812 resultados para Computer integrated manufacturing systems
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Mode of access: Internet.
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There is controversy over whether integrated manufacturing (IM), comprising advanced manufacturing technology, just-in-time inventory control and total quality management, empowers or deskills shop floor work. Moreover, both IM and empowerment are promoted on the assumption that they enhance competitiveness. We examine these issues in a study of 80 manufacturing companies. The extent of use of IM was positively associated with empowerment (i.e., job enrichment and employee skill enhancement), but, with the minor exception of AMT, bore little relationship with subsequent company performance. In contrast, the extent of empowerment within companies predicted the subsequent level of company performance controlling for prior performance, with the effect on productivity mediating that on profit. Copyright © 2004 John Wiley & Sons, Ltd.
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Editorial
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Results of complementary surveys of foreign and Chinese manufacturing enterprises with respect to their objectives and expectations regarding technology transfer into China show that the major strategic objective of foreign enterprises, to gain access to the Chinese market, fits well with Chinese enterprises’ main objective of improving domestic competitiveness but less well with that of accessing world markets through technology transfer. Foreign firms rate highly the capability of Chinese enterprises to learn new technologies and also find the Chinese macro environment for business favourable. The survey results provide information that will help managers with their negotiations on co-operating with prospective partners for the transfer of technology as well as assisting policy makers who wish to facilitate more effective transfer arrangements.
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The Systems Engineering Group (SEG) at De Montfort University are developing the Boardman Soft Systems Methodology (BSSM) which allows complex human systems to be modelled, this work builds upon Checkland's Soft Systems Methodology (1981). The BSSM has been applied to the modelling of the systems engineering process as used in design and manufacturing companies. The BSSM is used to solicit information from a company and this data is then transformed into systemic diagrams (systemigrams). These systemigrams are posited to be accurate and concise representations of the system which has been modelled. This paper describes the collaboration between SEG and a manufacturing company (MC) in Leicester, England. The purpose of this collaboration was twofold. First, it was to create an objective view of the MC's processes, in the form of systemigrams. It was important to get this modelled by a source outside of the company, as it is difficult for people within a system being modelled to be unbiased. Secondly, it allowed a series of systemigrams to be produced which can then be subjected to simulation, for the purpose of aiding risk management decisions and to reduce the project cycle time
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Cellular manufacturing is widely acknowledged as one of the key approaches to achieving world-class performance in batch manufacturing operations. The design of cellular manufacturing systems (CMS) is therefore crucial in determining a company's competitiveness. This thesis postulated that, in order to be effective the design of CMS should not only be systematic but also systemic. A systemic design uses the concepts of the body of work known as the 'systems approach' to ensure that a truly effective CMS is defined. The thesis examined the systems approach and created a systemic framework against which existing approaches to the design of CMS were evaluated. The most promising of these, Manufacturing Systems Engineering (MSE), was further investigated using a series of cross-sectional case-studies. Although, in practice, MSE proved to be less than systemic, it appeared to produce significant benefits. This seemed to suggest that CMS design did not need to be systemic to be effective. However, further longitudinal case-studies showed that the benefits claimed were at an operational level not at a business level and also that the performance of the whole system had not been evaluated. The deficiencies identified in the existing approaches to designing CMS were then addressed by the development of a novel CMS design methodology that fully utilised systems concepts. A key aspect of the methodology was the use of the Whole Business Simulator (WBS), a modelling and simulation tool that enabled the evaluation of CMS at operational and business levels. The most contentious aspects of the methodology were tested on a significant and complex case-study. The results of the exercise indicated that the systemic methodology was feasible.
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This thesis reviews the existing manufacturing control techniques and identifies their practical drawbacks when applied in a high variety, low and medium volume environment. It advocates that the significant drawbacks inherent in such systems, could impair their applications under such manufacturing environment. The key weaknesses identified in the system were: capacity insensitive nature of Material Requirements Planning (MRP); the centralised approach to planning and control applied in Manufacturing Resources Planning (MRP IT); the fact that Kanban can only be used in repetitive environments; Optimised Productivity Techniques's (OPT) inability to deal with transient bottlenecks, etc. On the other hand, cellular systems offer advantages in simplifying the control problems of manufacturing and the thesis reviews systems designed for cellular manufacturing including Distributed Manufacturing Resources Planning (DMRP) and Flexible Manufacturing System (FMS) controllers. It advocates that a newly developed cellular manufacturing control methodology, which is fully automatic, capacity sensitive and responsive, has the potential to resolve the core manufacturing control problems discussed above. It's development is envisaged within the framework of a DMRP environment, in which each cell is provided with its own MRP II system and decision making capability. It is a cellular based closed loop control system, which revolves on single level Bill-Of-Materials (BOM) structure and hence provides better linkage between shop level scheduling activities and relevant entries in the MPS. This provides a better prospect of undertaking rapid response to changes in the status of manufacturing resources and incoming enquiries. Moreover, it also permits automatic evaluation of capacity and due date constraints and hence facilitates the automation of MPS within such system. A prototype cellular manufacturing control model, was developed to demonstrate the underlying principles and operational logic of the cellular manufacturing control methodology, based on the above concept. This was shown to offer significant advantages from the prospective of operational planning and control. Results of relevant tests proved that the model is capable of producing reasonable due date and undertake automation of MPS. The overall performance of the model proved satisfactory and acceptable.
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The performance of direct workers has a significant impact on the competitiveness of many manufacturing systems. Unfortunately, system designers are ill equipped to assess this impact during the design process. An opportunity exists to assist designers by expanding the capabilities of popular simulation modelling tools, and using them as a vehicle to better consider human factors during the process of system design manufacture. To support this requirement, this paper reports on an extensive review of literature that develops a theoretical framework, which summarizes the principal factors and relationships that such a modelling tool should incorporate.