This dissertation presents information gathered and analyzed through an electronic internet-based Delphi Survey process. The purpose of this study is to identify a consensus of factors that might forecast the future effects of Rapid Prototyping (RP) technology on engineering design education when used for the purpose of overcoming the limitations of 2D representation of 3D space. The identification of consensus was developed from the collection of opinions from a panel of experts in RP technology. Early adopters of emerging technologies can reduce risk through careful research, but decisions must often be made before significant quantitative data are available. Expert subjective judgment may be a valuable source of information for making decisions. RP is just one of the tools used in engineering design education for visualization. This research should help to guide faculty members in making decisions regarding the use of RP technology in the curriculum. The one consensus reached by the panel is that 3D CAD will replace 2D CAD as the default modeling tool in most product-design related curricula within 5 years. The general conclusion of the study is that the appropriate use of the technology in the curriculum is largely situational.

The focus of this dissertation is on the development of a solid freeform fabrication (SFF) process for the design and manufacture of porous biodegradable orthopaedic implants from calcium polyphosphate (CPP). Porous CPP structures are used as bone substitutes for regenerating bone defects and/or as substrates in formation of so-called “biphasic” implants for repair of damaged osteochondral tissues. The CPP implants can be utilized in the treatment of many musculoskeletal diseases, osteochondral defects, and bone tumours while replacement of the defect site is required. In this study, the fabrication of CPP structures was developed through a powder-based SFF technique known as adhesive bonding 3D-printing. SFF is an advanced alternative to the “conventional” fabrication method consisting of gravity sintering of CPP pre-forms followed by machining to final form, as SFF enables rapid manufacturing of complex-shaped bio-structures with controlled internal architecture. To address the physical and structural properties of the porous SFF-made components, they were characterized using scanning electron microscopy, micro-CT scanning and mercury intrusion porosimetry. Specific surface area and permeability of the porous structures were also determined. Additionally, the chemical properties (crystallinity) of the specimens were identified by X-ray diffraction. The mechanical properties of the crystalline CPP material were also measured by micro- and nano-indentation. Moreover, the porous structures were tested by uniaxial and diametral mechanical compression to determine the compressive and tensile strengths, respectively. Furthermore, the effect of the stacked-layer orientation on the mechanical properties of the SFF-made constructs was investigated through the production of samples with horizontal or vertical stacked-layers. The properties of the SFF-made samples were compared with those of the conventionally-made CPP constructs. The SFF-made implants showed drastically higher compressive mechanical strength compared to the conventionally-formed samples with identical porosity. It was also shown that the orientation of the stacked-layer has substantial influence on the mechanical strengths. Moreover, this thesis examined the ability of in vitro forming of cartilaginous tissue on the SFF-made substrates where the chondrocytes cellular response to the CPP implants was evaluated histologically and biochemically. In addition, an initial in vivo assessment of the CPP structures as bone substitutes was conducted using a rabbit medial femoral site model. Significant amount of new-bone was formed within the CPP porous constructs during the 6-week implantation period demonstrating appropriate biological response of SFF-made CPP structures for bone substitute applications. Another accomplishment of this thesis was the development of a mathematical model which predicts the compact density of powder layers spread by a counter-rotating roller in the SFF technique. The results may be used in the control of the apparent density of the final implant. The potential of the developed SFF method as an efficient and reproducible technique for the production of porous CPP structures for use in orthopaedics and musculoskeletal tissue regenerative applications was concluded.

Rapid prototyping (RP) is a set of fabrication technologies that are used to produce accurate parts directly from computer aided drawing (CAD) data. These technologies are unique in a way that they use an additive fabrication approach in which a three dimensional (3D) object is directly produced. In this thesis study, a RP application with a modular architecture is designed and implemented to satisfy the possible requirements of future rapid prototyping studies. After a functional classification, the developed RP software is divided into View, RP and Slice Modules. In the RP module, the process parameter selection and optimal build orientation determination steps are carried out. In the Slice Module, slicing and tool path generation steps are performed. View Module is used to visualize the inputs and outputs of the RP software. To provide 3D visualization support for View Module, a fully independent, open for development, high level 3D modeling environment and graphics library called Graphics Framework is developed. The resulting RP application is benchmarked with the RP software packages in the market according to their memory usage and process time. As a result of this benchmark, it is observed that the developed RP software has presented an equivalent performance with the other commercial RP applications and has proved its success.

The design of curves and surfaces in C.A.D. systems has many applications in car, plane or ship industry. Because they offer more flexibility, rational functions are often preferred to polynomial functions to modelize curves and surfaces. In this work, several methods to generate rational Bezier curves and surfaces which minimize some functionals are proposed. The functionals measure a technical smoothness of the curves and surfaces, and are related to the energy of beams and plates in the sense of the elasticity theory.

