Re: Bridgeport Boss 6 Stepper Motors

Jon, these motors are 400W continuous. The peak rating is about
1200W. They have a max RPM of 4500, but torque falls off at this
speed.

Maybe I should use a higher gear ratio like 4:1 as I shouldn't need
full torque for rapids. This would give 225 IPM rapids with a 5 TPI
ball screw and would give about 1200 lbs of continuous thrust with a
peak thrust of about 3600 lbs. This sounds like it should be more
than enough.

Why do you think Bridgeport used such large motors? Are they geared
for really fast rapids?

~petev

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
> vavaroutsos wrote:
>
> > Jon, I have no problems making the calculations for torque and
power
> > required based on ball screw efficiency, TPI, IPM rapids, etc.
Where
> > I fall short is in the machinist knowledge area. I don't have a
good
> > feel for how much force is required on the X, Y, and Z axis for a
> > series 1 machine.
>
> I used 1000 Lbs. as a wild guess at the required force, for
acceleration,
> friction and cutting forces combined. I tried to do a calculation
on the
> worst case cutting force that could be delivered to the workpiece,
but
> it seemed pretty crude. You can figure 1 HP as 550 Ft-Lb/Sec. A 1"
> diameter tool has a 3.14" circumference, and at 60 RPM, it would be
> moving at a tangential velocity of 3.14 IPS, or 0.262 FPS. So, 550
Ft-Lb/Sec
> divided by .262 Ft/Sec = 2102 Lbs! Now, generally, you won't run a
> 1" tool at only 60 RPM, so these forces are almost certainly greater
> than you will ever experience with a 1 Hp spindle motor, but they
give
> some idea of what the worst case could be.
>
> > I was looking at some 400W, 3000RPM servos that would provide
about
> > 600lbs of force with 300 IPM rapids on a continuous basis with a
2:1
> > reduction. These are roughly 1/2hp motors. Based on your success
with
> > 1/8hp motors I guess these are more than enough. Thanks for the
info.
>
> If those are 400W Continuous, you should be fine. If they are 400
W peak,
> they are pretty marginal. I figure I am running about 1/2 Hp
peak. Note
> that the stock motors in Bridgeport's EZ-Trak servo machines are
> about 1 Hp continuous, with rediculous peak ratings - something
like 26
> A at 140 V = 3640 W = 4+ Hp.
>
> Jon