VisionGauge®’s CAD Auto-Align™ tool has now been enhanced to make it even more widely applicable. The tool can now be applied to very large parts that extend way beyond the system’s optical field-of-view. And in the same way, it can now be used on parts that have very large variations in depth and height, much larger than the system’s optical depth-of-field.

When dealing with large parts, the system scans the part (a single time) and captures and stores images of all of the areas of interest as well as the precise location at which each image is taken (using the system’s high-accuracy encoder readings). VisionGauge®’s proprietary algorithm then iteratively aligns the CAD to the part, across all of the images and along all of the prescribed datums. As these calculations quickly converge to the correct solution, the system does not need to revisit any of the image capture locations, thus tremendously speeding up the overall operation. All of the calculations throughout the entire process are carried out on the initial image buffers. This results in tremendous time savings and very fast overall performance, even when dealing with very large parts.

Furthermore, because there is no limit on the number of images used to encompass all of the part’s datums and features of interest, it is possible to carry out this CAD Auto-Align™ operation at high magnification, which produces very high accuracy results, even in the case of large parts.

VisionGauge®’s new “CAD Fitting™” tool

VisionGauge®’s patented CAD Auto-Align™ tool aligns the CAD nominal to the part at user-specified control sections. It does this in a least-squares sense, i.e. it minimizes the sum of the squared deviations from nominal over all of the control sections.

In most cases, this is ideal. However, there are some situations where it might not be the absolute optimal approach. For example: we can imagine an (extreme) situation where the result of the CAD Auto-Align™ calculation would have the CAD nominal perfectly aligned with the part at all of the control sections except one, at which the part would be just outside the tolerance band. This could lead to a “Fail” result. In this example, the optimal solution might be to slightly modify the alignment (still respecting all of the prescribed constraints) so as to “bring the part back into the tolerance band” at the one control section where this was not the case. This could result in the part slightly “moving away from the CAD nominal” at the other control sections, but still remaining in tolerance at all of these locations. This is what we refer to as “CAD Fitting™” and, in this case, it would transform the result to a “Pass”.

Sketch 1 shows an area of a part that is out of tolerance. The CAD Auto-Align™ tool would attempt to carry out the correction “A” to align the CAD nominal and the part. The CAD Fitting™ tool, on the other hand, would only attempt to bring the part back in the tolerance band, i.e. applying the smaller correction “B”.

Sketch 2 illustrates how the CAD Fitting™ tool is only applied on the control sections in the out-of-tolerance areas, whereas the full CAD Auto-Align™ tool is applied on all control sections everywhere.