Order release is a key component of the Workload Control concept. Jobs do not enter the shop floor directly -they are retained in a pre-shop pool and released in time to meet due dates while keeping work-in-process within limits or norms. There are two important groups of release methods: continuous methods, for which the workload falling to a specified level can trigger a release at any moment in time; and, periodic release methods, for which releases take place at fixed intervals. Continuous release methods in general have been shown to outperform periodic release methods. Yet there is incongruence in the results presented in the literature on the relative performance of the various continuous release methods. We use a job shop simulation model to examine the performance of continuous release methods from the literature and find that the contradictory results are explained by the different rules applied to sequence jobs in the pool -a factor neglected in previous work. Finally, a new breed of continuous release methods has recently emerged, but these have not been compared with prior approaches. Therefore, we also examine these methods and show that they significantly improve overall performance, although this is to the detriment of jobs with large processing times.

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Production leveling is an essential element of the Toyota Production System. It aims at balancing production volume as well as production mix to reduce waste, overburden, and unevenness. The application of conventional leveling approaches is limited by the requested product diversity. Because of this production leveling is predominantly used in high volume production. Nevertheless it can be implemented in low volume and high mix production by means of an adapted leveling approach. This approach applies principles of Group Technology for leveling. It uses clustering techniques to group product types into families according to their manufacturing similarity. Based on this, a family-oriented leveling pattern is generated. This paper presents a systematic procedure to level production considering constraints of low volume and high mix production. It describes which grouping criteria can be applied and how product families can be formed for leveling.

Structured AbstractPurpose: To show that Hoshin Kanri has the potential to integrate the operations strategy literature into a coherent structure. Hoshin Kanri's planning process is typically described as a top-down cascading of goals, starting with the senior management's goals and moving to the lowest organizational level. We argue that this misrepresents a firm's actual cognitive processes in practice because: (i) it implies reasoning from the effects to the cause; and (ii) it assumes a direct causal relationship between what the customer wants and what is realizable by the system. Design/methodology/approach: Conceptual; abductive, based on the literature. Findings:The actual strategic thought process executed in an organization consists of three iterative processes: (i) a translation process that derives the desired customer attributes from customer/stakeholder data; (ii) a process of causal inference that predicts realizable customer attributes from a possible system design; and, (iii) an integrative process of strategic choices whereby (i) and (ii) are aligned. Each element relies on different cognitive processes (logical relation, causal relation and choice). Research implications:By aligning the thought and planning processes, the competing concepts of manufacturing strategy are integrated into a coherent structure.Practical implications: Different techniques have to be applied for each of the three elements.Since each element relies on different cognitive processes (logical relation, causal relation and choice), the use of unifying tools (e.g. in the form of matrices, as often presented in the literature) is inappropriate.Originality/value: The first study to focus on the thought processes underpinning manufacturing strategy.

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