How should injection molds prevent streaking defects from occurring
1. Improper selection of equipment: When selecting equipment, the amount of melted material of the machine must be greater than the amount of melted material of the product. The weight of the injection molded parts can only account for 85% of the total melting amount of the machine.
2. Insufficient feeding: Whether there is a phenomenon of "bridge" at the feeding port, the screw injection stroke can be appropriately increased to increase the feeding amount.
3. Poor fluidity of raw materials: Improve the stagnation defects of the mold casting system, reasonably set the pouring position, enlarge the gate, the size of the runner and the injection port, and adopt a larger nozzle to appropriately increase the temperature of the raw material.
4. The design of the pouring system is unreasonable: When designing the pouring system, pay attention to the balance of the gate. The weight of the plastic parts in each cavity should be proportional to the size of the gate. The cavity can be filled at the same time, and the gate position should be thick. For the wall part, it is also possible to adopt a design scheme in which the split runners are balanced.
5, mold exhaust failure: check whether there is a cold material cavity, or the position is correct, for the mold with deep cavity, the exhaust groove and vent hole should be added in the unfilled part, can be opened on the clamping surface A venting groove with a depth of 0.02-0.04 mm and a width of 5-11 mm, and the venting hole should be placed at the filling of the cavity. In addition, in terms of process operation, the mold temperature can be increased, the injection speed can be reduced, the casting system resistance can be reduced, and the mold clamping force can be reduced.
6. The mold temperature is too low: the mold must be preheated to the temperature required by the process before starting. If the mold temperature does not rise, it should be checked whether the mold water channel design is reasonable.
7. Insufficient injection pressure: the injection pressure and the length of the die are close to a proportional relationship. The injection pressure is too small, the filling length is short, and the cavity filling is not full. For this, the injection speed can be slowed down and the injection time can be appropriately extended to increase the injection molding. pressure.