CNC Machining of Polycarbonate (PC)

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Science and technology are developing continuously. Polycarbonate (PC) is used more and more in machinery manufacturing. Polycarbonate is a high-performance plastic. It is used widely in construction, electronics, cars, medicine, and daily items. It has excellent mechanical, optical, and processing properties. These make it important in the demanding fields of aerospace, electronics, and safety gear. Next, it will discuss why we use CNC to machine polycarbonate. Then, it will discuss the properties of polycarbonate. Also, we will share tips on CNC machining of polycarbonate. This is for your understanding. Let’s get started!

What Is Polycarbonate?

Polycarbonate (PC) is a flexible thermoplastic. It has no fixed melting point and becomes soft before melting. Polycarbonate is usually sold in transparent and black strips and sheets. In addition, polycarbonate is a stronger and more flexible alternative to normal glass when you need parts with high-light transmission. It is lightweight and has low crystallinity because it consists of amorphous molecules. Polycarbonate is more heat-resistant and impact-resistant than other plastics such as plexiglass.

PC is a flexible engineering plastic with many excellent properties. Polycarbonate is available in different grades, but generally has the following mechanical properties:

High Resistance to Breakage and Impact. Polycarbonate is renowned for being very hard and not easily damaged by impact. It is therefore often used in high-performance environments.
Resistant to UV Radiation. Some types of polycarbonate are extremely resistant to UV radiation. They do not decompose in direct sunlight.
Heat and Fire Resistant. Polycarbonate can withstand temperatures of up to 140°C. It is therefore ideal for medical applications that require repeated sterilization.
Chemically Resistant. When it comes to chemicals, polycarbonate is highly resistant to alcohols, greases, inorganic acids, and aliphatic hydrocarbons.
Excellent Dimensional Stability. This thermoplastic does not shrink significantly, between 0.6% and 0.9%. It therefore retains its shape in most cases.
Transparency and Clarity. The amorphous structure of polycarbonate plastic gives it a high degree of transparency and clarity. It also lets 90% of light through and has a refractive index of 1.548. It is therefore a popular alternative to glass.

Common Types of Polycarbonate

There are different grades of polycarbonate, each with its own mechanical properties. Different grades are suitable for different tasks in different areas. The following types of polycarbonate are commonly used for CNC machining:

General-purpose Polycarbonate

This polycarbonate is extremely tough and has excellent transparency. General-purpose polycarbonate has a smooth surface and a beautiful appearance. It is also highly UV-resistant and is therefore ideal for outdoor use.

Glass-filled Polycarbonate

This polycarbonate is very strong, with high impact strength and toughness. It is an ideal substitute for metal and engineering plastics. It is made stronger by the addition of 10–40% glass fibers. As a result, it can be used to replace metal in the manufacture of industrial-grade parts.

Mechanical-grade Polycarbonate

This polycarbonate is very dimensionally stable. It has excellent electrical properties, a high modulus of elasticity, and impact resistance. Parts made from mechanical-grade polycarbonate are often used in situations where a lot of work needs to be done.

AMGARDTM Polycarbonate

AMGARDTM polycarbonate is a unique industrial plastic. It contains silver ions in the material, which prevent the growth of microorganisms on its surface. This polycarbonate is ideal for manufacturing medical equipment and instruments, protective shields, and other items that require a bacteria- and mold-free surface.

TUFFAK polycarbonate

TUFFAK is a flexible polycarbonate plastic that is twice as strong as glass. It can be produced in a variety of ways, including CNC machining and thermoforming. TUFFAK polycarbonate has very good dimensional stability and is compatible with glues, paints, and solvents.

Why use polycarbonate for CNC machining?

Good Mechanical Properties

Polycarbonate is strong and rigid. It can withstand the cutting force and pressure in machining. This keeps the machined parts accurate in size and shape.

Excellent Toughness

Polycarbonate is tough. It’s hard to make it crack or fracture. This toughness keeps the processing stable and safe. This is especially so when working with complex shapes.

Good Dimensional Stability

Polycarbonate keeps its shape well under varying temperatures and humidity. This stability ensures that the processed parts stay the right size and shape. When the temperature and humidity change, the size changes are small. This helps to keep the machining accurate.

Good Transparency

Polycarbonate is see-through. It can be made into see-through or semi-see-through parts. Smooth and pretty parts are made from see-through materials. So, they are widely used in parts and optical components that need visual inspection. They are the ideal material for making see-through or optical parts.

Excellent Temperature Adaptability

Polycarbonate can keep its shape and work at high temperatures. Its continuous use temperature range is typically between -40°C and 120°C, and it can even withstand temperatures up to 140°C for short periods. This heat resistance makes polycarbonate suitable for use in high-temperature environments. For example, in automotive lampshades, electronic equipment housings, and lighting fixtures.

