Injection-moulded parts refer to various injection molded products produced by injection molding machines. They are collectively referred to as injection molded parts, including various packaging, parts and so on. They are mainly made of materials such as polyethene or polypropylene and added with a variety of organic solvents.
1. Improper selection of the equipment
When selecting equipment, the maximum injection volume of the injection molding machine must be greater than the total weight of the plastic injection molding parts and gate, and the total injection weight cannot exceed 85% of the plasticization volume of the injection molding machine.
2. Insufficient supply
At present, the commonly used method to control the charging is the fixed-volume charging method. Observe whether the amount of roll material is uniform with the particle size of the raw material, and whether there is a "bridging" phenomenon at the bottom of the feeding port. If the temperature at the feeding port is too high, it will also cause poor blanking. In this regard, the feeding port should be dredged and cooled.
3. Poor material fluidity
When the fluidity of the raw material is poor, the structural parameters of the injection molding molds are the main reason that affects the short shot. Therefore, the stagnation defects of the electronic plastic parts injection mould gating system should be improved, for example, setting the runner position reasonably, expanding the size of the pouring gate, runner and injection port, and use larger nozzles. Check whether the amount of recycled materials in the raw materials is excessive. If so, reduce the amount appropriately.
4. Excess lubricant
If the amount of lubricant in the raw material formula is too much, and the wear clearance between the non-return ring of the injection screw and the barrel is large, the molten material will flow back into the barrel seriously, which will cause insufficient feeding and short shot. In this regard, the amount of lubricant should be reduced and the gap between the barrel, the injection screw and the non-return ring should be adjusted, repairing the equipment.
5. Cold material impurities block the feeding channel
When the impurities in the melting block the nozzle or the cold material block the pouring gate and the runner, fold down the nozzle to clean it or expand the cold material cavity and the runner section of the mold.
6. The design of the pouring system is unreasonable
When a mold has multiple cavities, the appearance defects of the injection molding automotive parts are often caused by the unreasonable balance design of the pouring gate and the runner. When designing the gating system, pay attention to the balance of the pouring gate. The weight of the plastic parts in each cavity should be in direct proportion to the size of the pouring gate, so that each cavity can be filled at the same time. The location of the pouring gate should be selected at the thick part of the wall. Or adopt the balanced shunting runner layout design scheme. If the pouring gate or runner is small, thin, and long, the pressure of the melt will lose too much along the way during the flowing process, so the flow will be blocked and poor filling will easily occur. In this regard, the cross-section of the runner and the pouring gate area should be expanded, and multi-point feeding can be adopted if necessary.
7. Poor venting of injection molding mold
When a large amount of residual gas in the mold is squeezed by the material flow due to poor venting, generating a high pressure greater than the injection pressure, it will prevent the melt from filling the cavity and thus cause a short shot. It should be checked whether the cold material cavity is set or whether its position is correct. In addition, in terms of the process operation of the mold system, the poor venting can be improved by assistant measures like increasing the mold temperature, slowing down the injection speed, reducing the flow assistance of the gating system, reducing the clamping force and increasing the mold gap.