The relative importance of planning and control systems in achieving good delivery performance

Amongst factors such as quick changeovers and workforce flexibility, managers in 533 UK manufacturing plants ranked a responsive planning and control system as the most important facilitator of good delivery performance on products made-to-order or assembled-to-order. The rankings indicate greater importance to companies in the Household and Engineering sectors than in Process and Electronics, where other factors are dominant. These results are combined with data such as customer lead times and item variety, to characterize and explain differences between the plants in these four sectors. Collectively the results indicate considerable differences in the production planning and control tasks. This implies that general statements on the importance of planning and control systems are inadequate. Practitioners need contextual information in order to ascertain when research is applicable to their circumstances.     

A framework for production control in health care organizations

The paper presents a hierarchical framework for production control of hospitals which deals with the balance between service and efficiency, at all levels of planning and control. The framework is based on an analysis of the design requirements for hospital production control systems. These design requirements are translated into the control functions at different levels of planning required for hospital production control. The framework consists of five levels of planning and control: patient planning and control, patient group planning and control, resources planning and control, patient volumes planning and control and strategic planning, though this last level does not make part of production control as such. Each of the levels of the framework is further elaborated in terms of the decisions made regarding patient flows and resources, and the co-ordination of the different planning levels. Implications of the framework are discussed by describing some points where current practice deviates from assumptions made in our approach. Recommendations for future research and development of the planning framework are formulated.     

The effectiveness of input control based on aggregate versus bottleneck work loads

This study compares input control based on aggregate shop loads with that based on bottleneck resource loads. Two appropriate release mechanisms are developed and compared in flow and job shops that have various levels of a bottleneck constraint. Simulation results show that both the level of bottleneck and the flow pattern influence the effectiveness of the strategies. Release based on aggregate loads works well when shop loads are balanced or when there is a bottleneck but the flow is highly structured, as in a flow shop. Release based on bottleneck loads works best when flow patterns are less structured, as in a job shop.     

A general approach to disassembly planning and control

Closing product and material cycles have emerged as a paradigm for industry in the 21st century, and are directed towards an economical and responsible use of our limited resources. Disassembly plays a key role in recycling. It enables the recovery of functioning components for re-use of pure materials for re-utilization and the separation of harmful substances. Major challenges are presented by the enormous variety of products to be disassembled, by uncertainty as to quantity and by their unknown properties. An appropriate planning and control of disassembly processes is essential for an economic disassembly. Based on an investigation of the suitability of common production planning and control (PPC) methods for disassembly, a specific disassembly planning and control concept (DPC) is outlined.     

Extending the pursuit of flow (lean) management to encompass sales,general and administrative functions

Abstract

Operations management tends to be treated independent of other business functions—the silo syndrome. In this article, we call for operations management (OM) to broaden its perspective by strengthening linkages with other functions of the business, thereby to realize competitive advantages and strategic integration, as well as to avoid resource misallocation. The issues involved are presented and tested by examining the effects of intermeshing sales, general and administrative (SG&A) expenditures with customer-centred flow manufacturing, the latter being measured by system inventory as surrogate for customer lead time. In doing so, we designate trends in total inventory as the independent variable—representative of a dominant target of flow/lean management—and trends in SG&A expenditures as the output variable. The research tasks are enabled by inventory and SG&A data being widely available in companies’ audited financial statements. Such hard data offers methodological and validation advantages over, say, opinion-based survey research. The research adds bulk to existing flow/lean management theory and can be helpful in inducing primary business functions (e.g. OM, finance, sales and marketing) and sub-functions (such as SG&A and management accounting) to engage in cross-functional efforts in the cause of flow-oriented process improvement and company competitiveness.     

A simulation study comparing performance of CONWIP and bottleneck-based release rules

Many firms seeking production economies and quicker throughput times have adopted cellular manufacturing techniques. New product introductions, increased product variety and process changes all add elements of uncertainty to the cell, and dynamic management techniques are required to achieve the benefits expected. This paper considers the problem of managing the flow of material into a manufacturing cell in order to maximize the output rate for a given level of work-inprocess inventory. The manufacturing cell is patterned after an Intel facility that assembles and tests microprocessors for the computer industry. The cell is studied under conditions in which a single bottleneck arises and those under which there are multiple bottlenecks. Alternative procedures for releasing material into the cell are evaluated in order to determine which offer the greatest advantage to managers.     

