Reporting the width of an o-ring groove ( or the difference between an I.D. and an O.D. )

PcDmis 3 years ago in Metrology Software / PC-DMIS updated by Guillermo 3 years ago 4

Reporting the difference between an inner and an outer diameter is easy by "normal" calculation, but that doesn't take into account if they are concentric or not. Correct way of checking the O-ring groove would be to measure points at the same position both for the outer and inner diameter and report the distance between these. So, it is more the way it is measured (technically) than how it is calculated.

If you are sure that the form is good enough for both diameters, I guess you could use the radial distance between the diameters center points and the measured diameter values to calculate the min and max groove width. But the method outlined above (with points) are the most correct in my opinion.

I believe this idea center entry shares a lot with the technical aspect of this measurement:


This is a must-have! Wall thickness and Groove depths on cylindrical parts should be able to be checked 360° simultaneously. Not just in singular locations.

Should not be limited to tactile systems, but also vision systems.  One typical check are also o'rings themselves never round)

A rule set should be established that OD feature have equal or more points than the ID feature in the case of tactile (CONTACT) type feature.  I don't agree with the thickness as the radial distance or distance from opposite points.  First, as mentioned above, OD and ID may no necessarily be concentric.  Second, there is no way to assure that the positional error of a machine driving to take a hit in combination with any probe compensation results on points that are on same radial line (e.g. assuming ID feature is the center).
My suggestion is to evaluate the 2D (features common plane) distance between each point from the ID feature perpendicular (shortest) to cubic spline fitted curve (or arc segment)  thru all the hits on the OD feature.  Report the Max., Min and average values as MEAS.