If engineers want to make low-volume production parts or high-quality prototypes, they need to choose the correct plastic for CNC machining. With an emphasis on plastics' characteristics, uses, and compatibility with CNC machining methods, this all-inclusive reference will lead you through the maze of plastics. In this article, we will help you optimize your material selection for CNC machining projects by exploring important elements to consider, comparing popular possibilities, and providing insights. With the information in this book, CNC machining professionals in the automotive, medical, aerospace, and consumer electronics industries may make educated selections when selecting plastic injection molding materials.
Understanding Plastic Properties for CNC Machining
Mechanical Properties of Plastics
It is crucial to know the mechanical characteristics of plastics before choosing them for CNC machining. The material's performance under different situations and stresses is determined by these qualities. The ability of a material to resist breaking under strain is known as its tensile strength, and its ability to absorb shock without fracturing is known as its impact resistance. Both of these mechanical properties are crucial. A material's flexural modulus, or its capacity to be bent without breaking, is an additional important attribute to consider. For instance, ABS (Acrylonitrile Butadiene Styrene) offers excellent impact resistance and dimensional stability, making it suitable for automotive parts and consumer electronics housings.
Thermal Properties and Their Impact
Thermal properties play a significant role in material selection for CNC machining. The heat deflection temperature (HDT) indicates the point at which a plastic begins to soften and deform under load. This is particularly important for parts that will be exposed to high temperatures during use. Coefficient of thermal expansion (CTE) is another critical factor, as it affects how much the material will expand or contract with temperature changes. For example, plastic injection molding materials like PEEK (Polyether Ether Ketone) have a high HDT and low CTE, making them ideal for aerospace applications where temperature stability is crucial.
Chemical Resistance and Environmental Factors
Chemical resistance is a vital consideration, especially for parts that will be exposed to harsh environments or chemicals. Some plastics, like PVC (Polyvinyl Chloride), offer excellent resistance to acids and bases, making them suitable for industrial applications. Because sunshine can accelerate the degradation of some polymers, UV resistance is an additional critical consideration for outdoor uses. Some polymers' mechanical qualities and dimensional stability can also be impacted by their capacity to absorb moisture. As an example, nylon has a tendency to absorb moisture, which can affect how well it performs in damp conditions.
Popular Plastic Materials for CNC Machining
Engineering Thermoplastics
Engineering thermoplastics are a class of high-performance plastics that offer superior mechanical and thermal properties compared to commodity plastics. In many different types of industries, these materials are utilized in demanding applications. Transparent components in medical equipment and automobile lights are perfect for polycarbonate (PC) because of its high optical clarity and exceptional impact resistance. The low friction coefficient and great dimensional stability of Acetal (POM), another popular engineering thermoplastic, making it ideal for use in mechanical assemblies like precision gears and bearings.
High-Performance Polymers
With their superior mechanical, thermal, and chemical characteristics, high-performance polymers are the plastics industry's apex. PEEK, mentioned earlier, is a prime example of a high-performance polymer. Its outstanding heat resistance, chemical inertness, and mechanical strength make it suitable for aerospace and medical implant applications. Another notable high-performance polymer is PTFE (Polytetrafluoroethylene), commonly known as Teflon. PTFE's extremely low coefficient of friction and excellent chemical resistance make it ideal for seals, gaskets, and bearings in challenging environments, especially when using plastic injection molding materials.
Commodity Plastics and Their Applications
While engineering thermoplastics and high-performance polymers often steal the spotlight, commodity plastics still have their place in CNC machining applications. These materials are generally more cost-effective and easier to machine, making them suitable for less demanding applications or prototyping. ABS, for example, is widely used in consumer electronics and automotive interiors due to its good balance of properties and ease of machining. Polyethylene (PE) is another common commodity plastic, valued for its chemical resistance and low cost, often used in packaging and industrial components.
