Manufacturing systems configuration complexity

Manufacturing Systems Configuration Complexity
H. A. EIMaraghy(l), 0. Kuzgunkaya, R. J. Urbanic Intelligent Manufacturing Systems (IMS) Centre, Faculty of Engineering University of Windsor, Windsor, Ontario, Canada

Abstract A new Complexity Coding System is introduced to classify and code the machines, buffers and material handling equipment in manufacturing systems. A Code-based StructuralComplexity Index is proposed to capture the amount and variety of information related to these components. The probability of a manufacturing system's success in delivering the desired production capacity, as function of the availability of its components, is used as an additional measure of the system complexity in meeting the targeted forecast production volume with its variation. The applicationof the Coding System and two Complexity Indices in comparing manufacturing system configurations is demonstrated using a cylinder block-machining example with consistent results. Keywords: Manufacturing Systems; Group Technology; Complexity

1 VARIATION OF MANUFACTURING SYSTEMS Manufacturing systems have evolved over time in response to changing market demands (e.g. common products, nicheproducts, mass customization), varying emphasis on objectives and values (e.g. cost, quality, agility) and technological advances in products, processes and systems. This gave rise to various types of manufacturing systems from job shops to mass production, flexible manufacturing and potentially reconfigurable manufacturing systems. As complexity and supply of products increase, manufacturers need todifferentiate themselves by producing goods that satisfy customer requirements in the right quantity, efficiently, cost effectively, and respond quickly in order to maintain and increase their market share. Hence, tools are needed to achieve flexibility and adaptability at product design and manufacturing levels. Uncertainty about satisfying the new demands increases as different products andproduct features are introduced for which the current manufacturing system was not designed. This leads to increased complexity in trying to fulfill the new manufacturing requirements with existing system capabilities by using different and less optimal process plans, machine assignments, routes or schedules. The capabilities of the system may also be significantly augmented or modified byaddinghemoving tools, machines or modules. This means re-setting the system periodically or re-designing / reconfiguring it as needed. This is observed in manufacturing systems expansion, shrinkage or total change (e.g. for significant products change over). Similarly, as demand for products varies, either by exceeding the existing production capacity or falling short of fully utilizing it, the need arisesfor re-setting capacity. Variations in demands lead to uncertainty regarding the ability to fulfill the desired production volume. The resulting complexity is dealt with incrementally by adding / removing production resources (e.g. equipment, material, people, etc.) to existing systems, expanding production time through the use of overtime, second and third shifts as well as outsourcing. Periodicalre-setting may also occur by adding new production lines or even starting whole new production facilities as may be observed in expanding and building

new factories. The same is true in the case of reduction of production volume in response to decreased demand. Complex manufacturing systems that comprise large number of different resources (i.e. equipment, material, people, data, programs,etc.), and are designed to respond dynamically to changing requirements represent an extended space of alternatives and choices. The cost of this added complexity must always be balanced against improved performance. 2 MANUFACTURING SYSTEMS COMPLEXITY Several researchers addressed the manufacturing systems complexity [e.g. 1, 2, and 31. It is generally agreed that the real or perceived complexity of...