Nos processos usuais de prototipagem rapida, a transformacao do material para a construcao do prototipo, de maneira geral, e realizada por fusao ou polimerizacao oriunda do aquecimento via laser ou resistencia eletrica. Isso, necessariamente, envolve equipamento especial para o processo de fusao e deposicao do material para a construcao das superficies camada por camada, o controle de temperatura para assegurar a qualidade e o tratamento de gases exalados pela transformacao entre outros. Essa forma de transformacao nos processos de prototipagem rapida tem assim custos relativamente altos do prototipo e do equipamento. Uma alternativa para o processo de transformacao inclui evidentemente outros materiais para construcao do prototipo. Entretanto, no levantamento bibliografico realizado observou-se que nao existem trabalhos que explorem materiais e processos alternativos. Assim varios materiais foram analisados com base nas seguintes propriedades: processamento sob temperatura ambiente, capacidade de aderencia entre as camadas, tempo de consistencia e de cura do material, custo e disponibilidade no mercado nacional. Com base nesse estudo foi selecionado o seguinte material: composito a base de complexo de carboidrato, o qual transforma-se, de estado fisico, sob temperatura ambiente. Inicialmente analisaram-se os aspectos de aderencia e tempo de cura. Posteriormente estudaram-se as caracteristicas dos dispositivos e dos processos Fused Layer Modeling (FLM). Baseado nesse estudo foi fabricado um dispositivo para se extrudar material em forma de filamentos. Em seguida modelou-se o cinematismo da velocidade de deposicao do dispositivo extrusor e assim delinear o projeto de experimentos para se obter, do processo proposto, os aspectos qualitativo (operacao, preparacao, custos, utilizacao dos prototipos, entre outros) e quantitativo (velocidade de deslocamento dos eixos X e Y, alturas entre camadas, rugosidade e forma geometrica). Desse estudo resulta que a proposta demonstra potencial para aplicacao na fabricacao de mostruarios, pecas de brinquedos, utilizacao em cursos de formacao profissional, prototipos para moldagem a temperatura ambiente, moldes para fundicao em areia. / In usual processes of rapid prototyping the transformation of the material into the prototype construction is usually made by fusion or polymerization by means of heating by laser or electrical resistance. It necessarily requires special equipment for the fusion process and deposition of material for the surface construction, layer on top of layer, the temperature control to certify quality, the treatment of exhalation during the transformation process, among others. This kind of transformation in the rapid prototyping process is relatively expensive compared with the conventional process of prototyping. An alternative for the transformation process includes, obviously, other kinds of material for the prototype construction. However, bibliographic research has show, that there are no such works which explore alternative materials and processes especially in the national context. Therefore, several kinds of material have been analyzed based on the following properties: required temperature for the work, adherence capacity between the layers, consistence time or cure time of the prototype, cost and availability on the national market. The following material was chosen, based on this study: a compound, based on a carbohydrate complex, because it transforms itself from the physical form at room temperature. First of all, adherence aspects and curing time were analyzed,. Then characteristics of the apparatuses and devices of the Fused Layer Modeling process (FLM). Based on these characteristics the project of the extrusion device was developed, to extrude the carbohydrate composite in form of filaments and its kinematics was modeled to determine the depositing speed and design of experiments to obtain, out of the proposed process, the qualitative aspects (operation, preparation, costs, utilization of the prototype, among others) and quantitative (speed of the dislocation of the table at x-y axis, height between the layers, roughness and geometric form, among others). At that rate the developed proposal shows potentiality to be used in production of showcases, toy pieces, utilization in course for professional training, prototypes for molding at room temperature, forms for sand castings.

The purpose for this study is to examine the impact score has on free-form designed games:games without designed goals. The study is aimed towards smaller products and is meant tohelp designers who are looking to implement score into their game with how it could affect theplayer’s relationship to the defined goal, their intrinsic goal, and the purpose of the game. Aprototype game was created that would simulate the free-form design method. The game hadtwo modes: mode A without score and mode B with score added to one of the actions. Resultsfrom observations and semi-structured interviews show that score has a direct impact on theway participants defined both their intrinsic goals and the one set by the game. Participants’perception of the game defined goal shifts as score is added by giving them a clear andunambiguous extrinsic reward.

