Concentricity headache

[[SH...]]

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I tried scanning according to zeiss advice, but I got form error 47 cylinder 5micron and 118 bore 14micron. But my 118 bore co ordinate value shift is high compared to zeiss.

I will try in different speeds and force.
I think it change with temperature, 118 bore wall thickness is very less. Zeiss engineer might kept the job in AC for long hours..

[[Jo...]]

A few thoughts: I haven't read any mention of how the circles are being evaluated. An LSQ evaluation of the circles will yield a different center than a maximum inscribed. These need to be the same between you and Zeiss. Also, 8 points per circle and 3000 points per circle is profound so that by itself will yield a different result. Since concentricity is measuring the location of centers of diametrically opposed elements, exactly where your probing points are taken will affect the result. Adding datum references that are not on the print is never a good idea, even if it improves your result. I agree that an excessively short axis is problematic but that should have been addressed on the design side, not the inspection side. It is VERY likely that concentricity is not the right callout for this at all. It was eliminated from Y14.5 for a reason. Position or runout is probably the correct callout for this but since concentricity is what's there, you're stuck with it.

[[SH...]]

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Your point is really appreciated, I will try with maximum inscribed cylinder.
I have attached my reference sphere position using tip three and tip five , which is used for calculating concentricity. Only 4 micron difference between the coordinate values, can be reason ??
Tip three directed towards x plus direction, and tip five towards x minues direction.

Also I will ask to zeiss engineer about their evaluation.

IMG20200819072242.jpg

[[Da...]]

How is the part fixtured, It sounds like its aluminum, and thin walled. It doesn't have a lot of flat surfaces...is there a chance you are warping if in the holding device ? Is there a chance that in trying to clamp the part lightly so as not to warp it , it's able to move a bit?

[[SH...]]

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Part is located in the fixture, yes it is aluminium alloy ADC12. There is no chance of wrapped, I locate inside the thread ,it doesn't move while checking. 118 bore wall thickness is very less. Usually I check the job after soaking.