Aplicação do algoritmo genetico na formação de celula de manufatura

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro TecnologicoNeste trabalho estuda-se o problema de formação de células de fabricação. A formação de família de peças e grupos de máquinas é um problema que vem desafiando, nos últimos tempos, a argúcia dos pesquisadores. Este trabalho propõe um modelo matemático, com um procedimento de solução baseado no algoritmo genético abordando a questão do custo e tempo de processamento das peças. A criação de problemas para teste mostraram que o algoritmo tem solução e que ele é uma ferramenta valiosa para trabalhar no ambiente de fabricação

Dynamic process simulation for the design of complex large-scale systems with respect to the performance of multiple interdependent production processes

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999.Includes bibliographical references (p. 247-255).This research developed a methodology to assess the design of complex large-scale products with respect to the performance of their production processes. In complex large-scale projects, physical and functional relationships among the product systems and components, along with concurrency and co-location of their production processes, generate inter-system process dependencies that drive the relative production rates among the systems. The methodology links the complexity of the product to the complexity of the production process at the level of detail of the single component and task to model the impacts of inter-system process dependencies on production performance. This detailed focus makes the methodology highly responsive to changes in design and technology and able to capture primary, secondary and tertiary impacts of change on production performance. Based on the methodology, a dynamic process simulation model has been developed to systematically assess different combinations of design and technology alternatives across multiple dimensions of production performance. Performance measures include project duration, costs, resource utilization and index of workers' exposure to dangerous conditions. Simulated scenario testing based on actual data from a construction project, the renovation of Baker House (MIT building W7), demonstrates that 1) inter-system process dependencies strongly influence production performance, 2) these links build their dynamic effects on production performance at the detailed task and component level, and 3) the nature of the links and their spatial and temporal location vary as changes are introduced in the design and in the production specifications. One important consequence is that the specification and optimization of the production processes for product systems and components as separate from one another leads to solutions that may be sub-optimal for the performance of the whole project. In addition, the specification and the representation of complex production processes at the aggregate level fails to capture important impacts of design and technology changes and, thus, leads to inconsistent duration and cost estimates.by Alessandra Orsoni.Sc.D

The development of a metallurgical CAPP system for large steel forgings.

The development of CAPP (Computer Aided Process Planning) systems promises improvement to the design efficiency and quality of process plans, whilst maintaining knowledge for future developments. Although considerable progress has been made in Computer Aided Process Planning, most of the systems developed or under development so far are limited to one manufacturing operation and to planning for an individual part design. The systems lack an overall structure for real manufacturing practice. This thesis examines the problems involved in the planning of an extensive manufacturing task involving many different processes including chemical and thermal treatments. On the basis of the evaluation of the manufacturing system in the collaborating company, an intelligent database system has been designed to solve metallurgical process planning problems involved in the manufacture of large steel forgings. In this CAPP database system, two hierarchy control levels involving a number of local planning areas have been adopted to allow the development of process sub-plans as well as supporting engineering data. All the process sub-plans have been integrated into a single system rather than isolated as separate entities within the overall metallurgical process planning system together with quality assurance control and other functions. These sub-plans, however, are planned and modified in the separate planning areas, the development being conducted on facsimile data records. Only when each sub-plan has reached a satisfactory state of development is it issued - made available to the overall system - by transferring the facsimile records into the system data files, the facsimile records then being discarded.Metallurgical process knowledge and rules have been incorporated into the database. These allow the system to assist users to make decisions and achieve final desired process plans. A versional approach has been developed to organise and control the stage by stage evolution of issued process plans within this complex steel forging environment. The use of separate planning areas and local facsimile records allows the modification of sub-plans already issued to be undertaken on a step by step but secure basis. A fully operating authorisation system controlling access to the data and the deletion or modification of records has been achieved. This is essential in a CAPP system of this type in which historical decisions, or approved rules based on historical experience, are presented to the users as the basis to make new decisions.The work has been extended to explore external enhancement of the central database system with an expert system and with specially written C ++ programmes. The system architecture needed to support this link is described, and issues raised by the enhancement that relate to the overall control are then addressed. The final part of the thesis examines the limitations of the method that has been developed and discusses difficulties involved in implementing a CAPP system in a large concern involved in the 'bespoke' manufacture of complex engineering artifacts on a one-off design basis