STATE-OF-THE-ART SURVEY: OPEN QUEUEING NETWORKS: OPTIMIZATION AND PERFORMANCE EVALUATION MODELS FOR DISCRETE MANUFACTURING SYSTEMS

In this survey we review methods to analyze open queueing network models for discrete manufacturing systems. We focus on design and planning models for job shops. The survey is divided in two parts: in the first we review exact and approximate decomposition methods for performance evaluation models for single and multiple product class networks. The second part reviews optimization models of three categories of problems: the first minimizes capital investment subject to attaining a performance measure (WIP or lead time), the second seeks to optimize the performance measure subject to resource constraints, and the third explores recent research developments in complexity reduction through shop redesign and products partitioning.     

CAPACITY AND PRODUCTION DECISIONS IN STOCHASTIC MANUFACTURING SYSTEMS: AN ASYMPTOTIC OPTIMAL HIERARCHICAL APPROACH

We present a new paradigm of hierarchical decision making in production planning and capacity expansion problems under uncertainty. We show that under reasonable assumptions, the strategic level management can base the capacity decision on aggregated information from the shopfloor, and the operational level management, given this decision, can derive a production plan for the system, without too large a loss in optimality when compared to simultaneous determination of optimal capacity and production decisions. The results are obtained via an asymptotic analysis of a manufacturing system with convex costs, constant demand, and with machines subject to random breakdown and repair. The decision variables are purchase time of a new machine at a given fixed cost and production plans before and after the purchase. The objective is to minimize the discounted costs of investment, production, inventories, and backlogs. If the rate of change in machine states such as up and down is assumed to be much larger than the rate of discounting costs, one obtains a simpler limiting problem in which the random capacity is replaced by its mean. We develop methods for constructing asymptotically optimal decisions for the original problem from the optimal decisions for the limiting problem. We obtain error estimates for these constructed decisions.     

LOT‐SIZING RULE AND FREEZING THE MASTER PRODUCTION SCHEDULE UNDER CAPACITY CONSTRAINT AND DETERMINISTIC DEMAND

This paper investigates the performance impact of lot‐sizing rule (LSR) selection and freezing of the master production schedule (MPS) in multi‐item single‐level systems with a single resource constraint under deterministic demand. The results of the study show that the selection of LSRS and the parameters for freezing the MPS have a significant impact on total cost, schedule instability, and the service level of the system. However, the selection of LSRS does not significantly influence the selection of the MPS freezing parameters. The basic conclusions concerning the performance of the freezing parameters under a capacity constraint agreed with previous research findings without consideration of capacity constraints.     

STRATEGIC PRODUCTION COMPETENCE: CONVERGENT,DISCRIMINANT, AND PREDICTIVE VALIDITY

A resource-based construct of manufacturing competence, termed strategic production competence, is examined with respect to its convergent, discriminant, and predictive validity. The construct evaluates manufacturing performance across a comprehensive domain of competitive priorities relative to item importance and performance. Data from an earlier study of furniture firms (n = 65) are used for statistical testing. The results establish the convergent and discriminant validity of strategic production competence and show that it is positively related to business performance.     

SETUP REDUCTION AND MACHINE AVAILABILITY

This paper is an extension of Billington, who used the framework of the economic production quantity (EPQ) to model setup cost reduction. In the present paper, we use the EPQ model as a starting point to investigate the nature of setup costs and the effect of setup time reduction on the increase in available capacity. Reducing setup is vital to a company's success because a lengthy changeover of machinery is expensive: it demands long production runs to justify its cost, and these, in turn, lead to excessive inventory and to a slow response to customer needs. As in Billington, setup reduction is modeled as a function of an annual amortized investment. The paper examines the behavior of the setup time, the inventory cost, the lot size, and the freeing up of machine time in the face of a capacity constraint. A solution algorithm is provided to find setup times that minimize the sum of setup and holding cost, subject to a constraint on machine availability. The analysis sheds light on the true nature of setup cost and on the opportunity cost of not reducing setups. In the constrained optimization, the Lagrangian multiplier gives an estimate of the marginal value of adding one time unit of machine capacity, or, alternatively, of reducing one unit of setup time.     

