Mustafa Özbayrak

Leanness: experiences from the journey to date

Purpose – Although leanness is certainly not a new concept it is doubtless still relevant. Interestingly, newly developed manufacturing paradigms and systems are always examined in relation to leanness. In other words, leanness serves in most cases as the landmark paradigm with which comparisons are being drawn between the latter and recently pioneered approaches. The purpose of this paper is to highlight the evolutional orbit that leanness has followed over the years and serve as a herald of the current state of this evolution, which will be discussed further, in a separate paper.Design/methodology/approach – A great part of this paper is devoted to highlighting the misconceptions surrounding issues such as what leanness really constitutes and what are the key concepts and practices that leanness encompasses. Two successful lean transition stories are presented showing how these lean tools and techniques were implemented in the cases of two UK‐based manufacturing companies.Findings – Because of its inher...

Activity-based cost estimation in a push/pull advanced manufacturing system

Abstract The objective of this paper is to estimate the manufacturing and product costs by using activity-based costing (ABC) method in an advanced manufacturing system that is run under either material requirements planning (MRP) or just in time (JIT) system. ABC is a method that can overcome many of the limitations of traditional costing systems. This paper reports and discusses the implementation of the ABC alongside a mathematical and simulation model to estimate the manufacturing and product cost in an automated manufacturing system. The potential effects of manufacturing planning and control strategies implemented on financial structure of the manufacturing system are initially analysed. ABC has been used to model the manufacturing and product costs. An extensive analysis has been carried out to calculate the product costs under the two strategies. The comparison of the two strategies in terms of effects on the manufacturing and product costs are carried out to highlight the difference between the two strategies.

A knowledge-based decision support system for the management of parts and tools in FMS

Flexible manufacturing systems (FMS) are very complex systems with large part, tool, and information flows. The aim of this work is to develop a knowledge-based decision support system (KBDSS) for short-term scheduling in FMS strongly influenced by the tool management concept to provide a significant operational control tool for a wide range of machining cells, where a high level of flexibility is demanded, with benefits of more efficient cell utilization, greater tool flow control, and a dependable way of rapidly adjusting short-term production requirements. Development of a knowledge-based system to support the decision making process is justified by the inability of decision makers to diagnose efficiently many of the malfunctions that arise at machine, cell, and entire system levels during manufacturing. In this context, this paper proposes three knowledge-based models to ease the decision making process: an expert production scheduling system, a knowledge-based tool management decision support systems, and a tool management fault diagnosis system. The entire system has been created in a hierarchical manner and comprises more than 400 rules. The expert system (ES) was implemented in a commercial expert system shell, Knowledge Engineering System (KES) Production System (PS).

Systems dynamics modelling of a manufacturing supply chain system

Abstract Supply chains are multifaceted structures focusing on the integration of all the factors involved in the overall process of production and distribution of end products to the customers. Growing interest in supply chain systems has highlighted the need to adopt appropriate approaches that can ensure the efficient management of their complexity, enormity and broadness of scope. With the main aim of supply chain management being to optimise the performance of supply chains, attention is mainly drawn to the development of modelling frameworks that can be utilised to analyse and comprehend the dynamic behaviour of supply chains. While there have been only a few supply chain modelling attempts reported in the literature, this paper proposes a modelling framework that is used to simulate the operation of a supply chain network of moderate complexity. The proposed model comprises four echelons and is build around a central medium-sized manufacturing company operating as a typical Make-to-Order (MTO) system. The developed model was built using a systems dynamics (SD) approach. The operations performed within a supply chain are a function of a great number of key variables which often seem to have strong interrelationships. The ability of understanding the network as a whole, analysing the interactions between the various components of the integrated system and eventually supplying feedback without de-composing it make systems dynamics an ideal methodology for modelling supply chain networks. The objective of the paper is to model the operation of the supply chain network under study and obtain a true reflection of its behaviour. The modelling framework is also used to study the performance of the system under the initial conditions considered and compare it with that obtained by running the system under eight different scenarios concerning commonly addressed real-life operational conditions. The modelling effort has focused on measuring the supply chain system performance in terms of key metrics such as inventory, WIP levels, backlogged orders and customer satisfaction at all four echelons. The study concludes with the analysis of the obtained results and the conclusions drawn from contrasting the system’s performance under each investigated scenario to that of the benchmark model.

