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In this paper, we study the influence of seasonal demands and forecasts on the performance of an Automatic Pipeline, Variable Inventory, Order-Based, Production Control System (APVIOBPCS) using linear control theory. In particular, we consider a system that uses a seasonal forecast based on a no-trend, additive-seasonality exponential-smoothing model, and compare its performance to an equivalent system using simple exponential smoothing. We find that the system with seasonal forecasting significantly outperforms the system with simple exponential smoothing under certain demand assumptions. With optimal parameter settings, the forecast error of the seasonal model can be up to 40% lower. However, we also find that the forecast superiority does not necessarily translate to the performance of the system measured through the bullwhip metrics. In addition, the seasonal forecasting model is very sensitive to the demand frequency and smoothing parameters, while the simple exponential smoothing model is very robust. This implies that the real life benefits of implementing a seasonal forecasting model are not obvious and depend on the particular situation; under a large number of settings (e.g. low seasonality, high-smoothing), the good performance of simple exponential smoothing certainly justifies its popularity in the industry and research worlds alike.

This paper is intended to provide a scoping review on interfaces in service modularity. There is little detailed understanding of this concept despite its attributed importance. We identified 12 papers, showing that interfaces in service modularity are an area still open to research, especially with regard to interfaces that cross organisational boundaries. We found common themes in the available literature: the nature of interfaces, service fragmentation and predefined interfaces. Further research is needed on interfaces in service modularity, especially for complex services with components that stem from multiple, autonomous organisations. More specifically, there is a need for more studies that explore in detail how interfaces manifest themselves, and how they can be addressed to improve complex service provision. In addition, we argue why healthcare could be an interesting domain in which to conduct those studies. Our paper’s contribution comprises a detailed description of interfaces in service modularity, the dissemination of summarised research findings and suggestions for potential future research.

This paper addresses the process of event handling and rescheduling in manufacturing practice. Firms are confronted with many diverse events, such as new or changed orders, machine breakdowns, and material shortages. These events influence the feasibility and optimality of schedules, and thus induce rescheduling. In many manufacturing firms, schedules are created by several human planners. Coordination between them is needed to respond to events adequately. In this paper, the practice of coordination during event handling is analysed by an extensive case study. The study shows that human planners spend much time in communicating events and in negotiating rescheduling solutions. Because many events demand a quick response, the possibilities for coordination are restricted by time constraints. The paper proposes a procedure to structure the event handling process. This procedure helps a scheduler to select an appropriate response to an event by evaluating its influence on schedule feasibility and the time available for coordination and rescheduling. The use of the procedure in the case company has led to improved rescheduling performance through a reduction of scheduler interactions and increasing coordination efficiency. The procedure contributes to traditional planning frameworks and paradigms, and supports the conscious selection and use of rescheduling methods in manufacturing practice.

Advances in production planning and control in recent decades have focused on increasing the sophistication of the planning function. For good reasons, these advances have led to the centralisation of the planning function in production. However, the sophistication of the planning function should be in balance with monitoring and control of the plan. Monitoring and control are by their nature decentralised, beginning on the shop floor, and, therefore, the desire for greater sophistication in monitoring and control leads to renewed interest in decentralised and localised approaches. This paper demonstrates the possibility of using intelligent products for decentralised monitoring and control. Intelligent products are aware of their local context and can negotiate with local manufacturing resources. As such, local solutions to problems can be proposed directly when problems occur. With the advancement of the 'Internet of Things', such a scenario is likely to become feasible in the near future. The paper demonstrates the viability of such an approach through a simulation study, in which robustness is included as an additional measure of performance. The results of the simulations are encouraging.

Warehouse operations are vital for the success of a supply chain. This paper explores fit among warehouse management structure and the context in which the warehouse operates as an important driver of warehouse performance. Warehouse management structure has been operationalised as the extensiveness by which warehouse operations are planned and controlled, and the complexity of the decision rules used for optimisation of the operations. Warehouse performance is measured using data envelopment analysis (DEA). Hypotheses are developed and tested in a survey study among 111 distribution warehouses in the Netherlands and Belgium. Our results show that indeed warehouse management structure should be adapted to context. In order to obtain high warehouse performance more complex warehouse tasks require more and more complex decision rules, and warehouses with more unpredictable demand require fewer tactical plans. These results can help warehouse managers to structure their warehouse management contingent on the context in which the warehouse operates.

