The Complete Guide to Acrylic CNC Machining

Acrylic, also known as PMMA or Plexiglas, is an important malleable polymer material. It has high light transmission and stiffness, making it an ideal alternative to glass.

With the increasingly wide application of acrylic materials in various industries, the demand for acrylic machining parts is also growing day by day. We can process acrylic through a variety of processes, the most common of which is CNC machining acrylic, as it can produce parts with high precision dimensions and shapes.

In this article, we will discuss with you in depth about acrylic CNC machining, so that you can have a more comprehensive understanding of acrylic machining, including how to process acrylic, its properties, advantages and applications.

What is Acrylic?

Acrylic, also known as polymethylmethacrylate (PMMA), is a transparent thermoplastic that is often used as a lightweight and shatter-resistant alternative to glass. It offers excellent optical clarity and versatility, including chemical stability, weather resistance, good hardness, high printability adhesion, attractive appearance and recyclability.

In the continuous development of the machinery manufacturing industry today, acrylic sheets, with their high hardness, good luster, environmental protection, transparent acrylic sheet by virtue of its own excellent characteristics, in the processing and thus improve the texture and aesthetics of the product acrylic precision parts also has a wider range of market applications, including aerospace, automotive, medical, electronics, pharmaceutical industry, petrochemical and other various fields.

After these introductions, you must also want to know more about acrylic machining knowledge. Below, let's take a look at what characteristics acrylic has.

A Basic History of Acrylic

Acrylic, which was discovered in 1872, has been around for more than a hundred years. In 1927 the world's first complete piece of acrylic was manufactured, followed soon after acrylic began to gradually realize large-scale production. At first acrylic was mainly used in aircraft, until the end of the last century, with the further development of science and technology, production processes, acrylic gradually applied to automotive, lighting, consumer electronics and other fields.

Properties Of Acrylic

There are many properties of acrylic, below we mainly talk about its 8 properties：

Optical Clarity: High light transmittance, pure acrylic transparent plate light transmittance is above 90%, usually 92%. Taking 6mm as a reference, the light transmittance of ordinary glass is usually 82-83%, and the light transmittance of 6mm super white glass is 90%-92%.

Lightweight: With a density of only 1.17 to 1.20 g/cm³, acrylic is a lightweight material, approximately half the weight of ordinary glass and 43% that of aluminum.

Strength and Durability: Acrylic has strong impact resistance, being sixteen times that of ordinary glass, with minimal risk of breakage.

Weather/UV Resistance: It exhibits excellent resistance to ultraviolet rays and temperature changes, remaining resistant to yellowing, becoming brittle, or wearing out, thus ensuring a long service life.

Chemical Stability: Acrylic demonstrates good resistance to most acids, alkalis, and other chemicals.

Easy to Process: Acrylic is highly moldable, easily processed into various shapes through cutting, engraving, and thermal bending, with minimal risk of cracking during fabrication.

Low Moisture Absorption: Acrylic sheets have low moisture absorption, making them resistant to moisture and mold, suitable for humid environments.

Environmental Friendliness: 100% recyclable, acrylic is durable and long-lasting. Waste acrylic can be recycled by removing impurities and reintegrating it into raw materials to produce new acrylic sheets.

Types of Acrylic

Clear Acrylic: The most common type of acrylic, available in a wide range of thicknesses. Clear acrylic resembles glass in appearance and even surpasses ordinary glass in light transmission. It can undergo various secondary processing, making it the most widely used type.

Colored Transparent Acrylic: Also known as color sheet, it has a softer light transmission compared to clear acrylic, offering rich color options, making it ideal for decorative purposes. It can be classified into two categories: transparent colored and semi-transparent colored.

Pearlescent Acrylic: This type is made by mixing pearlescent powder or fluorescent powder into ordinary acrylic. It exhibits vibrant colors and a high surface gloss, often used for creating unique shapes, food packaging.

Embossed Acrylic: Available in four types: transparent, semi-transparent, colored, and uncolored. It can produce the same texture effect as embossed glass. It is often used for decoration, doors and windows, and can present a light-transmitting but not transparent effect.

How To CNC Machine Acrylic?

There are many different machining processes for machining acrylic, including 3D printing, injection molding, thermoforming, and bonding processes.

One of the fundamental principles of machining acrylic is to remove the heat via chips as quickly as possible. Acrylic has a low melting point of 320 F, that’s why high temperature will affect its cutting performance and surface quality. To reduce the frictional effect, the material is machined at a higher feed rate.

