RDS-CAA Angle Discrepancy

[[De...]]

Hello all,

 

It has recently come to my attention that I am getting different measurements while using different angles on my RDS-CAA head.  Checking a 2.49969 Ring in the same spot with A+B at 0° it's perfect.  Then using B at 35° and again at 45° in the same locations yields different results.  I am using the 35° method to ID grooves in customer parts that have ±0.001 tolerance.  This is right after requalifying the probe being used as well.  With this much of a discrepancy from straight to angled, I'm wondering if I need to try a disc probe and stop using the articulation of the RDS head.

 

Any suggestions or ideas on what I could/should try to make this better or is it "Go with a disc" at this point?

 

Attached is a PDF of the 35°, 45°, and straight scans.  The screen capture is of how I am doing the scans for the angled measurements.  For the X axis measurements I have "A" at 0° with "B" at -35° and 35° while for the Y axis "A" is turned to 90° and then "B" repeats the -35° and 35° angles.

7-27-26 35-45 DEG CHECK.pdf

[[De...]]

Hello again,

I was able to speak with a Zeiss representative and over the phone and TeamViewer, I got the exact help I needed.  Using a more accurate qualification method is exactly what was required to overcome the issue with the off measurements.

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 Care to elaborate on the details of a more accurate qualification method?

 

[[De...]]

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Yes.  I was wanting to give it a few days of testing it out to see if the solution still works and I'm glad to say that is has worked flawlessly.

 

Steps are as follows:

1.  Open the Probing System Qualification window

2.  Click "Insert new stylus system"

3.  Have your stylus ready in the desired angle you want and uncheck the "RDSCAA" box.  This will set the current angle as the position for this stylus in which to be used.  Having that box checked will have it do the multiple position qualification throughout the range of the head's motion.  (That's what I had originally done for my 2MM stylus.  This is less accurate as it calculates parts of the stylus that it doesn't touch to the sphere.)  Having the box unchecked will qualify the stylus locked into that position.

4.  Name your stylus and the current position.

5.  Now Qualify

 

After you have the base qualification set, you click "Insert new stylus" and add more positions in whichever angles you want.  I myself have nine(9) positions for my 2MM probe now.  Each is named for their angle in A, B format.  For example, A:0, B:-45 is named "0 -45" and so on to help with later programming so as not to have to remember which way the stylus is pointing.

With this now done I am more confident in my findings and reports as it is more accurate and consistent with our other CMMs.  

2MM PRECISION PROBE CHECK.pdf