POM (Acetal) for CNC Machining: Everything to Know

Polyoxymethylene (POM), commonly known as Acetal, is a highly versatile engineering plastic renowned for its excellent mechanical properties and ease of machining. It is widely used in various industries, such as automotive, consumer products, and medical devices, due to its high strength-to-weight ratio, low friction, and high chemical resistance. This guide will explore the different grades of POM, its properties, applications, advantages, disadvantages, and machining characteristics using CNC technology.

Understanding the different grades of POM is essential for selecting the right material for your POM CNC machining projects. Each grade has distinct properties that make it suitable for specific applications.

Homopolymer Acetal, often referred to as POM-H, offers higher mechanical strength and rigidity compared to copolymer grades. It also has a lower coefficient of friction, making it ideal for applications that require excellent wear resistance and low friction. CNC machining of POM-H is often used for precision parts like gears, bearings, and valve components where high dimensional stability and strength are crucial.

POM-C provides better resistance to hot water, chemicals, and creep deformation. It has slightly lower mechanical strength than homopolymer Acetal but offers superior dimensional stability and resistance to hydrolysis, making it ideal for applications in wet environments, such as pump components and food processing equipment.

Filled Acetal grades are reinforced with various fillers like glass fibers or PTFE to enhance specific properties such as stiffness, strength, or wear resistance. These grades are suitable for CNC milling where high mechanical properties are needed, such as in automotive parts and industrial machinery components..

Reinforced Acetal is modified with additives to improve mechanical properties like impact strength and rigidity. This grade is typically used in applications requiring higher strength and stiffness, making it ideal for heavy-duty mechanical parts such as load-bearing structural components and gears.

POM is known for its excellent combination of physical, mechanical, electrical, and chemical properties, making it a preferred choice for many CNC machining applications.

Density: POM has a moderate density, contributing to its high strength-to-weight ratio, ideal for lightweight yet durable components.
Water Absorption: POM exhibits low water absorption, ensuring it maintains its mechanical properties and dimensional stability in moist or wet environments.
Thermal Expansion: With a relatively low coefficient of thermal expansion, POM helps maintain tight tolerances in precision parts over various temperatures

Tensile Strength: POM offers high tensile strength, suitable for applications requiring strong and durable materials.
Flexural Strength: It has good flexural strength, providing excellent resistance to bending and deformation under load.
Impact Resistance: Known for its high impact resistance, POM can withstand sudden shocks and loads without cracking or breaking

Dielectric Strength: POM provides good dielectric strength, making it suitable for electrical insulation applications.
Volume Resistivity: The material has high volume resistivity, which ensures it does not conduct electricity, ideal for insulating components.

Chemical Resistance: POM is resistant to a wide range of chemicals, including fuels, oils, solvents, and alkalis, making it suitable for use in chemical processing environments.
Flammability: POM has moderate flammability and is not self-extinguishing, so it should not be used in applications where exposure to open flames or high temperatures is expected​.

POM’s unique properties make it suitable for a variety of applications across different industries.

Gears: POM’s low friction and high wear resistance make it ideal for manufacturing gears used in various machinery and equipment.
Bearings: Its high strength and low friction characteristics are perfect for producing bearings that operate smoothly and efficiently.
Pump Components: POM is often used in pump components due to its chemical resistance and ability to maintain performance in wet environments​

Zippers: The material’s durability and low friction make it ideal for zippers in clothing, luggage, and outdoor gear.
Buckles: POM’s strength and resistance to impact make it a popular choice for buckles used in safety equipment and outdoor gear.
Fasteners: POM is used in fasteners due to its high strength-to-weight ratio and resistance to chemicals and wear​

Medical Implants: POM’s biocompatibility and resistance to chemicals make it suitable for certain medical implants.
Surgical Instruments: The material’s ease of machining and sterilization makes it ideal for surgical instruments and other medical devices.
Medical Devices: POM is often used in various medical devices due to its strength, durability, and resistance to repeated sterilization processe

POM offers several advantages that make it an excellent choice for CNC machining:

High Strength-to-Weight Ratio: POM provides a strong and durable material that is also lightweight, suitable for applications where weight is a concern.
Low Friction: The material’s low friction coefficient makes it ideal for components that require smooth operation and minimal wear.
High Chemical Resistance: POM’s resistance to a wide range of chemicals makes it suitable for use in harsh chemical environments.
Easy to Machine: POM is easily machinable, allowing for precise and complex components to be produced with high accuracy​.

Sensitive to UV Light: POM can degrade when exposed to UV light for extended periods, so it is not suitable for outdoor applications without proper UV stabilization.
Prone to Cracking: The material can crack under high stress or impact, particularly in thin sections or sharp corners.
Limited High-Temperature Resistance: POM has a relatively low melting point and can deform or degrade when exposed to high temperatures for prolonged periods​.

Machinability: POM can be easily machined with standard tools, providing excellent surface finishes and maintaining tight tolerances.
Excellent Surface Finish: The material allows for smooth, polished surfaces with minimal post-processing required.
Low Cutting Forces: POM requires low cutting forces during machining, reducing tool wear and extending the lifespan of cutting tools.
Minimal Burr Formation: Machining POM typically results in minimal burr formation, reducing the need for extensive deburring and finishing operations。

POM (Acetal) is an outstanding material for CNC machining due to its excellent combination of mechanical properties, chemical resistance, and ease of machining. Whether you are producing gears, bearings, medical devices, or consumer products, POM provides the durability, precision, and performance needed for a wide range of applications. However, understanding its limitations, such as sensitivity to UV light and limited high-temperature resistance, is crucial for selecting the right material for your specific needs.

For high-quality CNC machining of POM and other engineering plastics, consider partnering with AstroCNC. Our advanced machining capabilities and expertise ensure precise, reliable, and cost-effective solutions for your manufacturing needs. Contact us today to learn more about how we can support your next project.