The focus of this dissertation is on the development of a solid freeform fabrication (SFF) process for the design and manufacture of porous biodegradable orthopaedic implants from calcium polyphosphate (CPP). Porous CPP structures are used as bone substitutes for regenerating bone defects and/or as substrates in formation of so-called “biphasic” implants for repair of damaged osteochondral tissues. The CPP implants can be utilized in the treatment of many musculoskeletal diseases, osteochondral defects, and bone tumours while replacement of the defect site is required. In this study, the fabrication of CPP structures was developed through a powder-based SFF technique known as adhesive bonding 3D-printing. SFF is an advanced alternative to the “conventional” fabrication method consisting of gravity sintering of CPP pre-forms followed by machining to final form, as SFF enables rapid manufacturing of complex-shaped bio-structures with controlled internal architecture. To address the physical and structural properties of the porous SFF-made components, they were characterized using scanning electron microscopy, micro-CT scanning and mercury intrusion porosimetry. Specific surface area and permeability of the porous structures were also determined. Additionally, the chemical properties (crystallinity) of the specimens were identified by X-ray diffraction. The mechanical properties of the crystalline CPP material were also measured by micro- and nano-indentation. Moreover, the porous structures were tested by uniaxial and diametral mechanical compression to determine the compressive and tensile strengths, respectively. Furthermore, the effect of the stacked-layer orientation on the mechanical properties of the SFF-made constructs was investigated through the production of samples with horizontal or vertical stacked-layers. The properties of the SFF-made samples were compared with those of the conventionally-made CPP constructs. The SFF-made implants showed drastically higher compressive mechanical strength compared to the conventionally-formed samples with identical porosity. It was also shown that the orientation of the stacked-layer has substantial influence on the mechanical strengths. Moreover, this thesis examined the ability of in vitro forming of cartilaginous tissue on the SFF-made substrates where the chondrocytes cellular response to the CPP implants was evaluated histologically and biochemically. In addition, an initial in vivo assessment of the CPP structures as bone substitutes was conducted using a rabbit medial femoral site model. Significant amount of new-bone was formed within the CPP porous constructs during the 6-week implantation period demonstrating appropriate biological response of SFF-made CPP structures for bone substitute applications. Another accomplishment of this thesis was the development of a mathematical model which predicts the compact density of powder layers spread by a counter-rotating roller in the SFF technique. The results may be used in the control of the apparent density of the final implant. The potential of the developed SFF method as an efficient and reproducible technique for the production of porous CPP structures for use in orthopaedics and musculoskeletal tissue regenerative applications was concluded.

Inspection of optical components is essential to assure the quality and performance of optical systems. Evaluation of optical components includes metrology measurements of surface topography. It also requires optical measurements including refractive index, thin film thickness, reflectivity and transmission. The dispersion characteristics of optical constants including refractive index are also required. Hence, various instruments are used to make these measurements in research laboratories and for quality assurance. Clearly, it would be a significant advantage and cost saving if a technique was developed that could combine surface metrology with optical measurements. {Coherence Scanning Interferometry} (CSI) (also referred to as {Scanning White Light Interferometry} (SWLI)) has been used widely to measure surface topography with sub-nanometre vertical resolution. One of the benefits of the CSI is that the technique is non-contacting and hence non-destructive. Thus the test surfaces are not affected by the measurement using a CSI instrument whereas damage to the surfaces can occur when using traditional contact methods such as stylus profilometry. However use of CSI is geometrically limited to small areas ($\lesssim 10 \times 10$ mm) with gentle slopes ($\lesssim \ang{40}$) because of the numerical aperture of objective lens whereas stylus profilometry works well with larger areas and higher slopes due to the range of motion of the gauge and the traverse unit. Since the CSI technique is optical and involves light reflection and interference it is possible to extend the technique for the measurement of the thickness of transparent films, the roughness of surfaces buried beneath thin films or interfacial surfaces. It may also be used to determine spectral complex refractive index. This thesis provides an analytical framework of new methods to obtain complex refractive index in a visible light domain and interfacial surface roughness (ISR). It also provides experimental verification of these new capabilities using actual thin film model systems. The original Helical Complex Field (HCF) function theory is presented followed by its existing extensions that enable determination of complex refractive index and interfacial surface roughness. Further theoretical extensions of the HCF theory are also provided: A novel theory to determine the refractive index of a (semi-)transparent film is developed to address the constraint of the current HCF theory that restricted its use to opaque materials; Another novel theory is provided to measure ISR with noise compensation, which avoids erroneous surface roughness caused by the numerical optimisation affected by the existence of noise. The effectiveness of the ISR measurement with noise compensation has been verified using a number of computer simulations. Stylus profilometry is a well established method to provide a profile and has been used extensively as a 'reference' for other techniques. It normally provides a profile on which the roughness and the waviness are computed. Extension of the stylus profilometry technique to areal measurement of asymmetrical surfaces, namely raster scan measurement, requires a system to include error compensation between each traverse. The system errors and the random errors need to be separately understood particular when the measurement of a surface with nanometre-order accuracy is required. In this thesis a mathematical model to locate a stylus tip considering five mechanical errors occurring in a common raster scan profilometer is provided. Based on the model, the simulator which provides an areal measurement of a sphere was developed. The simulator clarified the relationship between the Zernike coefficients obtained from the form residual and the size of the errors in the form of partial derivatives of Zernike coefficients with respect to the errors. This provides theoretical support to the empirical knowledge of the relationship between the coefficients and the errors. Furthermore, a method to determine the size of errors directly from Zernike coefficients is proposed supported by simulations. Some of the error parameters were accurately determined avoiding iterative computation with this method whereas the errors are currently being determined by iterative computation.

