Measures of backtracking and bi-directional flow in one dimensional machine location problems

Abstract

In many modern manufacturing settings, management simplifies the workflow of jobs to the greatest extent possible by avoiding a job-shop structure in favour of a generalized flow line (GFL) in which all jobs flow in a single direction (Conway et al., 1967, Theory of Scheduling (Addison-Wcsley)). Heuristics may be used to assign machines to appropriate locations in the attempt to achieve a GFL. Materials that must be transported upstream in a production line are said to ‘backtrack’. Since no backtracking occurs in a GFL, the relative amount of backtracking that does occur is an indication of the degree to which the ideal (and most productive) case is achieved. Several measures of the backtracking of materials are developed in this paper to assess the degree to which a configuration approaches the GFL. The measure for backtracking is extended to bi-directional flow problems which may occur when a GFL is not achievable because of the job routing.

Keywords:

• job backtracking
• machine location problems
• one dimension