problem:
Injection molding products are incomplete, how to overcome in the process?
answer:
Slow injection speed
The injection speed has great significance for some products with complex shapes, large thickness and long process, long process, and plastics with high viscosity such as toughness ABS. When high pressure is not enough to fill the product, high-speed injection should be considered to overcome the problem of dissatisfaction.
Improper feed adjustment, lack of material or more material
Inaccurate metering or improper operation of the feed control system, injection molding machine or mold or operating conditions, resulting in abnormal injection cycle, small pre-plastic back pressure or small density of material in the barrel may cause material shortage, for large particles, Plastics with large voids and crystallographic specific changes such as polyethylene, polypropylene, nylon, etc., and plastics with higher viscosity, such as ABS, should be adjusted to a higher amount. When the temperature is high, the amount of material should be adjusted.
When there is too much material stored at the end of the barrel, the screw consumes an extra injection pressure to compress and push the excess material in the barrel during injection, which greatly reduces the effective injection pressure of the plastic entering the cavity. The product is difficult to fill.
Material temperature is too low
The temperature at the front end of the barrel is low, and the melt entering the cavity causes the viscosity to rise prematurely to the point where it is difficult to flow due to the cooling effect of the mold, which hinders the filling of the distal end; the plastic in the rear part of the barrel has a low temperature and a high viscosity. Difficulty in flow hinders the advancement of the screw, resulting in a pressure that appears to be sufficient for the pressure gauge to actually enter 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, and the heat is insufficient, or the nozzle heating coil is insufficiently heated or the contact temperature is low, which may block the feeding passage of the mold; if the mold does not have cold material Wells, with self-locking nozzles, using the post-feeding procedure, the nozzles can maintain the necessary temperature; when the nozzles are too cold, the nozzles can be heated externally to accelerate the nozzle temperature.
Injection pressure is too low, injection time is short, plunger or screw is returned too early
Molten plastics have higher viscosity at lower operating temperatures and poor fluidity and should be injected at higher pressures and speeds. For example, in the case of ABS color parts, the high temperature resistance of the colorant limits the heating temperature of the barrel, which is compensated by a higher injection pressure than usual and an extended injection time.
