Concentricity Help!

[Underspec]

I'm measuring cylinder type parts with ID's and OD's then spitting out concentricity. My issue is that even after taking a plane and origin hits, my concentricity is way high. Roundness on the dimensions are around .0005. The part must be tilting a bit on the fixture. How can I compensate this tilt even after taking a plane to get an accurate concentricity dimension???


Thanks

[Schrocknroll]

Did you try using coaxility instead of concentricity since it's an axial feature?

You stated that the roundness is around .0005, but what are the axial locations of the cylinders?

[kbotta]

Are you outputting concentricity from Pcdmis?
the reason I ask is, it is NOT ASME Y14.5M-1994 compliant.
Pcdmis does not correctly obtain the results for this.
maybe you trying to get coaxiality?
Kev

[Underspec]

The parts are bored out cylinder type parts. I am using circles for the Inner / Outer diameters then spit out concentricity. If the part is tiliting then the X & Y would be off. How do I compensate for this? Should I use cylinders instead?

[kbotta]

That should give you coaxiality (I think) If you select one as a datum, then the other. It does not give you concentricity (per ASME).
Kevin

[J Temmen]

Try to level to either top and bottom ID cicles using a 3d line or the OD circles, that should take out any tilt from the plane.

[Underspec]

I can't create a 3d line using circles

[Underspec]

Can I create two circles in the Inner diameter and create a cylinder, use that as the origin but how do I adjust for the tilt? Level the Z?

[kbotta]

I beleive you level the axis of the cylinder, what ever direction you have it in.

[tking]

I beleive you level the axis of the cylinder, what ever direction you have it in.

Exactly! I think this is the best way.

TK

[James Doolittle]

What do you mean by "the part is tilting"? Do you mean the part is not parallel from end to end? What is the parallel for the part, and how is it defined on the print?

[Underspec]

So....

Plane @ top of Part...

Circle1 @ top of Inner diameter (bore), Circle2 @ bottom of Inner diameter...

Construct cylinder from Cir1 & Cir2...

Origin X, Y, and Level Z...

Circle3 on Outer diameter.....(OD is at the bottom of the part)

Insert Concentricity from Cir3 to Cir1...

That should give me an accurate concentricity??

[J Temmen]

I can't create a 3d line using circles

As long as the circles are at different heights you can create a 3D line, which represents the same axis as a cylinder.All you need to do is LEVEL to the axis and call it X,Y origin.

[tking]

Absolutely. You're there man!

TK

Concentricity of circle to CYLINDER.

TK

[Underspec]

The part tilts because of the way it's set up on the surface plate. The plane doesn't seem to compensate when doing concentricity between the circles.

Imagine an open can sitting on a plane. You have to take the bottom outer diameter as the datum. Then take the top inner diameter and find the concentricity.

Because the bottom outer diameter needs to be measured, I have to sit it on something smaller than itself (a gage pin). A vblock won't work because of outer features etc.

Anyway, PCDMIS should be able to compensate for this tilt when doing concentricity...