Material Reference
Processing data and selection guidance for common injection molding plastics.
Processing reference
| Material | Cavity Pressure (psi) | Recommended (psi) | Shrinkage (%) | Mold Temp (°C) | Melt Temp (°C) | Drying Required? |
|---|---|---|---|---|---|---|
| Acrylonitrile Butadiene Styrene (ABS) | 8,000 – 12,000 | 10,000 | 0.4 – 0.8 | 40 – 80 | 210 – 250 | Yes (2-4 hrs @ 80°C) |
| Nylon (PA6 / PA66) | 10,000 – 15,000 | 12,000 | 0.8 – 1.5 | 60 – 100 | 240 – 290 | Yes (4-6 hrs @ 80°C) |
| High Density Polyethylene (HDPE) | 6,000 – 10,000 | 8,000 | 1.5 – 4.0 | 20 – 60 | 180 – 240 | No |
| Low Density Polyethylene (LDPE) | 5,000 – 8,000 | 6,500 | 1.5 – 5.0 | 20 – 50 | 160 – 220 | No |
| Polycarbonate (PC) | 10,000 – 15,000 | 12,000 | 0.5 – 0.7 | 70 – 110 | 270 – 310 | Yes (3-4 hrs @ 120°C) |
| Polyoxymethylene (POM / Acetal) | 10,000 – 14,000 | 12,000 | 1.5 – 2.5 | 60 – 100 | 180 – 210 | Yes (2-4 hrs @ 80°C) |
| Acrylic (PMMA) | 8,000 – 12,000 | 10,000 | 0.2 – 0.6 | 40 – 80 | 220 – 260 | Yes (3-4 hrs @ 80°C) |
| Thermoplastic Polyurethane (TPU) | 6,000 – 10,000 | 8,000 | 0.5 – 1.5 | 20 – 40 | 180 – 230 | Yes (2-4 hrs @ 80°C) |
| Thermoplastic Rubber (TPR/TPE) | 5,000 – 8,000 | 6,500 | 1.0 – 3.0 | 10 – 40 | 170 – 220 | Yes (2-3 hrs @ 60°C) |
| Polypropylene (PP) | 6,000 – 10,000 | 8,000 | 1.0 – 2.5 | 20 – 60 | 200 – 250 | No |
| Rigid PVC (Unplasticized) | 8,000 – 12,000 | 10,000 | 0.2 – 0.5 | 20 – 50 | 190 – 210 | No (but surface moisture causes splay) |
| Flexible PVC (Plasticized) | 6,000 – 10,000 | 8,000 | 0.5 – 1.5 | 15 – 40 | 170 – 200 | No (but check plasticizer stability) |
Selection guide
| Material | Best For | Key Mold Design Consideration |
|---|---|---|
| ABS | Automotive, consumer goods, housings | Good flow, easy to plate/paint — use medium gates |
| Nylon | Gears, bearings, structural parts | Hygroscopic — must dry! High shrinkage = design oversize |
| HDPE / LDPE | Containers, toys, flexible parts | High shrinkage — use larger draft angles (2-3°) |
| Polycarbonate (PC) | Transparent parts, lenses, guards | High melt temp — use hot runner and corrosion-resistant steel |
| POM (Acetal) | Gears, snap-fits, precision parts | Excellent creep resistance — sharp corners cause stress |
| Acrylic (PMMA) | Lenses, displays, transparent covers | Notch-sensitive — avoid sharp edges! Use large radius |
| TPU / TPR | Soft-touch grips, seals, gaskets | Low melt temp — use cold runner to avoid drooling |
| Polypropylene (PP) | Living hinges, containers, automotive | Great for living hinges — but high shrinkage, design for it |
| Rigid PVC | Pipes, fittings, profiles | Corrosive (HCl gas) — use 420SS or H13 with corrosion coating |
| Flexible PVC | Gaskets, seals, tubing | Plasticizers degrade at high shear — use large gates |