The effect of time bucket length on the choice of a lot-splitting approach is studied. Due to the continuing pressure to reduce throughput times and increase efficiency, managers apply various measures, such as lot splitting and cycle time reduction programmes, that change the length of the time bucket in their planning systems. It is shown that the choice for a suitable lot-splitting approach depends on the time bucket length used, so these measures cannot be treated independently as costs may increase rapidly without substantial effect on throughput times. Moreover, the current belief in the lot-splitting literature that the improvements of a variable lot-splitting approach are only marginal compared with an equal sub-batch approach is challenged. Some papers estimate the possible flow time improvement to be less than 5%. It is shown that such statements are not valid as the improvement depends strongly on the type of equal sub-batch strategy applied and the length of the time bucket. Moreover, flow time improvements are accompanied by extra transfer costs, so a cost perspective that includes both effects is more appropriate. The paper shows that equal sub-batching is only effective if information on the time bucket length and on product characteristics is included. At time bucket lengths between one and three days, costs are very sensitive for the type of sub-batching strategy applied. Simulation experiments show that variable sub-batching leads to average cost improvements from 3 to 11%, depending on the time bucket length and the equal sub-batch strategy applied. Lower costs are due to throughput time reductions and transfer cost savings.

Scheduling packaging lines in the process industry is a well known hard problem. The problem becomes even more complicated when each line consists of several machines and an order has to be manufactured on different lines. In this paper we consider the case where a number of orders has to switch from one line to another. This means that an order-run is sometimes manufactured first on the first part of a line and then has to switch to the second part of another packaging line. In this situation the second part of the first line and the first part of the second line cannot be used simultaneously for another run. This situation is studied for the case of the tobacco company Royal Kabat BV. In order to solve the complicated planning problem, the process is partitioned into a Prescheduling Level (PSL) and a Scheduling Level (SL). At the PSL an aggregated plan for a number of successive weeks is made that takes care of the purchasing of packaging materials and the balancing of the capacities. The PSL plan for the current week is the input for the SL at which the actual packaging schedule for that week is made, including the allocation of orders to lines. In this paper we concentrate on the PSL, and our main purpose is to describe the complicated model building process. The model is solved by means of an improvement heuristic on the solution of an LP-relaxation of the model. The computational results show that our partitioning of the problem into a PSL and an SL yields a practically solvable mathematical model; its solutions (i.e. PL plans) are usable for the SL planning and result in practically useful schedules.

E-commerce companies often use manual order-picking systems in their warehouses since these systems can provide the required flexibility and scalability. Manual systems have been widely studied, but the operating policies may require significant changes for e-commerce settings. First, to maintain consumers' loyalty, it is important to maintain delivery reliability even on the busiest days. When the number of order pickers in an area increases, however, more delays due to interactions may occur. For example, travel speed may need to be lowered when order pickers pass each other in narrow aisles. Second, many products sold through e-commerce are returned by consumers. Before these returned products can be sold again, they must be reintegrated in the stock. This paper presents hybrid genetic algorithms to determine routes for simultaneous pickup of products in response to consumers' orders and delivery of returned products to storage locations. Furthermore, interactions between the order pickers are considered in the routing decisions. The developed algorithms use specific warehouse problem characteristics. We identify the mix of pickups and deliveries to realise the highest savings in practice. It is shown that order-picker interactions can be a significant cause for delay and should be accounted for in the routing.

The workload control literature highlights the importance of balancing the shop floor workload, but also acknowledges that this can conflict with processing the most urgent orders – hence, there is a trade-off. In practice, shops contain many complexities, e.g. simultaneous batching and sequence-dependent set-up times that may conflict with processing the most urgent orders and require other solutions than workload balancing to avoid capacity losses. This adds to the trade-off dilemma, which traditionally only considers timing and balancing. This paper develops a framework that determines whether to address a complexity through order release or dispatching. It comprises two dimensions: (i) the typical position of a complexity in the routing of an order and (ii) the criticality of the complexity. A case study is presented, which demonstrates the framework’s utility and illustrates the development of specific solutions designed to handle the complexities. Most complexities present in the case require handling at the order release stage. The challenges of handling multiple complexities at this decision level are evaluated. Finally, the implications for managers and future research are outlined.

