I wrote a little macro to set the Z Zero for my pen plotter. Here it is in its entirety:
G53G0Z-5.8
G92Z0
It runs, the Z descends to machine Z-5.8 and the work Z sets to 0, but then it throws an error, “Machine travel exceeds limits”. I can clear the error and go ahead with the job.
The same thing happens when I enter just the G92 line from the HMI MDI, and it also happens when I try it on the X and Y axis. It’s weird, because there is no move commanded at all! It’s a minor problem, but it should work.
James at RealTime support can’t reproduce the error.
I’m hoping some of you will try this and tell me what happens.
For example if your z has 6" of travel and the machine zero is at the very top it’s travel where the homing sensor is, but now you use your touch plate to zero off your bed, then your work zero is the bed top. You are asking it to go to the bed (work zero) and another 5.8" below that. If cutting .25" material and I zeroed off the top of that, but wanted to go through to the bed surface after G92, the command would be G0 Z-0.25 for rapid or G1 Z-0.25 for a slow move to cut the thickness of the material. Test at your own peril…I am far from an expert.
The G53 command works as it should. No matter where the spindle is positioned, it moves to the proper machine coordinate, providing it is within the hard limits of the axis.
The G92 command is what causes the error, and the error occurs on all three axes. The command shouldn’t move anything, and it doesn’t. The controller does zero the work coordinate, and then complains that I’m trying to move the machine past its limits. All it should do is set the work coordinate of the axis in the command to zero.
This is evidently a problem that has recurred, here’s a link to the discussion in an earlier forum post.
I’m still hoping that some folks on the forum will help me out by entering “G92Z0” from their MDI, and telling me what happens.
I played around a little and it seems that any time you run g92 when your z is below -4.5" on your machine position the error occurs. If you are above -4.5 there is no issue.
I don’t see that as a solution. I should not have to use G53. If I am in G54 and issue G92 X0 Y0 Z0 using the MDI the axis all get set to 0, But If I try to use G92 inside a gcode file it errors out, no bueno!
I’m not sure what the issue is. Apparently, some work, some don’t. The last word I had was that Realtime and OF were exploring the problem.
“G92” by itself worked with my BB controller, didn’t with my Redline.
I’m using two macros (G Code programs) in the Redline right now using the “G53G92” syntax, and they both work with no problem, zeroing all 3 work axes. That solves my problem.
And that’s what happens on my machine. The work Z-coordinate resets to zero at the current machine Z position without the machine moving or any change in the machine’s Z coordinate.
Remember that “G53” is non-modal; you’ll remain in the “G54” mode after that step.
In my little experiment g92 on worked when the z axis was at -4.5 or higher. Probably just adding unneeded info to the thread but I thought it was a weird quirk.
I believe I was just zeroing using G92 not using g53