Production planning and inventory control in a company manufacturing PC parts: A case study

In this paper, we present a case study on the production planning and inventory system in a company manufacturing personal computer (PC) parts. In the case study, the targets are specified for developing a system for production planning and inventory control. The current state of the company is analysed for clarifying the points necessary to achieve the targets. Also, a system based on the analysis is proposed and its effects are estimated.     

Deconstructing bottleneck shiftiness: the impact of bottleneck position on order release control in pure flow shops

Bottleneck shiftiness is an important managerial problem that negatively affects shop floor manageability. It has therefore received much research attention. Yet research has focused on how protective capacity can be used to influence bottleneck shiftiness rather than on assessing its operational impact. The latter is complex to evaluate since changing the degree of bottleneck shiftiness influences utilization, which makes the results of different experimental settings non-comparable. To overcome this problem, we take a different approach. Bottleneck shiftiness is decomposed by investigating its underlying phenomenon: the impact of the bottleneck position. Using simulation, we demonstrate that tighter control can be exercised, and better performance achieved, the further upstream the bottleneck is positioned. It is consequently important to be aware of the direction of the bottleneck shift. If the bottleneck shifts upstream, performance is likely to improve rather than deteriorate as is implicitly assumed in the literature.     

Period batch control: Classic,not outdated

Period Batch Control was developed and first applied during the Second World War. The historic roots are discussed and the principles of this classic production planning approach explained, PBC compared to other production control concepts, and it is demonstrated that it may still be fruitfully applied, especially in combination with cellular manufacturing. It is therefore considered as a classic, but not outdated production planning concept.     

The flow refueling location problem with load flow control

Battery electric vehicles as well as renewable energy are two key factors that can contribute significantly to sustainable development within the transportation and the energy sector. However, the market introduction of these technologies results in new challenges, especially with regard to the interaction between both sectors. So far, neither location models for charging stations nor load flow models for the electrical grid consider these interactions sufficiently. Thus, an integration of planning problems from both sectors is needed in order to exploit potential synergies and to avoid negative impacts.In this paper, we present such an integrated planning approach to locate charging infrastructure for battery electric vehicles considering interactions with the electrical grid. Herein, we combine a charging station location model and a power flow model with integrated energy stores. We aim at determining a network configuration that satisfies the charging demand of battery electric vehicles, herein maximizing the benefits and minimizing the negative impacts resulting from the interactions of the two sectors. To demonstrate the benefit of our integrated planning approach, we apply it to an illustrative case and present results of a sensitivity analysis. We derive managerial insights regarding the interdependencies of the number of sited charging stations and the installed storage capacity based on renewable energy generation and charging demand.     

Flexible reasoning using sensible agent-based systems: A case study in job flow scheduling

Planning and control systems for highly dynamic and uncertain manufacturing environments require adaptive flexibility and decision-making capabilities. Modern distributed manufacturing systems assess the utility of planning and executing solutions for both system goals (e.g. minimize manufacturing production time for all parts or minimize WIP) and local goals (e.g. expedite part A production schedule or maximize machine X utilization). Sensible Agents have the ability to alter their autonomy levels to choose among a set of decision models in order to handle the differences between local and system goals. In this paper, Sensible Agents are applied to a production planning and control problem in the context of job shop scheduling and decision model theory. Sensible Agents provide for trade-off reasoning mechanisms among system and local utilities that are flexible and responsive to an agent's abilities, situational context and position in the organizational structure of the system.     

Production planning and control tools

There are numerous tools available to be used for production planning and control purposes. The number of tools is ever increasing, and so are the levels of sophistication as well as complexity. For the specific manufacturing firm, the task of selecting the most appropriate set of tools is not trivial. However, in recent years, the understanding of the relationship between tools and manufacturing environments for which they are suitable has increased. The purpose of this paper is to provide an overview of production planning and control tools available today, as well as new trends, issues and ideas.     