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.

Les formes asphériques et les surfaces complexes sont une classe très avancée d'éléments optiques. Leur application a considérablement augmenté au cours des dernières années dans les systèmes d'imagerie, l'astronomie, la lithographie, etc. La métrologie de ces pièces est très difficile, en raison de la grande gamme dynamique d'information acquise et la traçabilité à l'unité SI mètre. Elle devrait faire usage de la norme infinie; (Méthode de zone minimum ou la méthode Min-Max) pour calculer l'enveloppe entourant les points dans le jeu de données en réduisant au minimum la différence entre l'écart maximum et l'écart minimal entre la surface et l'ensemble de données. Cette méthode a une grande complexité en fonction du nombre de points, enplus, les algorithmes impliqués sont non-déterministes. Bien que cette méthode fonctionne pour des géométries simples (lignes, plans, cercles, cylindres, cônes et sphères), elle est encore un défi majeur lorsqu' utilisée pour des géométries complexes (asphérique et surfaces complexes). Par conséquent, l'objectif de la thèse est le développement des algorithmes d'ajustement Min-Max pour les deux surfaces asphériques et complexes, afin de fournir des algorithmes de référence robustes pour la grande communauté impliquée dans ce domaine. Les algorithmes de référence à développer devraient être évalués et validés sur plusieurs données de référence (Softgauges) qui seront générées par la suite. / Aspheres and freeform surfaces are a very challenging class of optical elements. Their application has grown considerably in the last few years in imaging systems, astronomy, lithography, etc. The metrology for aspheres is very challenging, because of the high dynamic range of the acquired information and the traceability to the SI unit meter. Metrology should make use of the infinite norm; (Minimum Zone Method or Min-Max method) to calculate the envelope enclosing the points in the dataset by minimizing the difference between the maximum deviation and the minimum deviation between the surface and the dataset. This method grows in complexity as the number of points in the dataset increases, and the involved algorithms are non-deterministic. Despite the fact that this method works for simple geometries (lines, planes, circles, cylinders, cones and spheres) it is still a major challenge when used on complex geometries (asphere and freeform surfaces). Therefore, the main objective is to address this key challenge about the development of Min-Max fitting algorithms for both aspherical and freeform surfaces as well as least squares fitting algorithms, in order to provide robust reference algorithms for the large community involved in this domain. The reference algorithms to be developed should be evaluated and validated on several reference data (softgauges) that will be generated using reference data generators.

Thesis (M. Tech.) -- Central University of Technology, Free State, 2008 / As the tendency to use sol id freeform fabrication (SFF) technology for the manufacture of end use parts grew, so too did the need for a set of general guidelines that would aid designers with designs aimed specifically for rapid manufacture. Unfortunately, the revolutionary additive nature of SFF technology left certain fundamental principles of conventional design for manufacture and assembly outdated. This implied that whole chapters of theoretical work that had previously been done in this field had to be revised before it could be applied to rapid manufacturing. Furthermore, this additive nature of SFF technology seeded a series of new possibilities and new advantages that could be exploited in the manufacturing domain, and as a result drove design for rapid manufacturing principles even further apart from conventional design for manufacture and assembly philosophy. In this study the impact that rapid manufacture had on the conventional product development process and conventional design for manufacture and assembly guidelines were investigated. This investigation brought to light the inherent strengths and weaknesses of SFF, as well as the design for manufacture and assembly guidelines that became invalid, and consequently lead directly to the characterization of a set of design for rapid manufacture guidelines.

This thesis attempts to resolve the contradictory relationship between the ecological merits of wood construction and the significant material intensity of recent free form timber surface structures. The building industry is now adept in the design and construction of freeform surface architecture, however new challenges have been introduced with the environmentally conscious desire to build these structures in wood. Lacking the formal versatility of steel and concrete, wood introduces a great deal of difficulty in the realization of complex form at an architectural scale. Powerful digital design and fabrication tools have recently made it possible to model, analyze and construct these buildings, but at the cost of heavy structural solutions that involve energy intensive fabrication processes and significant material waste. This approach contradicts the ecological benefits of wood, and raises the question of whether it is possible to achieve free and expressive form in timber surface architecture while maintaining an economy of means and material. This question is addressed through the development of a generative design tool for the creation of material conscious free form timber surface architecture. The formation of the tool is informed by the field of computational morphogenesis, which draws from the natural growth processes of biological structures in the virtual synthesis of form. The tool is conceived as a morphogenetic material system, which consists of a generative algorithm that integrates material, structure and form in a single computational process. Specific material saving techniques deployed in the algorithm draw from existing research in timber shell design and material optimization. Established methods in the use of geodesic lines for the structural patterning of wood shells and stress driven material distribution make up the core concepts deployed in the algorithm. The material system is developed, refined and tested through the design and construction of an experimental free form timber lattice.