Can you injection mold delrin?

Yes, Delrin (acetal/POM) is actually one of the best thermoplastics for injection molding. Here's what you need to know:

Why Delrin molds well

It has a sharp melting point (~175°C), low melt viscosity, and excellent flow characteristics, which means it fills mold cavities cleanly and releases easily. It also has very low moisture absorption, so no pre-drying is needed before molding.

Key processing parameters

• Melt temperature: 200–230°C

• Mold temperature: 60–100°C (higher = better surface finish and less warpage)

• Injection pressure: 70–140 MPa

• Shrinkage: 1.8–2.5% — notably high, so molds must be designed with this in mind

• Drying: generally not required, but 2–4 hrs at 80°C is recommended if material has been exposed to humidity

Design considerations

• Wall thickness: 1.5–3mm ideal; uniform walls are critical due to high shrinkage

• Draft angles: minimum 1°, 1.5–2° preferred — Delrin has low friction so ejection is usually clean

• Gate location: matters more than with many plastics; avoid jetting by gating into thick sections

• Weld lines: Delrin weld lines can be weak — design to minimise them in load-bearing areas

• Avoid sharp internal corners — stress concentration cracks easily in acetal

Watch out for

• Formaldehyde off-gassing at elevated temperatures — good ventilation is essential

• Shrinkage variation between Delrin homopolymer (DuPont) and copolymer acetals (e.g. Celcon) — they behave slightly differently in the mold

• Incompatibility with PVC — if both are processed on the same machine without thorough purging, the combination can decompose violently

Where it excels as a molded part

Gears, bearings, bushings, snap-fit clips, valve components, and any part needing low friction + high stiffness without lubrication. It's a true engineering-grade material in molded form.