On the other hand, polycarbonate maintains good toughness and impact resistance at low temperatures. It stays strong even at temperatures as low as -40°C. This makes it good for use in cold weather. For example, in outdoor equipment and aerospace parts.

Good Machinability

Polycarbonate is easy to machine. It allows simple cutting, drilling, and milling with standard CNC equipment. It also allows CNC machining to make many complex shapes and structures. This facilitates CNC machining and ensures the quality of the final product under a wide range of process parameters. Also, polycarbonate does not cause excessive heat and wear during machining. This extends tool life.

Superior machinability of polycarbonate

In CNC machining, polycarbonate exhibits several excellent machining properties:

Low Cutting Force Requirements: Polycarbonate is relatively soft, so less cutting force is required during the cutting process. This helps to reduce the load on the machine tool, extend tool life, and reduce energy consumption.
High-precision Molding: It can achieve high-precision machining and has better dimensional stability. In addition, the machined parts have smaller dimensional deviations and can meet the needs of applications with higher accuracy requirements.
Good Surface Finish: The surface after processing is smooth and flat, with a low roughness value. It also achieves a good appearance without much need for subsequent processing.
Low Tool Wear: Low wear on the tool, reduces the frequency and cost of tool replacement.
Better Thermal Stability: The heat generated during the machining process has a relatively small impact on its performance, helping to maintain machining accuracy and surface quality.

Excellent Mechanical and Optical Properties

Now, CNC machines like to use polycarbonate. This is mainly because it has great mechanical and optical properties.

Mechanical Properties

Impact Resistance: Polycarbonate (PC) is a tough material with excellent impact resistance. This means that PC materials maintain their integrity and structural stability even in high-stress or impact environments. This property allows CNC-machined PC parts to be highly durable and resistant to damage.
Thermal Stability: PC materials are thermally stable and maintain their mechanical properties at elevated temperatures. The heat distortion temperature is usually 110-150°C. This means that when CNC machining, the heat won’t deform or damage the PC material.
Electrical Insulation: PC materials have good electrical insulation properties, making them ideal for use in electronic and electrical applications. In CNC machining, this property lets PC components isolate current and voltage. It keeps the equipment safe and stable.

Optical Properties

High Transparency: PC materials have high light transmission, with a light transmission rate of over 90%. This gives PC parts a clear advantage in application scenarios such as manufacturing optical components or transparent housings. This transparency can be retained during CNC machining, resulting in a final product with excellent optics.
High Refractive Index: With a refractive index of approximately 1.585-1.586, PC materials are high refractive index materials. This high refractive index makes PC transparent. It can replace glass and other costly materials to cut costs.
Light Resistance: PC materials have excellent light resistance properties and can maintain their transparency under long-term UV exposure and effectively resist aging. This gives PC parts high durability in outdoor environments or in applications that require long-term exposure to light.

Advantages of Using CNC to Process Polycarbonate

Versatility of Processing Options: Polycarbonate can be machined using a variety of CNC machining processes, including milling, turning, drilling, and cutting. This allows it to excel in a variety of manufacturing applications, from simple flatbed machining to complex 3D structure fabrication.
High Machining Efficiency: The high degree of automation and the ability to perform machining quickly and continuously greatly increases productivity. This is very favorable for mass production and rapid prototyping.
Low Generation of Internal Stress: During CNC machining, polycarbonate is less likely to have internal stress. This lowers the chance of parts deforming after machining. This is critical for applications requiring high dimensional stability.
High Accuracy and Consistency: The ability to achieve very high dimensional and shape accuracy ensures that each machined polycarbonate part has a high degree of consistency and meets strict industry standards and design requirements.
Complex Shape Processing Capability: We can easily make polycarbonate parts with complex shapes. These shapes include internal structures and outer contours. They will accurately match the design.
Good Surface Quality: The surface of parts machined with CNC is smooth and flat, reducing the need for subsequent surface treatment processes and saving time and costs.
High Material Utilization: Accurate programming and machining path planning can minimize material waste. This cuts production costs.
Repeatability: With CNC machining, as long as the programming and settings are the same, the same parts can be produced over and over again, which ensures the stability of product quality and greatly improves production efficiency.

CNC Machining Polycarbonate Parts Applications

Electronic and Electrical Appliances Field: Polycarbonate is strong and insulating. It is good for making electrical connectors, terminals, and other insulating parts. These parts ensure the safety and reliability of electrical systems.
Automotive Field: Polycarbonate is strong and heat resistant. It is good for making car headlight covers, tail light covers, and instrument panels. These parts need to be durable and give good optical performance.
Construction: Polycarbonate is clear and can resist weather. These properties make it good for transparent roofs, light covers, and windows in construction. They provide natural light and save energy.
Medical Devices: Polycarbonate is biocompatible and sterilizable. This makes it suitable for making surgical instruments, syringes, and diagnostic equipment. It ensures safe use in medical settings.
Aerospace: In aerospace, polycarbonate makes aircraft windows and hatches. It keeps flights safe and efficient because it is light and resists impacts well.
Optical field: Polycarbonate has great optical properties. It is used to make many types of lenses, like camera lenses.

