Acrylic, also known as polymethylmethacrylate (PMMA), is a versatile plastic material that can also be used as a glass substitute. It is widely used in CNC machining due to its excellent properties. This article is a complete guide to CNC acrylic, providing information on CNC acrylic methods, applications for CNC acrylic parts, and tips for machining acrylic parts.


What is Acrylic(PMMA)?
Acrylic, also known as PMMA (Polymethyl Methacrylate), is a synthetic polymer made from the polymerization of methyl methacrylate monomers. It’s widely recognized for its glass-like transparency, high impact resistance, and ease of processing. PMMA is a versatile material used in a variety of applications, including signs, displays, windows, and even medical devices.
Physical Properties of Acrylic (PMMA)
- Transparency: PMMA is often called “acrylic glass” or “plexiglass” because of its glass-like clarity. It has a high light transmission rate (about 92%), even higher than that of glass. This makes it an excellent substitute for glass in many applications.
- Lightweight: Acrylic is much lighter than glass, making it easier to handle and transport.
- UV Resistance: PMMA has good resistance to UV light, which makes it durable and stable when exposed to sunlight, unlike many other plastics which may yellow or degrade over time.
- Impact Resistance: While PMMA is more brittle than some other plastics (like polycarbonate), it is still more resistant to shattering than glass, making it safer in applications like windows and shields.
- Scratch Resistance: While PMMA is more scratch-resistant than some plastics, it can still get scratched relatively easily compared to glass or polycarbonate.
- Thermoformability: Acrylic can be heated and molded into various shapes, which is useful for creating custom designs and intricate forms.
What Is CNC Machining Acrylic?
CNC Machining Acrylic refers to the process of using Computer Numerical Control (CNC) technology to cut, shape, and finish acrylic, a popular thermoplastic material. Acrylic, commonly known by trade names like Plexiglass, Lucite, or Perspex, is widely used in industries such as signage, automotive, architecture, and consumer products due to its transparency, lightweight, and easy-to-machine properties.
CNC Machining Process for Acrylic
- CNC Machine SetupCNC machining involves the use of automated machines like CNC routers or CNC mills, which are controlled by pre-programmed computer software. These machines perform highly precise cuts based on the 2D or 3D digital design of the part or product. Acrylic sheets or blocks are fixed onto the CNC machine bed, and tools like cutters, drills, and mills are used to shape the material.
- Material SelectionAcrylic comes in different grades and thicknesses, and the machining process can vary depending on the type of acrylic. There are two main types of acrylic used in CNC machining:
- Extruded Acrylic: More affordable but slightly less clear and more prone to surface imperfections.
- Cast Acrylic: Higher quality, clearer, and ideal for precise machining.
- Design & ProgrammingThe first step in the CNC process is creating a digital design using CAD (Computer-Aided Design) software. This design is then converted into a CNC-compatible file format (e.g., G-code). The code tells the CNC machine how to move the cutting tools, at what speeds, and the depth of each cut.
- Cutting and ShapingCNC machines use different types of tools (end mills, drills, or engraving bits) to cut, mill, or engrave acrylic. Depending on the complexity of the design, multiple passes may be needed to achieve the desired shape and smoothness.
Common PMMA Machining Methods
Here, we’ll explore five common CNC machining techniques for acrylic: CNC Milling, CNC Drilling, CNC Engraving, CNC Acrylic Turning, and CNC Acrylic Cutting. Each method serves different purposes and allows for intricate designs, precise cuts, and high-quality finishes.


CNC Milling
CNC Milling is a widely used process for shaping and cutting acrylic into specific forms. In this method, the material is held in place while a rotating cutting tool moves along multiple axes to carve out the desired shape.
Key Features
- Multiaxis Capability: CNC milling uses multi-axis machines (typically 3, 4, or 5 axes) to make intricate cuts and create complex shapes.
- Precision: Highly accurate, CNC milling allows for precise control over cutting depth, angle, and shape.
