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

On Mon, 2003-06-09 at 17:32, deanc500 wrote:

> Hi Kim, its Dean from Edmonton.

Hi Dean. Thanks for replying. It was good talking to you the other
day.

> 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.

OK. That motor probably has 40% more torque than mine.

> 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.

Your motor is 40% more powerful.
Your ACME screws take 3x more torque than my ball screws for the same
loading.
Your screw is half the pitch meaning it takes half the power.

Overall, your motor load will be:

3 x 0.5 = 1.5 times what mine will be. However, your motors are 1.4 x
as powerful, so the motor/load ratio will be about the same.

Have you taken any heavy/long/slow cuts to make sure they won't overheat
?

> 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

If you left the drive at 1:1, you'd get 200 IPM and your loading would
be the same as now. I'm looking for some speed.

> 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:
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> > --
> > Kim Lux <lux@d...>
>
>
> Addresses:
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> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
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>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

--
Kim Lux <lux@...>