LinuxCNC as ELS for lathe?

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4 years 4 months ago #244770 by Markyd
Rather than a full cnc conversion of my Colchester Bantan I'd like to try a Electronic lead screw conversion, possibly as a first step to full cnc.  Ive mounted a belt driven rotary encoder to the spindle and have an RPI4 and 7i96 (ethernet).  Is there an easily configurable way of using linuxcnc for this Or? Or am I best off building something bespoke with a microcontroller (based on clough42's ELS or similar)?

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4 years 4 months ago #244780 by tommylight
Can you please explain to me what does "Electronic lead screw" mean or what it does?
Thank you.
P.S.
Not helping, but i saw this many times on youtube by Clough, but i never watched any of it as i got tired of having that suggested to me about 40 times a day, 10 or 15 or 20 videos from him about this same subject. I did watch some other videos from him though, but not related to ELS as, if it is a controlled motion of a lead screw, why not CNC? There are only 2 screws ...
So my point of view was "to much fanfare for nothing".
I would like to be proven wrong, though.

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4 years 4 months ago #244784 by spumco
Replied by spumco on topic LinuxCNC as ELS for lathe?
Tommy,

An electronic lead screw is just that - it's a normal manual lathe leadscrew, coupled to the carriage with a standard half-nut.  The difference is that instead of being locked to the spindle through a set of change gears or a q/c box, it's driven by a servo or stepper.

There is no motor or anything else coupled to the top slide or compound.  Those are still fully manual.

The "electronic" part is three components - a spindle encoder, a microcontroller, and a servo/stepper drive.  The controller takes the spindle encoder pulses and converts them to a S&D signal the (new) leadscrew motor.

The magic trick is a simple user interface which permits you to select a particular electronic gear ratio between the spindle and leadscrew.

For a grown-up industrial (or serious hobby) lathe with a q/c gearbox that has both a leadscrew as well as a shaft-driven power feed, an ELS is generally a waste of time.

However, for small hobby lathes which are typically driven only by a leadscrew and may still have individual change-gears, an ELS is a godsend.  Imagine having to switch out gears just to go from a roughing to finishing chipload?  Very time consuming and annoying.

Further, these lathes usually require an even more lengthy swap between metric and imperial feeds for threading.  What if you're missing a gear - how do you cut a particular thread?

Depending on the complexity of the microcontroller software you may even be able to set a feed-per-rev rather than a specific ratio - the ELS does the math for you.  Just program it (usually a simplistic GUI or dedicated buttons), engage the half nuts, and away you go.

In addition, a true servo may be able to stop (or reduce) crashes if there is a torque overload sensor.

On one hand, you could ask what's the point? Why not just CNC the thing?  The answer is - no significant hardware changes, very low cost (compared to a full X/Z retrofit with ballscrews), and very easy interface.  No new 'language' to learn, no program to write.

If all you have is a small lathe that is annoying to use, an ELS can be a game-changer.

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4 years 4 months ago #244785 by JohnnyCNC
I think LinuxCNC is way overkill if you just want ELS functionality and would probably be more work than building a dedicated ELS. But I am sure it could be done. I built the Clough42 ELS for my 8x12 Lathe just so I could eliminate the change gears. It works great.

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4 years 4 months ago #244786 by tommylight

For a grown-up industrial (or serious hobby) lathe with a q/c gearbox that has both a leadscrew as well as a shaft-driven power feed, an ELS is generally a waste of time.

However, for small hobby lathes which are typically driven only by a leadscrew and may still have individual change-gears, an ELS is a godsend.  Imagine having to switch out gears just to go from a roughing to finishing chipload?  Very time consuming and annoying.
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On one hand, you could ask what's the point? Why not just CNC the thing?  The answer is - no significant hardware changes, very low cost (compared to a full X/Z retrofit with ballscrews), and very easy interface.  No new 'language' to learn, no program to write.

If all you have is a small lathe that is annoying to use, an ELS can be a game-changer.
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That explains a lot, thank you.
Having had a small and still having a bigger lathe, i see the point, i never changed gears on the small one as it took half an hour, but i consistently change gears on the big one. Do not get any ideas, i use those about twice a year! :)
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Thank you.

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4 years 4 months ago #244793 by Markyd
Replied by Markyd on topic LinuxCNC as ELS for lathe?
Exactly as Spumco says. My Bantam is Metric and has what I'd say is a very good threading gearbox, for metric threads. Unfortunately a seem to cut almost as many Imperial threads as metric, including Whitworth (and the odball 12tpi for 1/2"), at which point changing the change wheels is a pain (accepting that everything is relative). I will ultimately do the full CNC conversion, which is why i have a 2nd 7i96 (my first being on my mill).

Based on the responses above it sounds like there's no simple way of using Linuxcnc for this purpose?

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4 years 4 months ago #244800 by spumco
Replied by spumco on topic LinuxCNC as ELS for lathe?
I'm not an expert by any stretch in LCNC, but I can think of a couple ways of using LCNC for this.  But a dedicated ELS is likely simpler, assuming you can borrow someone else's design and microcontroller program.

And creating a user interface for LCNC will be a challenge if you've never done a GUI before.

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4 years 4 months ago #244803 by Todd Zuercher
Considering the only difference between doing an ELS and full CNC control in Linuxcnc is one stepmotor. What's the point of only doing it half way?

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4 years 4 months ago #244804 by spumco
Replied by spumco on topic LinuxCNC as ELS for lathe?
Perhaps someone simply wants a manual lathe and not a CNC lathe, but they want the ability to cut many different threads or feed-rates.

I think of them as enhancing a manual lathe rather than being a half-a$$ CNC lathe.  Like a power down-feed on a mill quill - not necessary, but makes a huge difference in user experience.

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4 years 4 months ago #244810 by Todd Zuercher
Just because you add cnc capability doesn't mean it has to loose the ability to be used manually.

I certainly would want to keep manual capabilities on a lathe, if I were ever to convert one.

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