Do you know how backpressure is used in injection molding?
Backpressure is the pressure applied to the molten material during the screw retraction (plasticizing) stage of the injection molding process. It is the pressure built up in the barrel and is achieved by different hydraulic setpoints depending on the intensification ratio.
The main functions of backpressure are as follows:
1. Improve the density and uniformity of the molten material. Backpressure can compress the molt material in the barrel, thereby improving its density and uniformity. This can improve the mechanical properties and appearance of the plastic parts.
2. Reduces air bubbles in the melt material. Backpressure can help to remove air bubbles from the melt material, thereby reducing voids and bubbles in the product.
3. Improves the melt material flowability. Backpressure can cause the melt material to generate more flowability under shear action, thereby improving the product quality.
4. controls the size and weight of the product. Backpressure can control the metering accuracy of the molten material.
The amount of backpressure should be adjusted according to the properties of the plastic, the shape and the size of the product, and the type of injection molding machine. In general, higher backpressure should be used for plastics with poor flowability; lower backpressure should be used for plastics with good flowability
