Re: [CAD_CAM_EDM_DRO] Build my own CNC lathe - possible?

Well Alan we may have a few things incommon other than first names.I'm also in California San Jose)I've been designing my own desktop cnc mill for a few years now,I have a couple of versions of it.I have some parts set aside for a lath as well however I haven't even looked into starting that project yet.Not untile I finish these mills
I'm auctualy not a machinist ,however I've almost finished the machining program at San Jose City College,I'm normay a sr electronics technician.And having said was to explain where all my parts came from.here in silicon valley there used to be a real world class mechinial "junk shop"  everthing under the sun in cnc was avaible, so I ah "stocked up"  like most hording hermits do.So even throuh that place is gone I still have alot to work with I even have some in excess,for trade ofcourse.
My project has auctualy been a very long term project(20 years) and now at school I'm pulling it all together..The  mill should hold a thou on all three axis auctualy one of the machine may auctualy be a five axis when complete.I use linear encoders and ballscrews and the slides are some sort of roller bearing ways if you will.One unit I have the z axis running on three parallel shafts with the ball screw in the center.That unit the spindel is auctualy cable driven with the moter some two feet away.The other mill uses a stainless steel tube with  three magnetic donuts inside the tube and three motor donuts on the outside.These are neodibium magnets extreamly powerful. so it rides on a magnetic flux .Both of these systems are not my invetion , as they are products of silicon valleys r&d efforts into wafer handers and the like.Well enough said.
Alan Howard(San Jose,Cal.)




________________________________
From: Alan Rothenbush <alan@...>
To: CAD <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sun, April 11, 2010 11:40:30 AM
Subject: [CAD_CAM_EDM_DRO] Build my own CNC lathe - possible?

 

Lazy Sunday morning, drinking coffee, daydreaming and a crazy plan starting to coalesce.

1. I've CNC'd my old Sherline lathe and have been playing with it in earnest, to get my head around the use of a CNC lathe. (Long time user of a CNC'd mill).

This pretty cool!

I took the trouble of adding manual handwheels to it (just in case) but I can see that a nice MPG will completely obviate the need for these.

Problem is, there's some backlash in the system and due to the age of the Sherline, it's not easily removed. (Uses the OLD style leadscrew nuts). I'm compensating in software, but of course that's not the same thing.

Still, a CNC lathe is cool.

2. My primary lathe is an old Southbend 9" x 18" that's a bit of a Frankenlathe; bed, headstock, saddle and tailstock are all from different machines. It still turns out pretty good pieces, I think, but there's a TINY bit of taper and a TINY bit of roughness in the turning, a bit more play in the nuts than I'm happy with, bit of wear in the cross slide, a slightly sloppy tailstock and so on.

None of the faults are show stopping, but there's enough of them that I've gotten it into my head that I want something better, plain and simple; something NICE, and preferably new or nearly so.

Now, it's about the biggest machine that will fit my space and it will do 99% of what I typically turn, so I REALLY don't want to contemplate anything bigger.

Looking around, though, for "new" and "nice" in a benchtop of that size, the pickin's are slim; really, all I see is a Prazi D6000 for $6500.00 That's really outside my price range as a hobbyist.

3. Whatever I buy, I'd have to CNC; no question. I'm hooked. So even if I did talk myself into $7k (adding in taxes and whatnot), do I really want to start drilling holes in a brand new machine? Probably not; I'm not that brave.

4. Staring at the McMaster Carr online site and peeking at eBay, I keep looking at all these linear rails and I've got to wonder; couldn't a guy build his own CNC lathe for a WHOLE lot less?

Some stout linear rails fastened to a suitable base (the ground flat bed of an old lathe, for example). Standard linear slide for the cross slide. Ball screws.

Use an existing spindle out of something, maybe even another Southbend so all the existing attachments can be reused.

Fab up a headstock and line bore it right on the machine itself; same thing for a tailstock.

Sunday morning on the couch, this SEEMS doable. Am I dreaming? Hallucinating? Any opinions (including "you're nuts") appreciated.

Alan






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