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Electronic Leadscrew for the New Lathe
PekkaNF:
Aah Forth...When I was a school this was cutting edge. Every processor of it:
http://www.cpushack.com/2013/02/21/charles-moore-forth-stack-processors/
I remember one (least some part of) Norvegian team that was trying to make FORTH-processor for graphics application, bit slices were driven out of everything else than esoteric radar and such signal cruching. And finally out of that too with when signal processors started to appear. With PC:s I lost all interest on computers. Just too many layers of junk.
One more word: Harris. Never used one of those, but some later processors were very much influenced on those designs and ideas.
http://en.wikipedia.org/wiki/RTX2010
Pekka
vtsteam:
Guess I better resurrect this ancient thread and try to refresh my memory on what I'd done, if I'm going to use this. 3 years, sheesh!
vtsteam:
Okay looking back at he old spreadsheet I see I kind of lucked out on the new lathe. I just this week made a set of pulleys for it and I coincidentally gave them an exact 5 to 1 ratio. I did that at the time mainly because 18T and 90T were good do-able numbers for indexing on my old spin collet, and I lack a dividing head. And because 5 to 1 was in the range of a good reduction ratio for the specs of the treadmill motor I had. To have both of those things work out to exactly 5 to 1 was true dumb luck for me.
Why? Because I hadn't looked at this old electronic lead screw thread. And looking at it now I'm reminded that 5 to 1 is THE absolutely ideal ratio to make this work. Because what it means is that I can attach the 600 line encoder I already have directly to the DC motor and that gives me 3000 lines per rotation at the spindle. The DC motor has an extension shaft on the back end, for very easy attachment.
Looking at the lead screw, the ratio of the stepper motor and lead screw will be 1.5 to 1, that means (with a 200 step motor) the 300 steps per lead screw rotation on a 10 TPI screw yields 3000 steps per inch, super-convenient for the 3000 pulse per turn signal from the spindle.
And that means that simple integer division by the intended TPI will yield the proper pulse rate for the stepper to produce that TPI. Divide encoder pulses by 4, you get a 4 TPI screw. Divide by 28, you get a 28 TPI screw. etc.
This doesn't even require an Arduino to accomplish. It can be done with perhaps two discreet IC's. Maybe something in the 74LS161 series chained ( I have some). I think that's going to be my approach. If that doesn't work I can always fall back on the programmed Arduino I had already developed 3 years ago in this thread. But even an SBC is overkill, oversized, and slow and complicated by comparison.
Actually even one modern IC might work -- I don't know what's available these days. Basically I need a divide by N circuit with a max divisor of say 56 (for 56 TPI, or fine feed).
awemawson:
Sometimes the toast falls butter side up :thumbup:
vtsteam:
Glad I didn't own a dividing head!
I do need to read my own plan A before embarking on B sometimes.
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