Computer turned off in the middle of a cut

I’'m working on cutting some fully 3d models of cars(Mustang at the moment) but about a quarter of the way into a cut using UGS my computer turned off because I moved the fan that keeps the old piece of junk from overheating. When I got it started back up along with UGS it was reporting my location as being way off from where the bit stopped relative to original zero. Even if I could figure out what the last command was I have no idea where zero is anymore. Work position is at some nonsensical values 6 inches off my part and Material position is now 0,0,0. My questions are as follows:

  1. Any idea how to deal with premature stoppage? Does UGS log somewhere that I haven’t seen? I’m considering trying to pipe all the command-line output to a file. Then I can figure out what the last command was and start from there.

  2. How the heck did the position get so far off? I would have thought that the computer would have been sending G1s and suddenly stop which should leave grbl hanging, but still with it’s original work zero. On starting UGS again it should read the zero back from grbl right?

I too have been caught and though I’ve yet to try it, I wondered about doing the following…

Home the machine

Move to whatever point is going to be the 0,0,0 for the job.

BEFORE setting X, Y and Z to zero, record the current X, Y and Z positions from within UGS (relative to the Home position).

Set the zero positions and cut as normal.

If the worst happens and you lose zero, all you’d need to do is home the machine, manually move it to the X, Y and Z positions that were recorded above. Reset zero at this point and then begin the job again.

Mind you, I’ve never tried this…

I did not. I use the “drop bit in the x/y position i want until it catches on a piece of paper” zeroing method. Are you saying that if I made machine zero the same as work zero at the beginning then after restarting the position would have been correct relative to my original work zero? Either way, I with there was a button for resetting both instead of just the one…

I agree, I did this many times working out how to get a good pinewood derby car, and by using homing and a fixed piece of wood to align the blanks, I was able to “re-x-carve” the same shape several times, even after regenerating the g-code or changing bits.

WARNING: successful bit changes require a way to accurately set the Z zero position!!!
If you haven’t tried it yet, then this is probably harder than you think, since your original Z zero position on the stock probably doesn’t exist any longer.


Ah! It’s relative to machine zero! That’s what I didn’t understand. I see what you were saying now. The “Learning about G28” post is very helpful, thanks.

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It kinda appears there’s a few automated ways to do this and clearly I need to learn more.

My suggestion perhaps was less than clear. All it entailed was to manually record the point where you set the 0,0,0 position, before you began cutting. A point which is relative to the homing location for your machines and is a location that is easily repeatable and easy to find.

After recording the UGS info, you then go ahead and (without moving the bit) do your normal process to zero each of the three axes In UGS and begin work.

If the job is interrupted and zero is lost, you can simply ‘home’ the machine and then manually move the bit to the UGS location you recorded. This position is the same spot where you originally set your axes to zero and began work. You can then reset each axis to zero and restart your job.

It sounds long winded, but it’s simply a manual method of returning to the location where you set 0, 0, 0 on your material so you can quickly find it again when or if needed.

I have been living on Center of project cam position start if something drops I can manually roll back to where it started - if using the lower corner you can do the same thing. If the system sleeps you get boned. overheats boned… sorry but a stable computer is a serious need on something like this even in UGCS there is no way to tell what line you were on so an air cut to a similar local or just letting it rerun 100%/