HOT motors. Voltage problem ?

[DJ Morrow]

I have 3 - 258 oz steppers on my Sherline mill. The spec's are 4.20 amps and 2.31 volts each. They are wired as bipolar, parallel. I know that my power supply is a bit low on voltage. It's 28 Volts / 6 Amps.

I just ran a routine to do some engine turning which was a series of quick drilling points 1/2" apart and there was about 80 in total. The Z axis was doing most of the work although I only had it set at about 3" per minute.

The problem was it was horribly hot when I was done. In fact just after it stopped the drilling routine, I jogged it and it made a bit of a grinding noise. All was well after it cooled off.

Is it possible that I'm running the voltage too low ?

Maris at Gecko advised some time ago that with a higher voltage power supply I could run the motors in series with just about zero heat sinking as things would get too warm.

[H500]

Low voltage doesn't matter as long as it's within your controller's spec. What controller are you using?

The most likely cause is that you have your current limit set too high. Are you sure the mots are rated at 4.2 amps? It sounds too high for a 258oz stepper.

[DJ Morrow]

The motor spec sheet is here:
https://www.mcg-net.com/electric_mot.../IH_23_014.pdf

I'm using Gecko 201's and used their formula for the current set resistors. The formula looked like 47 x 4.20 \ (7-4.20) in K ohms. I get 68k ohms.

Thanks for taking the time to help. I'm pretty green on this part and I'm stumped.

[H500]

Are you sure you have it properly wired as bipolar parallel?

Also, measure your resistor with an ohmmeter to make sure you have the right value.