Radius measurement with small arc

[[Ba...]]

Hello,
Backstory:
Zeiss had written some programs for us to measure multiple features on this part. They used curves to measure the radius in balloon 16. We are after the results of balloon 21, the center of the "16" radius to the top of the tubes. I have verified these on a vision system, and the results vary significantly from what the CMM is outputting. We aren't recording the value of the radius, just primarily after balloon 21 (0.080 - 0.100). Calypso will almost always output these results as 0.99 - 0.1 with no variation. I have measured these to be about 0.084 - 0.087 using a smart scope. We are using a Duramax, Calypso 2024, 0.5mm probe / also attempted a 0.3mm probe on an angled knuckle @ 45 deg to minimize deflection. These are fixtured with the tubes aligned with the Z axis.  

I have made my own copies of these programs to play around with no success at improving these features. Any suggestions would be appreciated. I feel that vision would be the best way to achieve these accurately and repeatably.

Thank you!

 

[[Ma...]]

For small angle on radius you can measure their position with constraining their radius - forcing calculations with nominal radius.

What i found on small radiuses ( R1.0mm; 90° ) is that your probe needs to be on correct position - so do alignments, bestfit - whatever to be on correct spot for taking points.