Is this important?
I would imagine so, considering all the parts have datums, but what is the difference from, say, setting a point as Datum A and dimensioning a feature to Datum A, and setting a point and dimensioning a feature to said point?
So the general consensus is I should set features as datums, if anything for posterity's sake, considering I take more than a single point to define a couple features.
Works for me!
So a datum definition question in and of itself:
I have a rotary table that clamps down cylindrical parts with a flat face. This face is usually datum B, my Y origin. Datum A is the OD of the cylindrical part itself, which I level to. Datum C is undefined, so I set up points and lines to generate a rotation vector.
Would I be better off defining these features as Datums? Almost all measurements use at least one of these features in its' construction.
Also along these lines, I'm having an issue with Datum B...
I am uneasy with the rotary table and subsequent calibration; I'm not seasoned in PC-DMIS, rotary tables, machining, or anything related to any of them in any way. So I do not trust it's accuracy.
When it rotates to 45°, I am pretty sure it's actually 45°. But I'm not sure how tilted the part is in the rotary table, if that makes sense.
Say I want to generate a plane as Datum B. To do that I would want to rotate to each of the relevant vectors (every 30° or 45° typically) and take a point on the face, then construct a plane out of these points.
How can I be sure that the Y axis is level? I would imagine if the part is tilted sideways a little in the rotab, a point on the left side would be farther away than a point on the right, for example.
Would I be better off trying it and reporting the flatness of the plane?
Is using a single point for a datum such as a Y axis insufficient?
Is using a singe point at each rotation and constructing a plane going to be insufficient due to part sway/tilt from the chuck?
Is there a way to test this?
Is this better asked in a different forum?
Who knows?
So the general consensus is I should set features as datums, if anything for posterity's sake, considering I take more than a single point to define a couple features.
Works for me!
So a datum definition question in and of itself:
I have a rotary table that clamps down cylindrical parts with a flat face. This face is usually datum B, my Y origin. Datum A is the OD of the cylindrical part itself, which I level to. Datum C is undefined, so I set up points and lines to generate a rotation vector.
Would I be better off defining these features as Datums? Almost all measurements use at least one of these features in its' construction.
Also along these lines, I'm having an issue with Datum B...
I am uneasy with the rotary table and subsequent calibration; I'm not seasoned in PC-DMIS, rotary tables, machining, or anything related to any of them in any way. So I do not trust it's accuracy.
When it rotates to 45°, I am pretty sure it's actually 45°. But I'm not sure how tilted the part is in the rotary table, if that makes sense.
Say I want to generate a plane as Datum B. To do that I would want to rotate to each of the relevant vectors (every 30° or 45° typically) and take a point on the face, then construct a plane out of these points.
How can I be sure that the Y axis is level? I would imagine if the part is tilted sideways a little in the rotab, a point on the left side would be farther away than a point on the right, for example.
Would I be better off trying it and reporting the flatness of the plane?
Is using a single point for a datum such as a Y axis insufficient?
Is using a singe point at each rotation and constructing a plane going to be insufficient due to part sway/tilt from the chuck?
Is there a way to test this?
Is this better asked in a different forum?
Who knows?
If you use legacy, (as you answered the "left" picture above" then defining datums is pointless, as you won't use them. If you are aligning to your datums and using legacy dimensions, then you are already "defining" the DRF (Datum Definition is a particular thing in PC-DMIS, it has a meaning, that is not how you are using it).
I'm not going to answer rotary table questions, since I never use one.
Based on the answer to my question above, you do not need to use the PC-DMIS function "Datum Definition". However, when you say you've "seen" the other window, what do you mean? I'm asking because if you go to Insert...Dimension...Location, it looks similar to the left window, but if you went to Insert...Dimension...True position and it looks like the one on the right, you do have Xact measure turned on.
If you go to Insert...Dimension, and look at the very bottom of that sub menu, is the a check box next to "Use legacy dimensions"
You do still need to do a proper alignment, however. As an aside, "Datum Definition" does NOT create an alignment, it only defines what the feature the datum letter is.
