Designing Algorithm for Nesting Irregular Shapes With and Without Boundary Constraints

Abstract

Nesting of flat patterns into a given raw sheet has applications in a number of industries. It is in fact a common problem often faced by designers in the shipbuilding and garment manufacturing industries. In addition to a number of constraints peculiar to the specific type of application, the basic goal is to achieve a good layout so that material wastage will be reduced to a minimum. Traditionally, a solution is achieved through the careful manipulation of an experienced designer. This is equivalent to putting together an imperfect jig-saw puzzle which is highly Intuitive and time-consuming. This paper describes the design and development of a nesting algorithm in a step-by-step approach from scratch. Graphics routines are used to describe the shape of a pattern. An approximate-shape routine than replaces the original pattern with a multi-sided polygon. The patterns can be completely different in shape or repetitive in small batches. For repetitive patterns, a pairwise layout is first used to search for a probable good nesting module. Modules are further clustered to form larger modules using a rectangular-packing routine. The program gives an automatic layout solution with variables such as bridge width and stock size controllable by the operator. The program also caters for raw sheet with irregular boundaries and internal bad patches. This feature has further application in leather trimming since leather sheets are highly irregular in profile and are known to contain a large amount of defects such as scars and scratches.