How to Verify Stamping Supplier Die Maintenance Logs

Why Die Maintenance Logs Matter for Quality

Stamping quality depends on consistent die condition. A well-maintained die produces uniform parts, while a worn die introduces variation. Engineers reviewing a supplier’s records need to confirm that the documented maintenance matches the physical tooling.

Die maintenance logs capture the history of each die. They record when the tooling was inspected, cleaned, lubricated, and adjusted. For complex parts, these records show when critical edges were replaced. Without them, a supplier cannot prove that the same die produced the current lot as the qualified sample.

Prerequisites for Reviewing the Records

Before starting the review, gather specific documents from the supplier. Request the maintenance log for each die used in the production run. Include the die number, the part number, and the date range covering the production period.

Obtain the tooling lifecycle records as well. These files track the die from build through retirement. They show when the die was first qualified and when it reached end of life. Also request the first-article inspection reports for the production lot.

The audit team should have access to the press floor. Physical inspection of the dies is required to validate the written records. Without floor access, the review remains a document exercise.

Step 1: Identify the Correct Die Number

Start by matching the die number on the production order to the maintenance log. The die number is usually stamped into the die body. A mismatch here indicates a data entry error or a substitution that was not documented.

Check the die number against the tooling lifecycle record. The lifecycle file should show the die number at build. If the numbers differ, stop the review. The supplier may be using a different die than the one qualified for the part.

Step 2: Verify the Maintenance Interval

Review the maintenance interval defined for the die. This interval is based on the part complexity and the material. A simple bracket in mild steel may require maintenance every twenty thousand strokes. A complex housing in stainless steel may need service every five thousand strokes.

Count the strokes since the last service. The log should show the stroke counter at the time of the last maintenance. Compare this number to the current stroke count. The difference tells you how much the die has operated since the last service.

If the stroke count exceeds the defined interval, the die is overdue for service. This creates a quality risk. The supplier should have flagged this and performed corrective action.

Step 3: Inspect the Physical Die Condition

Move to the press floor and inspect the die. Look at the cutting edges for wear. A well-maintained die shows a clean, sharp edge. A worn die shows a rounded edge or visible chatter marks.

Check the die surface for lubrication residue. The log should record the type of lubricant used. The physical die should show evidence of this lubricant. A dry die contradicts the log.

Examine the die for scoring or galling. These marks indicate a problem with the material or the die surface. The maintenance log should note any die surface repairs made during the last service.

Step 4: Cross-Reference First-Article Data

Pull the first-article inspection report for the production lot. The report should list the critical dimensions. Compare these dimensions to the part print tolerance.

Check the date on the first-article report. It should follow the last die maintenance date. If the first article was taken before the last service, the supplier may have run a lot with a die that had not been fully qualified after maintenance.

Review the first-article notes for any die-related issues. If the report mentions edge wear or part variation, the maintenance log should show a corresponding action taken.

Step 5: Confirm Lubrication Records

Check the lubrication records for the specific material in use. Different materials require different lubricants. Mild steel may use a water-soluble lubricant. Stainless steel often requires a different type.

The log should record the lubricant lot number. This allows traceability if a lubricant defect causes part issues. If the log only says “lubricated,” it is insufficient. The specific product name or lot number is required.

Inspect the lubrication application points on the die. The log should show when these points were cleaned and checked. A clogged lubrication point causes premature die wear.

Step 6: Review Press Setup Sheets

The press setup sheet documents the press settings for each die. It includes the tonnage, speed, and back gauge settings. Compare these settings to the tooling lifecycle record.

The lifecycle record should show the qualified settings for the die. If the press setup sheet differs from the qualified settings, a change was made. The maintenance log should show an approval for this change.

An unapproved press change can damage the die. It can also cause part variation. The audit should confirm that all press changes are documented and approved.

Step 7: Check for Unapproved Modifications

Review the tooling lifecycle for any modifications to the die. This includes changes to the die geometry, the mounting method, or the lubrication system.

Each modification should have a documented approval. The approval should reference the engineering change order. If a modification is present on the die but not in the lifecycle record, it is unapproved.

Unapproved modifications break the chain of quality. They mean the current die is not the same as the die that passed the initial qualification. The supplier cannot claim the parts are produced to the qualified tooling standard.

Step 8: Verify the Retention Period

Check the retention period for the maintenance logs. The log should cover the entire production life of the die. If the log ends before the die is retired, the records are incomplete.

The retention period should match the part life cycle. For a part with a long service life, the die records must be kept for a similar period. This allows traceability if a field failure occurs.

If the supplier has deleted old logs, the audit is incomplete. The supplier cannot prove the tooling history for the full part life.

Common Mistakes in Die Maintenance Logging

Engineers often make mistakes when reviewing these records. The most common error is accepting the log at face value. The log is only as good as the physical die. Always inspect the tooling.

Another mistake is ignoring the stroke counter. The stroke counter is the most objective measure of die wear. If the supplier does not track strokes, the maintenance interval is based on guesswork.

Some suppliers use a generic maintenance log for all dies. This is a red flag. Each die has a specific interval based on the part. A generic log does not reflect the actual tooling condition.

Final Verification Step

After completing the steps above, perform a final verification. Select one die from the production lot. Trace its full history from the lifecycle record to the maintenance log to the physical die.

Confirm that the die number is consistent across all documents. Confirm that the maintenance dates match the physical condition. Confirm that the stroke count is within the defined interval.

If the trace is complete and consistent, the die maintenance log is verified. If any step fails, the supplier must provide a corrective action plan before the production lot is accepted.

Summary of Verification

This process verifies that the supplier’s die maintenance logs are accurate. It matches the written records to the physical tooling. It confirms that the die is maintained to the qualified standard.

The result is a reliable tooling lifecycle. The engineer can trust that the parts are produced with consistent die condition. This reduces quality risk and supports long-term supplier reliability.