XC Homes correctly, returns to zero correctly, starts carve incorrectly

Hey Gang,
I’m hoping someone might have some insight to this problem.
My machine has been working quite nicely since being built in the summer. I did some beautiful engravings over the winter holidays. When I tried to do a simple engraving today, the machine homed correctly, it returned to zero correctly, my gcode appears to be giving the correct instructions, but when I actually start the carve, the first thing the machine does is send the gantry to the corner opposite of home at breakneck speeds and crashes hard if I don’t stop it manually and quickly.
(sorry for that last sentence…it’s a bit of a run-on)

Manual control of the machine also works correctly.

Yikes! Maybe a loose wire? I’m not sure but maybe triple check your connections.

I have already ensured all of my connections are correct and secured (3 times for good measure). I have cycled power on both the XC and the laptop that feeds it gcode (twice for good measure).

I had an issue over the holidays where I had to reflash GRBL but I was able to complete several projects just fine after that incident. I believe all of my GRBL settings are correct but it also seems like at this point that’s the only potential cause for this problem. I’ll have to go out to the other laptop to get a screenshot of them to share. In the meantime, if anyone has any suggestions or experience with a similar issue, I’d love to hear them.

Since you home your machine, do yourself a favor and turn on soft limits ($20=1) at least until you get this problem solved.

I use Fusion 360 to generate the gcode. I use UGS to send the gcode.

I’m well aware that home and zero are not the same thing. This does not change the fact that the machine homes correctly and can return to whatever zero I set correctly. My tool is positioned correctly on the machine and in the model and in the cam pathway.

I appreciate the attempt at suggesting solutions but these are things that I’ve already eliminated as issues. I have realized that I may have forgotten to remove a few commands from my post processing and I’m going to double check that shortly. If that doesn’t fix it, I will be trying a different mode of sending the GCode. When I return, I will upload a screenshot of my GRBL settings and also my GCode.

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Thanks, but that wasn’t the problem either. I have already been using soft limits rather than hard limits.

Keep em coming folks! Eventually we’ll find a suggestion that catches the problem.

Look for G28 or G30 in your G-code.

Next time you try it do a $G and a $# command to grbl after the failure and post the results here.

Thanks everyone! It was G28 causing the issues. I forgot that every time Fusion 360 updates it for some reason resets the GRBL post script settings to include G28 and Tool Changes. I will make a note to double check this in the future before I do my post processing.

It’s most likely in the post processor. Check that.