Checklist: Sheet Metal First Article Inspection

What Is a First Article Inspection

A first article inspection is a structured quality control checkpoint. It happens when a production run starts, before the full batch moves to the next stage. The goal is simple. Confirm that the first part meets the drawing, the material is correct, and the process is stable.

Buyers need this step to catch errors before they become expensive. A missing bend relief, a wrong alloy, or a surface defect on the first piece signals a problem that will repeat across the whole order. The inspection protects both the fabricator and the customer.

The process is not a one-time guess. It is a documented review. The inspector uses a checklist, measures the part, and records the results. This creates a baseline. Later in the run, the fabricator can compare subsequent parts against the first article data to monitor consistency.

Why First Article Inspection Matters

Without a first article inspection, defects can travel through the production line unnoticed. If the first sheet is loaded incorrectly, every part after it will have the same error. If the laser cutter uses the wrong kerf compensation, the hole sizes will be off by a consistent amount.

The first part is the most reliable indicator of the process state. It shows how the tooling, fixtures, and operators are performing. If the first piece passes, the process is likely stable. If it fails, the issue can be corrected immediately with minimal material loss.

This step also supports compliance and traceability. Many industries require proof that initial parts were verified. For automotive, aerospace, or medical applications, the first article record often becomes part of the quality file. It helps satisfy audits and customer requirements.

Dimensional Accuracy Checks

The first check is always against the drawing. The inspector uses calipers, micrometers, and gauges to measure critical features. The goal is to confirm that the part fits within the specified tolerances.

1. Overall length and width: Measure the finished part against the drawing. Check both horizontal and vertical axes.
2. Bend angles: Use an angle gauge or a dedicated fixture. Confirm that the bend matches the specified degrees.
3. Hole location and size: Measure the distance between holes. Check the diameter of each hole against the drill or punch specification.
4. Bend relief and radius: Inspect the bend area for proper relief. A missing relief can cause cracking or poor fit.
5. Flange height and straightness: Verify that flanges are uniform and not twisted. Use a straightedge or a gauge block.
6. Critical fit dimensions: Measure any feature that mates with another component. These often have tighter tolerances than general features.

Each measurement should be recorded. Note the actual value, the tolerance range, and the pass or fail status. If a dimension is outside the limit, the part is rejected. The process must be corrected before the next part is cut.

Common Dimensional Red Flags

• Bend angle drift: The angle changes as the operator adjusts the machine. This often happens when the first part is rushed.
• Hole position shift: The fixture or punch tool may be worn or misaligned. The holes will be consistently off.
• Flatness issues: The part may warp during cutting or forming. A flat part should sit evenly on a reference surface.
• Kerf variation: Laser or plasma cutting may leave holes that are slightly larger or smaller than specified. This can affect assembly.

Surface Finish and Workmanship

Surface quality is often the first thing a buyer notices. It affects function, appearance, and corrosion resistance. The inspector checks for defects that can compromise the part or indicate poor process control.

1. Burrs and sharp edges: Run a finger lightly across cut edges. Burrs indicate poor cutting or lack of deburring. Sharp edges can be a safety hazard.
2. Weld spatter and discoloration: If the part has welded features, check for spatter, cracks, or uneven heat discoloration.
3. Coating defects: Inspect painted or plated surfaces for runs, pinholes, or incomplete coverage.
4. Grinding marks: Check for deep tool marks that may interfere with mating surfaces.
5. Dent and deformation: Look for dents from handling or clamping. These can affect fit and finish.
6. Punch marks: Deep marks from punching can affect surface aesthetics and may indicate excessive force.

Surface defects are not always cosmetic. A missing paint coat can lead to corrosion. A sharp edge can damage other components. The inspector must judge severity against the drawing and the application.

Surface Finish Red Flags

• Inconsistent coating: Some areas are thick, others are thin. This suggests an uneven spray or dip process.
• Burn marks: Dark discoloration near bends or cut edges indicates excessive heat.
• Scratches on critical faces: Scratches on a face that mates with another part can cause leakage or poor contact.
• Oil or coolant residue: Leftover fluids can trap dirt and cause corrosion. They also indicate a missing cleaning step.

