Profile @ MMC

[[Ri...]]

Take a look at this drawing that I made. It's not the actual part that will be inspected, but I made something to represent the part. 

Profile_3-13-25 Drawing v1.pdf

I'm not certain how to even begin to wrap my head around this one. ASME Y14.5-2009 page 176 kind of gives an example of something like this. 

It says, "For an external feature, the boundary equals the MMC size of the profile plus the positional tolerance, and the entire feature surface must lie within the boundary."

I think in this case the 0.15 Profile requirement would set the MMC allowance of +0.075 from the True Profile + the Positional/Profile tolerance of 0.15. 

BUT that is if it as MMC, so what value are you actually using to calculate the deviation from MMC? 

I'm all kinds of confused, and I'm looking for some assistance on how to interpret this, and how to evaluate this. Any and all help is greatly appreciated. 

 

Thank you. 

 

[[Ch...]]

I dont believe MMC is allowed on profile features only on datums - thats what profile is for, to control size, etc...

[[Ri...]]

Yeah. I think they are intending to do what is shown on Page 176 of the standard. 

[[Th...]]

Ripping that page out of my hard copy of 14.5 like the Monty Python bookshop sketch so I can pretend it doesn't exist. Chris is right that you can't directly apply material condition modifiers to a profile, which is why the combined control uses a position instead for the lower FCF. I think your understanding of the boundary is correct. Can't tell how you would evaluate with an actual position characteristic, so I would use another profile, unequally disposed, with the outer boundary set to whatever pseudo-bonus tolerance is allowed. You have an outer boundary of +0.225 to start with, and then I guess you can best fit the curve, find your most plus-material point, find the distance between it and your floating profile boundary, and add it to that 0.225, and that's your upper limit.

[[Ri...]]

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That's what I was thinking as well. Sometimes I look at drawings from customers and just smile and nod. Lol. 

[[Ma...]]

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 in your sketch it seems, you can recall points into circle - then you can use MMB. No option for MMC for curve so last one should be evaluated as circle too.

I am curious how to correctly implement that ASME example in Calypso - but i understand that concept, just i would use normal curve with unequal distribution.

[[Ri...]]

Apparently the concept as shown in ASME Y14.5 is the same as the BOUNDARY condition which I have seen plenty of times. I have requested this be added to Calypso, but I haven't seen any feedback. 

[[Br...]]

I would just treat that as a composite profile tolerance and forget about the MMC. It doesn't apply to profile tolerances. If you want to treat it like the irregular feature of size from Y14.5, you can.  Position @MMC weather it uses a profile tolerance to control size of an irregular feature of size, or a directly toleranced size dimension for a regular feature of size, is a single limit boundary.  So what you can do is make a 2D curve measurement and do your profile tolerance to no datums for the size requirement. Then make a copy of the curve feature, open it, select the nominal data dropdown>Nominal Geometry Manipulations>Modify Nominals>in vector direction tab>Translation. Then with the translation radio button ticked, take half of the size tolerance and add it to half of the position tolerance and put that number into the "Length" box. This will make the nominal curve the MMB or inner boundary from that figure you shared. Now you can recall points from the measured curve into this MMB curve. You now can use the MMB curve in a profile tolerance. From here the Profile characteristic should have a zone of either Inwards to Infinity or outwards to infinity depending on if your feature is an external feature or an internal feature. This satisfies both requirements. Its a lot, but It's the only way I know how to do it.