[Bird_E]

Hello all,
I'm looking to get started in CNC I would like to convert my Mill and need a little guidance! So far this is what I have.

1. A New Sieg X3 Milling machine (a bit bigger the the mini mills)
2. A new HF 9X20 Lathe
3. An RF-20/25 Mill/Drill Clone

I have basic machining experience and a good deal of Electronics and PC experience.

I don't want to spend a fortune but I do wan't decent performance.. Ok isn't this true for most of us!

My questions:

1. What machine should I convert the X-3 or the Older Mill/Drill?
I prefer the Mill/Drill because "IF" something doesn't go as planned At least I haven't butchered up my New X3! But I think the X-3 would be a better candidate because of its square column and the Z axis would be easier to convert in my Opinion. But I'm open to suggestions.


2. What size stepper motors would I need to get nice performace? I have NO CLUE! Or should I consider servo motors (too expensive?) and if so what size?

What should be my first steps in the conversion? the electronics and power supply?, the motors and mounts?, Ball screws? (do I need them?

THanks!
Bob

[Swede]

Bob, there are so many choices and variables here, it's scary. Ultimately you must mesh your budget with your goals, and understand that with a limited budget, your speed and accuracy goals may not be met. So in many cases compromise is the name of the game.

I was not familiar with the X3 machine until I looked at some pics on a site. It looks fairly capable, but the head mass appears significant, even counterbalanced with a gas spring. Getting tight, accurate Z I think will require you to forego the stock feed and install perhaps a Z ballscrew.

Some options...
Cheapest: Fit adequate steppers in place of the handles, use stock screws. You must now deal with backlash, high forces, and fairly high torque requirement.

Medium: Replace stock screws with 5/8" or 3/4" Thomson-type rolled ballscrews and anti-backlash nuts. Torque requirement will drop, steppers may be pushed a bit faster, accuracy improves. Drawback - cost and time to machine the ballscrews and install decent bearings to keep the screws axially fixed.

High-end - Servos and high-grade ballscrews. Big $$, lots of time.

If it were me (just an opinion) I'd go for the X3 and convert it on the cheap in such a way that I could restore the machine later to manual. This would mean executing the "cheap" conversion described above, using the stock screws. If you feel adventurous and have a lathe or access to one, the medium approach with rolled ballscrews would be nice, especially since you can still, after the screws are in, restore the machine to manual, better and more accurate than it was, simply leaving the ballscrews in place. Thomson 5/8" rolled screws can probably be done for $100/axis using surplus BB.

There are others on this board with more experience than me who hopefully will chime in! Good luck!

[Bird_E]

Swede,
Thanks for the quick reply!

I'm going to opt for the "Cheaper" option along with ball screw converions. Seeing that I do have a 9x20 I do have access to the available tools in order to do the converion.

What would you recommend as an ideal stepper torq for the x3 or a Mill/Drill?

I can find 600-700oz stepper that should fall within budget, would this be too small or over kill?

A note on the X3 Z-axis there is a gas spring in the z axis column that balances the head mass nicely. The Z handle turns almost as easily as the X or Y!


Thanks Again!
Bob

[NeoMoses]

600-700 oz-in is much larger than most guys use for steppers, but since this is a milling machine and not a wood router, I don't think it's overkill.

My best advice is to set your budget first, then start designing your system. Without a budget cap, there are too many options. As far as the order of operations, I would recommend setting the budget, then determining drive motors you'll be using, then design the drive system to get the speeds and forces you expect to be using.