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GD&T roundness not possible for circle


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I applied a GD&T roundness check to my cone. This was succesfully done, see figure in attachment.

However, When trying to do the same for a circle constructed from this cone, the software mentions "this gd&t tolerance cannot be applied to all selected elements."
I create the circle using 'Construct Intersection Cylinder/Cone'.

It is not clear to me when GD&T roundness can be applied to a circle and when it cannot.



Schermafbeelding 2021-12-09 163551.png

(updated figure)
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This creation command creates a purely geometric circle, which cannot be checked with GD&T tolerances (and is perfectly round by definition).

You need a circle that is defined on a "real" section of the mesh of the cone with a plane:

- define a section plane, e.g. from the cone axis and a point

- Restore the selection of the cone (right click the cone and choose "Restore Point Selection")

-Call command Construct->Section->Single Section.. and choose the defined section plane

-Create a fitting circle on the resulting section and check it for roundness

(If you start in the nominal, you will have to apply the appropriate measuring principles.)

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Hi Christian,

Thank you for your reply. That worked indeed.

However, you mentioned that the creation command ' Construct Intersection Cylinder/Cone' creates a purely 'geometric circle'. But when later on actual data is applied, I assumed the constructed actual circle should be allowed a circularity check.

Anyway, I was able to circumvent that problem following your steps. Much appreciated!

Kind regards

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  • 1 year later...

Hello Christian,

I encountered a similar problem with GOM software. I need to create a plane by using two holes and one plane(with using perpendicular plane function) and after it is created all GD&T checks for the created plane  disappeared. I solved the problem with creating the plane as nominal and creating an actual section by using that . Finally using  section data with fitting plane function,  I can activate all GD&T checks.I thought the reason of the problem could be same but still want to ask you again.



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