Dipping my toes into turning

[Advil]

(Accidental post)

 

[WobblyHand]

Well, of course, if you knew all that, and could enter it into the ELS, it could compensate, but the Clough42 ELS is not set up to do that math. Looking at the over-threading, my guess is that this is still an issue related to disengaging the half-nut and trying to re-engage it at the proper time and place. He's using the ELS that James Clough designed, and James goes into what's required to do metric threading with his ELS in glorious detail in the video at the following link. It's not straight forward given that he has an imperial lead screw and trying to cut metric, but it is possible to be successful disengaging and re-engaging the half nut if strict procedures are followed. Personally, I would find it a lot easier to just leave the half-nut engaged and back out of the operation for the next pass even with this ELS.

Let's ask the OP - were you disengaging and re-engaging the half-nut between passes?

I wrote my own ELS software from first principals. My DRO is integrated into the ELS. However, I have yet to implement thread to a shoulder, but it's on my agenda to do so.

I do agree with you that it would be easier in the Clough42 implementation to leave the half nut engaged. I don't think Jame's implementation has sufficient inputs to automatically do metric threads correctly (and use the half nuts like in imperial threading).

It really does look like disengaging and re-engaging was done. That was my initial guess.

 

[koenbro]

I am not disengaging the half nut.

The way one threads with the Clough fork, is to go the shoulder, engage the halfnut and the half nuts remain engaged for the duration of the operation. Select the shoulder position, then move to the start point, select that one and then start the lathe. Just to clarify, threading to a shoulder feature is not part of the original Clough software, that is why one has to use kwackers' fork. I think I'll make a video.

 

[Huub Buis]

According to the kwackers/electronic-leadscrew project:
It can support metric threads:

Allows the setting of custom thread pitches from 0.01mm to 9.99mm.

You do need to keep the half nuts closed:

If you haven't already engage the half nuts - they MUST now remain engaged for the duration of the threading operation.

You do not disengage the lead screw so maybe your encoder (index) pulses are "noisy". The real way to check this is using an oscilloscope.

 

[WobblyHand]

I am not disengaging the half nut.

The way one threads with the Clough fork, is to go the shoulder, engage the halfnut, select the shoulder position, then move to the start point, select that one and then start the lathe. Just to clarify, threading to a shoulder feature is not part of the original Clough software, that is why on has to use kwackers' fork. I think I'll make a video.

Thanks for the clarification. As a guess, there's either a miscount of steps, or a slip of the stepper. Are you using an open or closed loop stepper (or servo)?

Edit: could also be lead screw backlash

 

[koenbro]

The motor is a “servo” more correctly a fancy stepper the Teknic ClearPath and is good quality. https://teknic.com/products/clearpath-brushless-dc-servo-motors/

I suspect it’s the gearbox. Probably the hardest to correct.

Sent from my iPhone using Tapatalk Pro

 

[WobblyHand]

The motor is a “servo” more correctly a fancy stepper the Teknic ClearPath and is good quality. https://teknic.com/products/clearpath-brushless-dc-servo-motors/

I suspect it’s the gearbox. Probably the hardest to correct.

Sent from my iPhone using Tapatalk Pro

I have a closed loop stepper in my ELS. It won't miss steps, unless it is under drastic load. Under drastic load it just plain quits. Fortunately that has only happened once when I was really pushing the system.

The gearbox you are referring to is where? The kwacker software, how does it infer Z position? At the most basic level one needs to maintain the correct z position vs spindle angle to generate a proper thread.

For your lathe, is your lead screw worn, or your half nuts worn? Or your gearbox?

 

[koenbro]

I have a closed loop stepper in my ELS. It won't miss steps, unless it is under drastic load. Under drastic load it just plain quits. Fortunately that has only happened once when I was really pushing the system.

The gearbox you are referring to is where? The kwacker software, how does it infer Z position? At the most basic level one needs to maintain the correct z position vs spindle angle to generate a proper thread.

For your lathe, is your lead screw worn, or your half nuts worn? Or your gearbox?

Oh no the lead screw is not worn. The lateh is less than 1 year old and more importantly has only a couple of hours of easy load on it.

 

[WobblyHand]

Oh no the lead screw is not worn. The lateh is less than 1 year old and more importantly has only a couple of hours of easy load on it.

If we entirely rule out hardware, and I'm not sure that's correct yet, then the software is flawed somehow. As a guess, it's probably a little of both. Your hardware is probably "looser" than kwacker's and his software may not account for that. I briefly looked at the code base, but I haven't found where his thought process is explained.