Piggyback CNC Lathe Add On

[lerman]

I have this perfectly good 14 x 30 lathe sitting in the shop, but I sure would like to have a CNC lathe for some of the parts I'm making. A 3 x 6 lathe would be fine for most of them.

Converting the lathe would probably require a lot of time and effort, and would be hard to do without taking it out of service.

So, I had this thought. Why not build an XY (or XZ, I guess) CNC table that is bolted onto the top of the existing cross slide? I would add an encoder (or perhaps just an index) to the spindle and use a VFD drive. To use it as a CNC machine, just bolt on the table, set the cross slide to the proper position and lock it in place, zero the CNC, and I'd be in business with my small CNC lathe. I would consider making both X and Z feeds about 12 inches long and plan on using gang tooling with it.

Since the CNC work I'd be doing is mainly aluminum and brass, I would probably make this assembly fairly light.

Any comments or thoughts?

(Is this posting in the wrong place? I don't think it really qualifies as a project log yet.)

Ken

[lerman]

To follow up on my own post, mechanically, something like:

http://www.omniturn.com/bin/Attachme...ifications.htm

seems about right.

Ken

[Adobe Machine]

Do you have enough space from the top of the cross slide to stack a Z axis, an X axis and some type of tool holder , that will allow tooling at centerpoint ? Even with small ball screws, you have ball nuts, flanges , radial thrust bearings and housings, plus your servos or steppers and their connections. Even making it "light" you must calculate the amount of force needed to engage the tooling at a decent DOC with out moving everything away from the cut etc...Could you draw your idea up and post ? There are some really good brains on this forum who could help you decide weather to go ahead with such a project, which ,from a mechanical stand point, is going to be a real complicated endevor....just a real challenge..but maybe some fun and rewarding for you !

Adobe (old as dirt )

[NC Cams]

Packaging would be the fly in this idea's ointment.

Yes you could get an X-Y table to work but at what price would swing loss be???

Lathe retrofits are not easy to begin with, ESPECIALLY, if you want to do threading. You could probably affix steppers to your manual lathe where appropriate and end up with a much more versatile system than what you propose. Mach would probably be the least cost, most viable DIY system.

If you can not afford to take the lathe out of service due to production demands, you might NOT want to try doing a DIY retrofit. Retrofits gobble up copious quantities of time and money that you'll be unable to recover the loss from in a production environment.

Somethings are better of being bought as a package than being kluged together in a make-do fashion. BTDT and wouldn't go there again.

[miljnor]

Something’s are better of being bought as a package than being kluged together in a make-do fashion. BTDT and wouldn't go there again.

A truer statement was never typed!

On the flip side some people have great luck putting a DIY system together and get it running.

It mainly depends on how much time your willing to throw at a project both before and after the initial start. And how much aptitude you have changing your design on the fly. And most importantly: having realistic expectations of the outcome.

The last one is where most people go wrong. You have to have very realistic expectations. Your probably not going to have anything remotely close to a Commercial grade machine. Either it will break allot or the tolerance will be dicey. I am not saying you couldn't build something better than what is sold commercially but its not likely as your trying to save money most of the time you do things like this, and lets face it commercial vendors throw huge amounts at R&D.

My reasons for this type of project are:
1. I work on most of my stuff already and something I can put together myself makes it easier to diagnose do to familiarity with the machine.

2. I know what I can get away with on slop (if any)

3. I mostly only build hobby machines (wouldn't hold up in production environment)

4. Willing to re-engineer everything multiple times until its the way I want it.

The last one is where most people lose there steam. If your think your going to get it worked in one iteration, think again and get a pro to do it.

And lastely some machines are MUCH easier to retrofit than others. You should look for others that have done similar machines. I put a stepper system on a 9x7 Harbour freight unit took about 2 hours and has been working great since then. But the software and my expectations took alot of adjustemenst.

Have fun.