POM (Acetal/Delrin)

CNC Machining / Light Weight + Corrosion Resistance

Home Resources Materials POM (Acetal/Delrin)

Introduction

POM (Polyoxymethylene) is an engineering thermoplastic material that demonstrates excellent dimensional stability, stiffness and impact and temperature resistance. The material, also known as acetal or Delrin, can be produced two ways: as a homopolymer or as a copolymer.

POM materials are commonly used in the fabrication of pipe components, gear bearings, household appliances, automotive parts, consumer electronics and more.

Surface Finish

Bead blasting

Bead blasting results in parts with a smooth surface with a matte texture. Used mainly for visual applications and can be followed by other surface treatments.

Manufacturability

Tolerance

- Standard: (+/-) 125 µm -Achievable: (+/-) 100 µm , (+/-) 50 µm

Wall Thickness

- The minimum wall thickness should be at least 1 mm for machined parts. - 2 mm is suggested for better strength and 2.5 mm for a rigid wall.

Pocket depth

- Pocket depth should be up to 3 times the diameter of the end mill

Engraving

- Engraving is preferable to embossing - For the clear, legible text consider fonts such as Arial or Gothic - Design letter strands with a width of at least 2 mm

Internal Radii

- The minimum internal radii possible is 1 mm - In general, internal radii dimensions depend on the depth of pocket being milled

Holes

- Use standard drill bit sizes - Minimum of 1 mm in diameter

Threads

- Use standard metric inserts - Smallest threaded insert possible is M2

Design Recommendations

Min Wall Thickness

0.5 mm

Min End Mill Size

0.8 mm (0.03 in)

Min Drill Size

0.5 mm (0.02 in)

Max Part Size

1200 x 500 x 152 mm [(x,y,z] (mill) 152 x 394 mm [d,h] (lathe)

Undercuts

Square profile, full radius, dovetail profiles

Radii : Depth

Depth must not exceed 12x drill bit diameter. For endmills, depth must not exceed 10x drill bit diameter.

Engineer's Pro Tips

POM is a versatile and popular plastic in the engineering sector. Its high stiffness and hardness (with a Rockwell hardness of up to D80-85Z) make it a suitable alternative to certain metals, including ordinary carbon steel.
In addition to hardness, POM has other properties that make it ideal for replacing metals. For example, it has insulation and wear resistance properties comparable to those of certain carbon steels.
Generally, POM has good processing characteristics. However, it does demonstrate a high shrinkage rate (2% to 3.5%) and has poor corrosion resistance.
Its elasticity can also result in deformation during the machining process caused by clamping or overheating. POM is also not conducive to polishing (the surface turns white) and cannot be plated or disassembled.