As usual, you are an incredible wealth of knowledge - thank you!
And here's an update... I tested the switch and it was OK. So I was flicking the switches on the control (block skip, coolant) and making sure they all registered in the diagnostic screen - when I hit the EMG OVERRIDE switch, the M01 error went away.
Hmmm...
I let it go, and the error came back. So I held it in and put the mode switch in handle mode to see if I could jog the axes, and I could. Then, after jogging them, the error returned when I relased the switch. I called Mitsu back, and while I was on the phone with the guy (about 5 minutes after jogging the axes), the error just went away.
I mentioned this to the Mitsu guy and he said that there's no way to tell (other than the ladder) what Leadwell hooked into that mode switch that could be generating the error. He said to go through the ladder and see what various things are tied into the X100 control line, and check them all and see if I can find anything - and if not, when it happens again, track test each line again and see which one is giving the signal to the control.
Sounded good.
So I fire up my program again, and at exactly the same point, it did it again... it does a toolchange to grab a face mill, as the spindle is speeding up and the spindle is moving down in Z (I think the XY motion has completed, but not sure), it gives the error. So something in my NC code is making the machine do something which is causing this error.
The ladder documentation (I found it in the manual with the help of the Mitsu guy) is really bad... it's barely legible. So I'm going to have a very close look at my NC code and see if I can figure out what I am doing wrong. I had thought that since the tool in question was a face mill that was right at the max diameter the machine allows, it may be a spindle load error or something since I'm trying to accelerate it up to 4500rpm. But I'm thinking it's something else.
I'll look through the code and I'll see if I can decipher the ladder documentation in the manual to see if I can get anywhere.
But does the above shed any light on what I may be looking for?
strangely, this problem has happened a few times before... it always just seemed random. I'd shut off the machine and the next day it would be OK. It always seemed to happen in the beginning of a cycle start, never mid-way through.
I bet when I figure it out, it will be a "duh" moment.