On the front of the machine is a button. With this you set the heat from 0 (off) to 10 (maximum). The numbers do not correspond to a certain heat in degrees Celsius. This depends on the outside temperature, frequency of use, and type of cheese. Young cheese cools the blade faster than old cheese. 

Find the setting that works for your situation. 

Always set the knob to 0 after use and at the end of the day!