I have an AvidCNC Pro 48x96, and I am running Mach 4.  Everything has been great but suddenly I have a problem.
 
When I home the machine, the Machine stops and the error line says that the motor is having trouble backing off the limit switch.  I switched to the diagnostic tab and everything looks good.  However, the Y axis keeps both indicators lit.  I don't know where to look to fix the issue.  I don't know if it is a Mach 4 issue or a motor/hardware problem. 

If anyone has any advice, please share.  I am going to post this same thing on Avid's forum to see if that is the place to go for a solution.

Can you jog the Y axis in both directions?

Can you jog the Y axis in both directions?

Yes, if I override soft limits

Still having issues.  The machine will not home and so far, no solution.

Quick question, is there any way to set a home position without using the home (automatically) button?  I have a project for which I am in the middle and cannot proceed without finding out why the machine will not home.  If I can set a homing position without the machine (and software) itself determining this position, I might be able to get back up and running.

Hi,

However, the Y axis keeps both indicators lit.

So, am I to understand that you have multiple switches on one input? Or do you have one switch per input?
Most people try to combine them, and often have problems. May I suggest disconnecting and (programmatically) disable all Limit switches so you have just three Home
switches.

Mach, when homing ignores Limit switches, and when not homing ignore Home switches. The problem is often the transition from one mode to the other.

In the first instance I would try to home the machine with Home switches only. That should eliminate any problems that might occur during the transition.

Second issue is the dynamic response of the switch.

When Mach homes it advances towards the Home switch until it activates, whereon Mach decelerates to a stop. Then it will back up until the switch deactivates.
If the motion control issues pulses to back the axis up the axis will back up, but not immediately. It still has to accelerate. Thus the switch deactivation will be delayed.
If the motion control detects that despite the issuing pulses for the axis to back up, and yet the switch has not deactivated within some given time, then it will fault out.

What sort of switches are you using? What speed are you allowing the axis to use to backup?

In the first instance use say the X axis or the Z axis that has only one Home switch. Disable all the other axes from homing until you understand whats going on with just the one axis.
For instance its common to have the Z axis home first, so that it is up and out of the way. Once it homes and the DRO is set then the Home switch will now be treated as a Limit switch
(if you have combined them into one physical switch) and any noise or inadvertent activation of that switch, and it is very close to activation point after all, would stop the rest of Mach's homing routine.

Craig