Tolerance design and processes for fabricated jet engine components

Understanding the causes and effects of dimensional and geometric variation is a major concern in the design and manufacturing of products. Geometry assurance is a generic name for different activities with the aim to secure the quality of the company’s geometry definition and verification process, which includes both virtual and physical processes. Methodology and support for a robust design, simulation and visualization of variation is important to be able to make the product as insensitive to manufacturing variation as possible. It is important to have an internal overall picture of the geometry process to become more effective and achieve higher quality on the products and an efficient manufacturing process. To be more competitive in the market Volvo Aero has launched the concept of Make it light. This design objective is partly met by fabrication, i.e. designing products with an increased number of subparts. Fabrication leads to new/increased demands on the ability to break down geometrical requirements to subparts and to be able to sum up the expected variation from subparts to a top level to assess producibility/quality. It is important to be able to take control of geometrical variation in an early stage of product development, and this requires new tools and working methods. Volvo Aero is currently developing several products that will enter into service in the near future, and several other product development projects are in the planning. When this happens, and production volume increase, the number of deviations might increase many times compared to the present levels according to internal estimations. This will result in increased cost of poor quality (non-conformance handling, tied up material and scrap). This thesis work has through analysis, of Volvos GDP (Global Development Process) and Geometry Assurance processes in the automotive industry, worked towards a description on how this method can be used at Volvo Aero. An interview study was made to be able to form a description of how the Geometry Assurance process could be visualized today. Suggestions of improvements of today’s Geometry Assurance process was discussed and visualized through a future Geometry Assurance process, which shows the possibilities for what Volvo Aero could achieve. Through the studies and the interviews it became quite clear that improvements regarding handling and visualizing variation is something that is needed at Volvo Aero. A case was used to show the possibilities of improvements with a method to analyze and visualize stability, contribution of locating points, variation envelope and stack-ups, this all in 3D environment, which could be implemented early into the design process. The recommendations are that Volvo Aero should implement the suggested Geometry Assurance process, because it is a good way of visualizing the working process and highlights problem/improvement areas for further discussions. The process is in line with Volvo Aero’s current strategy regarding producibility and fabrication. A 3D visualization stability and variation simulation tool should be acquired since it shows a lot of potential of minimizing deviations and creating a better connection between tolerance chains and the 3D model. The tool is also most likely to improve the efficiency of the Product Development process, because of the few hours it takes to perform the analysis. If the Geometry assurance process and a 3D visualization tool are implemented at Volvo Aero, future work is needed regarding easy access and search ability of capability data and Geometry Assurance process support for the projects etc.Validerat; 20101217 (root