Shrinkage rates, achievable tolerances, and certification compatibility — by material family. Tolerance is a function of material, geometry, and process — not a single number.
Achievable tolerance scales with shrinkage rate and crystallinity. Glass-fiber reinforcement moves a material up an entire tier of dimensional capability — but only if fiber orientation and gate location are controlled.
| Material | Shrinkage % | Standard Tol ± (mm) | Precision Tol ± (mm) | Key Notes |
|---|---|---|---|---|
| ABS | 0.4–0.8% | ±0.15 | ±0.10 | Amorphous, isotropic, predictable |
| PC | 0.5–0.8% | ±0.12 | ±0.10 | Best dimensional consistency, hygroscopic |
| PC/ABS | 0.5–0.7% | ±0.15 | ±0.10 | Amorphous, isotropic |
| PBT + 30% GF | Flow 0.2–0.3% / Cross 0.5–1.3% | ±0.12 | ±0.10 | Dimensionally stable, low moisture uptake |
| PA66 + 30% GF | Flow 0.2–0.6% / Cross 0.8–1.3% | ±0.12 | ±0.10 | Inspect after 48h conditioning at 23°C/50%RH |
| PA66 (unfilled) | 0.7–1.8% | ±0.16 | ±0.13 | Moisture swell dominates — conditioning mandatory |
| PA6 + 30% GF | Flow ~0.3% / Cross ~0.8% | ±0.12 | ±0.10 | More moisture-sensitive than PA66+GF |
| POM Copolymer | 2.0–2.5% | ±0.16 | ±0.13 | Post-mold shrinkage 24–72h; anneal for critical parts |
| PBT (unfilled) | 1.2–2.5% | ±0.16 | ±0.13 | Fast-crystallizing, stable after mold |
| PP | 1.0–3.0% | ±0.17 | ±0.11 | High variable shrinkage, anisotropic |
| PEEK (unfilled) | Flow 0.9–1.2% / Cross 1.3–1.6% | ±0.16 | ±0.10 | Mold ≥170°C required |
| LCP + 45% GF/MF | Flow 0.1–0.2% / Cross 0.3–0.5% | ±0.05–0.10 | ±0.02–0.05 | Ultra-precision possible; flow anisotropy suppressed by MF |
| PPS + 40% GF | Flow 0.2–0.3% / Cross 0.5–0.8% | ±0.12 | ±0.10 | Best long-term stability; mold ≥135°C |
| TPU | 0.5–1.5% | ±0.20–0.40 | ±0.10–0.20 | Shore-dependent; elastic recovery during ejection |
Tolerance scales with approximately 0.1–0.2% of nominal dimension for amorphous and fiber-filled resins, and 0.3–0.5% of nominal for unfilled crystalline resins. A 30% glass-fiber addition moves a part up an entire tolerance tier — but gate location and fiber orientation must be controlled or warpage erases the gain.
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