I consider mold cooling one of the most important elements of a mold design | Injection Molding
The purpose of producing a plastic part in the injection molding process is to design and build a mold that will produce consistent parts at the fastest cycle time possible. Some plastics require a cold mold and some require a warm or hot mold. Both essentially are cooling the part so it is ready to be ejected from the mold.
Cooling a mold is done in a variety of ways. The most common are drilled holes that make up a circuit that consists of an in port and an out port. This type of mold cooling is commonly used on plastic parts that are square or rectangle and usually follow the shape of the part. They are also used in the mold plates if needed. This is also the most economical way to install water into an injection mold. This method can also be used for heating a mold. Cores that are standing in mid-air absorb the most heat in an injection mold and must be cooled in order to run an acceptable cycle time. Cooling a core is usually done with baffles or bubblers. Baffles are thin pieces of brass that are mounted up the center of a drilled water line. For example, a 1″ diameter core that is standing up 6″ would have a hole that is drilled in the center and roughly 5 5/8″ deep. The water comes in the bottom of the drilled hole and travels up one side of the hole until it hits the top of the waterline where the baffle ends and then travels down the other side of the waterline to the bottom of the core and out of the mold to make a complete circuit. The bubbler works basically the same except the bubbler is a piece of round brass with a hole in the center. Here the water flows up the center hole and then goes down the outside of the bubblier and then out the mold.
Heating the mold up to 200°F can be done the same way as cooling the mold. If a hotter temperature is needed, then hot oil can be used in the waterlines. Another option for a mold temperature over 200°F is the use of cartridge heaters along with thermocouples.
These are just a few and the most common options that can be used for mold cooling in injection molding. The most important thing is not to let mold size or mold cost force you to cut corners on mold cooling. This part of the mold design can make or break you on the final part price.