| dc.description.abstract | A framework and methods are presented in this thesis to support integration of 3D feedback control systems to improve dimensional conformance during fabrication of engineered assemblies such as process piping, structural steel, vessels, tanks, and associated instrumentation for industrial construction projects. Fabrication includes processes such as cutting, bending, fitting, welding, and connecting. Companies specializing in these processes are known as fabricators, fabrication shops or fab shops. Typically, fab shops do not use 3D feedback control systems in their measurement and quality control processes. Instead, most measurements are done using manual tools such as tape measures, callipers, bubble levels, straight edges, squares, and templates. Inefficiency and errors ensue, costing the industry tens of billions of dollars per year globally. Improvement is impeded by a complex fabrication industry system dependent on deeply embedded existing processes, inflexible supply chains, and siloed information environments. The goal of this thesis is to address these impediments by developing and validating a new implementation framework including several specific methods.
To accomplish this goal, several research objectives must be met:
1. Determine if 3D dimensional control methods are possible for fab shops that do not have access to 3D models corresponding to shop drawings, thus serving as a step toward deploying more integrated, sophisticated and higher performing control systems.
2. Discover ways to solve incompatibility between requested information from fabrication workers and the output information delivered by state-of-the-art 3D inspection systems.
3. Conduct a credible cost-benefit analysis to understand the benefits required to justify the implementation costs, such as training, process change management, and capital expenditures for 3D data acquisition units for fab shops.
4. Investigate ways to compare quality and accuracy of dimensional control data sourced from modern point cloud processing methods, conventional surveying methods, and hand tools.
Methodologies used in this research include: (1) an initial literature review to understand the knowledge gaps coupled with informal interviews of practitioners from industrial research partners, which was revisited throughout the development of the dissertation, (2) development of a conceptual framework for 3D fabrication control based on 3D imaging, (3) development and validation of algorithms to address key impediments to implementation of the framework, (4) experiments in the fab shop environment to validate elements of the framework, and (5) analysis to develop conclusions, identify weaknesses in the research, understand its contributions, and make recommendations.
By developing and testing the preceding framework, it was discovered that three stages of evolution are necessary for implementation. These stages are:
1. Utilization of 3D digital templates to enable simple scan-vs-3D-model workflows for shops without access to 3D design models.
2. Development of a new language and framework for dimensional control through current ways of thinking and communication of quality control information.
3. Redefining quality control processes based on state-of-the-art tools and technologies, including automated dimensional control systems.
With respect to the first stage, and to address the lack of access to 3D models, a framework for developing 3D digital template models was developed for inspecting received parts. The framework was used for developing a library of 600 3D models of piping parts. The library was leveraged to deploy a 3D quality control system that was then tested in an industrial-scale case study. The results of the case study were used to develop a discrete event simulation model. The simulation results from the model and subsequent cost-benefit analysis show that investment in integrating the scan-vs-3D-model quality control systems can have significant cost savings and provide a payback period of less than two years.
With respect to the second stage and to bridge the gap between what 3D inspection systems can offer and what is expected by the fabrication workers, the concept of Termination Points was further defined and a framework for measuring and classifying them was developed. The framework was used to developed applications and tools based on the provided set of definitions. Those applications and tools were further analyzed, and the results are reported in each chapter. It is concluded that the methods developed based on the framework can have sufficient accuracy and can add significant value for fabrication quality control. | en |
