Re: [CAD_CAM_EDM_DRO] hot servo motors, heatsinks??

etauch wrote:

>Greetings,
>
>I am currently at the point where I am testing my CNC
>conversion. I notice that the servos get quite hot
>after about 5 min of running. Not so hot that I cant touch
>them, but if you grab one, you can only hold on comfortably
>for a few seconds.
>
>I know they are running at low RPM, so this is probably one
>of the causes (higher I^2R at low rpm?). Also, I am dumping
>many amps into a relatively small mass, so heat is to be
>expected.
>
>My question for those with experience with CNC servo motors.
>Does anyone install heatsinks on them?? At what point should
>you shut down to let them cool off? I think they are ok
>after 5 min, but if I were chugging away on something for 30 min
>or so, I think they might burn up.
>
>Some info on my setup...
>This is a HF 47158 micromill with 190 oz/in servos
>using direct drive (bracket and shaft couplers). I am
>running a Camtronics/Gecko320 servo driver box, and also
>installed a 20lb gas spring to offset the head weight on
>the Z screw.
>
>

I think your motors are dithering at high speed. They should run
cool. Check the data sheet on the gecko 320, I think there are
adjustments to reduce this heating. Do they get hot when just
enabled but not moving, or only when in motion? If only
in motion, then you need to put a belt reduction on them, to
reduce effort. If this minimill has 16 TPI screws, then a 2:1 belt
reduction may be all you can provide and still get reasonable
speed. If it has a coarser screw, you can go to 4:1 or 5:1,
and reduce torque demand even more.

Jon