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No description available.

No description available.

No description available.

In this thesis, a new graph grammar representation is proposed to reason about the manufacturability of solid models. The knowledge captured in the graph grammar rules serves as a virtual machinist in its ability to recognize arbitrary geometries and match them to various machine operations. Firstly, a novel convex decomposition algorithm has been developed to decompose a given part into multiple sub-volumes, where each sub-volume is assumed to be machined in one operation or to be non-machinable. Then the decomposed part is converted into a graph so that graph grammar rules can determine the machining details. A candidate plan is a feasible sequence of all of the necessary machining operations needed to manufacture this part. If a given geometry is not machinable, the rules will fail to find a complete manufacturing plan for all of the sub-volumes. As a result of this representation, designers can quickly get insights into how a part can be made and how it can be improved based upon the feedback of the rules. A variety of tests of this algorithm on both simple and complex engineering parts show its effectiveness and efficiency. / text

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.

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No description available.

This research is concerned with improving the planning process in large construction projects where the management and planning of the preconstruction planning process itself is a significant and complex task. Preconstruction planning in the construction sector has become a complex task requiring substantial collaboration, with ad-hoc teams (especially from design and construction) created to bring all the project resources involved together in a timely manner, to ensure a construction project is completed effectively and efficiently. This, combined with the iterative nature of the planning process, has challenged even the best companies in the industry. Three major weaknesses in current practice were identified in the research: first, the planning preconstruction planning process is heavily reliant on a planner's experience (i.e. a planner develops a new programme of a preconstruction planning through personal determination of the planning tasks and their precedence, starting afresh at the beginning of each project). For large projects this is not only time consuming but subject to the limitations ohhe planner's knowledge and experience, often resulting in simplistic programmes in which many of the dependencies are ignored. Secondly, guesses (i.e. estimates) are frequently made in the planning process, which neither the initial planner nor the downstream planner will later check. They are usually ignored and left until the execution of the plan, when the problems reveal themselves. Finally, the current techniques for the management of preconstruction planning, such as the critical path method and bar charts, cannot account for the iterative nature of the planning process that requires estimations to be made and work to be redone until a satisfactory so lution is developed. As a result, it may be said that preconstruction planning is currently managed poorly. It can be. argued that if preconstruction planning is to be undertaken effectively, it must be better managed and planned.

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