T-Value for Edge Points & Surface Points

[rangerboat72]

Is there a way to get the T-value for Edge Points & Surface Points? I like using these features for several reasons but seem unable to use them for profile because the gap only and T-values do not seem to work with these features. I really like using them because of the relative measurement association. I do not have to translate to other features prior to measuring the particular feature I'm required to measure. Usually, I use them but I do not report the T-value or turn the gap only on since it has no apparent effect.

[Matthew D. Hoedeman]

Well, the T value works just FINE for edge points. I can't tell you about surface points as I do not use them, I use vector points, but it SHOULD report the same for surface as it does for vector points, the only difference between them is that SURFACE points allow you to use sample hits so that it will then drive the actual vector of the point instead of the nominal (cad) vector of the point. Unless you are dealing with tolerances that are EXTREMELY small, the vector point sould be good enough, you have to have quite a bit of 'off-angle-ness' in the surface before a significant deviation shows up from using cad vectors instead of nominal vectors and who has the time to take 4 hits for every point on a part instead of 1?.

As to the GAP ONLY mode, that will only show an effect IF you are using a surface sample hit, what it will then do is 'project' the actual point back down into the nominal surface, thus eliminating the surface error from the XYZ locations, it SHOULD NOT have any effect on the T value for the edge point since that will be the (T)otal deviation, along the edge vector, for the edge point and nothing to do with the surface deviation. Using a surface sample hit will also allow you to use the S axis for the edge point, giving you the surface deviation of the point.

Gap only only works for edge points (as far as I know).

More info:

http://www.pcdmisforum.com/showthread.php?t=2575

[rangerboat72]

Wow that was quick...

Matt,

I'll have to experiment a little more with them. The main reason I use surface points rather than vector points is the fact that the parts I am measuring are typically out of square in which the feature that I am measuring is nowhere near where it is supposed to be. All that matters is the location of one axis (lets say the Z-axis). So rather than translating to a point on the side, I use the realative measurement in the surface point to relate it to a point on the side. I'll read through the thread you linked me to and see if it helps me understand any more... Thanks for the assistance.

[Peter Warcholyk]

Rangerboat,

As you stated in your note, the main reason that I typically use surface points instead of vector points, is the fact that then you can use them to do "relative" measurements.

ZydecoPete

[Paul Barriage]

I just wrote a small program to make sure, but T value does come up on my auto dimension for a surface point.

[rangerboat72]

I just wrote a small program to make sure, but T value does come up on my auto dimension for a surface point.

Is the T value calculated correctly though? I cannot get them to calculate correctly when I use them. I tried "SNAPPING" the surface points, but it still did not calculate like a vector point with snap on???