Key Differences Between Acrylic and Polycarbonate Machining

We already know that acrylic sheets and polycarbonate sheets are very similar products, sharing many properties while also differing in several key characteristics. In a previous article, we discussed the differences between acrylic and polycarbonate sheets. Here, we focus specifically on the differences when machining and fabricating each material.

We will explore this topic across the following areas:

1. Acrylic CNC cutting vs polycarbonate CNC cutting
2. Acrylic laser cutting vs polycarbonate laser cutting
3. Screen printing on acrylic vs polycarbonate
4. Digital printing on acrylic vs polycarbonate
5. Drilling acrylic vs polycarbonate
6. Acrylic thermoforming vs polycarbonate thermoforming
7. Acrylic bending vs polycarbonate bending
8. Acrylic polishing vs polycarbonate polishing
9. How to choose the right material for your project

1. Acrylic CNC Cutting vs Polycarbonate CNC Cutting

Polycarbonate is better suited to CNC milling due to its toughness. Acrylic is more likely to chip or crack during the machining process.

Tooling

• Sharp Tools: Essential to limit friction and prevent melting. Polycrystalline diamond (PCD) and carbide cutters are ideal for both materials.
• Best Tools: Up-spiral end mills with one or two flutes for milling; 135-degree angle drills for drilling.
• Avoid: Multi-flute tools that cause chips to pack and material to fuse to the tool.

Fixturing

• Avoid Over-tightening: Can cause warping and out-of-tolerance features.
• Alternatives: Use vacuum tables or double-sided tape for securing sheets, especially thinner ones.

Speeds & Feeds

• High Spindle Speed & Feed Rates: Up to 18,000 RPM to prevent melting.
• Polycarbonate has a higher melting temperature, is less prone to melting, and may require slower feed rates.
• Acrylic chips more easily and requires high speeds and feeds.

Coolant

In most cases, compressed air is sufficient for cooling during machining. If additional cooling is required, use water-based coolant — coolants containing organic solvents can damage the material, especially acrylic.

2. Acrylic Laser Cutting vs Polycarbonate Laser Cutting

The key difference is that acrylic is much easier to laser cut and does not leave discoloured edges. Acrylic evaporates directly, avoiding melt and decomposition products along the cut edge.

Is it safe to laser-cut polycarbonate?

• Polycarbonate can be laser-cut with caution, but it is generally not recommended due to poor cut quality, discolouration, and fire risk.
• Better suited for thicker polycarbonate materials with careful precautions.

Challenges of laser cutting polycarbonate:

1. Hazardous Fumes: High-powered lasers can produce toxic gases including carbon monoxide and hydrogen cyanide — proper ventilation is essential.
2. Heat Sensitivity: Polycarbonate can melt, burn, or warp due to heat.
3. Thermal Stress and Warping: Overheating leads to discolouration, distortion, and poor dimensional accuracy.
4. Difficulty Achieving Clean Edges: Edges can melt and lose smoothness.
5. Additives and Coatings: Can produce additional toxic gases when laser cut.

3. Screen Printing on Acrylic vs Polycarbonate

• Surface: Both materials have a smooth surface, making them ideal for screen printing.
• Ink Adhesion: Acrylic allows excellent ink adhesion, resulting in vibrant and durable prints. Ink adhesion on polycarbonate can be slightly less effective, requiring specialised inks for optimal results.
• Drying Time: Acrylic dries quickly, reducing the risk of smudging. Polycarbonate may have a longer drying time, increasing production time.
• Durability: Prints on acrylic are resistant to wear and fading. Prints on polycarbonate are highly durable and impact-resistant, ideal for demanding environments.

4. Digital Printing on Acrylic vs Polycarbonate

Surface and ink adhesion are nearly the same as screen printing. The main difference in digital printing is the use of UV lighting to cure the surface, which requires the material to be UV stable. ExcelitePlas polycarbonate sheets come with a UV coating, so this is not an issue. Before digital printing on acrylic sheets, ensure they are UV stable.

5. Drilling Acrylic vs Polycarbonate

See our dedicated guide: Drilling Acrylic Sheet and Polycarbonate Sheet.

Acrylic is more brittle, making it prone to cracking and chipping during drilling. Polycarbonate is tougher and less likely to crack or chip.

