Bolt hole circle pattern feature position techniques

[[Ti...]]

I'd like to begin by making a feature request in the software. I get position checks for cylindrical patterns a lot and the problem I have with creating an element group and getting the position of that group is that it ONLY let's you select ISO or ASME for the feature math type. Many times the cylinders that I measure are 90-120 deg of arc and it is well know that Maximum Inscribed and Minimum circumscribed math is not stable with less than 180 deg of arc.  Some of my cylinders will move and shrink drastically using ASME/ISO math types. So I cannot use that feature at all.

 

What I have been doing is using a top and bottom section cut then creating a centroid point from the section cuts. That is actually working well so far, but it isn't technically correct.

 

Below, you can see in the picture one other thing I would like to learn. How can I create a circle(so I can get a point for use in a position check) from all six Cylinder End points? I haven't figured it out yet.

 

Thanks.

 

Edited August 8, 2023

[[Ch...]]

To my point of view it is not good idea to use a normal position check to evaluate such an pattern.

My idea would be (of course this has to discuss with your customer/designer)

 

1) Use position tolerance under material requirement (you have to define a linear size, that is capable to tolerate the half cylinder; i would say gaussian or chebyshev is a good approach) OR

2) Use a surface profile (Yes I am aware that these will tolerate more than an simple position tolerance check)

 

As mentioned before you tolerate some things different than using a simple position tolerance check (therefore you cannot simply change this without your customer); but according to your screenshot you will get stable results, i hope.

 

Best regards

Christoph Schult

[[Ti...]]

well...I'm not sure what is going on I just did it again and it let me use geometry for the measuring principle for an element group.

I know for a fact that I've tried to do this 3x before and it always said I cannot use anything but ASME or ISO for a pattern/element group, but it just accepted me using geometry.

Sorry, I guess I was wrong, but I didn't learn anything new in the past 3 days, lol.

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I'm using this to give offsets in X and Y for machinists not for customer output. Therefore, I'm just looking for the best way to do it. I think I stumbled into the correct way using the 'centroid point' of the section cut. It is working very well on the shop floor dialing in our surface profile customer callout. The values I got correlated very well to several vision checks on multiple different machines so I am happy with what I have.

I just can't understand why it wasn't letting me use geometry last week and just now it let me.

 

 

Edited August 9, 2023