In this research, a set of novel, integrated and systematic adaptive process planning algorithms and strategies, which include adaptive tool-path generation algorithms and strategies, adaptive slicing algorithms and strategies, adaptive approach for FGM(Functionally Graded Material)-based biomedical model and build time and geometrical accuracy analysis and control modules, for complex biomedical model fabrication in the RP/M (Rapid Prototyping and Manufacturing) process, have been developed to balance and optimise the geometrical accuracy and build efficiency. In the developed adaptive tool-path generation algorithms and strategies, directly slicing algorithm and NURBS(Non-Uniform Rational B-Spline)-based curves have been developed to represent the boundary contours of the sliced layers to maintain the geometrical accuracy of original biomedical models. The developed mixed tool-path generation algorithm can be used to generate mixed contour and zigzag tool-paths to preserve geometrical accuracy and speed up fabrication. Based on the developed build time and geometrical accuracy analysis modules, the developed adaptive speed algorithms can be used to further reduce build time of biomedical model fabrication in RP/M. In the developed adaptive slicing approach, rotating slicing and two thresholds have been introduced to extract surface feature of biomedical models. Then, an adaptive slicing thickness determination algorithm has been developed to decide the thickness of each slicing layer based on the outside surface complexity of the model. In addition, the user can balance the geometrical accuracy and the build efficiency during RP/M processing with the different values of two pre-setting thresholds. Furthermore, by choosing the right value of the pre-setting thresholds, it can also effectively reduce the build time and improve the accuracy of biomedical model fabrication in RP/M. In the developed adaptive approach for FGM-based biomedical model fabrication, FGM-based modelling features can represents typical FGM-based biomedical models effectively, and the linear and non-linear control parameters for FGM composition and distributions can enable users to address their specific functional needs of FGM-based biomedical model. The proposed mixed tool-path generation algorithm and adaptive speed algorithm can be used to generate a series of contour/offset tool-paths to represent the material gradual change, and zigzag tool-path is generated for the internal area of a single material to support the realizable and customized FGM-based biomedical models fabrication in RP/M efficiently.

A novel approach to microfabrication based on stereolithography was presented. This fabrication process is referred to as, ‘Exposure Controlled Projection Lithography’ (ECPL). In the ECPL process, incident radiation, patterned by a dynamic mask, passes through a transparent substrate to cure photopolymer resin. By controlling the amount of exposure, the height field of the cured film can be controlled. An ECPL system was designed and assembled. Factors affecting the accuracy of the ECPL process in fabricating micron shaped features were identified and studied. A real-time in-situ photopolymerization monitoring system was designed and assembled within the ECPL system to identify the sources of variations present in the system. Parts are fabricated from the ECPL process because of polymerization (or cross-linking) of monomer resin using light energy. Photopolymerization is a complex process involving coupling between several phenomena. This process was modeled by utilizing an understanding of the known polymerization reaction kinetics with incorporating the effects of oxygen inhibition and diffusion. A material response model and a simulation tool to estimate the shape of a cured part resulting from photopolymerization was created. This model was used to formulate a process-planning method to estimate the manufacturing process inputs required to cure a part of desired shape and dimensions. The process planning method was validated through simulations and experiments.

Process planning is a task comprising a broad range of activities to design and develop an appropriate manufacturing process for producing a part. Interpretation of the part design, selection of manufacturing processes, definition of operations, operation sequences, machining datums, geometrical dimensions and tolerances are some common activities associated with the task. Process planning is also “the link between product design and manufacturing” with the supplementary commission to support design of competitive products. Process planning is of a complex and dynamic nature, often managed by a skilled person with few, or no, explicit methods to solve the task. The work is heuristic and the result is depending on personal experiences and decisions. Since decades, there have been plenty of attempts to develop systems for computer-aided process planning (CAPP). CAPP is still awaiting its breakthrough and one reason is the gap between the functionality of the CAPP systems and the industrial process planning practice. This thesis has an all-embracing aim of finding methods that cover essential activities for process planning, including abilities to predict the outcome of a proposed manufacturing process. This is realised by gathering supporting methods suitable to manage both qualitative and quantitative characterisation and analyses of a manufacturing process. The production research community has requested systematisation and deeper understanding of industrial process planning. This thesis contributes with a flow chart describing the process planning process (PPP), in consequence of the methodological studies. The flow chart includes process planning activities and information flows between these activities. The research has been performed in an industrial environment for high volume manufacturing of gear parts. Though gear manufacturing has many distinctive features, the methods and results presented in this thesis are generally applicable to precision manufacturing of many kinds of mechanical parts. / <p>QC 20140522</p>

