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Z-Axis Issues - G-code and ground control difference

Hey everyone!
I’ve had a problem randomly start happening.
I’ll setup my drawing just like I normally have, as well as set my zero…but when I start my program the g code will call for -0.125, but ground control will only show me -0.0.
I’ve verified that my g code is calling for G20 in the beginning. I’ve also reset ground control, rebooted my Arduino, verified my z axis connections, and confirmed that I can command the z axis below 0 manually. Also I’ve verified that I don’t have the steps set extremely low, and even tried making a full depth cut in the g code.

I’m currently making a cut with my zero set at -0.125 just so that I can get it done.

Any thoughts?
This is with the metal maslow kit, and with a setup that I have cut with before already and had zero issues.

Thank you!

TLDR: G-code is calling for -.125 or -.250, ground control is showing 0.0
911 FINAL_detail.nc (257.0 KB) 911 FINAL_roughing.nc (25.1 KB)

Can you attach the file? May have to .zip it to get the forum software to accept it…

911 FINAL_detail.nc (257.0 KB) 911 FINAL_roughing.nc (25.1 KB)

I’ve got the roughing file running and haven’t seen the issue crop up. Is there a particular spot in the file where it most often occurs? When this happens, does GC pause waiting for the bit to reach -0.125?

Are we talking about the line of gcode being executed

43%20PM

or the current Z: axis position?

Here’s a thought, the Z: axis position number is derived from the encoder on the Z motor, and an intermittent issue is most often something mechanical like a connector not fully seated.

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No particular spot that it occurs, just the entire project.
We are talking about the current position. After I finish this cut I’ll double check and clean my connections to be sure though!

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So I finished a cut that I started last night. I had reset everything, verified my connections once again, and then verified them again lol. I ran into the same issue where I had to set my zero to -0.125 to make a cut.

I’ll keep playing later, currently I’ve got a newborn that needs some attention though!

Wisely chosen, the Maslow can wait.

Later, see what the z-axis control panel does - does it misbehave as well?

I agree!

And the z axis control panel does exactly as it should…that’s the mind boggling part. I was playing with it last night with a straight edge and it was moving exactly as it should.

Here’s a sequence to exercise the Z axis, the G4 will pause for S seconds to give you a moment to observe or measure.

G20
G90
G1 Z0.0
G4 S5
G1 Z-0.1
G4 S10
G1 Z0.1
G4 S10
G1 Z0.0
G4 S10
G1 Z-0.1
G4 S10
G1 Z0.0
M30
3 Likes

So eventually this did end up working, but not on the first try. I’ve attached a video link (That should work).
It seems to be intermittent, could this be a motor problem already?
Video Link

Thanks for including the video. On my rig, I get that sound when the firmware is using a very low feed rate. Often that’s because I’ve just started GC and the first file I run is one where I’ve forgotten to put a feed rate in my gcode file.
Here’s a copy of my gcode from above, with a feed rate ‘F40’ set:

G20
G90
G1 Z0.0 F40
G4 S5
G1 Z-0.1
G4 S10
G1 Z0.1
G4 S10
G1 Z0.0
G4 S10
G1 Z-0.1
G4 S10
G1 Z0.0
M30

Load that in GC, quit then start again and see if it runs correctly. Then repeat with the old copy without the feed rate to see if that fails when GC first starts.
The z-axis control sets its own feed rate, and when you ran a different file that included a feed rate, so the problem “disappeared”.

Edit – I’m not certain about the above, I started in to see if I could write a ‘fix’ for it and the steps I listed didn’t make the issue happen. Which versions of firmware and GC are you using? I’d sure like to find a way to reliably cause the issue to occur here…

1 Like