- Applications: Ideal for creating detailed shapes, slots, and cavities, commonly used in producing prototypes, signage, decorative elements, and functional parts.
CNC Drilling
CNC Drilling is specifically used to create holes in acrylic sheets. This process involves rotating a drill bit that moves vertically into the acrylic material. CNC drills can create holes of various sizes and depths with high precision.
Key Features
- Types of Holes: CNC drilling can create both through-holes (holes that go all the way through the acrylic) and blind holes (holes that stop at a certain depth).
- Hole Sizes: The CNC machine can accommodate different drill bit sizes to produce holes with varying diameters.
- Speed: Drilling is generally faster than other machining methods due to its simple motion and direct cutting process.
Applications
- Creating holes for screws or bolts in acrylic assemblies
- Making holes for light fixtures or display stands
- Drilling for mechanical fasteners or connectors in products like furniture or signage
CNC Engraving
CNC Engraving involves using a rotating engraving tool to carve patterns, text, or designs onto the surface of the acrylic. This process is often used for adding branding, logos, decorative features, or custom designs onto acrylic panels.
Key Features
- Surface Detailing: Engraving is ideal for creating intricate surface designs, logos, or fine text.
- Depth Control: CNC engraving allows for precise control over the depth of the engraving, providing a 3D effect.
- Tools: Typically, diamond-tipped or carbide engraving bits are used for fine, detailed work.
Applications
- Personalization of products like trophies, awards, and nameplates
- Logo engraving for branding and signage
- Decorative patterns for acrylic art pieces
CNC Acrylic Turning
CNC Acrylic Turning is a method used to create cylindrical or rotationally symmetric shapes from acrylic. This process involves rotating the acrylic material while a cutting tool is applied to shape it, similar to how wood or metal is turned.
Key Features
- Rotational Symmetry: This process is particularly suitable for creating round or cylindrical objects such as rods, tubes, and spheres.
- Surface Finish: CNC turning can produce a smooth, polished surface, especially when combined with a polishing or flame treatment afterward.
- Precision: The rotational nature allows for high-precision dimensions and smooth surfaces, which is critical for products like lenses, optical components, or decorative items.
Applications
- Making acrylic tubes, rods, and cylinders for various applications
- Producing acrylic handles, knobs, or caps
- Creating rotationally symmetric parts for engineering and automotive use
CNC Acrylic Cutting
CNC Acrylic Cutting is a process that uses a rotating tool to cut through acrylic sheets, creating precise straight or curved cuts. It can be used to cut large sheets of acrylic into smaller pieces or to create complex shapes and designs.
Key Features
- Straight & Curved Cuts: CNC cutting allows for both straight lines and intricate curves, making it versatile for a range of applications.
- Thickness Control: CNC cutting can handle different thicknesses of acrylic, from thin sheets to thicker panels.
- Speed & Efficiency: CNC cutting is highly efficient for large-scale production and is ideal for mass production of parts or products.
Applications
- Cutting acrylic sheets for custom-sized parts or panels
- Creating intricate designs and shapes for decorative elements
- Cutting parts for display cases, furniture, and signage
Key Benefits of CNC Machining Acrylic
Precision
CNC machining allows for high precision, which is essential for applications where fine details or tight tolerances are required (e.g., optical applications, signage).
Complex Geometries
CNC machines can create intricate designs, including custom shapes, curves, and patterns, which would be difficult or impossible to achieve manually.
Clean Cuts
Unlike laser cutting, which can cause material burn, CNC machining provides cleaner, sharper cuts with little material distortion.
Versatility
CNC machining can be used for both 2D cutting and 3D shaping, allowing acrylic to be molded into complex shapes or detailed engravings.
Speed & Efficiency
Once the design is set up and the CNC machine is programmed, the actual machining process is automated and can be completed relatively quickly, especially for large production runs.
Tips for Successful CNC Machining of Acrylic Parts
When machining acrylic (PMMA), there are several best practices to keep in mind to ensure high-quality results and avoid common issues.
