excello conversion stepper to servo

[roonster71]

hi all i just recently purchased a xlo knee mill cnc model 602? for a great price but the controllers were shot it was a 1970's paper tape reader it had 1100 Oz-In slo-syne steppers installed at 200 steps per revelution direct drive, now here is my question there is about 2" of table travel per revelution on the leadscrew (ball type) if i use a dc servo (Continuous Stall Torque (Oz-In) 352
Peak Torque 1760 (Oz-In) 1760.) that run up to 1700 rpm, should i use reduction belt an pully set up, or direct drive??



thanks

[2muchstuff]

Stepper motors produce their torque at a low RPM range and servo motors produce their torque at a higher but broader RPM range. With that being said, I would use a belt and pulley reduction. Are the original steppers still good/ usable, you may be able to get away with changing out the controllers to a newer style.

[roonster71]

Originally Posted by 2muchstuff Stepper motors produce their torque at a low RPM range and servo motors produce their torque at a higher but broader RPM range. With that being said, I would use a belt and pulley reduction. Are the original steppers still good/ usable, you may be able to get away with changing out the controllers to a newer style.

the steppers are pretty old 1.3v 20amp dc i have a rutex controller just wondering how much reduction is needed for those servos 2:1?

[Al_The_Man]

Originally Posted by roonster71 2" of table travel per revelution on the leadscrew (ball type) if i use a dc servo (Continuous Stall Torque (Oz-In) 352 Peak Torque 1760 (Oz-In) 1760.) that run up to 1700 rpm,

Should that be 0.2"? because 2" is heck of a high lead for a ball screw.
My Excello's are fitted with 26 inch-Lb stall torque DC motors with 2:1 timing belt reduction.
Al.

[2muchstuff]

What worries me is that 2" of travel per revolution, that's an awful lot of movement. At that amount of travel you would almost have to go with a 10:1 or 20:1 ratio to get any kind of decent resolution. At that amount of reduction you IPM speed would be awfully slow.

[roonster71]

yep i guess i need to learn to read my dial it was loose its .250 inches per rev

[2muchstuff]

That's much better. With a 1000 ppr encoder and a 2:1 reduction, that would give you a resolution of 8000 pulses per inch of travel. Now were cookin.

[roonster71]

thanks!! that the info i was looking for do you know of any good (inexpensive) places for timing belts and pully's ????

or any place for info on xlo mill's

thanx

[2muchstuff]

As for the mill, I am not familiar with that one. Timing belts and pulleys can be found at McMaster-Carr, W.W. Grainger and my favorite Stock Drive Products. Stock Drive has a very nice section on engineering data to help you design your drive. As for finding stuff inexpensive, I've been doing some searching myself as I'm needing the same stuff. Ebay has been a waste of time, yesterday-only 2 auctions for belts and 1 for a pulley. I have started searching metal scrap yards for them, found some stuff that has been close but not exactly what I was wanting, a lot of more yards to go thru though.

[Al_The_Man]

I have the mechanical parts manuals, and the last time I checked most mechanical parts are still available, I assume the retrofit on the 602 was Z axis on the quill? They had two types of knee, one was hand crank and the other powered for initial position only.
Al.

[Karl_T]

Looks like most of your queries are answerred.

I'll just mention I have the Excello 602. First with Ahha control and now with a Camsoft control. I used 2:1 reduction for servos 1:1 for steppers. Most parts from McMaster Carr

Its been a wonderful machine for me. Parts and manuals readily available from Excello in Michigan.

Karl

[Al_The_Man]

This one of the 602's I retrofitted.
Al