1. What is Acrylic CNC Machining?
CNC machining has become the mainstream high-precision custom processing technology today and is widely used in the manufacturing of various materials. By using CNC machines and pre-programmed instructions, acrylic can be cut, drilled, engraved, and shaped. This is one of the most common and modern processing methods.
Before CNC machining became popular, acrylic processing was mostly performed manually, which inevitably resulted in rough and imprecise outcomes. Today, with the wide adoption of CNC machining, acrylic benefits from high precision, repeatability, efficiency, and the ability to produce complex shapes. It can achieve micron-level accuracy and perfectly meet the high requirements of fields such as signage, optical lenses, display props, precision instrument panels, and medical device components.
2. Acrylic CNC Machining Methods and Processes
A complete CNC machining workflow for acrylic is as follows:
1. Design and Programming (CAD/CAM)
Modeling:
Use AutoCAD, SolidWorks, or Rhino for 2D/3D modeling.
Toolpath Generation:
Generate toolpaths in CAM software such as Mastercam, Fusion 360, or ArtCAM. Common machining operations include profile cutting, pocketing, relief engraving, and drilling.
Code Output:
Export G-code compatible with CNC control systems (e.g., Fanuc, Syntec, Mach3).
2. Material Preparation
Material Selection:
Choose clear, opal, colored, or mirrored acrylic. Cast acrylic is better for engraving, while extruded acrylic is more suitable for simple cutting.
Thickness:
Typical thickness ranges from 2–30 mm. Check tolerance before machining.
Workholding Methods:
- Vacuum table (suitable for large flat sheets)
- Double-sided adhesive tape (for small or irregular parts)
- Mechanical clamps (use protective pads to avoid marks)
3. Tool Selection and Setup
Common Tools:
- Single-flute spiral bit (efficient chip evacuation, prevents melting, recommended for cutting)
- Ball nose end mill (for 3D surface machining and finishing)
- Flat end mill (for pocketing and flat surface finishing)
- V-bit (for lettering and chamfering)
Tool Diameter & Flute Length:
Choose according to part size and detail, avoid excessive tool overhang to reduce vibration.
Tool Installation:
Keep tool protrusion as short as possible to minimize runout and ensure accuracy.
4. Tool Setting and Parameter Configuration
Workpiece Coordinate System:
Typically set at the bottom-left corner or center of the sheet. The Z-zero is set at the material surface.
Cutting Parameters (Reference Values):
- Spindle speed: 18,000–24,000 rpm
- Feed rate: 800–2500 mm/min (depending on tool diameter and material thickness)
- Depth of cut: 0.5–3 mm per pass
Cooling Method:
Air blast or mist cooling. Avoid water cooling, which may cause cracks or cloudiness.
5. Machining Execution
Roughing:
Use a larger tool to quickly remove material, leaving 0.2–0.5 mm allowance.
Finishing:
Use a smaller tool with lower feed rate to achieve fine details and smooth surfaces.
Key Notes:
- Avoid dwelling at the same spot to prevent melting.
- Keep toolpaths continuous to reduce stops.
- Ensure sharp tools and replace them when dull.
6. Post-Processing
Deburring:
Use sandpaper, files, or chemical polishing solutions.
Polishing:
Use buffing wheels with polishing paste, or apply flame polishing (quick, even passes to avoid deformation).
Surface Treatment:
Options include screen printing, UV printing, heat bending, and adhesive bonding.
Final Inspection:
Check dimensional tolerances, transparency, and surface quality (scratches, marks).
3. Acrylic Cutting Parameters: Feed, Speed, and Depth of Cut
This is the key to success or failure. Improper parameter settings may lead to melting, tool sticking, chipping, or surface scratches.
- Spindle Speed: Recommended high speed, typically between 10,000 – 24,000 RPM. High speed generates shearing rather than tearing force, producing smoother cuts.
- Feed Rate: Must match spindle speed. Too slow = excess heat and melting; too fast = excessive cutting force, vibration, or chipping. Recommended chip load (Fz) = 0.05 – 0.15 mm/tooth.
Example: 2-flute 6 mm cutter at 18,000 RPM → Feed = 3,600 mm/min. - Depth of Cut:
- Roughing: ½–⅔ tool diameter (e.g., 3–4 mm for a Ø6 mm tool).
- Finishing: <0.5 mm for best surface quality.
- Cooling: Strongly recommended to use compressed air to remove chips and prevent melting. Avoid water-based coolants, which may cause stress cracking (“crazing”).
4. Which Tools Are Used for Acrylic CNC Machining?
The choice of tool directly determines the machining quality and efficiency.
V-Carving Tool: Used for engraving text and patterns.