THE PLANT LOCATION DECISION IN MULTINATIONAL MANUFACTURING FIRMS: AN EMPIRICAL ANALYSIS OF INTERNATIONAL BUSINESS AND MANUFACTURING STRATEGY PERSPECTIVES

The paper combines perspectives from international business and manufacturing to examine multinational plant location decisions. The location choice in manufacturing is between integrated and independent plants, while the international choice is between a foreign and domestic plant relative to their headquarters' country. The study empirically investigates whether these choices have different plant location determinants using data from a survey of plant managers of large, multinational firms. We find more evidence that the manufacturing choices benefit from consideration of international business issues than vice versa. However, managers rank determinants associated with manufacturing strategy considerably higher than those associated with intemational business.     

TECHNOLOGICAL PROGRESS AND TECHNOLOGY ACQUISITION: STRATEGIC DECISION UNDER UNCERTAINTY

We develop a stochastic programming model to aid manufacturing firms in making strategic decisions in technology acquisition. The proposed model maximizes the firm's expected profit under the condition of the uncertainty in technological progress and development. To solve this large‐scale problem, we decompose future uncertainties through scenarios and then develop an algorithm to solve the resulting non‐linear subproblems efficiently. Finally, we develop a heuristic to eliminate the infeasibility in the master problem and obtain best solutions. Numerical results show that our heuristic solutions are very close to the optimal solutions and meaningful insights are derived.     

PEDAGOGICAL CHALLENGE: TEACHING INTERNATIONAL PRODUCTION AND OPERATIONS MANAGEMENT COURSES

There should be two distinctly different pom introductory courses (or even tracks) for MBAs. Course one (called pom) would consist of traditional pom materials emphasizing domestic POM course materials. Course two, called international production and operations management (ipom), would focus on international aspects of pom, emphasizing cross-boundary operations. Training of instructors differs significantly for the two courses. ipom accentuates operations crossing borders where different languages, cultures and currencies apply. The ipom syllabus employs cases and examples based on companies and/or divisions located in a great variety of countries. Three important drivers of the international pom curriculum should be recognized: (1) supply chain management with ipom responsible for coordinating sources-of materials as well as making and delivering goods and services across global boundaries, (2) portfolio management because ipom can reduce risks by geographically diversifying operations, and (3) capabilities management because ipom must spot, develop and implement special global opportunities. Teaching how these three international drivers interact challenges the pom field to provide proper curriculum development and instructor methodology.     

COMBINED PRODUCTION AND MAINTENANCE SCHEDULING FOR A MULTIPLE‐PRODUCT,SINGLE‐ MACHINE PRODUCTION SYSTEM

Traditionally, the problems of equipment maintenance scheduling and production scheduling in a multi‐product environment have been treated independently. In this paper, we develop a Markov decision process model that simultaneously determines maintenance and production schedules for a multiple‐product, single‐machine production system, accounting for the fact that equipment condition can affect the yield of different product types differently. The problem was motivated by an application in semiconductor manufacturing. After examining structural properties of the optimal policy, we compare the combined method to an approach often used in practice. In the nearly 6,000 test problems studied, the reward from the combined method was an average of more than 25 percent greater than the reward from the traditional method.     

A WORLD OF CITIES: THE CAUSES AND CONSEQUENCES OF URBANIZATION IN POORER COUNTRIES

Historically, urban growth required enough development to grow and transport significant agricultural surpluses or a government effective enough to build an empire. But there has been an explosion of poor mega‐cities over the last 30 years. A simple urban model illustrates that in closed economies, agricultural prosperity leads to more urbanization, but that in an open economy, urbanization increases with agricultural desperation. The challenge of developing world mega‐cities is that poverty and weak governance reduce the ability to address the negative externalities that come with density. This paper models the connection between urban size and institutional failure, and shows that urban anonymity causes institutions to break down. For large cities with weak governments, draconian policies may be the only way to curb negative externalities, suggesting a painful trade‐off between dictatorship and disorder. A simple model suggests that private provision of infrastructure to reduce negative externalities is less costly when city populations are low or institutions are strong, but that public provision can cost less in bigger cities.     

