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Common Plastics for CNC Machining
Plastic materials are of different types and offer versatile properties. As a result, it is advisable to use each of these materials based on their respective properties. This section discusses the top plastics perfect for custom plastic machining:
Acrylic
Acrylic or Poly Methyl Methacrylate is a famous resin with natural transparency, resistance to scratch, and lightweight properties, making it a commonly used material in different applications across industries. Furthermore, its cheapness, brilliant mechanical properties, toughness, impact, and weather resistance make it a perfect alternative to glass and polycarbonate. However, acrylic is vulnerable to aromatic/chlorinated organic substances. It has low resistance to heat and cracks under heavy loads.
ABS
Acrylonitrile Butadiene Styrene (ABS) is a versatile, lightweight plastic famous for its high machinability, impact resistance, and strength. Despite its excellent mechanical properties, ABS has low chemical stability, making it susceptible to alcohol, grease, and other chemical solvents. Additionally, pure ABS without additives exhibits low thermal stability. It is highly machinable and an affordable option suitable for rapid prototyping.
Nevertheless, ABS produces hot plastic fumes when heated. Hence, it would help to have proper ventilation to avoid gas buildup. Its low melting point causes defects from heat produced by a CNC machine.
PVC
PVC is a commonly used plastic polymer in CNC machining due to its high durability and versatility. Also, it is resistant to abrasion, chemicals, and moisture. Most product designers use PVC due to its ease of machining. You can easily cut, turn, mill, and drill this material to fabricate precise plastic parts. Furthermore, PVC is inexpensive, making it an affordable alternative in several applications. It is odorless, tasteless, and non-toxic. However, note that PVC has poor heating stability and releases toxic gas during machining.
Nylon
This plastic is a low-friction engineering plastic with excellent chemical, abrasion, and high-impact resistance properties. Likewise, it offers outstanding mechanical properties, including hardness (116R), strength (76mPa), and durability. These properties make nylon an ideal material for CNC machining, improving its use in the medical and automotive part manufacturing industries. Nylon is a low-cost material and exhibits excellent chemical and heat resistance. However, nylon absorbs moisture quickly and is vulnerable to strong mineral acids.
POM(Delrin)
Most manufacturers often use POM for CNC machining because it is highly machinable and offers high strength and resistance to wear/tear, heat, and chemicals. Due to their dimensional stability, the common POM grades are Delrin 150 and 570. It has a longer lifespan due to its durability and high tensile strength. Delrin is the most machinable plastic polymer of all. However, it would help to note that it exhibits poor acid resistance.
PEEK
PEEK offers unique mechanical properties such as high wear and tear and chemical and heat resistance to precisely 260ºC. Its recyclability, lightweight, and biocompatibility properties make PEEK a suitable replacement for some metals in part production. PEEK is highly recyclable and can withstand harsh environmental conditions.
Nevertheless, PEEK is costly and is not resistant to UV light. Likewise, it is not suitable for use in marine environments.
LDPE
LDPE is a tough, flexible plastic polymer with low temperature and excellent chemical resistance. It is an ideal material applicable for making orthotics and prosthetics in the medical industry. It is highly resistant to corrosion and compatible with heat techniques like welding. However, LDPE has low structural strength and is not ideal for making components with high-temperature requirements.
HDPE
High-density polyurethane plastic offers incredible resistance to corrosive chemicals and stress. This thermoplastic material exhibits excellent mechanical properties, including hardness (R65) and tensile strength (4000PSI). HDPE offers high durability and excellent mechanical properties. However, it exhibits poor UV resistance.
PTFE (Teflon)
This high-performance CNC machining plastic material offers chemical and mechanical properties, making it perfect for various commercial products. PTFE exhibits a low coefficient of friction and high chemical, fatigue, and UV resistance. This plastic polymer has anti-adhesive properties making it suitable for coating non-stick pans. Teflon has resistance to light and chemicals, and Its anti-adhesive properties make it suitable for coating.
However, PTFE is available in 2-inch thick plates and rods, restraining manufacturable parts’ thickness. Likewise, it has low mechanical properties than other plastic CNC machining materials.
Polyethylene
Polyethylene plastic polymer is popular for its strength, lightweight, stiffness, flexibility, and impact resistance properties. It exhibits impressive dielectric properties. Furthermore, polyurethane is available in different grades with varying applications- HDPE, LDPE, and UHMW PE. Polyethylene is lightweight and doesn’t compromise its mechanical strength. It is non-toxic, non-staining, and offers high tensile strength.
Polyethylene releases hot plastic fumes when heat-treated. Its low melting point leads to deformation due to the generated heat during machining.
Plastic CNC Machining Technologies
CNC plastic machining involves creating plastic parts with a computer-controlled machine. This CNC machine removes excess material from the plastic polymer, making consistent cuts till it produces the desired object/shape. This subtractive machining technology forms myriads of plastic parts with tighter tolerance, accuracy, and uniformity using these techniques:
CNC Milling
CNC plastic milling involves cutting material from a workpiece using a rotating milling cutter—the CNC milling cutter travel along multiple axes to create desired parts. The typical mills used for plastic CNC milling include flat, ball, and end mills.
CNC milling machines are of different kinds – 3-axis mills and multi-axis mills. 3-axis milling machines travel in three linear axes: up and down, left to right, and back and forth. Multi-axis CNC milling machines can travel more than three axes, making them perfect for machining plastic components with intricate geometries.
