Is anyone aware of a good deal on servo motors large enough to power a
Bridgeport mill clone (49 X 9 table)? The mill will have acme, not ball
screws. From what I have read I need servos that have about 28 lbs/inch of
torque, although I suspect that is for ball screws.

You've heard of Ebay?

Another route is to make a servo out of an ordinary DC motor. See:
http://truetex.com/servomod.htm

You'll need more torque for ACME vs. ball screws. Bigger motor or belt down.

--
(©¿©) An apple a day keeps the doctor away.
Two apples a day gets the doctor's OK.
Five a day makes you a fruit grower like me.

Karl Townsend

On Sat, 27 May 2006 16:33:19 -0500, "Karl Townsend"
remove .NOT wrote:

You've heard of Ebay?

Another route is to make a servo out of an ordinary DC motor. See:
http://truetex.com/servomod.htm

You'll need more torque for ACME vs. ball screws. Bigger motor or belt down.

Where are you located? I have one 500 watt ( I think) 84 volt DC
servomotor left in the garage. It is a printed circuit armature(disk
motor) type Permanent Magnet unit - about 35 lbs. I think it also has
a brake on it. Definitely has quadrature encoder and tach output. It
is in Waterloo Ontario. I shipped 2 similar motors to Virginia for
about a dollar a pound.

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I got 2 of what you need with controlers....
E-mail me at




Rich Goldner wrote:
Is anyone aware of a good deal on servo motors large enough to power a
Bridgeport mill clone (49 X 9 table)? The mill will have acme, not ball
screws. From what I have read I need servos that have about 28 lbs/inch of
torque, although I suspect that is for ball screws.

I tried emailing you, but the email got returned to me.

Let me know what you have and how much it will cost.





wrote in message
oups.com...
I got 2 of what you need with controlers....
E-mail me at




Rich Goldner wrote:
Is anyone aware of a good deal on servo motors large enough to power a
Bridgeport mill clone (49 X 9 table)? The mill will have acme, not ball
screws. From what I have read I need servos that have about 28 lbs/inch
of
torque, although I suspect that is for ball screws.

Rich Goldner writes:

Is anyone aware of a good deal on servo motors large enough to power a
Bridgeport mill clone (49 X 9 table)? The mill will have acme, not
ball screws. From what I have read I need servos that have about 28
lbs/inch of torque, although I suspect that is for ball screws.

"Large enough" depends on what sort of speed and acceleration you want
to have, since you can always gear down to trade less speed for more
torque.

Industrial CNC machines do 100s of inches/minute. That's a bit
ambitious for a hobbyist or a retrofit.

I am using these to do 90 inches/minute with ballscrews and 2:1 timing
belt pulley ratio:

http://www.truetex.com/mcgpd34002.htm

They are rated for 34 lb-inch peak, but develop significantly more with
Geckodrives. You would have to tune things differently for Acme screws,
perhaps a 3:1 or 4:1 ratio to overcome the 50 percent (in)efficiency.
Ballscrews are not expensive when you realize that they halve the cost
of your CNC drives by virtue of the mechanical efficiency. You then
have the ability to cut curves and holes that are spoiled by backlash-
compensated Acme screws.

Realize that that kind of torque at slew speeds amounts to about a full
horsepower, which implies a very expensive servo, if you want that kind
of performance continuously.

I have found that the shaft size of a motor can be a better indicator of
true performance than the spec sheet.

If you have X and Y converted, you should also consider doing the knee
for Z, using a still bigger motor and higher gear ratio. You don't need
speed on that axis but the mass being lifted requires a lot of torque.
If you avoid running Z simultaneously with X and Y, you can avoid the
need for a beefier power supply. I really enjoy not having to hand-
crank that thing.

I need $150.00 for everything....
Goto WWW.Beitz.net for my E-mail address...

See pictures at ....

http://user.pa.net/~kbeitz/Post-em/Stepper%20motors.jpg

Try my E-mail again... I needed to reactvate it again.... Working now...

Sorry, I need much more torque then your steppers can deliver.

wrote:
I need $150.00 for everything....
Goto WWW.Beitz.net for my E-mail address...

See pictures at ....

http://user.pa.net/~kbeitz/Post-em/Stepper%20motors.jpg

On 28 May 2006 08:30:16 -0700, wrote:

Sorry, I need much more torque then your steppers can deliver.

wrote:
I need $150.00 for everything....
Goto WWW.Beitz.net for my E-mail address...

See pictures at ....

http://user.pa.net/~kbeitz/Post-em/Stepper%20motors.jpg

Mine has a LOT more torque. It is an 8" frame "print motor"

%150 plus shipping, or make an offer.

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Unfortunately your motor is too big and heavy.

According to :
Unfortunately your motor is too big and heavy.

It looks about the size that the stepper motors on my Bridgeport
BOSS-3 (Series I) were -- and *that* had ballscrews. You will probably
need something bigger to drive Acme screws. This was made from scratch
as a CNC machine -- back around 1975 or so, IIRC.

And they were mounted more inboard -- the X-axis under the table
to the right of the knee (and it turned the ball-*nut*, not the screw,
which was rigidly mounted to one end of the table). The Y-axis is
mounted under the knee, and the Z-axis mounted to the right of the head,
with the ball screw hollow and surrounding the quill, so the force is on
the axis of the quill, instead of on one side thus being likely to tilt
the quill and produce uneven wear.

And -- the stepper motors were mounted inside a massive finned
heat sink with a thermal goo between the OD of the motors and the ID of
the heat sink assembly.

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 29 May 2006 03:48:28 GMT, (DoN. Nichols)
wrote:

According to :
Unfortunately your motor is too big and heavy.

This motor came out of an articulated welding robot.

It looks about the size that the stepper motors on my Bridgeport
BOSS-3 (Series I) were -- and *that* had ballscrews. You will probably
need something bigger to drive Acme screws. This was made from scratch
as a CNC machine -- back around 1975 or so, IIRC.

And they were mounted more inboard -- the X-axis under the table
to the right of the knee (and it turned the ball-*nut*, not the screw,
which was rigidly mounted to one end of the table). The Y-axis is
mounted under the knee, and the Z-axis mounted to the right of the head,
with the ball screw hollow and surrounding the quill, so the force is on
the axis of the quill, instead of on one side thus being likely to tilt
the quill and produce uneven wear.

And -- the stepper motors were mounted inside a massive finned
heat sink with a thermal goo between the OD of the motors and the ID of
the heat sink assembly.

Enjoy,
DoN.


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