The Chinese injection moulding guide is based on our current knowledge and experience. In view of the many factors that may affect processing and application in a mold making factory, this data does not relieve processors from the responsibility of carrying out their own tests and experiments; neither does it imply any legally binding assurance of certain properties or suitability for a specific plastic injection mold. We expressly disclaim liability for any loss, damage, or injury directly or indirectly suffered or incurred as a result of or related to anyone using or relying on any of the information in this documents. Residence time is the amount of time the resin is exposed to heat in the barrel. If there is inadequate residence time the molecules will not absorb heat uniformly throughout the material. The under-heated material will become stiff and will cool before the plastic injection mold is properly packed in the Chinese mold making factory. This causes the molecules to shrink at different rates during the cooling process which results in injection mold warpage.

A schematic of the main elements of a Chinese injection molding machine in the factory. It consists of a hopper that holds the raw plastic pellets. The hopper feeds the barrel with the plastic. The plastic is melted in the barrel and with the help of the screw (piston) is injected into an injection mold. The plastic injection mold being colder than the plastic rapidly cools and solidifies the plastic. The injection mold is then opened and the part is ejected out of the injection mold in China. To reduce or control shrinkage and warping of the injection mold, it is also essential to avoid non-uniform wall thickness. You need to balance the filling pattern, and use a proper packing pressure level for the mold in China. This allows sufficient packing time and removes the pressure after the gate freeze. The cooling system should apply uniform cooling across both the thickness and throughout the part, in order to reduce residual stress.