do you know a hot runner nozzle with a needle valve? That is so called valve gate, the gate mark produced by a valve gate tends to be clear, round and smooth, it works like this, before injecting, the valve is controlled by the cylinder, moves rightward and opens the gate hole so that fused materials can pass. Before the fused materials at the gate completely solidify, the needle valve is pushed to the left and closes, leaving a round and smooth gate mark.