electronic lead screw

DoubleHelix

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Has anyone added Jog to their ELS setup? You wouldnt be able to do this while threading since it would not be synced but for just normal feed operations.
 

RJSakowski

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I tried using the enable input to my driver for end of travel. (electronic carriage stop) If the driver is enabled while the spindle is still turning, weird things happen with the feed rate. The lead screw might reverse or rotate with a speed different from that which has been set. Stopping the spindle before enabling the driver will return thing to normal. This is a driver issue and other drivers may behave differently.

If you are planning to use the driver enable to jog the lerad screw, use caution.
 

GunsOfNavarone

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I tried using the enable input to my driver for end of travel. (electronic carriage stop) If the driver is enabled while the spindle is still turning, weird things happen with the feed rate. The lead screw might reverse or rotate with a speed different from that which has been set. Stopping the spindle before enabling the driver will return thing to normal. This is a driver issue and other drivers may behave differently.

If you are planning to use the driver enable to jog the lerad screw, use caution.
Man RJ, you have a genius idea. Why wouldn't you be able to have some sort of limit switch? Perhaps in a magnet and place it where ever the thread operation ended or (more reasonably) where the feed ends for simple turning. I mean really, this is essentially CNC, why isn't it possible and super simple? You're saying, when you stopped the carriage moving forward, you had problems based on the spindle turning? Couldn't this some how be connected to a vfd to stop it as well? Why is it not an issue when using the ELS normally and stop at the end of a pass? Is the only way you can stop the carriage moving forward when threading is the run/stop switch? That's got to make if difficult where the threads end right up against the nut (with little to no gutter) I mean we still have the half nut, but stopping via the ELS would be great. Maybe 'll shoot Clough that question.
 

RJSakowski

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Man RJ, you have a genius idea. Why wouldn't you be able to have some sort of limit switch? Perhaps in a magnet and place it where ever the thread operation ended or (more reasonably) where the feed ends for simple turning. I mean really, this is essentially CNC, why isn't it possible and super simple? You're saying, when you stopped the carriage moving forward, you had problems based on the spindle turning? Couldn't this some how be connected to a vfd to stop it as well? Why is it not an issue when using the ELS normally and stop at the end of a pass? Is the only way you can stop the carriage moving forward when threading is the run/stop switch? That's got to make if difficult where the threads end right up against the nut (with little to no gutter) I mean we still have the half nut, but stopping via the ELS would be great. Maybe 'll shoot Clough that question.
My idea was to use a microswitch to disable the stepper driver which it did very reproducibly. When I disengaged the half nut and manually backed off the microswitch, the driver was again enabled but the stepper was now running in reverse. The driver apparently doesn't like being disabled while it is receiving step/direction signals. Even if it did work properly, it would be of no use for threading as disabling the driver is the electrical equivalent of disengaging the gear train. Synchronization is lost.

It does work for carriage feed though as synchronization is an issue. I run to the stop and and disengage the half nuts and then back the carriage off the stop. The lead screw starts in reverse and I trigger the stop again which starts it running in the forward direction. It weorkss but is really of little utility as when I am turning with power feed, I will disengage my half nuts before the end of travel and finish manually to the stop or to a DRO position.

I have a mechanism to disengage the half nuts using an electrical stop in the works. As things ease up,I'll be getting back to it and will publish it on HM at that time.
 

GunsOfNavarone

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Hmmm... Maybe a programming thing for James. If a micro switch could send a signal to run a patch that just reversed direction on a VFD, Or, since the spindle and lead screw are no longer mechanically connected, just immediately reversed the lead screw direction? There has got to be SOMETHING there. This is CNC pretty much after all.
What would happen if the micro switch reversed the VFD and left the ELS alone? What would the ELS do if the spindle changed direction fairly quickly?
What if the micro switch shut down receiving signal from encoder? (spindle)
Help me out here brother, you're far smarterer than me!
I have seen some of the half nut disengaging setups (that leave manual control) WAY too much work!
 

RJSakowski

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I don't have a VFD...yet. I'm working on that now. It is possible that Clough could work something into the code. It starts to get complicated though. Essentially, the code would have to recognize the trigger signasl, stop sending pulses to the driver but continue counting them and do some catch up later to restore synchronization.
 
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DoubleHelix

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Well from Clough's github it looks like it is in consideration:

Future Goals

While this project is starting out as a simple gearbox replacement, some features seem attractive, even for that simple case:
  • Threading/feeding up to a hard shoulder with automatic stop
  • Automatic recall and resync with hybrid threads (e.g. metric threads on an imperial leadscrew)
 

GunsOfNavarone

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Yeah, I sent him a question based on a convo with others here about the auto stop about a week ago. Of course no answer, but if enough around here post that on his ELS youtube comments, maybe that will reignite his interest.
 

DoubleHelix

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So far what I plan to try is a proximity sensor (copy of @mksj proximity sensor) connected to the VFD. This will stop the spindle, encoder will send steps and thus stop the ELS movement.

If you have the sensor stopping the ELS directly while spindle is still spinning then its a more complicated endeavour of syncing back up.
 

GunsOfNavarone

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@DoubleHelix what VFD are you using? During my build/install I came across something that I remember thinking I could use for such a thing (ELS wasn't even a thought at that point) I'll have to look that up again & post here. At say 60 RPM, the spindle could be stopped in a second.
 
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