The following is an overview of the most common CNC machining methods for acrylic:

CNC Milling Acrylic

CNC milling is the most popular machining method for machining acrylic, where a rotating tool is used to remove material from a stationary acrylic sheet or workpiece, allowing for the machining of parts with high precision and complex geometries.

Acrylic CNC milling has a variety of operating functions, such as deep cutting, shallow cutting and peripheral milling.

CNC Turning Acrylic

CNC turning is a process that uses a single-point fixed cutting tool to remove excess material from a rotating acrylic workpiece. End machining, thread cutting, slotting and boring are often used, and the parts produced are generally cylindrical.

CNC Engraving Acrylic

CNC engraving acrylic is an efficient and high-precision process. Through this process, you can achieve a variety of shapes and patterns on acrylic workpieces, including adding design text, symbols or marks to add aesthetic or functional characteristics to the parts.

CNC Drilling Acrylic

CNC drilling of acrylic refers to the processing method where a computer-controlled system precisely drills holes in acrylic sheets. Whether it's a simple through hole or a complex angled hole, you can create clean, burr-free holes without causing damage.

CNC Cutting Acrylic

CNC cutting is a precise and efficient method for cutting acrylic sheets into desired sizes and shapes. It boasts fast cutting speeds, enhancing production efficiency, making it suitable for mass production. Each cut maintains consistent accuracy and quality.

Advantages Of CNC Machining Acrylic

Easy to Process

Acrylic is a thermoplastic material that becomes highly moldable when heated, making it easy to process into various shapes and sizes. Due to its high consistency and absence of particles in PMMA material, CNC machining can achieve ultra-high precision and intricate detail processing without easily breaking.

Precision and Accuracy

CNC machining of acrylic achieves higher accuracy, producing high-precision acrylic components with tight tolerances of +/- 0.01mm, thereby facilitating the machining of complex parts and shortening the production cycle.

Consistent Quality

CNC machining of acrylic utilizes computer control to process the material, minimizing human errors and producing consistent high-quality products, saving time and effort.

Versatility in Techniques

CNC machining enables various processing methods including milling, turning, cutting, engraving, drilling, etc., meeting diverse project requirements and enabling the production of acrylic products in various shapes and patterns.

Surface Finishes For CNC Machined Acrylic

Here are some of the common finishes for acrylic:

Polishing: Using sandpaper of different grit sizes to polish the surface of acrylic, removing machining marks to enhance surface smoothness and light transmittance.

Bead Blasting: Using compressed air to spray fine sand or abrasives onto the surface of acrylic, giving it a frosted appearance to improve slip resistance and scratch resistance.

Silk Screening: Applying silk screening on the surface of acrylic to print various patterns, text, logos, etc., enhancing decorative effects and product recognition.

UV Coating: Applying UV-cured paint onto the surface of acrylic parts, enhancing their glossiness, hardness, and weather resistance.

Difficulties you may face during Acrylic machining

These are some of the difficulties that you may face during acrylic machining.

Cloudy Appearance: Before using coolant or any solvent for cleaning purposes, make sure that they will not react with the acrylic material. Some solvents or oil-based coolants may react with the part or make it turn cloudy.

Stringy Chips: The continuous operation will develop some stringy chips. This is a serious safety concern for both operator and the equipment. Try anything you can to avoid these chips.

Overheating: While machining acrylic parts you strictly need to follow the temperature requirements. Cutting at high speed with a lower feed rate will generate heat which will lead to melting the workpiece. To avoid overheating, try to machine at a slow speed with a higher feed rate.

Poor Surface Quality: You may encounter a problem of poor surface quality. To avoid this issue, try to use a sharp edges cutting tool with coolant. It reduces the frictional effect and leads towards excellent surface quality.

Clingy Chips: Some chips cling around the machine tool or at the place of machining. It results in increasing the temperature of the workplace. To avoid chips clinging, use polished cutting tools at low speed and a higher feed rate.

Machine Malfunction: It is necessary to carry out preventive maintenance of the CNC acrylic machines to avoid any trouble or malfunction. Machining under unfavorable environmental and operating conditions will also cause machine malfunction.

4 Tips for Getting Quality CNC Acrylic Parts

Material Selection and Inspection: Make sure to use high-quality, high-purity acrylic materials to avoid melting or cracking due to material problems during processing. Check the material for scratches, impurities or bubbles, which may affect the appearance and strength of the final product.

