PC

High toughness, excellent impact strength, transparent. PC is a widely used thermoplastic with excellent mechanical properties, outstanding toughness, good heat resistance, and easy toprocess.

Can be optically transparent.

Words Are Good.
Examples Are Better.

 

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Contents

1.Advantages of PC Injection Molding

2.Applications of PC Molded Parts

3.Tips for Better Surface Finish

4.Optimal Molding Parameters

5.Case Study

1. Advantages of PC Injection Molding

• Excellent mechanical strength and toughness
• High impact resistance and heat resistance
• Good dimensional stability and transparency
• PC injection molding is widely used across electronics, automotive, lighting, medical devices, and industrial equipment.

We have produced PC molded components for:

• Electronics and lighting products: transparent housings, lamp covers, and protective shields
• Automotive parts: instrument panels, protective covers, and interior components
• Mechanical and industrial parts: gears, structural components, and enclosures

2. Application Fields of PC Injection Molding

Instrumentation & Light Industry: Electronics & Light Industry: housings, display panels, protective covers, brackets, and lighting components

Construction & Industrial Equipment: transparent panels, safety

Automotive: interior and exterior parts, dashboards, instrument panels, lamp covers, and protective shields

3. How to Achieve a Good Surface Finish for PC Injection Molded Parts

The appearance of PC parts depends on mold quality, processing, and materials. Due to PC's heat resistance and transparency, careful temperature control and surface protection are essential.

3.1 Mold Quality

Cavity finish: Scratches, pores, or roughness are highly visible on transparent or glossy PC parts. We ensure mirror-polished cavities and use hard chrome plating or nickel plating where necessary.

Cleanliness: Any oil, dust, or release agent residue will be highly visible on PC surfaces. Regular mold cleaning is strictly maintained.

Draft angle: Insufficient draft can cause scratches or drag marks, especially on large transparent parts. Draft angles are carefully reviewed in DFM.

Venting system: Poor venting can create burn marks, streaks, or dull areas. Venting is optimized for smooth flow, particularly for thick or transparent sections.

Gate and runner design: Sharp transitions or small gates can induce shear, leading to flow lines or haze. Mold flow simulations are conducted to optimize gate placement and runner size.

3.2 Molding Parameters

Injection speed: Too fast can create flow marks; too slow can cause incomplete filling or surface haze. Balanced speed is critical for transparent or glossy PC parts.

Cooling system: Uneven cooling may lead to warpage, birefringence, or dull surfaces. Cooling channels are carefully designed for uniform temperature control.

Holding pressure & time: Insufficient pressure or time may cause voids or surface sink marks; proper settings are essential for maintaining clarity and surface smoothness.

Melt temperature: PC requires higher melt temperatures than ABS. Low melt temperature reduces flowability and transparency; excessive temperature can cause degradation. Temperature is carefully controlled to achieve optimal surface quality.

3.3 Raw Materials

Granule uniformity: Non-uniform pellets lead to inconsistent flow, haze, or surface streaks. We strictly select and screen materials.

Moisture content: PC is highly hygroscopic; even slight moisture can cause bubbles, surface roughness, or cloudy appearance. Materials are thoroughly pre-dried.

Additive and colorant dispersion: Uneven mixing can result in streaks, color inconsistency, or gloss reduction. High-quality, well-dispersed additives are used.

Impurities: Foreign particles can cause visible spots or scratches, especially on transparent parts. We ensure materials are clean and impurity-free.

Recycled content: Excessive recycled PC can reduce clarity and gloss. Proportion is strictly controlled for high-quality parts.

4. Best Parameters for PC Injection Molding

4.1 Key Properties

Moisture Sensitivity: PC is highly hygroscopic; materials must be thoroughly dried (below 0.02% moisture) at 120 °C for 3–4 hours to prevent bubbles and poor appearance.

Flow Behavior: The melt has high viscosity; higher injection temperature and pressure improve flow and reduce internal stress.

Shrinkage Rate: 0.5–0.7%, ensuring good dimensional stability.

Machine Type: Screw-type injection machines are recommended for uniform melting and stable molding quality; all our production lines use screw-type machines.

Injection Volume: Ideal to use 40–70% of the machine's maximum shot size for optimal control of melt temperature and part quality.

