Nesting strategy for standard parts under variable demand

Optimization of the cutting of sheet metal parts involves the arrangement of parts to be cut on sheets for a minimal trim loss. In addition, the number of parts of different types in any nesting layout must be selected so that an appropriate combination of such nesting layouts results in the required quantity of any part type and in a minimal amount of extra parts cut. The creation of high-quality nesting layouts of arbitrarily shaped parts is difficult, and therefore the number of nesting layouts created should be kept low and the nesting layouts should perform adequately under uncertain demand conditions. In this paper, a nesting strategy and methods for its practical implementation are presented for selecting the candidate parts to be included in each nesting layout and for choosing a combination of layouts to be cut. As another aspect, such a grouping of the parts in subsets of layouts is studied, in which the parts of each type are present in one subset only. By means of such a nesting strategy, the problem can be divided into smaller subproblems, which are solved more easily. Examples of results of numerical experiments made are given.