What are the details of the fiber reinforced PC plastic injection molding process?

1. Pre - injection Molding Preparation

• Raw Material Selection and Treatment

• Selection Basis: Product performance needs guide raw material choice. Higher - load products require PC with suitable fiber content, length, and diameter. High - appearance - quality products demand pure raw materials and proper additives. Reputable suppliers ensure raw material stability.

• Drying: PC is hygroscopic and prone to hydrolysis. Before molding, dry it in a hot - air circulation box at 100 - 120 °C for at least 4 hours (6 - 8 hours for large particles or high - fiber - content materials), reducing moisture to < 0.02%. Use low - humidity air and avoid over - drying.

• Mold Preparation

• Structure Inspection: Check the mold parting surface for smoothness and tight fit to prevent flash. Ensure smooth movement of complex - structure parts like sliders and inclined tops. Verify that the gate and runner system suit fiber - reinforced PC, with the gate avoiding key appearance and stress - concentration areas.

• Cleaning and Maintenance: Apply release agent evenly on the mold cavity with a clean cloth. Remove oil and impurities. For long - unused molds, check rust prevention; if rusty, polish and re - treat.



• Injection Molding Machine Debugging

• Selection and Parameter Setting: Choose an injection molding machine based on product size, weight, and complexity. Set parameters like injection stroke, mold opening/closing speed, and ejection speed. Calculate the injection stroke accurately for fiber - reinforced PC.

• Barrel Cleaning: Thoroughly clean the barrel if other plastics were previously processed. Use compatible cleaning materials or plastics, increasing barrel temperature gradually.

2. Process Parameter Control during Injection Molding

• Temperature Control

• Barrel Temperature Partition: Divide the barrel into feed, compression, and metering sections. Set feed - section temperature at 260 - 280 °C, compression - section at 280 - 300 °C, and metering - section at 300 - 320 °C. Adjust for raw - material batch and fiber - content differences.

• Nozzle Temperature: Set it slightly lower than the metering - section temperature, at 290 - 310 °C. Ensure nozzle insulation to prevent melt solidification or drooling.

• Pressure Control

• Injection Pressure Adjustment: Set injection pressure based on product wall thickness, shape complexity, and mold structure. 80 - 100 MPa for thick - walled products (> 3 mm), 100 - 150 MPa for thin - walled (< 2 mm) or complex - shaped products. Fine - tune during injection.

• Holding Pressure Setting: Holding pressure is 50% - 80% of injection pressure. Increase for large or thick - wall products. Determine holding time according to product thickness (1 - 2 seconds per 1 mm increase in wall thickness).

• Speed Control

• Injection Speed Curve: Control injection speed in multiple stages. Start with a low speed (10 - 30 mm/s), increase to 30 - 60 mm/s when 50% - 70% of the cavity is filled, and reduce to 10 - 20 mm/s near the end.

• Screw Speed Control: Keep screw speed at 40 - 60 r/min for fiber - reinforced PC to ensure good plasticization without breaking fibers.

3. Gate and Runner Design

• Gate Design

• Type Selection: Use pin - point gates for high - appearance - quality, small - size products (0.8 - 1.5 mm diameter). Side gates are suitable for flat or simple - shaped products (width 1 - 2 times wall thickness, depth 0.6 - 0.8 times wall thickness).

• Location Optimization: Set the gate in thicker - walled product parts, away from stress - sensitive and appearance - critical areas.

• Runner Design

• Main Runner Design: The main runner has a 2° - 4° taper, with the small - end diameter 0.5 - 1 mm larger than the nozzle diameter. Keep it short and ensure a smooth transition to the diverter.

• Diverter Design: Determine diverter diameter (4 - 8 mm, larger for large products or multi - cavity molds) and use round or trapezoidal sections. Ensure low surface roughness.

4. Cooling and Demoulding

• Cooling System Design and Control

• Cooling Channel Layout: Design cooling channels according to product shape and wall thickness. Keep a 10 - 20 mm distance from the mold - cavity surface, with a 6 - 12 mm channel diameter and appropriate spacing.

• Cooling Medium Temperature and Flow: Use water at 20 - 30 °C (10 - 20 °C for large/thick - wall products). Monitor and adjust cooling - medium flow with valves and sensors.

• Demoulding Process Control

• Demoulding Mechanism Design: Design suitable demoulding mechanisms (push - rod, push - plate, slider, etc.) based on product structure. For complex products, use special structures like inclined - top or secondary demoulding.

• Release Force Control: Ensure moderate demoulding force, considering product - mold friction and shrinkage. Use release agent and control demoulding speed, especially for thin - walled or easily - deformed products.

5. Product Post - processing

• Annealing Treatment

• Parameter Determination: Anneal at 120 - 130 °C (up to 140 °C for thick - wall products) for 1 - 2 hours per 1 mm of wall thickness. Heat slowly (10 - 20 °C/hour) in an air - circulation oven.

• Effect Evaluation: Evaluate annealing by observing product appearance and size changes. Use a polarizing stress meter to detect internal - stress reduction.

• Surface Treatment

• Grinding and Polishing: Remove gate marks and flash by grinding, then polish (mechanically, chemically, or electrolytically) to improve gloss.

• Coating and Plating: Coat to enhance appearance and protection. Pretreat the product surface. Electroplate to add metallic properties, controlling plating parameters.

6. Quality Control and Testing

• Appearance Quality Inspection

• Visual Inspection: Check for bubbles, silver lines, black spots, flash, and scratches. Observe color uniformity under proper lighting.

• Surface Roughness Detection: Use a roughness meter to ensure compliance, especially for high - gloss products.

• Dimensional Accuracy Detection

• Tool Selection and Method: Select appropriate measuring tools (calipers, micrometers, CMM) and measure according to specified points and methods.

• Deviation Cause Analysis: Analyze dimensional - deviation causes (mold design, injection parameters, raw - material shrinkage) and take corrective measures.

• Performance Testing

• Mechanical Property Test: Test tensile, bending, and impact strength according to standards. Check raw - material quality, fiber content, and injection parameters if performance is sub - standard.

• Thermal and Chemical Properties Testing: Test thermal deformation temperature, Vica softening point, and chemical resistance. Adjust raw - material formula or injection parameters if properties are insufficient.