[Yu...] Posted May 30, 2022 Share Posted May 30, 2022 The difference between the maximum and minimum distances (72 points in total) from the center of the circle to the points created on the outer circumference is 2.582 mm. 2.283 mm when roundness is applied to a circle created from a cross section. Why does it make a difference... Link to comment https://qualityforum.zeiss.com/topic/991-radius-method-and-gd-t-error/ Share on other sites More sharing options...
[Ch...] Posted May 30, 2022 Share Posted May 30, 2022 What kind of circle (i.e. what fitting method you are using) for your comparison? GD&T checks inside the GOM software using only the point data from the fitting element and computes all needed fits to be in accordance to the default of the corresponding ISO standard. That means if you are using another fitting type for your circle than it mentioned as default in the standard you will get different results. Link to comment https://qualityforum.zeiss.com/topic/991-radius-method-and-gd-t-error/#findComment-3069 Share on other sites More sharing options...
[Yu...] Posted May 30, 2022 Author Share Posted May 30, 2022 The fitting circle (Gauss best fit) is used. The center used for the two-point distance from the center to the outer circumference uses a fitting circle. Link to comment https://qualityforum.zeiss.com/topic/991-radius-method-and-gd-t-error/#findComment-3071 Share on other sites More sharing options...
[Yu...] Posted May 30, 2022 Author Share Posted May 30, 2022 Please sign in to view this quote. Please sign in to view this quote. Link to comment https://qualityforum.zeiss.com/topic/991-radius-method-and-gd-t-error/#findComment-3073 Share on other sites More sharing options...
[Ch...] Posted May 30, 2022 Share Posted May 30, 2022 This explains the difference: The default in accordance to ISO 1101 is a chebyshev circle. If you use this you should get the same results. Link to comment https://qualityforum.zeiss.com/topic/991-radius-method-and-gd-t-error/#findComment-3077 Share on other sites More sharing options...
[Yu...] Posted May 30, 2022 Author Share Posted May 30, 2022 Is the roundness calculated by Chebyshev Best Fit in the default state of GOM Inspect? Link to comment https://qualityforum.zeiss.com/topic/991-radius-method-and-gd-t-error/#findComment-3079 Share on other sites More sharing options...
[Ch...] Posted May 30, 2022 Share Posted May 30, 2022 As I mentioned before, it is the default in the corresponding standard and therefore it is the way how a roundness check is internally computed in the GOM Inspection software. Link to comment https://qualityforum.zeiss.com/topic/991-radius-method-and-gd-t-error/#findComment-3083 Share on other sites More sharing options...
[Yu...] Posted May 30, 2022 Author Share Posted May 30, 2022 I understood your explanation perfectly. Thank you for your uncomplicated explanation. Link to comment https://qualityforum.zeiss.com/topic/991-radius-method-and-gd-t-error/#findComment-3089 Share on other sites More sharing options...
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