Curve around corners

[[To...]]

What is the best practice for measuring a curve that goes around sharp corners?

[[Ma...]]

I usually place one point in exact corner and make it 45° ( or any angle which suits there between faces ).

That will handle bad scanning ( mostly jumps ).
Inner corners i usually block evaluation for some points.
Also if you need that corner ( in your case ), then use smaller speed on some points ( make new segment with another strategy speed )

[[To...]]

While you're visiting my post, please remind me on how to do position of this irregular shaped pocket.  I always figured profile would handle that.  The above part has the following requirements below.

[[Ma...]]

That circle should mean "all around" - so not just one face, but all around that shape.

For TP - i would use either curve or that surfacce profile - use bestfit ( i would use only translation and rotation excluding in datum A axis )
Now place a point into nominal position as TP states and use element's alignment from that bestfit.

Now you can place TP on that point - it will move accordingly to bestfit.

[[To...]]

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That circle should mean "all around" - so not just one face, but all around that shape. That's why I called it "irregular shaped pocket"

For TP - i would use either curve or that surfacce profile - use bestfit ( i would use only translation and rotation excluding in datum A axis ) 
Now place a point into nominal position as TP states and use element's alignment from that bestfit.  The position is fully constrained. Doesn't that mean "no best fit".  2019 does not allow me to select a freeform surface or curve in my position

Now you can place TP on that point - it will move accordingly to bestfit.  see previous note

 

Edited Monday at 03:15 PM

[[Ma...]]

Profile is lock only for A - i assume perpendicular to A.
But TP is controled also by B and D and bestfit will be only for getting it's center. That center is then compared to ABD

Not for first profile callout.

[[To...]]

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But TP is controled also by B and D and bestfit will be only for getting it's center. That center is then compared to ABD  Sorry, I don't understand how to do what you're saying. Are you saying create a BestFit within the evaluation of the Curve feature with no translations or rotations? Then, how do I apply this to the point? Can you be more specific with the steps? 

Not for first profile callout. Yes, my question was only about position.

[[Ma...]]

To be safe you can make general surface and recall measured points into new one. This new one will have enabled bestfit with all translations and rotations -> save this bestfit.

Now this saved bestfit will serve as point element's alignment.

Let me explain it to you more deeply:

If you use a point alone, then you would have to somehow measure it, otherwise theoretical feature will report "0" as TP value.
So by using bestfit from surface profile will imitate real measurement, while nominal will be correct as from drawing.
So bestfit will move that point which is controlled by TP. By movement i mean like real measurement and you are comparing his real position to TED position in TP callout.

[[Cl...]]

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Personally I think the bottom tier should simply be surface profile to ABD that would evaluate form and position minus the deviations

from any basic dimensions. A heat map generated in CAD evaluation would tell you which way it's got to move to be within tolerance.

[[Ri...]]

Usually if they invoke Position in the lower tier then they are meaning Boundary Condition - look at Page 176 of ASME Y14.5-2009 (sorry I don't have 2018 in front of me). 

BUT, Boundary is usually invoked with MMC on the feature in the Positional control. That's because the Profile control is controlling the size, and the Positional control is only controlling location/orientation. 

I have a more detailed write-up that I could share if needed, but I would have to redact information before sending it. Here is a less detailed example that could be utilized for you (if you went the Boundary approach).

 

Regarding the tolerance – Calypso does not natively handle Boundary Conditions, so we have to set it up correctly ourselves. The tolerance is based on the following:

Taking half of the Profile Callout (0.015/2 = 0.0075) and half of the Boundary Callout (0.015/2 = 0.0075) or (0.020/2 = 0.010)

                                                               i.      The Boundary Callout of .015 to A B will have a tolerance of 0.015 (0.0075 + 0.0075)

                                                             ii.      The Boundary Callout of .020 to S will have a tolerance of 0.0175 (0.0075 + 0.010)

Setting the Shape of Zone to Inwards to Infinity

                                                               i.      This will report the largest deviation that adds material to the surface to ensure that the virtual condition has not been violated.

                                                             ii.      If the Profile result is 0.000, then all of the surface deviations are minus material and the Boundary Condition is verified.

Edited 18 hours ago

[[Ze...]]

Doesn't it need to be a feature of size to use position? And what is the shape of the tolerance zone for the position? 

The portion in the middle could be considered a width I suppose and control the location side to side. But the open-ended portion on the sides is what's confusing me. Isn't a boundary condition in this case just acting as profile? 

Sorry for all the questions. Just trying to learn something. 

[[Ri...]]

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 Typically yes, but there are cases where that doesn't apply. See the example I was discussing above. 

 

[[Ze...]]

Thank you for the diagram, Richard. I appreciate it! 

Let's see if I'm understanding this correctly. Since you can't use a material modifier on a profile feature itself since it's a surface control, the combination of the profile and position allows for the profile feature location to shift based on its material condition. Is that correct?

What about the lack of a material condition in the position callout from Tom's example? Does that essentially make it a composite/single segment profile since the tolerance zone is unaffected by a material modifier?