Thesis Abstract

<p> </p><div> </div><div><br></div><div> </div><div> </div><div><b>ABSTRACT</b> </div><div> </div><div>In the mass production of sheet metal parts, saving of materials is very important as material cost is </div><div>the major portion of the overall production cost. By making use of the Minkowski sum evaluation, </div><div>efficient nesting of part blanks is achieved. In the part layout formation, strip pitch and width are </div><div>calculated for different blank-pair orientations. The optimum orientation of two nested pairs that </div><div>results in the greatest material utilization is then obtained. These algorithms for nesting and part </div><div>layout formation are implemented in SolidWorks and some case studies carried out on typical parts </div><div>to demonstrate the method are discussed. It was found that for parts that have the Minkowski sum </div><div>inner loop, a very high material utilization can be achieved. </div><div> </div><div>Keywords Minkowski sum, nesting, part layout, material utilization, optimization, SolidW</div> <br><p></p>

Thesis Overview

<p> </p><div>. INTRODUCTION </div><div>Sheet metal parts are widely used in daily life and engineering field. In today's highly competitive industrial environment, it is very important to cut down the production cost. As the material cost is the major portion of the cost involved in mass producing sheet metal components, efficient nesting of parts will minimize the amount of scrap material and reduce the overall production cost significantly.</div><div> </div><div>Traditionally, nesting layouts were carried out manually and it is a very time consuming process. Depending on the designer's skill and experience, the optimal layout is not always obtained. In recent years, computer-aided software tools are used to carry out the nesting of part blanks automatically. Some computer nesting systems are demonstrated by Choi et al. [3], Huang et al. [8] and Zhao and Peng [15]. However, most of the nesting algorithms are limited to</div><div>regular blank shapes such as rectangles or simple polygon shapes. When the blank shapes are irregular, initial conversion to approximate manageable shapes are performed before the nesting process.</div><div> </div><div>In our work, an automatic nesting system for relatively more complex parts is devised and implemented on the computer software tool SolidWorks, and Visual C++ 6.0 is used to create the SolidWorks application programming interface for algorithm demonstration. The nesting process is divided into two main stages: the nesting of two blanks and the part layout formation of two nested pairs. The basic idea of using the Minkowski sum in an algorithm to orient a part on the strip for maximizing the material utilization, which had been presented previously by Nye [12], was adopted and a modified Minkowski sum formation algorithm was developed. In order to deal with the nesting of more complex part shapes, our algorithm would start with the extraction of the blank profiles, which may consist of straight</div><div>or circular edges and even concave features, and then use the Minkowski sum formation to determine the optimum orientation of the nested blank pair and the width of the metal strip.</div><div> </div><div>In the following sections, previous work on the nesting problem and an introduction to the Minkowski sum are presented in Section 2. Section 3 introduces our method of applying the Minkowski sum to nesting of complex sheet metal parts. In Section 4, the nesting algorithm of a pair of convex and concave blanks is presented. Section 5 describes the algorithm of part layout formation together with the calculations of the nesting parameters. In Section 6&nbsp; an example of a pair of convex and concave blanks is used to demonstrate the idea of nesting and part layout of formation. Finally conclusions are drawn in Section 7.</div> <br><p></p>