[baseball43v3r]

hey all I recently purchased a 14" X 40" inch lathe, and i was looking at converting it into a cnc lathe.
Most of the pieces i plan to make are around 1/2" to 4" in diameter, and mostly out of maple, ash, pine, andoccasionally oak.

My main question revolves around the electronics, for a machine of this size and these types of projects, what would you guys recommend for a stepper motor? as it is i'm currently looking at the probotix 2 axis kits, but i'm unsure if they would provide enough power.

Also i've searched on here, and also throughout the web on google, trying to find large size lathe conversion projects to see what other people are doing but to no avail. everything i see is for lathes around 8 or 12 inches, but nothing in the 30" plus range.

Thank you for your time and input!

[andy55]

how much money do you want to spend? Do you have experience with stepper-motors from previous projects? Are you fitting the machine with ballscrews?
Brushless servos and drives are cheaper than ever before and I would suggest you look at them, the performance is usually miles beyond any stepper motor solution.
NEMA34 size servos of around 500W would probably work.

[baseball43v3r]

hey andy thanks for the reply!
in answer to your questions:
1) on the electronics, i've got a smaller budget, only 200-350 dollars. ya i know its a minimal budget, but i'm trying to make due with what i can.
2) my experience from stepper motors comes from one or two previous school projects where i have enough experience to be comfortable with them but i wouldn't consider myself an expert or advanced by any means.
3) as for ball screws, i'm still toying with that one. I will settle for very very close accuracy on this machine, but it doesn't need to be perfect.

I have not read very much about servos but i will look later tonight, i know they have a very high accuracy, but if they are cheaper now, why aren't more people using them for mills? Also i know that W = V * A, but the sights i'm looking at for stepper motors have them listed in oz-in like steppers, and the converted numbers when i do their V*A does not add up. As i don't know very much about servo's can you provide a little more insight about them? and how to compare their power to steppers?

[andy55]

steppers want to be run at low rpm, they loose all torque above some critical rpm, look at the datasheet. You probably want to directly couple the steppers to your lead-screw for this reason. Good axis-couplers can cost a bit...

Servos want to be run at high rpm, they will have the same torque up to the rated rpm which is usually 3000rpm or 4000rpm. That is much too fast for your lead-screw, so they are usually geared down 1:2 or 1:3 which allows for very quick accelerations and decelerations on the machine.

with your budget it seems a set of 3 geckodrives, a powersupply, and three steppers (get the most holding torque you can afford) should be the plan.

servos are more expensive and would "deserve" ballscrews, fancier controllers, etc.

[oreos40]

if it is a metal lathe make sure your headstock does not have Babbitt bearings they wont take the speed. If your planning on production and not something just cool to watch you will want to get the speed up and use machine tool type cutters. if you are turning with a router in the cross feed you will want it to go slow rpms but it takes a long time to make a part.I don't know if your lathe has both a power carriage feed and a lead screw but for wood the lead screw tends to wear quickly. when you lube it the dust sticks to it and when you don't the half nuts wear, so the best would be to use the power carriage feed if it is a wood lathe you have some work to do for the carriage and cross feed. It doesn't take much force to run the cross feed section. the longitudinal could be set up with a roller chain and reduction.

[cabnet636]

i added a lathe to the side of my camaster x3.

[ame="http://www.youtube.com/watch?v=giYiUTpm_LE"]YouTube- x3 rotary movie 0001[/ame]

jim