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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Enhancing the form creation capabilities of digital industrial design tools

Sener, Bahar January 2004 (has links)
The foundation of the research is that conventional computer-aided design (CAD) has yet to provide form creation tools that are entirely satisfactory to industrial designers, and that improved tools will redress the present shortfalls. Three interconnected strands of research are reported in the thesis. Emphasis is placed throughout on learning from current practices, in order to identify how digital design tools can be improved to provide better support to industrial designers' form creation processes. The first research strand comprises a series of design and modelling experiments, leading to a definitive set of customer needs for form creation. Documentary evidence is collected and analysed on the modelling activities associated with blue foam, conventional CAD, and the FreeForm® virtual clay haptic modelling system. Strengths and weaknesses of each modelling medium are identified and discussed. Taxonomies of modelling tools and charts of generalised sequences of form creation are constructed. The second research strand comprises a case study with Procter & Gamble, which establishes recommendations for how FreeForm®, as a virtual material modelling system, can be most effectively integrated into commercial new product development. The third research strand comprises a concept design project, which delivers eleven proposals for enhancing the form creation capabilities of digital industrial design tools. The main conclusions reveal that conventional CAD fails to provide satisfactory sketch form creation with both two-dimensional and three-dimensional representations. Furthermore, sketch form creation, which is characteristically speedy, loose and explorative, must be allied to constrained and dimension-driven form creation if digital design tools are to satisfy industrial designers' needs. The alliance of these two contrasting form creation approaches is suggested to be especially challenging. Two distinct directions for digital design tools are identified by the research: (i) improved emulation, or implementation, of the manual activities involved with non-digital media; and (ii) new paradigms away from 'real world' emulation, which supplement designers' cognitive modelling and draw upon existent design and communication skills.
42

Product and manufacturing process improvement using data mining

Shahbaz, Muhammad January 2005 (has links)
In recent years manufacturing enterprises are increasingly automated and collect and store large quantities of data relating to their products and production systems. This electronically stored data can hold both process measures and hidden information, which can be very important when discovered. Knowledge discovery in databases provides the tools to explore historic or current data to reveal many kinds of previously unknown knowledge from these databases. Manufacturing enterprises data is complex and may include information relating to design, process improvement and limitations, manufacturing machines and tools, and product quality. This thesis focuses on issues relating to information extraction from engineering databases in general and from manufacturing processes in particular using their historical databases. It also addresses the important issue of how the process or the design of the product can be improved based on such information.
43

Simulation optimisation : an expert mechanism approach

Mebrahtu, Habtom January 2006 (has links)
No description available.
44

A methodology for the concurrent design of products and their assembly sequence

Barnes, C. J. January 1999 (has links)
This thesis reports on the development of a two-tier methodology that provides support for assembly sequence construction, validation and evaluation in parallel with the design. This facilitates the production of products that are optimised for assemblability. The proposed approach diverges significantly from many of the sequence generation methods developed to date, which assume that assembly planning starts at the conclusion of the design process. It is believed that the latter approach misses an important opportunity to concurrently implement design and sequence improvements that would result in products inherently suited to assembly. The industrial assembly planning process was found to be completely different from the automatic sequence generation approach. The Two-Tier methodology has its foundations in this manual process, which uses a breadth-first, depth-second search. A constraint-based method is used to interactively validate the sequence. In direct contrast to traditional sequence generators, the hard and soft constraints are invoked throughout the process. A novel approach to sequence evaluation allows the user to quantitatively determine the suitability of the sequence at any time during the construction process. However, designers are rarely assembly experts and it is unreasonable to expect practical sequences to be generated without assistance. Thus, a set of generic assembly planning rules was identified from industrial surveys by the author. These were collaboratively implemented into an Expert Assembler, which currently consists of two mini advisors. Support is available to identify the most suitable base component and the most appropriate component to add next. The Two-Tier methodology has been implemented into a computer-based system called SPADE (Sequence Planning And Design Environment). A four-layer model holds the product data that underpins this implementation. The methodology and SPADE have been successfully tested using representative case studies and the results are reported as part of this thesis.
45

