8L lathe looses reference position in the middle of a program

Just wondering if anyone else who has an 8L is seeing this issue. It’s not a huge deal, but is very annoying when it happens. I’ve had my lathe set up and operational for a couple months now and in that period of time I’ve had this happen about 3 or 4 times. While running a program, at some point, the machine will loose both X and Z reference positions. Initially I thought maybe it was something I was doing, but was running a lot of 11 parts today and it did it again. This is a real pain in the butt since once this happens I have to reset my work offset to get my size back to exactly where it should be. Anyway, is anyone else seeing this issue, and if so do you have any idea of what the cause of it is? Other than this issue I couldn’t be happier with this fantastic and capable little lathe!

@LARRY_PHILLIPS Is the machine bumping you into EStop and Reset condition, needing to actually hit the reference X and Z button? Or are you losing motion, and need to re zero you work offset?

Yes, it acts as if the estop has been made. In order to continue any operations at all I have to reference the X and Z axis both again just as if I was restarting the machine after having it powered down. At no time during operation does the machine act as if it has lost power though…such as lights blink, feed waver…no indication of anything like that.

This one sounds like you may want to start a technical support ticket with us, to get you back to reliably making chips! Jira Service Management

Thanks for the input. I’ll definitely get one started. I just wish it would do it a bit more frequently so I could establish some sort of pattern that I could make heads or tails of.

Hi Larry, I have had something similar happen to my 8L lathe a couple times. If I am manually jogging with the pendant and accidentally go past the z limit, I then have to disable the limit switches jog the machine off the limits, turn limit switches back on and rehome the machine. As long as I don’t jog the machine into the limit switch at full rapids I don’t have the problem. Have you been able to replicate your issue or is it still just random?

Brian, I’m thinking you may have just solved my problem.:grin: It always happens when the carriage has just went to the g30 position when I haven’t moved it from the home position. I wasn’t able to come up with a pattern until you mentioned what and where your machine done it. I’ve never had my machine do this when I’ve had the g30 moved a bit up the bed towards the headstock end. Thank you so much for your reply… pretty sure you just saved me a whole lot of time and trouble chasing this down. Kudos to the wisdom of the crowd!!!

This is a strange series of events. PathPilot shouldn’t allow you to jog into the limit switches. If you are able to move the machine in Z+ and bump the limit switches then you something is amiss. One possible reason is if you are running too hard in Z, while cutting, and the machine is loosing Z position. Another possible outcome is something is amiss with your machine. If you can figure out a way to repeat this scenario then we would love to hear about it.

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So far , knock on wood, moving the G30 position just a bit towards the headstock seems to have cured my issue. I haven’t had a single issue with this since I’ve started doing this. I may only move it less than .100" but that seems to be all it needed. Thanks everyone for all your replies, y’all got me thinking in the right direction to find my solution.

Just to make sure I understand this Larry, are you saying that you would home the X and Z after startup AND then press the ‘Set G30’ button before moving at all. And later during that working session you might return to G30 and sometimes or intermittently the machine would act like the E-Stop button was pressed? And this intermittent problem no longer happens as long as you move a little forward on the Z before pressing the ‘Set G30’ button?

It’s my understanding that when the machine references the X and Z, it moves to the limit switches and then backs off of the limit switches some number of steps (let’s say N steps). So if your machine has been coming back to G30 and hitting the limit switch thus putting the machine in an E-Stop-like situation, it would at least suggest that your machine lost N number of steps somewhere along the way in the operations you were doing. Is it possible that any of the operations you programmed were heavy in the Z axis such as bumping up the Roughing Depth of Cut on an OD Turning operation?

I only ask this to try and understand the root cause better. Moving forward a bit before setting G30 is really a workaround if my hypothosys is correct.


Paul, your description is very close to being correct, but not exactly. This will highlight just how little I knew about programming a CNC lathe when I was getting started, and makes me realize even more about what was happening. After referencing the x and y axis I would write my program with no concern for setting up any G30 position. So basically it was using the limit proximity switch as G30. Had I actually set that limit position as G30 I may not have had the issue, but since I didn’t set a G30 I’m thinking that the machine was possibly overshooting the limit switch and that would cause the fault. Again, this is just me thinking, but ever since I’ve been actually setting the G30, wherever it’s set, I’ve not seen this issue. So, ultimately at the end of the day as is so often the case, the root cause was operator error. :neutral_face:

Ok guys…I have finally figured out what the cause of this is and thought I’d post it. I had this happen to me twice again today and the g30 was set off of the limit switch. I was cutting some stringy hot roll pipe and one of those stringy chips had gotten back up under the back side of the carriage far enough that it made the limit switch…at least that’s my theory since both times it happened I was pulling chips out from behind the carriage and they run back far enough that they would have easily made it to the limit switch. I’m not sure what I can do about this other than do my best to get the chips to break, but as we all know that’s not always an easy task. At any rate, hopefully this may help someone else that goes to chasing this problem.