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The injection molding process of the injection mold factory usually divides the control of injection pressure into the control of primary injection pressure, secondary injection pressure (holding pressure) or more than three injection pressures.
Whether the timing of pressure switching is appropriate is Plastic quality household mould/mold very important to prevent excessive pressure in the mold and prevent flash or shortage of material. The specific volume of the molded product depends on the melt pressure and temperature when the gate is closed during the pressure holding stage. If the pressure and temperature are the same every time when switching from the holding pressure to the product cooling stage, the specific volume of the product will not change.
Injection mold factory injection molding process at a constant molding temperature, the most important parameter that determines the product size is the holding pressure, and the most important variables that affect the product dimensional tolerance are the holding pressure and temperature. For example, after filling the mold, the holding pressure will immediately decrease. When the surface layer has a certain thickness, the holding pressure will rise again. In this way, a low clamping force can be used to form large thick-walled products and eliminate craters and flash. The holding pressure and speed of injection molding in the injection mold factory are usually 50%~65% of the highest pressure and speed when the plastic is filled in the cavity, that is, the holding pressure is about 0.6~0.8MPa lower than the injection pressure. Since the holding pressure is lower than the injection pressure, the load of the oil pump is low during a considerable holding time, the service life of the solid oil pump is prolonged, and the power consumption of the oil pump motor is also reduced.
Three-stage pressure injection can not only fill the part smoothly, but also will not appear welded lines, dents, flashing and warping deformation. It is good for the molding of thin-walled parts, small parts with multiple heads, large parts with long processes, and even parts with uneven cavity configuration and tight mold clamping.