Keep getting z axis overtravel alarm 146

[dragon864]

We get a 146 z axis over travel alarm. It never happens when it's changing tools or near home. It happens with vibration or if we run in 100%. I can't remember when it happened at 50%.
Sometimes it happens 2-4 times a day....and won't happen again for a month or so. This is a VF3 2006. Haas service checked the plugs on the boards and said they didn't find anything loose. And they checked the operation of the z switch and everything checks fine?

[GITRDUN]

Encoder problem maybe? Does the machine lose track of where its Z is located when it happens? Like does it throw up some crazy Z axis position number, or does it still show the correct Z position when it happens? I know a couple of our Haas VF machines will throw up an over travel alarm if it reads an axis position in the program that is beyond the over travel switch. It wont move untill it hits the switch, it just stops and puts out the alarm because it knows it cant move that far without over traveling.

[dragon864]

Thanks for the reply.......It happens while it's running a program that's been run before. I'm not sure what the z axis readout says when it alarms in z.....I will notice the screen next time it happens.....

[serviceman]

146 is a y axis alarm this new of a machine has proximity sensors and can get fooled by chips is it a 146 or 147 alarm?