Sieg mini-mill CNC conversion

Conversion uses ubiquitous 5/8" ballscrews and ballnuts. However,
there should be enough off the beaten path that the hobbyist/
enthusiast may find interesting. A pictorial summary can be found
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I have always been interested in the conversion projects. Very interesting. The problem IMO is most conversions seem to be based around the smaller mills like that. Is it just because they are such an inexpensive mill?
I do like your motor mounts and how you kept the manual operation. Do you have an AC side switch so you can turn power off, move your machine, and then turn power back on without frying your controller with back current?

Reply to
Bob La Londe
I'm not finished, but did you follow the conversion of my Matsuura MC1000 VDC? The machine weighs in at 16,000 lb. Or my completed Mazak M4 lathe. It only wieghs about 9,000 lb.
Reply to
Karl Townsend
I did a servo conversion on a 150-Lb mini-mill, mostly as a demo to drag to shows. You can hit E-stop and move the machine manually, and then clear the E-stop and be back to CNC operation, without ever losing the coordinate reference.
It is an ugly hack, as I use it for a test bed of various ideas, motors, drives, etc. it even has rigid tapping capability. See
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Reply to
Jon Elson
Retaining full manual capability was a priority. Having to turn on computer (or wake from standby), log in and run the CNC software just to drill a hole or two makes no sense IMO. However, I'll have to get used to the small handwheel for the Z-axis.
I can either turn off the power supply or use a switch that connects/ disconnects power to the drives. Normally use the latter.
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Interesting and well documented -- within the limitations which the web site put on your own added text. I mean who cares about the camera (a nice one) or the EXIF data when you are documenting a project like this -- but you live with what the web site will allow. :-)
A question and a suggestion to follow -- both related to turning the ends of the ball screws:
1) Was it truly necessary to anneal the ends of the screws? I believe that they are only case hardened, so after a first heavy cut to get under the case, you should be fine. (Perhaps with the insert tooling you were using, you could not take that heavy a cut. I've used that style of insert tooling, and have long since abandoned them for the more industrial style with a carbide anvil under the inserts among other things.
2) Looking at the photo showing the teeth of the chuck jaw lining up with and resting on the crests of the ball screw thread, I suspect that the other two chuck jaws would be touching at non-optimum places, so what I would probably do (if I did not have collets large enough for the task), I would have taken some aluminum, mounted it in the chuck and marked the point in the middle of the #1 jaw, then bored it to barely clear the ball screw, then removed it from the chuck and slit it at a point midway between two chuck jaws (probably 180 degrees opposite the marking for the #1 jaw), then put it back in the chuck (using the mark to put it in the same position), so it would act as a reasonable collet and be less likely to damage the crests or flanks of the ball threads.
Good job, anyway. DoN.
Reply to
DoN. Nichols
The ballscrew manufacturer (Roton) recommends annealing for easier machining. Some posts recommend grinding off the hardened layer with a grinder (heaven forbid) and those with better carbide tooling recommend the same as you did. Interestingly, one fellow posted that a machine shop he approached declined to take on the job for lack of the proper tooling.
Agreed, those little triangle carbide inserts suck even for normal steel. Hardened steel would probably kill them in an instant. They're fine for alu, brass and soft metals IMO. Furthermore, my parting blades are all HSS so annealing it was. No biggie, I had the Benzomatic already (plumbing repairs).
Several posts on this too. Some recommend using collets and others recommend filling the grooves with aluminum or copper wire then treat the ballscrew as a normal shaft. I simply positioned the ballscrew carefully and had no runout or slipping issues even when using the die.
Thanks! And thanks for the advice. I really need to upgrade my lathe tooling.
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O.K. If they recommend it, that should be fine.
I suspect that I might have tried punching a hole in the roaster pans to pass the rod through, just to minimize radiation heating of the rest. I presume that the wrapping was soaked in a coolant of some sort to keep conducted heat down to a minimum.
That is interesting. I certainly would have found a way to do it myself. :-)
And the interesting thing is that while the holders are cheap enough in sets, the inserts (alone -- not in the sets) cost more than those for serious industrial tooling in my experience -- both based on prices from MSC. For most turning, I use the Aloris BXA 16N (negative-rake) double ended holder, and inserts with grooves such that while the holder is negative rake, the net effect is that of positive rake -- but I still get the ability to turn the inserts over for three more points, if I don't do something to chip them badly. :-)
In part, I suspect that this is because the shanks don't have the carbide anvils, so they can bend a little and no longer support the inserts solidly enough to prevent breaking.
Yes -- collets if you have them large enough and can handle through spindle diameters large enough for the workpiece. The aluminum or copper wire might work with chuck jaws which did not have those precisely spaced grooves. Aside from the makeshift collet which I described above (quoted), an alternative would be shims of aluminum between each jaw and the workpiece, likely with an 'L' bend in the end to let you stop them against the end of the jaws.
I got a lot of my inserts and insert tooling from eBay auctions back in the days when they had more of usable size (and did not insist that their vendors use PayPal). But I bought the Aloris BXA 16N *new* and have not regretted it. Perhaps an AXA-16N for your lathe, depending on the size.
Enjoy, DoN.
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DoN. Nichols

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