Notes For PVC Injection Stage
Normally, the injection process refers to the plasticizing stage and the injection molding stage.Whether the injection is appropriate, affecting the appearance of the final product, performance and so on.. Here will be some attention points of the two stages of the plastic phase.
1. Plasticizing stage
The stage of plasticization is the important process of melting material to the viscous flow which can be injected normally. The principle of operation is to maximize the physical properties of the injection molding material and to have sufficient low viscosity to fill the material at the lowest possible temperature, so that the production process has the greatest operational flexibility
2. Injection molding stage
In view of the characteristics of hard PVC resin, we should pay attention to the following points during injection molding:
A.The injection process in the barrel temperature control at 170 ~ 190 ℃. When the barrel reaches the temperature, it should be controlled by the temperature control system in the injection molding machine.
B.In order to make the PVC granules be fully injected into the mold cavity, each speed should be uniform. General injection speed to use multi-stage control, the principle is slow start injection, with the gradual increase in the area of the formation of sub-section to increase the injection rate, the product without cracks and obvious welds based on the injection speed can not be too high.
C.Pre-plastic back pressure should be controlled as much as possible within 1.0MPa, too high back pressure will produce excessive shear force, so that hard PVC overheating decomposition. At the same time should be used in the melt process using multi-level back pressure control.
D.Because of the high viscosity and thermal sensitivity of hard PVC, screw speed should be controlled. Under normal circumstances, if the screw diameter is small than 60mm, then the speed is 50 to 70r/min.And if the diameter greater than 7omm, then the speed is 20 ~ 50r/min.
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