Cannot get bonus positional tolerance on a sphere

[[Ti...]]

Is there a way to apply a positional tolerance to a sphere and use the bonus MMC tolerance? I don't think GOM allows you to use a GDT size check to get the bonus tolerance.

If not, is it possible to do this in the user defined checks? I still don't know how to use those yet.

 

Thanks.

[[Ch...]]

Hi,

Linear size on spheres is possible since GOM software 2021. In addition MMR on spheres is a new feature of the GOM Software 2022. Therefore please update to GOM Software 2022 to use this feature.

 

Best regards

Christoph Schult

[[Ti...]]

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Thanks, when did 2022 get released? 

[[Ch...]]

To my understanding GOM Software 2022 was released one week ago. 

[[Ti...]]

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We cannot update to 2022 for various reasons right now, one being we are told to hold off until hotfix 1 due to our CT. 

I decided to create a user defined measurement to calculate a check based on a zero positional tolerance which requires MMC calculation. Quite easy once I learned how to use the user defined section.  I basically create a check on the spherical position using dXYZ using no tolerance. Then I create a check that just doubles that value to get it from radial distance to diametrical distance('User defined Position'). Now I have the absolute value of the diametrical deviation. Then I define a check of the diameter deviation of the sphere from the MMC condition. Then I create a check of the (diam deviation value from MMC) - (2*dXYZ).  If that value is positive the part passes this check.

I noticed in 2022 it REQUIRES you to use ASME/ISO to use the softwares MMC calculation due to it being a GDT check. My approach can bypass this b/c it doesn't require the user to use maximum inscribed. My method allows us to continue to use a least squares/guassian filter on the sphere and still produce a valid check of position based on MMC.

We all know that max inscribed is the proper method for measuring an internal feature, but we are not dealing with hard gaging, we are dealing with imperfect data, so sometimes it may be more beneficial to go with a gaussian fit. Therefore, I think my method is a rather important way to get this done not only in 2021, but also in 2022 if someone doesn't want to be required to measure the sphere as maximum inscribed.

I'd like to hear your thoughts on my approach.  Below is my data, using the max inscribed method so I could test if my results replicated the 2022 results.

Thanks.

 

 

 

Edited October 21, 2022

[[Ti...]]

I cannot edit my post....For some reason now I can use a non-GDT gaussian approach to do the 2022 positional check, but it starts measuring things incorrectly in my opinion. For one thing, if you use my manual method it will retain the 2 or 3 sigma approach and backing off edges by .005". But with the mandatory GDT linear size approach you must use GG which is still gaussian but hits all the points it seems.  I'm rather confused as to how this has been put together. I'm getting same data when using my method and max inscribed, but when I use the 2022 positional data and deviate from anything but a GDT measurement method I get weird data.

Edited October 21, 2022