Nos processos usuais de prototipagem rapida, a transformacao do material para a construcao do prototipo, de maneira geral, e realizada por fusao ou polimerizacao oriunda do aquecimento via laser ou resistencia eletrica. Isso, necessariamente, envolve equipamento especial para o processo de fusao e deposicao do material para a construcao das superficies camada por camada, o controle de temperatura para assegurar a qualidade e o tratamento de gases exalados pela transformacao entre outros. Essa forma de transformacao nos processos de prototipagem rapida tem assim custos relativamente altos do prototipo e do equipamento. Uma alternativa para o processo de transformacao inclui evidentemente outros materiais para construcao do prototipo. Entretanto, no levantamento bibliografico realizado observou-se que nao existem trabalhos que explorem materiais e processos alternativos. Assim varios materiais foram analisados com base nas seguintes propriedades: processamento sob temperatura ambiente, capacidade de aderencia entre as camadas, tempo de consistencia e de cura do material, custo e disponibilidade no mercado nacional. Com base nesse estudo foi selecionado o seguinte material: composito a base de complexo de carboidrato, o qual transforma-se, de estado fisico, sob temperatura ambiente. Inicialmente analisaram-se os aspectos de aderencia e tempo de cura. Posteriormente estudaram-se as caracteristicas dos dispositivos e dos processos Fused Layer Modeling (FLM). Baseado nesse estudo foi fabricado um dispositivo para se extrudar material em forma de filamentos. Em seguida modelou-se o cinematismo da velocidade de deposicao do dispositivo extrusor e assim delinear o projeto de experimentos para se obter, do processo proposto, os aspectos qualitativo (operacao, preparacao, custos, utilizacao dos prototipos, entre outros) e quantitativo (velocidade de deslocamento dos eixos X e Y, alturas entre camadas, rugosidade e forma geometrica). Desse estudo resulta que a proposta demonstra potencial para aplicacao na fabricacao de mostruarios, pecas de brinquedos, utilizacao em cursos de formacao profissional, prototipos para moldagem a temperatura ambiente, moldes para fundicao em areia. / In usual processes of rapid prototyping the transformation of the material into the prototype construction is usually made by fusion or polymerization by means of heating by laser or electrical resistance. It necessarily requires special equipment for the fusion process and deposition of material for the surface construction, layer on top of layer, the temperature control to certify quality, the treatment of exhalation during the transformation process, among others. This kind of transformation in the rapid prototyping process is relatively expensive compared with the conventional process of prototyping. An alternative for the transformation process includes, obviously, other kinds of material for the prototype construction. However, bibliographic research has show, that there are no such works which explore alternative materials and processes especially in the national context. Therefore, several kinds of material have been analyzed based on the following properties: required temperature for the work, adherence capacity between the layers, consistence time or cure time of the prototype, cost and availability on the national market. The following material was chosen, based on this study: a compound, based on a carbohydrate complex, because it transforms itself from the physical form at room temperature. First of all, adherence aspects and curing time were analyzed,. Then characteristics of the apparatuses and devices of the Fused Layer Modeling process (FLM). Based on these characteristics the project of the extrusion device was developed, to extrude the carbohydrate composite in form of filaments and its kinematics was modeled to determine the depositing speed and design of experiments to obtain, out of the proposed process, the qualitative aspects (operation, preparation, costs, utilization of the prototype, among others) and quantitative (speed of the dislocation of the table at x-y axis, height between the layers, roughness and geometric form, among others). At that rate the developed proposal shows potentiality to be used in production of showcases, toy pieces, utilization in course for professional training, prototypes for molding at room temperature, forms for sand castings.

The need for increased product variety and improved aesthetics require the manufacturing enterprise to reduce time to market and to increase use of free-form surfaces in the form of the product. These changes lead to problems in the traditional approach for specification and verification of tolerances especially for a free form surfaces. In the case of freeform surfaces, the desired performance of a product depends on its geometry and is often controlled by intrinsic parameters such as curvature. Design intent therefore requires control on variations in these parameters. Ideally therefore, tolerances have to be applied on these parameters to prescribe allowable variations in the geometry of free-form surfaces. Since only the geometry of the product is controlled in manufacturing, tolerance specification has to ensure that the tolerances specified on the part geometry will ensure that the resulting value of the parameter of interest is within the limits prescribed by the designer. Relationship between allowable range in design parameters and that in geometry is not linear. Tolerance specification therefore becomes a trial and error process requiring considerable expertise and time. This thesis provides designers with a tool to automatically derive the corresponding tolerances to be specified to the manufacturing process to realize the final shape, such that the parameters that are used to control shape of the surface are within the prescribed variations. Automation in acquiring inspection data has brought dramatic changes in procedure for tolerance verification too. Optical scanners and similar non-contact devices provide large amount of points on the surface of the part quite rapidly. The unstructured point data are then processed to determine if the part complies with the given tolerance specifications. For freeform surfaces, current methods of verification uses minimum distance criterion between the nominal surface and unstructured point data. This ignores the correspondence between the points in the two data sets and may result in the rejection of good parts and acceptance of bad parts. There are other unresolved such as the singularity at corners of polyhedral shapes and handling datum. A new approach based on the Medial Axis Transform (MAT) has been proposed. It has been shown that reasoning on the MAT of the nominal model and the measured point set respectively enables the identification of corresponding points in the two sets. Verification of the tolerance allocated is therefore free from the problem mentioned above. MAT exhibits dimensional reduction and hence reduces verification time. It also eliminates surface fitting for detected feature. Results of implementation are provided for tolerance specification and verification using MAT.

