Mike Byrne

Production planning using a hybrid simulation - analytical approach

Abstract The “Multi Period Multi Product (MPMP) Production Planning Problem” is well known in the literature. The problem essentially consists of matching production levels of individual products to fluctuations of demand for a number of periods into the future, subject to constraints of capacity. Solution approaches to this problem can be categorised in two classes: Analytic methods (mathematical programming, numerical search etc.) and simulation. The choice of approach is based on issues such as the complexity and linearity of the system functions. In the literature analytic modelling and simulation have often been presented as mutually exclusive alternative methods for solving problems. Thus, the well known relative advantages of the alternative technique not chosen might be sacrificed. Furthermore, the results obtained may either lack accuracy and realism, or be too complex to be easily interpreted. It may therefore be preferable to use a hybrid approach that combines aspects of both of these alternatives. Such an integrated approach is presented here. This paper studies a hybrid algorithm combining mathematical programming and simulation models of a manufacturing system for the MPMP problem, and demonstrates how the analytic model working in co-operation with the simulation model can give better results than either method alone. The resulting production plan can be both mathematically optimal and practically feasible.

Real-time operational control of an FMS with full routing flexibility

Abstract This paper considers the operational control of an FMS with flexible alternative machines and flexible alternative operation sequences (full routing flexibility). Several policies are presented which can select in real-time the next operation for a part, and the machine to perform that operation, given that flexible process plans are available. These policies were examined by simulation of an eight-machine FMS model under several operating conditions against several performance measures. Results indicate that the system performance is at its best using a policy which seeks to balance the workload between machines while also minimising the distance travelled by the parts.

Delivery reliability, manufacturing capabilities and new models of manufacturing efficiency

Purpose – To provide a selective bibliography on reported empirical evidence regarding the compatibility/trade‐offs relationships between delivery reliability and other manufacturing capabilities, and also identify specific areas for future research.Design/methodology/approach – The paper conceptually examines published studies which have reported a trade‐off/compatibility situation between delivery reliability and other manufacturing capabilities such as internal quality, external quality, manufacturing costs, inventory costs, etc. Some different aspects of delivery reliability are also discussed.Findings – Principally, the paper identifies a need to study in more detail the different variables (manufacturing capabilities, contextual variables and manufacturing practices) that could be potentially associated with the achievement of high manufacturing efficiency (high levels of outputs/low levels of inputs) in terms of delivery reliability, materials inventory and safety resources.Research limitations/imp...

Stochastic linear optimisation of an MPMP production planning model

The subject of this paper is to study a realistic planning environment for a multi-product multi-period problem with stochastic demand. We develop here a new demand stochastic LP model based mainly on the two-stage deterministic equivalent problem. In this paper, the normally distributed stochastic demand is approximated by a discrete approximation method.

Manufacturing capabilities and performance: a critical analysis and review

In order to advance scientific knowledge, it is important to maintain consistency regarding the methodologies and units/levels of analysis employed to test a theorys main claims. Thus, this investigation provides a critical examination of the papers that have aimed to test the trade-off model and its competing concepts. The analysis focuses on the methodologies used to examine the validity of such models and theories, and also on the operationalisation of the variables that represent the level of analysis by which those theories are tested. To aid in the investigation, a framework to distinguish measures of performance with an internal and external reference and perspective is proposed. The results show that current methodologies, approaches and rationales used to determine the validity of the trade-off model or its rival concepts observe important limitations, as they do not address the trade-off models core principles. Those limitations in turn make the results of those studies questionable. Consequently, it is proposed that in order to advance theory in our field, more consistent methods and approaches should be utilised.

A simulation study of bottleneck scheduling

Abstract Over the past thirty years three main approaches for controlling the flow of materials, both into and through manufacturing organisations have been developed. Numerous papers exist which compare Material Requirements planning (MRP), Just-In-Time (JIT) and Optimised Production Technology (OPT), in an attempt to establish which is best. However, it is becoming increasingly apparent to both academics and industrialists that each of the above methods can make a positive contribution to the performance of the organisation if adopted. Research suggests that MRP, JIT and OPT, are in fact quite complementary and an outline framework for their integration is presented in the first part of this paper. Using computer simulation the authors examined aspects of the OPT philosophy and some preliminary results of this work are presented. These suggest that taking account of bottleneck resources when scheduling impacts favourably on performance. In conclusion it is argued that bottleneck scheduling could be the first step in developing an integrated approach to materials control.

Strategic consensus on manufacturing competitive priorities

Purpose – The purpose of this paper is to provide a critical analysis of studies on strategic consensus along manufacturing competitive priorities. Based on this analysis, a new methodology to measure strategic consensus on manufacturing competitive priorities that is more consistent with mainstream operations management theory is proposed. The paper also includes novel proposals for future research.Design/methodology/approach – The new methodology and proposals for research are mainly based on a literature review of previous studies on strategic consensus regarding manufacturing competitive priorities and also on relevant research and works in the field of operations management.Findings – Previous methodologies used to measure strategic consensus regarding manufacturing competitive priorities are mainly based on studies in the business strategy field. Thus, these methodologies are deemed as inadequate in the operations management field. It is also found that there are very few studies that have analysed ...

A combined switching algorithm and linear decision rule approach to production planning

The problem of medium term production planning and control is compounded in many manufacturing concerns by the wide variety of products and by the presence of stochastic variables. This paper presents a simple heuristic approach to the problem by essentially combining a simple linear decision rule with a switching algorithm to give multi-product control operating within capacity limits. The approach is examined in depth by description of an industrial study and the results of the study suggest that the method requires little computing time, that it is conceptually simple and that it gives good results. It is suggested that the approach could be extremely useful in a wide variety of batch manufacturing environments.

Comprehensive simulation analysis of a flexible hybrid assembly system

A comprehensive analysis of a flexible hybrid assembly system (FHAS) where automated devices and human operators interact is presented. A computer simulation programme and ANOVA were conducted to identify which factors significantly affect the measures of performance of the system. The results clearly indicated that certain factors have a more significant effect on the measures of performance than the others. A classification of the relative significance of input factors affecting such a system is made. In order to investigate the generality of the results, alternative station configurations and factor levels are examined. The outcome shows that the results are applicable to different configurations of FHAS.

Multi-item production lot sizing using a search simulation approach

Abstract The selection of appropriate lot sizes for a number of items sharing common manufacturing facilities is a complex problem. Simple approaches such as the Economic Order Quantity model are not generally suitable in such an environment with its variable and stochastic demands and lead times, and with complex interactions between the different products and resources of the system. This paper presents an approach to the multi-item production lot sizing problem based on the use of simulation to model the interactions occurring in the system. A search algorithm is used to adjust the lot sizes on the basis of the results of previous simulation runs, with the objective of achieving a minimum total cost solution.