Finding the Correct height of a 3D surface feature
Using a 3D gauge to inspect defects like pits is different from a shadow graph or stylus check, because it automatically includes the highest/lowest point on the feature you’re measuring, so you don’t have to try different angles and alignments to find it — it’s in there, but where? The software automatically reports a profile height as you draw a trace across the data. But the result varies depending on your starting point, and which part of the surface you’re crossing. The trick is finding a way to keep the shape of the surrounding area from throwing off the reported height difference.
In most cases, you’ll want to treat some area (like the area around the bump) as “normal”, with zero height. But in a three dimensional measurement with high precision–or on a surface with shape like a cylinder or sphere–the surface you want to be “zero” isn’t really flat and equal.
In this video, Applications Engineer Jared Wheeler shows how a 4D InSpec’s reference mask feature can be used to set the surrounding surface area to zero, so you get a true measurement of the defect. 4D InSpec is a handheld surface measurement gauge used for providing super-fast, shop-floor inspections of parts surface features like pits, scratches, corrosion nicks and edge break.
In drawing a trace profile across a data set, you can make the trace several (or many) pixels wide — the result is an average trace for all the included rows of pixels. This averages out individual peaks and valleys, so that you are seeing the more general shape from the beginning to end of the profile, without the noise.
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