In the process of injection molding, it is often difficult to solve the shrinkage of a certain part of the product. In this case, only the back pressure can be used to adjust the back pressure parameters appropriately.
The reason for using the back pressure is that when the screw rotates, the plasticized plastic is pushed forward by the screw, passes through the stop valve and reaches the front of the screw, and the melt generates a reaction force due to the forward advancement of the melt. Acting on the screw and the stop valve, the screw is retracted, so that more molten material is pushed forward. At this time, if the back pressure is adjusted, the cylinder has a certain pressure from the back to the front on the screw, providing The resistance of the screw retreating, the greater the back pressure, the longer the screw reset time, the pressure generated by the front end of the screw must be greater than the back pressure to allow the screw to retreat. It must be pointed out that not all injection molding production must use back pressure, but if back pressure is used, the plastic can be fully melted and mixed evenly.
There are more advantages to using back pressure in the injection molding process: First, it is beneficial to the discharge of volatile gases in the melt. Second, make the additive and the melt mix more evenly. Third, make plastic plasticization more uniform and so on.
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