Position of Slot

[[To...]]

Using the sketch below, let's assume the Datum D Cylinder is positioned to ABC.  And the slot width (E) is positioned to AD.  I am using a Symmetry Plane to measure the width.  For this example, let's say the slot length is not very long, leaving very little plane to measure.  Let's say the tool that cut the slot had some deflection and caused the slot to be slightly skewed.

 

Here's  my question. For the DRF ADE, will the rotation around D be controlled by the angle of the symmetry plane? In other words, (1) will the symmetry plane rotate about D until it is parallel with with the X axis or (2) will it rotate about D until the mid-point of the symmetry plane is at Y zero to D?

[[Ma...]]

If you use something like plane, then it wil do your 1. pic.

If you use something like point, then it will do your 2. pic.

[[Ch...]]

Tom, excellent question, I've found myself asking similar in very similar situations. My understanding is Calypso can only rotate to a point and doesn't handle 3D tertiary features well. If this were a single plane for example it would rotate to the high point of material in the real world. I'm assuming it does something similar based on Symmetry Plane vector and evaluation (OTE/LSQ).

I would get Zeiss official statement on this one to be safe. I do know that if your CAD model and setup does not have the slot directly on X or Y of the CMM, there are some drawbacks there, and it may not be advised.

 

Good luck, let us know how you make out.

 

 

[[Ky...]]

Martin's comment is correct, at least as far as I know. Calypso works just fine with 3D tertiary datums controlling the orientation fine to my knowledge, but it sets the axis direction to be parallel with the datum, so it doesn't necessarily "rest" on any of the data from the feature in question.

[[Ri...]]

Have to be careful with projection error here too. If the plane is short and far away from the center, you will not like the results you get. There's an argument to be had that in that case you should probably just use a symmetry point instead, but that's neither here nor there. 

In the cases where I was forced to use a plane, I've had solid success leveraging Free-Form to create the correct alignment for me. 

[[To...]]

If I am not mistaken, ASME indicates that pic 2 is how it should be done.

[[Ma...]]

But this would be for MMB. I thought you were talking about alignment and not datums for callout.

[[To...]]

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No, MMB would allow for movement. When a Datum Feature is RMB, the Datum Simulator is fixed at nominal location and expands to fit actual size.

[[Ma...]]

If it's for ASME, then ok - i have no idea how it's described there.

I will try something tommorow at work how it would rotate on our setup.

But on this view i would stick to mid point - from that view it could mean in any height of cylinder 🙂
God bless, that it's machined mostly correctly so you won't notice mismatch 🙂

[[Ma...]]

I've tried out some scenarios and had no luck - i didn't achieve your picture.

Maybe in simulation or real data can show more. ASME is still big unknown for me.