2. mold defectsIf the gate position of the Mold is not correct or the gate section is too small, the main runner and branch runner are long and narrow, there are dead corners in the runner or the mold exhaust is poor, which will cause bubbles or vacuum. Therefore, first determine whether the mold defect produces bubbles and the main reason for vacuum bubbles. Then, according to the specific situation, adjust the structural parameters of the mold, especially the gate position should be set at the thick wall of the plastic part. When selecting the gate type, since the vacuum hole produced by the direct gate is more prominent, it should be avoided as much as possible. This is because the pressure in the cavity is higher than the pressure in front of the gate after the pressure holding is over. The molten material at the place has not been frozen, and the phenomenon of molten material backflow will occur, causing holes to form inside the plastic part. In the case that the gate form cannot be changed, it can be adjusted by extending the holding time, increasing the amount of feed, and reducing the taper of the gate. The gate section should not be too small, especially when molding several plastic parts with different shapes at the same time, it must be noted that the size of each gate should be proportional to the weight of the plastic part, otherwise, larger plastic parts are prone to air bubbles. In addition, the slender and narrow runners should be shortened and widened to eliminate dead corners in the runners, and eliminate the failure of poor mold exhaust. When designing the mold, try to avoid any extra-thick parts or large disparity between the thickness of the plastic part.
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