Richard Barson

Are push and pull systems really so different

A distinction is frequently made between push and pull production planning and control systems. Many people believe that pull systems are inherently better at reducing stocks because they try to eliminate queues, not provide for them, whereas push systems encourage queues to cushion operations and to increase work station utilisation but at higher cost. However, the definitions of push and pull are inconsistent between different researchers. Worse, arguments about performance are sometimes circular. Thus, if the performance of a pull system is poor then it may be suggested that this is because the fundamentals of JIT are not being observed, whereas, if the performance of a push system is poor, then that is a consequence of it being a push system. After defining push and pull systems, this paper examines, by means of simulation, the effect that push and pull information flows have on system performance, under a variety of conditions. In particular, the performance of both push and pull information flow systems are considered in conjunction with high-quality levels, small set-ups and small batches, i.e. the conditions normally associated with JIT continuous improvement programmes. Similarly, the performance of both push and pull information flow systems are investigated in the presence of conditions such as large set-up times, which are frequently eliminated as part of a continuous improvement programme. The question investigated in this study is how system performance is affected by the flow of control information. The investigation uses models of the material and information flows of push and pull systems to examine the conditions which affect performance. A production sequence is chosen which consists of ordering materials, making parts and assembling products which are then despatched to customers. A set of decision rules is used to operate the systems using different demand and inventory level data.

The application of case based reasoning to decision support in new product development

This paper describes the application of case based reasoning (CBR) to decision support for design managers and engineers during the early phases of new product development projects, in a concurrent engineering environment. The paper discusses the rationale of using CBR, emphasising its suitability for ill‐defined, unstructured problems, in comparison with traditional knowledge‐based systems. The overall research approach is presented, the importance of case collection, case base maintenance and user training is highlighted and the pre‐requisites for effective use of the system are discussed. Finally, the benefits and costs of the CBR system, as perceived by the user companies, are discussed. The experimental nature of the approach is emphasised and it is shown that the industrial environment for which the system is designed and in which it is used has great bearing on its capability.

Analysing organisational issues in concurrent new product development

Abstract Organisation analysis and improvement techniques have been a field of study for many years with the result that there are a number of different methodologies ranging from purely mathematical models of analysis to heuristic models using simulation. This paper presents an overview of research carried out towards the development of a methodology and tool aimed at assisting in the reengineering of the processes and organisation deployed in Concurrent New Product Development (CNPD) (NPD within a Concurrent Engineering (CE) environment). The focus is on the analysis of the operation of multifunctional project teams throughout the NPD process lifecycle, using process modelling and analysis techniques. The methodology and tools developed identify low value adding tasks and poor value adding ability of the performers, using both quantitative as well as qualitative information. This enables the company managers to reduce lead times, remove weak functions or links, move towards a more flatter organisation, and improve performance of the process and consequently organisation. The methodology and tool were originally developed within the European BRITE-EURAM (No. BE-8037-93) project PACE – a Practical Approach to Concurrent Engineering

The application of business process modelling to organisational analysis of concurrent engineering environments

Abstract Barriers to Concurrent Engineering (CE) or Integrated Product Development (IPD) are organisational in context. Consequently to facilitate CE, significant changes to the design and development of the organisation need to be considered. Both research and practice have demonstrated that companies which invest in improving organisational development issues fair better than those that rely purely on tools and technology alone. The key issues are improving cross-functional integration and developing social mechanisms that facilitate a collaborative environment. The first step in improving an organisation design is of course organisational analysis. Organisational Analysis techniques have been a field of study for many years, resulting in the development of a number of different methodologies ranging from purely mathematical models of analysis to heuristic models using simulation. This paper presents a methodology, which draws upon traditional organisational theory and combines it with the more recent business process re-engineering approaches, for the analysis of organisational issues in a CE environment. The methodology is based on the hierarchical modelling and analysis of the business process. A detailed case study of its application in industry is presented. The paper concludes by summarising the key features of the methodology and issues emerging from its implementation.

