Cylindrical Probe Qualification (extended from disc probe)

[[Ch...]]

*Knowing that this thread is regarding a disc probe I anticipate the math/qualification is much the same for a cylindrical stylus.

Okay folks, adding to this conversation I've got a question for you. Apart from trying what was explained in that attachment (awesome method btw); how would I do this with a cylindrical star configuration? The application requires port diameter diameter measurements that come to an apex, multiple cavitation fixture setup, and need to be able to use a cylinder on all 5 axis.

My current process would be as follows (still work shopping this):
1) Create a calibration artifact (much like mentioned above with a ring gage)
2) Measure with known Spherical Star Configuration
3) Measure with Desired Cylindrical Star Configuration
4) Establish offsets and edit the qualification values
5) Duplicate the same Cylindrical Star Configuration for respective perpendicular offset (Z, X, Y, etc.)

I feel like this should be some simple trig, but I'm having trouble understanding one bit of it. If I run two circle paths on each cylinder/disc, does the established Z get placed at the center of the two circle paths? Or is it somewhere arbitrarily? I feel like it shouldn't be that difficult to figure out. AND I don't want to make an artifact for every variation of size to use and requalify my stylus every time to different master references/programs/etc.

Cylindrical Stylus Qualification Inquiry.pdfCreate_Disc_Probe_for_VAST_XXT_140315 (1).pdf

[[No...]]

The Z coordinate is wherever you edit it to, but it is only CORRECT in the area where you probed the cylinder. I guess it depends on what the actual shape of the cylinder is. After all you need some distinct point the CNC paths refer to, so it'll be a compromise in the end.

By the way, I wouldn't use a ring gage. Think about it. The cylinder will practically NEVER align perfectly with the ring, so you will always have small deviations just because the cylinder is a tiny little bit askew to the ring. A disc probe is spherical and always touches the ring with a point on the sphere. This is not the case with the cylinder, so in practice it will always touch with the wrong point, no matter how small that deviation may be. A sphere is a must with cylinder probes.