Flatness with Datum Targets

In this Question Line video, Jason answers questions regarding datum targets and applying flatness and profile of a surface.
Interested in learning more about Print Reading or GD&T? Check out more of our free GD&T resources here: download.gdand...
#datumtargets #flatness #profileofasurface

[@alanchang0118]

If datum targets are applied, how to simulate datums during inspection via CMM. Should fixture must be used? Is there any option by CMM software or programing?

[@AlexLapugean]

Usually a jig. Most CMMs I've seen do not have datum target simulators. Maybe more high end ones do ...
Or 3D scan measurement software, like GOM Inspect, do have ways to simulate datum targets.

[@AlexLapugean]

Yes, it is obvious that when a datum plane is define by 3 datum target points, flatness is meaningless because they will always form a perfect plane. however, when the datum targets are surfaces instead, with meaningful areas, or you have more than 3 datum target points, you will have a flatness mismatch between a simulator and the real part.
Is there a way to impose a restriction to the deviation of those multiple points or surfaces from a perfect plane, without qualifying the entire surface? (for example, you have four contact points, and you want to make sure that with any 3 points in contact, the fourth point will never have a larger gap than a certain value)

[@Gdandtbasics]

That's a great question, Datum target points, regardless of how many or where they are, will not ever "control" any aspect of size, location, orientation, or form. You can however still apply a form control to the entire surface, or portions of that surface as you mentioned and we show in this example. THat would be the only way to control specific form deviations in this scenario.