Erratic plunge when starting job

Randomly the z axis will plunge deep into the project when I start even though I have zeroed everything. Sometimes this happens between two projects as well.

I usually end up restarting Gsender and that fixes things but I have destroyed the workpiece.

Any ideas? Do I have to restart gsender after each project?



I had this happen on my longmill as well way back. I checked my drive belt gears and the motor at the top my Z axis and discovered that it had become loose over time.

Suggestion …


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Maybe make sure absolute rather than relative programming is enabled; G90 in console is absolute, G91 is relative; homing or an abort will not change the setting


Okay. Don’t know how to check this. Am I setting this somewhere in Fusion 360, or is it set in Gsender?

Had the exact same issue. I check that before starting each job. Only takes a second and can save you from turning a beautiful piece into firewood

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How do you check to make sure absolute rather than relative programming is enabled?

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@MajorSciGuy What CAM software are you using to generate your gcode, Jeffrey?

Fusion 360.

Ran the same files this morning with no problems so it doesn’t seem to be code. Could I be doing something incorrect during power up and connecting with my laptop?

@MajorSciGuy It’s not likely as there is not much to go wrong. If you are running Windows, be sure to turn off any power saving settings related to USB ports. If you are setting Z0 using the touch plate, after setting Z0, click on “return to 0” to ensure that the bit is now sitting on the top of your work piece and that the GUI shows Z at 0. Neither of these steps should be necessary, but they can save some grief. Finally, and this is particularly relevant if you are using either very thin stock or very thick, make sure that the Z gantry is not hitting its stops at either the top or bottom after you set Z0.

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same file with no problems, did you do anything different, Startup sequence change? Or just roll with it…