When to use 3D scanning for Inspection, as opposed to traditional measurement tools.

3D Scanning is a relatively new technology in the world of inspection.  And, although it is fantastic for some applications, it is not necessarily suitable for all applications, nor is it a replacement for traditional tools such as calipers and height gages, or the Coordinate Measuring Machine (CMM).

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For the uninitiated, 3D scanning refers to the rapid collection of thousands or millions of data points using a projected light source and a high resolution camera.  There are several types of scanners available on the market today, each with their own specific uses, but they all typically output a “cloud of points”, or polygon mesh (STL file).  These data sets can then be overlaid on the original design CAD model for comparison.  This is a very useful tool for checking complex surface shapes that are not defined by geometric features, such as circles, plane or lines.  The result of this type of comparison is a color map, which will show in-tolerance conditions as green, and out of tolerance conditions as red or blue, depending upon the direction of (inboard or our outboard) of the deviation.

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Color Map of a part

Scanners, however, are not necessarily the best at determining hole locations, particularly on very thin parts such as composites or sheet metal.  In such cases, a CMM (coordinate measuring machine) can be used to probe data points to generate geometric features such as circles for hole locations.  Depending upon the software provided with the CMM, these features can also be compared to the original CAD model to show deviations.  Or, a simple text report showing actual values may be output.

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CMM Machine

Some systems, such as the Creaform MetraScan, combine both scanning and probing into one comprehensive solution for complex surface scanning, as well as geometric feature probing.


Of course, scanning and probing systems can be a somewhat costly investment, and require a certain degree of technical expertise to operate.  If your measurement needs are simple, you may be able to get by with traditional such as calipers and height gages.  These tools are adequate for 1 dimensional measurements, such as the length of a part, the diameter of a  hole, or the over-all height of an object.

In conclusion, the nature of the required measurements is the true driving factor in determining the correct tool to be used.  There may be times when the simplest tool is the most appropriate.

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