Runner Design:

-Main runner ≤100 mm (preferably around 50 mm)

-Sub-runner 6–8 mm for balanced flow and easy filling

Ejection Force: Should be gentle to avoid surface stress marks or cracking.

Post-Treatment: Annealing at 120 °C for 2–3 hours helps to release internal stress and improve mechanical strength.

4.2 Typical Molding Parameters

The molding parameters for PC parts vary depending on the material grade, part geometry, and required surface quality. Proper control of barrel temperature, mold temperature, and injection pressure is essential to achieve high-quality, dimensionally stable parts.

These parameters serve as a general guideline; fine-tuning may be required based on part complexity, thickness, and tooling design to ensure optimal surface finish, mechanical performance, and dimensional stability.

5. PC Injection Molding Case Study

5.1 Product Basic information

Product Name: Lamp Panel Mounting Base

Product Color: Black

Product Size: 125.63 x 201 x 137.99 mm

Average thickness：2 mm

Cavity：1 Cavity

Product Material: Makrolon 2407(PC)

Product appearance Requirements: No welding line, No any appearance defects

5.2 Preliminary Analysis

To ensure manufacturability, multiple aspects were analyzed at the early development stage.

5.2.1 Product Structure and Process Adaptability

The main wall thickness is about 2 mm and generally uniform, minimizing sink marks and warpage risks. Draft angles are sufficient for smooth ejection without surface scratches. Rib and reinforcement structures were optimized to balance strength and material usage.

5.2.2 Molding Simulation Analysis

MoldFlow simulation predicted balanced filling with minor air-trap risk. The maximum injection pressure at V/P switchover is 79.82 MPa, and melt front temperature (310–341 ℃) is within the suitable molding range.

5.2.3 Cooling and Defect Risk

Cooling layout analysis (coolant 100 ℃, Re = 16355) indicates good heat dissipation. Main risks include localized air traps, weld lines, and potential shrinkage (max depth 0.156 mm, vol. shrinkage 8.98%). Warpage is controlled within 0.61 mm overall, requiring further optimization.

5.3 Design Optimization

Based on the defects and risks identified in the preliminary analysis, the following optimizations were implemented:

5.3.1 Product Structure

Wall thickness distribution was refined to achieve more uniform 2 mm sections, reducing sink marks and shrinkage. Venting slots (0.2–0.3 mm wide, 0.03–0.05 mm deep) were added to air-trap and weld-line areas to improve gas release and appearance.

5.3.2 Gate and Runner System

Gate locations were adjusted to balance flow and avoid thin-wall areas. Local runner sections were slightly enlarged to reduce flow resistance and ensure stable pressure transmission.

5.3.3 Process Parameters

Holding time was extended to 5–8 s, with holding pressure increased to 85–90% of peak value. Melt temperature was optimized to 290–310 ℃ for better flow and surface quality. Cooling layout was refined for temperature uniformity.

5.4 Post-Optimization Analysis

5.4.1 Filling Performance

Filling time remained about 2.1 s with improved flow balance and reduced air-trap risk.

5.4.2 Pressure & Temperature Distribution

Injection pressure stabilized at 75–80 MPa, and melt-front temperature narrowed to 315–335 ℃, improving temperature uniformity and appearance.

5.4.3 Defect Reduction

Weld-line strength and air venting improved; maximum sink depth decreased to below 0.08 mm; volume shrinkage variation reduced within 2%; total warpage decreased to <0.4 mm (Z-axis <0.3 mm).

5.4.4 Other Factors

Clamping force remained stable at 120–125 T; cooling efficiency consistent with Reynolds number >15,000, ensuring cycle stability.

5.5 Summary & Recommendations

5.5.1 Results

The optimized design effectively solved key issues including air traps, weld lines, shrinkage, and warpage.

5.5.2 Production Recommendations

Follow optimized settings: melt 290–310 ℃, mold 80–120 ℃, holding 5–8 s, pressure 85–90%.

Ensure vent slot precision, cooling flow balance, and wall thickness tolerance during mold fabrication. Regularly monitor temperature, pressure, and dimensional stability in mass production.

5.5.3 Conclusion

The optimized molding plan demonstrates strong feasibility and stability, effectively controlling major defects and ensuring consistent product quality and production efficiency.