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Please help with a very tricky measurement

constadin
Hello all,

I have the following measurement to do 12.4 (mm):

​




The idea is to use the CMM as a profilometer. Having located and measured the Sphere 7.55, I could zero on it and take a circle in the cross section ​shown in the second pic. Normally when the probe goes from reading PR 7.55/=3.775mm or whatever the actual DIA is there to something else, I could locate the point where the transition is happening. I am not familiar with T values but I suspect I could also use these somehow. The probe I have available to reach that point is a 6dia ruby ball that looks something like this:


​

Due to dimensions being so small there, I searched in the cad the point of 0.006mm where the PR will be bigger and the idea is locating this point and substracting 0.19 to find my transition value of 12.4

How would you guys handle that? Performing a scan and using arrays seemed to be to much for me as populating arrays in PCdmis seems to be a PITA. Thanks in advance for your inquires!
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  • Ok so I figured out another way that seems to be repeatable and maybe will help someone as a general idea down the line:



    I am scanning circles in a loop just above the transition each time descending 5 microns. The first few circles (average) are used as a reference for the real value of the cylinder just above the transition. Based on CAD I am having a 5 microns radial (or 0,01mm difference in DIA) when the edge of the transition comes in contact with my 6mm tip. At this point I can stop the loop and add the theoretical 0.748mm to the Z of the last circle. Not the perfect solution but with a somewhat big tolerance of 0,1mm, the CMM seems to be repeatable (in fact after 20 tries I have 20 same values which I don't know if it is a good thing or not rofl).
    ​
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  • Ok so I figured out another way that seems to be repeatable and maybe will help someone as a general idea down the line:



    I am scanning circles in a loop just above the transition each time descending 5 microns. The first few circles (average) are used as a reference for the real value of the cylinder just above the transition. Based on CAD I am having a 5 microns radial (or 0,01mm difference in DIA) when the edge of the transition comes in contact with my 6mm tip. At this point I can stop the loop and add the theoretical 0.748mm to the Z of the last circle. Not the perfect solution but with a somewhat big tolerance of 0,1mm, the CMM seems to be repeatable (in fact after 20 tries I have 20 same values which I don't know if it is a good thing or not rofl).
    ​
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