Z changing during a carve

Yeah, I have an issue… again…

But I’m not leaning on the table investigating it while also causing it.

I had the longmill going today making a small plaque for my neighbor and everything was running smoothly for about 80% of the carve. I saw a friend walking by so I stepped outside to say hi and we chatted for a couple of minutes. When I came back in it was no longer cutting the wood. It was cutting air about 3 inches above the wood. I then paused it. I click “go XY0” and it goes to the correct XY0. I click “go to 0 for Z” and it goes about 3 inches up above the wood. I used Carveco Maker+ for the design and gcode. Also used Gsender, the latest version I think 1.0.0

Any ideas? Pic and Gcode on Google Drive are below. Thanks

You can see the tip of the bit above the piece. That is where the new Z zero is set and where it was now carving.
https://drive.google.com/drive/folders/1nqqDvvIhCAHMK1zKSMxd7HHC6gR4uebc?usp=sharing

@Swinly Apparently, you need to give me some sort of permission to look at the file. I’ve logged into my gmail account and sent you a request for access.

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I thought I had set it to share for anyone with the link…idk

Okay here is the Gcode…?

https://drive.google.com/file/d/14cL3Y-hj562CIUOW0IxJ3he7_ootBFL6/view?usp=sharing

@Swinly I have it, Lonnie. I’ve taken a quick look, but it is about 380,000 lines, I’ve not looked closely. However, searching for any Z moves greater than 1" positive reveals that there are none. So, at first blush, it’s not the gcode. How thick is the piece?

The material is 1 inch
The model I put together is 0.649 inch

After my last issue, I started surrounding the longmill and laptop with barricades, barbed wire and
mpt305-roll-covid-19-barricade-tapekeep-6ft-distance-3-x-1000-ft-yellow_1

Well, I got the longmill going right now and everything is looking good. I didn’t know what line it stopped on so randomly picked a number about 80% through the gcode and started from there. It caught up to where it left off and is looking good. Slight variation in the Z but I can fix that with a rotary tool.

Do you think maybe I had the anti-backlash nut too tight/loose and the Z got stuck or slipped during a Z movement? I’ve had some pretty good swings in temp/humidity the last few days here in South Texas. I did adjust the anti-backlash which solved (I think) my other thread about a sound it was making.

Hard to say since you weren’t in the room when it happened, but one other area I’d suggest a check is the linear guides. If you remove the two bolts to the anti-backlash nut in the z-axis then you’ll be able to smoothly move the z-gantry along the rails and feel if they’re still moving along smoothly

If you’re feeling some roughness or bumps then I’d recommend adding in a couple drops of oil as we recommend for regular machine maintenance: Maintenance 🛠️ - LongMill CNC

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