When melt with unsteady flow is injected into the mold cavity through the runner and gate in semi-solidified state, refluence and stagnation can form during its flow in the cavity due to the extrusion and pushing by follow-up melt that is continuously injected therein, and thereby wheel wave flow mark centering around the gate occurs on the surface of plastic parts.

The treatment measures include raising mold temperature and nozzle temperature, improving injection rate, increasing injection and dwell pressure, properly designing size and position of cold-slug well and optimizing design of feed system so that the unsteady flow of melt can be improved through the shearing heat during the flow and filling of melt.