Brett,
The spindle and coolant problem was due to a wiring goof with the optical relays
. So that problem is solved and working.
I did some more testing on the limits. I couldn't find any ground loops, and I'm not getting any voltage readings that are out of range for a digital signal.
I have managed to determine the following:
1.) The problem is random. Ocassionally it will screw up on re-boot although that is unusual. I may get 10 homes in a row, I may get 5, I may get none.
2.) The problem has never occured on the Z axis. It is wired the same way and the shield is grounded in the same way at the same place as the X and Y
3.) Changing the direction of the Z axis under soft limits has no effect on whether the problem occurs on the Z.
4.) Changing the home direction of the Z axis also has no effect.
5.) The problem is precipitated by either the X or the Y axis failing to home properly. When this occurs the machine stops. No error is displayed on the mach status line. I can jog with the shuttle pro but nothing happens. When I hit Reset on the screen and then hit it again it will say "limit switch triggered." at which point I overide and drive off.
6.) once either the X or Y fails to home properly the homing is erratic. The Z will move with the Y. Or some other strange combination.
7.) Two things will fix this problem and cause the machine to home in the proper sequence again.
a.) exit mach and start it again.
b.) keep running the homing routine until it works.
after either of these two things happens the homing sequence will be correct until it faults again.
8.) disabling the X+ or Y+ limit has no effect on this.
9.) G64 has no effect on the problem. I cannot make it happen beforehand by entering a G64, nor can I fix it once it happens with a G61
Our machines are different in that you are using NO contacts and I am using NC.
I may switch them to see if that makes any difference, but first:
Try this experiment.
Tell your machine to reff all. Then as either the X or Y hit the limit switch. hit the other one with something.
Then move all the axis to the middle of travel and hit ref all again. Since you are not homing your Z you may not see the problem exactly the same way as I do, but you may get the X and Y going at the same time.
Monty