A Load‐based and Due‐date‐oriented Approach to Order Review/Release in Job Shops*

In this paper, a new order review/release (ORR) method is proposed for shop floor control systems. The proposed method utilizes both job due date and shop load information to improve the effectiveness of the ORR function in production systems. The performance of the new method is compared to those of a few well‐known ORR methods under four experimental conditions. The results of extensive simulation experiments indicate that the proposed method is superior with respect to the mean absolute deviation measure. In general, it is also better than existing methods for the other performance measures. Furthermore, we show that the proposed method is more robust to variations in system load and processing times than the other ORR methods examined.     

An Evaluation of Capacity Sensitive Order Review and Release Procedures in Job Shops

We investigate the performance of capacity-sensitive order review and release (ORR) procedures in job shop environments that have not been previously explored. Previous research has ignored the case of job shops which must perform to very tight due-dates because of time-sensitive customers. We propose and test a new capacity sensitive ORR procedure called path based bottleneck (PBB) in such environments, along with the modified infinite loading (MIL) procedure which has been shown to work well in several studies. We compare the performance of these two controlled release rules with that of immediate release rule under different conditions of capacity utilization and customer specified exogenous duedates. Our results indicate that PBB performs well in lowering total costs when due-dates are tight, while MIL is a better procedure with relatively loose to medium due-dates. We also show that in many cases, the shortest processing time (SPT) dispatching rule is a superior performer than a due-date based rule like critical ratio (CR); a conclusion which is contrary to the existing research in this area. In addition, the shop floor control policies recommended are shown to be sensitive to the cost structure of the firm. The managerial implications of this research in providing effective shop floor control in job shops operating under tight due-date conditions are also discussed.     

Customer Order Scheduling in a General Job Shop Environment*

The primary objective of this study is to examine the performance of order-based dispatching rules in a general job shop, where the environmental factors are shop utilization and due date tightness. An order is defined as a collection of jobs that are shipped as a group—an order—to the customer, only on completion of the last job of the order. We specifically compare dispatching rules from past job-based studies to some rules adapted to encompass order characteristics. Standard flow time and tardiness measures are used, but in addition, we introduce measures that combine average performance with variation in an attempt to capture the performance of a majority of the orders processed in the shop. Of the 16 dispatching rules tested, our results show that four of the simple rules dominate the others. We also found that order-based rules perform better than their job-based counterparts. The study makes use of multivariate statistical analysis, in addition to the usual univariate tests, which can provide additional insight to managers using multiple criteria in their decision process.     

Workload Control and Order Release: A Lean Solution for Make‐to‐Order Companies

Protecting throughput from variance is the key to achieving lean. Workload control (WLC) accomplishes this in complex make‐to‐order job shops by controlling lead times, capacity, and work‐in‐process (WIP). However, the concept has been dismissed by many authors who believe its order release mechanism reduces the effectiveness of shop floor dispatching and increases work center idleness, thereby also increasing job tardiness results. We show that these problems have been overcome. A WLC order release method known as “LUMS OR” (Lancaster University Management School order release) combines continuous with periodic release, allowing the release of work to be triggered between periodic releases if a work center is starving. This paper refines the method based on the literature (creating “LUMS COR” [Lancaster University Management School corrected order release]) before comparing its performance against the best‐performing purely periodic and continuous release rules across a range of flow directions, from the pure job shop to the general flow shop. Results demonstrate that LUMS COR and the continuous WLC release methods consistently outperform purely periodic release and Constant WIP. LUMS COR is considered the best solution in practice due to its excellent performance and ease of implementation. Findings have significant implications for research and practice: throughput times and job tardiness results can be improved simultaneously and order release and dispatching rules can complement each other. Thus, WLC represents an effective means of implementing lean principles in a make‐to‐order context.     

