After the plastic passes the gate it flows into the mold. The mold is generally two big blocks of steel. Our 73 Qt Tote Box mold weighs about 10 tons!! The blocks are shaped and fitted together so that one block forms the inside of the part and the other block forms the outside. High pressure is applied to the plastic until the mold is filled, and then cooled enough to become solid again.
The mold has a series of channels inside through which we pump cold water to take the heat away and cool the part. While the part is cooling, the injection screw starts turning again to get ready for the next cycle.