Delrin (Acetal / POM)
Injection Molding | Good optical properties, scratch resistant, glossy
Introduction
POM (Polyoxymethylene) is an engineering thermoplastic with high impact and temperature resistance. Also known as acetal or Delrin, POM has excellent dimensional stability and high stiffness.
Applications: Pumps, gears, conveyor links, soap dispensers, fan blades, switches, buttons, knobs.
Behavior: POM demands consistent wall thickness to avoid shrink, and the material is not receptive to painting or coating. It can be machined with greater ease.
| Properties | Metric | |
|---|---|---|
| Density | 1.01 – 1.20 g/cc | 0.0365 – 0.0434 lb/in³ |
| Hardness | 68 – 113 | 68 – 113 |
| Tensile Strength (Yield) | 13.0 – 65.0 MPa | 1890 – 9430 psi |
| Tensile Strength (Ultimate) | 22.1 – 49.0 MPa | 3210 – 7110 psi |
| Elongation at Yield | 0.62 – 30 % | 0.62 – 30 % |
| Elongation at Break | 3.0 – 150 % | 3.0 – 150 % |
| Dielectric Strength | 18.0 – 50.0 kV/mm | 457 – 1270 kV/in |
| Melt Temperature | 180 – 274 °C | 356 – 525 °F |
Design Guideline
Wall Thickness
Between 1 mm and 3 mm
Keeping walls as thin and constant as possible will reduce warping and sinking
Thickness gradient
Wall thickness should increase by no more than three times
Transition between thicknesses can be made smoother with fillets
Internal edges
Rounded, more than half wall thickness
Add fillet with largest possible radius
External edges
Rounded, full wall thickness plus internal fillet
Add fillet with largest possible radius
Draft angle
Increase draft by 1° for every 25 mm (for parts taller than 50 mm)
Add draft to ease ejection and avoid drag marks
Textured finish
Increase draft angle by 1-2°
Increase draft to ease ejection and avoid drag marks
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