Problem- z-axis overtravel at tool change

[jam-man]

I have an Okuma MC60 VAE with a 7000m control. About once or twice a week it will over travel the Z-axis in the positive direction during a tool change in auto. I don't have a clue what to look for. Any ideas would be great

[Goldorak]

Originally Posted by jam-man I have an Okuma MC60 VAE with a 7000m control. About once or twice a week it will over travel the Z-axis in the positive direction during a tool change in auto. I don't have a clue what to look for. Any ideas would be great

check for chip on the limit switch, this happen sometimes , it turn on the LS before it reach the limit, thats why you get an over travel alarm

[Algirdas]

most likely, yes, the chips. Aluminum especially. preventive cleaning under the Z axis guideways cover would be usefull anyway.
What more could be:
1. wrong setting of home position Z axis location. You need to check ATC thoroughly.
2. wrong setting of Z axis user positive limit.
3. some mechanical backlash combined with wide "in-position" setting.
These are not worth to check if there was chip collection.

[old timer okuma]

i have seen once before when the reset/spindle stop/jog stop switches start to go bad. originally they were all NC switches on just those, the rest are NO. then the NC switch starts to go bad it flickers just fast enough to confuse the control. if nothing else works on this consider replacing all 3 of those switches. they are one of the few switch or parts on a board that okuma will sell. they are soldered on and once you replace them you will have to change the jumpers on the machine panel control card (3 jumpers), if you don't have a IF card that has the jumpers you will have to upgrade to one.

[jam-man]

i replaced the switch about a month ago and have had no more trouble.
thanks for your help