Interruption and Forgetting in Knowledge‐Intensive Service Environments

An increasing barrier to productivity in knowledge‐intensive work environments is interruptions. Interruptions stop the current job and can induce forgetting in the worker. The induced forgetting can cause re‐work; to complete the interrupted job, additional effort and time is required to return to the same level of job‐specific knowledge the worker had attained prior to the interruption. This research employs primary observational and process data gathered from a hospital radiology department as inputs into a discrete‐event simulation model to estimate the effect of interruptions, forgetting, and re‐work. To help mitigate the effects of interruption‐induced re‐work, we introduce and test the operational policy of sequestering, where some service resources are protected from interruptions. We find that sequestering can improve the overall productivity and cost performance of the system under certain circumstances. We conclude that research examining knowledge‐intensive operations should explicitly consider interruptions and the forgetting rate of the system's human workers or models will overestimate the system's productivity and underestimate its costs.     

ORGANIZATIONAL STRUCTURE OF DUAL-CONSTRAINT JOB SHOPS

This paper describes the results of a simulation study to examine the effects of different organizational structures on the performance of a dual-constraint job shop production system. A hypothetical shop in which machines and workers are constraining resources is the setting of the study. The shop consists of divisions comprised of work centers which, in turn, contain machines to which workers are assigned. There are fewer workers than machines. Variations in organizational structure are achieved by different allocations of a fixed number of work centers to the divisions. Each structure is studied for three levels of labor flexibility. Mean flow-time, flow-time variance, and worker transfers between divisions and work centers are used as performance measures.     

The Impact of Learning and Labor Attrition on Worker Flexibility in Dual Resource Constrained Job Shops

This study investigates the impact of worker learning, worker flexibility, and labor attrition on the system performance of a dual resource constrained (DRC) job-shop. The effects of learning and labor attrition have not been previously addressed in DRC literature. Results from the study, consistent with previous literature, show that the greatest benefits are achieved when inter-departmental worker flexibility is incrementally introduced into the system. In addition, the learning environment, which depends on the initial processing time of jobs and the learning rates of workers, is shown to impact the acquisition of flexibility. The study also shows that the impact of labor attrition on system performance under certain shop conditions may be significant.     

ORGANIZATIONAL SEGMENTATION AND LABOR TRANSFER POLICIES IN LABOR AND MACHINE LIMITED PRODUCTION SYSTEMS

This paper describes a simulation study to examine the effects of different organizational structures on the performance of a dual-constraint job shop production system. A hypothetical shop in which machines and workers are constraining resources is the setting of the study. The shop consists of divisions comprised of work centers which contain machines to which workers are assigned. There are fewer workers than machines. Variations in organizational structure are achieved by segmenting a fixed number of work centers equally into varying numbers of divisions. Mean flow-time, flow-time variance, and worker transfers between divisions and work centers are used as performance measures. Changes in organizational segmentation are shown to affect the performance of the production system and the effects are dependent on the extent to which workers can be transferred between the divisions of the system.     

Impact of operator experience on information feedback and reusability

Keeping a record of operator experience remains a challenge to operation management and a major source of inefficiency in information management. The objective is to develop a framework that enables an explicit presentation of experience based on information use. A purposive sampling method is used to select four small and medium-sized enterprises as case studies. The unit of analysis is the production process in the machine shop. Data collection is by structured interview, observation and documentation. A comparative case analysis is applied. The findings suggest experience is an accumulation of tacit information feedback, which can be made explicit in information use interoperatability matrix. The matrix is conditioned upon information use typology, which is strategic in waste reduction. The limitations include difficulty of participant anonymity where the organisation nominates a participant. Areas for further research include application of the concepts to knowledge management and shop floor resource management.     

Lead Time Management through Expediting in a Continuous Review Inventory System

We consider a continuous review inventory system where delivery lead times can be managed by expediting in‐transit orders shipped from the supplier. First, we propose an ordering/expediting policy and derive expressions for evaluating the operating characteristics of such systems. Second, using extensive numerical experiments, we quantify the benefits of such an expediting policy. Third, we investigate a number of managerial issues. Specifically, we analyze the impact of the number of expediting hubs and their locations along the shipment network on the performance of such systems and offer insights into the design of the shipment network. We show (i) a single expediting hub that is optimally located in a shipment network can capture the majority of cost savings achieved by a multi‐hub system, especially when expediting cost is not low or demand variability is not high; (ii) when expediting time is proportional to the time to destination, for small‐enough or large‐enough demand variations, a single expediting hub located in the middle of the shipment network can capture the majority of cost savings of an optimally located hub; and (iii) in general, hubs close to the retailer significantly drive down costs, whereas hubs close to the supplier may not offer much cost savings.     

