A Guide to POM (Polyoxymethylene) CNC Machining: Properties, Types, and Applications

Key Takeaways

1. POM's excellent self-lubricating properties and wear resistance make it a strong choice for sliding components.

2. POM machines cleanly with minimal burring—and any burrs that do form are easy to remove.

3. Standard-grade POM has poor weather resistance and is not recommended for outdoor use.

Overview

POM (polyoxymethylene) is an engineering plastic recognized for its excellent mechanical strength, wear resistance, and chemical resistance. It machines cleanly with minimal burring—and any burrs that form are easy to remove—making it suitable for a wide range of industrial applications.

POM is a crystalline thermoplastic resin made up primarily of repeating (-CH₂O-) units. There are two main types: homopolymer, which is formed from molecular chains of polyoxymethylene linked by formaldehyde, and copolymer, which is made by combining trioxane (a formaldehyde trimer) with ethylene oxide or other monomers.

Well-known examples include DuPont’s Delrin® for homopolymer and Polyplastics’ Duracon® for copolymer.

Homopolymer (e.g., DuPont’s Delrin®)

• Formed entirely from identical monomer units.

• Its main chain is formed solely from carbon-oxygen bonds.

• Offers slightly higher crystallinity, strength, and rigidity.

Copolymer (e.g., Polyplastics’ Duracon®)

• A copolymer is a polymer made from different types of monomer units, most commonly two types.

• Exhibits better thermal stability and less degradation during molding.

• Lower crystallinity than homopolymers, resulting in improved flexibility but slightly reduced strength.

• Melting point and heat deflection temperature are about 10 °C lower than homopolymers, but practical heat resistance is largely equivalent.

Key Properties

• High mechanical strength, wear resistance, and chemical resistance

• Naturally self-lubricating with a low coefficient of friction, ideal for sliding parts

• Continuous service temperature for homopolymers: 85 °C

• Continuous service temperature for copolymers: 105 °C (can withstand short-term exposure up to approximately 150 °C)

• Excellent dimensional stability (low moisture absorption)

• Easy to machine with minimal burr formation (even if burrs form, they are easy to remove)

• Makes POM ideal for precision parts, including components with small holes

POM Material Properties

Material Selection Considerations

• Not suitable for strong acids (e.g., hydrochloric acid, sulfuric acid).

• Poor bonding properties: adhesives are generally ineffective.

• Low weather resistance: prolonged outdoor use may cause discoloration or degradation.

• Flammability: burns with a blue flame and formaldehyde odor, making it unsuitable for use near open flames.

Standard-grade POM has poor weather resistance and is not suitable for outdoor applications. While it is slow-burning, its oxygen index of 15 means it is still flammable, so it should not be used in environments with open flames or significant heat sources.

Although POM generally has low water absorption, some grades can actually absorb more moisture than expected. For example, the high-load sliding grade POM SW-01 has a water absorption rate of 0.6%, while the MC Nylon sliding grade MC703HL sits at 0.5%, meaning the POM grade absorbs slightly more in this case.

Since physical properties can vary between grades, always consult the latest material data sheet from the manufacturer when finalizing your material selection. This will help ensure the best possible match for your specific application.

Typical Applications

• Automotive parts (e.g., fuel pump components)

• Bearings and sliding components

• Gears, pulleys, and switches

• Precision machine parts

• Consumer goods and everyday items

Grades of POM

Beyond the standard grade, POM is available in a range of specialty grades with enhanced properties:

• Standard Grade

• UV-Resistant Grade

• Low-Friction / Sliding Grade

• Glass Fiber Reinforced Grade

• Medical Grade

• Carbon Fiber Reinforced (Conductive) Grade

• High-Load Sliding Grade

Available Colors & Sizes

Stock Colors

• Standard colors: White, Black, Yellow

Stock Sizes

• Round rods: φ4–φ250 mm

• Sheets/plates: Thickness from 0.2 mm up to 100 mm

Major Brands and Manufacturers

Development & Market Adoption

POM was first developed by DuPont in the early 1950s, with production beginning in 1960 under the trade name Delrin®. Soon after, other companies like Celanese (now Ticona) and Polyplastics introduced their own versions (e.g., Duracon®).

By the 1960s, POM’s high wear resistance made it a popular choice for bearings. Over time, its strength, self-lubricating properties, and affordability expanded its use into the following:

• Gears, screws, and fasteners

• Musical instruments (flutes, whistles)

• Electronics housings and modules

• Automotive components

Today, POM is a standard engineering plastic for applications requiring durability, strength, and precision.

POM CNC Machining at Yumoto Electric

Yumoto Electric manufactures custom POM machined parts starting from a single piece. We have experience with over 200 materials, including metals such as aluminum alloys, stainless steel, molybdenum, and titanium; and engineering plastics including PEEK, PPS, and MC Nylon.

If you’re unsure about material selection or machining methods, we offer complimentary consultations to help optimize your design and production. For any questions, please feel free to contact us.