Injection pressure of injection molding machine
It is generally divided into two stages. The first stage is the stage of injecting melt material into the mold at a high speed. The pressure at this time is called the 1st injection pressure, which is the so-called injection pressure. The second stage is the pressure applied after filling the mold,which is called 2nd injection pressure or holding pressure.
If the injection pressure is too low, the filling amount will be insufficient. If the pressure is too high, the density of the part will increase and the shrinkage rate will decrease. However, if too high, the product will have a flash or a large residual stress. It also makes it difficult to demold the part.
Therefore, when debugging the product, it should start from the low pressure and gradually increase to determine the appropriate injection pressure.
The secondary injection pressure (holding pressure) is the pressure acting on the material after the material is filled into the cavity to cool and solidify. The whole time of the pressure holding pressure is called the holding time. Its function is on the basis of preventing the flash occur and over filling, machine can fill the portion which was reduced in volume due to shrinkage during cooling and solidification from then ozzle with the melt material.
in order to prevent the shrinkage (shrinkage) caused by the shrinkage of the workpiece. Generally, holding pressure settings are lower than injection pressure.