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Surface Profiles

newsitechris
Hello,

I'm trying to understand something and hoping someone could help.
I have parts that call out just basic surface profiles 1.0/A/B/C or +/-0.5mm.
I normally create individual vector points on the surface, measure the points, and report out the "T" values at +/-0.5mm.
For this new part we have, reporting like this shows very good, consistent parts that exactly match what I'm seeing from checking the parts on the fixture gage.
However, we have a new program manager that says I have to report X,Y,Z & T for every point.
Of course, when I do this, the two-dimensional X,Y,Z's are causing this manager to freak out saying that the die is not producing consistent parts.
I've tried explaining to him that X,Y,Z are two-dimensional and the only surface measurement that matters is the one that is parallel to the surface's normal vector, but he seems to think I don't know what I'm talking about.
Are you guys in agreement with me or do I not know what I'm talking about???
I've been in metrology for more than 20 years so, I hope I know what I'm talking about here.
Please, someone give me your thoughts and maybe suggestions on how to explain this to someone who's not very familiar with metrology.
Parents
  • The T axis will always report the same value, the 3D distance along the perfect vector for a perfect part. Even with machine drift (which all machines have) the "T" axis will still report the 3D deviation from the perfect part to the actual touch along the nominal vector of the touch. Now, if your machine has excessive drift, you can turn SNAP=ON which will 'project' the actual touch back onto the nominal vector. THIS HAS NO EFFECT ON THE T AXIS deviation being reported. For any 3D contour you check as points, the T axis is what is important as it tells the (T)otal deviation along the surface vector. Period. For any 2D that is not square to the axis, again, the T is what tells you what you need to know. For anything that is square to the axis, one of the XYZ values will show the same absolute deviation as the T axis.

    T axis is + when there is 'heavy' stock and - when there isn't enough stock.
Reply
  • The T axis will always report the same value, the 3D distance along the perfect vector for a perfect part. Even with machine drift (which all machines have) the "T" axis will still report the 3D deviation from the perfect part to the actual touch along the nominal vector of the touch. Now, if your machine has excessive drift, you can turn SNAP=ON which will 'project' the actual touch back onto the nominal vector. THIS HAS NO EFFECT ON THE T AXIS deviation being reported. For any 3D contour you check as points, the T axis is what is important as it tells the (T)otal deviation along the surface vector. Period. For any 2D that is not square to the axis, again, the T is what tells you what you need to know. For anything that is square to the axis, one of the XYZ values will show the same absolute deviation as the T axis.

    T axis is + when there is 'heavy' stock and - when there isn't enough stock.
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