Four factors of the vertical injection molding machine not forming

Posted by sere on November 12th, 2020

In the plastics processing industry, the vertical injection molding machine is the most used injection molding equipment. The output of vertical injection products accounts for more than 30% of the total plastic products. It is characterized by easy production automation, short production cycle, and adaptability. Strong, high-end production power. However, the vertical injection molding machine has problems when it is working, which is generally a process problem. So what are the influencing factors of the vertical injection molding machine not forming?

(1) The injection pressure is too low, the injection time is short, and the plunger or screw returns too early. Molten plastic has a higher viscosity and poor mobility at lower operating temperatures, and injections should be made at higher pressure and speed. For example, when making ABS colorful parts, the high temperature resistance of the colorant limits the heating temperature of the barrel, which must be compensated with higher injection pressure and extended injection time than usual.

(2) The injection speed is slow. The injection speed has a very prominent meaning for some products with messy shapes, large thickness changes, and long processes, as well as plastics with higher viscosity such as resistant ABS. When the high pressure can not be used to fill the finished product, high-speed injection should be considered to solve the shortcomings of filling dissatisfaction.

(3) Feeding materials are not properly adjusted, lack of materials or excessive materials. Feeding metering is forbidden or the feeding control system is not operating normally, the vertical injection molding machine or mold or operating conditions are limited to cause the injection cycle to be abnormal, the pre-plastic back pressure is too small, or the density of the material in the barrel is small.Plastic materials with a lot of open space and crystallized 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 material temperature is high, the volume should be increased.When there is too much material at the end of the barrel, the screw will consume a lot of injection pressure to compress and push the excess stock in the barrel during injection, which greatly reduces the useful injection pressure of the plastic entering the mold cavity. Make the finished product difficult to overflow.

(4) The material temperature is too low. The temperature of the front end of the barrel of the vertical injection molding machine is low, and the viscosity of the molten material entering the cavity rises too early to the point where it is difficult to move due to the cooling effect of the mold, which hinders the filling of the far end; the temperature of the rear section of the barrel is low , The plastic with high viscosity is difficult to move forward, which hinders the forward movement of the screw. The result is that the pressure displayed by the pressure gauge is satisfied, but in fact the melt enters the cavity at low pressure and low speed; the low temperature of the nozzle may be caused by the long-term relationship between the nozzle and the fixed feeding. Cold mold touch loses heat. Perhaps the nozzle heating ring lacks heat or touches poorly, resulting in low material temperature, which may block the mold’s feeding channel; if the mold does not have a cold slug well, use a self-locking nozzle and select a post-feeding program. It 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 speed up the nozzle heating.

The vertical injection molding machine uses the thrust of the screw (or plunger) to plasticize the plastic in the molten state (that is, the viscous flow state). The process of injecting into the closed mold cavity and obtaining the product after curing and shaping.