Injection Mold Acceptance Standards and Inspection Checklist

Mold acceptance marks the critical transition from trial molding to mass production. The acceptance result directly impacts product yield, production stability and mold service life. Acceptance should not only check sample appearance. Inspectors need to verify items against drawings, DFM plans, moldflow reports and technical agreements. The whole inspection covers four major sections: mold hardware inspection, molded sample testing, motion mechanism validation and document handover. Clear judgment criteria for each item help avoid design and machining defects discovered after mass production starts.

Mold Hardware Inspection

The mold surface should be free of obvious dents, rust and improper welding marks. The nameplate is complete with mold number, product name, cavity quantity, mold base specification, shrinkage rate and production date. Datum marks on the mold base are clear, and lifting rings are firmly installed to match mold weight. Steel grade and hardness of cavities and cores must comply with the agreement. Material certificates and hardness test reports are required. The polished surface of A-class surface meets specified requirements, without scratches, pockmarks or sanding lines. Shut-off surfaces fit tightly without intermittent gaps. For gating systems, hot runner manifolds and nozzles must be fixed securely. 

Heating coils and thermocouples are neatly wired with clear labels. Cold runner surfaces are smooth without burrs or dead zones for material buildup. Water circuits are tested under specified pressure with no leakage. Inlet and outlet marks are clear, and flow is balanced. Vent grooves match drawings on position, depth and width, free of blockage or excessive depth causing flash. Ejector pins, sleeve pins and flat ejectors move smoothly without jamming or scratching molded parts. Sliders and lifters move steadily without shaking or abnormal noise. Locking blocks hold firmly and limit switches send accurate signals. Guide pins and guide bushes fit properly, with no dragging or uneven wear.

Molded Sample Testing Items

Visual inspection of A surface checks for silver streaks, bubbles, burn marks, sink marks, flow lines, obvious weld lines, ejection whitening and scratches. Gate vestige size meets acceptance requirements and will not interfere with assembly or appearance. Dimension measurement follows 2D and 3D drawings. Inspectors focus on assembly datums, buckles, screw bosses and sealing grooves using calipers, micrometers and CMM. For glass-filled materials, samples need aging treatment before re-measurement to account for post-shrinkage. Assembly matching test verifies fit between parts, seals and fasteners. Insertion and locking force stay within agreed ranges. For enclosure parts with IP rating requirements, sampling sealing tests are arranged. Load-bearing structures go through drop, tension and torsion tests. Flame retardant parts shall be accompanied by material reports satisfying UL94 or GB standards. 50 to 100 consecutive shots are sampled to calculate defect rate including flash, short shot and sticking. Weight fluctuation is controlled within a reasonable range to confirm stable filling and packing.

Motion, Safety and Mass Production Validation

Mold opening and closing runs smoothly without impact noise or crawling. Low-pressure mold protection is well adjusted to prevent mold crash. Temperature error of hot runner zones is controlled within ±5℃. Signals of ejection return, slider limit and safety switches work normally and match the injection machine. The mold can release parts stably without sticking to cores during automatic cycling. After continuous running for more than two hours, part quality does not drift obviously. Cavity surface does not accumulate carbon or corrode rapidly. Spare parts including wear plates, ejector pins, springs and sealing rings are delivered according to the spare list.

Technical Document Acceptance

Deliverables include complete 2D assembly drawings, part drawings, 3D mold files and archived revision records. Steel material certificates, heat treatment reports, hardness test reports and hot runner qualification documents are provided. Moldflow analysis, DFM records, trial molding reports and dimension inspection sheets are also included. A mold maintenance manual marks lubrication points, cleaning cycles and troubleshooting guidance.

Acceptance Judgment Rules

Test items are classified into pass, conditional acceptance and fail. Critical items such as steel material, water leakage, positioning deviation and safety protection failing will result in overall rejection and rework. Minor non-critical defects can be conditionally accepted with written confirmation and scheduled rectification. After all items pass, the acceptance document is signed for mass production handover. Small batch trial production on the customer’s own injection machine is recommended to eliminate risks caused by different machine parameters.