Relationship between clamping force and material
Relationship between clamping force and material
The applied pressure should be higher than the full cavity pressure. In the injection process, the mold control pressure rises sharply, and finally reaches a peak, which is usually called the injection pressure. The injection pressure is obviously higher than the full cavity pressure.
The function of pressure maintaining pressure: after the cavity is filled with plastic until the gate is completely cooled, the plastic in the cavity still needs a high pressure support, namely pressure maintaining. Its specific function is:Replenish the amount of material close to the gate, and prevent the unhardened plastic in the mold cavity from flowing back to the gate material source under the residual pressure before the gate condensation is closed.
Prevent shrinkage of parts and reduce vacuum bubble.
Reduce the phenomenon of die bursting or bending deformation due to excessive injection pressure. Therefore, the holding pressure is usually 50% - 60% of the injection pressure. If the holding pressure or time is too long and too large, it is possible to squeeze the cold material on the gate and flow channel into the workpiece, so that the bright spot of cold material is added near the gate, and the cycle is extended without any benefit.
Selection of injection pressure:
According to the shape of the parts, thickness selection;
Select different plastic materials.
Under the permission of production conditions and product quality standards, it is suggested to adopt the process conditions of low temperature and low pressure.
Back pressure regulation:
The back pressure represents the pressure of plastic plasticizing process. Sometimes called plasticizing pressure.
The mixing effect of color is affected by back pressure. The back pressure is increased and the mixing effect is strengthened.
Back pressure helps to eliminate all kinds of gases in plastic parts, reducing craze and bubble phenomenon.
Proper back pressure can avoid local material stagnation in the barrel, so the back pressure is often increased when cleaning the barrel.
