Analysis of the cause: the phenomenon of depression on the surface of the product. It is produced by shrinkage of plastic volume, which is common in areas of local fleshy thickness, such as ribs or column-to-face intersections. The localized meat thickness of the product is a vacuum bubble generated by volume shrinkage during cooling, called a void. When the plastic melt contains air, moisture and volatile gases, the air, moisture and volatile gases that enter the interior of the product during the injection molding process are called bubbles.
Countermeasure: Increase the size of the gate and runner so that the pressure acts effectively on the thick portion of the molded product. The position of the glue can also be adjusted if necessary. Increase the holding pressure and extend the holding time. Increase the filling speed and achieve full compression before the plastic cools and solidifies. The glue is transferred to the pressure too fast. Make the meat thickness change smoother and improve the cooling efficiency of this part. The colloidal particles are sufficiently dried in advance to remove moisture. The temperature setting of the barrel should not be too high, which can effectively prevent the generation of plastic decomposition gas. Use a small screw or machine to prevent over-shearing of the screw. Increase the back pressure so that gas can be expelled from the barrel. Appropriately reduce the filling speed, the gas has sufficient time to discharge.