You cant as far as I know, that is a function that most stepper drives have internally (current reduction) so if your drives dont have that then afraid you are out of luck as far as I know.

Hood

Thanks anyway.
It seems that I dont have access to STEP and DIR signals in VB
http://www.machsupport.com/MachCustomizeWiki/index.php?title=VB_Constants_for_Signal_Names
is that true?

or if not how can i access them

YOu cannot do what you are asking. Mach is a machine controller IT controls the step and direction outputs not you.

Your problem seems to stem from a VERY bad drive design. Redesign the drives to industry standards and your problem of overheating will go away.

You can certainly control the enable signals BUT nowhere near fast enough to use as a heating control mechanism. You would loose control of the output pulse stream and loose steps every time you tried to start movement.

Mach was not designed to correct BAD design flaws in drive controls.

Sorry, (;-) TP

I solve this problem with microcontroller