CNC Turning
CNC Turning involves rotating a workpiece held on a lathe against the spinning cutting tool, consistently removing material from the workpiece. Manufacturers use this subtractive manufacturing process to make cylindrical shapes in CNC-machined plastics. CNC lathes can add various features, such as grooves, holes, and threads, to plastic parts.
Common types of plastic CNC turning include:
- Taper CNC turning –perfect for making cone-like shaped parts
- Straight or cylindrical CNC turning – well-suited for making more significant cuts
CNC Drilling
CNC plastic drilling involves making a hole in a plastic workpiece with a drill mounted with a drill bit. The drill bit’s shape and size often decide the hole created in the plastic workpiece. More so, the hole’s size significantly influences chip evacuation. Radial, bench, and upright drill presses are the standard types available.
Alternatives to CNC Plastic Machining
This section discusses the various alternatives machining techniques to using CNC plastic part machining:
3D Printing
3-Dimensional printing is a widely used prototyping technology many small-scale businesses use in prototyping and low-volume production. This additive manufacturing technique enables rapid prototyping with its technologies.
3D printing technology involves developing 3D models and creating the desired components layer by layer. 3D printing prevents material waste and the need for tooling, making it an ideal process for producing parts with complex design requirements.
Injection Molding
Injection molding is a common mass-production process for machining plastic parts. It involves building a mold from steel or aluminum, depending on the desired longevity. You can use this process to form desired plastic parts with preferred shapes by injecting molten plastic into the mold cavity and cooling it after.
Plastic injection molding is a suitable method for prototyping and production of real parts. Additionally, it is a cost-effective alternative for machining plastic components with simple and complex designs. However, injection molded parts don’t always need additional processing or surface finishing.
Vacuum Casting
Vacuum or polyurethane casting is a machining technique that involves using silicon molds and plastic materials to create a copy of a model design. You can make various high-quality plastic components with a rapid prototyping process.
Applications of Plastic CNC Machining
Plastic CNC machining has many uses due to its benefits, including tight tolerance, precision, and accuracy. Below are typical industrial applications of plastic CNC machining:
Aerospace Parts
The aerospace industry requires high precision and tighter tolerances for machining processes. Hence, the use of plastic CNC machining in developing, testing, and creating various aerospace machined components. Plastic resins are applicable because of their suitability for their strength, complex shapes, lightweight, heat, and high chemical resistance. CNC machining plastic parts in this industry include brackets, ducting, and interior panels.
Medical Industry
CNC plastic machining is ideal for producing different medical tools and devices, including implants, diagnostic equipment, artificial hearts, and prosthetic limbs. This sector embraces the CNC machining method due to its high repeatability and accuracy, ensuring complex safety standards are met. More importantly, the process is compatible with several material options, allowing the creation of complex shapes.
Electronic Sector
The electronic industry greatly benefits from the high precision and durability of plastic CNC machining. Product designers in this industry use this process to create CNC-machined plastic electronic components such as LCD screens, wire enclosures, and device keypads.
Automotive Parts
The automotive industry utilizes plastic CNC machining to manufacture real-time prototypes and parts. Plastic machining is commonly used in this industry to create custom CNC parts like interior trims, dashboards, clips, and prototypes because of its lightweight properties, reducing fuel consumption. Also, plastic resins have excellent corrosion and wear resistance, making them suitable for most custom-machined automotive components.
When to Use Plastic for CNC Machining
Although many plastic materials exist, choosing between the plastic manufacturing techniques discussed earlier can be very difficult. Hence, here are some helpful tips to help you determine if plastic CNC machining is ideal for your products.
Quality Surface Finish
A conventional CNC machine offers CNC-machined plastic components a superior-quality finish. So, your products don’t necessarily need other surface finishing options.
Tight Tolerance
Plastic CNC machining is a versatile method that offers tight tolerances for complex design needs. A standard CNC milling machine provides a tight tolerance of precisely 4µm.
Special Materials
You can make several plastic components with the plastic CNC machining method. This process is compatible with different plastics, such as those with unique properties such as high chemical resistance, high-temperature resistance, and high strength. Hence, it is an ideal process that matches the specialized requirements of some prototypes.
Testing Stage
CNC machining depends on 3D models because they are easy to modify. As such, CNC machining helps product designers and engineers to develop functional plastic prototypes. It helps to test, detect and rectify design flaws since the testing stage supports consistent design modifications.
Economical Option
Plastic CNC machining provides a cost-effective process of making plastic parts. Plastics are not as expensive as metal and other materials like composites. More importantly, CNC machines are highly accurate and can handle complicated geometries.
Conclusion
This article has given a detailed overview of various Plastic CNC machining, discussing the multiple plastics for CNC machining and other vital aspects—manufacturers across industries due to its vast benefits, including tight tolerance, accuracy, and speed. Although plastic CNC machining can pose certain challenges, AT-Machining is the most reliable CNC machining service provider to consult.
Our engineering team possesses in-depth knowledge of thermoplastic and thermoset materials and machining capabilities, including 3-, 4-, and 5-axis machining, milling, turning, and drilling with precision tolerances of .0001″. We handle all custom CNC plastic machining, no matter the design complexity. Contact us today for complete solutions to your plastic CNC machining needs.
