Datums A&B

[[Ra...]]

Hello,
I'm new with cmms machines. Thanks for your understanding.

When a drawing calls for datum A and B, should I use these datums to do my alignment or not?
See the drawing below.

Thank you,

Datums.PNG

[[An...]]

You absolutely can use your datums as base alignments. It generally is a good practice to double dip your base alignment with datum features.

Note it is still recommended in call outs that require said datums to plug those in individually per the characteristic instead of just using the generic Alignment option.

[[Ma...]]

Don't forget to ask which element is used for base B - i think you can not place bases just on axis.

[[Da...]]

And if the part is symmetrical, check both/all sides.

[[To...]]

What feature is the Datum B feature?

[[Ro...]]

I use datums when they are easy to get to, and easy for subsequent parts to be loaded and ran without doing manual.
I have 1 customer that in almost all parts, the B and C Datums are 2mm Cylinder and Slot, so for those parts I never use datums in the base alignment.
Also I prefer not to use "bottom planes", or features requiring multiple probe angles in base alignments.
Additionally, If a base alignment requires a Stylus system change, i try to figure alternate surfaces to use for base.

[[Je...]]

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Hi Ramiro!

Welcome to the exciting world of Coordinate Metrology Programming. You've come to the right place to learn more about Calypso and CMM. I also recommend attending an official Zeiss Calypso basic course if you ever have the opportunity to do so.

To answer your question:

Whether or not to use datum features in your base alignment is not as important as this question:

• "Will the features I am using in my base alignment provide a stable setup to allow the cmm to find and probe the features of interest on my part?"

Keep this in mind when thinking about alignments:

The purpose of a base alignment in Calypso is primarily to facilitate . and only secondarily to facilitate .[/color] of characteristics.

The purpose of subsequent alignments in Calypso is primarily to facilitate .[/color] of characteristics and also can further refine . of features.

My go-to workflow is to use mostly touch-point strategies in stable features on the workpiece and then program robust scanning strategies into the features of interest, which will include datum features as well as controlled features.

Per your drawing, the Datum A feature may indeed work well for the "spatial rotation" feature in your base alignment, and the Datum B feature may work well for the planar rotation (clocking)

I hope that helps. Welcome, and feel free to contact me or post on this forum anytime you have questions. There are some awesome, knowledgeable people here who have helped me out more times than I can count.


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[[Ra...]]

Thanks to all of you.

[[De...]]

It also depends on your procedures at your company so check those. I worked for one company that require the datum features to be used in the base alignment. While I don't agree with the decision it is something I need to follow. A case could be made on a case by case basis to deviate from the procedure, but that needs to be approved by the customer.