Dropping Probes

[[Ha...]]

Has anyone had any issues with probes being dropped during an automatic stylus change? This started happening a couple of months ago and we cannot figure out the issue. It is only happening on one of our probes that is fairly long, but we've also been using this probe for over a year with no problems prior. So far we've tried replacing the adapter plate, steel and ceramic extensions, cleaning every piece of hardware. The only work around we have is to put a programmable stop before this particular probe is put back. The operator has to slow down the feed rate and watch the probe settle so the spring does not push the probe out. Any suggestions on what we should do next?

Stylus Dimensions
50mm ext., 5mm adapter, 20mm ext., probe length 10mm

[[Mi...]]

Please sign in to view this quote.

Different answers for different head types/CMM/environments. Our CMMs are probably put through the most demanding environments, tell us what your CMM and head is and I'll give you some suggestions.

Also clarify the direction of your probe? is all of that in -Z or in one of the radial Axes?

[[Da...]]

Have you tried to change its' position in the rack? I had a similar situation with a spectrum years ago, when I switched the "bad" probe to a different pocket the problem went away. It has not happened again.

[[Ha...]]

Thank you for the responses!

Michael,
We are using a Contura CMM with RDS Vast XXT head. The problem happens when the probe head is at A-90 degrees and is placing the probe back in the holder. The CMM will be moving towards the back of the table in the Y direction, release the probe in the rack and the probe does not seat itself quick enough. The probe will essentially wobble/rock and because it is not seated, the spring will push the probe out of the rack position.

David,
We have not tried switching the position in the rack yet, but I will have the operators give that a shot next thank you!

[[Mi...]]

Please sign in to view this quote.

When we run into this, the most overlooked part is dirt/gunk on the bottom of the XXT change rack, causing the probe system to not drop down and settle fast enough, then it gets kicked out.

A poorly aligned change rack has also caused this for us, since defining it 1 time creates the location for all 3 positions - if your rack is tilted slightly you might run into this - especially in the far right probe socket.

Heavier, well balanced probe systems will be less likely to have issues - but the weight limits of your XXT head should always be a concern.

This could be make so much simpler if Zeiss let us control how high the head lifts during the probe change, or let us program a delay.

[[Je...]]

Several factors can contribute to this. [list=]

Stylus is too long

Stylus is too heavy

Tab on plate is bent

Stylus rack is misaligned/crooked/cracked

If the stylus is "wobbling" when it is placed in the rack that is a clear indication of one of these criteria or several. Bent tabs are the most overlooked item as they don't appear to have any interaction with the stylus rack yet they do fit into the slot that retains the plate.