Automated off-line programming for Rapid Prototyping using Gas Metal Arc Welding

Ribeiro, A. F. M. January 1995 (has links)
Rapid Prototyping is a recent CAD/CAM based manufacturing technique which produces prototypes of components in a fraction of the time normally required. This technique normally involves drawing the part as a 3 Dimensional solid model using a CAD program and then 'printing' it in 3 Dimensions. The raw material can be a photopolymer or thermoplastic which solidifies when in contact with light. Other materials are available although producing the final parts a 100% metal is not very usual. Some disadvantages of these techniques are: a) 100% metal prototypes cannot normally be made directly. b) only prototypes can be produced instead of the final component. c) machine size limits the size of the final component. d) very thin layers are deposited. This makes the build up more time consuming and mostly suitable to small components. The main objective of this work was to overcome these disadvantages by creating a new Rapid Prototyping technique using Robot Fusion Welding. In the pre-production phase, it is important to make a prototype not only for visualisation but also to test and assess it in its real function. Therefore, prototyping in resin a component which is going to be made in metal has no use for assessing purposes. This technique, besides making the prototype in metal can also be used as a production technique to make the real usable final component. It even allows the use of different metals along its structure in the welding filler wire is changed. This makes it possible to have different structural characteristics in the same component a required. None of the slicing algorithms developed for other Rapid Prototyping processes were applicable to this new technique and therefore a new slicing concept (and routine) was created specifically. I addition, an interface for off-line programming and quality documentation was evolved. The technique developed has been tested by fabricating several 'test' components and both the dimensional accuracy and component integrity have been evaluated and proved to be successful.
46

The development of an educational computer aided design system for garment manufacture

Jo, Jin-Sook January 1989 (has links)
A computer aided design (CAD) system for the design of flat patterns for female clothing has been developed specifically for use in an Educational environment. This Pattern Making System (PMS) has been developed using a commercial computer aided design software system, CADDS 4X, originally marketed for Mechanical Engineering applications by the Computervision division of Prime Plc. The software operates on a Sun 3 computer Workstation under a Unix operating system environment. The features of the PMS include software programs, written using CVMAC, the macroprogramming language of the host CAD system, for the creation of basic blocks for many styles of garments to suit any size of female body within a specified size chart or user defined anthropometric data. Also included are software programs for the design of auxiliary patterns such as collars, cuffs etc., together with programs to proportionally grade patterns to different sizes. These programs have been compiled with appropriate CADDS 4X graphics functions and structured into an icon menu driven shell to form the PMS. The main emphasis in developing the PMS was to make it suitable for an Educational environment. Therefore an extensive set of demonstration programs and on-line help ivfiles has been written and incorporated into the PMS to assist the user. These help files explain the details of the PMS and the CADDS environment, the functions of the programs and the graphics commands and give guidance in their use for the novice user. Furthermore, a series of explicit tutorials have been written so that inexperienced users can self-teach themselves in the use of the PMS for pattern design so that the PMS also forms a system for computer based learning. The intention and hope is that, through the use of this tutorial based PMS, students will gain considerable insight into the use of a CAD system for pattern design which they can readily transfer to other commercial systems.
47

Manufacturing systems simulation using the principles of system dynamics

Oyarbide Zubillaga, Aitor January 2003 (has links)
Manufacturing is the largest single contributor to the global economy. The evolution of consumer demands has pressurised companies into producing a larger variety of products, with improved specifications, reduced costs, and shorter lead times. In this context, companies have found simulation techniques useful in their manufacturing systems design processes; simulation based on Discrete Event Simulation (DES) is the preferred technique. The complexity of manufacturing systems, and the mechanisms of DES, means that the simulation task often consumes excessive time and resources, such as data, software, and training. Evidence suggests that an alternative modelling technique, named System Dynamics (SD), is also appropriate for conducting this task. SD has been applied successfully in other fields, where its graphical notation is considered beneficial. However, the lack of an SD tool that is tailored toward manufacturing systems has prevented industry from adopting this technique more extensively. This thesis determines the extent to which SD can provide a credible alternative to DES in the manufacturing system design process. Information concerning DES, SD and practitioners' needs was gathered from published literature and from an interview survey. A functional prototype of a tool based on the SD principles, but tailored to model manufacturing systems was then developed. Three case studies then provided valuable information concerning the requirements of industry and the capabilities of the SD technique. This research programme has found SD to be sufficiently accurate and quicker than DES tools under certain conditions, requiring less data and skills. In addition, the user interface appears to have had a significant impact on the lack of adoption of SD techniques within the manufacturing sector. Simp1ifications made by this technique can reduce both model building and model execution time, and thus, experimentation time. However, evidence suggests that DES is still more prevalent, and that further work is required to develop SD based tools tailored to manufacturing systems. Therefore, this thesis provides a much improved understanding of the capabilities of SD as an aid to manufacturing systems design.
48

Automatically idealising quasi-axisymmetric component models to 2D axisymmetric finite element models

