Stepper motor inside are composed of iron core and the windings. Winding resistance, electricity use will produce a certain quantity of heat.
It like woodworking engraving machine spindle motor, temperature is continuously rises, spindle motor has only to reduce the heat generated by the cooling water cycle. But there is no water cooling step motor, so how to judge its temperature overheating problem.
Actually very simple question. Stepper motor heating reasonable range, electrical heating allows to what extent, mainly depends on the internal motor insulation class.
Internal insulation performance at high temperatures (130 degrees) will be destroyed. So as long as within no more than 130 degrees, the motor won't damaged.
We may can't be measured accurately to the internal temperature, but we can measure the surface temperature of the machine. When the internal temperature of 130 degrees, the outside will be around 90 degrees. So, step motor surface temperature in 70-70 degrees are normal.
Simple useful point thermometers, temperature measurement method can also be rough judgment: by hand can touch more than 1 to 2 seconds, no more than 60 degrees; Only with the hand touch, about 70-80 degrees; Drop a few drops of water gasification quickly, more than 90 degrees.