Thanks,

I did turn down the accel, but not the speed. I'm using too fine a threaded rod on Z, so it will be unbearably slow, but I do intend to change it, so I'll give it a try tomorrow at the slow speed as you suggest and change the lead screw later.

My concern for the wild start is safety. I don't have limit switches set up yet, but at least I have an EStop (I stay close to it). Of course, beyond that, I still want to fix it just because it shouldn't be doing it. It's a bit disconcerting. Where the heck is it going? It's like it's looking for a better spot, decides the one I picked is the best, so it comes back and starts where I told it to. A mind of its own.

Thanks again,

Jeff

You need to eliminate the possible causes, so slow it down do the test.
Change the feed rate in the program do the test etc etc.
Once you know what's happening you can figure out why and get as much of the lost speed back as possible.
Z Axis are under much higher load than X or Y, so feed rates have to be a LOT lower.

Can you attach your xml and I will see if I can replicate the problem here.
Hood

Incremental mode is shown and the first move is from x&y=0 to the circle. So you may be referencing the axis at the wrong place.
RICH

Thanks to you all. My problems seem to be fixed, but I'm not sure why. As far as the depth change of the outer circles was concerned, I realized that the Z acceleration should also be lowered as were the X and Y for the G0 repositioning mentioned by ERP. If they were being thrown off, why not the Z. Was my thinking correct? It seemed to work.

Then to the wild start. I finally noticed where the router was going on startup. Each time it headed for machine coordinates that I believe were the tool change position. I found that Auto Tool Changer was checked. Checking Ignore Tooll Change seems to have solved that problem. Again, correct? I see in the GCode an M6 at the start (I've been studying ). Why was it there in the first place? Was it there because of the Auto Tool Changer. And if M6 is now being ignored, how will I place an M6 where I want it and not have it ignored.

I hope I'm making sense.

I'm sure I'll have more questions, but that's it for now. Again, thanks to all who helped. Your answers to these questions and any comments will be greatly appreciated.

Regards,

Jeff

I see in the GCode an M6 at the start ....Why was it there in the first place?
Have a look at CamBam settings or post processor since you are telling  CamBam that you want to change tools.  Ignoring the tool change via Mach settings cancells the
M6 command when Mach runs the program. Note that routers can generate a lot of interference and just turnign it on can create a condition to miss steps in additon to incorrect
velocity or acceleration settings.

RICH