Evolutionary algorithms applied to project scheduling problems—a survey of the state-of-the-art

Evolutionary algorithms, a form of meta-heuristic, have been successfully applied to a number of classes of complex combinatorial problems such as the well-studied travelling salesman problem, bin packing problems, etc. They have provided a method other than an exact solution that will, within a reasonable execution time, provide either optimal or near optimal results. In many cases near optimal results are acceptable and the additional resources that may be required to provide exact optimal results prove uneconomical. The class of project scheduling problems (PSP) exhibit a similar type of complexity to the previous mentioned problems, also being NP-hard, and therefore would benefit from solution via meta-heuristic rather than exhaustive search. Improvement to a project schedule in terms of total duration or resource utilisation can be of major financial advantage and therefore near optimal solution via evolutionary techniques should be considered highly applicable. In preparation for further research this paper reviews the application of evolutionary algorithms to the PSP to date extending previous reviews in this area by also encompassing the study of PSP using the design structure matrix. In order to better examine the coverage of this research, this paper also utilises the PSP classification system proposed by (Herroelen, W., Demeulemeester, E. and de Reyck, B., A note on the paper ‘Resource-constrained project scheduling: notation, classification, models and methods’ by Brucker et al ., Euro. J. Op. Res., 2001, 128, 679–688.) to identify the problems being studied in each application and to identify the areas lacking in research. The paper concludes with an examination of areas that in the opinion of the authors would particularly benefit from further research.

Scheduling mixed-model final assembly lines in JIT manufacturing

This paper reports on a new approach to applying simulated annealing to a class of mixed-model sequencing problems. Two major problems are considered: (1) minimizing of actual workload from the ideal workload on the assembly lines; (2) minimizing required set-ups on the assembly lines. The approaches that are found to perform the best are extended for the bicriteria problem considering problems 1 and 2. The sequencing of mixed-model assembly lines in a just-in-time (JIT) production environment is a well-known combinatorial optimization problem. The main purpose of this paper is to use the simulated annealing methodology to schedule JIT production lines. The performance of the proposed method is tested on several problems from the literature and is compared with optimal solutions found so far. Finally, it is shown that solutions obtained by the proposed method are superior to the formal optimal solution. The performance of the method is numerically tested on a standard problem.

How successfully does JIT handle machine breakdowns in an automated manufacturing system

Scheduling a manufacturing system can be one of the most complex tasks in managing an operation. Planning and control systems such as just in time (JIT) can aid scheduling. However, planning and control tools require a fairly stable shopfloor environment to get the best out of them. Many system designs and schedules only consider 100 per cent reliability in machines, and do not take into account random interruptions. In this paper, a simulation model was created to investigate machine and material handling system breakdown problems in a JIT‐driven flexible manufacturing system. Results show that compromises have to be made with JIT control in order to get the best system performance.

Recycling of cutting tools in flexible manufacturing systems

Flexible manufacturing systems (FMS) are complex, with a high variety of entities. In particular, tool management is critically important for timely manufacture. Since a large number of tools flow in a medium-size FMS, it is important to design and operate the tool management system (TMS) to guarantee unmanned and streamlined manufacturing. In this work, a new strategy is developed to minimize the tooling cost by recycling the partially used tools within the manufacturing cell. A particular TMS design strategy, entitled workpiece-oriented tool flow, is considered. Under this strategy, three different tool issue sub-strategies are used to assign tools to available machines. These sub-strategies are measured against cell and tooling performance criteria and are compared to each other with and without recycling. Conclusions are drawn for some different cell configurations and the results are highlighted for different performance criteria.

Tool Management and Job Allocation in Flexible Machining Cells Part 1: Work-Oriented Strategies

In many flexible machining cells, total priority is given to meeting a scheduled list of work orders. The management of the tooling resource required to process these work schedules is also important. This paper presents and investigates strategies for tool management and job allocation in such a demand-driven system, and are termed work oriented. These generic strategies are described, forecasting the required level of tool exchange activity at individual machines according to different sets of issue and return rules. A computational study using industrial data has been conducted to assess the effectiveness of the strategies over a range of different system characteristics and under the influence of two job allocation rules. The model, data and range of parameters are discussed and results are presented and compared. Conclusions are drawn regarding the success of the study, the nature of the data used and the relative performance of the strategies.

Simulation of JIT performance in a printing shop

A medium sized UK based academic publisher own a subsidiary printing business. Presently, Academic Printers (AP) is experiencing production line flow problems reducing the efficiency of the operation. Most of the problems are generated by the imbalanced workflow through the system. By implementing a JIT production planning system it is hoped that some of the production problems can be resolved. Using the simulation software a model was created to investigate the performance of the AP under a variety of operating conditions. Results showed that operating the system with JIT control would not produce economic performance improvements due to constraints applied by the printing process.