Adding steppers to LC-30 mill: direct or belt drive?

[slow-poke]

As the title states, the steppers are 900 oz-in, speed is not a primary concern, having enough torque is my main concern. I also think it might be easier to implement with a short clogged belt with the motors just to the side of the hand cranks. I would imagine I can get a 2:1 (or better) increase in torque with a belt system.

If anyone has implemented CNC on a Long Chang mill I would really like to see how the conversion was done?

 

[Eddyde]

I have a Mill made by Long Chang, it was marketed as RB-1 (LC 50) by a Swiss company Siber Hegner. They were also sold under the brand name "First". I am currently working to CNC it, albeit slowly... I went with servos, 1125 oz in. I haven't mounted them yet but they seem plenty strong for the task, I had researched the motor needed for CNC-ing a Bridgeport and that size was the upper range what was suggested. What are the specs of your mill, Do you have any pictures?
Here's a link to when I got my mill for reference: http://www.hobby-machinist.com/threads/new-siber-hegner-rb-1-milling-machine.37875/

 

[slow-poke]

Picture of my smaller, cheaper, older LC-30 Mill

 

[RJSakowski]

I would use direct drive. Any additional components added to a drive train add backlash and/or lost motion.

 

[RJSakowski]

My Tormach 770 has 500 oz-in steppers and more than enough torque to do serious damage in a crash. If you feel you need mechanical advantage, on way would be to use a lower pitch lead/ball screw. The 770 ball screw has a 4mm pitch.

 

[Eddyde]

Picture of my smaller, cheaper, older LC-30 Mill

Looks like a nice mill, I know Long Chang make quality machines. I agree with RJ, your steppers should be plenty powerful even in direct drive, However, you may want to do a pulley timing belt arrangement to get the motor(s) out of the way, I don't think you'll add much if any backlash.

 

[slow-poke]

Looks like a nice mill, I know Long Chang make quality machines. I agree with RJ, your steppers should be plenty powerful even in direct drive, However, you may want to do a pulley timing belt arrangement to get the motor(s) out of the way, I don't think you'll add much if any backlash.

That's what I was thinking, also a belt arrangement is more forgiving for slight errors in alignment. Apparently UPS has lost my package (steppers), so when they do finally arrive, I will size up how I will mount them. Fun project!