We already know that acrylic sheets and polycarbonate sheets are very similar products, sharing many properties while also differing in several characteristics. In a previous blog, we discussed the differences between acrylic sheets and polycarbonate sheets. In this blog, we will focus specifically on the differences between machining acrylic and machining polycarbonate.
- Acrylic CNC cutting VS Polycarbonate CNC cutting
- Acrylic Laser cutting VS polycarbonate laser cutting
- Screen Printing on Acrylic sheet VS Screen printing on polycarbonate sheet
- Digital printing on Acrylic sheet VS Digital printing on polycarbonate sheet
- Drilling on Acrylic sheet VS Drilling on polycarbonate sheet
- Acrylic Thermoforming VS polycarbonate thermoforming
- Acrylic Bending VS polycarbonate bending
- Acrylic polishing VS Polishing Polycarbonate
- How to choose the right material for your next project?
1, Acrylic CNC cutting VS Polycarbonate CNC cutting
CNC machining and engineering Tooling
polycarbonate is better for machining and is particularly well-suited to CNC milling, Acrylic is more like to chip or crack during machining process.
- Sharp Tools: Essential to limit friction and prevent melting. Carbide and polycrystalline diamond (PCD) cutters are ideal for both Acrylic and polycarbonate.
- Best Tools: Up-spiral end mills with one or two flutes for milling; 135-degree angle drills for drilling.
- Avoid: Multi-flute tools that can 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 perspex sheets, especially thinner plastic sheets.
Speeds & Feeds
- High Spindle Speed & Feed Rates: Up to 18,000 RPM to prevent melting.
- Polycarbonate sheet has higher melting temperature, less prone to melting, and may require slower feed rates.
- Acrylic sheet Chips more easily; requires high speeds and feeds.
Coolant
- In most cases, compressed air is sufficient for cooling acrylic and polycarbonate parts during machining. However, the need for cooling can vary based on speeds, feeds, and the type of cutting operations. If additional cooling is required, use water-based coolant, as coolants containing organic solvents can damage the part, especially acrylic.
2, Acrylic sheet laser cutting VS Polycarbonate sheet laser cutting
Is It Safe To Laser-Cut Polycarbonate Sheet?:
- Polycarbonate can be laser-cut with caution, but it's generally not recommended due to poor cut quality, discoloration, and fire risk.
- Better suited for thicker polycarbonate materials with careful precautions.
Challenges of Laser Cutting Polycarbonate:
- Hazardous Fumes: High-powered lasers can produce toxic gases like carbon monoxide and hydrogen cyanide, requiring proper ventilation.
- Heat Sensitivity: Polycarbonate can melt, burn, or warp due to heat.
- Thermal Stress and Warping: Overheating can lead to discoloration, distortion, and poor dimensional accuracy.
- Difficulty Achieving Clean Edges: Edges can melt and lose smoothness.
- Effects of Additives and Coatings: Additives and coatings can produce additional toxic gases.
3, Screen Printing on Acrylic Sheet vs. Printing on Polycarbonate Sheet
- Surface: Both material have a smooth surface, making them ideal for screen printing.
- Ink Adhesion: Acrylic allows for excellent ink adhesion, resulting in vibrant and durable prints. ink adhesion on polycarbonate can be slightly less effective compared to acrylic, requiring specialized inks for optimal results.
- Drying Time: Acrylic dries quickly, reducing the risk of smudging. Polycarbonate may have a longer drying time, which can increase production time.
- Durability: Prints on acrylic are resistant to wear and fading, suitable for long-term applications. Prints on polycarbonate are highly durable and resistant to impact, making them ideal for demanding environments.
4, Digital printing on Acrylic sheet VS Digital printing on polycarbonate sheet
Surface and ink adhesion are nearly the same with screen printing.
The main difference in digital printing on acrylic and polycarbonate is the using of UV lighting to dry the surface, which requires the material to be UV stable. Excelite Polycarbonate sheets come with UV coating, so this is not an issue. However, before doing digital printing on acrylic sheets, ensure that they are UV stable.
5, Drilling on Acrylic sheet VS Drilling on polycarbonate sheet
Acrylic sheet is more brittle, making it prone to cracking and chipping during drilling. Polycarbonate sheet 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.
Drilling can generate heat, so it's essential to cool the drilling area with water or compressed air to avoid melting and deformation. Polycarbonate also requires cooling during drilling to prevent heat build-up, but it is less prone to melting compared to acrylic.
Properly secure the acrylic sheet to minimise vibration and movement.
