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Help: Measuring Scribe Line Profile on a 3 dimensional surface.

SAguy
Hi everyone,

I'm new to the forums and DMIS in general. So far I seem to have everything down good except for this one nagging issue: How to measure a scribe line on a contoured surface. I've asked experienced DMIS users and people at Hexagon and no one has been able to give me an answer. So i'm reaching out to you guys.

I understand that if a part is 2 dimensional all you have to do is create a profile of a line dimension and just look at the workplane it is on. But how do you do it with a 3 dimensional part, for example:



When I do a line profile on that scan i get numbers all over the place (+.8,-.8). You can see in the screen shot that the points are right on the line. The line in the CAD is not an actual groove, but a line on that surface.

I also need to be able to eliminate any error in the depth and just look at the straightness of the line. I know in other softwares that I've used you would just project the points to the CAD surface and it would analyze to the line.

I really need to get this figured out, parts like this are the bread and butter of the place I work. We haven't had inspection capabilities until we got a Romer Arm. Now that we have one, customers want to send over the tight tolerance molds but we're on hold because we can verify the scribe lines properly. Any help or guidance would be greatly appreciated, thanks.
  • What exactly do you mean by "scribe line"?
    Do you mean a line that is physically scribed into the part?
    Are you trying to line up the tip with it? That would be pretty hard to do accurately.

    Do you mean an intersection of some surfaces?????
    Do you mean some sort of theoretical gage line on the parts?

    By tight tolerances, what do you mean?
    IMO, a Romer will not hold what I consider to be tight tolerances.
  • A scribe line is a line that is physically scribed into the part, about .010 deep x .010 wide. These are aluminum molds for carbon fiber pieces. It represents the end of the part, after the part is layed up the line shows up on the carbon and that's were it will be trimmed. When I say tight tolerances, I mean tight tolerances for layup work. Usually along the lines of: .010 Profile of a line. I take the points on the line by using the sharp tip probe and placing it in the center of the line. The scribe is cut with a v-shaped cutter. Typically i'm given CAD that included just a line on the surface, sometimes i get it as a groove in the surface.
  • Use the point tip probe, measure the points (vector, surface) with autotrigger, trigger radius of .004"
  • Do i need to have the line isolated on a different layer and turn off the surfaces?
  • Do i need to have the line isolated on a different layer and turn off the surfaces?

    It´s easier to pick the points on a surface, use your line as a guide or reference, zoom the CAD in at the max for best results.

    One more thing you can try is to turn on the "find nominals from CAD" mode, take points directly on the line, then you have to be creative and find a way to compare against the nominal (it´s easy if the line is square to grid)Slight smile
  • Well i gave it a shot and this is where i got.


    It's analyzing the depth of the scribe instead of its' straightness. I think i need to find a way to project the points to the surface in the CAD (along the vector) so it doesnt show depth. This was how I had to do it in another software.
  • I was fearing that was the case. I would have thought the guys at wilcox would've came up with something by now. I guess there's not too many people who need to do this.
  • Just sent an email to Hexagon, I'm sure the response will be something along the lines of "We're working on it for 2011".
  • If you know the depth of the scribe, use that value for your theoretical thickness, then just dimension individual points in the axis you need (X axis by looking at the image you posted)
  • Well i gave it a shot and this is where i got.


    It's analyzing the depth of the scribe instead of its' straightness. I think i need to find a way to project the points to the surface in the CAD (along the vector) so it doesnt show depth. This was how I had to do it in another software.

    A few ideas to offer -
    Project the points to a generic plane and profile?
    Pull single-axis data via an array and reporting the range (min-to-max)?
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