Sprue: The sprue is what the plastic resin hits first after exiting the sprue bushing. This is normally a deeper imprint in the mold and leads the plastic to the runners.

Runners: The runners flow to each of the mold cavities and allows for even flow while using as little resin as possible.

Gates: At the end of each runner the plastic resin enters the cavity through a gate. There are many different types of gates but the most popular are edge gates and tunnel gates.

Shut Offs: Shut offs block the plastic from entering a selected area, most commonly used when a part needs a hole or requires a hollow aspect.

Water Line: A water line is a channel inside the “B” and “A” plate that lets cold water flow through to keep it cool. The water line also helps cool the parts quicker for faster cycle runs depending on the type of plastic resin used. Not all molds require a water line.

Heating Cartridge: Rather than cooling a mold, sometimes a mold needs to be heated to keep the plastic from hardening too quickly. Heating cartridges are electric steel rods that are inserted into the mold to keep it hot. Engineering grade thermoplastics require mold temperatures of over 200° F to help stabilize the plastic during the cooling process. This will also help prevent short shots.

You can also heat a mold with hot water through the water line, but these lines usually only go as high as 150° F.