Ces travaux proposent une méthode d’assistance à la sélection des techniques d’assemblage et à l’allocation de tolérances sur les écarts géométriques des composants dans le cadre de l’assemblage de structures aéronautiques composites. Cette méthode consiste à formuler et à résoudre un problème d’optimisation multiobjectif afin de minimiser un indicateur de cout et un indicateur de non-conformité des structures assemblées. L’indicateur de coût proposé prend en compte le coût associé à l’allocation des tolérances géométriques ainsi que le coût associé aux opérations d’assemblage. Les indicateurs de non-conformités proposés sont évalués à partir des probabilités de non-respect des exigences géométriques sur les structures assemblées. Ces probabilités sont évaluées en propageant les tolérances géométriques allouées et les dispersions des techniques sélectionnées au travers d’une fonction appelée Relation de Comportement de l’assemblage (RdCa). Dans le cas de l’assemblage de structures aéronautiques composites, des exigences peuvent porter sur les jeux aux interfaces entre composants. Dans ce cas, la RdCa est évaluée par la résolution d’un problème mécanique quasi-statique non-linéaire par la méthode des éléments finis. Un méta-modèle de la RdCa est construit afin de la rendre compatible avec les méthodes probabilistes utilisées pour évaluer la non-conformité. Finalement, la définition d’un modèle structuro-fonctionnel du produit et d’une bibliothèque de techniques d’assemblage permet de construire un avant-projet de gamme d’assemblage paramétrique. Ce paramétrage permet de formuler le problème d’optimisation multiobjectif résolu à l’aide d’un algorithme génétique. / The purpose of this PhD is to develop a method to assist assembly technique selection and component geometrical tolerance allocation in the context of composite aeronautical structure assembly. The proposed method consists in formulating and solving a multiobjective optimisation problem aiming at minimising a cost indicator and a non-conformity indicator. The cost indicator account for both the cost involved by the geometrical tolerance allocation and the cost associated with the assembly operations. The proposed non-conformity indicators are evaluated according to the probabilities of non-satisfied requirements on the assembled structures. These probabilities are computed thanks to Geometrical Variation Propagation Relation (GVPR) that expresses the characteristics of the product as a function of the geometrical deviation of the components and the dispersion occurring during the assembly. In the case of composite aeronautical structures, the product characteristics can be gaps at interfaces between components. In this case, the GVPR is evaluated by solving a non-linear quasi-static mechanical problem by the mean of the finite element method. A metamodel of the GVPR is built in order to reduce the computing time and to make it compatible with the probabilistic methods used to evaluate the non-conformity. Finally, the use of a structure-functional model of the product together with an assembly technique library allows defining a parametric assembly process plan. The multiobjective optimisation problem built thanks to set of parameters defining the assembly process plan is solved using a genetic algorithm.

A importância deste trabalho encontra suas fundamentações na atual relevância de pesquisas sobre avaliação de impacto de sistemas de informação e na importância dos sistemas CAPP para a indústria de manufatura. A necessidade de avaliar sistemas de informação surgiu de um fenômeno conhecido como paradoxo da produtividade (falta de evidência de retornos para altíssimos investimentos). Já o CAPP é um sistema fundamental na interface de Engenharias e Produções, sendo gerador de informações para toda a empresa. Para a obtenção este objetivo foram realizadas análises de dados colhidos em 11 casos investigados. / The importance of this work meets its foundation both in the nowadays relevance of studies on information systems impact and in the importance of CAPP systems to the manufacturing industry. The necessity of evaluating information systems emerged from a situation known as the productivity paradox (lack of return evidence in despite high investments). Regarding the CAPP, it is a fundamental system to do the interface between the Project and the Production areas, being also a generator of important information to the whole company. To reach these goals, some analysis were carried on data collected from 11 case studies.

This paper presents an intelligent, hybrid system for stamping process planning in progressive die design. The system combines the flexibility of blackboard architecture with case-based reasoning. The hybrid system has the advantage that it can use past knowledge and experience for case-based reasoning when it exists, and other reasoning approaches when it doesn’t exist. A prototype system has been implemented in CLIPS and interfaced with Solid Edge CAD system. An example is included to demonstrate the approach. / Singapore-MIT Alliance (SMA)

Finish machining of hardened steel is receiving increasing attention as an alternative to the grinding process, because it offers comparable part finish, lower production cost, shorter cycle time, fewer process steps, higher flexibility and the elimination of environmentally hazardous cutting fluids. In order to demonstrate its economic viability, it is of particular importance to enable critical hard turning processes to run in optimal conditions based on specified objectives and practical constraints. In this dissertation, a scientific and systematic methodology to design the optimal tool geometry and cutting conditions is developed. First, a systematic evolutionary algorithm is elaborated as its optimization block in the areas of: problem representation; selection scheme; genetic operators for integer, discrete and continuous design variables; constraint handling and population initialization. Secondly, models to predict process thermal, forces/stresses, tool wear and surface integrity are addressed. And then hard turning process planning and optimization are implemented and experimentally validated. Finally, an intelligent advisory system for hard turning technology by integrating experimental, numerical and analytical knowledge into one system with user friendly interface is presented. The work of this dissertation improves the state of the art in making tooling solution and process planning decisions for hard turning processes.

Mask Projection Stereolithography (MPSLA) is a high resolution manufacturing process that builds parts layer by layer in a photopolymer. In this research, a process planning method to fabricate MPSLA parts with constraints on dimensions, surface finish and build time is formulated. As a part of this dissertation, a MPSLA system is designed and assembled. The irradiance incident on the resin surface when a given bitmap is imaged onto it is modeled as the Irradiance model . This model is used to formulate the Bitmap generation method which generates the bitmap to be imaged onto the resin in order to cure the required layer. Print-through errors occur in multi-layered builds because of radiation penetrating beyond the intended thickness of a layer, causing unwanted curing. In this research, the print through errors are modeled in terms of the process parameters used to build a multi layered part. To this effect, the Transient layer cure model is formulated, that models the curing of a layer as a transient phenomenon, in which, the rate of radiation attenuation changes continuously during exposure. In addition, the effect of diffusion of radicals and oxygen on the cure depth when discrete exposure doses, as opposed to a single continuous exposure dose, are used to cure layers is quantified. The print through model is used to formulate a process planning method to cure multi-layered parts with accurate vertical dimensions. This method is demonstrated by building a test part on the MPSLA system realized as a part of this research. A method to improve the surface finish of down facing surfaces by modulating the exposure supplied at the edges of layers cured is formulated and demonstrated on a test part. The models formulated and validated in this dissertation are used to formulate a process planning method to build MPSLA parts with constraints on dimensions, surface finish and build time. The process planning method is demonstrated by means of a case study.

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