Abstract: (1996). A review of: “Virtual Reality Technology” Grigore Burdea and Philippe Coiffet John Wiley & Sons, Inc., 1994. IIE Transactions: Vol. 28, No. 6, pp. 523-524.

Abstract: The design of a cellular manufacturing system requires that a part population, at least minimally described by its use of process technology (part/machine incidence matrix), be partitioned into part families and that the associated plant equipment be partitioned into machine cells. At the highest level, the objective is to form a set of completely autonomous units such that inter-cell movement of parts is minimized. We present an integer program that is solved using a genetic algorithm (GA) to assist in the design of cellular manufacturing systems. The formulation uses a unique representation scheme for individuals (part/machine partitions) that reduces the size of the cell formation problem and increases the scale of problems that can be solved. This approach offers improved design flexibility by allowing a variety of evaluation functions to be employed and by incorporating design constraints during cell formation. The effectiveness of the GA approach is demonstrated on several problems from the literature.

Abstract: Economic specification limits have typically been developed on the basis of a single quality characteristic. From the viewpoint of the customer, products are often evaluated based on multiple quality characteristics. The specification region for multiple quality characteristics must be determined on an economic basis where we minimize the total loss to both the producer and the customer and thus to the whole society. In this paper a multivariate normal distribution is considered for the quality characteristics. The specification region is given by truncating the multivariate normal distribution. We present the optimization model to develop the specification region for multiple quality characteristics based on the framework of multivariate quality loss function.

Abstract: The traditional Economic Manufacturing Quantity (EMQ) model assumes that the production process (system) is perfect. However, owing to aging, the production process will shift from the ‘in-control’ state to the ‘out-of-control’ state and produce defective items. When the process shift distribution follows an Increasing Failure Rate (IFR) distribution, preventive (scheduled) maintenance policy is usually used to enhance its reliability. In this paper we incorporate a preventive maintenance policy into this deteriorating production system and derive an optimal preventive maintenance policy. Two well-known IFR distributions, Weibull and extreme-value distributions, are considered and some examples are used to illustrate the proposed model. Finally, the advantages of the proposed model are addressed in the conclusion.

Abstract: We examine age replacement and ordering decisions for a system with only one component subject to random failure and with room for only one spare in stock. The system incurs costs for replacement, shortage, holding, and breakage; the lead time for receipt of an ordered spare is constant. We consider the solvability and desirability of jointly optimizing these two traditionally separate decisions. We show that the problem has some convexity properties that make it amenable to minimization. For our data set, we find that using separate optimization gives an average loss of 3% relative to the joint minimum; about a tenth of die time the difference was more than 10%, but in general this loss can vary from zero to arbitrarily large.

Abstract: In this paper we study the effects of increasing component commonality for a single-period model. A two-product, two-level configuration under a general component cost structure is considered. The economic implications of replacing different products' components by common components are analyzed. We develop optimal solutions for the Commonality and Non-Commonality (Basic) Models and provide bounds on the total savings resulting from using commonality. We demonstrate, under general and specific component cost structures, that some forms of commonality may not always be a preferred strategy. Furthermore, we present conditions under which commonality should not be used. Finally, an extension to the two-product multicomponent model is provided.

Abstract: When control charts are used for process monitoring, the traditional practice is to take samples from the process by using a fixed sampling interval (FSI) between samples. Recently developed variable-sampling-interval (VSI) charts vary the sampling interval as a function of the process data to give faster detection of process changes. This paper considers a type of VSI control chart in which samples are always taken at specified equally spaced fixed time points, but additional samples are allowed between these fixed times when indicated by the data from the process. The location of the fixed times would typically be determined by administrative considerations such as testing schedules or by the desirability of sampling according to natural periods in the process. Markov process methods are given for analyzing the performance of these VSI with fixed times (VSIFT) charts. The VSIFT feature is considered for the X¯-chart, the EWMA chart and the CUSUM chart. It is shown that VSIFT charts will detect most proc...

Abstract: Quantitative measures and a procedure for evaluating the ease of disassembly of products when recycling them are presented. A rating scheme is described that allows the designer to translate form properties of a design into quantitative scores, and thus provides a means of identifying weaknesses in the design and comparing alternatives. As part of a broader effort in design for disassembly and recycling, the current work emphasizes the provision of feedback to the designer. The discussion focuses around robotic disassembly for recycling of small electrical appliances; however, the same methodology applies to manual dismantling and other products.

Abstract: We model a U-shaped manufacturing module that operates with fewer workers than machines. Workers move in order around the layout. A definition of the module’s rules of movement are presented. The t...

Abstract: This paper uses Data Envelopment Analysis (DEA) to measure multiple performance criteria for 42 dispatching rules in a job shop environment. We introduce a DEA application in production scheduling. Seven performance measures are considered in the evaluation. Without pre-assigning weights to any performance measure, DEA evaluates the efficiency of each dispatching rule relative to the other rules. After running a large number of experiments, the results show that two extreme subgroups of dispatching rules perform consistently. The shortest processing time related rules form the top group, while the longest processing time related rules form the bottom group. The due date or slack-related rules perform well in tardiness. However, they are ranked low if all seven criteria are considered together. The results provide guidance to scheduling practitioners in choosing priority dispatching rules when there are multiple objectives.

