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X-axis stops moving during machining cycle with no alarms

Troubleshooting problems when no alarms occur are always fun. In this case it was an intermittent problem where I happen to get it to stay in a condition to troubleshoot. The main goal of any troubleshooting is to repeat the problem or troubleshoot when it is in the current fault condition. With this problem I was lucky to have the problem occur and catch it in time before it changed back.
 
Typically when an axis stops moving it has to do with a pallet changer or tool changer on a horizontal CNC not in home position or a switch status that changes for some reason. After looking at these areas, what I found was the pallet up switch happened to be false triggering while the down switch was also made. Most machines have some alarm circuit tied to it when this condition occurs but this one did not. The CNC machine I was working on was a Mitsubishi M-H5A with a M300 CNC control.