POM CNC Machining Service

Why Choose POM

Best-in-Class Dimensional Stability Among Commodity Plastics

POM absorbs very little moisture (0.2% at saturation) — unlike nylon, which can absorb 2–8% and change dimensions significantly. For precision parts that must maintain tolerances in humid or wet environments, POM is the correct choice.
Low Friction and Self-Lubricating

POM's low surface energy makes it naturally slippery — gears, cams, bearings, and sliding parts run with low friction and minimal wear without added lubricant. This is why POM dominates precision mechanical components in food processing, medical devices, and consumer products.
Excellent Fatigue Resistance

POM withstands cyclic loading without fatigue failure — critical for snap-fit connectors, living hinges, and parts that flex repeatedly. It is the standard material for precision snap-fit components in consumer electronics and medical devices.
Chemical Resistance

POM resists fuels, solvents, oils, and most cleaning chemicals — suitable for fuel system components, fluid handling parts, and parts cleaned with industrial solvents. Not suitable for strong acids or bases.
Easy and Predictable Machining

POM machines cleanly with good chip formation, predictable tool wear, and consistent dimensional results. It holds tolerance well and produces good surface finish at moderate cutting speeds.

Common POM Grades

POM Homopolymer (Delrin)

Slightly higher strength, hardness, and fatigue resistance than copolymer. Better surface finish on machined parts. The standard choice for precision mechanical components.

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POM Copolymer

More chemically resistant than homopolymer, especially to alkaline environments. Better for thick sections (no centerline porosity). Lower strength and hardness than homopolymer.

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Our Machining Capability

POM is one of our most frequently machined plastics. It machines cleanly on CNC lathes and machining centers with carbide tooling. Tolerances held to ±0.02 mm on precision features. POM's low moisture absorption means parts hold their machined dimensions in service — what you verify at inspection is what the customer installs.
Limitations & Cost Considerations

POM is not suitable for alkaline environments (copolymer grade is better than homopolymer, but neither is suitable for strong alkalis). POM is also not suitable for elevated temperatures above ~90–100°C continuous — at higher temperatures, PEEK or PPS is required. POM is flammable and does not pass UL94 V-0 rating in standard grades — flame-retardant grades are available but uncommon. POM cannot be solvent-bonded or painted easily — mechanical fasteners or press-fit inserts are the standard assembly method.

FAQ

What is the difference between Delrin and acetal copolymer?

Delrin is DuPont's brand name for POM homopolymer — it has slightly higher strength, hardness, and fatigue resistance, and produces better surface finish on machined parts. Acetal copolymer has better chemical resistance (especially to alkalis), no centerline porosity in thick sections, and slightly lower mechanical properties. For most precision mechanical parts, Delrin homopolymer is the standard choice. For thick sections or alkaline environments, copolymer is preferred.
Can POM replace metal in bearing and gear applications?

Yes, for many low-to-medium load applications. POM gears run quietly, resist corrosion, and operate without lubrication in environments where metal gears would require sealing and maintenance. Limitations: POM has lower load capacity than metal, lower temperature resistance, and is not suitable for very high-speed or high-load gear applications. For moderate loads, speeds up to ~3 m/s, and temperatures below 90°C, POM is an excellent metal replacement.
What tolerances can you hold on POM parts?

±0.02 mm on precision-machined POM features — better than most other plastics due to POM's low moisture absorption and good dimensional stability. For bore diameters and shaft ODs on precision rotating components, ±0.01 mm is achievable on specific features with care.
How does POM compare to nylon for precision mechanical parts?

POM is the better choice when dimensional stability and moisture resistance are the priorities. Nylon absorbs 2–8% moisture by weight depending on grade, which causes significant dimensional change in humid environments. POM absorbs only 0.2% — its dimensions are stable in both dry and wet conditions. For gears and bearings where fit and backlash must be consistent regardless of humidity, POM is correct. Nylon's advantage is better impact resistance and higher continuous use temperature (up to 120°C for PA66 vs. 90°C for POM).