During the filling process of the injection mold, the temperature of the plastic melt in the mold cavity drops, the viscosity is high, the plastic melt contacting the mold surface is semi-solidified, and the surface flows vertically to countless fine lines, resulting in ripples similar to fingerprints on the product surface.
When the temperature of the plastic melt drops again, the filling is not completely solidified, resulting in insufficient filling. Ripples usually occur on the edges and fill ends of plastic products. Causes and Countermeasures of Ripples in Plastic Parts During Injection Molding
(1) The gate freezes too fast and shrinks insufficiently. In this case, it is possible to increase the temperature of the plastic melt and the temperature of the injection mold, maintain high temperature, fill with low viscosity, and increase the gate size appropriately.
(2) Insufficient pressure holding during injection molding leads to insufficient feeding. At this time, the pressure should be increased.
(3) The temperature of the plastic melt in the stagnation zone drops beyond the molding temperature range, resulting in ripples. At this time, the gate position or cooling water path should be adjusted.
(4) When the filling speed of the plastic melt is too slow, the temperature drops too much during the filling process, and the insufficient filling causes ripples. At this time, the screw speed and pressure should be increased, or external lubricant treatment should be performed to prevent excessive pressure loss.