In the injection mold, in general, every cooling circuit stays at one temperature over the complete cycle.
For parts with a high demand on surface quality it is important that the melt reproduces the cavity perfectly.
A variotherm process is used to achieve this.
Hereby one or more cooling channels will be processed with a lot higher temperature during filling phase (A in the picture below).
As this results in a longer cycle time, the coolant temperature is decreased during cooling phase (B in the picture below) to speed up the process.
The phase of mold movement (C in the picture below) is used to heat up the coolant of the specific circuits to the higher temperature for the next cycle.

Variotherm in Plastic Industry