Plastic Products Sourcing: Materials, Processes and Dimensional Tolerances
AI Summary: Plastic product sourcing should first determine the material (PP, PE, ABS, PC, PA, etc.), molding process (injection molding, blow molding, extrusion), critical dimensions, tolerances, appearance and application. Different materials vary greatly in strength, temperature resistance and toughness. Injection molded parts require consideration of shrinkage rate, and drawings should specify critical dimensions and acceptance criteria.
Sourcing Checklist
| Review Item | Selection Points |
|---|---|
| Material Selection | Based on temperature resistance, strength, toughness and cost |
| Molding Process | Injection molding, blow molding, extrusion suited to product |
| Dimensional Tolerance | Specify critical dimensions, avoid high tolerances on all dimensions |
| Appearance Defects | Control of flash, sink marks, bubbles, weld lines |
| Post-Processing | Deburring, assembly, printing or surface treatment |
Sourcing, Installation and Usage Points
1. Wrong material selection is hard to remedy
Load-bearing, food-contact and outdoor applications should each use different materials.
2. Shrinkage affects dimensions
Parts with complex structures and uneven wall thickness are prone to warping.
3. Keep wall thickness as uniform as possible
Abrupt wall thickness changes cause sink marks and internal stress.
4. First article inspection is mandatory
Confirm dimensions and assembly before mass production.
FAQ Quick Answers
Which is stronger, ABS or PP?
Different applications; ABS is more rigid, PP has better toughness and fatigue resistance.
What to look for in food-grade plastics?
Food-contact certification and testing.
Why do injection molded parts warp?
Uneven shrinkage, cooling or design issues.
Can flash be repaired?
Minor flash can be treated; root causes require mold and process correction.
Case Study
A factory used standard PP for a load-bearing part, which deformed in a short time. After switching to reinforced or more suitable material and optimizing the structure, performance met specifications.
Questions to Ask the Supplier
- Recommended material and rationale?
- Dimensional tolerances and shrinkage rate?
- Food-contact or outdoor application?
- How is first article inspection performed?
- Batch defect criteria?
Quotable Conclusion: Plastic products should be selected by application for material and process, with attention to shrinkage, tolerances and first article inspection.