Published Article / At Helsinki University of Technology rapid prototyping, rapid tooling and rapid manufacturing technologies and applications have been researched since late 1980s. The Integrated Design and Manufacturing research group has concentrated on new industrial Rapid Prototyping and Manufacturing (RP&M) applications within product development and manufacturing. This paper is based on research projects realized in 2001 - 2004 in cooperation with several industrial companies. New developments within industrial product development paradigms and processes will be discussed. The paper attempts to link current industrial management sciences research with latest developments within rapid manufacturing technologies. Product platforms, product customization and networked manufacturing have become common product development management paradigms in many industrial sectors. These paradigms have lead to an increasing number of product configurations and variations. Traditionally cost comparisons between RP&M processes and conventional manufacturing processes have been based on break even point calculations. The latest product development and manufacturing paradigms places agility in production and efficient prototyping technologies among others in an important role. Conventional cost per part comparison methods to value rapid manufacturing need to be re-engineered. In those comparisons the first break even point does not describe the overall rapid manufacturing economy. For example, effects of neccesity for product change, tool wear or tool defect have to be taken into consideration. In this paper the new cost modeling technology and some industrial case studies will be described.

Published Article / Rapid tooling (RT) in the context of this research presents the possibility of improving the traditional investment casting process by shortening lead times while still maintaining affordable costs and required quality. Various rapid prototyping processes are available that can be used to create direct metal, polymer or wooden dies for this casting technology. This paper presents results gained in an AMTS project, focusing on RT development for investment casting of light metals. One of the most widely used layer manufacturing processes available in South Africa is selective laser sintering. A machine produced by the German manufacturer EOS (process known as laser sintering) utilising this technology was selected for the study. Two of the materials that are suitable for rapid die making are used, which in tum reflects different mechanical properties and process economics. A standard benchmark part was used as a study base. Two dies were built, one in alumide and one in polyamide. A comprehensive measurement programme was conducted, followed by an appropriate statistical analysis and evaluation regarding accuracy and surface finish. A number of wax patterns were produced. The best wax patterns from each die were selected and evaluated. The subsequently produced castings in AI, Mg and TI were further examined and evaluated. Various issues concerning the reinforcement, wax injection, pattern removal, accuracy and surface finish of the dies are discussed in the paper. The research concludes that rapid tooling techniques can be successfully used for creating accurate dies in order to shorten lead times in the investment casting process chain.

ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / When network-centric flight test system components are developed concurrently, it is necessary to produce relevant simulated network traffic for exercising the network devices and other processing subsystems prior to system integration. Having an accurate and repeatable pattern of simulated network traffic is extremely important for debugging and subsystem integration. The simulated network traffic must be both representative of the real system and repeatable to aid test efforts. Our solution to this problem was to develop a model-driven network traffic generator – NETGEN. Using NETGEN to resolve errors, stress test, and verify requirements, we have achieved otherwise unattainable correctness, reliability, and success in our systems.

published_or_final_version / abstract / Mechanical Engineering / Master / Master of Philosophy

published_or_final_version / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

Approved for public release; distribution is unlimited / As demand for hard real-time and embedded computer systems increases, a new approach to software development is critical. Software engineers and users would benefit from an automated methodology allowing validation of design specifications or functional requirements early in the development life cycle. A fast, efficient, easy-to-use tool would increase productivity and would enhance user confidence that software would be delivered at less cost and on schedule. The Computer Aided Prototyping System (CAPS) is a conceptualized tool providing these capabilities. This thesis represents a pioneering effort to develop a Static Scheduler for the CAPS Execution Support System using the Ada programming language. The Static Scheduler initially extracts critical operators, timing constraints and precedence relationships from a high-level prototype source program. The Static Scheduler then creates a static schedule for run-time execution, using worst case scenarios, guaranteeing that timing constraints are met. The primary goal of this thesis is to provide the scheduling algorithms and implementation guidelines for the Static Scheduler. Secondary goals are to demonstrate the significance of continued research to telecommunications applications and to demonstrate the feasibility of Ada as the implementation language. / http://archive.org/details/staticschedulerf00jans / Lieutenant, United States Navy

