Nesting of 2D Parts with Complex Geometry and Material Heterogeneity

This dissertation, "Nesting of 2D Parts With Complex Geometry and Material Heterogeneity" by Tsz-fung, Lam, 林子峰, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis titled Nesting of 2D parts with Complex Geometry and Material Heterogeneity Submitted by LAM Tsz Fung for the degree of Master of Philosophy at The University of Hong Kong in November 2007 In the mass production of sheet metal parts, saving of materials is very important as material costs account for the bulk of the overall production cost. By making use of the Minkowski difference evaluation, efficient nesting of industrial parts is achieved in this study. Actual geometry of the Minkowski difference of complex part shapes is computed by using the proposed algorithms, which includes the edge copying method and advanced decomposition method. In the nesting algorithms, packing of identical part shapes with the same or different orientations is considered. In the part layout formation, strip pitch and width are calculated for identical or different parts and nested pairs of parts in different orientations. The optimum orientation of part shapes that results in the greatest material utilization is then obtained. It was found that both the geometries of Minkowski difference inner loop and outer envelope should be considered for packing the parts as close as possible so as to achieve a very high material utilization rate. These algorithms for nesting and part layout formation are implemented in SolidWorks, and some case studies were carried out on industrial sheet metal parts with curved profiles and concave features to demonstrate the method. These studies are discussed. A number of considerations need to be taken into account in practical product design and the manufacture of sheet metal products to enhance part quality and minimize fabrication cost. Typical considerations include product accuracy, productivity, fabrication cost, reliability and longevity. Efficient nesting of part shapes helps enhance material utilization rate and reduce fabrication cost, whilst the use of functionally graded material coating can improve product wear resistance. However, most existing approaches have considered the nesting and material coating separately, resulting in the alteration of the original product surface geometries. A design and manufacturing scheme for producing high-performance 2D products at low fabrication costs is proposed in this study. By considering concurrently the nesting of part shapes and the material coating, product wear resistance enhancement, guarantee of surface geometry accuracy and fabrication cost reduction are achieved. A case study on design and manufacturing of a typical disc cam with desired surface profile and high wear resistance is provided to illustrate the principle of the proposed scheme. (367 words) DOI: 10.5353/th_b3955700 Subjects: Algorithms Geometry, Differential Inhomogeneous materials