This article is a summary of the article “White Light Scanning in Action” published by CMM Quarterly.
A company that produces stampings for automotive and other industries in Canada approached RX Metrology to request to reverse engineer 24 die blocks for legacy automotive body stampings.
This company had previously contracted CMM programming and training services to RX Metrology, but this time, capturing full surfaces was needed and clearly a CMM was not enough.
RX Metrology contacted his partner FixLogix, US distributor for SIDIO white light 3D scanners for assistance in this task.
They used the Nub3D SIDIO XR to scan the die blocks, and Polyworks software to reverse engineer the surfaces from the point cloud data. Some of the scanning work could be performed in the inspection lab where their CMM resides, but a significant portion of the work needed to be done on the shop floor due to the size and weight of the die sections.
The working surfaces of the die blocks were highly polished. The Nub3D scanner is capable of scanning relatively shiny and dark surfaces, but in this case the high polish of the part surfaces led them to decide to spray the parts. This allowed them to work much faster with fewer shots to capture all the sculpted surfaces, as the matte finish of the powdered surface gave much better light return to the scanner camera. They also prepared the parts with circular targets, many of which were mounted on magnets, allowing for quick placement, removal and re-use.
The purpose of the circular targets is to allow the scanner or the part to be moved during the scanning process, while maintaining registration (alignment) from one scan to another. The targets are placed in a random pattern; as long as the scanner can see (around 4-5) targets common to both scans it can align the two images together. Below is a screen shot of the point cloud data developed from several scans.
The scanner software is very intuitive. Both the scanned data and the “live” measuring window are displayed on the monitor. The newest scan shows up as orange and in the same orientation as the operator is scanning, what makes the scanning process much easier and intuitive.
In the measuring window if the object is green the light level is good, while red indicates that the object is over-saturated with light. The Nub3D system allows for multiple exposures to be used in one scan, which is very helpful for finding both the targets and darker part surfaces in one shot. A focus pattern (the two shadow stripes) allows the operator to confirm that the object is the correct standoff distance from the scanner.
Below is an image of the final desired result: a CAD model derived from the points scanned by the Nub3D white light scanner.
Tags: die blocks , Reverse Engineering , sheet metal
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