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Perpendicularity of cylinder

Hi everyone,

I am new to the forum and by searching the topics I couldn't find the answer to my question.
I need to measure the perpendicularity of a hollow cylinder according to its planar surface used as datum. I have used two different approaches in this regard, but I obtain very different results.
in the first approach, I measure 5 circles at different levels along the cylinder height [using auto circle feature] then I construct a cylinder from these 5 circles [constructed feature] and finally I chose Perpendicularity Dimension to measure the perpendicularity.
in the second approach, I use Auto Cylinder feature[using Adaptive Cylinder Concentric Circle Scan] to construct the cylinder geometry as showed in the attached image, where the scans are performed at the same positions along the axis compare to the previous approach. by measuring the perpendicularity according to the same datum as the first approach, this time I get perpendicularity values which are much worst than the previous case. [in first case I get 0.006 mm while in second case it is 0.098mm].
I would appreciate if you can help me find out which of these two approach is correct, or is there a better solution to measure the perpendicularity precisely?

Thank you in advance.

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  • I was wondering what could be the reason for this differences...


    One factor may be the form of the cylinder - conical, banana curved, hourglass, non-circular etc. etc. - and depending on the form, it may be very important where you put the hits, and that you use enough hits to actually catch the form error. A rule of thumb is to increase the number of hits and cuts until the form error doesn't increase anymore, then you know how many you need for that particular specimen...

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  • I was wondering what could be the reason for this differences...


    One factor may be the form of the cylinder - conical, banana curved, hourglass, non-circular etc. etc. - and depending on the form, it may be very important where you put the hits, and that you use enough hits to actually catch the form error. A rule of thumb is to increase the number of hits and cuts until the form error doesn't increase anymore, then you know how many you need for that particular specimen...

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