TB 6600 getting hot

I have been testing nema 23 3Nm Stepper Motors with the TB6600 Stepper driver with no load on them. After a minute the drivers get so hot they shut themselves off. I reduced setting to 2.5 A they run a bit longer. When i use micro stepping 8:1 they are fine. Why do they get hot unless I use microstepping?

The steppers can be in one position for a long time the drivers were only getting hot when motors were turning. Could it be that resonance caused the overheating?

Or is there some other reason?

Just to add yes these drivers have heatsinks. I wonder if I should add a cooling fan.

what voltage are you running them at?

be careful with the amperage settings, as there is a difference between RMS and PEAK amperage (RMS = PEAk / SQRT(2) )

also how you wire them will give you a different current rating (my stepper motors are 8 wire (mostly) and 6 wire (which can be a bit odd ball).. so I have a few different ways I can wire them and they require different current settings depending on the wiring

do you have a datasheet for the stepper motors and your tb6600 drives....

you can (normally) set the stationary current at 1/2 (or adjustable depending on your drives) .... stepper motors should run hot though

I killed a load of tb6600 drives when I first started out with CNC.... they did not like me running them at 42V and did not like me running them on a switch mode power supply as it squeaked and squarked under spread changes (back emf)

I then bought some proper drives and toroidal transformer power supply. same stepper motors run silent and much cooler

I run them on 36 volt after all the manual says 42v peak. 36v recommended.

I attached the data sheets for steppers drivers and power supply.
As I said Stepper Motors don’t get hot only the drivers I run them on 3A rms.
Run 1 minute before hot.
2.5A rms runs 2 minutes before getting hot. Microstepping 8:1 2.5A no over heating.