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Originally posted by AndersI
I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.
Translate to nominal center of radius and take Radial Points along the surface. Treat basically as a profile. Report MIN MAX of radial distance. Easiest way. Or, use RAD Gage.
Bill Jarrells
A lie can travel half way around the world while the truth is putting on its shoes. - Mark Twain
OK. Polar radius for 10 points.
My RAD is 100'' ant tolerance .002
What about probe compensation? If touching points, it should be ON - must calculate approach vector for no CAD is present.
OK. Polar radius for 10 points.
My RAD is 100'' ant tolerance .002
What about probe compensation? If touching points, it should be ON - must calculate approach vector for no CAD is present.
Well, what I typically do is go ahead and rotate my coord system until my first hit is directly in a particular axis (usually X) and hits exactly where I want it to on the part (hope that makes sense). Then I do a pattern paste for the other points and PC DMIS will take care of all the other vector comps for me with no need for calculations. With 0.002 tolerance the fools in engineering should have put a profile on such an arc. Do you have any location tolerance for the arc? If the arc is not exactly where it is supposed to be you can get some cosine error on your comps. This is not usually a worrisome consideration but with a 100" Radius and 0.002" tolerance it sounds like the Engineering Group for the part needs some help if it isn't controlled any better than this.
Bill Jarrells
A lie can travel half way around the world while the truth is putting on its shoes. - Mark Twain
Short note about this topic: I think that in fact all described approaches are undoubtly correct... But if you are asked about the radius (single value) and there is no one that wants to hear your perfect reasons... What I miss in PC-DMIS, is calculating the circle with fixed co-ordinate position, which is a common approach for example in QUINDOS or CA. You just set the nominal position as fixed and let the software calculate the radius of a circle with that centre. A little bit like "Fixed radius", but the opposite one. Then it is up to you to set the form error to some sensate value and output the radius you are asked for...
Short note about this topic: I think that in fact all described approaches are undoubtly correct... But if you are asked about the radius (single value) and there is no one that wants to hear your perfect reasons... What I miss in PC-DMIS, is calculating the circle with fixed co-ordinate position, which is a common approach for example in QUINDOS or CA. You just set the nominal position as fixed and let the software calculate the radius of a circle with that centre. A little bit like "Fixed radius", but the opposite one. Then it is up to you to set the form error to some sensate value and output the radius you are asked for...
Reporting MIN and MAX PR from fixed point is same result as you describe. Yes, it is a workaround but the result is the same as you describe.
Too bad PCDMIS doesnt have radius best fitting so that you could take the points and best fit the data to the known radius curve without the fixed axis of the radius point method.
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