The structuring of production control systems

Co-ordination of the activities of production units is necessary to realise the required delivery performance in the market. These should not conflict with reaching the production economics objectives of each of the units. Production structure is needed to reduce the complexity and should minimise the loss of potential flexibility. Any structure will have some elements in common — the definition of basic elements (e.g. capacities) as a first step in production control structure design; the introduction of product units and the decomposition of the total production control to Goods Flow Control and Production Unit Control; the relationship of sales and manufacturing and the interference of products and capacities as two main determining factors of the Goods Flow Control structure. The generality of these elements means it is possible to develop a small but relatively complete set of reference structures. A reference structure for Goods Flow Control in a repetitive manufacturing situation is discussed. Its main elements are master planning, material co-ordination, workload control and work order release

Optimising workload norms: The influence of shop floor characteristics on setting workload norms for the workload control concept

Workload control (WLC) is a leading production planning and control (PPC) solution for small to medium sized enterprises (SMEs) and make-to-order (MTO) companies, but when WLC is implemented, practitioners find it difficult to determine suitable workload norms to obtain optimum performance. Theory has provided some solutions (e.g., based on linear programming) but, to remain optimal, these require the regular feedback of detailed information from the shop floor about the status of work-in-process (WIP), and are therefore often impractical. This paper seeks to predict workload norms without such feedback requirements, analysing the influence of shop floor characteristics on the workload norm. The shop parameters considered are flow characteristics (from an undirected pure job shop to a directed general flow shop), and the number of possible work centres in the routing of a job (i.e., the routing length). Using simulation and optimisation software, the workload norm resulting in optimum performance is determined for each work centre for two aggregate load-oriented WLC approaches: the classical and corrected load methods. Results suggest that the performance of the classical approach is heavily affected by shop floor characteristics but no direct relationship between the characteristics and norm to apply could be established. In contrast, results suggest that the performance of the corrected load approach is not influenced by shop floor characteristics and the workload norm which results in optimum performance is the same for all experiments. Given the changing nature of MTO production and the difficulties encountered with the classical approach, the corrected load approach is considered a better and more robust option for implementation in practice. Future simulations should investigate the influence of differing capacities across work centres on the workload norm while action research should be conducted to apply the findings in practice