Lack of glue is one of the most common defects in injection molding, also known as "short shot". The concrete performance is: the product is not complete, mostly appears in the farthest part from the gate.
To improve this defect, the following parameters can be increased: melt position, barrel temperature, sol speed, back pressure, injection pressure, injection speed, injection time, pressure maintaining pressure, pressure maintaining time and mold temperature. This includes almost all injection parameters, which are described as follows:
Melt position: the melt measurement is not enough. It can be judged by observing the forward and end points of the screw. If it reaches the 0 position, the measurement should be increased, that is, the storage position.
Barrel temperature: the higher the material temperature, the smaller the viscosity of the material and the smoother the filling. It can also prevent the insufficient filling caused by the nozzle cold material blocking the thinner part.
Sol speed: material shear strength, can increase material temperature.
Back pressure: it can also enhance the shearing effect and material temperature. It can also compact the melt and increase the filling amount.
Injection pressure: the pressure is too small, the injection length is increasing, the resistance is also increasing, the injection pressure can not overcome the resistance to press the material into the cavity.
Injection speed: increase injection speed can reduce the increase of melt viscosity and the loss of injection pressure caused by cooling in the filling process. It has the same effect as increasing material temperature and mould temperature.
Injection time: the setting of injection time or injection pressure maintaining switch position should be reasonable and not too early. When the injection weight reaches 95% of the product weight, the pressure can be maintained. In the actual debugging, the injection position can be used as the starting point of pressure maintaining when the product is a little short of glue or shrinks.
Pressure maintaining pressure: the pressure maintaining pressure is insufficient, so the final filling cannot be carried out. Set the injection pressure above 50%, or even more than the injection pressure, provided that the transfer position is set correctly.
Holding time: the same as holding pressure.
Mold temperature: mold temperature is very important. The fluidity of some materials is greatly affected by temperature. Increasing mold temperature is the key to ensure smooth filling.
Of course, there are some "miscellaneous diseases" that need to be dealt with in addition, such as:
Gas accumulation: the gas in a certain part of the mold cavity cannot be discharged smoothly to prevent the filling of the melt. It can be solved by reducing the clamping force, cleaning the mold, or increasing the exhaust.
Leakage: in the production process, there is a sudden lack of glue. First, check whether the nozzle leaks. Readjust the pedestal, increase the forward pressure of pedestal (observe whether the pressure gauge of the system is consistent with the setting, prevent the pedestal oil seal from damaging and causing insufficient pressure), and increase the thickness of paper pad, etc.
There are residual foam or broken products in the mould: just clean the mould.
