Problem with high standard deviation during tip qualification

[Douglas]

OK... yes I know about off topic and this is about half way there but I see so many discussions on standard deviation during tip qualification, they so often dive down a rabbit hole of how many hits on how many levels and touch speeds... the discussion will often not be complete until somebody brings in prime numbers.

I'm chiming in to say before you do any of that check your hardware... this adapter at first gave me all the symptoms that people blame on a module that is going bad. First couple days I could not get good SD then I watched it and calibration offsets floated around a few thou at first and my results correlating to other probes was an issue.

First I rebuilt the star probe thinking it was moving around...nothing.
Cleaned everything and re-calibrated... still no change.
Started to blame a bad module but then the error grew beyond what I could believe for that.
Closer examination finds the adapter coming apart... apparently these are only glued in from the factory. It is an older Tesa but Hexagon bought this stuff and it crosses over to some HA- number now.
Anyway yeah sorry if you say this is off topic but enough people run these things with pcdmis that it is worth knowing how poorly these are built from new, and watch for this along with loose tips etc... this had me chasing my tail for a while until it came apart enough to detect... last thing I expected

adapter.jpg

[Douglas]

to update, after swapping out the adapter, I added one feature to a part run to compare position and size between this probe set and a short ruby, have not seen half a thou error yet.

[Mike Ruff]

This is a good point, and not something that comes to mind right away. I have had a similar issue over here, where I was seeing my star tip rotate due to side hits slowly unscrewing it, I had to recalibrate every 2-3 parts. The non-star tip in the same program was very consistent and would repeat very well, but the star would not. It turns out the problem was actually the TP20 unscrewing itself from the HA-TM-31 that was causing the deviation. I didn't realize it until it came unscrewed enough that it was actually loose and I noticed it move when I was swapping tips manually (no rack over here). I tightened it back up, recalibrated, and haven't had the issue since!

[Douglas]

yeah everyone is so fast to blame the demon... just my opinion there

[JEFMAN]

I've had the same problem with a Ø8 L 100 tip (ceramic stem Renishaw for SP600).
The std dev wasbad, I cleaned the sphere, the ball, re cleaned the sphere, the ball and at a moment, the ball stayed in the soft paper I was using with alcohol...
Someone said "the devil is in the details"...(Nietzsche ?)

[Douglas]

loose ruby has got me before too, I watch for that and even rebuilt the star probe on this one to no avail... this one had me head scratching until I had wondered if the body was loose on the adapter and looked closer at the whole thing

[AndersI]

Micro fractures in carbon fiber shafts are quite similar...