Derived median plane

[[SH...]]

For checking this flatness should I go for symmetric plane or symmetry construction?.

Perfect form required at MMC condition, but here print says at MMC flatness is 0.3 so it is violating rule number 1?.

What should be the size of snap gauge, 20.2 or 20.5?

IMG_20210607_215314.jpg

[[Ma...]]

Is this even valid?

[[Cl...]]

This is wrong, MMC cannot be applied here. Use a symmetry plane (recalled points from both planes)

[[SH...]]

I think there may be some exceptions to rule number one. I have to verify the standard.

[[Ro...]]

A Derived median plane is a feature of size and can have MMC. The MMC callout overrides Rule 1.

[[Jo...]]

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Could you use profile of surface for second plane back to Datum A ? bilateral tolerance of .4 . Then flatness of both planes not to exceed .3 RFS . I think that would satisfy drawing intent.

[[Da...]]

I've never heard of taking points from both planes and using a flatness callout for the resulting median plane. How does that work?

[[Da...]]

Flatness is form only, no datums, no modifiers. I think its safe to say that the placement of the flatness on the dimension, and not attached to one surface is also a mistake. The way calypso makes symmetry features it will not have any form errors, If I'm not mistaken ?

[[Ma...]]

I found some article for this
https://www.linkedin.com/pulse/flatness ... dan-pepin/

[[Cl...]]

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I thought a symmetry plane could be used to evaluate flatness.
Your right, doesn't work. Calypso won't allow you pull the feature
into the characteristic. Although It does work in either a form & profile
characteristic.

[[Da...]]

Martins article sheds some light on the idea, but at the end, the correction uses the flatness callout on one surface.

[[SH...]]

So, in CMM can't check this flatness?.

[[Me...]]

Just simulate a functional gage by reporting the width of the outer tangential symmetry plane. The reported width must be less than or equal to the virtual condition. If you’re using the latest release of Calypso, you can report the local size using the 2-Point distance characteristic set to “LP”. Doing each of these will “satisfy” both requirements.

If you must report an actual flatness value, then you’re going to need to create a rather large number of midpoints and construct a plane from them in order to use the flatness characteristic.

[[Ri...]]

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