Camacho Casero, Jorge January 2017 (has links)
At present, simulation is at the core of the product development cycle. To accelerate the design and simulation phases, it is necessary to idealise the CAD model prior to simulation activities. The strategy for model idealisation to be used depends on the original geometry and the type of analysis to be run. In industry, many components are either axisymmetric or quasi-axisymmetric, (i.e. largely axisymmetric with some non-axisymmetric features). Using 3D models for analising these components is computationally expensive and is often unpractical, especially at early stages of the design process when the design is constantly changing. For this reason, there is an ambition to use 2D-axisymmetric models to represent these quasi-axisymmetric components, with the section properties altered for the elements in the non-axisymmetric regions„to account for the actual component shape. The current industrial process of creating the 2D equivalent representation of a 3D model is manual, time consuming and requires significant skill. This thesis describes an innovative methodology which automatically creates a 2D-axisymmetric finite element (FE) model of a quasi-axisymmetric component from its 3D CAD model. The process has been implemented using the API to a commercial FE package. It creates the FE models in the order of minutes (< 2.5 minutes) for realistic aerospace gas turbine components. In a series of thermal analyses of an industrial Turbine Rear Structure, the results from the resulting axisymmetric FE model are demonstrated to be within 9% of the 3D FE model.
49

Business process and IT systems implementation

Kaps, Tim Oliver January 2003 (has links)
This research develops, tests and refines an implementation model with the supporting toolkit to implement business process and IT systems within an existing manufacturing environment. The implementation model is based on the vehicle development process and the IT systems development process. A supporting toolkit has been developed by reviewing multiple areas of research and practice such as project management, quality management, systems engineering, behavioural studies, business process reengineering, people and cultural studies, as well as best practices within industry. This model and its corresponding toolkit has then been thoroughly tested and refined based on empirical research and experiences gained within 3 business cases, which took place within the BMW Group between 1996 and 2001. Due to the growth of joint ventures, mergers and acquisitions within the automotive sector the introduction on new business processes and IT systems represents a common problem within the automotive and other industries. Common business processes and IT systems within one automotive group enable the flexible use of manufacturing capacity and skilled workforce. Thus they represent the way to realise the synergy potential that often drives mergers and acquisitions. Within the business cases which are focused in this research, the introduction of new business processes and IT systems in the areas of engineering, sales and marketing, production, finance and process planning was carried out in parallel with the introduction of a new product. The challenges of such programmes are multiplied and the price of failure is tremendous. At the BMW Group the knowledge or model and toolkit of how to manage such a wide-ranging business change was not available when the first business case was initiated. Thus it had to be developed and documented on the run based on the lessons learnt. This research helped to enable and structure this process. Key recommendations for successful implementation are proposed. Critical people and cultural issues when implementing new business processes and IT systems are analysed and strategies for their resolution are proposed. With this research an overarching, holistic model on business process and IT systems implementation and the required toolkit is provided. Both theoretical research and practical experiences within an industrial context are linked due to the unique set-up of this research. This research set-up and the fact that the results were generated within the BMW Group facilitated the acceptance and the diffusion of the recommendations within the BMW Group. Principal parts of this model and its toolkit are now being used at the BMW Group on current business cases. The pre-study duration (Time-to-decision) and the duration of the implementation were halved. Future programmes will benefit from the results of this research.
50

A framework for digitisation of manual manufacturing task knowledge using gaming interface technology

Prabhu, Vinayak Ashok January 2015 (has links)
Intense market competition and the global skill supply crunch are hurting the manufacturing industry, which is heavily dependent on skilled labour. Companies must look for innovative ways to acquire manufacturing skills from their experts and transfer them to novices and eventually to machines to remain competitive. There is a lack of systematic processes in the manufacturing industry and research for cost-effective capture and transfer of human skills. Therefore, the aim of this research is to develop a framework for digitisation of manual manufacturing task knowledge, a major constituent of which is human skill. The proposed digitisation framework is based on the theory of human-workpiece interactions that is developed in this research. The unique aspect of the framework is the use of consumer-grade gaming interface technology to capture and record manual manufacturing tasks in digital form to enable the extraction, decoding and transfer of manufacturing knowledge constituents that are associated with the task. The framework is implemented, tested and refined using 5 case studies, including 1 toy assembly task, 2 real-life-like assembly tasks, 1 simulated assembly task and 1 real-life composite layup task. It is successfully validated based on the outcomes of the case studies and a benchmarking exercise that was conducted to evaluate its performance. This research contributes to knowledge in five main areas, namely, (1) the theory of human-workpiece interactions to decipher human behaviour in manual manufacturing tasks, (2) a cohesive and holistic framework to digitise manual manufacturing task knowledge, especially tacit knowledge such as human action and reaction skills, (3) the use of low-cost gaming interface technology to capture human actions and the effect of those actions on workpieces during a manufacturing task, (4) a new way to use hidden Markov modelling to produce digital skill models to represent human ability to perform complex tasks and (5) extraction and decoding of manufacturing knowledge constituents from the digital skill models.

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