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CNC Machining: Plastic parts

Author: Yaozu Deng
Published on: 2022-10-18

CNC machining of thermoplastic

Plastic CNC machining process

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, and food& automotive industry. This article will overview common CNC machining plastics, advantages, disadvantages, applications, and surface finishing options for CNC machined plastic parts.

 

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Common Plastics for CNC Machining

Common types of plastics

Common types of plastics

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.

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.

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.

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.

5 Electrical insulation

Various parts for electronics and electrical applications need electrical insulation properties; those parts are easily creatable with plastic CNC 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.

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.

 

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.

Related:

What are the most common cnc machining defects?

 

Surface Finishing options

Parts with as-machined surface finish

There are many options for surface finishing of CNC machined plastic parts. As-machine surface finishing could be sufficient in some applications. However, it is frequently necessary to preserve functionality and aesthetic appeal.

1 Bead Blasting

In bead blasting, a jet of compressed air mixed with abrasive materials such as sand, silicon carbide, and glass pieces is targeted toward the surface of plastic parts. It can maintain the roughness (Ra) lower than 32 µin.

2 Painting

The best way to make plastic items aesthetically pleasing is to paint them. It entails applying paint in the desired colors by spraying it onto the surface of plastic parts. The parts are also protected from wear and tear by painting.

3 Brushing

Brushing serves various purposes for plastic parts, such as cleaning, edge blending, and deburring. It is the best way to protect the surface from damage and scratches. You can use different types of brushes to create smooth and shiny finishes.

 

Applications

There are numerous applications of plastic CNC machining. CNC-machined plastic parts are used in simple household appliances to complex aerospace components. Let’s discuss various applications in detail;

1 Electronics

Parts for electronic application

Parts for electronic application

CNC-machined plastic parts have a significant role in the electronics and electrical industry. It is used in the Rapid prototyping of different electronic products, including phone housing, circuit boards, switches, and other items.

2 Medical

The chemical inertness and lightweight property of plastics make them suitable for various medical equipment. Parts from plastic CNC machining allow for extreme levels of sterilization regularly. Plastic is used to make sterilization trays, surgical equipment, insulin pens, catheters, endoscopic probes, and many more.

3 Aerospace

Aircraft parts made from plastic

Aircraft parts need to be light in weight and high strength; plastics fulfill those requirements very effectively. CNC machining of plastic is an ideal option for making prototypes of various parts and testing them before production. Plastics make fuselages, ventilation ducts, tank covers, rudders, radomes, and many more.

4 Automotive

Various high-performance plastics, such as PEEK and PPS, and others, can withstand extreme environments and high-stress levels, making them suitable for different automotive parts. Various parts can be created from plastic CNC machining, including housing, chassis, vents, AC components, exterior, and many more.

In addition, plastic is used for prototyping various types of Vehicles. Corrosion restiveness and the light weight of plastics also help to enhance the performance of the automobile.

5 Defense

Plastic CNC machining offers a wide range of parts for defense equipment. Plastic parts are suitable options for communication devices, tanks, and precise weapons.

6 General applications

Plastic CNC machining has various general applications, such as toys, ropes, cables, kitchenware, and many more.

Conclusion

Plastic CNC machining is a versatile and popular approach to manufacturing, applicable to a wide range of applications. It offers precision, reliability, cost-effectiveness, and tight tolerances. It fulfills the various requirements for automotive, aerospace, defense, medical, electronics, and other industries.

At Prolean, we have experienced production specialists and skillful operators to deliver accurate plastic parts for your project with CNC machining. We will make your design a reality, regardless of where you are or the type of project you are working on.

 

FAQ’s

What are the common plastics used in CNC machining projects?

Numerous types of plastics are compatible with CNC machining. However, ABS, Delrin, Nylon, Polycarbonate, and PEEK are used in most cases.

Related resources:

Common Materials for CNC Machining

What are the advantages of plastic CNC machining?

CNC- machined plastic parts offer accuracy, chemical inertness, electrical insulation, quick turnaround, and tight tolerances in different applications.

What are the surface finishing options for CNC-machined plastic parts?

As-machined surface finishing might be sufficient in some cases. However, there are different surface finishing options, including bead blasting, brushing, painting, metallization, and many more.

What are the applications of plastic CNC machining?

Plastic CNC machining applies to electrical, electronics, medical, aerospace, automotive, defense, cookware, and other industries.

1 Comment

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