Integrated DEsign and Modeling

Category: Type 1 Model

Comments: The IDEM - Methodology for factory modeling is a project of Loughborough University.

Just automating parts of a manufacturing facility is not enough to keep pace with the competitive environment. Thus, we need to take into account integration of these parts. Existing factories need to be redesigned or even an entirely new plant needs to be developed to remain competitive. Hence, is a need for a comprehensive factory modeling methodology. A lot of limitations exist in the available modeling techniques like not accurately representing the hierarchical nature of many factory systems. The IDEM methodology aims at overcoming these limitations and providing a methodology which can reduce the effort to model a factory.

The IDEM modeling technique consists of: conceptual modeling, approximate modeling, and detailed modeling. The conceptual modeling consists of the aims of the upper level management in the re-organization. They also set the scope and context of reorganization. Then an approximate model is constructed. This approximate model should be approximate enough not to be too detailed and cumbersome without compromising on the main aspects of the factory. Then areas of the factory are considered and the detailed modeling is done.

Another problem which arises, is the lack of modeling tools that model the factory from different viewpoints (ex functional, information, etc.). Some tools model the functional view well but do not model other views well. By doing this some of the important information of the model is lost. To solve this problem, a multi view modeling technique is needed. The IDEM method uses three different views - function, dynamic and information view. The function view models all the functions that take place. IDEF0 is the basis of the IDEM function view since it can accurately model the hierarchical structure and the inputs, outputs, controls and mechanisms. The information view shows the information flows in the model and the dynamic view shows the way the model behaves with time.

The IDEM technique is an alternative to model a factory but the real effectiveness of the technique would be evident only when a process is modeled by the reader.

Manufacturing strategies are important for a company's success. However, often there is an inadequate link between manufacturing strategy and its realization. Molina et al think that this is due to the lack of appropriate decision support tools which can assist top management in organizing and communicate crucial strategy. Such tools need both a knowledge of how a strategy can be formulated and the manufacturing position of the firm. The results from two projects at Loughborough University of Technology namely the Startegic Manufacturing Decision Support (SMDS) project and the Model Oriented Simultaneous Engineering (MOSES) project are used in this paper. Manufacturing strategy can be broken down into Business Strategy, Product design strategy, Financial Strategy and Manufacturing Strategy. An effective manufacturing strategy consists of interactions between these four areas. In developing an effective manufacturing strategy, we need to consider the present manufacturing of the company. This is where the manufacturing model comes into play.

The SMDS project aims to link business strategy to manufacturing performance. It also aims to supply a tool to top management to organize and communicate their strategies. The Manufacturing model is a four level model consisting of the factory, shop, cell and station levels. In each of these levels, there are Strategic decisions, Operational rules and performance measures. The factory level should represent the information needed for manufacturing strategy. Thus the same set of criteria (Strategic decisions, Operational rules and performance measures) can be used for SMDS. Strategic decisions are decisions made choosing a particular variable over another. Operation rules are the rules that are in use in the various levels and performance measures are the measures of the performance caused by the Strategic decisions and the operating rules.

To design a manufacturing plant, the expected performance of the plant needs to be known. This is not an easy task and simulation needs to be carried out to find the performance. For a huge factory, performing a simulation is not a very efficient way of finding out the performance. These simulation models take up too much memory and they give out way too much output. They are also very complicated and the output cannot be interpreted easily. Hence, a metamodel can be used to simplify the simulation. In a simulation if the output Y = f1 (X1, X2, ... Xn) then the corresponding metamodel could be Y' = f2 (X1, X2, ... Xm). The authors did a study on the use of metamodels in manufacturing. The aim of the study is to show that metamodels are being used more and more in manufacturing. The authors found that there was interest in metamodels in the late 70s and then there were not many papers about metamodels. The interest in metamodels has increased again since 1987. Also the numbers of papers of metamodels in manufacturing systems has increased greatly. Earlier, the papers were more theoretical but now the papers are more case studies. This means that the use of metamodels has increased in manufacturing.