Development of computer models and subsequent finite element analysis, are important aspects of modern engineering design. In this process, the geometry creation and finite element analysis software are well developed; however, the process of discretizing a geometry into a proper finite element model is time consuming and tedious. The work presented here uses the free-form deformation method to create smooth solid models, and invokes a solid subdivision and transition method to generate the hexahedron finite elements. The combination of these two techniques provides an automatic mesh generator that is easy to use, creates acceptable hexahedron elements for finite element analysis, and can model basically any complex shape.

No description available.

Today's commercial rapid prototyping systems (i.e., solid freeform fabrication, layered manufacturing) rely on human intervention to load and unload build jobs. Hence, jobs are processed subject to both the machine's and the operator's schedules. In particular, first-in-first-out (FIFO) queuing of such systems will result in machine idle time whenever a build job has been completed and an operator is not available to unload that build job and start up the next one. These machine idle times can significantly affect the system throughput, and, hence, the effective cost rate. This thesis addresses this problem by rearranging the job queue to minimizing the machine idle time, subject to the machine's and operator's schedules. This is achieved by employing a general branch-and-bound search method, that, for efficiency, reduces the search space by identifying contiguous sequences and avoiding reshuffling of those sequences during the branching procedure. The effectiveness of this job scheduling optimization has been demonstrated using a sequence of 30 jobs extracted from the usage log for the FDM 1600 rapid prototyping system in the Department of Mechanical Engineering at Virginia Tech. / Master of Science

The objectives of Sensor Based Fixture Design and Verification (SFDV) research are to provide the means for detecting contact failure of the workpiece with fixture locators and for preventing incorrect loading of the workpiece in a fixture. The fixtures that involve complex free-form surfaces especially in the aerospace industries face problems caused by the contact failure of the workpiece with locators. In batch and mass production defects often occur due to incorrect loading of the workpiece in a fixture by an operator due to fatigue or inadvertence. The current fixturing research is focussed on improving the fixture quality and other aspects and do not address these issues. This research is focussed on three areas, to generate algorithms for automatically foolproofing the fixtures, to build locators with embedded sensors that could be used to verify the contact and foolproof the existing fixtures, and to design and experimentally validate fixtures for free-form surfaces with sensors to verify the location. In foolproofing, workpieces were classified into different categories to identify the existence of a solution and the geometry was simplified and used to search for a solution based on symmetry/asymmetry to discover a foolproofing location. The algorithms were implemented in a CAD software and the solutions were verified in 3D space. The locators with inbuilt sensors were designed for foolproofing and location verification purposes and the sensors were used in case studies to establish credibility. A sensor based fixture design method is created for the part location of free-form surfaces using fiber optic sensors. An experimental fixture with sensors incorporated in the locators was used to determine the effects of surface curvature on the sensitivity of the sensors. A new theory on best locations for the sensor based locators by utilizing surface curvature is proposed based on the experimental results. The SFDV implementation may help realize the dream for any manufacturing sys­tem aspiring to move beyond the six sigma levels of quality and achieve zero defects.

