Re: [CAD_CAM_EDM_DRO] small servo motors keep stalling

feck123 wrote:

>Hello...I have been trying to get my little Taig CNC mill going..I have a
>servo motor setup with little pittman motors. they say 24 volt, 5:9 ration and
>coupla other numbers..im not sure about the rpms.The whole setup is from
>a cnc retrofit company so it is not "homebuilt"at least by me , but the tech
>support has not been able to help me figure out why my motors keep
>stalling out at the SLIGHTEST bit of resistance....the gibs must be all the
>way backed out for the motors to not stall.....i havent even tried to mill
>anything....the taig has a 1/2-20 screw--no ballscrew--and i have a
>direct/staight coupling to the motors using interlocking spiders with
>plastic piece in the middle of the spider to accomadate axial
>misalignment...backlash is about .003 in Y and Z and .01 in X..just
>wondering if could get ANY sugestions or help....do i need to change to
>belt drive ? Tahnks for any and all help Mike
>
>

What are you using for servo amps/drivers? What is the current rating
of the motors,
and what is the current limit of the amps set to?

I have a fair guess what size these Pittman motors are, even with a 20
TPI thread on
the leadscrew, there are probably not capable of running it directly.

I have 40 Lb. motors on my machine, specifically designed for low speed
operation, and I still have a 2.5:1 belt reduction ratio on it. And, I
DO have
ballscrews, too! I can't imagine an Acme thread at 20 TPI, so it must be
a 60 degree threadform. VERY inefficient for power transfer.
To get linear movement at 60 IPM, your screw needs to spin at 60 x 20 =
1200 RPM.
I suspect that motor can turn 6000 RPM without much trouble, so a 5:1 belt
reduction might be a good place to start. That only gives you a 5 x
increase
in torque, but that might be enough. It certainly will help.

What is this 5:9 ration about? Is this a gear motor? If so, what
backlash is there
in the gears? Otherwise, I don't know what that means.

Jon