Re: [CAD_CAM_EDM_DRO] 13x40 cnc
Posted by
Jon Elson
on 2007-07-25 22:51:53 UTC
Arnie Minear wrote:
Unless it has over 5 Hp on the spindle, I can't see how you need
that much torque.
You can use a belt reduction to both make the motor-leadscrew
coupling and increase motor torque, as servo motors generally
have plenty or RPM. Assuming common lathe hardware, you'd have
8 TPI on the Z and 10 TPI on the X. If using generic
ballscrews, then it would likely be 5 TPI on both. That's the
worst case, so let's use that. 200 IPM on a 5 TPI screw is 1000
RPM. That could cause some whip on a small-diameter Z screw.
But, anyway, with a 3:1 reduction, the motor would do 3000 RPM
to turn the ballscrew at 1000 RPM. With 200 Oz-In from the
motor, you get 600 Oz-In at the screw. That equals 37.5 Lb-In.
If you apply 37.5 Lb-In to a 5 TPI screw, you get 1179 Lbs of
linear force on the carriage. Is that enough to break things?
You'd better select a peak torque that your machine can handle
without breaking castings!
(If you are wondering how I got from 37.5 Lb-In to 1179 Lbs
force, I use a conversion factor derived from the diameter of a
spool that would give .2" advance per revolution. Such a spool
would be .0318" radius. This is much easier than calculating
the pitch angle of a helix, and allows the pitch diameter of the
ballscrew to cancel out of the equation. All that really
matters is how far the nut advances per full revolution of the
screw.)
Jon
> I have a 13x40 on order and I am looking for ideas and specs onThis seems pretty excessive. What motor does this machine have?
> converting it to CNC. I am also considering documenting the process
> and eventually offering a kit. There seems to be a lot of info and
> resources out there for the smaller ones, 7X and 9X.
>
> I did a search and found a very little on converting a 13x40 to cnc
> just not a lot out there. Anyone with pic's or ideas.
>
> I would guess in the range of 1000oz steppers for the Z and 800oz for
> the x. Probably ballscrews on both z & x.
>
Unless it has over 5 Hp on the spindle, I can't see how you need
that much torque.
> What about servos? Any ideas on size to get in the range of 200ipm.I would guess that 200 Oz-In continuous motors should do it.
You can use a belt reduction to both make the motor-leadscrew
coupling and increase motor torque, as servo motors generally
have plenty or RPM. Assuming common lathe hardware, you'd have
8 TPI on the Z and 10 TPI on the X. If using generic
ballscrews, then it would likely be 5 TPI on both. That's the
worst case, so let's use that. 200 IPM on a 5 TPI screw is 1000
RPM. That could cause some whip on a small-diameter Z screw.
But, anyway, with a 3:1 reduction, the motor would do 3000 RPM
to turn the ballscrew at 1000 RPM. With 200 Oz-In from the
motor, you get 600 Oz-In at the screw. That equals 37.5 Lb-In.
If you apply 37.5 Lb-In to a 5 TPI screw, you get 1179 Lbs of
linear force on the carriage. Is that enough to break things?
You'd better select a peak torque that your machine can handle
without breaking castings!
(If you are wondering how I got from 37.5 Lb-In to 1179 Lbs
force, I use a conversion factor derived from the diameter of a
spool that would give .2" advance per revolution. Such a spool
would be .0318" radius. This is much easier than calculating
the pitch angle of a helix, and allows the pitch diameter of the
ballscrew to cancel out of the equation. All that really
matters is how far the nut advances per full revolution of the
screw.)
Jon
Discussion Thread
Arnie Minear
2007-07-25 09:34:31 UTC
13x40 cnc
Jon Elson
2007-07-25 22:51:53 UTC
Re: [CAD_CAM_EDM_DRO] 13x40 cnc