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Key Processes of PC Injection Molding Dies

2025-12-29 10:45:31 Injection Molding
PC (Polycarbonate) is widely applied in electronics, automotive components, and medical devices due to its outstanding impact resistance, heat resistance, and optical transparency. The technological process of PC injection molding dies is a critical factor that directly determines both product quality and production efficiency, with its core focusing on four key links: mold adaptation, raw material optimization, molding process control, and post-processing guarantee. Compared with ordinary plastics, PC’s high melt viscosity and strong hygroscopicity impose stricter requirements on mold design and process parameter control.

1. Mold Design and Manufacturing

1.1 Mold Structure Design

The mold structure must be designed to match PC’s melt flow characteristics, with special attention to the gating and cooling systems. Conformal cooling channels, in particular, can significantly improve cooling efficiency by more than 30% compared with traditional straight channels, effectively reducing product warpage. Meanwhile, a reasonable exhaust structure with a gap of 0.01-0.02mm is essential to prevent defects such as gas marks and burn marks during molding.

1.2 Mold Material and ProcessingCavities and cores are typically made of wear-resistant and corrosion-resistant alloy steel, with mirror steel selected for molds producing transparent PC products. After heat treatment, the mold steel hardness should reach HRC 50-55 to ensure sufficient durability for long-term production. Precision machining technologies such as CNC milling and wire cutting are adopted to guarantee the mold’s dimensional accuracy and surface finish.

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1.3 Simulation and Trial OptimizationCAD/CAE integrated simulation technology is used in the mold design stage to simulate melt filling, pressure holding, and cooling processes, which can reduce the number of trial molds by more than 60% and greatly shorten the mold development cycle. After mold manufacturing, trial molding is carried out, and parameters are adjusted or mold structures optimized based on trial results until product quality meets the required standards.

2. Core Injection Molding Process

2.1 Raw Material Preprocessing

PC has strong hygroscopicity, with a moisture absorption rate of 0.3%-0.5% in a standard environment. Excessive moisture can cause bubbles, silver streaks, and degradation during molding, so thorough drying is necessary. The drying process is typically carried out at 120-130℃ for 4-6 hours, reducing the material’s moisture content to below 0.02%.

2.2 Process Parameter SettingThe barrel temperature is controlled in sections within the range of 260-310℃, with higher temperatures for HDPE and slightly lower for LDPE. The injection pressure ranges from 80-145MPa, adjusted according to product structure complexity. The holding pressure is 50%-70% of the injection pressure, and the mold temperature is maintained at 80-120℃ to optimize melt flow and reduce internal stress.

injection mould

2.3 Molding Process ControlKey parameters such as barrel temperature, injection pressure, and mold temperature are monitored in real time during injection molding, with temperature fluctuations controlled within ±5℃. Stable clamping force is ensured to avoid flash or incomplete filling, and a two-stage ejection structure is adopted for thin-walled or irregular products to prevent damage during demolding.

3. Product Post-Processing and Quality Inspection

3.1 Post-Processing

Annealing treatment is required for PC products to eliminate internal stress, with the annealing temperature controlled at 100-120℃ and holding time adjusted according to product thickness. After annealing, gates, flashes, and burrs are removed, and mirror polishing is performed on transparent products to achieve a light transmittance of no less than 88%.

3.2 Quality InspectionAppearance inspection focuses on defects such as bubbles, scratches, and weld lines. Dimensional inspection uses professional tools to verify key size tolerances, and performance inspection samples test indicators such as impact strength to ensure products meet application requirements.

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