Choose the Right Drill Bit: Carbide is an efficient material for drilling holes in acrylic materials, and O-slot end mills are more commonly used. Before machining, make sure the drill bit is sharp, otherwise it may cause stress cracking.

Set the Right Parameters: According to the needs of the project, choose the appropriate acrylic material type and thickness, and then set the correct feed rate, depth to ensure the processing accuracy and surface quality of the part.

Check the Revolutions Per Minute (RPM): Feed rate and RPM complement each other. Setting a high feed rate helps cut the material faster, while keeping the RPM relatively consistent to prevent the material from melting.

Applications Of CNC Acrylic Parts

Rapid Prototyping: Due to its affordability and sustainability, acrylic material is also widely used to develop prototypes. Various manufacturing industries are using acrylic for rapid prototyping via the subtractive machining method.

Glass Alternatives: Due to its superior transparency and impact resistance, acrylic is an ideal substitute for glass in multiple industries such as optics, automotive and aerospace.

Medical: Acrylic is non-toxic, easy to clean and has good biocompatibility, making it ideal for medical applications and an ideal choice for laboratory equipment, surgical instruments and medical housings.

Optics and Lighting: Transparent acrylic has a light transmittance of up to 92%, is lightweight and has strong impact resistance, making it an ideal material for optical devices and electronic lighting including lenses, prisms, diffusers and LED lights.

Automotive: In automotive applications, acrylic's impact resistance and transparency are highly valued and it is the preferred material for automotive lamps and interior and exterior decoration.

Consumer Products: It is widely used in various consumer products such as electronics, furniture, musical instruments, etc. CDs and DVDs are also made up of acrylic material.

Why Use CNC Machining to Cut Acrylic?

As CNC machines are computer-controlled, they significantly minimize human errors during operation. CNC machining acrylic allows for achieving high precision and accuracy in parts, enabling flawless cutting and processing of the material, reducing material waste.

CNC machining acrylic makes it possible to manufacture parts with intricate geometric shapes, ensuring dimensional tolerances and precision, thereby enhancing production efficiency.

Conclusion

Acrylic is an excellent alternative to glass, and you can use CNC machining processes to obtain customized parts according to your requirements. Through this comprehensive introduction, you have gained an in-depth understanding of all aspects of CNC machining acrylic. It's time to start your customized PMMA project.

DEK is a global CNC machining manufacturer with a footprint across various industries. We have a range of advanced CNC machining machines and experienced engineers to fully meet your design requirements. Producing parts that meet your expectations is our constant driving force. For the stringent requirements of your project and the professional technical guidance needed, contact us to get the answers you seek.

FAQs

What are the Types of Acrylic Suitable for CNC Machining?

Different types of acrylics have different properties, and choosing the right type of acrylic and the corresponding processing method is important for you to obtain precision parts. Here are a few acrylic materials: cast acrylic, extruded acrylic, continuous cast acrylic, modified acrylic, acrylic composites and laminates, frosted and textured acrylic.

What are Ways to Avoid Acrylic Melting During CNC Machining?

Here are 4 methods recommended:

Use Proper Tools and Settings: Make sure the tools are sharp to reduce heat generation and friction.

Control Machining Speed: Acrylic is a brittle material, so it is important to take light processing and maintain a slow feed rate to reduce heat accumulation when processing acrylic and improve surface finish.

Use a Cooling System: Machining can generate a lot of heat, which can cause stress. Use coolant to assist lubrication, remove chips and maintain stress-free cold processing.

Use a Climbing Milling Direction: This means that the tool rotates in the same direction as the feed. It can ensure a cleaner cut, improve cutting efficiency and surface quality. Compared with traditional methods, the chip evacuation ability is better and the possibility of melting is reduced.

How Much Does Acrylic Cost?

The price of acrylic is affected by many factors, including the type and thickness of acrylic, brand, purchase quantity, market conditions, etc. Considering its durability and recyclability, this material is considered to have a high cost-effectiveness. If you want to know the current acrylic price, contact us today!

When Machining Acrylic, Should I Use Router or Laser Cutting?

Routers are the best choice for applications that require fast cutting and flexible curves. However, if high precision and smooth surfaces are required, laser cutting is recommended. Routers can cut a variety of shapes, including curves and circles, while laser cutting is limited when cutting complex shapes. Compared with laser cutting, routers are less expensive and more suitable for small batch production.