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How to overcome the incomplete injection molding products?
Improper feed adjustment, lack of material or excessive material
Inaccurate feeding measurement or abnormal feeding control system operation, abnormal injection cycle caused by injection molding machine or mold or operating conditions, low pre-plastic back pressure, or low particle density in the barrel may cause material shortage. For large particles, Pellets with many voids and plastics with large crystalline specific volume changes, such as polyethylene, polypropylene, nylon, etc., as well as plastics with higher viscosity, such as ABS, should be adjusted to a higher volume. When the temperature of the material is high, the volume should be adjusted.
When there is too much material at the end of the barrel, the screw will consume extra injection pressure to compress and push the excess stock in the barrel during injection, which greatly reduces the effective injection pressure of the plastic entering the mold cavity. The product is difficult to fill.
The injection pressure is too low, the injection time is short, and the plunger or screw returns too early
Molten plastic has higher viscosity and poor fluidity at lower working temperature, so it should be injected at higher pressure and speed. For example, in the production of ABS color parts, the high temperature resistance of the colorant limits the heating temperature of the barrel, which has to be compensated by higher injection pressure and longer injection time than usual.
Slow injection speed
The injection speed is of great significance for some products with complex shapes, large thickness changes, and long processes, as well as plastics with high viscosity, such as toughened ABS. When the product cannot be filled with high pressure, high-speed injection should be considered to overcome the problem of dissatisfaction.
Material temperature is too low
The temperature at the front end of the barrel is low, and the viscosity of the molten material entering the cavity rises to the point where it is difficult to flow prematurely due to the cooling effect of the mold, which hinders the filling of the far end; the rear section of the barrel is low temperature and high viscosity plastic Difficult flow hinders the advancement of the screw. As a result, it seems that the pressure indicated by the pressure gauge is sufficient, but the melt actually enters the cavity at low pressure and low speed.
If the nozzle temperature is low, it may be that the nozzle is in contact with the cold mold for a long time during the fixed feeding and loses heat, or the nozzle heating ring is insufficiently heated or has poor contact, resulting in low material temperature, which may block the mold’s feeding channel; if the mold does not have cold material Well, with self-locking nozzles and post-feeding procedures, the nozzles can maintain the necessary temperature; the nozzle is too cold when it is just turned on, and sometimes a flame gun can be used for external heating to accelerate the temperature of the nozzle.