CONSTITUENCIES OF JOURNALS IN PRODUCTION AND OPERATIONS MANAGEMENT: IMPLICATIONS ON REACH AND QUALITY*

I analyzed the contributions made by members of the following constituencies in terms of the number of articles published in the Journal of Operations Management (JOM), Manufacturing and Service Operations Management (M&SOM), and Production and Operations Management (POM): the top 20 U.S. business schools and the top 7 non‐U.S. business schools as ranked by Business Week or U.S. News and World Report, business and government organizations, U.S. business schools ranked between 21 and 50, non‐U.S. business schools not included above, and U.S. business schools not included above. I also analyzed the contributions made by U.S. business schools with top 10 programs in production and operations management; 9 of which are also in the list of top 20 U.S. business schools. Authors from the schools with top 10 programs in production and operations management contributed 20.2% of the articles published in POM and 3.5% of the articles published in JOM during 1997‐2001. They contributed 24.6% of the articles in the eight issues (from July 2000 through June 2002) of M&SOM. During these periods, authors from the top 27 schools contributed 29.3% of the articles published in POM, 9.4% of the articles published in JOM, and 37.4% of the articles to the eight issues of M&SOM. Also during the same periods, authors from business and government organizations contributed 6.6% of the articles published in POM, 1.9% of the articles published in JOM, and 5.8% of the articles published in the eight issues of M&SOM. The findings reported in this paper reflect the reach of the three journals and the perceptions of various constituencies regarding journal quality. The findings about POM and JOM have a very high degree of validity because both journals are more than 10 years old and have well‐established constituencies. The conclusions about the M&SOM constituencies are tentative because it is about 3 years old, and it is still developing its constituencies.     

A COMPARISON OF PRODUCTION SCHEDULING POLICIES ON COSTS,SERVICE LEVEL,AND SCHEDULE CHANGES

We consider a single product, single level, stochastic master production scheduling (Mps ) model where decisions are made under rolling planning horizons. Outcomes of interest are cost, service level, and schedule stability. The subject of this research is the Mps control system: the method used in determining the amount of stock planned for production in each time period. Typically, Mps control systems utilize a single buffer stock. Here, two Mps dual-buffer stock systems are developed and tested by simulation. We extend the data envelopment analysis (dea ) methodology to aid in the evaluation of the simulation results, where Dea serves to increase the scope of the experimental design. Results indicate that the dual-buffer control systems outperform existing policies.     

COMPUTER INTEGRATION AND CATASTROPHIC PROCESS FAILURE IN FLEXIBLE PRODUCTION: AN EMPIRICAL INVESTIGATION

This paper empirically investigates the effect of advanced manufacturing technology on process stability during flexible production in a process industry. A sample of 61 North American fine paper plants is used to examine the relationship between the level of automation installed for controlling changes between paper grades and the incidence of paper web breaks. These web breaks are catastrophic failures; they require the entire plant to be stopped, reinitialized, and restarted. Because a large fraction of breaks occurs shortly after changeovers, they are an important determinant of the aspect of plant flexibility, called mobility, or the ability to move between products with only small penalties. In an attempt to ensure stable and mobile production, many plants have implemented changeover automation. We find, however, that higher levels of this automation are significantly associated with higher rates of catastrophic failure among the plants studied. We suggest that this finding becomes less paradoxical when considered in light of a recent stream of research on advanced manufacturing technologies, loosely called the usability perspective. According to this perspective, automation designed and implemented with the narrow, technical goal of replacing human operators or removing their discretion over a production process is misguided, especially in environments in which requirements are changing rapidly.     

PRODUCTION SCHEDULING OF CONTINUOUS FLOW LINES: MULTIPLE PRODUCTS WITH SETUP TIMES AND COSTS

The problem of production planning and setup scheduling of multiple products on a single facility is studied in this paper. The facility can only produce one product at a time. A setup is required when the production switches from one type of product to another. Both setup times and setup costs are considered. The objective is to determine the setup schedule and production rate for each product that minimize the average total costs, which include the inventory, backlog, and setup costs. Under the assumption of a constant production rate, we obtain the optimal cyclic rotation schedule for the multiple products system. Besides the decision variables studied in the classical economic lot scheduling problem (ELSP), the production rate is also a decision variable in our model. We prove that our solutions improve the results of the classical ELSP.     

AN ANALYSIS AND DISCUSSION OF THE OPTIMIZED PRODUCTION TECHNOLOGY SOFTWARE AND ITS USE

During the 19805 much attention, both pro and con, was directed toward optimized production technology (OPT). Criticism was directed at the proprietary nature of the scheduling algorithms within the software. Despite these criticisms, many large companies installed OPT. Little has been written on how the software is constructed and operates. This article introduces the software, provides a discussion of how it interfaces with management, and how various algorithms are imbedded in the software function. Last, a survey of companies that had implemented the software revealed that the major users are in the automotive industry.     

