Lack of Material 1. Meaning: The molten material is not filled after entering the mould cavity, resulting in a shortage of plastic parts.
2. Causes and troubleshooting methods:
① Improper equipment selection: When selecting equipment, the melting amount of the machine must be greater than the melting amount of the product, and the weight of the injection moulded part can only account for 85% of the total melt amount of the machine.
② Insufficient material supply: If there is a "bridging" phenomenon at the feeding port, the screw injection moulding stroke can be appropriately increased to increase the material supply amount.
③. Poor fluidity of raw materials: Improve the stagnation defect of the mould pouring system, reasonably set the pouring position, expand the size of the gate, runner and injection port, use a larger nozzle, and appropriately increase the temperature of the raw material.
④. The design of the gating system is unreasonable: When designing the gating system, attention should be paid to the balance of the gate. The weight of the plastic parts in each cavity should be proportional to the size of the gate. To ensure that each cavity can be filled at the same time, the position of the gate should be selected to be thicker. For the wall part, the design plan of a balanced arrangement of sprues can also be adopted.
⑤. Poor mould exhaust: Check whether there is a cold material cavity or whether the position is correct. For moulds with deep mould cavities, exhaust grooves and exhaust holes should be added to the parts that are underfilled. They can be opened on the mold closing surface. A vent groove with a depth of 0.02-0.04mm and a width of 5-11mm should be set at the final filling point of the cavity. In addition, in terms of process operation, the resistance of the gating system can be reduced by increasing the mold temperature, reducing the injection speed, and, and reduce the mold clamping force.
⑥. The mold temperature is too low: The mold must be preheated to the temperature required by the process before starting the machine. If the mould temperature cannot rise, check whether the mold water channel design is reasonable.
⑦ Insufficient injection pressure: The
injection mould pressure is close to a proportional relationship with the length of the die. The injection pressure is too small, the mold filling length is short, and the cavity is not filled enough. In this regard,
injection molding can be improved by slowing down the forward speed of the injection material and appropriately extending the injection time.