6, Acrylic Thermoforming VS polycarbonate thermoforming
Thermoforming of Polycarbonate
Thermoforming polycarbonate sheet is a well-established process that allows for the creation of complex shapes with significant cost and performance advantages. Benefits include low-cost tooling, large part production, and reduced lead times.
The Process
Thermoforming polycarbonate involves heating, shaping, and cooling the plastic sheet. Techniques vary, from simple drape forming, which uses heat to mold the sheet over a positive or negative form, to vacuum and pressure forming, which use pressure or a vacuum to shape the heated sheet.
Softening Temperature
Polycarbonate softens gradually above its glass transition temperature of about 147°C (297°F) and flows above 155°C (311°F). Molds should be kept above 80°C (176°F) to ensure the production of stress-free parts.
Outgassing
Polycarbonate panels has a high outgassing rate and absorbs moisture, which can cause surface issues, like bubble during thermo forming. To prevent this, sheets should be dried in a hot-air circulating oven at 125°C (257°F) to remove moisture before forming.
Applications
Thermoformed polycarbonate is used in a variety of applications, including:
- Cellphone frames and screens
- Electronic displays for TVs, monitors, and tablets
- Shatterproof and bulletproof glass
- Vehicle windows and windshields
- Data storage devices like CDs and DVDs
Thermoforming of Acrylic sheet
Acrylic thermoforming involves heating the acrylic sheet until flexible, then shaping it around a custom-designed tool. Thermoformed acrylic provides impact protection, resistance to UV radiation and corrosion, and offers flexible ordering with short lead times.
The Process
Acrylic can be thermoformed using various equipment types, including vacuum, pressure, or stretching devices, and heating methods like coiled nichrome wire, hot air ovens, and quartz tubes. These methods offer different life spans and efficiency levels.
Softening Temperature
Acrylic softens at higher temperatures and melts at 320°F (160°C). While household use won't melt acrylic, precautions like using trivets for hot items are recommended to prevent damage.
Outgassing
Acrylic also has a high outgassing rate and absorbs moisture, which can cause bubbles during heating. Pre-drying in air-flow ovens at temperatures below the softening point is recommended.
Applications of Acrylic fabrication
Thermoformed acrylic is clear, durable, and shatter-resistant, making it ideal for:
- Signs and sign holders, Sign stand
- Retail displays and retail shelves
- Acrylic Brochure displays
- Dome Skylights
- TV screens
- Submarine windows and aquarium tank.
Acrylic Polishing Methods:
Flame Polishing: A fast method using a flame to melt and smooth the 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: Involves progressively finer grits of sandpaper to remove scratches before final polishing. Often followed by buffing.
Vapor Polishing: Involves exposing the acrylic to a vapor of a solvent that melts the surface slightly, resulting in a smooth, clear finish. Used for intricate parts.
Applications: Clear signs, cosmetic displays, aquariums, and other items where optical clarity and aesthetic appeal are crucial.
Polycarbonate Polishing Methods:
Buffing: Similar to acrylic, buffing is used to polish polycarbonate. However, polycarbonate is more prone to heat buildup and scratching.
Sanding: Starting with coarse sandpaper and moving to finer grits, followed by buffing. Extra care is needed due to polycarbonate’s sensitivity to heat and scratching.
Vapor Polishing: Less common for polycarbonate because it is more sensitive to chemical damage than acrylic.
Considerations:
Heat Sensitivity: Polycarbonate is more sensitive to heat compared to acrylic. Excessive heat during polishing can cause warping or melting.
Scratch Resistance: Polycarbonate is less scratch-resistant than acrylic. More care is required during the sanding and buffing process to avoid additional scratches.
Applications of polycarbonate fabrication: Protective covers, machine guards, and other items where impact resistance is more critical than optical clarity.
How to choose the right material for your custom fabrication project?
Polycarbonate offers much higher impact resistance than acrylic, making it ideal for applications like bullet-proof panels. Acrylic has a high gloss finish and is more transparent, making it ideal for display cases. Acrylic is also easier to crack, while polycarbonate is easier to scratch.
Acrylic machining:
- Preferred Type: Cast acrylic is better than extruded due to lower risk of cracking or chipping.
- Toolpath Strategies: Require careful selection to avoid chipping.
- Heat Sensitivity: Sharp tools and lower feed rates are essential to prevent heat buildup and melting.
- Cooling: Acrylic can be kept in a freezer before machining to remain cool.
Polycarbonate machining:
- Suitability: Better for machining due to toughness and impact resistance, especially with CNC milling.
- Tool Sharpness: Critical to prevent heat buildup and melting.
- Toolpath Strategies: Standard strategies are effective due to lower chipping risk.
- Temperature Range: Allows for more aggressive strategies, saving time and money.