Abstract: Parallel numerically controlled machines can perform multiple machining operations simultaneously using combinations of interacting workholding and tool holding devices. One type of parallel machine, the Mill/Turn, also has the ability to perform both turning and milling operations in the same setup. These machines, in addition to being suitable for large volume machining, also have the potential for efficiently producing small batch sizes. Consequently, Mill/Turns can be used as a rapid prototyping tool. One of the major hurdles to integrating Mill/Turns into manufacturing environments is the absence of computer-aided processing planning systems. This problem is more acute in the parallel-machining domain because process plans for parallel machining are more complicated than their sequential counterparts. In this paper we discuss various aspects of parallel machining that influence the generation of process plans, and describe a process planner that uses a genetic algorithm for sequencing operations. Imp...

Abstract: The purpose of this paper is to propose an analytical method for the performance evaluation of closed-loop production lines with unreliable machines and finite buffers. Such a system consists of a set of K machines separated by buffers of finite capacity. There is a fixed number of pallets circulating in the closed loop. We assume that machines have deterministic processing times but are subject to failures. Failures and repair times are exponentially distributed. We approximate the behavior of this system by a continuous flow model. The continuous flow model is then analyzed with a decomposition technique, which is similar to that used for (open) production lines. Numerical experiments are reported that show that the results provided by this method are in general fairly accurate.

Abstract: The optimal placement of a predetermined amount of buffer capacity in balanced serial production lines is a well-understood problem: in lines with moderate variability, the optimal allocation involves equal numbers of buffers at each site; in lines with severe variability, the equal allocation is modified slightly to place more buffers toward the center of the line. Buffering unbalanced lines is a much less well-understood problem. We study the problem of buffering serial lines with moderate variability and a single bottleneck; i.e., a single station with a larger mean processing time than all other stations. Our analysis shows that a bottleneck station draws buffers toward it, but the optimal allocation depends on the location and severity of the bottleneck, as well as the number of buffers available. Furthermore, relatively large imbalances in mean processing times are required to shift the optimal buffer allocation away from an equal allocation. Finally, line length appears to have a relatively small e...

Abstract: We consider a production facility that produces items for which demand occurs according to a Poisson process. The facility is assumed to deteriorate while it is in operation, with an increasing fai...

Abstract: When production yields are random and orders need to be satisfied in full, several successive production runs may need to be initiated until an order is met. Variants of this multiple lot-sizing pr...

Abstract: Modern statistical process control must often cope with large quantities of highly autocorrelated data. Alwan and Radson (1992) proposed the monitoring of autocorrelated processes by plotting the averages of small batches of data separated by skipping observations. Using results for the AR(1) process, we show that generally better performance can be achieved with no skipping and much larger batch sizes. The resulting batch-means charts derive from methods used in simulation output analysis and can be implemented easily with common digital control systems.

Abstract: In a dynamic environment, such as high-technology industry, a forward picking area requires an intelligent approach to ongoing rewarehousing (reassignment of stock items to locations). The items go...

Abstract: The Warehouse Scheduling Problem is a deterministic multi-item inventory problem with a restriction on warehouse floor space available. We formulate a mixed integer nonlinear programming problem for the objective of minimizing long run inventory holding and order costs per unit of time. We integrate algorithms for staggering orders, described in companion papers, with a heuristic to choose the order sequences. The result is called Sequenced Staggering. We describe a new algorithm to generate order frequencies, called the powers-of-two-factor-of-three technique, as a generalization of Roundy's roundoff technique for powers-of-two policies. We report on a computational study of four hybrid algorithms for solving the warehouse scheduling problem, including the competing algorithm of Gallego, Queyranne, and Simchi-Levi. Based on these results, we recommend the combination of powers-of-two frequencies with Sequenced Staggering.

Abstract: In this paper, a production scheduling problem in glass manufacturing is studied. The production facility consists of multiple identical production lines and each production line includes a number of serially arranged machines. The production is characterized by semi-ordered processing times in each product family, and the last machine in each production line is a bottleneck machine. Significant changeover times are required when products of different families are produced on a production line. The scheduling problem was modeled as a parallel no-delay flowshop scheduling problem (PNDFSP). The PNDFSP combines the parallel machine scheduling problem (PMSP) with the no-delay flowshop scheduling problem (NDFSP). While PMSP and NDFSP have received considerable attention in the literature, PNDFSP has not been well studied. A mixed-integer programming formulation is developed and an efficient heuristic algorithm is proposed. The sequential heuristic algorithm considers simultaneously the line changeover...