MODELING LEARNING CURVE AND LEARNING COMPLEMENTARITY FOR RESOURCE ALLOCATION AND PRODUCTION SCHEDULING*

Research on learning effects in mathematical programming models for optimum resource allocation has called attention to the difficulty in solving such models in their original nonlinear form. In this paper, systematically varying sizes of linear segments are designed to approximate productivity changes along the learning curve, and a single separable linear programming model is developed. With production complementarity and learning transmission between products, a more realistic resource allocation and production scheduling problem emerges. Two cases of learning transmissions are considered, and the model design process, which defines a decision problem that can be solved by a simplex algorithm, is demonstrated.     

Education: MRP/GT: A FRAMEWORK FOR PRODUCTION PLANNING AND CONTROL OF CELLULAR MANUFACTURING

American industry typically uses material requirements planning (MRP) for manufacturing control. This paper presents production planning and control procedures based on group technology (GT), which is used in British manufacturing. A translation between these ideas and the American approach is made, and it is suggested that a combination of MRP and GT is viable. The problems that arise, especially in the areas of lot-sizing and sequencing/scheduling, and their possible solutions are discussed. Since increased adoption of GT is expected within the next decade, an intensified research effort is warranted in these and other areas so that existing MRP systems can be modified or extended to handle cellular manufacturing control problems. Subject Areas: Material Requirements Planning and Production/Operations Management.     

CELLULAR PRODUCTION SYSTEMS: A CONCURRENT CLUSTER ANALYTIC FRAMEWORK

We propose an agglomerative heuristic cluster analysis framework for application to the part-family and machine-cell formation problems associated with group technology. This framework addresses the notion of concurrently forming clusters of parts (families) and machines (cells) based on natural between-part and between-machine relationships and the strength of association relating pairs of parts with pairs of machines. An illustrative model is presented and operational aspects demonstrated using a small problem.     

MADE IN THE WORLD: THE GLOBAL SPREAD OF PRODUCTION

We are moving rapidly into an age of transnational manufacturing, where things made in one country are shipped across national borders for further work, storage, sales, repair, remanufacture, recycle, or disposal; but our laws, policies, and management practices are slow in adjusting to this reality. They are often based on inaccurate premises. This article examines these premises and suggests what they imply for management of manufacturing. First, a common view is that manufacturing investment in the industrialized nations is declining and shifting to the developing countries. This is not true. Investment in manufacturing in both industrialized and developing nations is increasing and, in absolute value, there is a lot more investment in industrialized countries than in developing countries. Second, a related view argued by many is that manufacturing does not have a bright future in the rich countries. I argue that manufacturers can thrive in the industrialized countries if they learn how to add more value for the end users. They must go beyond productivity improvement to producing more technologically advanced and customized products, responding faster to changing customer demands, and appending more services to their products. Doing all this is easier in the industrialized countries because the needed skills and infrastructure are more readily available there. Third, another potentially misleading notion is related to why companies invest in manufacturing abroad. Access to low-cost production is not the main motivation in most cases; rather it is access to market. Superior global manufacturers use their foreign factories for much more: to serve their worldwide customers better, preempt competitors, work with sophisticated suppliers, collect critical marketing, technological, and competitive intelligence, and attract talented individuals into the company. They build integrated global production networks, not collections of disjointed factories that are spread internationally. Thus their investment in manufacturing abroad is not a substitute for investment at home, it is a complement. Building and managing such integrated global factor networks is the next challenge in manufacturing.     

INFLATION,MAINTENANCE OF CAPITAL,AND THE IRR MODEL: AN APPRAISAL AND ALTERNATIVE

Capital budgeting under inflationary conditions presents some additional implementation problems when computing the internal rate of return. This paper reviews an earlier proposal made in this journal and concludes that it has some technical deficiencies. Further, it does not have the flexibility needed to be congruent with a wide variety of concepts of capital maintenance and asset evaluation. An algorithm is developed that will permit the user to make a variety of assumptions and then solve for the IRR that is consistent with those assumptions.