True Position + MMC for symmetry plane datums

[[Za...]]

Hello all,

I'm trying to add MMC to Datum D and Datum E per the print, but the box won't show up to add the MMC. Datum D and Datum E are both Symmetry Planes. Can somebody help me?


Thanks,

Zach

[[Me...]]

Calypso will not allow MMC to datum features unless they are coplanar to the feature you're inspecting.

🙁

[[Ün...]]

Hello,

You can view the attached sample file

[[Za...]]

Please sign in to view this quote.

Is this a shortcoming of Calypso or is this bad GD&T?

[[Za...]]

Please sign in to view this quote.

I'll have to take a look at that when I have some time. That seems a little advanced for my current Calypso knowledge and will probably take some time to figure out. Thank you for the resource 🙂

[[Me...]]

Please sign in to view this quote.

It's Calypso. If I'm not mistaken, the way it was explained to me is the complication with the equations. I can definitely say that I didn't trust what PCDMIS was telling me in regard to the same situation with True Position you're dealing with but it could've been my small amount of knowledge of that software...

[[Ri...]]

If the Datum is a Planar feature, it will not allow it. It will only allow the material modifier if the feature for evaluations.

[[Ca...]]

I could be totally wrong, but...

Features>Special Geometries>Symmetry Plane

Under the Nominal Definition dropdown, select Recall Feature Points. Select the Datum surfaces.

If you tick the Distance box, (Make sure to verify the Nominal distance.) and set the distance tolerances, you should be able to assign material modifiers to coplanar locations that use the slot datum.

MMC.png

[[Za...]]

Please sign in to view this quote.

Unfortunately, that's how I have the datums setup and it won't allow the MMC to be checked.

[[An...]]

Wrong dimensioning!

True Pos. horiz. direction:
0.015 (M) A D(M)

True Pos. vert. direction:
0.015 (M) A E(M)

Actual width of datum E:
constrained to datum D

[[Za...]]

Please sign in to view this quote.

Can you go into a little more detail? I'm not crazy sharp on my GD&T and I've only been programming on calypso for about a year and a half.

[[To...]]

Please sign in to view this quote.

That is the quote of the day......LOL

[[Za...]]

Please sign in to view this quote.

🤣 🤣 🤣

[[Ja...]]

You could scan the opposing surfaces that make up the slot, recall those scanned planes into 2 single points (one point per surface) and use those 2 points to construct a circle; this will give you a "feature of size" to invoke MMC and the center point of the circle will tell you where your mid-plane/symmetry plane is located relative to your alignment.

[[Ja...]]

Symmetry Point works with MMC/LMC but only if you restrict to X-axis only, Y-axis only, or Z-axis only, whichever is applicable. Unless you're using in a bore pattern, in which case it works with the diametral tolerance zone.

Personally, though, I tend to make theoretical circles that recall the XYZ location and use distance formula for diameter. These can be plugged into any TP using MMC/LMC without issue.

[[Je...]]

If your datum features used in the DRF are not features of size then a material condition modifier cannot be applied. If the feature you are using does not have a size associated then MMC will never show up as an option.

Someone mentioned the lack of MMC/LMC options in some DRF configurations. Generally speaking, with the current version of Calypso, all features must be within the same space axis. Essentially Calypso will calculate rotation/translation using MMC/MMB only in the same space axis as the primary datum and feature so long as all feature space axes are parallel nominally. This is not a hard fast rule but is the easiest to communicate in laymans terms.