By Cap mould following proper part design, sink marks c […]
By Cap mould following proper part design, sink marks can be minimized. If there are any ribs or structural features behind the shaped surface, the dents will not be eliminated. But with proper part design, they can be minimized to an invisible degree. Shorten the cooling time of the injection mold. Higher mold temperature. The product thickness is greater. Higher resin melt temperature during injection. More plasticizer in the resin. The injection speed is slower. Smaller packaging holding pressure and volume. Extend the cooling time of the injection mold.
Lower the mold temperature. The product wall is thinner. Reduce the resin melt temperature during the injection process. Higher injection speed. Larger packaging/holding pressure and volume. Fillers such as talc, glass beads or glass fibers fibers will produce more anisotropic shrinkage. Injection speed, filling volume and mold temperature will significantly affect the molding stress or leave voids and dent marks. Molding stress affects warpage, solvent sensitivity, dimensional stability and impact resistance; therefore, these tertiary effects need to be considered. Warpage is usually caused by compression stress.
The problem of warpage is related to semi-crystalline materials. HDPE is a semi-crystalline polymer that has different shrinkage rates along the flow direction and the entire flow direction, resulting in warpage. It is difficult to eliminate this problem only by optimizing the processing parameters. If multiple gates can be used, it may help multi-directional flow, thereby reducing warpage. The two most affected areas are the temperature of the injection mold and the location and type of the gate. It is difficult to give specific suggestions without knowing the configuration or process, but to consider the parts on the molecular scale. Imagine that the surface of the part is interconnected crystals, and the cooling starts from the coldest surface of the injection mold.
The surface will be multiple points and spread into a circle in less than a second. You want the surface as cold as possible and reusable, and you want the runners to fill the mold as evenly as possible. The flow front is more uniform than the part configuration from side to side, and the uniform temperature of the plastic injection mold surface temperature will minimize warpage. There are some design techniques that can minimize warpage, but you may exceed this. As for the gate type, it should be as large as possible so as not to increase the shear force. Also monitor the melting temperature of the nozzle and look for the lowest temperature to ensure that the mold is completely filled.