Acrylic (often called Plexiglas or PMMA) is a favorite among makers and small businesses. It’s lightweight yet strong, comes in transparent and colored sheets, and delivers a sleek professional finish when cut or engraved. From edge-lit LED signs to custom trophies and décor panels, CNC routers unlock endless acrylic project possibilities.
The challenge? Acrylic behaves differently from wood or MDF. Without the right bits, speeds, and finishing techniques, edges can melt, chip, or turn cloudy. This article walks you through everything you need to know to succeed with acrylic on your CNC.
Types of Acrylic for CNC Projects
Not all acrylic is the same. Choosing the right type ensures cleaner cuts and better engravings.
- Cast Acrylic: Engraves with a frosted, white look. Ideal for LED edge lighting because it diffuses light beautifully. Slightly more expensive but produces superior engraving results.
- Extruded Acrylic: Cheaper and more uniform, it cuts smoothly but engraves with less contrast. Best for clear panels or when polishing edges is a priority.
For best results, invest in quality acrylic sheets. TwoTrees offers reliable, smooth-surface acrylic with consistent quality — perfect for CNC work.
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Best Router Bits for Acrylic Cutting & Engraving
Bit selection is critical when working with acrylic. The wrong tool can melt the plastic or leave rough edges. The best bits are designed to clear chips quickly and minimize heat buildup.
- Single-Flute Upcut: Clears chips fast, reducing melting risk. Good for general cutting.
- O-Flute Bits: Designed specifically for plastics. Produces polished edges with minimal chatter.
- Polished Edge End Mills: Keep surfaces smooth and reduce friction heat.
- Ball Nose Bits: Great for engraving curved designs or 3D patterns into acrylic.
Always use sharp bits. Dull edges generate heat, which melts acrylic instead of cutting it.
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CNC Settings for Cutting & Engraving Acrylic
Acrylic requires different feeds and speeds than wood. The goal is to remove chips quickly without melting the edges.
- Spindle speed: Medium RPM (e.g., 12,000–18,000). Too high = melting, too low = chipping.
- Feed rate: Fast enough to evacuate chips. Slower feeds trap heat.
- Depth per pass: Shallow passes (1–2 mm) reduce stress and keep edges smooth.
- Workholding: Use clamps, vacuum tables, or double-sided tape. Avoid point pressure that can crack acrylic.
- Air assist / compressed air: Essential for cooling and clearing chips during both cutting and engraving.
Pro tip: Always test on scrap pieces before cutting your final project. Acrylic sheets vary in hardness between brands.
Finishing Acrylic Projects
Even with perfect cutting, edges may look rough straight off the CNC. Proper finishing transforms them into professional-quality results.
- Wet Sanding: Start with 400 grit, progress to 800–1200 grit. Always wet sand to avoid heat and scratches.
- Flame Polishing: Pass a propane torch quickly over the edge. Heat melts microscopic scratches into a glossy finish. Practice first to avoid bubbles.
- Buffing: Use a polishing wheel with plastic buffing compound for high clarity.
- Protective Film: Keep it on during cutting to prevent scratches. Remove only before engraving.
Common Mistakes & How to Fix Them
- Melted Edges: Caused by high RPMs or slow feed. Fix: increase feed speed, lower spindle speed, and use air assist.
- Chipped Edges: Caused by dull tools or vibration. Fix: replace with sharp bits, secure material firmly.
- Cloudy Engraving: Often happens with extruded acrylic. Fix: switch to cast acrylic for frosted, high-contrast engraving.
- Cracks During Clamping: Caused by over-tightened clamps. Fix: use wide, even clamping pressure or vacuum hold-down.
CNC Acrylic Project Ideas
Acrylic is one of the most flexible CNC materials, suitable for both artistic and functional projects. Here are some ideas:
- Edge-Lit LED Signs: Frosted engravings glow when mounted on an LED base.
- Awards & Trophies: Custom shapes with engraved names and logos.
- Desk Nameplates: Professional and customizable.
- Decorative Wall Panels: Geometric cutouts or engraved designs.
- Machine Guards & Enclosures: Functional, protective panels with transparency.
- Jewelry & Ornaments: Lightweight, stylish, and customizable with engraving.
Best CNC Machines for Acrylic Projects
While almost any CNC router can cut acrylic, stability and precision make the biggest difference in edge quality. Here are recommended machines:
- TTC-450 Pro — Compact and affordable, ideal for small acrylic signs, ornaments, and accessories.
- TTC-6050 — Larger cutting area (600 × 500 mm) for signage, panels, and décor projects.
- TTC-H40 / TTC-H80 — Prosumer-grade routers with added rigidity for professional-quality acrylic cutting.
Conclusion
Acrylic opens up a world of possibilities for CNC projects — from personalized gifts and décor to functional enclosures and signage. With the right material, sharp router bits, correct settings, and careful finishing, you can produce professional-quality pieces with clear, polished edges and crisp engravings.
👉 Get started today with TwoTrees Acrylic Sheets, pair them with a set of precision CNC router bits, and choose the CNC router that fits your space — from the TTC-450 Pro to the H80.
Frequently Asked Questions
What’s the difference between cast and extruded acrylic?
Cast acrylic engraves with a frosted, high-contrast look, perfect for LED-lit projects. Extruded acrylic is cheaper and cuts smoothly but produces less clear engravings.
Can CNC routers cut thick acrylic?
Yes, with the right machine and bits. For sheets thicker than 10 mm, use shallow passes, strong workholding, and air assist to prevent melting.
How do I get polished edges on acrylic?
Use sharp O-flute bits, sand progressively (wet sanding), and finish with flame polishing or buffing compound.
Do I need coolant when cutting acrylic?
Coolant is optional but compressed air is strongly recommended to clear chips and keep edges cool. This prevents melting and weld-back.
