Definition of Acetal Homopolymer (POM-H)
POM-H, also known as acetal homopolymer and sold under the brand name Delrin, is a strong engineering plastic. It is slightly stiffer and harder than POM-C copolymer, with higher tensile strength and better fatigue resistance. It is self-lubricating, low-friction, and wears well. CNC shops machine it into gears, bearings, bushings, valve parts, and precision mechanical components. It is naturally white, holds tight tolerances, and is widely used in automotive, electronics, and industrial machinery.
Properties of Acetal Homopolymer (POM-H)
| Property | Value |
|---|---|
| Mechanical Properties | |
| Ultimate tensile strength | 60 – 89.6 MPa |
| Yield strength | 48.6 – 72.4 MPa |
| Young’s modulus (modulus of elasticity) | 2.5 – 4 GPa |
| Elongation at break | 15 – 75 % |
| Hardness | 14.6 – 24.8 HV |
| Physical Properties | |
| UV resistance | Poor |
| Thermal Properties | |
| Maximum service temperature | 76.9 – 96.9 °C |
| Thermal expansion coefficient | 75.7 – 202 × 10-6/ºC |
| Thermal conductivity | 0.221 – 0.35 W/(m⋅°C) |
| Electrical Properties | |
| ESD Safety | Yes |
| Common Applications | |
| Gears & Bearings | Electrical applications |
| Pump and valve components | |
Why Acetal Homopolymer (POM-H) Matters in CNC Workshops
- High-strength plastic demand: Customers needing stronger than POM-C choose POM-H. It is the go-to material for load-bearing gears, springs, and snap-fit parts that must not break.
- Premium brand recognition: Delrin is a trusted name. Customers specifically ask for it by name, which means you can charge more and compete less on price.
- Excellent fatigue resistance: POM-H parts survive millions of cycles. This makes it ideal for moving parts, repeat customers, and long-term replacement orders.
- Fast, clean machining: POM-H cuts sharply, holds tight tolerances, and produces a smooth finish. Low scrap rates and quick cycle times keep your shop profitable.
Surface Finishes for Acetal Homopolymer (POM-H)
As-Machined
The default finish from CNC machining plastic stock (Delrin, nylon, HDPE, ABS). Visible linear tool path scallop marks across machined surfaces with a matte plastic sheen. No secondary operation suitable for functional components, jigs, fixtures, and internal parts where cosmetic appearance is secondary to dimensional accuracy.
Flame Polished
Quick post-fabrication process that passes a controlled flame over acrylic (PMMA) cut edges, melting the surface micro-layer to produce a crystal-clear, glossy, transparent edge. Fast and cost-effective for acrylic sheet edges produces optical clarity on cut borders without the labor of hand polishing. Ideal for display cases, signage, and acrylic enclosures.
Vapor Polished
Post-fabrication chemical process that exposes transparent plastic parts (acrylic, PC, PETG) to solvent vapor, melting and smoothing the surface micro-layer to dramatically improve optical clarity and gloss. Removes machining lines and produces crystal-clear transparent parts — essential for prototype lenses, light guides, display windows, fluidic chambers, and medical components requiring optical transparency.
Painted
Post-fabrication spray painting in any custom color (matte, satin, gloss, metallic) followed by screen printing or pad printing for logos, labels, buttons, and graphics. Applied over a primed plastic surface for uniform color and adhesion. Allows custom fabricated plastic parts to match production aesthetics widely used for control panels, instrument faces, enclosures, and marketing/showcase components requiring exact brand color and graphic printing.
Sanded
Post-fabrication sanding with progressively finer grit sandpaper (typically 240–600 grit) produces a uniform low-gloss matte non-reflective surface. Hides machining marks, scratches, and surface inconsistencies while providing a soft tactile feel. Used for HDPE, UHMW, and nylon components where a durable, non-glare, fingerprint-resistant matte appearance is desired for industrial and functional parts.
Heat Formed
Thermoforming process that heats plastic sheet (acrylic, polycarbonate, ABS) to its glass transition temperature and bends it over a form tool to create precise angles and curved shapes. Produces clean, smooth bend radii with consistent surface finish no tool marks at the bend. Used for display stands, guards, enclosures, signage, and custom fabricated parts requiring 3D formed shapes from flat sheet stock.
