Acrylic CNC Machining: A Comprehensive Guide

07 May 2024

Polymethyl methacrylate (PMMA), commonly known as Acrylic, is a thermoplastic polymer renowned for its unique combination of properties. This transparent plastic material is valued for its exceptional optical clarity, surface hardness, weather resistance, and dimensional stability, positioning it as a superb alternative to glass for various reasons. Noteworthy features include:

 

  • 50% Lighter Than Glass
  • Generally More Affordable
  • Higher Impact Resistance

 

These attributes make acrylic a preferred choice in numerous sectors for both prototyping and production purposes, frequently manufactured with the precision of CNC machining.

3 vs 5 axis
Image: Opt Lasers

Why use CNC Machining to Cut Acrylic?

CNC (Computer Numerical Control) machining stands as an automated manufacturing process that utilizes precise cutting tools to shape raw materials into finished parts or products. It emerges as a popular method for cutting acrylic, owing to several advantages it provides:

Material Compatibility

Acrylic, being a thermoplastic that becomes malleable upon exposure to heat, is well-suited for CNC machining. This inherent quality allows for easy fabrication and shaping of acrylic using this precise and efficient process.

Builds High Precision Parts

CNC machines exhibit an impressive capability for extremely precise cuts, with tolerances measured in thousandths of an inch. This high level of accuracy is particularly crucial when working with materials like acrylic, where the demand for clean edges and precise dimensions is paramount. 

Increased Rate of Production

CNC machining stands out as one of the most efficient methods for fabricating acrylic material, especially when producing small batches of acrylic parts. The process enables faster production compared to manual methods, enhancing efficiency and productivity in acrylic manufacturing. 

 

cnc machining waste

Minimized Waste

Due to its precise manufacturing methods, CNC can cut acrylic with the optimal amount of force, avoiding irreversible damage. This results in the quick and effective production of acrylic components with accurate shapes and sizes. The use of CNC increases accuracy and minimizes waste in the manufacturing process. 

Results in High Repeatability

The automated CNC process guarantees consistency across multiple parts or batches, ensuring stable replication accuracy in each PMMA workpiece. This reliability is a key benefit of CNC machining, particularly in maintaining uniformity and precision in the production of acrylic components.

Saves on Manufacturing Costs

CNC machining can result in significant cost savings in manufacturing, attributed to reduced material waste, increased efficiency, and lower labor costs compared to manual machining methods. The precision and automation of CNC contribute to a more streamlined and cost-effective production process.

acrylics
Image: Getty Images

Applications of CNC Acrylic Parts

CNC acrylic parts find diverse applications across various industries. Some major applications of CNC acrylic parts include:

 

  • Automotive Industry: Automotive manufacturers utilize acrylic CNC machining for producing interior and exterior parts, including headlights, indicators, brake lights, sirens, and gear bearings.
  • Medical Sector: In the medical field, CNC acrylic is commonly employed to manufacture syringes, clear enclosures, and incubators. Additionally, in dental care, PMMA is frequently used for temporary crowns.
  • Consumer Goods: CNC machined acrylic components are prevalent in consumer goods, ranging from smartphones and laptops to signage applications.
  • Architecture and Construction: Acrylic’s high impact resistance and UV light resistance make it suitable for various applications in the construction industry. This includes the production of canopies, panels, and façade designs.

 

cnc turning
Image: Alexander Putter

Considerations for CNC Machining Acrylic

To ensure precision and minimal damage in the final acrylic part, consider these five tips when using CNC cutting machines for cutting acrylic:

Ensure the Acrylic Billet is Secure 

Ensuring the proper securing of your acrylic workpiece to the machine is paramount. Neglecting this step could lead to subpar products, as excessive vibrations may cause the PMMA material to shift or become misaligned while undergoing the machining process.

Choose the Right Cutter 

When CNC machining acrylic, choosing cutters with sharp and robust edges is crucial. This prevents acrylic from melting, which can detrimentally impact both appearance and functionality. It’s advisable to avoid using cutters that have been previously employed with metal, as they may have cuts or jagged edges. Opting for smooth and sharp cutter edges ensures cleaner cuts and improves overall quality.

CNC Milling
Image: Wikimedia Commons

Monitor Cutting Depth and Direction 

When employing a CNC machine for cutting acrylic, the direction of the tool is just as crucial as the cutting depth. It’s imperative to be aware of how your CNC cutter is rotating or spinning—whether it’s to the left or right, or counterclockwise versus clockwise—to maintain accuracy in your design features.

Set the Correct Feed Rate 

Setting the correct feed rate is crucial when operating a CNC machine. While a faster feed rate can prevent acrylic from melting, it may also increase cutting pressure, risking the breakage of the acrylic workpiece. The optimal feed rate for your project depends on factors such as the type of acrylic material selected and the complexity of the part geometry.

Check the Number of RPM 

The feed rate and Revolutions per Minute (RPM) are interdependent factors. Utilizing a higher RPM, coupled with an increased feed rate, can aid in preventing material melt by ensuring the cutting tool moves swiftly through the material, effectively dissipating heat. This coordinated approach helps maintain optimal machining conditions and enhances overall performance.

 

Report by Danny Weller

 

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