ABS vs POM vs Nylon: Which Plastic Is Best for CNC Machining?

ABS, POM (acetal/Delrin), and Nylon are three of the most widely used engineering plastics in CNC machining. Although they are often compared together, they actually serve very different engineering purposes due to differences in strength, rigidity, wear resistance, and machining behavior. Choosing the correct material is not only about cost, but also about functional performance, tolerance stability, and long-term reliability of the final component.

ABS (Acrylonitrile Butadiene Styrene) is considered one of the most machinable plastics in CNC manufacturing. It has a stable internal structure, which allows it to be cut smoothly without excessive tool wear or cracking. During machining, ABS produces relatively consistent chips and does not require highly specialized cutting conditions. Because of this, it is widely used in prototyping, appearance models, and non-functional parts where dimensional accuracy is required but mechanical load is low. ABS is also relatively inexpensive, which makes it attractive for early-stage product development and design validation.

However, ABS has clear limitations. Its mechanical strength is moderate, and its heat resistance is relatively low compared to engineering-grade plastics. When exposed to elevated temperatures or continuous stress, ABS can soften, deform, or lose dimensional accuracy. This makes it unsuitable for load-bearing applications, high-temperature environments, or precision mechanical assemblies. In addition, ABS has limited wear resistance, meaning it is not ideal for parts involving continuous friction or motion.

POM (Polyoxymethylene), also known as acetal or Delrin, is a high-performance engineering plastic widely used in precision CNC machining. One of its most important characteristics is excellent dimensional stability. Unlike many other plastics, POM does not easily absorb moisture or deform after machining, which ensures tight tolerances are maintained over time. This makes it highly suitable for precision components where accuracy is critical.

Another key advantage of POM is its extremely low coefficient of friction. This allows it to perform very well in moving mechanical systems without requiring additional lubrication. As a result, POM is commonly used in gears, bushings, rollers, conveyor parts, and sliding mechanisms. It also has excellent wear resistance, meaning it can handle continuous motion over long periods without significant degradation.

In addition, POM has relatively high stiffness compared to ABS, which improves its mechanical performance in functional applications. It also resists fatigue well, meaning it can endure repeated mechanical loading without cracking or failure. These properties make POM one of the most reliable materials for CNC-machined mechanical parts.

However, POM is not perfect. It has lower impact resistance compared to Nylon, and under certain conditions it may become brittle at very low temperatures. It is also slightly more expensive than ABS, although still considered cost-effective for engineering applications.

Nylon (PA6, PA66) is another widely used CNC machining material, known for its excellent toughness and impact resistance. Compared to ABS and POM, Nylon performs significantly better in applications involving mechanical stress, shock loading, and repeated deformation. It has high tensile strength and excellent fatigue resistance, making it suitable for structural components and industrial mechanical parts.

One of Nylon’s strongest advantages is its ability to absorb energy without breaking. This makes it ideal for gears, pulleys, bearings, and load-bearing supports. It also performs well in abrasive environments due to its good wear resistance.

However, Nylon has a major limitation: moisture absorption. Nylon is hygroscopic, meaning it absorbs water from the environment. When this happens, the material expands, which can affect dimensional accuracy and mechanical performance. In high-humidity environments, this can lead to part deformation or inconsistent tolerances. Therefore, Nylon is not recommended for high-precision applications unless environmental conditions are carefully controlled or accounted for in design.

Another factor to consider is that Nylon is more difficult to machine than ABS or POM. It tends to generate heat during cutting, which requires proper tool selection and machining parameters to avoid deformation.

In conclusion, ABS is best suited for prototypes and non-functional components due to its low cost and ease of machining. POM is ideal for precision mechanical parts requiring stability, low friction, and wear resistance. Nylon is the best choice for high-strength, impact-resistant applications where dimensional accuracy is less sensitive to environmental changes.