Valve assemblies according to the present disclosure include a channel with a channel proximal end and a channel distal end. The valve assemblies also include and an inlet that receives a nozzle at an inlet proximal end that injects a molten plastic into the channel. The inlet includes a first inlet surface at an inlet distal end fluidly coupled to the channel. The valve assemblies further include a valve translatably coupled to the channel and the valve translates between an open position and a closed position. The valve includes a valve proximal end, a valve distal end, and a first valve surface at the valve proximal end. A diameter seal is formed between the first inlet surface of the inlet and the first valve surface of the valve when the valve is translated from the open position to the closed position.