Z-axis doesn't hold setting after restart

[bhdavis]

Both my x and y axis local zero setting hold when I restart UCCNC. However the z-axis does not..........or at least doesn't consistently hold its setting.

This was the case before adding my ATC when I was running Ver. 1.2111 and remains the case after adding my ATC to the system and updating Ver. 1.2113.

I also am getting some inconsistency in my local Z height location after making a tool change. Sometimes my Z0 location remains where it was on the previous tool but most of the time it has moved upward.

Plus sometimes when I touch down to the material with my portable probe it sets Z0 a 1/4" or so above the actual material surface. Then on a second touch down it hits it dead on.

Not sure where to look to resolve this. If it were always happening the same then I'd say the problem was in the G31 macro but as I said sometimes it works fine. I'm beginning to wonder if it might be my ancient Sony Vaio laptop that is running Windows 7.

My z-axis settings are below in a screen shot. I'll add that I've never set anything up in the PROBE settings windows. I've just entered my physical probe height in the G31 and M931 macros. I do not believe the PROBING PLUGIN is enabled but do need to go to the machine and check that. Perhaps that is the problem?

Thanks,
BH

[Battwell]

have you added more weight to the z axis with atc conversion?
have you run a repeat rapid test up and down full distance of your z axis? to see if z is losing steps.

[bhdavis]

Thanks for the suggestions.

I have a gas shock counter balance on the Z-axis so while my new retracting dust skirt is heavier than the old pre ATC non-retracting dust skirt, it is countered by the gas shock. Now the gas shock could be over strong and causing a problem I suppose. I'll look into that. Thanks for making that point.

I have not done a rapid up and down to check for missed steps so to speak. But it is servo driven and I've run hundreds of files with thousands of up/down moves and the Z0 remains constant once it is established on a given tool. So once it is set it holds during that session with UCCNC. But if I turn off the PC and come back later to run the router again the Z0 will have changed while X and Y have held their setting. The gas shock keeps the Z-axis from drifting down when the system is shut off. Plus Z is a screw feed which helps to counter gravity drift down as well. But per your first suggestion I guess the gas shock could be pushing it up. I will definitely check it out. Plus I'll do as you suggest and run a repeated full z travel up/down process to see if it holds the Z0. Easy enough to do with a loop file moving Z up and down for 10 minutes or so.

But that still wouldn't explain the first touch down with the portable probe not setting correctly while a subsequent 2nd attempt hits it dead on. Very weird.

Thanks for the help. Much appreciated.

BH

[spillage]

I put a servo brake on my Z to avoid any movement when not powered.