International audience; Self-storage warehousing is a rapidly growing industry where consumers or companies can rent storage space for personal or company use, over a certain horizon. This paper addresses the question of how to design the facilities so that revenue can be maximized over a nite horizon, considering multiple demand requirements with respect to size, pricing, location within the facility, climate control, security, or outside access, among others. Using a customer choice model to specify the probability of purchase for each fare product as a function of the set of fare products offered, we propose methods to design self-storage warehouses while allowing different customer choice behaviors. We model the problem as a mixed-integer program and solve it using column generation and branch-and-price algorithms. In addition, we study the impact of re-layout and methods to modify facility layout, since self-storage facilities are relatively fexible in layout and individual storage compartments can be adapted to changes in demand. We validate our model using the data of four self-storage warehouses, and show our method can improve the expected revenue by nearly 11% on average for these cases.

In the past three decades, the magnitude of business dynamics has increased rapidly due to increased complexity, uncertainty and risk of international projects. This fact made it increasingly tough to ‘go alone’ into the international projects. As a consequence, companies with diverse strengths and weaknesses cooperatively bid for joint ventures (JV) formation. Joint venture is also a well-established aspect of the crude oil industry, specifically in the upstream segment. Making decision on the optimal form of JVs is still a challenging problem. In addition, the success of a JV is intertwined with the accuracy of the partner selection phase. Therefore, this paper formulates a multi-criteria mathematical model to select the best partners and form an optimal JV for undertaking oilfield projects. The lexicographic goal programming technique is employed to minimise undesirable deviations from diverse goals such as resources needs (technological and expertise), budgetary requirements, time, etc. The model is validated with a real-life-based example and provides insightful views on alternative formats of cooperation.

The International Journal of Production Research has successfully navigated through its first 50 years while remaining truthful to its initial editorial goals of publishing interdisciplinary work that is both relevant and rigorous. Will the journal be equally successful in the decades to come? Surely, the world has gone through huge changes and we now are part of global interconnected networks that make us vulnerable to new or at least unfamiliar phenomena. We have added expressions like black swans to our lexicon. The world has experienced both natural tsunami and business tsunami, which we term grey swans. This article describes characteristics of these grey swan business tsunami and argues that our current dominant toolkit of parsimonious analytical models may fall short of passing the test of interdisciplinary work that is both relevant and rigorous. IJPR needs to reflect upon what type of papers to encourage to keep on its original course and provides answers on how to deal with today’s grey swans.

The response time of a storage system is mainly influenced by its shape (configuration), the storage assignment and retrieval policies, and the location of the input/output (I/O) points. In this paper, we show that the optimal shape of a storage system, which minimises the response time for single command cycles, is independent of the used storage policy and the location of the I/O point. This means decisions on the shape of the storage system and storage policy can be decoupled. This simplifies system design since at the design stage little information on customer demand is available. The storage system can then be designed for optimality assuming a random storage policy. Such a system optimally accommodates other time-saving storage policies such as class-based or full-turnover-based storage without requiring configuration correction. © 2013 Taylor & Francis.

Workload control (WLC) is a well established production planning and control concept for make-to-order companies. The main insights into WLC are being gained from stationary simulation studies. Knowledge on its functioning in practice is limited, especially in a dynamic setting. The aim of this paper is to identify and classify the key issues when WLC is being used to control logistical performance in a dynamic setting. For this purpose an empirical research project in a company is carried out, in which both quantitative scanning data and qualitative workshop data are obtained and analysed over one year. Throughput diagrams and order progress diagrams support the analysis of the quantitative data obtained. Various types of dynamics could be discerned, but all implying similar requirements in terms of adaptations to the control concept. Whereas research in stationary settings addresses parameter choices, this study shows that it is issues on timing and magnitude of control adjustments that need to be addressed if WLC is to be used effectively in a dynamic setting. The empirical study shows that if the dynamics are not adequately taken into account, buffers may starve while throughput times become uncontrolled over time, despite the use of WLC.

