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Electronic Leadscrew for the New Lathe
Country Bubba:
--- Quote from: vtsteam on March 28, 2015, 01:19:49 PM ---When all is said and done and we get a small computer board and a screen and a keyboard and lets say we're going to run DOS and TurboCNC....... seems like some old funky 486 DX66 laptop with a small screen and therefore a small footprint is actually going to be more compact than all the other separate micro stuff hooked together with a power supply and cables, etc.
And I don't know why I hadn't thought of it, but I do have an old Win95 NEC 486 DX66 laptop, that will run DOS on startup, actually in quite good condition stuffed away somewhere "in case I ever found a use for it".
The only question is, John S. Is TurboCNC single pulse pickup threading no good, or probably okay for a bodger like me?
ps There's a business in Vermont???
--- End quote ---
Steve,
Look at the Dakeng web site and the piece that Dave K is making for a sonar part (video at http://www.dakeng.com/TurboCNC_four_tools_turning.AVI)
Yep, turbocnc ain't dead yet!
vtsteam:
Thanks Pekka, that was interesting reading. :beer:
Norman, yes I guess a QC gearbox could be made. There was an article in May 16 1980 ME by S.H. Abigail for a really simple conversion from loose change gears that I saved and looked at for quite awhile -- thinking of doing something similar for the Craftsman 12x36. But I never did. I should still keep it in mind. But I'd have to make up a full set of gears for the new lathe, which means making up a dividing rig, etc. I suppose one way of simple dividing would be to use the set of change gears from the Craftsman to index a cutter to make the new gears with.
Bubba, I have a fondness for TurboCad, and I actually still use it on the hot wire foam cutter. That video is cool, but it was running so fast I finally realized when I looked at the swarf that he was cutting plastic, not steel. I've used LinuxCNC on my router. Both of these are in my big shop, where there is more room for a computer and other necessary gear.
One more thought re. electronic leadscrew and a micro single board computer running the GRBL CNC program:
GRBL does not do threading -- no input for pulse or encoder
But it does do conventional axis stepping. What if you could temporarily disengage the normal spindle motor by loosening the belt, and have another sheave with a timing belt to a stepper. Then you could just treat the spindle as just another machine axis, and since thread cutting speeds are likely to be low, and reduction to the stepper can be a reasonable amount, seems like you could just sync the spindle and leadscrew that way. Then cutting and multiple passes are all doable depending on how you write your G-code.
Similar idea I've already seen where both the spindle and leadscrew are servos, but a stepper version....
Fergus OMore:
Yes, but the late and much lamented Cleeve only utilised enough cogs to make the necessary threads. I've got a heap of cogs tied up and have never been used and will never be used-- and this is a 'sight glass' Myford Super7B that Hiram Abiff made the brass pillars for Solomon's Temple( or very nearly) .Again, I've a heap of cogs for the time that I might rip it all out and fit a longer leadscrew. If I ever get everlasting life!
Seriously, apart from cutting a 1/2" BSW thread or a fine feed, that is about it. I only cut 16TPI because I'm not strong enough now to to manually tap.
Writing as retired bean counter, having a Myford box is a better investment than having my hard earned brass in the bank.
But enough of the Ancient dis-Order of Myford Investers? What about the old Pools Major lathe? I had one- sadly worn out and past its best but it had TWO leadscrews! It simply tightened or slackened the screws for the cogs to engage or disengage. Mine had flat belts and was often archaic but these nice little touches were winners.
Electronic lathes or whatever? No, they will come for the model maker and be affordable but not in my time. Meantime, others will spend a lot of time and money in development( and often failure).
Maybe you should make a Hozapffel with your initials cast in the legs and a wardrobe full of homemade tools!
My kind regards
Norman
philf:
--- Quote from: vtsteam on March 28, 2015, 11:05:55 PM ---
But it does do conventional axis stepping. What if you could temporarily disengage the normal spindle motor by loosening the belt, and have another sheave with a timing belt to a stepper. Then you could just treat the spindle as just another machine axis, and since thread cutting speeds are likely to be low, and reduction to the stepper can be a reasonable amount, seems like you could just sync the spindle and leadscrew that way. Then cutting and multiple passes are all doable depending on how you write your G-code.
Similar idea I've already seen where both the spindle and leadscrew are servos, but a stepper version....
--- End quote ---
Good idea Steve,
You'd need a fairly powerful stepper to drive the spindle and/or a big (compound?) reduction ratio to provide enough torque for coarse threading.
Phil.
RussellT:
Hi Steve
Having read all the responses it seems it's possible to do it electronically but it's not straightforward or it's expensive.
Constructing a quick change gearbox seems like a lot of work too.
I bought a gearbox for my lathe because I didn't like changing the wheels to switch from threadcutting to fine feed - which is one of the reasons you mention and I'd find myself trying to avoid threading because of it.
If you're building a lathe from scratch then perhaps the easiest solution would be to have two lead screws - or two gear trains - one for fine feed and one for threading and rely on changewheels for setting the thread. Maybe you could even use the Craftsman change wheels.
Russell
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