Acetal vs UHMW: precision or wear resistance?
The short answer: acetal (POM) is the material for parts that must hold dimension and transmit load; UHMW polyethylene (UHMWPE) is the material for parts that exist to take abrasion, sliding wear and impact. They are rarely interchangeable, and choosing the wrong one is a common cause of early replacement.
At a glance
| Property | Acetal (POM) | UHMW (UHMWPE) |
|---|---|---|
| Strength & stiffness | High — rigid, resists creep | Low — flexes, and creeps under sustained load |
| Abrasion resistance | Good | Outstanding — among the best of any thermoplastic |
| Impact resistance | Good | Exceptional, and retained at low temperature |
| Friction | Low — typically 0.2–0.35 against steel | Very low — typically 0.10–0.20, with a non-stick surface |
| Temperature | To roughly 90–100 °C continuous | To around 80 °C continuous |
| Moisture | Very low uptake (about 0.2%) | Effectively zero |
| Machining & tolerance | Excellent — holds tight tolerance | Machinable, but softness and high thermal expansion mean looser practical tolerances |
| Food contact | Food-contact grades available | Food-contact grades widely used |
| Relative material cost | Moderate | Generally lower |
Figures are typical values for unfilled grades and vary by grade and manufacturer — confirm against the supplier datasheet for a critical application.
Where acetal is the better choice
Choose acetal for parts that must hold dimension and transmit load: precision gears, cams, bushes, spacers, and threaded or snap-fit features. It is rigid, resists creep and machines to tight tolerance, so it behaves like a precise mechanical component rather than a wear surface.
Where UHMW is the better choice
Choose UHMWPE where product or a mating part slides, rubs or strikes against the component: chute and hopper liners, chain and belt guides, wear strips, star wheels and impact pads. Its abrasion and impact resistance are in a different class from acetal, its surface sheds sticky product, and it is quiet in running contact — which is why it is so common on conveying and food-handling lines.
The common mistake
UHMWPE is sometimes specified for a precision part because of its wear performance, and then disappoints: it is soft, moves with temperature more than acetal does, and relaxes under a sustained clamp or press-fit load. If the drawing carries a tight tolerance or the part locates something else, acetal is normally the safer specification. If the part exists to take wear, UHMWPE is.
How to decide
- Tight tolerance, press fits, threads or gear teeth under load? Acetal.
- Sliding or abrasive contact with product, chain or belt? UHMWPE.
- Repeated impact, or service in cold rooms and freezers? UHMWPE.
- Sustained duty above about 80 °C? Acetal — or a different material if it runs much hotter.
Related comparisons
Final material suitability depends on the component drawing, load, speed, operating temperature, chemical exposure, food-contact requirements, wear conditions and validation. Tell us the position the part runs in and we will manufacture to the grade your drawing specifies — or discuss the material if the drawing leaves it open. See the full materials list for designations and characteristics.
Not sure which grade suits your part? Send the drawing and we’ll advise.
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