Injection molded products fill insufficient, how to improve the process?
(1) improper feeding adjustment, material shortage or multiple materials.
Measurement is allowed to or control of feeding system operation is not normal, and the limit of the injection mould or operating conditions lead to abnormal injection cycle, plastic small back pressure or machine barrel inside small grain density is likely to be due to lack of material, the number of large particles, gap of aggregate and the volume change of the crystalline is big plastic such as polyethylene, polypropylene, nylon and other plastic such as ABS and high viscosity should be adjusted higher feed rate, feed temperature on the high side should be adjustable for big shoes.
When too much material is stored at the end of the cylinder, the screw will consume extra injection pressure to compress and push the excess stock in the cylinder, which greatly reduces the effective injection pressure of the plastics entering the mold cavity and makes the products difficult to fill.
(2) the injection pressure is too low, the injection time is short, and the plunger or screw is returned too early.
The melt plastics have high viscosity and poor fluidity at low operating temperature and should be injected at high pressure and speed.For example, when making ABS color parts, the impregnation of colorants limits the heating temperature of the cylinder, which is compensated by higher injection pressure and longer injection time than usual.
(3) slow infusion speed.
Injection rate is of great significance for some products with complex shapes, large thickness changes, long process, and plastic with high viscosity, such as toughening ABS.When the product cannot be filled with high pressure, the problem of dissatisfactory injection can be overcome by using high speed injection.
(4) material temperature is too low.
The temperature at the front end of the cylinder is low, and the melt entering the mold cavity causes the viscosity to rise to the point of difficulty to flow prematurely due to the cooling action of the mold, which hinders the filling of the far end of the mold.The temperature of the rear section of the cylinder is low and the plastic with high viscosity is difficult to flow, which impedes the forward movement of the screw rod. As a result, it seems that the pressure shown by the pressure gauge is enough, but actually the molten material enters the mold cavity at low pressure and low speed.
If the temperature of the nozzle is low, it may be that the nozzle has lost heat due to the long time of contact with the cold mold during the fixed feeding.If the mold does not take the cold feed well, use the self-locking nozzle and adopt the post-feed procedure, the nozzle can maintain the necessary temperature;When the nozzle is too cold at first startup, sometimes the nozzle can be heated externally with a flame gun to accelerate the heating process.