• Use moderate drilling speed and light pressure to prevent cracking.
• Start with a smaller pilot hole and gradually increase the drill size.
• Cool the drilling area with water or compressed air to avoid melting and deformation.
• Securely clamp the sheet to minimise vibration and movement.

6. Acrylic Thermoforming vs Polycarbonate Thermoforming

Thermoforming Polycarbonate

Thermoforming polycarbonate is a well-established process allowing complex shapes with low-cost tooling, large part production, and reduced lead times.

• Softening Temperature: Polycarbonate softens above its glass transition temperature of ~147°C and flows above 155°C. Moulds should be kept above 80°C to produce stress-free parts.
• Outgassing: Polycarbonate absorbs moisture, which can cause surface bubbles during forming. Pre-dry sheets in a hot-air circulating oven at 125°C before forming.
• Applications: Phone frames, electronic displays, shatterproof glazing, vehicle windows, and data storage devices.

Thermoforming Acrylic

Acrylic thermoforming involves heating the sheet until flexible, then shaping it around a custom-designed tool. It provides impact protection, UV resistance, and corrosion resistance.

• Softening Temperature: Acrylic softens and melts at approximately 160°C.
• Outgassing: Acrylic also absorbs moisture. Pre-dry in air-flow ovens at temperatures below the softening point.
• Applications: Signs and sign holders, retail displays, dome skylights, aquarium tanks, and TV screens.

7. Acrylic Bending vs Polycarbonate Bending

See our dedicated guide: Can Polycarbonate Sheet Be Bent?

Polycarbonate's versatility in both hot and cold bending makes it suitable for a wide range of applications, from simple DIY projects to complex professional designs.

1. Hot Bending: Both materials can be bent using a strip heater or bending device. Polycarbonate bending temperature: 180°C–210°C. Acrylic bending temperature: 135°C–177°C.
2. Cold Bending: Easier and more common with polycarbonate due to its strength and flexibility. Suitable for boat windows and windscreens. Acrylic is suitable for slight curves only — it is prone to cracking if bent too sharply without proper heating.

8. Acrylic Polishing vs Polycarbonate Polishing

Both materials can be polished to improve clarity and smoothness, but acrylic is generally easier and more forgiving to work with.

Acrylic Polishing Methods

• Flame Polishing: A fast method using a flame to melt and smooth edges. Best for straight edges and simple shapes.
• Buffing: Uses buffing wheels and polishing compounds to achieve a high-gloss finish. Ideal for both edges and surfaces.
• Sanding: Progressively finer grits of sandpaper to remove scratches before final polishing, often followed by buffing.
• Vapour Polishing: Exposing acrylic to a solvent vapour that melts the surface slightly, resulting in a smooth, clear finish. Used for intricate parts.

Applications: Clear signs, cosmetic displays, aquariums, and items where optical clarity is critical.

Polycarbonate Polishing Methods

• Buffing: Similar to acrylic, but polycarbonate is more prone to heat buildup and scratching during the process.
• Sanding: Start with coarse sandpaper and move to finer grits, followed by buffing. Extra care is needed due to heat sensitivity.
• Vapour Polishing: Less common for polycarbonate as it is more sensitive to chemical damage than acrylic.

Key considerations: Polycarbonate is more heat-sensitive and less scratch-resistant than acrylic. More care is required during sanding and buffing to avoid additional scratches.

Applications: Protective covers, machine guards, and items where impact resistance is more critical than optical clarity.

9. How to Choose the Right Material for Your Project

Polycarbonate offers much higher impact resistance than acrylic, making it ideal for safety glazing and structural applications. Acrylic has a higher gloss finish and superior optical clarity, making it ideal for display cases and signage. Acrylic is easier to crack; polycarbonate is easier to scratch.

Choose Acrylic When:

• Optical clarity and gloss finish are the priority
• The application involves signage, displays, or decorative items
• Cast acrylic is preferred for machining — lower risk of chipping than extruded
• Laser cutting is the primary fabrication method

Choose Polycarbonate When:

• Impact resistance and toughness are critical
• The application involves outdoor structures, safety barriers, or roofing
• CNC milling is the primary fabrication method
• Cold bending is required

Need help choosing the right material or fabrication method? Contact the ExcelitePlas team — we're happy to advise on the best option for your project. You can also browse our full range of acrylic sheets and polycarbonate sheets online.