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Electronic Leadscrew for the New Lathe
vtsteam:
I just spent a discouraging evening looking up electronic leadscrews on the internet. They don't seem to work very well, and, they cost multi $, or both. Or they need a big computer, too. Any suggestions to get past both of those problems would be greatly appreciated!
I read that standalone units don't make sense, and that a supposedly DIY open source unpopulated standalone board costs $250.
I read that a full fledged CNC program can work (and actually, more cheaply, since I already have steppers, stepper drivers, and spare older computers with parallel ports).
BUT a computer and associated gear and wiring is practically the size footprint of the lathe.
BUT also the single pulse per revolution of the spindle in most stepper CNCs is NOT accurate.
BUT some say it is and the reason it isn't accurate is because Mach 3 has bugs in the threading portion of the code.
But TurboCNC has been used for threading for over a decade.
But is it accurate enough?
But LinuxCNC uses a quadrature signal besides the single pulse, so maybe it is acceptably accurate.
But GRBL a simple CNC program that can run with very simple compact computers like Raspberry Pi to control an Arduino has no lathe threading capability.
Most threads devoted to this kind of thing seem to deteriorate after the first two or three pages into arguments about closed loop and open loop theories and the number of pulses per revolution or inch, etc. and end up nowhere.
Here's what I'd like:
A small box that had a small display and a few buttons, that would hook to a sensor on the headstock, and to a driver for the stepper motor, and would allow you to enter the feed rate desired, direction, and if needed threading input requirements. That's all. And that there was a board available for doing that for about $100 or less.
Is there such a thing? My guess at least from reading so far, is no.
Yes?
Brass_Machine:
I did see something like that awhile back. It was essentially a cnc "lite".
I will see if I can find it again.
However, why not use an arduino and make your own?
Brass_Machine:
I can't understand what he is saying... but something like this? Arduino control...
bertie_bassett:
Ahh the good old ELS problem. I remember getting just as frustrated trying to find a simple solution.
What do you actually want it to do though??
Do you want it to do the whole threading job?? Or do you want to do the threading yourself and just have the speed controlled electronically ?
If you want to do it yourself, all you need to replicate electronically is the change gears, so a simple spped control circuit would be the main part, tie it to the headstock speed with a comparator and bobs your uncle! Then for threading either keep the half nuts engaged or use a thread dial.
If you want the electronics to do the whole job, then you'll need to have something keeping track or where everything is plus drive 2steppers, so then you getting into big enclosures with lots of parts. In fact you'll be jusst pn the edge of a full cnc machine.
Personally I'm going to go stick with change gears for now ( if i ever make any). And in the future have a simple speed controlled lead screw
lordedmond:
This may be a completely dumb question but
If you use the system as Bertie speced out you have to reverse the lathe , so with a single encoder pulse from the headstock how does the system know how to reverse the lead screw ?
In my mind a single pulse will give position but not direction , but I may be wrong again
Stuart
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