Issues with using 3d Lines for distances

[[Za...]]

Hello all,

I'm running into an issue using 3d lines for distances, and I was wondering if there's anything I can do to improve my results.

For example, on this picture, the distances from hole to hole measure almost nominal, but when using a 3d line to 3d line comparison, the feature fails. Now I know the line is going to be skewed a little bit due to the scanning of the threads, but for the result to be as far out of tolerance as it is, I'm confused.

I have all of my nominal depths set the same for each thread and I set the nominal A1/A2 to zero to straighten out the line as best as possible. Am I missing something?

Thanks in advance,

Zach

[[Mi...]]

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To make sure I understand: you have two 3d lines parallel to the x-axis, and you're trying to find the y-distance between them? What distance tool are you using, Cartesian?

If that's the case, I've had trouble with it before. Since the 3dlines are never exactly parallel, it doesn't know exactly where along the lines to measure the distance. You might be able to fix it by using caliper distance - I'm not sure, since I'm several versions behind where I work and I haven't used it myself.

Otherwise, though, you an recall one of the lines into a point, which will be drawn at the midpoint of the line, then report the perpendicular distance from there to the other line.

[[Za...]]

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The first part of your response is correct, I'm actually just reporting the actual Y location of the 3d line based on a secondary alignment, but the results are different in the Caliper distance window as well.

I'm going to try to recall the 3d lines to points and I'll be back with my results.

[[Er...]]

Unless your drawing specifically ask you to do this, report the Y location of every hole separate.
Your line will have an infinite options of Y distance values.

[[Za...]]

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Since I've always had bad luck with the 3d line method, I've been reporting each hole location, but it would be nice to be able to report this as one check. I suppose if it's not going to yield accurate results, I'll have to keep doing it the old way.

Here's the drawing if it helps

[[Jo...]]

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I would not trust a 3d line as "one measurement". One hole could be at 1.662 and the other at 1.462 and be "perfect" at 1.562 on center..

[[No...]]

Four different distances if you only consider the end points of the lines, five if you include the center.
Infinite number if you go along the whole line.
Which one do you want?

(Warning: dramatized image following)

[[Ja...]]

When you created your 3D lines did you use "recall" or "recall feature points"? Recall will use the center point of the circle. Recall feature points could be off to one side of the circle if you have more points on that side from scanning more than 360 degrees of the circle.

[[Ri...]]

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Unfortunately the oil/gas people love dimensioning things this way.

[[Jo...]]

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Richard,
If you were to check the position X, Y in the feature, would it be to the centroid of cylinder?

[[Ri...]]

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Unfortunately no. The XYZ of the feature (of any 3d feature) is from the feature coordinate system which for a cylinder is either the top middle or bottom middle of the feature.

[[SH...]]

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I think there is an option inside the evaluation dialogue box to change it to centroid, I don't wheather it is possible globally.