CNC Machining Finishing Options for Polycarbonate Parts

Polycarbonate is prone to scratching, so there are a number of surface treatments that can be used. These surface treatments help to improve the physical properties of the PC parts after machining. This makes them better suited for use in practical applications. The following are some of the surface treatments for polycarbonate:

Machining

Machining is a common and inexpensive method of processing. It is suitable for machined parts that do not require any further processing. Machined parts may have fine tool marks or scratches on the surface. However, it is a cheaper and faster way of production.

It should be noted that machining cannot provide an optically clear surface for polycarbonate parts. This can be achieved by machining polycarbonate parts using diamond tools. Therefore, customers must request this surface treatment directly during the quotation process. This may increase the processing cost.

Steam polishing

Parts machined on a CNC machine often have visible tool marks, which can change the appearance of the product. Steam polishing is often used to remove scratches and tool marks from machined polycarbonate parts. This is done by placing the part in a solution that reacts with and melts the surface of the part. It then causes the material to flow and mask the tool marks.

The surface of a CNC-machined polycarbonate part is usually transparent. However, if it is melted during the machining process, it may become almost opaque. After the part has been machined, steam polishing is an excellent way to smooth the surface and give it a uniformly high gloss or a perfectly clear appearance. However, this surface treatment is not suitable for components that need to be optically transparent.

Polishing

This process improves the appearance of tool marks on the surface of machined polycarbonate parts. A rapidly rotating cotton polishing wheel is used to smooth the surface of the part. This method is ideal for machining large parts with smooth outer surfaces. On the other hand, polishing does not have the same polishing effect as steam polishing on machined polycarbonate.

Scratch-resistant Coating

One of the disadvantages of polycarbonate is that it is prone to scratching. We can coat CNC-machined polycarbonate parts. This helps to reduce scratching and improves their optical clarity.

Expert Tips For CNC Machining Polycarbonate

At present, the application fields of polycarbonate are getting wider and wider. Yonglihao Machinery has been a CNC machining and manufacturing enterprise for many years. They have much experience and skill in CNC machining polycarbonate. Here are some tips for machining polycarbonate:

Tool Selection

When machining, use sharp tools. They ensure smooth cuts and reduce delamination and burrs. You should pick a tool material that works for machining polycarbonate. For example, tungsten steel or high-speed steel are good choices.

Select the Appropriate Cutting Parameters

Cutting parameters are important factors affecting processing efficiency and product quality. For polycarbonate, the right cutting parameters can ensure fast processing. They also ensure good product quality. Generally speaking, the cutting speed of polycarbonate should be moderate, usually 2500 to 3000 RPM. too high a speed will lead to material overheating and melting, too low a speed will lead to cutting not being smooth.

In addition, a proper feed rate will minimize vibration and scraping of the material. The recommended feed rate is 800 to 1200 mm/min. But, adjust the parameters to fit the machining requirements and tool choice. There is also the depth of each cut should be smaller to avoid material cracking or tool overheating. A depth of cut of between 0.5 and 2 mm is usually recommended. However, it should be noted that the optimal cutting parameters are not fixed, and need to be selected according to the wear of the tool, the specific composition and properties of the PC material, and the processing requirements.

Use of Coolant

We use coolant to cool the tool. It also cuts wear and betters surface quality. The coolant choice should be based on the plastic’s traits. It should also match the machining needs.

Tool Path Planning

Plan the tool path to cut force and avoid stress. Minimize force concentration. The use of gradual deepening of the cutting method can improve the quality of machining.

Clamping and Fixing

To keep the polycarbonate in place during machining, use vacuum suction cups, clamps, or double-sided tape. They prevent the material from moving. On the other hand, reduce material vibration by adding more clamping points. You can also use vibration-damping shims. These steps ensure smooth cutting and surface quality.

Post-treatment

We do post-treatment as needed. It includes polishing and sanding. These steps improve the finish and quality of the machined surface. Fine sandpaper or polishing paste can be used to polish the surface to enhance the surface finish.

Conclusion

CNC machining of polycarbonate is an important tool in modern manufacturing. This is due to its great strength and processing flexibility. It can make good parts. In addition, It can also improve products. It does this through better machining and post-treatment. Science and technology are progressing. Processing tech is maturing. CNC machining polycarbonate will soon show its unique advantages and wide uses. It will offer better and faster solutions for many industries. If you need parts made from polycarbonate, please contact us at Yonglihao Machinery. We will be happy to serve you and provide expert machining solutions and products.

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