- Choose the right tool
Use sharp tungsten carbide tools or special cutting tools to reduce the risk of chipping and melting, and ensure fine and smooth cutting.
- Control cutting speed
Maintain a moderate cutting speed. Too high will cause overheating and deformation, while too low may cause surface unevenness and tool wear.
- Cooling and heat dissipation
Use coolant or air jet to reduce heat accumulation, prevent acrylic from melting or deformation, and also help remove chips.
- Reasonable fixation and support
Clamp the acrylic evenly to prevent deformation. For large materials, use supports to reduce vibration and prevent errors.
- Perform test cutting
First use waste materials to test cutting parameters to ensure the accuracy of actual processing and avoid waste of finished materials and misoperation.
Surface Finish Options for CNC Machined PMMA Parts


As-Machined Finish
An as-machined finish refers to the surface texture left directly after the CNC machining process without any additional post-processing steps. This finish is generally smooth but may still have visible tool marks, slight roughness, or minor imperfections.
Best For
- Prototyping or functional parts where high appearance quality is not essential.
- When subsequent polishing or coating is planned.
Flame Polishing
Flame polishing is a technique where the edges or surfaces of the acrylic are passed through a controlled flame, causing the surface to melt slightly and smooth out. This method is often used for sharp edges or detailed cuts, giving acrylic a glossy, clear finish.
Best For
- Edges that need to be smooth and transparent.
- Display or decorative parts where high clarity is required.
Mechanical Polishing
Mechanical polishing involves using a buffing wheel or polishing pad with a compound (such as fine polishing paste or abrasive pads) to smooth the surface of the acrylic. This method works well for flat surfaces or large-area polishing.
Best For
- Larger flat surfaces or detailed areas that require a mirror-like finish.
- When a high-gloss surface is essential.
Wet Sanding
Wet sanding is a process where abrasive sandpaper is used with water to smooth the surface of the acrylic. This method is effective for reducing visible tool marks or rough areas and prepares the surface for further polishing or coating.
Best For
- Removing deep scratches, tool marks, or rough finishes.
- Preparing the acrylic for flame polishing or other finishes.
Chemical Polishing
Chemical polishing involves applying a chemical solution that reacts with the acrylic surface, slightly dissolving it to create a smooth, polished look. This method can be used to achieve a clear, glossy finish without the need for physical abrasion.
Best For
- Large volumes of parts where mechanical polishing is impractical.
- Parts with complex shapes or intricate details that are difficult to polish manually.
Conclusion
Acrylic (PMMA) CNC machining is a process commonly used to create clear and high-gloss parts for a variety of applications from prototyping to end products. CNC machining offers high-precision and complex shape processing capabilities, ensuring dimensional accuracy and surface finish of the finished product.If you want to custom CNC machine PMMA parts, EASIAHOME is the best CNC machining manufacturer for you.EASIAHOME has state-of-the-art CNC machines and years of experience in providing CNC machining solutions.
Frequently Asked Questions
Q: What is the best CNC bit for cutting acrylic?
A:The best CNC bit for cutting acrylic is a single-flute spiral carbide bit. It provides a clean cut, reduces heat buildup, and minimizes the risk of cracking or chipping during the machining process.
Q:What are the applications of acrylic CNC machining?
A: Acrylic CNC machining is used in a variety of applications, including signage, display panels, protective covers, lighting fixtures, and optical components, thanks to its clarity and ease of fabrication.
Q: How does PMMA compare to other plastics in CNC machining?
A: PMMA is more brittle but offers superior optical properties compared to polycarbonate or ABS. It requires precise machining to avoid cracking or surface imperfections.
Q:What are common challenges in machining PMMA?
A: Challenges include avoiding cracks or burns, ensuring a polished finish, and managing stress buildup during machining, which can lead to warping.
Q: What are the advantages of using PMMA for CNC machining?
A: PMMA is lightweight, durable, easy to machine, and provides excellent optical clarity, making it ideal for applications like displays, lenses, and light guides.