Material and Process Verification

The part may look correct, but the material could be wrong. A first article inspection must confirm that the input material matches the specification. This includes grade, thickness, and finish.

1. Material certificate: Request a mill certificate for the steel, aluminum, or other alloy. Verify the grade and heat number.
2. Thickness check: Measure the sheet thickness at multiple points. Variations can affect bend angles and fit.
3. Surface finish of raw material: Check for scale, rust, or coating before forming.
4. Tooling and fixtures: Verify that the correct dies, punches, and fixtures are in use.
5. Machine settings: Record the cutting speed, gas pressure, or laser power. These settings affect quality.
6. Process sequence: Confirm that steps follow the approved routing. For example, forming before cutting may change the part.

This step protects against substitution. Sometimes a fabricator uses a cheaper alloy to save cost. A material check prevents this. It also confirms that the thickness is within the specified tolerance. A thin sheet can bend differently than expected.

Documentation and Traceability

A first article inspection is only useful if it is documented. The form must show who inspected the part, when, and what was found. This creates a paper trail.

1. Part identification: Record the part number, revision, and serial number.
2. Date and inspector: Note the date, time, and name of the inspector.
3. Measurement records: List each check, the measured value, and the pass or fail status.
4. Nonconformance report: If a defect is found, document it clearly. Describe the location, size, and impact.
5. Correction action: Record how the issue was fixed. For example, “adjusted bend die and re-ran first part.”
6. Approval signature: The quality engineer or buyer must sign off on the accepted part.

This documentation supports audits and continuous improvement. If a problem appears later in the run, the first article record shows the baseline. It helps identify whether the issue is a process drift or a one-time anomaly.

Documentation Red Flags

• Missing mill certificate: A part without a material trace is risky for critical applications.
• Unsigned forms: An inspection without a signature is not official. It lacks accountability.
• Vague notes: Writing “looks fine” instead of “measured 12.1 mm” is not acceptable. Specificity is required.
• No revision control: If the drawing is updated, the first article must reference the correct revision.

First Article Inspection Checklist

Use this checklist to verify the first part. Print it out or use it digitally. Complete every item before releasing the production run.

Check Item	Specification	Measured Value	Status
Material Grade	Per drawing		Pass / Fail
Sheet Thickness	1.5 mm +/- 0.05 mm		Pass / Fail
Overall Length	100 mm +/- 0.2 mm		Pass / Fail
Bend Angle	90 degrees +/- 1 degree		Pass / Fail
Hole Diameter	5 mm +/- 0.05 mm		Pass / Fail
Surface Finish	No burrs, no scratches		Pass / Fail
Coating Coverage	100% coverage		Pass / Fail
Mill Certificate	On file		Yes / No

The status column is critical. If any item fails, stop the process. Do not proceed until the issue is corrected and the part is re-inspected. The checklist should be attached to the production order. Store it with the quality records.

How to Use the Checklist in Practice

The first article inspection is a team effort. The machine operator, the quality engineer, and the buyer all have roles. The operator prepares the part. The quality engineer measures and records. The buyer reviews the form and approves.

Start with the drawing. Confirm the revision. Check the material certificate. Then move to the part. Measure the dimensions first. This is the most objective check. After that, inspect the surface and workmanship. Finally, review the documentation.

If a part fails, do not simply scrap it. Identify the root cause. Is the tooling worn? Is the material wrong? Is the machine misaligned? Fix the cause, not just the symptom. Then re-run the first part. The process must be stable before the bulk run starts.

This habit saves money. A small correction at the start prevents a large batch of defective parts. It also builds trust with the supplier. A fabricator that provides a thorough first article inspection demonstrates control and professionalism.

When to Inspect Beyond the First Part

The first article is the baseline, but it is not the only check. For long production runs, sample inspection is required. The frequency depends on the part complexity and the application.

• High-risk parts: Inspect every piece or use a statistical sampling plan.
• Standard parts: Inspect a sample at regular intervals.
• Critical dimensions: Measure these more frequently, even if the part is standard.

The first article data helps set the sampling plan. If the first part was marginal, increase the inspection frequency. If it was perfect and consistent, a lower frequency may be acceptable. The key is to monitor the process, not just the part.