The pressure control during injection molding

- Feb 16, 2019-

     1.Manner plasticizing pressure :(back pressure) when using screw injection machine, the screw top melt in screw rotation back pressure is called plasticizing pressure, also known as back pressure.This pressure can be adjusted by means of an overflow valve in the hydraulic system.In injection, the size of the plasticizing pressure is depending upon the design of the screw, the product quality requirements, and the type of plastic and needs to change, if the situation and the screw rotation speed is constant, increase plasticizing pressure will strengthen shearing action, which will raise the temperature of the melt, but will reduce the plasticizing efficiency, increase the current and leakage flow, increase the driving power.

In addition, increasing the plasticizing pressure can often make the melt temperature uniform, color mixture uniform and exhaust the melt gas.In general operation, the decision of plasticizing pressure should be below the premise that assures product quality is good the lower the better, its specific numerical value is the breed with the plastic that USES and differ, but exceed 20 kilograms/square centimeter rarely normally.

2. Infusion pressure: in the current production, almost all the injection pressure of the injection machine is made up of the plunger or screw top on the plastic pressure (by oil pressure conversion) prevail.The injection pressure plays a role in the injection molding, which is to overcome the flow resistance of the plastic from the cylinder to the cavity, to give the rate of filling the mold and to compaction the melt.

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