Hi all,

I've been running Mach 3 for better than 10 years on my CNC, which has a CNC4PC C23 BOB with USB Smooth Stepper.
I've not run the machine in many months, but today I decided to fire it up and do a little trouble shooting.
The machine uses two motors to drive the gantry, with Y being the primary axis and A set up as the slave axis.
There are home limit switches on both ends of the gantry, at the Y and A.

I went to the Diagnostics screen to home the machine axes.
I first want to set the homing on the X axis, hit the Ref X button, and that went smoothly.

Then, I hit the button Ref Y button...
I knew that the gantry was a little bit racked, so was expecting the gantry to move forward, hit the Y limit switch, and then continue moving the A side.  What happened was, the Y switch did trigger as expected, but A side stopped.  Then, the Y continued to drive forward until the machined indicated that the limit switch went off.   Broke the limit switch.
I replaced the switch, same results.

Any thoughts?

Thanks.

Was there an indication on M3 that the Y limit was active? I think to start you need to see if the light in the M3 diags screen comes on to indicate whether the PC thinks the limit switch is active. You should be able to do this without moving the gantry, just manually activate the limit switch.

Hi David,

Thanks for the reply.

So I'm getting weird behavior at the Diagnostics screen. 
When I touch my touch-off plate to the bit in the spindle it lights up the "Digitize" box, and the "M3 Home" box.
When I push the limit switch for the X axis, the M1 Home box lights up. Nothing else.
But when I push either the Y or the A limit switches, they trip the system, and I have to Reset.
The Y switch lights up the M2 ++Limit box, and the M2Home box.
The A switch lights up the M4 ++Limit box, and the M4Home box

From memory, manually pushing these switches in the past never tripped the system where I had to Reset.

Thanks.

Activating the limit switches when the machine isn't homing should cause a system "Reset", if the system is enabled before you push the switches, because the machine thinks it has somehow moved out of bounds.
Perhaps your memory is not what it used to be? (see what I did there?).

LOL... Yes I get you!
However, I'm talking at the Diagnostics screen.  You should be able to push all of the limit switches on the screen without it tripping an E-stop type of action.  I think I may have a wiring issue.  Going to dig out my multimeter and check things out.