Learning How and Learning What: Effects of Tacit and Codified Knowledge on Performance Improvement Following Technology Adoption

This paper examines effects of tacit and codified knowledge on performance improvement as organizations gain experience with a new technology. We draw from knowledge management and learning curve research to predict improvement rate heterogeneity across organizations. We first note that the same technology can present opportunities for improvement along more than one dimension, such as efficiency and breadth of use. We compare improvement for two dimensions: one in which the acquisition of codified knowledge leads to improvement and another in which improvement requires tacit knowledge. We hypothesize that improvement rates across organizations will be more heterogeneous for dimensions of performance that rely on tacit knowledge than for those that rely on codified knowledge (H1), and that group membership stability predicts improvement rates for dimensions relying on tacit knowledge (H2). We further hypothesize that when performance relies on codified knowledge, later adopters should improve more quickly than earlier adopters (H3). All three hypotheses are supported in a study of 15 hospitals learning to use a new surgical technology. Implications for theory and practice are discussed.     

Improving operational performance through knowledge exchange with customers

Drawing upon a knowledge-based view of the supply chain, this study analyses the antecedents and consequences of tacit and explicit knowledge transfer, from the supplier's standpoint. The proposed conceptual model is tested using survey data from a sample of 218 Canadian manufacturers. Results show that the exchange of tacit and explicit knowledge in the context of a relationship between a supplier and a customer has a positive impact on the supplier's operational performance. As expected, tacit knowledge exchange appears to have a stronger impact on performance than explicit knowledge exchange. Results also confirm the importance of the level of integration and inter-firm trust for the exchange of both types of knowledge. Although many studies of knowledge transfer in the supply chain have been published to date, no empirical study has specifically examined the simultaneous effect of both types of knowledge.     

Impact of Storage Assignment Decisions on a Bucket Brigade Order Picking Line

Bucket brigade order picking is a method for retrieving orders from a storage rack where workers follow a fixed sequence and dynamically adjust to variability in work content along the rack. The method is simple and has been shown to provide superior performance in many applications. In this article, we analyze how the location in which products are stored in the rack affects throughput. We identify conditions where storage decisions have a large impact on throughput (e.g., a 20% increase in productivity) and conditions where the impact is minimal. Conditions associated with high impact are high variation in worker skill, high variation in SKU volume, and a moderate level of walking‐to‐picking work content per pick list.     

A Simulation Study of Work-in-Process Inventory Drive Systems and their Effect on Operational Measurements

This simulation study compares three operational measures of performance through the exploration of three work-in-process (WIP) inventory drive systems and their associated inventory buffer characteristics. The three drive systems under study are a push, a pull and a hybrid push-pull system. While these systems have many aspects in common, their buffer management systems do not. The data analysis was based on information gathered from three computer-simulated flow shop assembly lines all operating in the same environment. Hypotheses concerning the operational performance measurements were established, independent variables were controlled and manipulated and a conclusion was drawn as to which system would afford the operation optimum results. While inventory has traditionally been considered and is currently being shown as an asset from an accounting point of view, it is obvious from the findings of this study, that excess WIP inventory, above the minimal requirements for production, may have a negative effect on the operational measurements evaluated.     

Effects of Behavioral Skills Training With Directed Data Collection on the Acquisition of Behavioral Practices by Workers in a Private,Not-for-Profit Child Care Center

Thirty-one workers at a childcare center were observed working with children and data were recorded on their performance of seven behavioral practices. Each week data from observations of individual workers were aggregated into a single data point for each strategy, presented graphically, and posted publicly in the center. Approximately once per month supervisors provided 30 minutes of training (video modeling with directed data collection and discussion) to all workers. Staff reached criterion with training for three skills, and without training for four skills. By study’s end aggregate worker performance was demonstrated at, or above, 80% for all skills.     

