CNC Machining: Plastic parts
Plastic is a versatile engineering material that contributes to the manufacturing industry with various unique properties. Plastic is used in CNC manufacturing for prototyping design, customized parts, and large-scale production of different products.
CNC machining of plastic is a subtractive manufacturing method in which the creation of parts involves removing material from the workpiece. The tool setup follows the digital instruction provided to the CNC machine and informs of G-code. The process is fully automated. Numerous types of parts are creatable with high accuracy and precise tolerances using plastic CNC machining.
CNC machining of plastic plays a significant role in the medical, semiconductor, aerospace, beverage, food, and automotive industries. This article will overview common CNC machining plastics, their advantages and disadvantages, applications, and surface finishing options for CNC machined plastic parts.
Common Plastics for CNC Machining
CNC machining is compatible with a wide range of plastics. However, some specific plastics are widely used due to their excellent physical, mechanical, and chemical properties Let’s overview some of the popular plastics in detail.
ABS
ABS is a hard and rigid plastic that offers excellent impact resistance. CNC machining of ABS leaves a smooth surface. However, if needed, different surface finishing, like surface metallization, electroplating, and painting, can be applied in post-processing. With CNC machining of ABS, various durable parts can be created for the aerospace, automotive, electronics, and home appliances industries.
Delrin
Delrin is a popular engineering thermoplastic, which is also known as polyacetal, or acetal. It offers low-moisture sensitivity, chemical inertness, electric & thermal insulation, and excellent mechanical strength. It is applicable in automotive to make seat belts, locks, clips, and various parts for pumps and fittings.
Nylon
Nylon is known for its elasticity and applies to various general applications such as toys, ropes, tents, cookware, and automotive parts. It has exceptional tensile strength, chemical inertness, abrasion resistance, and strength-to-weight ratio.
Polycarbonate (PC)
Polycarbonate (PC) is a tough plastic, which offers excellent Stiffness, creep resistance, impact resistance, and thermal stability. It is also transparent in nature. CNC machining of PC is used for bottles, discs, pumps, valves, and various automotive and aerospace applications.
PEEK
PEEK is a high-strength semi-crystalline thermoplastic that offers excellent electrical insulation, strength-to-weight ratio, thermal & chemical stability, and resistance to combustion. It is used in the automotive, aerospace, medical, and electronic industries to make various parts. Besides these, other various plastics are used in CNC machinings, such as Acrylic, Garolite G-10, FR4, Polyethylene (PE), Polypropylene (PP), PPSU, PPS, Polyetherimide, and PVC.
Advantages
Using plastics for CNC machining projects has various advantages. It provides a low-cost replacement for metals and alloys in different applications. Following are the key advantages offered by the CNC machining of plastics.
1 Corrosion-resistive part
Plastic does not rust over time, even in areas with high moisture levels, whereas metal and alloys are known to have a high risk of corrosion. Therefore, plastic products produced through CNC machining are the trustworthy choices for applications where corrosion resistance quality is crucial.
Plastic does not rust over time, even in areas with high moisture levels, whereas metal and alloys are known to have a high risk of corrosion. Therefore, plastic products produced through CNC machining are the trustworthy choices for applications where corrosion resistance quality is crucial.
2 Cost-effectiveness
Plastic is cost-effective material. Most plastics are cheaper than metal and alloys and provide unique physical and mechanical properties. Even while CNC plastic machining is more expensive than injection molding, it is still less costly than CNC metal and alloy machining.
You won’t notice a cost difference if you produce a small number of parts, but creating several parts at once results in significant financial savings.
Plastic is cost-effective material. Most plastics are cheaper than metal and alloys and provide unique physical and mechanical properties. Even while CNC plastic machining is more expensive than injection molding, it is still less costly than CNC metal and alloy machining.
You won’t notice a cost difference if you produce a small number of parts, but creating several parts at once results in significant financial savings.
3 Quick production
Plastics are incredibly compatible with CNC machines and require less time for machining. Prototypes for any applications can be prepared within a few hours. It allows manufacturers to test the prototypes quickly and decrease the time for prototyping. If you need customized parts, that also takes less time than injection molding and other manufacturing approaches.
Plastics are incredibly compatible with CNC machines and require less time for machining. Prototypes for any applications can be prepared within a few hours. It allows manufacturers to test the prototypes quickly and decrease the time for prototyping. If you need customized parts, that also takes less time than injection molding and other manufacturing approaches.
4 Chemical inertness
Unlike metals and alloys, Plastics do not react with chemicals, which makes them ideal for various applications such as food processing and oil & gas.
Unlike metals and alloys, Plastics do not react with chemicals, which makes them ideal for various applications such as food processing and oil & gas.
5 Electrical insulation
Various parts for electronics and electrical applications need electrical insulation properties; those parts are easily creatable with CNC plastic machining. Therefore, it makes excellent choices for housing electrical devices, semiconductor handling devices, and parts for various circuit boards.
Various parts for electronics and electrical applications need electrical insulation properties; those parts are easily creatable with CNC plastic machining. Therefore, it makes excellent choices for housing electrical devices, semiconductor handling devices, and parts for various circuit boards.
6 Excellent As-machined surface finish
CNC machining of plastics leaves a smooth surface without any rough edges. In most cases, machining marks are invisible and provide a low level of roughness to the surface. In addition, other finishing can be applied, such as painting, metallization, and bead blasting.
CNC machining of plastics leaves a smooth surface without any rough edges. In most cases, machining marks are invisible and provide a low level of roughness to the surface. In addition, other finishing can be applied, such as painting, metallization, and bead blasting.
7 Accuracy
Plastics can be machined with a high degree of accuracy Using CNC technology. It allows the creation of plastic parts with maintaining tight tolerances. Even complex shapes are easily achievable by using different CNC machining processes.
Plastics can be machined with a high degree of accuracy Using CNC technology. It allows the creation of plastic parts with maintaining tight tolerances. Even complex shapes are easily achievable by using different CNC machining processes.
Disadvantages
Although CNC machining of plastics has several advantages, there are some drawbacks to the process too. Having an idea about limitations and disadvantages helps to minimize the possible error. So, let’s discuss some disadvantages.
1 Deformation of the workpiece
Plastic sheets or rods used as raw materials for CNC machining may not always be precisely flat or straight. This could distort the workpiece and cause problems with uniform feeding. Therefore, verifying the workpiece’s flatness and roundness is crucial before machining.
2 Cracks
The brittleness nature of plastic sometimes causes the workpiece to crack while machining. If the design has a thin surface and sharp edges, it increases the chance of having cracks. So, it is best to avoid sharp corners while designing plastic parts for CNC machining. In addition, the optimum tool path should be finalized before the process.
3 Wrap and distortion of the workpiece
Since plastics are brittle, it might be challenging to hold the workpiece for machining in some cases. Excessive stress during hold can be damaged or warp the workpiece. Also, plastics cause the cutters to wear more quickly. So, careful monitoring is required during the hold and selection of cutters. It is vital to select the coated tools.
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