Mold Approval Risk Checklist: Before You Sign Off the Tool

Mold approval is where a buyer’s leverage shifts permanently. Before sign-off, tool corrections are the supplier’s obligation. After sign-off, they become commercial negotiations. Run this checklist after the T1 sample review says parts are acceptable, and before you sign the approval document. Goal: catch approvals that look fine now and cost you later. The mold approval decision explainer frames the decision.

1. Defect Status

• Zero open structural findings: Defects like cracks, voids in loaded bosses, or weak weld lines under mechanical load dictate an automatic hold.
• Cosmetic defects resolved or codified: Visual findings must be physically corrected or explicitly documented as acceptable in the quality standard. What you approve now becomes the permanent specification.
• Process marks classified: Stress whitening and ejector marks must be classified in writing as inherent to the geometry or fixable.
• Corrections physically verified: Never sign off on a promise to “polish the tool later.” Verify every fix on actual molded parts.
• Multi-cavity review: Inspect parts from the worst-performing cavity, not only the best samples presented.

2. Dimensional & Functional Verification

• Critical dimensions confirmed: All critical-to-function dimensions must be within tolerance on the inspection report. Deviations need formal concession from your engineering team.
• Cavity-to-cavity variation checked: For multi-cavity tools, review dimensional spread across all cavities against the allowable tolerance stack.
• Physical assembly verified: Test fit and function with actual mating components, not just drawings.
• Mechanical features tested: Verify loaded features (snap-fit cyclic testing, threaded boss torque limits) on samples from this specific tool.

3. Process Stability

• Cycle time verified: Demonstrated cycle must align with the quoted cycle. If there is a gap, the supplier must explain it and adjust piece price if the slower cycle is permanent. See cycle time.
• Ejection confirmed: Demolding must be unassisted. Continuous mold release spray to overcome sticking means the tool is not production-ready.
• Process parameters locked: The process record that produced the approved samples must be documented and reproducible.
• Material validated: Confirm the exact specified resin grade, secure the Certificate of Analysis (CoA), and document the agreed regrind policy.

4. Documentation & Ownership

• Package complete: Dimensional report, locked process record, and issue-closure log on file.
• “Golden” samples retained: Approved reference parts labeled, dated, and retained by buyer and supplier.
• Acceptance standard finalized: Update the quality specification with trial decisions (acceptable cosmetic zones, permissible witness marks, final color references).
• Tooling data secured: Collect tooling documentation per the tooling guide: 3D CAD, steel certifications (if contracted), maintenance schedule.
• Ownership & transfer rights confirmed: Written confirmation of tool ownership and transfer rights. Clarifying ownership is inexpensive now and expensive in a dispute.

5. Commercial Closure

• Corrections scheduled: Outstanding agreed tool modifications priced and scheduled, with who pays stated explicitly.
• Maintenance defined: Responsibilities for spare parts, wear components, and routine maintenance assigned in writing.
• Production release conditions set: Criteria for the first production run (initial quantity, required validation steps).

The Approval Decision

• Approve: All checklist sections are clear.
• Approve with Conditions: Open items remain, but every item has an assigned owner, a strict deadline, and a defined verification method documented directly in the sign-off agreement.
• Hold: Any open structural defect, unexplained process variation, missing ownership documentation, or unverified tool fix.

A held approval costs days. A premature approval can cost the product lifecycle. If uncertainty remains, another tool trial is cheaper than a production recall.

Disclaimer

PlasticsTechnologyAlliance.com is an independent buyer resource. This checklist augments, but does not replace, your internal engineering review, quality management system, and legal contracts. Approval criteria must be calibrated to your specific part’s risk profile and industry requirements.