Technology

　　(1) Improper feed adjustment, lack of material or excessive material. Improper feeding measurement or abnormal operation of the feeding control system, abnormal injection cycle caused by the limitation of injection molding machine or mold or operation conditions, small back pressure of pre molding or small particle density in the barrel may result in material shortage. For particles with large particles and many voids, plastics with large specific volume change of crystallinity, such as polyethylene, polypropylene, nylon, and plastics with large viscosity, such as ABS, should be adjusted higher When the material temperature is too high, the material quantity shall be increased.

　　When there is too much material stored at the end of the barrel, the screw consumes extra injection pressure to compress and push the excessive material stored in the barrel during injection, which greatly reduces the effective injection pressure of the plastic entering the mould cavity and makes the product difficult to be filled.

　　(2) Injection pressure is too low, injection time is short, plunger or screw return too early. The melt plastic has high viscosity and poor fluidity at low temperature, so it should be injected at high pressure and speed. For example, when making ABS color parts, the high temperature resistance of colorant limits the heating temperature of the barrel, which should be compensated by higher injection pressure and longer injection time than usual.

　　(3) Injection speed is slow. The injection speed is very significant for some products with complex shape, large thickness change, long process, and plastics with high viscosity, such as ABS. When using high-pressure products can not be filled, high-speed injection should be considered to overcome the problem of insufficient injection.

　　(4) The material temperature is too low. The temperature of the front end of the barrel is low, and the melt entering the mould cavity rises to the point where it is difficult to flow due to the cooling effect of the mould, which hinders the filling of the mould at the far end; the plastic with low temperature and high viscosity in the rear part of the barrel flows difficultly, which hinders the forward movement of the screw, which results in that the pressure indicated by the pressure gauge is enough, but in fact, the melt enters the mould cavity at low pressure and low speed; If the temperature of the nozzle is low, the heat loss may be caused by the contact between the nozzle and the cold mold for a long time during the fixed feeding, or the low temperature of the material may be caused by the insufficient heat supply or poor contact of the nozzle heating ring, which may block the feeding channel of the mold; if the mold does not have a cold charging well, use the self-locking nozzle, and use the post feeding procedure, the nozzle can maintain the necessary temperature better; When the nozzle is too cold when the machine is just started, sometimes the flame gun can be used for external heating to accelerate the temperature rise of the nozzle.

　　Raw materials

　　The fluidity of plastics is poor. Recycled chips are often used in plastic factories, and recycled chips often reflect the tendency of viscosity increase. It is pointed out that the increase of the unit volume density of the molecular broken chain generated by oxidative cracking increases the viscosity of the flow in the barrel and the cavity, and the regeneration of the crushed material promotes the generation of more gaseous substances, increases the injection pressure loss and makes it difficult to fill the mold. In order to improve the fluidity of plastics, the addition of external lubricants such as stearic acid or its salts should be considered, and silicone oil (viscosity 300-150000px2 / s) is the best choice. The addition of lubricant not only improves the fluidity of plastics, but also improves the stability and reduces the gas resistance of gaseous substances.

　　Overflow (flying edge)

　　Overflow, also known as flash, overflow and drape front, mostly occurs at the scoring and closing position of the mold, such as the parting surface of the mold, the sliding part of the slider, the gap of the insert, the hole of the top bar, etc. If the overflow is not solved in time, it will be further expanded, so that the stamping die will form local collapse, causing permanent damage. The overflow of the gap of the insert and the hole of the ejector pin will also make the product stuck on the mold and affect the demoulding.