Lathe Spindle for CNC Router

[tpsimer]

Good Afternoon,
I built a cnc router 5 years ago and it is running great. I now want to hook up a 4th axis to use as a wood lathe with live tooling. I found in my garage a 2hp treadmill motor. It is 130v dc variable speed.
I now have a couple of questions: What kind of board if any could I work with this to control the spindle speed from my computer? On and Off? Reverse and Forward? Could I use this motor with an encoder to control positioning for a 4th axis? What would I need to do this? If I cant control the positioning I know I would still need an encoder for the speed control. I would just hook it up to read the spindle. Any help or links would be appreciated. I expect to start to build soon and will post pics as they the project is completed.
Thanks
tony

[mike_Kilroy]

leeson has dc 180vdc scr variable speed controls for this kind of motor.

[sch]

Treadmill motor with SCR drive will be fed chopped 60cycle AC, and
will not work very well at motor speeds below perhaps 600-1000rpm
because lower speeds will be seeing severely chopped 60 cycle
and will start cogging. HP delivered is speed dependent, the 2 hp
rating is achieved only at 130VDC input, where the motor will likely
be running at 5-6K rpm. You can't get 130vdc out of the controller
unless it has a large stepup transformer from 110VAC or is run off 220VAC.
Most drivers, such as Mike mentioned, do not have transformers and
a 180VDC output requires the 220V input.
Check the current rating of the motor, it might need 12-14A at max
power. You may need to consider a timing belt speed changer
depending on your spindle speed requirement.

[tpsimer]

Thank you for your reply. If I was clear about what I am trying to do and you understood the post, what kind of motor would you suggest. I would very much like to control this with my computer so I can do threading and such. I will only be working with wood so the horsepower requirements won't be as much as for harder materials. This is sort of a practice before building a cnc lathe. I would like to start here so I can learn how to set things up before spending lots of money on a real machine. I will probably even make the headstock out of MDF.
tony

[sch]

My interpolation is that you want the 4th axis to function in a lathe
like fashion, ie rotating longish stock, but under the router with
the router doing the cutting. This suggests rpm in the 5 to say 300
or so. Sounds more like a stepper with a stepper driver, size dependent
on cutting loads, weight of work but likely not very big, again I would
refer you to the gecko site for some insight into motor sizing. If you
use the treadmill motor you would have to use a PWM controller
running at hundreds or low thousands of herz and a fairly hefty power
supply, in addition to mounting an encoder. Such a controller would be
considerably more expensive than even the Leesons, which are dumb controllers
and do not interface with computers.

[tpsimer]

I do want the slow speeds for doing intricate carving. I also want the higher end speeds of say up to 3000 rpm's for doing conventional turning. I would mount stationary tools in a sort of gang style using the z-axis for centering the cutters. If they are stacked and I have a 4 inch stroke on the z I could get 4 cutters mounted. Two on each side of the z axis mount at about 3.5 inches apart. This is why I would need reverse. I could also mount a delorian style tool holder in place of the router for changing tools. I am thinking of making chess pieces with carvings and such. Maybe I should go with a servo and a driver for that. I just don't know how to dual define it for spindle and c-axis control.
tony

[mike_Kilroy]

actually 120vac makes 160vdc for motor control so you can and do get 130vdc easily from 120vac input if it is a PWM drive: if SCR drive, sch is right, it outputs 90vdc from 120vac input. PWM drive is about as cheap as an scr drive in this size today so I would go with it. Again, I have bought these from Leeson in past. They can run dc motor down to like 10rpm very smoothly.

[RedskinsJBS]

Originally Posted by tpsimer I just don't know how to dual define it for spindle and c-axis control. tony

IIRC, in Mach3 (assuming that is what you are using to control the machine) you can create multiple machine profiles. So, if you are in Lathe mode, select the lathe profile. If you are in 4 axis mode, select the 4 axis profile. Easy!

HTH,

Jay

[Al_The_Man]

Originally Posted by sch Treadmill motor with SCR drive will be fed chopped 60cycle AC, and will not work very well at motor speeds below perhaps 600-1000rpm because lower speeds will be seeing severely chopped 60 cycle and will start cogging..

I have used them down to very low rpm with no problem.
If the motor has a tach, even better.
BTW, the switching frequency is 120hz as they are commonly switching a full wave bridge.
It would be 60hz for half wave.
KB and Baldor both sell the same product.
Al.