A especialidade de Prótese Buco-Maxilo-Facial é responsável por reconstruções complexas da face e do crânio. Entretanto, com a utilização de impressões convencionais, é difícil se alcançar uma adequada adaptação clínica para a reabilitação do paciente. Assim, algumas vêzes, faz-se necessária a obtenção de modelos tridimensionais (3D) que reproduzam a realidade clínica. O objetivo deste estudo é comparar os protótipos obtidos com diferentes protocolos de aquisição de imagem provenientes de distintos aparelhos de tomografia computadorizada com relação à rugosidade superficial, área reconstruída e dose de exposição gerada, procurando estabelecer o mais adequado para a confecção de protótipos de crânio. Para isso, nove protótipos de um fragmento craniofacial seco foram confeccionados. A comparação entre os protótipos quanto à lisura superficial e à área reconstruída foi realizada por meio da Análise de Variância (ANOVA). Nos casos em que a avaliação indicou diferença significativa, foi aplicado como complemento o Teste de Comparações Múltiplas de Tukey. O nível de significância adotado foi de 5%. Em relação à análise de rugosidade as diferenças encontradas não demonstraram correlação com a área reconstruída. Já em relação aos diferentes protocolos, diferenças significativas foram observadas nos protótipos com respeito à área reconstruída e dose de radiação gerada. Pode-se concluir, frente aos resultados encontrados, que as imagens geradas pelos tomógrafos de feixe cônico e feixe em leque, utilizando os protocolos com as resoluções máximas estudadas, estão indicadas para a confecção de protótipos. Contudo, o que deve nortear a seleção do melhor protocolo tomográfico deve ser o propósito da indicação clínica correlacionado com o princípio ALARA (As Low As Reasonably Achievable). / Oral-maxillo-facial prosthodontics is the study of complex face and skull reconstructions. In view of the insufficient degree of adjustment of conventional impression to enable proper clinical rehabilitation, among other reasons, practitioners increasingly resort to 3D models that accurately reproduce the clinical reality. The aim of this study is to determine the optimal selection of imaging device and protocol for use in skull prototyping. The surface roughness and reconstructed area of nine prototypes obtained from a dried craniofacial specimen using different image acquisition protocols and CT devices were measured, in addition to measurements of the radiation dose potentially received by the patient. ANOVA of the surface roughness, reconstructed area and radiation dose data enabled statistical comparisons among the prototypes. Where significant differences were found, Tukey’s multiple-comparison test was conducted, using a significance level of 5%. No correlation was found between surface roughness and reconstructed area. However, significant differences in reconstructed area and radiation dose were found among the different protocols. These results support the use of images generated by CBCT or fan beam CT for the construction of prototypes, using the protocols with the highest resolution. Nevertheless, the selection of the most appropriate TC protocol should be based on the particular clinical indication along with the ALARA (as low as reasonably achievable) principle.

This research explores the benefits of teaching design thinking to middle school students. The design thinking process, with its emphasis on iterative rapid prototyping, portrayal of mistakes as learning opportunities, and mantra of “fail early and often” stands in stark contrast with the typical high-stakes, failure-averse culture of the classroom. Educators laud the process as a way to teach integrative STEM curriculum, foster 21st century skills, and engage students in constructivist learning. However, few studies have examined the potential motivational benefits for K-12 students who learn design thinking. Therefore, the present research explored if design thinking instruction could reframe how students perceived failures and teach them to iterate, or “try again,” as they engaged with complex problems. In two quasi-experimental studies, with 78 and 89 students respectively, I investigated the effectiveness of a brief intervention, intended to teach a critical component of design thinking – the iterative process of design – and its unique philosophy surrounding failure, whereby mistakes are natural and expected learning opportunities as students work towards increasingly better solutions to ill-defined problems. Students in an iterative design mindset condition (Mindset) learned about iterative rapid prototyping, employed the process on two different design challenges with embedded reflections, and developed brochures about design thinking. In a comparison STEM-focused condition (STEM), students participated in an analogous intervention focused on the importance of using science and math in design. Results from both studies indicated that Mindset students learned the philosophy and process of iterative rapid prototyping from the brief intervention and were able to transfer the process to a target design task. Furthermore, results confirmed a performance benefit to iterating early and often. Moreover, Study 2 results suggested that students in the Mindset condition developed more adaptive attitudes to failure, compared to students in the STEM condition. These studies provide compelling evidence that design thinking education has the potential to instill persistence in the face of ill-defined problems, reframe failure, and improve task performance for middle school students. This work also presents a model for evaluating the design thinking process using quasi-experimental studies and quantitative methods. This dissertation consists of a brief summary of relevant literature and two journal-style articles. First, I define design thinking and explain how iterative rapid prototyping connects to key motivational constructs in the classroom, ultimately resulting in improved engagement and performance. Next, a design case describes the final intervention used in Study 2 and notes the ways in which the learning sciences literature and the iterative development process informed its design. I consider trade-offs in the effort to develop curriculum for a research study and detail lessons learned along the way. Subsequently, an empirical chapter presents two studies of the design thinking intervention. I end by considering the implications of this body of research and suggest future directions for researchers interested in bringing design thinking into the classroom.

