Help with true position diamter

[[Ra...]]

 

Hello, I'm new to working with CMM and Calypso 2022.

I need some guidance on selecting the correct option in Calypso to inspect the true position of this part. Depending on the option I choose, the part either passes or fails the inspection. I’m not sure what the best approach is.

Could someone please help me understand which option to use, or advise me on how to properly inspect the true position for this part?

 

See the following screenshots. 

 

Thank you, 

 

 

 

 

 

 

 

[[Ma...]]

Datum C should be a feature which allows MMB - so perhaps symmetry plane or symmetry point ( it's not the same as symmetry from construction menu! )

[[Ri...]]

The legacy GD&T will not allow you to use MMB, even with a Best-Fit Pattern. You will need to use the new GD&T engine to evaluate this. 

Pay attention to which standard you use. 

[[ni...]]

like on the draft the nominals of the TP should be 19 and 3, the datum C is the center axis of the oblong.

[[To...]]

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Because the Datum C identifier is in-line with the dimension line, it implies that Datum C is based on both sides of the slot.  Symmetry Plane, as pointed out by others, is the correct feature.

Edited April 24

[[Ri...]]

I apologize, I didn't see the version. 

You will most likely need to follow these instructions if you truly want something similar to datum shift. 

https://portal.zeiss.com/knowledge-base?id=522754

 

[[Da...]]

As an aside, I notice you are using a glue gun for part mounting. I highly recommend you stop using glue, and instead get a smallish toolmakers grinding vise, one with small steps on the edges to hold small parts like this. The C datum is the location of the slot, with datum shift resulting on width greater than the  smallest toleranced width.

Generally, a GD&T setup is based on the "3-2-1" alignment type, or more correctly "plane-line-point". Your primary in this case is the bottom of the part, which can't be directly measured on your setup (but could be, if you use a grinding vise as I mentioned). This creates the z=0 origin, plus fixes the roll and pitch rotations of said plane. 

Secondary would be the LINE created on the right side of the part. You entered a planar feature, but when creating this alignment, the machine will use a "resultant line" calculated from the plane. I assume that this is will be parallel to the primary datum in Calypso (in days gone by sometimes CMM programs would fit a line at some odd angle and screw up your vectors). This will fix your x=0 origin and y-axis orientation, and fixes the yaw rotation to the Y+ axis.

Your tertiary would be the center point of the width of the slot, with MMC variation resultant from the actual slot width measured. It seems you created a planar feature of this based on the midpoint of the 2 planar surfaces of the slot, from which the Calypso software will create a resultant point based on the "center-point" of this plane.

Since the only datum shift is on the tertiary datum, and that only affects the Y-axis with no rotational component, you CAN apply datum shift after measurement if all you have is an RFS dimension. This can be added afterwards only to the Y-axis data, but you'll have to do that manually. In years past, I would just mark-up a printout of the RFS dimensions, and add a note and maybe also a spreadsheet showing the extra bonus based ONLY on the tertiary datum. If it actually passes on the simple RFS alignment, you don't need to do anything else.