How to Ensure Quality Stability and Reliability of Custom Plastic Parts

1. Raw Material Control

1.1 Supplier Selection

Choose raw material suppliers with good reputation and sound quality management systems. Evaluate supply capacity and stability through on-site inspections of their production facilities, processes, and quality control procedures. Prioritize suppliers certified to ISO 9001, with strong industry reputation and long-term supply capability to ensure consistency across material batches.

1.2 Material Inspection

Implement strict inspection for each batch of raw materials. Use Differential Scanning Calorimetry (DSC) to test melt flow rate for consistent fluidity. For hygroscopic materials like PA and PC, test moisture content with a moisture analyzer; dry moisture-exceeding materials under vacuum before production to avoid defects such as bubbles. Conduct sampling tests on physical properties (density, tensile strength, flexural strength) to meet relevant standards.

2. Mold Design and Manufacturing

2.1 Design Optimization

Product-Adapted Design: Design mold size compensation based on plastic shrinkage. Optimize product structure for uniform wall thickness, add ribs in thick areas to prevent sink marks, set reasonable draft angles on demolding surfaces, and use fillet transitions for sharp edges.

Core Structure Design: Select simplified parting surfaces; use combined parting for complex products. Arrange cavities symmetrically for balanced melt filling. Adopt insert design for wear-prone parts and use wear-resistant steel for moving components.

Auxiliary System Design: Use circular runners; choose pin gates (small parts) or fan gates (large parts) away from stress/aesthetic areas. Design conformal cooling channels for uniform cooling; use ejector pin-plate combination to avoid deformation. Add vents at melt filling ends for air release.

2.2 Manufacturing Precision

Use high-precision equipment (5-axis machining centers) for cavity processing to control surface roughness. Strictly control EDM parameters for surface quality. Ensure precision of key fitting dimensions and conduct comprehensive debugging after assembly for smooth operation.

3. Injection Molding Process Control

3.1 Temperature Control

Set barrel temperatures in sections based on plastic properties to avoid degradation or poor fluidity. Maintain stable mold temperature via cooling/heating systems for consistent molding quality.

3.2 Pressure and Speed Control

Adjust injection pressure based on wall thickness and complexity. Use staged injection speed: low initial speed (prevent turbulence), high middle speed (fast filling), low holding speed (compensate shrinkage). Set appropriate holding pressure and time to avoid sink marks.

3.3 Cooling Time Control

Determine cooling time based on material thermal properties and wall thickness to ensure parts cool below heat distortion temperature, reducing deformation.

4. Quality Inspection

4.1 Dimensional Inspection

Use CMM to inspect dimensions, focusing on key assembly sizes. Develop sampling plans based on production volume: increase sampling ratio for small batches; follow standard procedures for mass production.

4.2 Visual Inspection

Use optical microscopes to check for defects (sink marks, flash, bubbles). For high-surface-quality parts, use colorimeters to control color deviation (ΔE). Identify and isolate non-conforming products for root cause analysis.

4.3 Performance Testing

Conduct targeted tests: thermal cycle tests for high/low temperature applications, burst tests for pressure-bearing parts, and mechanical property tests (tensile, flexural, impact strength) to meet design requirements.

5. Mold Maintenance

5.1 Daily Maintenance

Clean residual plastic and oil after production; lubricate moving parts (guide pillars, slides) with special grease. Check cooling water circuits for blockages.

5.2 Regular Maintenance

Develop plans based on usage frequency. Disassemble molds to inspect/weld/polish cavities; replace worn parts (seals, springs). Restore precision through grinding and testing.

5.3 Storage and Preservation

Clean and rust-proof idle molds; store in dry, ventilated racks. Establish maintenance records for tracking.

6. Conclusion

Ensuring quality stability of custom plastic parts requires full-process control: raw material screening, precision mold manufacturing, refined injection processes, comprehensive quality inspection, and scientific mold maintenance. Integrating these links enables consistent production of high-quality custom plastic parts meeting customer needs.