(1) Improper feeding adjustment, lack of material or excess material.

Inaccurate feeding measurement or abnormal operation of the feeding control system, abnormal injection cycle due to limitations of the injection molding machine or mold or operating conditions, low pre-molding back pressure or low density of the particles in the barrel may cause material shortage. For large particles, For granular materials with many voids, plastics with large crystalline specific volume changes such as polyethylene, polypropylene, nylon, etc., and plastics with high viscosity such as ABS, the material amount should be increased. When the material temperature is high, the material amount should be increased.

When there is too much material stored at the end of the barrel, the screw will consume 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 mold cavity. The product is difficult to fill.

(2) 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 low operating temperatures, so it should be injected at higher pressure and speed. For example, when making ABS colored parts, the high temperature intolerance of the colorant limits the heating temperature of the barrel, which requires a higher injection pressure and longer injection time than usual to compensate.

(3) The injection speed is slow.

Injection speed is of great significance for some products with complex shapes, large thickness changes, long processes, and plastics with high viscosity such as toughened ABS. When the product cannot be fully filled using high pressure, high-speed injection should be considered to overcome the problem of insufficient filling.

(4) The material temperature is too low.

The temperature of the front end of the barrel is low, and the viscosity of the molten material entering the cavity rises prematurely to the point where it is difficult to flow due to the cooling effect of the mold, hindering the filling of the remote end; the temperature of the rear section of the barrel is low, and the plastic with high viscosity The flow is difficult, which hinders the forward movement of the screw. As a result, it seems that the pressure displayed by the pressure gauge is sufficient, but in fact the molten material enters the mold cavity at low pressure and low speed.

If the nozzle temperature is low, it may be that the nozzle has been in contact with the cold mold for a long time during fixed feeding and has lost heat, or the nozzle heating ring has insufficient heating or poor contact, causing the material temperature to be low, which may block the feeding channel of the mold; if the mold does not have cold material Well, use a self-locking nozzle and adopt a post-feeding procedure, so that the nozzle can maintain the necessary temperature; when the nozzle is too cold when it is first started, sometimes a flame gun can be used for external heating to accelerate the nozzle temperature rise.