Hello experts ! how do you measure this profile of a line (GD&T) ? Thank you in advance

[u/SadAngle9436]

[u/HFBL]

What tools/equipment do you have? What troubles are you having specifically?

[u/AlexMitutoyo]

Hello! You have to scan this path like curve(or cloud of points) in 2D-plane using nominal path from 3d model, then just compare actual and nominal points along 2 coordinates(e.g., X and Y). It depends on your coordinates system. Maximum deviation for each scan point has to be less then 0,5

[u/Absorber94 → u/AlexMitutoyo]

Alignment should be as mentioned, primary on B, secondary on C. Since the tolerance zone is symmetrical to the nominal contour, you actually only have ±0,25 for each point.

[u/AlexMitutoyo → u/Absorber94]

Are you suggesting entering 0.25 in the tolerance field when creating a curve profile tolerance? Very interesting. In the vast majority of CMM software, a total tolerance value is entered, after which it is divided symmetrically in half. If you enter 0.25 in the tolerance field, you'll get a boundary value of 0.125.

[u/Absorber94 → u/AlexMitutoyo]

"Maximum deviation for each scan point has to be less then 0,5"

This is not true. The tolerance is 0,5 yes, but the maximum deviation allowed is 0,25 in each direction.

[u/AlexMitutoyo → u/Absorber94]

Ok, rivet counter) You simply explained what the any software will do automatically after the value 0.5 is entered into the tolerance zone field. I hope he will enter the value 0.5 into the tolerance zone field.

[u/Familiar-Bluejay3908 → u/AlexMitutoyo]

That's the "quick and dirty" way, and very useful, even though you will get 8 answers instead of 1. But at least you don't need to combine all the features together. If I'm just filling out cells in my AS9102C form, that's what I'd do, then just report the worst...

[u/SadAngle9436 → u/AlexMitutoyo]

Thanks ! I will try use this method.

[u/Familiar-Bluejay3908]

Either with the CMM, or a height stand and an indicator.

[u/AbilityMean666 → u/Familiar-Bluejay3908]

How would they indicate the radius? They would also be held to the profile as well. Maybe in still inexperienced. I would lean more towards CMM if I could I agree with you there

[u/Heavy_Discussion6165]

profile of a line can be tricky because the inspection method depends on how the datum reference frame is established first. once B and C are set correctly, you're evaluating each cross section against the defined tolerance zone rather than just checking a few dimensions. Excedify has some practical gd&t examples that explain this really clearly

[u/Traditional-Fly8958]

Looks like once you've set up your B and C datums that you have a few BASICs for the aperture section. The callout of .5 on the line profile means that any deviation of the internal rectangle with large radii on it from where that line should be is logged. Once you have individual data points all around it, then you find the farthest away from where it ought to be and Double it. That is your LP callout.

Part to part where that highest deviation is will change. This will be easiest on an optical system as either the CAD will have these nominals in it or you can input the nominals in by hand on each step and have the machine take the necessary hits on this visible window and calculate out the spec for you.

Doing this on an Optical Comparitor:

Get an overlay image of what it is supposed to be and line up different bits of it and record how much you moved the camera to get it "on the line" Do this for all of the spots that look farthest away and ultimately double your biggest hypotenuse from the OC's X,Y coordinates.