Miryam Barad

Flexibility in manufacturing systems: definitions and Petri net modelling

Abstract A discussion on the multi-dimensional character of flexibility is presented and an approach is suggested to define and measure flexibility. Petri nets are used as a design representation of an FMS for the purpose of comparing different systems on a flexibility basis thus unveiling their desirable flexibility properties.

Flexibility in logistic systems--modeling and performance evaluation

Abstract This paper examines potential benefits of flexibility in logistic systems. It briefly reviews flexibility concepts and existing flexibility frameworks before suggesting a bottom-up framework for flexibility in logistic systems. Then, one among the proposed system logistic flexibility types, denoted here trans-routing flexibility, is quantitatively investigated. The research focuses on flexibilitys benefits exclusive of cost considerations. Logistics dependability, a customer oriented logistic performance measure is introduced. The analysis is framed in a multi-factor design of experiments (DOE) that considers factors representing changes in operational and environmental conditions of a logistic system and design factors, such as trans-routing flexibility, acting as countermeasures to changes. The model stems from a military logistics scenario easily adaptable to an industrial or service environment. Using DOE to examine the important interactions between the factor effects contributes to a better understanding of the logistics decision problems and their eventual solutions.

Linking improvement models to manufacturing strategies - a methodology for SMEs and other enterprises

Small Manufacturing Enterprises (SMES) are of major importance to the future economic growth of the European Community. To sustain this role, they need support in defining their specific technological and organizational needs and in finding the right approach to respond to these needs. The main objective of the research described in this article is to develop a supporting methodology for determining the improvement priorities of SMEs through a process similar to the manufacturing strategy formulation. However, the tools and techniques proposed in this paper are of a general nature and need not be restricted to SMEs. The methodology uses Quality Function Deployment (QFD), a product oriented quality technique, to apply a contingency oriented approach to improvement priorities. The essence of the QFD method is to extract the customer needs or desires and then to translate them into technical product quality characteristics. Here, the customers are interviewees from a sample of Small Manufacturing Enterprises. We assume that the manufacturing system improvement needs stem from strategic manufacturing priorities and from concerns that express unsatisfied needs. To propagate the improvement needs from the strategic level to the action level, two QFD oriented matrices were developed. The first matrix was used to define the operating improvement needs of an enterprise while the second was used to determine its improvement priorities. Cluster analysis, a multivariate technique, identified several generic improvement models of the sampled enterprises.

Strategy maps as improvement paths of enterprises

To locate and prioritize the improvement needs of an enterprise, a strategy map merging managerial principles of the BSC with quality principles stemming from the Malcolm Baldridge National Quality Award and the European Foundation for Quality Management is proposed. It comprises four hierarchical levels: business objectives, competitive priorities, core processes and components of the organizational profile. The implementation methodology for supporting its application in an individual enterprise makes use of quality function deployment (QFD), a quality design tool. A strategy map here represents a bottom up cause and effect potential improvement path of an investigated enterprise, starting from an improvement of its organizational profile towards an improved realization of its business objectives, thus providing a global perspective on the important linkages between its weakest components at different hierarchical levels. Analysis of two test cases for implementing strategy maps revealed strategy maps that differed from one company to another and discontinuities in some of the maps. We found processes, considered as core processes by interviewees that did not support any competitive priority and a competitive priority, strongly recommended by interviewees, that was not supported by any core process. Such findings call attention to the complex cause-and-effect relationships influencing the enterprise system behaviour, to the lack of management understanding of this behaviour and eventually they add motivation and support to the continuation of our work here.

House of Strategy (HOS): from strategic objectives to competitve priorities

A challenge to management is creating superior values for its customers and improving financial performances. This paper expresses the customer-oriented perspective of a company in terms of its competitive priorities. It builds on the House of Quality (a customer requirements planning matrix) by developing a House of Strategy for translating the improvement needs of a companys business objectives into relative importance of its competitive priorities. A mean square error (MSE) criterion, supporting the selection of vital competitive priorities to be improved, is suggested. This divides a group of items (here a set of competitive priorities) into two groups: vital few and trivial many. The partition minimizes the overall MSE and by so doing delineates two homogeneous groups. The method is implemented in companies from three industry types. It reveals their different HOS structures and thus provides useful information on the vital competitive priorities to be improved as dictated by their respective business objectives and internal capabilities.

Contribution of quality management tools and practices to project management performance

There is little empirical research that demonstrates a link between quality management practice and better project management performance. Some evidence to this effect is presented and analysed. Reviews two studies that examined the relationship between quality management practice and performance in two areas: manufacturing, and logistics. Next, data are analysed from a survey of project managers in the high‐tech and software industries in Israel. Finally, the results of the survey are integrated with those of previous work, and some insights regarding the contribution of quality management practices to project success are offered.

A break-even quality level approach to location of inspection stations in a multi-stage production process

SUMMARY The break-even quality level concept for a multi-stage production process is introduced and a general model for calculating break-even quality levels between pairs of potential inspection stations, compatible with various formulations of this problem, is developed. The concept itself is intended to contribute to a better understanding of the optimal policy nature. An algorithm, based on this approach and providing an optimal location procedure for perfect inspection, is tested using data examples of imperfect inspection models appearing in literature and optimal solutions are obtained.

A Petri net model for the operational design and analysis of segmented flow topology (SFT) AGV systems

Designing flexible manufacturing systems in general, and flexible material handling system in particular, is a complex problem, typically approached through several stages. Here the focus is on the conceptual design stage during which valid approximation-based methods are needed. The segmented flow topology (SFT) AGV systems were developed to facilitate control of complex automated material handling systems. This paper introduces a decomposition method, directly derived from timed Petri nets (TPN) theories, to calculate the expected utilization of AGVs (as servers of SFT systems) and to derive simple operational decision rules leading to maximum system productivity at steady state, for a given deterministic routeing of discrete material through the manufacturing system.

Timed Petri nets as a verification tool

This paper presents timed Petri nets (TPN) as an analytical approach for verification of computerized queueing network simulation models at steady state. It introduces a generic approach to decomposing a queueing network into separate and independent TPNs, each representing a resource of specific type, such as a processing resource or a transporting resource. A decomposed TPN model enables a quick calculation of the resource expected utilization at steady state thus providing a yard stick against which to verify its long run simulation based utilization estimate. A factorial experimental design frame is applied to investigate the conditions and assumptions affecting the accuracy of the TPN decomposition, as compared to the simulation results. The relatively low differences obtained between the numerical results of the two methods provide evidence that this TPN technique can be used to verify simulation models. Eventual flaws in the computerized simulation model can be detected through observed discrepancies between the TPN based and the simulation results.

Some cultural/geographical styles in quality strategies and quality costs (P.R. China versus Australia)

Abstract The current presentation — rooted in a survey carried out in Israel in the early 1980s — discusses some principles and practices of quality management as emphasised across cultures. It is based on a glimpse into quality practices in P.R. China, which is then compared with some Total Quality Management experiences in Australia. Common traits, exhibiting some similarity to a Japanese style of quality management, could be found among a group of state enterprises in P.R. China, visited in May–June 1992. Distinctive differences are noticed between quality practices in the Chinese companies and those perceived in a small sample of Australian companies, investigated in the period September 1992–January 1993. The differences concern the reason for commencing the program, main improvement objectives, scope of jobs, as well as practice of quality control circles and quality cost reporting. Quality costs, which were reported on a regular basis in all the visited Chinese enterprises, are outlined here as a potential dynamic quality performance indicator.