POM (acetal, Delrin): density, print temperature and when to choose it
POM (polyoxymethylene, better known by the trade name Delrin) is a crystalline acetal plastic with an exceptionally low coefficient of friction and high wear resistance — the standard choice for injection-molded gears and plain bearings. It's not simple in FDM: strong crystallization shrinkage and near-zero adhesion to most beds and adhesives make it one of the fussiest materials in the catalog, despite its modest print temperatures.
Key properties
| Parameter | Value |
|---|---|
| Density | ≈1.41 g/cm³ |
| Nozzle temperature | 200–230°C |
| Bed temperature | 0–60°C (heating barely helps adhesion) |
| Part cooling | moderate |
| Shrinkage | high, crystallization-driven |
| Enclosure required | recommended, for even cooling |
When to use it
- Gears, gear racks, and bushings where low friction without lubrication matters.
- Moving mechanical joints running dry — POM slides where other plastics need lubrication.
- Replacing bronze or brass plain bearings in lightweight mechanisms.
- Button, latch, and mechanism parts that need stable geometry through repeated cycling.
When to pick something else
- You need reliable bed adhesion without special substrates — POM prints poorly even with BuildTak-like surfaces; for a less fussy alternative with similar wear resistance, look at PA6 or PA12.
- Impact-load resistance is needed — POM is more brittle than nylon; for impact risk, PA6-GF or Nylon is better.
- The part doesn't need low friction — don't pay extra for POM; plain PETG or ABS handles it more simply and cheaply.
Pros and cons
Pros: exceptionally low coefficient of friction without lubrication, high wear resistance and geometric stability of moving parts, good fatigue strength in bending (a classic material for snap-fits).
Cons: barely adheres to the bed — printing often needs special adhesive substrates or PEI sheets with texture; strong shrinkage, large flat parts are prone to corner lift; limited color and manufacturer choice; glues and welds poorly during post-processing.
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The main cost driver when printing POM isn't energy (print temperatures are fairly modest, and a heated bed isn't mandatory), but defects: weak adhesion means some prints detach or warp before completing, especially on large flat bases. Budget this into your cost through a higher failure rate and consumption of adhesive substrates/special bed coatings, which wear out faster for POM than for most other materials.