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CMM cannot turn on motor because of limit switch


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Before giving Zeiss a call has this happened to anyone else. I tried homing the CMM and it stopped when the head is at top most Z position. Is there a z limit switch I can press to lower the head a little. I cannot move the head with the joystick. This is for an Accura

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It has been a while since I've done this but as I recall there a small hole on the side of the Z cover that you can stick a hex wrench, screwdriver or other rigid device that releases the brake that is holding the Z ram in place.
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If you could post a picture of the front of the Z of your Accura, that may be helpful. The brake release access can be in a couple different locations, depending on the Accura type.
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That is the correct hole to release the brake for this model. You will need to hold down the button inside while you pull down the Z ram. It will take a bit of force, as there is still mechanical braking to prevent the Z from just slamming down under gravity.
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It's on the bottom now.

Just remove that front cover, and you will see the one that you need to press in to release air.
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Thanks!. I used more force and it moved down enough to clear the limit switch.
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Outstanding.
I would then recommend using the joysticks to move the probe head to roughly the center of the volume in all 3 axes, and turn the speedknob down to around 20% before attempting to home the CMM (this is often not necessary, but I find that in situations like this where the CMM failed to home due to hitting an endlimit it often increases the success of the next rehome)
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We have the same problem, but in Y.
I don't know what the official fix is going to be, but we got it to home after cleaning the glass scales.
I wiped down the scales a couple times. i just put a little alcohol on a rag and reach down and clean it, but it was still having issues. but when i went back and cleaned it again, spent more time making sure it was good and clean, it finally worked.
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We often had that phenomenon on our O-Inspect 322 when the axes were too close to the limits before homing. The machine would then fail to recognize the limits and hit the end stop. The only remedy was to move far enough from the limits before homing.

I was very pleased to learn that on our new Conturas there' s no need to move the axes manually anymore. Even after hitting a limit you just activate the drives again and the CMM is ready to move. Well done!
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  • 4 months later...
This happened to us many years ago when our Contura was new. I was not the programmer back then so I am not sure but I thought someone moved the CMM home position away from the limit. He was actually Zeiss training teacher. I know he did something to it. We never had it happen again.
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