The shape of cold runner section design in the plastic mold

The shape of cold runner could be round, trapezoid or U . In order to reduce the pressure loss and reduce the heat loss in runner path, we hope the runner section bigger, but the runner surfaces area should smaller. the round shape have the highest efficiency for reducing pressure and heat loss.

When the melt resin flow in the runner, the runner surfaces will be frozen, this will isolate the heating lose,melt resin will flow in the center, so perfect condition is that the runner center is same line with the gate center.