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Plastic Injection Molding Tolerance Standards
Here is a comprehensive and structured plastic injection molding tolerance standards chart, covering material types, dimensional ranges, and industry standards (ISO, DIN, ASTM) for your reference.
Plastic Injection Molding Tolerance Standards |
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| Tolerance Type | Size Range (mm) | Amorphous (ABS, PC) ±mm | Semi-Crystalline (PP, PA) ±mm | High-Precision (LCP, PEEK) ±mm | Standard Reference | Application Examples |
| General Linear Dimensions | 0–50 | 0.10–0.20 | 0.15–0.30 | 0.05–0.15 | ISO 20457 (Class 4) | Housings, structural parts |
| 50–100 | 0.20–0.30 | 0.30–0.50 | 0.10–0.20 | DIN 16901 | Appliance components | |
| 100–200 | 0.30–0.50 | 0.50–0.80 | 0.20–0.30 | ASTM D955 | Automotive interiors | |
| Hole Diameter Tolerance | 1–10 | 0.05–0.10 | 0.08–0.15 | 0.03–0.08 | ISO 286-2 | Assembly holes, locating pins |
| 10–20 | 0.10–0.15 | 0.15–0.25 | 0.08–0.12 | Connector interfaces | ||
| Wall Thickness Tolerance | 1–3 | ±0.10 | ±0.15 | ±0.05 | SPI Mold Class 101 | Thin-walled containers |
| 3–6 | ±0.15 | ±0.20 | ±0.10 | Ribs/reinforcements | ||
| Flatness/Planarity | 100×100 | 0.20–0.40 | 0.30–0.60 | 0.10–0.25 | GD&T (ISO 1101) | Sealing surfaces, cosmetic panels |
| Concentricity/Runout | Ø10–50 | 0.05–0.15 | 0.10–0.20 | 0.03–0.08 | ISO 2768-mK | Gears, bearing housings |
Material Shrinkage vs Tolerance |
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| Material Type | Shrinkage (%) | Tolerance Multiplier | Notes |
| ABS | 0.4–0.7 | 1.0× | Low shrinkage, precision-friendly |
| PP | 1.0–2.5 | 1.5–2.0× | High shrinkage, post-mold compensation |
| POM (Acetal) | 1.5–2.5 | 1.8× | Moderate dimensional stability |
| PEEK | 0.1–0.5 | 0.7× | Ultra-low shrinkage, aerospace/medical |
Mold Class & Tolerance Capability (SPI Standard) |
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| Mold Class | Tolerance Range ±mm | Cost | Typical Applications |
| Class 101 | 0.02–0.05 | Very High | Optical lenses, micro-connectors |
| Class 201 | 0.05–0.10 | High | Medical devices, electronic housings |
| Class 301 | 0.10–0.20 | Moderate | Appliances, automotive functional parts |
| Class 401 | 0.20–0.50 | Low | Packaging, low-precision components |
Process Control Impact on Tolerances |
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| Process Parameter | Tolerance Optimization | Control Recommendations |
| Mold temp. ±5°C | 10–15% lower shrinkage variation | Use thermostatic mold controllers |
| Holding pressure ±10% | 20% better repeatability | Closed-loop pressure feedback systems |
| Cooling time ±1s | 0.05mm less warpage | Standardized cooling channel design |
| Automotive (ISO 3302) | ||
| Feature | Tolerance ±mm | Material Examples |
| Interior assembly gaps | 0.15–0.30 | PP+TD20, ABS/PC |
| Engine bay components | 0.10–0.25 | PA66-GF30, PPS |
| Medical (ISO 13485) | ||
| Feature | Tolerance ±mm | Key Standard |
| Microfluidic channels | ±0.02 | USP Class VI |
| Surgical connectors | ±0.05 | FDA 21 CFR Part 820 |
| Electronics (EIA-364) | ||
| Feature | Tolerance ±mm | Test Conditions |
| Terminal pitch | ±0.03 | 23°C, 50% RH |
| Housing fit clearance | ±0.05 | Insertion force ≤5N |
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