CAD Auto-Align™ - Automatic CAD Overlay Alignment VisionGauge® Digital Optical Comparators

VisionGauge®’s patented CAD Auto-Align™ tool reduces inspection times and obtains increased accuracy.

Automatic CAD Overlay Alignment with New Enhanced CAD Auto-Align™

(Patented & Other Patents Pending)

VisionGauge®’s groundbreaking CAD Auto-Align™ tool automatically aligns a CAD overlay to a part. This gives VisionGauge® its unique ability to carry out fully-automated CAD-to-part comparison.

The VisionGauge® Digital Optical Comparator's CAD Auto-Align™ tool automatically aligns the CAD data to the part.

VisionGauge®’s patented CAD Auto-Align™ tool allows you to drastically reduce inspection times and obtain increased accuracy. This powerful tool is very fast (it typically takes just a few seconds) and it produces repeatable and accurate results that are completely operator-independent!

It’s a very general-purpose tool and the CAD-to-part alignment can be carried out along either a single or multiple datums or as an overall best-fit. The tool can carry out both translation and / or rotation alignment. You can easily apply it to meet the requirements of your specific application!

VisionGauge®’s CAD Auto-Align™ tool can be used to solve many different applications across a very wide range of industries including medical, aviation & aerospace, power & energy, military & defense, tooling, packaging, electronics & semiconductors and many, many more. This tool is the ideal solution whenever you need to compare a part to its CAD data.

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.

5x hip implant inspection

Image 2: 5X magnification - hip stem
Previously, the CAD Auto-Align™ tool operated on a single field-of-view. This means that for larger parts, a lower magnification needed to be used. This necessarily produced lower resolution and accuracy

Multi-FOV CAD Auto-Align
10x hip implant inspection
10x hip implant inspection (section 2)
10x hip implant inspection (section 3)

Image 3: 10X magnification - hip stem
Because the new enhanced CAD Auto-Align™ tool can now use multiple images to cover all of the part’s features of interest, it imposes absolutely no limitation on magnification and produces results of maximum resolution and accuracy.

For example: Images 2 and 3 above show the same hip stem. In Image 2, a lower (i.e. 5X) magnification is used so that the entire part fits within the field-of-view. In Image 3, a higher (i.e. 10X) magnification is used and the entire part is covered using 3 images. VisionGauge®’s new enhanced CAD Auto-Align™ tool carries out the CAD-to-part alignment across all 3 of these images and – because the system resolution is higher at 10X than at 5X – it produces a higher resolution and higher accuracy results.

Turbine blade inspection at 10x magnification

Image 4: Turbine blade fir tree at a lower (10X) magnification to fit the entire part inside a single field-of-view.

20x magnification Turbine Blade inspection
20x magnification Turbine Blade inspection (section 2)

Image 5: The same turbine blade fir tree as above, but this time covered using 2 images taken at a higher (20X) magnification. VisionGauge®’s new enhanced CAD Auto-Align™ tool carries out the CAD-to-part alignment using both images. This approach produces an overall result of higher accuracy.

And in the same way that VisionGauge®’s enhanced CAD Auto-Align™ tool is able to deal with parts that are larger than the system’s (XY) field-of-view, it can also overcome depth-of-field limitations. Specifically: in applications where the variations of the part’s height or depth (i.e. along the Z axis) are greater that the system’s optical depth-of-field, images taken at different Z positions can be included in the image set. VisionGauge®’s new calculation algorithm is then able to carry out a CAD Auto-Align™ over the image entire set, taken at different Z (and also possibly X and/ or Y) positions and best-fit the CAD to the part in these situations as well.

All of these new enhancements are the subject of new patent applications.

And, as previously, the results of VisionGauge®’s CAD Auto-Align™ operation can then be analyzed by VisionGauge®’s patented CAD Auto-Pass/Fail™ tool, all of which provide VisionGauge® with its unique and powerful ability for fully-automated high-accuracy part-to-CAD comparison.

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”.

out of tolerance edge - sketch1

Sketch 1: An area of the part that is out of tolerance

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.

out of tolerance area - sketch2

Sketch 2: The CAD Fitting™ tool would only affect the out-of-tolerance areas (highlighted in red)

Finally, Images 1 and 2 show how – in certain circumstances - the CAD Fitting™ tool manages to turn into a “Pass” the results of the CAD Auto-Align™ tool that produced a “Fail” result. Image 1 is concerned with an aerospace part and Image 2 with a medical part.

aerospace part CAD Auto-Align results vs CAD Fitting
Aerospace part CAD Fitting results

Image 1: the CAD Fitting™ tool applied on an aerospace part. The results of the CAD Auto-Align™ tool are shown on the left and those of the CAD Fitting™ tool are on the right.

medical part CAD Auto-Align result
Medical part CAD Fitting results

Image 2: the CAD Fitting™ tool applied on an medical part. The results of the CAD Auto-Align™ tool are shown on the left and those of the CAD Fitting™ tool are on the right.

Many VisionGauge® Digital Optical Comparator users combine the CAD Auto-Align™ and CAD Auto Pass/Fail™ tools to fully automate their inspections:

  • The operator loads the part in the fixture and scans the barcode on the traveller.
  • This causes the VisionGauge® Digital Optical Comparator to load and run a part-specific program that automatically:
  • Reads-in the correct CAD file
  • Auto-Aligns the CAD file to the part (even in the case of very large parts)
  • Produces an Auto Pass/Fail result that is collected in a Data Group and sent to Excel or another external application...
  • In the case of parts that are larger than the system's optical field-of-view, the stage moves the part and carries out the Auto Pass/Fail inspection at however many different locations are required. This way, the whole part gets inspected without having to "shift the overlay". The CAD data tracks the part's movement!

With VisionGauge®’s patented CAD Auto-Align™, CAD Auto Pass/Fail™, and patent-pending Tooth Checker™ tools, the VisionGauge® Digital Optical Comparator is truly revolutionizing how parts are inspected, quickly and accurately, directly on the shop floor!

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