During the past decades there has been an increase in the use of geosynthetics in construction due to their versatility in providing a wide array of functions such as reinforcement, containment, separation, filtration and drainage. Often, geosynthetics are used in conjunction with other geosynthetics to accomplish these functions. However, geosynthetics create possible planes of weakness which can lead to failures. Textured geomembranes are widely used within landfill and mining industries due to their containment and shear strength properties, however, there are subjected to a wide array of loads and environments which are potentially hazardous, as such is of utmost importance to retain their integrity in order to avoid ecological disasters. The challenge is to understand how geomembranes resist damage, wear and which of these factors control the development of wear on textured geomembranes. Digital imaging techniques have been used in order to develop a protocol that describes the quantification of wear on textured structured geomembranes. Direct shear tests were performed to induce wear on the geomembrane textures (asperities) to analyse the wear mechanisms and study the factors that induce wear on the asperities. The research showed that normal stress and shear displacement have a major role in the development of wear on interfaces. However, the geometrical characteristics of the geomembrane asperities control the amount of wear the geomembrane can sustain without significant shear strength loss. These outcomes help to better understand the behaviour of interfaces which have as component geomembranes, leading to more robust designs. This study also proposed new asperity texture shapes by using Rapid Prototyping (RP) techniques, such as Selective Laser Sintering and Fused Filament Fabrication. Using RP techniques to create new textures for the geomembrane, could allow the creation of textures which have increased shear strength thresholds and better withstand wear, allowing for more advanced and economical designs.

In der vorliegenden Arbeit wurden erstmals im 3D-Pulerdruckverfahren hergestellte Struvit-Matrizes auf ihre Eignung als Trägermaterial für Knochenzellen in vitro untersucht. Hierzu wurde die Zytokompatibilität sowie die chemische Löslichkeit von gedruckten Struvit-Strukturen betrachtet. In einem zweiten Schritt wurde untersucht, ob die biologische Funktion von BMP-2-Lösungen nach Durchlaufen des Druckprozesses erhalten bleibt und ob es möglich ist, BMP-2 unter Beibehaltung seiner biologischen Wirksamkeit direkt in Struvit-Matrizes zu drucken. Als Reaktanten zur Herstellung der Struvit-Matrizes wurde modifiziertes Farringtonit-Pulver mit definierter Körnung und eine äquimolare Binder-Lösung aus DAHP und ADHP verwendet. Die untersuchten Zellkulturträger mit Magnesiumammoniumphosphatchemie zeigten eine ausreichende Zytokompatibilität in vitro. Außerdem wurde gezeigt, dass thermolabile Proteine wie BMP-2 im 3D-Pulverdruckverfahren unter weitgehender Beibehaltung ihrer biologischen Wirksamkeit in vitro grundsätzlich prozessierbar sind. Die Freisetzung direkt eingedruckter Proteine aus den Struvit-Matrizes blieb jedoch hinter den Erwartungen zurück. Mit Struvit steht ein alternatives Zementsystem für den 3D-Pulverdruck zur Verfügung, welches spezifische Vorteile gegenüber den etablierten Calciumphosphaten bietet. Weitere Untersuchungen sind erforderlich, um die Ursache für die geringe BMP-Freisetzung aus den Struvit-Matrizes zu ermitteln und die Vorteile der neutralen Abbindereaktion voll nutzen zu können. / The purpose of the present study was the investigation of 3d powder printed struvite-scaffolds as a carrier material for osteoblastic cells in vitro. For this purpose, their cytocompatibility and their chemical solubility were observed. In a second step we analysed, if BMP-2 could pass through the whole printing process without losing its biological function and furthermore if it is possible to print BMP-2 directly into struvite-scaffolds without a significant loss of biological activity. As reactants for the fabrication of the struvite-scaffolds, we used a modified farringtonite-powder and a binder solution consisting of an equimolar mixture of DAHP and ADHP. The investigated struvite-scaffolds showed a sufficient cytocompatibility. It was also shown, that thermolabile proteins, such as BMP-2, could be processed in 3d powder printing without losing much of their biological activity in vitro. The release of directly imprinted proteins out of the struvite scaffolds remained unsatisfying. Struvite is an alternative hydraulic-setting cement for 3d powder printing with certain advantages over the established calcium phosphate cements. Further investigations are necessary to identify the reasons for the low BMP-release out of the struvite-scaffolds and to take full advantage of the neutral setting reaction of struvite-cements.