Lean Control for Make‐to‐Order Companies: Integrating Customer Enquiry Management and Order Release

A lead time that is short, predictable, and reliable is an increasingly important criterion in supplier selection. Although many companies may achieve this through lean implementation, high‐variety manufacturers, for example, small and medium‐sized make‐to‐order companies, have found that lean's planning and control techniques do not apply. This article outlines a planning and control concept known as workload control (WLC) that integrates customer enquiry management, including a due‐date setting rule, with order release control. Simulation is then used to assess its impact on shop performance. Results demonstrate that an integrated WLC concept can reduce the percentage of tardy jobs—so short lead times can be realistically quoted—while also reducing and stabilizing workloads. WLC can level demand and production over time when work is not standardized and it is not possible to synchronize flows on the shop floor. Results are shown to be robust to changes in routing characteristics, the mix of orders with due dates specified by the customer and proposed internally, and the strike rate (or order‐winning probability). Hence, an integrated approach to WLC represents an important step toward achieving lean in make‐to‐order companies.     

Integrating Knowledge through Information Trading: Examining the Relationship between Boundary Spanning Communication and Individual Performance*

With the global penetration of Internet technologies, individuals may now cross organizational boundaries to communicate efficiently with others regardless of time and space. Thus, when looking for help in solving work tasks, knowledge workers may just as easily contact individuals in rival firms across the globe as a coworker sitting at the next desk. As a result, management faces questions such as (1) How should firms manage employees' knowledge‐sourcing activities when they span both intra‐organizational and extra‐organizational boundaries, and (2) What is the relationship between different knowledge‐sourcing activities and individual performance? Grounded in the knowledge‐based view of the firm, we investigate these questions using data from Europe's largest information technology (IT) services and management consulting company. Our results provide evidence that organizations should support boundary spanning and knowledge sourcing from both internal and external sources. Results suggest (1) a positive relationship between boundary spanning communication and creativity and general performance, and (2) a negative relationship between a reliance on colocated coworkers as knowledge sources and creativity.     

Due Date Assignment,Job Order Release,and Sequencing Interaction in Job Shop Scheduling*

Depending on the techniques employed, the due date assignment, release, and sequencing procedures in job shop scheduling may depend on one another. This research investigates the effects of these interactions with a simulation model of a dynamic five-machine job shop in which early shipments are prohibited. Performance of the system is measured primarily in terms of the total cost (work-in-process cost, finished goods holding cost, and late penalty) incurred by the shop, but a number of non-cost performance measures are also reported. The results support existence of a three-way interaction between the due date, release, and sequencing procedures as well as interaction between shop utilization and procedure combination. Statistical tests are used to identify those rules that perform best both overall and in combination with other rules.     

Rethinking Knowledge: A Bergsonian Critique of the Notion of Tacit Knowledge*

The recent focus on the intangible resources of the organization in general, and specifically the notion of knowledge, has problematized the notion of organization. Rather than seeing organizations as systems that integrate the use of all kinds of physical, financial and human resources, the knowledge‐based view (KBV) of the firm and knowledge management literature emphasize the organization as a site for the development, use of and dissemination of knowledge and other forms of intellectual resources and assets. KBV and knowledge management literature also address the notion of knowledge as such; is knowledge what can be represented by concepts, figures, and statistics, or are there qualities inherent in knowledge that cannot easily be described, disseminated, or procured? The notion of tacit knowledge has been used to denote all forms of knowledge that cannot be represented: knowledge that cannot be fully articulated, expressed in formulas or described in documents. This paper aims to provide a critique of the notion of tacit knowledge as it is used in KBV and knowledge management literature. It examines the notion of tacit knowledge through the philosophy of Henri Bergson and concludes that the notion of tacit knowledge is little more than an umbrella term for unrepresentable knowledge. Thus, the notion of tacit knowledge should be used with care rather than being a residual category of knowledge.     

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.