Re: Servo Question

Hi,
The numbers are defenatly right, its possible theirs a mistake at
the source. They were taken from:
http://www.baldor.com/products/specs.asp?
1=1&page=1&catalogonly=1&catalog=MTE-2250-
AMACN&product=Servo+Motors&family=DC+Servo%7Cvw%5FServoMotors%5FDC

I'm currently using 200 oz steppers on a mini mill. I'm occasionally
loosing steps. I'd like some more top speed and a little extra
torque. I'm not seeking a huge increase in speed or torque, but
primarily just the advantages of a closed loop system not loosing
position. I want to be able to walk away and be confident its not
going to loose position do damage from a crash or something.

So to replace 200 Oz steppers what size servo should I be looking
at? My current rapids translate into 600 RPM. Would be great if I
could run the lead screws at about 1000 rpm and still have a little
extra torque. So if I was using a 5000 rpm motor (5:1 reduction) id
need it to have around 40 oz-in continious torque? Or could I get
away with something smaller? Kind of makes sense that something
smaller would work since its not needing to provide 40 oz
continiously.

Basicly what would be a good motor (that will run off Gecko 320's)
to replace 200 oz steppers?

Thanks for all the help so far.

Mark

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
>
>
> mmurray701 wrote:
>
> >I'm considering converting from steppers to servos (DC). After
> >looking at some specs it seems that continious stall torque is
far
> >lower than peak torque. One motor I was looking at has a
continious
> >stall torque of 3.313 lb-in, and peak torque is 300 lb-in! Why is
> >there such a huge difference? Can somebody give me a defenition
of
> >each?
> >
> >
> >
> Are you sure about those numbers? a 100:1 difference is a bit
unusual.
> The numbers
> I am more accustomed to are in the range of 4:1 up to 10:1. The
> continuous stall torque
> is the torque the motor can exert indefinitely, and it causes
gradual
> heating. The peak
> torque is the maximum torque the motor can produce for a short
interval,
> often only
> a fraction of a second. This is generally limited by the
resistance of
> the permanent
> magnets to demagnetization from armature reaction.
>
> >I know approximatly how much torque I want on the leadscrew,
which
> >motor torque value do I use to figure out pulley ratios? Please
help
> >me out. Thanks.
> >
> >
> If your torque requirement is for the steady-state cutting forces
needed
> to drive the
> work into the cutting tool, then the continuous number would
apply. If
> the torque
> requirement is for the peak load during acceleration to rapid feed
> rates, then the peak
> torque value would be the spec.
>
> By the way, 300 In-Lb is a HUGE amount of torque. You will likely
need
> massive
> belts or couplings to carry this torque without breaking.
>
> Jon