Re: CNC Servo motor gear ratio: overheating. EMC step rate. Tablespeed

Hi Kim, its Dean from Edmonton. I am (temporarily) using the 7" long
version of that same motor on my RF30 mill. I noticed the Y motor get
a bit warm once but I turned the gain down and it cooled right off.
The heat was caused by excessive dithering. Now X and Y run great for
hours at a time with no heat at all. I am running the original 10 tpi
acme screws directly. As soon as I get a bit of time, I'll install the
.2 lead ball screw I have, 2:1 reduction, and some of the 5" motors.
Will still max out at about 100ipm, but that is plenty fast. Have a
look here

http://www.members.shaw.ca/axxus4/mill_drill/mill4.jpg

Dean

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Kim Lux <lux@d...> wrote:
> I agree that the spec doesn't make sense. These motors have 50 oz-in
> per amp torque, 4" bodies and a 5/8" shaft. These are relatively
> torquey motors.
>
> Kim
>
>
> On Sun, 2003-06-08 at 22:10, Jon Elson wrote:
> > Tim Goldstein wrote:
> >
> > >Jon,
> > >
> > >We discussed these particular motors previously on this group. The
> > >consensus was that these motors were not a good selection for direct
> > >drive on most mills. The only specs that are on the Camtronics
website
> > >are:
> > >
> > >These motors have a 5/8 diameter shaft 1.75L. The bodies are 4"
diameter
> > >and 4.5" long. It has a standard 3.250 DBC on the front face.
about 50
> > >oz in per amp torque and RPM is about 900. 36 VDC PM brush ball
> > >bearing.
> > >
> > >So at 25 rpm for his 5 ipm which I am assuming is a speed he plans to
> > >actually cut something at I think he will be risking getting very hot
> > >motors and potentially frying them.
> > >
> > >
> > Yes, I think I misunderstood his original post. I thought the 25 Lbs
> > of linear force to move the table was the total force he needed, but
> > he doesn't actually say that. he gives no indication whatsoever
of what
> > cutting forces will resist table movement. I think it is safe to say
> > that these motors COULD handle the 25 Lbs force without trouble,
> > but if he is cutting metal, that is another story. With a 900 RPM
> > limit, he is limited on what he can do in the way of reduction,
> > although 450 RPM on a 5 TPI screw is still 90 IPM, so maybe
> > a 2:1 reduction would still be acceptable. I also suspect these
motors
> > could be run over 900 RPM (over 36 V) without harm. If these are
> > the Ametek motors that have flooded the surplus market, the 4 Ohm
> > (or worse) armature resistance is the bad news on them. That makes
> > them VERY prone to overheating on any continuous load.
> > On any servo application where motors are drawing over a couple of
> > amps, I really hate to see over one Ohm of resistance.
> >
> > Jon
> >
> >
> > Addresses:
> > FAQ: http://www.ktmarketing.com/faq.html
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> Kim Lux <lux@d...>