Problems and Improvement Methods in the Molding Site: Methods for Improving Sink Marks

What are the causes of sink marks and voids? Measures such as adjusting molding conditions and product design are necessary.

Resin undergoes volumetric shrinkage during the cooling and solidification process. The high volumetric shrinkage rate, particularly in thicker sections, is a primary factor. The layer that solidifies early after injection on the product surface, referred to as the skin layer in the industry, can lead to voids inside the product under conditions where pressure loss occurs during the cooling process. If the surface solidification layer is thick and robust, voids may form inside the product. Conversely, if the surface solidification layer is thin and soft, sink marks may occur. Additionally, sink marks and voids can occur simultaneously. Measures to mitigate sink marks involve adjustments in molding conditions and product design. 【Methods to Address Molding Conditions】 ■ Increase the internal pressure of the resin ■ Thicken the surface solidification layer to forcibly create voids ■ Use foamed materials to mold without lowering internal pressure *For more details, please refer to the PDF document or feel free to contact us.

Contract manufacturingProcessing Contract