Single-Flute Spiral End Mill (Most commonly used and highly recommended): This is the go-to tool for machining acrylic. Its unique single-flute design provides a large chip clearance space, allowing chips to be quickly expelled and greatly reducing chip heat buildup. The spiral design ensures smoother cutting, producing extremely smooth, burr-free sidewalls. It is the ideal choice for finishing operations.
Double-Flute Spiral End Mill: Offers higher cutting efficiency than the single-flute version, but with slightly smaller chip clearance. It is suitable for roughing and semi-finishing when surface finish requirements are slightly lower.
Double-Flute Spiral Down-Cut End Mill (Compression Spiral): The cutting edges are designed with the upper half as a positive spiral and the lower half as a negative spiral. This design generates downward compressive force on both the top and bottom surfaces during the cutting process, effectively preventing edge chipping, especially when cutting multi-layered boards or laminated panels with a protective film.
Ball Nose End Mill: Primarily used for 3D surface carving and engraving.
🔹 Comparison Table
| Tool Type | Common Applications | Advantages | Disadvantages |
|---|---|---|---|
| Single-Flute Spiral End Mill | Most recommended for finishing and precision cutting | Excellent chip evacuation, smooth & burr-free edges, high transparency | Slightly lower efficiency, higher cost |
| Double-Flute Spiral End Mill | Roughing and semi-finishing | Higher cutting efficiency, faster removal | Smaller chip pockets, lower surface quality than single-flute |
| Compression Spiral End Mill | Cutting multilayer or laminated sheets | Prevents chipping on top/bottom edges, clean finish | Higher cost, limited cutting speed |
| Ball Nose End Mill | 3D surface milling, relief carving | Ideal for complex curves and contours | Lower efficiency, less suited for flat finishing |
| V-Bit Engraving Tool | Text and pattern engraving | Sharp tip allows fine detail | Wears quickly, not efficient for large areas |
Preferred material: solid carbide tools for higher hardness and wear resistance compared to HSS.
5. Special Processes: CNC Grinding and Turning
- Acrylic CNC Grinding: Used for optical lenses or components requiring extreme flatness. With diamond or ultra-fine grinding wheels on CNC grinders, material can be removed at micron levels, achieving nanometer-level surface roughness—essential for high-end optical applications.
- Acrylic CNC Turning: For machining acrylic rods into lenses, domes, or cylindrical precision parts. With sharp diamond or polished carbide tools, CNC lathes can produce mirror-like finishes directly.
6. Types of Acrylic Materials for Machining
Not all “acrylic” is the same—different formulations and manufacturing methods affect machinability.
🔹 Comparison Table
| Acrylic Type | Advantages | Disadvantages |
|---|---|---|
| Extruded Acrylic | Low cost, easy thermoforming | Higher risk of melting and tool sticking, rougher finish |
| Cast Acrylic | Higher molecular weight, tougher, better machinability, smooth edges | More expensive |
| Impact-Modified Acrylic | Much higher impact resistance, shatter-resistant | Reduced edge transparency after machining |
| Colored/Patterned Acrylic | Wide aesthetic options, attractive appearance | Pigments may slightly affect machinability |
7. How to Calculate Acrylic CNC Machining Costs
Quotations are typically based on:
- Material Cost: Sheet cost + wastage.
- Machine/Hourly Rate: Depends on machine type (standard vs. 5-axis) and local labor cost.
- Tool Wear Cost: Especially relevant for large or complex jobs.
- Post-Processing Costs: Polishing, flame finishing, printing, assembly.
- Design/Programming Fees: If production-ready CAD/CAM files are not provided.
- Profit & Taxes.
Customers usually provide 2D DXF/DWG or 3D STEP/IGS drawings for accurate quotes.
8. Leading Manufacturers and Processing Companies
- CNC Equipment Manufacturers for Acrylic:
- International: Haas (US), DMG MORI (Germany/Japan), Mecanumeric (France), MultiCam (US).
- Chinese: Beijing Jingdiao, Jiatie, Han’s Laser, Dingtai—high cost-performance, widely used domestically.
- Acrylic Processing Companies:
- Many are regional specialists. Some global giants like Rogers Corporation and Mitsubishi Chemical also provide acrylic component processing.
- In China, the Pearl River Delta and Yangtze River Delta are hubs, serving clients like Apple, Huawei, and Tesla, as well as optical and medical industries.
Conclusion
Acrylic CNC machining is a precise technology integrating material science, mechanics, and cutting processes. Success depends on understanding PMMA’s properties, carefully selecting tools, optimizing cutting parameters, and designing efficient process paths.
By mastering the principles in this guide, acrylic can be transformed into crystal-clear, high-performance products across signage, optics, displays, and medical applications.
For specific projects, it is recommended to consult professional engineers or processing companies for the most cost-effective solution.