A new method for order release

A new method for determining when to release jobs into a probabilistic manufacturing line is described. This new heuristic releases jobs only if their predicted waiting times are sufficiently estimated using simulation. Moreover, we use simulation to examine the performance of this heuristic and others CONWIP, Starvation Avoidance for a manufacturing flow line with exponential machine processing, failure, and repair times. The reasons why it is appropriate to compare order release mechanisms using tradeoff curves of lead time versus customer service are described. The simulation experiments show that the new 'waiting time heuristic' is superior to other order release mechanisms in situations where low lead time is required. small. Waiting times are     

Employee reactions to behavioural control under conditions of stress: The moderating role of self-efficacy

Extensive research conducted in the occupational stress literature has failed to provide convincing support for the stress-buffering effects of work control on employee adjustment. Drawing on research conducted in the laboratory context, it was proposed that the stress-buffering effects of work control on employee adjustment would be more marked at high, rather than low, levels of self-efficacy. In a sample of 100 customer service representatives, a significant three-way interaction among role conflict, work control and self-efficacy (measured at Time 1) was observed on (low) depersonalization (measured at Time 2). Consistent with expectations, work control reduced the negative effects of work stress on this outcome measure only for employees who perceived high levels of self-efficacy at work. In addition, there was evidence to suggest that self-efficacy moderated the main effects of work control on job satisfaction and somatic health. These findings are discussed in terms of their theoretical contribution to the job strain model, and also in relation to workplace interventions designed to improve levels of employee adjustment.     

The impact of non-bottleneck variation in a manufacturing cell

Protective capacity is the 'extra' capacity placed at non-bottleneck resources to absorb random disruptions in planned levels of performance so that the bottleneck resource continues to be effectively utilized. A full factorial experiment with a simulation model was conducted to explore issues associated with the quantity and location of processing variance in a five-station manufacturing cell. The cell's performance was measured using both mean flow time ( MFT ) and bottleneck shiftiness ( SHIFT ) for 3 patterns of variance for the non-bottlenecks at 5 different levels of variation. In order to investigate the importance of the quantity of added capacity on the variation both a low level of protective capacity (10%) and a high level (50%) were considered. The results indicate that having the higher variation work centres close to the bottleneck provides reduced MFT and SHIFT . The performance measures improved at both the low and high setting of protective capacity.     

Neural networks in production planning and control

The purpose of this paper is to present a selection of the most significant ANN (artificial neural network) applications used to solve PPC (production planning and control) problems. Therefore, the paper itself is a reasoned classification rather than a simple survey. The PPC domain is divided into various areas, and for each area one or more examples of ANNs are discussed, together with the benefits and drawbacks of their application to that particular area. Finally, two case studies developed by the authors are reported and discussed to analyse the main implementation problems to be considered when using ANNs.     

Manufacturing cycle time reduction using balance control in the semiconductor fabrication line

In semiconductor manufacturing, wafer fabrication is the most complicated and important process, and is composed of several hundred process steps and involves several hundred machines. The productivity of the manufacturing process depends mainly on controlling the balance of WIP (work-inprogress) flow to achieve maximum throughput under short manufacturing cycle times. This paper discusses how to determine the proper WIP level for operations, against which balance status can be measured. Balance measurement can be applied in mathematical modelling for bottleneck scheduling and operations management of the fabrication line. Performances are evaluated through computational experiments to show that balance driven management leads to 15-33% more production in 21% shorter manufacturing cycle time than production driven management.     

Decentralized WIP-oriented manufacturing control (DEWIP)

DEWIP is a manufacturing control system for job shop environments aiming at achieving short and reliable lead times by establishing WIP control loops between the manufacturing work centres. The paper describes the mode of function, the setting of parameters and simulation results of the new manufacturing control system. The setting of parameters is done with the aid of the funnel model and the theory of logistic operating curves, both developed at the Institute of Production Systems at the University of Hanover. The simulation is conducted using industrial data and makes it possible to assess DEWIP with regard to lead times, WIP level, performance and schedule reliability. DEWIP is compared both with an uncontrolled process and with the manufacturing control systems Load oriented order release (LOOR), Conwip and Polca. The results suggest that DEWIP and the models employed for the setting of parameters are suitable for job shop production and therefore offer a valuable alternative to prevailing centralized manufacturing control systems.