This project was carried out for Bharat Heavy Electricals Limited, Bhopal.
This is a very good example of Part to CAD inspection using Reverse Engineering. In this project CAD model of pelton bucket was provided and the difference between this CAD model and polyurethane bucket was to be interrogated. Figure 4.4(a) is for the CAD model of the bucket. Given CAD model was used to get a prototype using Stratasys FDM Rapid Prototyping machine. This prototype was used as a pattern to make a Silicon Rubber mould. Twenty-two buckets were made by casting polyurethane into that silicon rubber mould. One of these twenty-two buckets was chosen randomly. Figure 4.4(b) shows the bucket obtained from this mould.
Top portion and bottom portion of this bucket were scanned separately. Spherical probe of diameter 0.25" was used for scanning in both the cases. To register both the point clouds, three common curves were scanned in both the scans. These common curves were scanned using point probe. To register both the point clouds both files were opened in the same viewport and with the help of common curves registration was completed. Figure 4.4(c) and Figure 4.4(d) show the scanned data with the wire frame surface models for top and bottom portions of the bucket respectively.
For inspection, points that were scanned using spherical probe were offseted by a distance of 0.125", which is equal to the radius of spherical probe. Now top portion of the CAD model of bucket and scanned data of bucket top were registered using three common curves. Difference in between the scanned point data and CAD model was interrogated. The result of this interrogation was a colored plot representing the magnitude of difference by different colors, which is shown in Figure 4.4(e). The same procedure was repeated for bottom portion of the bucket. The colored plot of the difference is shown in Figure 4.4(f). It is observed that this difference is in between +0.57mm and -0.77mm.