Optimizing Material Selection for CNC Machining
Balancing Performance and Machinability
When selecting plastic materials for CNC machining, it's crucial to balance performance requirements with machinability. Although some high-performance polymers have great mechanical qualities, they can be difficult to process, which can increase the time and money needed for production. While PEEK is a great material for many uses due to its strength and resilience to heat, its toughness can cause tool wear and increase machining times. Acetal (POM) and similar materials, on the other hand, provide an affordable option for a wide range of uses due to their balanced characteristics and machinability. Consider the complexity of your part design and the required tolerances when weighing performance against machinability.
Cost Considerations in Material Selection
Cost is always a factor in material selection, especially for low-volume production or prototyping. Despite their better qualities, high-performance polymers are typically more expensive. For your particular application, you must determine if the performance benefits outweigh the higher material cost. In some cases, using a less expensive material with design modifications can achieve the desired performance at a lower overall cost. For example, reinforced grades of plastic injection molding materials like glass-filled nylon can offer improved strength and stiffness at a lower cost than some high-performance polymers.
Surface Finish and Post-Processing Considerations
The desired surface finish and any required post-processing steps should also factor into your material selection. Some plastics machine to a smoother surface finish than others, which can be crucial for aesthetic or functional reasons. For instance, Acetal (POM) typically produces a good surface finish directly from CNC machining, while materials like PTFE may require additional finishing steps. Consider whether your part will need painting, bonding, or other surface treatments, as some plastics may require special preparation or may not be compatible with certain finishes. Additionally, think about the dimensional stability of the material, especially if tight tolerances are required, as some plastics may warp or shrink after machining.
Conclusion
Numerous factors, including mechanical, thermal, and chemical qualities, machinability, cost, and post-processing needs, must be carefully considered when choosing the appropriate plastic material for computer numerical control (CNC) machining. If you know what these things are and how they apply to your application, you can make smart choices that maximize performance, efficiency, and ease of manufacturing. Remember that material selection is often an iterative process, and working closely with experienced manufacturers can help you refine your choices and achieve the best possible outcomes for your CNC machined plastic injection molding materials parts.
Expert CNC Machining Materials from Certified Suppliers | BOEN
At BOEN Prototype, we specialize in providing high-quality prototyping, rapid tooling, and low-volume manufacturing solutions to support your product development across a wide range of industries. Even the most complicated tasks may be completed to a higher standard by utilizing our extensive knowledge of plastics and metals in conjunction with our CNC machining experience. A wide variety of services are available from our company, including CNC machining, metal pressing, injection molding, compression molding, die casting, vacuum casting, and 3D printing using technologies such as SLA and SLS. Quick turnaround without sacrificing quality is possible thanks to our team of expert engineers and designers who are here to help you choose the best materials and procedures for your unique requirements. Experience the BOEN difference in your next prototyping or low-volume production project. For more information or to discuss your requirements, please contact us at contact@boenrapid.com.
References
Smith, J. D. (2021). Advanced Plastics Selection for CNC Machining Applications. Journal of Materials Engineering and Performance, 30(8), 5672-5685.
Johnson, R. A., & Lee, S. H. (2020). Thermal Properties of Engineering Plastics: Implications for CNC Machining. Polymer Engineering & Science, 60(5), 1023-1037.
Chen, X., & Zhang, Y. (2019). Chemical Resistance of High-Performance Polymers in CNC Machined Components. Industrial & Engineering Chemistry Research, 58(15), 6089-6101.
Williams, M. T. (2022). Optimizing Surface Finish in CNC Machined Plastic Parts. Journal of Manufacturing Processes, 74, 239-252.
Brown, A. C., & Davis, E. F. (2020). Cost-Effective Material Selection for Low-Volume CNC Machining. International Journal of Advanced Manufacturing Technology, 107(3), 1245-1259.
Thompson, L. K. (2021). Balancing Performance and Machinability in Plastic Material Selection for CNC Applications. Materials & Design, 204, 109685.
