The working principle of the charger shell injection mold is as follows:
The mold is mounted onto the SZ-250/1250 injection molding machine. The fixed mold part is secured to the fixed platen, while the movable mold part is attached to the movable platen of the injection machine. When the mold is closed, ABS melt is injected into the cavity through the sprue system by the machine nozzle. After holding pressure and cooling, the plastic part solidifies and takes shape.
During mold opening, the movable part of the mold moves with the machine’s movable platen. At Parting Line I, the sprue plate separates from the fixed platen due to spring force, and the hook pin breaks off the sprue, detaching it from the plastic part. The runner system residue is gradually ejected as the middle plate moves away from the fixed platen. Once Parting Line I opens by 50mm, the distance-based splitting mechanism activates, pushing the sprue plate backward, ejecting the residue from the main sprue. When the sprue plate moves 10mm from the panel, the residue fully detaches and falls off automatically due to gravity.
Simultaneously, Parting Line II opens, causing the molded part to separate from the core. After the mold opens to a sufficient distance, the movable mold stops. The ejection device pushes the ejector rod assembly forward through the ejector holes, moving the ejector plate and pushing out the plastic part, which falls off automatically due to gravity.
When closing the mold, the injection machine’s thrust forces the parting lines to close, resetting the ejector plate and rod. Once the mold fully closes, a complete cycle is finished, and the process repeats.
During mold trials, defects may appear on the plastic parts, requiring analysis and troubleshooting. Table 1 lists common defects and their causes for thermoplastic products. If any defects arise, analyze the primary causes based on molding conditions, equipment, mold design, and part shape. Then adjust processing parameters or modify the mold as needed to resolve the issues.
| Defect | Cause |
|---|---|
| Insufficient Filling | Low barrel/nozzle/mold temperature, insufficient feed, low injection pressure, slow injection speed, undersized runners/gates, inadequate gate placement, poor cavity venting, short injection time, system blockage, poor plastic flowability. |
| Flashing | Excessive barrel/nozzle/mold temperature, high injection pressure, low clamping force, poor mold sealing, foreign objects in the mold, or warped mold plates. |
| Black Spots/Streaks | Overheated material, decomposed plastic, poorly fitted barrel/nozzle, poor mold venting, uneven dye distribution, or dark impurities in material. |
| Delamination | Contaminated raw material, mixed plastic grades, excess lubricants, uneven plasticizing, severe material contamination, small gates causing high friction. |
| Weld Lines | Low material/mold temperature, excessive mold release agents, low injection pressure, slow injection speed, inadequate feeding, poor mold venting. |
| Surface Cracks | Cold mold, long cooling time, mismatched shrinkage rates between plastic and metal inserts, misaligned ejector systems, inadequate draft angles causing ejection difficulties. |
| Surface Ripples | Low material temperature, high viscosity, low injection pressure, low mold temperature, slow injection speed, small gates. |
| Warpage/Deformation | Short cooling time, insufficient ejection force, high mold temperature, excessive internal pressure, uneven cooling, uneven wall thickness. |
| Unstable Dimensions | Unstable machine circuitry or hydraulic system, inconsistent molding cycle, variations in temperature, time, or pressure, irregular plastic granule sizes. |
| Mold Sticking | Poor ejector system design, insufficient draft angle in the cavity, improper mold temperature, residual material in mold seams, incorrect molding cycle duration. |