Academic and Industrial User Needs for a Concurrent Engineering Computer Simulation Game

This paper describes the rationale of a multimedia computer based simulation game of concurrent engineering for use on university engineering courses and for the training of engineers in industry. It describes the methodology and results of the analysis of academic and industrial user needs. This included interviews and focus groups with users and players of the simulation. The learning goals for the simulation were developed from this analysis. These learning goals and the insights gained were used as an input in the development of a simulation modelling methodology and computer simulation model of CE. The outcome of the development methodology was the first prototype of the COSIGA CE simulation game. This prototype is currently undergoing testing, including assessing how well it delivers the learning goals. The game will aim to realistically simulate the collaborative and cooperative process of product development inherent in a concurrent engineering approach. It is a team player game, played by up to five people. It can be played by individuals in the same room or in a distributed group, using the internet and telecommunications (phone, fax, videophone, etc). Each person plays a role in the product development process and work collaboratively together, using whatever communication means they choose, to specify, design, and produce the final product - a type of truck. This would involve them drawing up a market specification, a product specification, designing the product and allocating production processes. The products manufacturability will be put to the test in the simulated factory to produce the final products. The final products conformance to specification, development time and costs are used to calculate the teams score. This two year project will make the final simulation game available on CD-Rom (with a demo version available on the internet) for use by other universities and industrial companies.

Establishing Concordance within Concurrent Engineering Teams

This paper describes how collocated teams can be analysed using process modelling and analysis (of organisational and management issues) to achieve a culture of concordance or mutual agreement between different parties within CE (product develop ment) teams. The benefits of teams are described, in particular, the need to create a collaborative environment. After establishing the need for analysis of such teams a process modelling and analysis methodology is described. The methodology attempts to address the issues concerned within CE teams from a process perspective. The methodology and supporting tools hence act as an aid for managers in the organisation and management of the Concurrent New Product Development process and CE teams. A case study of a domestic appliance manufacturer developing a new product using a collocated product development team is described to verify the benefits of collocation, and process modelling and analysis. The issues that emerge from this type of approach to improving the performance of CE teams and product development management are discussed. The paper ends by proposing that the main factors contributing to the suc cess of this approach (to improve the culture and operations of CE teams in terms of achieving concordance) are: commitment from top management, participation of both intra- and inter-organisational members, integration of organisation and technology, and building rela tionships between the active players.

Inventory and enterprise integration

Abstract Inventory planning and control is concerned with determining which items to stock, and when and how much stock to order. These primary decisions exist alongside other operational problems of receipt, storage, issue and maintaining stock records. Additional information, such as the location and value of the stock held, stock turn, Pareto analysis etc., is needed for wider management control. In short, practical inventory systems maintain stock records and order stock but they also provide management information on shortages, movements and financial implications. However, inventory systems exist in a rapidly changing environment and the level of inventory is often a consequence of other factors, such as the effectiveness of MRP and supply chain management, rather than the models which determine ‘when’ and ‘how much’. The paper presents a hierarchical approach which uses a simplified top level model of a company to provide an approximate assessment of whether a proposal is satisfactory before moving down a hierarchy of more detailed models to investigate performance in greater detail. The approach is illustrated by using the UNISON systems analysis tool and modelling software to examine the inventory consequences of system options. The consequences of proposed manufacturing system options and investments are explored dynamically in terms of inventory levels, delivery performance and cash flows.

A Petri-net Representation of Computer-aided Production Management

This paper discusses part of a SERC funded investigation into computer aided production management. The broad objective is to produce a framework within which developments in practice, simulation and theory can be brought together so as to aid the production manager. A range of approaches for representing and recording production management systems has been investigated and Petri-nets is one of the methods examined. Petri-nets can be used to model the flow of information and control of actions in a system.

NECTAR — A Graphical Technique to Represent the Component Produced from the Cutter Path of a Numerically Controlled Milling Machine

Summary NECTAR ( N um E rically C ontrolled T ool p A th R epresentation) Is a computer graphics program which given the tool path of a cutter will produce a pictorial representation of the component which will be produced by that cutter in a billet of specified dimensions. This technique has potential use in two areas:- firstly it will enable machine control tapes to be proved away from the machine tool; the pictures produced as part of the current tape proving techniques are essentially only a plot of the cutter centre line path and as such they can be very misleading. Secondly this technique opens up the possibility of eliminating much of the role of the part-programmer, since a CAD designer has the ability to see directly how the component described in his data base will look as a finished workpiece once the part has been processed and post-processed automatically.

Constructing a natural language for describing work tasks

This paper presents a natural language for describing work tasks. It was developed for use with a software package (IDEA), designed for the analysis of manual assembly tasks. Among the functions of the software are health and safety evaluation, work task simulation, time estimation and ergonomic analysis. The language provides users with a simple and intuitive method for entering task descriptions to be used as the basis for workstation or work task analysis, for example using a human model, carrying out a time estimation or assessing human reliability.