not cherry-picked) from a stable production run.

    Who performs the FAI measurement?

    The FAI can be performed by the mold maker (as a service to the customer), by the customer’s incoming quality department, or by a third-party inspection lab. The measurement must be performed by a qualified inspector using calibrated equipment. The FAI report must include the measurement equipment ID, calibration date, and inspector name for traceability.

    Key Takeaways

    1. The FAI verifies the production process, not just the mold. The T1 verified that the mold works; the FAI verifies that the production conditions (machine, resin, parameters, operator) produce parts that meet every dimension on the drawing.
    2. The FAI measures every dimension on the engineering drawing — not just the critical dimensions. A part with 150 dimensions requires 150 measurements on each of the 3–30 FAI samples. The documentation follows the AS9102 three-form format.
    3. An FAI is required for new parts, after process changes, after mold modifications, and after extended production interruptions. Each trigger requires a new verification that the process still produces conforming parts under the current conditions.

    A quotation that includes the FAI as a deliverable (with the sample quantity, the documentation format, and the cost itemized) sets the expectation before the deposit is paid. A quotation that omits the FAI and presents it as a surprise charge after T1 creates friction at the point where the customer is already committed. The FAI cost ($500–2,000 for the inspection and documentation, depending on the number of dimensions and samples) should be included in the quotation as a separate line item.

    Sources
    SAE International — AS9102 FAI standard
    AIAG — PPAP 4th edition
    Plastics Technology — quality assurance

    Sources: Plastics Technology · Plastics Technology Online · Society of Plastics Engineers (SPE) · ThomasNet