Unit-based pull systems control the throughput time of orders in a production system by limiting the number of orders on the shop floor. In production systems where orders can follow different routings on the shop floor, route-specific pull systems that control the progress of orders on the shop floor by placing limits on the number of orders in (parts of) a routing, have shown to be effective in controlling throughput times. This is because route-specific pull systems are able to create a balanced distribution of the amount of work on the shop floor, which leads to shorter and more reliable throughput times. The placement of limits on work-inprogress in a route-specific pull system determines to a large extent the workload balancing capability of such a system. This paper shows how the placement of work-in-progress limits affects the workload balancing capability and thereby the throughput time performance of a route-specific unit-based pull system, namely POLCA.

In this paper, we investigate how buyers' and suppliers' distinct perceptions of technology uncertainty affect the relationship between communication frequency and supplier performance. Information processing theory suggests that a fit is desirable between perceived environmental uncertainty and the communication processes between organisations. However, if partners in a buyer-supplier relationship do not concur on the high level of technology uncertainty, it is highly questionable whether increased communication will be effective in increasing supplier performance. Using dyadic data from 86 buyer-supplier relationships, involving 388 respondents, we found that communication frequency was positively related to supplier performance only when both suppliers and buyers perceived high levels of technology uncertainty. When buyers perceived greater technology uncertainty than their suppliers, communication frequency was negatively related to supplier performance. The findings in this study show that it is important to take the distinct perceptions of buyers and suppliers of technology uncertainty into account when assessing the effects of communication frequency. It appears that increased communication is only effective when both parties acknowledge the need to communicate, and can be unfavourable when only one party sees the benefits of it.

Cross-training is becoming increasingly important to firms in order to cope with the more stringent performance requirements they are faced with in today's market. However, many firms put considerable effort into cross-training their workers only to find out that their workers favour the familiar tasks and hardly use and maintain the newly acquired skills. In this paper we explore the hypothesis that reducing the amount of work in process in a constant work in process (CONWIP) controlled job shop with worker preferences forces workers to make a more balanced use of the skills they possess. We test this hypothesis by means of a simulation study with the level of cross-training as moderating variable. Based on this study, it can be concluded that the control and limitation of the amount of work in process breaks the pattern of workers remaining at their preferred machines and constrains the workers to use and maintain their other skills more.

POLCA is a material control system designed for make-to-order or engineer-to-order companies. These firms have to cope with a high variety of customised products, and strong pressure to provide short throughput times. POLCA constrains the amount of work in progress on the shop floor in order to achieve a short average shop floor throughput time. Earlier work has shown that the POLCA system has the capability to reduce both the average shop floor throughput time and the average total throughput time, but it is only effective if the POLCA system has been appropriately designed. The design of the POLCA system is therefore being investigated and discussed in this paper. We give an extensive literature review and give attention to the authorisation mechanisms of POLCA, the design of control loops, the route-specific capacity signals (POLCA cards), and specific facilities needed to use the POLCA system in practice. Finally, we report on the design of a POLCA system in practice, the first complete implementation of POLCA in The Netherlands, and present the quick scan that was used in the design of the POLCA system for this SME.

In this paper, we consider a newly designed compact three-dimensional automated storage and retrieval system (AS/RS). The system consists of an automated crane taking care of the pallets' movements in the horizontal and vertical direction. A gravity or powered conveying mechanism takes care of the pallets' depth movement in the rack. Our research objective is to analyze the system performance and optimally dimension the system. For single-command cycles, the crane's expected retrieval travel time is the same for gravity and powered conveyors; we give a closed-form expression. From the expected travel time, we calculate the optimal ratio between three dimensions that minimizes the travel time for a random storage strategy. In addition, we derive an approximate travel time expression for dual command cycles for the system with powered and gravity conveyors, respectively, and use it to optimize the system dimensions. Finally, we illustrate the findings of the study by a practical example.

Today's manufacturing companies have strived to develop a large variety of customer-specified products in an effort to survive and stay competitive. Process platforms have been well recognized as a means for companies to obtain a stable production and thus the economy of scale. A process platform assists companies in configuring similar production processes for producing families of customized products at low costs through managing product and process variety coherently. Within a process platform, all data related to the product and process families are unified as a common generic structure. To shed light on the various constituent elements and complex relationships inherent in a process platform, this paper emphasizes the structural representation of a process platform. A formalism of process platform representation is developed based on the Unified Modelling Language. It consists of a generic product structure, a generic process structure and an integrated generic routing structure. Also reported is a c...

