Hi guys, I've decided that I need to be able to do lathe ops occasionally, but I can't really justify the space or expense of buying and CNC converting a lathe.
I have therefore decided to mount a lathe headstock and motor on my mill's table, and mount lathe tools on the side of my mill's head - I think this should give me basic turning and boring functionality under CNC.
So far, I have: Mini-Lathe headstock (from LittleMachineShop.com)
Mini-Lathe compound slide & tool post
Servo motor and Gecko on its way.
I am thinking that I am going to need a mini-lathe tail-stock as well, and a 'starter' set of cutting tools - is there anything else that I need to get started?
If I buy a standalone lathe, however small, I will still have to go through the extra expense of adding steppers/servos and motor mounts etc to it to get CNC. If I use my mill for X and Y/Z then the CNC part is free.
I also already have 1/3 of a lathe sitting on my desk...
You would think it should be this easy wouldn't you.
In the world of VMCs we spend MANY thousands of dollars for special driver boards that allow us to rigid tap.
I think the biggest issue with tapping is keeping the sync during decel and acel when reversing.
If you run constant speed/feed with a tach on the lathe RPM you may be able to thread acceptably.
I would think the threading less problematic then tapping for just the reason you mention DareBee, reversing.
The math is simple enough for this, (Precise) RPM X thread Pitch = Feed Rate.
It should be doable.
Some controllers I believe round up fractional feed rates, this may be a problem.
Pitch = .035714
RPM = 1500
Feed = 53.571
In practice I'm not sure how much difference a increase of .429 in the feed rate would make.
Some of you math whizzes figure it up in distance. I have not had my full pot of coffee yet
Don't forget you can thread mill as well. Mach 3 does do thread milling, but whether you can get it to properly treat your lathe spindle as a C axis remains an open question from what I"ve seen. It does not do rigid tapping, for example. Also, Mach lathe support has lagged mill support considerably, especially for the newer devices such as GRex. Art has promised to invest a bit of time near term improving Mach 3 Turn. You might want to pop over to that board and inquire about how to do what you want to do.
There once was a video of a mill being used as a lathe to make bushings. I've lost track of it, but it was a clever idea. This fellow used the mill's spindle as a lathe spindle, and the table as a lathe gang tooling plate. He had mounted toolholders all around the center, so he could approach the workpiece from a couple of directions to make the parts.
I was reading an old thread the other night and saw this intriguing setup by CNCZone contributor Geof:
He needed to face those 8 aluminum bars to length and drill and tap each end. He says this setup on a 4-axis mill will do the job faster than a CNC lathe. That got my attention. I thought about it, and the answer has to be because he had to drill and tap both ends of the rods. In a lathe that would require manually swapping the rod end for end (unless you have a fancy multi-spindle machine!) and in this setup it all gets done auto-magically.
That video of a mill making lathe bushings and Geof's idea for machining bars really opened my eyes to what some creative out of the box thinking can do.
Just so you don't think I'm a total mill bigot and hate lathes, I read another fellow who had improved productivity by using his lathe with bar feeder to act as a precision cutoff machine. He was just facing and chopping bar to length in order to make blocks to feed his mill. Said it worked out very well for him.
I have a 9x lathe and cnc'd x3 mill but also have a spare 7x headstock and tailstock I have been trying to figure out what to do with. Thought about using it as a second higher speed spindle for my x3, maybe a horizontal spindle or even as a lathe on the mill like you are talking about.
Keep us updated with your project!
Cheers guys - I haven't had much time to work on this yet - been madly building my new enclosure before I am inundated with 100's of lbs of extrusions, ballscrews and aluminium plate for my new mill+lathe project.
I suspect the lathe will be one of the last bits I get going, but I need to order a tail stock and some basic lathe tools tomorrow so that I'll have all the bits when the time comes.
I hadn't really thought hard enough about the software side of it - I was thinking that for boring and facing, I could just write some snippets of G-code , but I haven't really looked at how Mach 3 deals with spindle speed control.