Shape and dimensional analysis of castings with tactile coordinate measuring systems has its limitations. Therefore, US steel foundry Bradken has implemented optical 3D metrology. This enables inspection processes to be accelerated.
The Bradken foundry in Tacoma, Washington (USA) has a long tradition, tracing its roots back to 1899. Today, the plant produces castings mainly for the energy sector such as turbine components, pumps, valves, compressors, and hydropower generators with a net weight of up to 25 metric tons.
Since the production of growing volumes of high-quality castings, complete and consistent quality control became increasingly important. This made faster and full-field measuring and inspection methods necessary. Those methods not only had to cope with the requirements, but also needed to handle complex geometries and dimensions of up to 4.5 meters. When performed with the conventional coordinate measuring machines on articulated arms, shape and dimensional control of these components took several weeks. As a result, tactile measurement had its limitations in terms of the throughput of parts that could be measured internally by Bradken.
In an extensive selection process, various metrology systems such as 3D laser scanners, laser trackers and optical 3D fringe projection scanners were tested on large, machined domed castings intended for use on a production line for transport containers. Tests conducted in Tacoma demonstrated that, within eight hours, only the optical 3D fringe projection scanner ATOS was able to deliver precise scans with the specified tolerances along with an extensive analysis of the complete domed casting.
Unlike conventional tactile coordinate measuring systems
(which scan only individual points) or laser scanners
(which analyze measurement data for specific sections), optical 3D metrology systems such as ATOS capture the entire surface of the Bradken castings. Using the information
thus gathered, the ATOS software automatically determines the 3D coordinates in the form of a high-resolution
point cloud (ASCI/STL). The generated polygon mesh describes free form surfaces and primitives which can,
during shape and dimensional analysis, then be compared with the drawing or directly with the CAD data. Bradken’s engineers are thus able to instantly identify dimensional deviations in the on-screen color plot, thus providing substantial time savings for the Tacoma-based foundry.
Having incorporated the ATOS measuring systems into its inspection processes, Bradken is now able to measure large and complex components as well as mounted assemblies – capturing the complete object, meeting tight tolerances and working within appropriate time limits. As a result, the foundry’s investment has paid off faster than originally expected. Inspections no longer need to be outsourced, delivering additional cost savings.
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