Recent dismal economic conditions and a ruthlessly competitive environment have forced many companies to restructure, or reorganize their priorities. For such companies, the concentration of various resources upon their particular corporate strong points has become a central strategy. Consequently, there has been a rapid increase in the importance of (1) selecting profitable projects from a wealth of possible alternatives and (2) optimizing the allocation of current resources among the selected projects. This paper proposes an optimization system for project selection that not only yields the most beneficial project set, but also the optimum allocation of human resources for the selected projects. The optimization system consists of two algorithms, namely (1) a project selection algorithm for choosing the set of projects that maximizes the total estimated profit, and (2) a human resource allocation algorithm for optimally placing human resources among the selected projects, having considered the satisfact...

Many highly accurate computer tools have been developed for production line design, such as simulation of assembly processes and virtual reality techniques, but these tools require much input information and are generally utilized only in detailed design stages. This paper proposes a rapid analysis method for manual assembly line design, which can be utilized in the conceptual design stage. This method is based on a layout tool with which design engineers can construct assembly line models using 2- and 3-D views, and then employ design evaluation techniques for numerous important criteria such as volume flexibility, and visibility, using the layout data. Spatial evaluation and quantitative efficiency analyses can be simultaneously performed, which enhance collaborative decision-making in the conceptual design stage. This method is applied to an assembly line design for an automobile air-conditioner part as a case study, illustrating the efficiency of utilization in the conceptual design stage that the pro...

The workload control concept is known as a robust shop floor control concept. It is especially suited for the dynamic environment of small- and medium-sized enterprises (SMEs) within the make-to-order sector. Before orders are released to the shop floor, they are collected in an ‘order pool’. To make the release decision, information regarding the actual situation on the shop floor is required. Within SMEs, this information is often incomplete, incorrect or delayed. However, the workload control approaches discussed in the literature assume precise feedback information. The paper discusses the opportunities for information feedback from the shop floor for centralized order release within SMEs and analyses the information requirements of workload control approaches. These approaches are adapted based on more realistic assumptions regarding information supply within SMEs. The different approaches are compared and assessed by a simulation study. Results show that additional investments in more accurate information supply lead to decreasing marginal improvements in overall shop performance. Additionally, they indicate that the choice of the right workload control approach might have important effects on performance.

Almost all the research on the economic lot scheduling problem (ELSP) considering limited shelf life of products has assumed a common cycle approach and an unrealistic assumption of possibility of deliberately reducing the production rate. In many cases, like in food processing industry where limited shelf life for products is common, changing the production rates is not allowed at all because it may result in products with poor quality. In this paper, we allow products to be produced more than once in a cycle and do not allow reducing production rates. We present a modification to the Haessler's basic period procedure to account for the shelf life. Proposed 'branch-and-bound like' procedure exploits these extra constraints to efficiently achieve a feasible solution. Numerical examples are presented to show that our approach outperforms common cycle approach with shelf life considerations.

Labour flexibility is an important issue in the design and development of teams. By means of an analytical study this paper investigates the impact of cross-training on team performance. Four cross-training policies are distinguished and compared according to their effects on important performance measures, such as the load of the bottleneck worker and the number of newly used qualifications seen in various situations. These measures indicate a team's effectiveness and efficiency. Furthermore, they are related to psychological, social and organizational aspects of team functioning. A task assignment heuristic serves as a tool for comparing the cross-training policies. This is applied in an experimental study in which the team situation varies with respect to the cross-training policy, the level of absenteeism, and the variation in the mix of orders. It is shown that a worker-oriented cross-training policy, which attempts to spread multi-functionality evenly among employees, performs well. This policy offers the opportunity to shift work among employees to keep the load of the bottleneck worker low. The required coordination effort for allocating workers to tasks is also relatively low. In line with previous research, this study shows a diminishing positive effect of expanding the level of labour flexibility. The coordination effort required to apply additional flexibility appears to increase linearly with the amount of additional cross-training. The diminishing positive effect and the linearly increasing coordination effort suggest that managers should critically consider the level of labour flexibility in worker teams.