<p>This thesis presents an approach to free-form surface manipulations, which conceptually improves an existing CAD system that constructs surfaces by smoothly interpolating a network of intersecting curves. There are no regularity requirements on the network, which already yields superior modelling capabilities compared to systems that are based on industry-standard NURBS surfaces.</p><p>Originally, the shape of such a surface can be modified only locally by manipulating a curve in the network. In this process there is an inherent danger that the curve is being pulled away from intersections that it has with other curves. When this happens, the network is invalidated as a surface representation, and many curves may have to be adjusted to restore network consistency and surface quality. This thesis contributes a method that solves these problems by propagating changes that are made in one curve to curves in its vicinity. How and to what extent curves react to changes is controlled by two parameters that can be varied along the curve that is being manipulated. Any curve may be constrained in one or more degrees of freedom. The integrity of the curve network is implicitly conserved, as well as the geometric continuity of the surface.</p><p>The result is a tool for the modification of curve-interpolating surfaces, which can easily be applied to large areas on models with any level of detail. This allows designers to concentrate on the creative process, rather than on planning chains of actions. They can explore different design variations, optimise shapes further, and generally be more productive.</p> / <p>Dette doktorgradsarbeidet presenterer en fremgangsmåte for formgivning og modifisering av datamaskinbaserte, skulpturerte flater. Metoden forbedrer et eksisterende system for data-assistert konstruksjon (DAK) som bygger dobbeltkrummede flater ved å interpolere et nettverk av skjærende kurver. Nettverket trenger ikke være regelmessig, noe som allerede gir bedre modelleringsmuligheter sammenliknet med systemer som er basert på standard NURBS flater.</p><p>En slik flate kan opprinnelig bare endres lokalt ved å dra i en kurve. I denne prosessen er det fare for at kurven blir dratt fra skjæringspunkter den har med andre kurver. Hvis dette skjer, representerer ikke nettverket en flate lenger, og mange kurver må justeres for å få tilbake integriteten i nettverket og kvaliteten i formen. Denne avhandlingen bidrar med en metode som løser disse problemene ved å spre endringer som blir gjort i en kurve til andre kurver i nærheten. Hvordan og i hvilken utstrekning kurvene reagerer på endringen styres av to parametre som kan varieres langs kurven som blir endret. Enhver kurve kan låses i en eller flere frihetsgrader. Integriteten til nettverket samt glattheten i formen blir bevart automatisk.</p><p>Resultatet er et redskap for modifikasjon av kurve-interpolerende flater som med letthet kan brukes på større områder av modeller med hvilken som helst grad av detalj. Dette gir designere muligheten til å konsentrere seg om det kreative, istedenfor å planlegge handlingsrekker. De kan utforske forskjellige designvariasjoner, optimalisere former ytterligere, og i det hele tatt være mer produktive.</p>

This thesis presents an approach to free-form surface manipulations, which conceptually improves an existing CAD system that constructs surfaces by smoothly interpolating a network of intersecting curves. There are no regularity requirements on the network, which already yields superior modelling capabilities compared to systems that are based on industry-standard NURBS surfaces. Originally, the shape of such a surface can be modified only locally by manipulating a curve in the network. In this process there is an inherent danger that the curve is being pulled away from intersections that it has with other curves. When this happens, the network is invalidated as a surface representation, and many curves may have to be adjusted to restore network consistency and surface quality. This thesis contributes a method that solves these problems by propagating changes that are made in one curve to curves in its vicinity. How and to what extent curves react to changes is controlled by two parameters that can be varied along the curve that is being manipulated. Any curve may be constrained in one or more degrees of freedom. The integrity of the curve network is implicitly conserved, as well as the geometric continuity of the surface. The result is a tool for the modification of curve-interpolating surfaces, which can easily be applied to large areas on models with any level of detail. This allows designers to concentrate on the creative process, rather than on planning chains of actions. They can explore different design variations, optimise shapes further, and generally be more productive. / Dette doktorgradsarbeidet presenterer en fremgangsmåte for formgivning og modifisering av datamaskinbaserte, skulpturerte flater. Metoden forbedrer et eksisterende system for data-assistert konstruksjon (DAK) som bygger dobbeltkrummede flater ved å interpolere et nettverk av skjærende kurver. Nettverket trenger ikke være regelmessig, noe som allerede gir bedre modelleringsmuligheter sammenliknet med systemer som er basert på standard NURBS flater. En slik flate kan opprinnelig bare endres lokalt ved å dra i en kurve. I denne prosessen er det fare for at kurven blir dratt fra skjæringspunkter den har med andre kurver. Hvis dette skjer, representerer ikke nettverket en flate lenger, og mange kurver må justeres for å få tilbake integriteten i nettverket og kvaliteten i formen. Denne avhandlingen bidrar med en metode som løser disse problemene ved å spre endringer som blir gjort i en kurve til andre kurver i nærheten. Hvordan og i hvilken utstrekning kurvene reagerer på endringen styres av to parametre som kan varieres langs kurven som blir endret. Enhver kurve kan låses i en eller flere frihetsgrader. Integriteten til nettverket samt glattheten i formen blir bevart automatisk. Resultatet er et redskap for modifikasjon av kurve-interpolerende flater som med letthet kan brukes på større områder av modeller med hvilken som helst grad av detalj. Dette gir designere muligheten til å konsentrere seg om det kreative, istedenfor å planlegge handlingsrekker. De kan utforske forskjellige designvariasjoner, optimalisere former ytterligere, og i det hele tatt være mer produktive.