Mold Approval Risk Checklist: Before You Sign Off the Tool

Mold approval is the point where a buyer’s leverage shifts permanently. Before sign-off, tool corrections are the supplier’s obligation; after sign-off, they become commercial negotiations. This checklist serves as the final gate. Execute it after the T1 sample review indicates the parts are acceptable, but strictly before signing the approval document. Its purpose is to intercept approvals that appear acceptable now but incur significant downstream costs. The mold approval decision explainer frames this decision process.

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 either physically corrected or explicitly documented as acceptable within the quality standard. What you approve now becomes the permanent specification.
• Process marks classified: Stress whitening and ejector marks must be formally classified in writing as either 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 merely the best samples presented.

2. Dimensional & Functional Verification

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

3. Process Stability

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

4. Documentation & Ownership

• Package complete: The dimensional report, locked process record, and issue-closure log must be on file.
• “Golden” samples retained: Approved reference parts must be clearly labeled, dated, and retained by both the buyer and the supplier.
• Acceptance standard finalized: Update the quality specification to include decisions made during trial (e.g., acceptable cosmetic zones, permissible witness marks, final color references).
• Tooling data secured: Collect tooling documentation per the tooling guide: 3D CAD files, steel certifications (if contracted), and the maintenance schedule.
• Ownership & transfer rights confirmed: Secure written confirmation of tool ownership and transfer rights. Clarifying ownership is inexpensive now and exorbitant during a dispute.

5. Commercial Closure

• Corrections scheduled: Any outstanding, agreed-upon tool modifications must be priced and scheduled, explicitly stating who bears the cost.
• Maintenance defined: Responsibilities for spare parts, wear components, and routine maintenance must be formally assigned.
• Production release conditions set: Define the criteria for the first production run (e.g., 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: Triggered by any open structural defect, unexplained process variation, missing ownership documentation, or unverified tool fix.

A held approval delays the program by days. A premature approval jeopardizes the entire product lifecycle. If uncertainty remains, paying for another tool trial is vastly cheaper than managing 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.