Hello all,

The runout represents for tridimensional metrology a real challenge. The reason is due to the fact that involves object revolution and in 3D measurement there is no such rotational movement.

I confess that I am not very fluent with this evaluation because it was never an item that I had to use a lot throughout my life.

It is usually said that runout and total runout are obtained by applying the following formulas:

3.jpg

This represents the worst possible case since it can only happen if we join the largest deviation of circularity and concentricity in the same section as illustrated below:

4.jpg

Taking the practical example of a PC-DMIS report we have:

5.jpg

In this case, the value "RN" refers to the circularity deviation and below is the concentricity deviation resulting from the combination of the XY deviations.

Applying the formula described above we have:

0.042 + 0.064 = 0.106

Like this we assume that the illustrated scenario will for sure occur.

It is for sure a safeguard and we can say that with this evaluation in the extreme, we only reject good parts and never the opposite”.

It is true that:

7.jpg

Where C and T depend on how shape (circularity) and position (concentricity) relates to each other.

However the modern CMM applications come equipped with modules of direct Runout and Total Runout evaluation. In theory the software can estimate the values of C and T simulating manual measurement.

In our case, if we do so, this will get the following result:

8.jpg

This is what makes Runout so difficult to evaluate using a CMM, and it is for me always preferable to evaluate the two components individually.

My question to you is if you already correlate the results from the direct evaluation to a manual measuring on a dedicated test machine and how accurate the CMM result can be.

Please give me your thoughts regarding this issue.

Thank you.

The runout represents for tridimensional metrology a real challenge. The reason is due to the fact that involves object revolution and in 3D measurement there is no such rotational movement.

I confess that I am not very fluent with this evaluation because it was never an item that I had to use a lot throughout my life.

It is usually said that runout and total runout are obtained by applying the following formulas:

3.jpg

This represents the worst possible case since it can only happen if we join the largest deviation of circularity and concentricity in the same section as illustrated below:

4.jpg

Taking the practical example of a PC-DMIS report we have:

5.jpg

In this case, the value "RN" refers to the circularity deviation and below is the concentricity deviation resulting from the combination of the XY deviations.

Applying the formula described above we have:

0.042 + 0.064 = 0.106

Like this we assume that the illustrated scenario will for sure occur.

It is for sure a safeguard and we can say that with this evaluation in the extreme, we only reject good parts and never the opposite”.

It is true that:

7.jpg

Where C and T depend on how shape (circularity) and position (concentricity) relates to each other.

However the modern CMM applications come equipped with modules of direct Runout and Total Runout evaluation. In theory the software can estimate the values of C and T simulating manual measurement.

In our case, if we do so, this will get the following result:

8.jpg

This is what makes Runout so difficult to evaluate using a CMM, and it is for me always preferable to evaluate the two components individually.

My question to you is if you already correlate the results from the direct evaluation to a manual measuring on a dedicated test machine and how accurate the CMM result can be.

Please give me your thoughts regarding this issue.

Thank you.

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