Abstract: Many manufacturing systems are controlled with PID-type controllers. In some industries, such as semiconductor manufacturing, specifications or changing conditions impose a need for adjusting such controllers on a run-to-run basis. This need has originated a collection of techniques called run-to-run process control. Self-tuning control, where model estimation is done on-line, has been shown to be a feasible tool for run-to-run control in single input–single output systems. This paper presents a self-tuning multiple input-multiple output controller for run to run control. The controller compensates for a variety of disturbances frequently found in semiconductor manufacturing, such as offsets or shifts and trends. The controller also compensates for autocorrelated responses or noise terms, for coupled responses, and for non-square systems (i.e., the number of inputs may be greater than the number of outputs). A sensitivity analysis is presented to show the performance of the controller under various system...

Abstract: A three-phase network-flow-based procedure is developed for minimizing intercellular part moves in machine-part grouping problems. The unique feature of this methodology is its consideration of several variations related to the number of cells, the number of machines in each cell, and the part family size. The first phase computes a functional relationship between machines on the basis of either a machine-part matrix or actual operation sequences for the parts being considered. The final purpose of this phase is a network modeling of the problem. The second phase partitions the network according to mutually exclusive sets of nodes that represent manufacturing cells. A 0-1 integer programming model and a 0-1 quadratic programming model are discussed and network-flow-based solution procedures are developed. Finally, the third phase identifies the part families. A 0-1 integer programming model is formulated and the solution of this model is again performed through a network approach that allows the identific...

Abstract: We consider a scheduling problem in which n independent and simultaneously available jobs are to be processed on m identical parallel machines. The jobs have to be batched as well as scheduled. The completion time of a job is defined as the completion time of the batch containing it. A constant set-up time is incurred whenever a batch is formed. The problem is to batch and schedule jobs so that the total completion time of the jobs is minimized. We first present some properties and then develop a dynamic programming algorithm to solve this problem. The running time of our algorithm is O(mnm+1). When job processing times are identical, we show that the problem reduces to the corresponding single-machine problem, which has been well solved in the literature.

Abstract: In a complete inspection plan, every finished item is subject to repeated measurements for inspection of quality. The average of these measurements is used to determine its disposition. Items are acceptable and sold at the regular price to the primary market if the average value of repeated measurements meets a lower specification limit. Otherwise the items are sold as scrap at a reduced price. With a consideration of inspection error, this paper presents an economic model to determine the most profitable target value and optimal measuring precision level for a production process. As expected, the model without error consideration is a special case of our model when the inspection precision level approaches infinity. Moreover, the optimal number of repeated measurements is given, based on maximizing the net expected profit per item.

Abstract: The evolution to computer-integrated manufacture (CIM) has been slower than expected. This can be attributed directly to high software development and maintenance costs and the difficulty in achiev...

Abstract: Mixed-model assembly lines are widely used in just-in-time (JIT) production systems. One of the commonly used goals in sequencing mixed-model assembly lines in JIT production systems is to maintain...

Abstract: A group of composite Shewhart-EWMA statistical control schemes were evaluated with simulations. The main results are given in terms of average run-length profiles for each scheme. Results in terms of suggested secondary criteria, percentile points of the run-length distribution of false out-of-control signals, are also given. It is shown that Shewhart-EWMA control schemes using either time-dependent or constant control limits can be found that have better average run-length characteristics than standard Shewhart-Runs Rules schemes. When the secondary criteria are used, only the constant control limit schemes are better than the Shewhart-Runs Rules schemes.

Abstract: Linguistic variables, fuzzy statements and fuzzy algorithms, from the theory of fuzzy sets, provide suitable tools to solve ill-defined problems. Unlike conventional techniques that deal only with discrete conditions, like ‘on’ and ‘off’, and precise numerical values, fuzzy logic offers an alternate technique that deals with non-discrete conditions, such as ‘absolutely important’, ‘quite important’ and ‘less important’. This paper presents a new approach, based on the theory of fuzzy logic, to solve the facility layout problem. The proposed approach considers the multicriteria nature of the layout problem and the fuzziness of the input data through the integration of an expert system and a fuzzy algorithm with a facility layout program. The system generates the best layout that satisfies die qualitative as well as the quantitative constraints on the layout problem. This facilitates the incorporation of the knowledge of facility layout experts. A knowledge-based system, named FLEXPERT, has been developed t...

Abstract: Because product quality is not always perfect in practice, process reliability improvement is an important managerial concern. This study considers this reliability/quality issue in the context of linking production (lot sizing and inventory) and marketing (pricing) decisions. We address some modeling issues of a related previous study. We develop a profit-maximization model, which we investigate under two different decision-making approaches to linking production and marketing (sequential and joint decisions). Calculus and geometric programming are used to solve the model, to compare the decisions from the two approaches analytically, and to develop a practical heuristic approach. The comparative results show that decision patterns can be the opposite of the optimal decisions for the perfect-quality case reported in the literature.

Abstract: In this paper we develop and implement a linear programming model that integrates production and financial planning. We discuss the implementation of the model in a make-to-order type production environment that operates under high inflation. We elaborate on the motivation of the model as well as the difficulties encountered during the implementation. We present the results of the application and discuss various benefits that can be obtained by using the model.