Another instance of my programmer and I butting heads. First off, I want to ask... Is an alignment needed to measure the concentricity of 2 circles? If so, can a proper alignment be made with paint on the plane that we are leveling the part to? He says that even with paint (very uneven paint) on the part, the concentricity will be accurate. Again, be gentle.
You don't need an alignment to measure circles for concentricity? That seems couterintuitive to me. Aren't circles 2D features that are reliant on the workplane and alignment they are measured from? With no alignment, wouldn't you be dependant on the part being perfectly square with the machine axis? And the circles being exactly perpedicular to the probe?
You don't need an alignment to measure circles for concentricity? That seems couterintuitive to me. Aren't circles 2D features that are reliant on the workplane and alignment they are measured from? With no alignment, wouldn't you be dependant on the part being perfectly square with the machine axis? And the circles being exactly perpedicular to the probe?
no was to the other part, NO it will not be accurate.
2 cylinders, yes, 2 circles, no, for the concentricity.
Remember, concentricity, as reported by PCDMIS, is the same as location, not the ASME Y-14.5 Standard of opposing median points.
It is correct to ISO Standard of concenricity.
I suggest you run a test; measure with and without paint and with and without circles (cylinders). I suspect the difference you see is within the repeatability of the machine.
I suggest you run a test; measure with and without paint and with and without circles (cylinders). I suspect the difference you see is within the repeatability of the machine.
Really?
From the Wilcox Site - Mathematical Definitions of Dimensions
3.0 CONCENTRICITY The first feature must be a sphere (3d concentricity) or a slot, cylinder, cone, or circle (2d concentricity). The second feature is used as a datum feature and must be a cylinder, cone, line, or circle. If there is no datum, the origin and z vector of the current active alignment are used for the datum.
if the first feature is a slot, cylinder, cone, or circle, the perpendicular distance from the centroid of the feature to the datum feature's axis is calculated. The 2d concentricity is twice this value.
If the first feature is a sphere, the 3d concentricity is calculated as twice the 3d distance of the sphere's centroid from the datum centroid (or active alignment origin if there is no datum). End of Defintion.
So then PC-DMIS defines Concentricity not as opposing medians points. So if you need to report Concentricity per ASME Y14.5-1994, DO NOT use the canned dimensional icon. Figure another way to measure and report.
Twice times the 2d or 3d distance creates the feature zone. Sounds like POSITION.
That's why you can use features with an odd number of hits. NOT OPPOSING MEDIAN POINTS.
Twice times the 2d or 3d distance creates the feature zone. Sounds like POSITION. That's why you can use features with an odd number of hits. NOT OPPOSING MEDIAN POINTS.
hope this helps.
Yeah, really (?)
I was referring to the question about paint on the surface and the effect (I hit reply on your comment - dph51). The best way to find out how much influence it has on the result is to run a test.
I agree with the opposing median points by the way. There are many assumptions built into the software; the assumption that the circle is round when calculating concentrically is one of them.
