Leveling and Z-origin on slanted Datum A

[MattR]

Hey guys I have a question. How I level and z-origin on a slanted datum? It's a plastic part where datum A is slanted 20 degrees with respect to blueprint coordinates and datums B & C are the holes on that surface. Do I offset angle 20 degrees? Here is rough sketch:

print1.JPG

[Quality ish]

What I'd do is:

Touch off the plane in as many points as I think are required (flatness call out?) That's datum A. My Z plane. I'd touch off the two cylinders and construct a line between them. I'd rotate to that line, and probably call cylinder B my origin, as it's the secondary datum and C the tertiary. That'll orient the part. Figure all your measurements off data A, B, and C from there.

[MattR]

But don't I have to compensate for the skewed plane?

[Quality ish]

If you're intent on using the CMM to generate a comprehensive report, you're going to have to calibrate probe angles which would allow you to touch off the inside of the blind holes to show their perpendicularity to plane A (if that dimension is called out), or find a way to fixture the part so that plane A is level with the surface plate. Otherwise, you're in danger of shanking (that is, touching the edge of the hole with the shank of the probe, rather than the ruby at the end), which would give you erroneous measurements.

If you're just looking to see if the part is acceptable, you might touch off each datum, align accordingly, and put the largest pins that will fit properly in the blind holes, and touch off the pins as cylinders and construct circles using each cylinder and plane A. That would locate those holes on the surface of the plane. In that case, I don't believe that you'd need to compensate for the angle at all. the CMM will rotate the view so that you're looking at plane A as your Z plus, and you could dimension the circle locations accordingly.

[Rich P]

if you want to level the part to the machine load part on a sine plate set to 20 degrees

[MattR]

Problem is I don't have one. So I'm trying to figure out other ways in the software how to align this part.

[Schrocknroll]

To level surface [A] measure a plane on the surface and in the alignment, select that plane and level Z to it.

If you need to measure other features that are in the blue print coordinates you mentioned, then you would need to rotate the alignment 20 degrees.

[MattR]

Thanks for the info! Which axis do I rotate to? Z-plus?

[louisd]

The alignment command within pcdmis is easily conjured with CTL+ALT+A, if that was what you were missing.

[MattR]

Well I was looking how to level skewed plane that part I'm not so sure of.

[MattR]

I was wondering if I have to compensate for the 20 degrees in the alignment utilities window.

[Schrocknroll]

Thanks for the info! Which axis do I rotate to? Z-plus?

I was wondering if I have to compensate for the 20 degrees in the alignment utilities window.

Level [A] to Z plus. Select [B] then [C] and rotate to X plus about Z plus.
Then rotate -20° about X plus.

Where you set the origins is up to you. I would guess Z origin would be set on [A], X and Y would be on [B]. Both being set before the 20° rotation. However your drawing origin looks to be on the bottom of the part opposite [A], but if [A] is supposed to be the primary datum, you would need a basic dimension to offset from [A] to get it to the bottom and still be located from [A].

Disclaimer: All of this is guessing based on a hand drawing sketch. Without all the print and drawing notes none of us can be certain how this should be aligned. These are just suggestions based on a little information given. Ultimately it's up to you to understand PC-DMIS and the drawing to make the final programming decisions.