PC 注塑常见问题

Although polycarbonate can support very thin walls and complex geometries, 1mm – 1.02mm ensures proper flow during molding. The table below shows the recommended thickness for different parts.

Polycarbonate has high strength, durability, and toughness, which makes it an excellent material for snap-fit joints. It is commonly used for both rigid and reusable snap fits in automotive parts, electronic housings, and specialized construction panels. See the different uses of PC here.

For the best results, below are tips for drilling polycarbonate:

• Select appropriate drill bit: Opt for standard HSS metal bits or special carbide-tipped bits.
• Drill speed: Maintain a range of 1,000 – 2,000 rpm.
• Proper clamping: Place a wood board under and securely clamp the sheet to prevent movement.
• Technique: Peck drilling.
• Edge distance: drill holes at least 15mm or more from the edge.
• Expansion allowance: Drill holes 0.5mm to 1mm larger than the screw to allow movement.

Since PC picks up mold surface textures very well, high-polish finishes are recommended. Other recommended mold designs are highlighted in the table below.

PC is more flexible compared to metal. Therefore, it requires sturdy support during machining to avoid deflection.

For deeper parts, steeper angles (up to 3^o or higher) may be required because of PC’s rigid nature and high friction. Recommendations for different use cases are as follows:

• Lightly textured or smooth surfaces: 1^o 至 2^o
• Deep cavities or ribs: 2^o to 3^o for walls over 25 – 50mm
• Textured surfaces: 1.5^o – 2^o per side for every 0.025 mm of texture depth
• Female vs male (interior vs exterior): 1.5^o – 2.5^o for female and 3^o to 5^o for male cores.

For curved cuts, a jigsaw with a high-speed steel blade is recommended. Always use fine-toothed blades (10-18 teeth per inch) to prevent chipping or melting.

• Circular saw: This is the best choice if you want to achieve a straight cut on large or thick sheets measuring 3mm-10mm+.
• Jigsaw: Your best bet for curved or complex shapes.
• Utility knife: Effective for thin sheets (<3mm).
• Band saw: Suitable for complex shapes and thicker sheets.
• Rotary tool: Appropriate for intricate cuts

1. Sanding (best for smooth or matte edges: Start with 150 to 200 grit wet paper to remove the burr and move to 400 to 600 grit for a smooth finish. For matte edge, finish with 1,000 to 2,000 grit.
2. Scraping (best for rapid removal): Hold the scraper at a 45-degree angle to the edge and scrape in one direction to avoid creating new imperfections.
3. Filing (best for large sheets): File gently along the edge to remove burs and smooth down the sharpness.
4. Polishing (best for crystal clear edge): Use a bench grinder or drill with a soft cotton buffing wheel and polishing compound to buff the sanded edge.

Pre-drying involves the use of a hot-air circulating oven, preferably a dehumidifying oven, to dry the polycarbonate sheet at 121^oC (250^oC). The drying duration will depend on the thickness of the material as follows:

• 093″ (2.4mm): ~4 hours
• 118″ (3mm): ~6 hours
• 150″ (3.8mm): ~8 hours
• 177″ (4.5mm): ~12 hours
• 236″ (6mm): ~24 hours

甲基丙烯酸甲酯是结构性和高冲击性应用的最佳选择。双组分环氧树脂具有出色的耐环境性，而氰基丙烯酸酯则适用于快速修复。.

Hot air welding: Apply hot air using a plastic welding gun (≈ 400^oC – 425^oC) to the joint and matching polycarbonate filler rod. Move with smooth, steady strokes.

Solvent welding: Apply dichloromethane (DCM) to the welding surfaces. The solvent will melt the plastic on contact. Clamp the parts together while the solvent cures.

The list of chemicals and materials that may yellow or crack polycarbonate includes:

• Ammonia-based cleaners: e.g., Windex
• Solvents: e.g., Acetone, benzene, methyl ethyl ketone (MEK), and gasoline
• Harsh alkalines or acids
• Abrasive cleaners: e.g., Scouring powders
• Paper towels
• Scrapers or squeegees
• High-pressure washers

Dull tools increase friction, which leads to heat generation and melting. Use high spindle speed and lower feed rates to achieve a clean cut. Other important tips you should keep in mind include:

• Use sharp carbide tools for superior surface finishes

• Water-based coolants or air blast play the dual role of removing chips and keeping the material cool

• Clear chips quickly to avoid heat build-up
• Avoid excessively thin walls
• Use moderate, even pressure for workholding

Consider annealing after machining if the part has high-stress areas

Below are the recommended injection molding parameters for PC to achieve high-quality, transparent, and durable parts.

Cooling makes up 60% to 80% of the cycle times. Use conformal cooling channels to optimize heat removal. Keep the temperature differential between the coolant inlet and outlet within 2oC to 5oC to prevent hot spots.

For 3D printing using FDM, use an enclosure and keep the ambient temperature high. Increase bed temperature (100^oC – 130^oC), use brim (20+ lines) to increase surface area contact with the bed, optimize adhesion using specialized adhesives, lower print speed, and minimize cooling fans.

For injection molding, focus on uniform wall thickness, balance cooling channels, increase mold temperature, optimize packing pressure, and optimize gate location.

Apply solvent vapor to smooth micro-scratches and achieve superior optical clarity. Use masking film to protect the surface from microscopic scratches. Utilize highly polished mold surfaces to ensure maximum light transmission. Transparent PC parts should be handled with lint-free gloves.

Polycarbonate is an amorphous polymer. Therefore, it exhibits low and uniform shrinkage compared to semi-crystalline materials. Shrinkage is often influenced by wall thickness, mold temperature, packing pressure, and flow rate. Around 90-95% of shrinkage happens in the mold, while the remainder occurs within a few hours of ejection.

For minor scratches, wash with mild soap and water and allow to dry. Apply polishing compound to a microfiber cloth and rub the scratch in circular motions. Apply light to moderate pressure until the scratches disappear. For deeper scratches, use wet or dry sandpaper. Start with 600 to 800 grit, then move to 1,000 to 1,500 grit.

Another way to prevent yellowing of polycarbonate sheet is to apply UV coatings. Reapply the coatings or sprays every 1-2 years to maintain protection. Clean regularly with mild soap and warm water to remove debris that can trap heat and accelerate degradation.

Polycarbonate expands roughly 6x more than metal, which makes room for movement that is essential for preventing stress. The following installation and fastening techniques will prevent cracks or buckling.

• Leave expansion gaps, typically 3-5mm per meter of sheet, around the edges of the sheets
• Pre-drill holes that are 2-3mm larger than the screw shank to allow expansion and contraction
• Do not overtighten to avoid stress concentration
• Ensure the UV-protected side faces outward for multiwall sheets

Packing more materials into the mold will offset shrinkage, especially for thick areas. Lowering the mold temperature forces faster cooling on the surface. Make sure the material sets fully before ejection to prevent surface collapse.

Texts like “This side up” or “UV side” may be used to tell you the UV-coated side. On some PC panels, the UV-coated side may have a different finish, such as notched or a distinct texture, compared to the smoother non-coated side.