Thesis (MScEng (Industrial Engineering))--University of Stellenbosch, 2010 / ENGLISH ABSTRACT: Additive Manufacturing (AM) refers to the technologies that use Computer Aided Design (CAD) data to produce plastic, metal, ceramic, paper, wax or composite materials parts. Their ability to join thin layers of liquid, powder or sheet materials together permits the production of parts, which are difficult or even impossible to produce, using any other manufacturing method. Even though these technologies are still developing, they are considered a major breakthrough in industry. One of the main problems that is facing the improvement and the spread of AM technologies, and its benefits worldwide, is the lack of knowledge about them. Still a lot of countries, educational and industrial organizations do not even know about AM technologies. This lack of knowledge of such technologies is keeping their cost artificially high, which is limiting the access to more AM advanced technologies and materials. It also makes it difficult to market the technologies and those who do not use AM technologies yet become unable to compete against those who do. The numbers of AM systems are continually growing, their capabilities and applications are improving and their cost is decreasing. Today there are more than 40 companies that produce over 100 different systems in Canada, China, France, Germany, Israel, Italy, Japan, South Korea, Sweden and the United States. These systems vary in their strengths, defects, applications, functions and limitations. This growth has led to an increase in current and potential users of AM from both the manufacturing and educational sectors. These users are however facing increasing complex problems when it comes to selecting the most appropriate commercial system(s) to suit their needs. The aim of this study is to develop an AM system selection program. The program will serve both as an educational tool and a decision making support tool to assist any potential purchasers in both the educational and industrial sectors. The AM system selection program is divided into two sections: the learning section and the selecting section. The learning section introduces the AM technologies by imparting knowledge to the new users; moreover, it inspires them to start using these technologies to get their benefits. Having a background in AM technologies enables the new users to make educated decisions and to discuss technical issues about the systems with the providers. The selecting section offers a decision making support tool to help the users to decide which system best suits their needs. This study can contribute to the promotion of AM technologies and their benefits worldwide, especially for the countries and organizations that have not yet used such technologies. / AFRIKAANSE OPSOMMING: Toevoegende vervaardiging verwys na al die tegnologie wat rekenaargesteunde ontwerp data gebruik om plastiek, metaal, keramiek, papier, saamgestelde materiale en waks parte te vervaardig. Die vermoë van die tegnologie om dun lae vloeistof, poeier of plaatmateriaal op mekaar te verbind laat die vervaardiging van parte wat moeilik of selfs onmoontlik is, deur die gebruik van ander vervaardigingsmetodes. Alhoewel hierdie tegnologieë nog in ‘n ontwikkelingsfase is, word dit as ‘n reuse deurbraak vir die bedryf beskou. Die verbetering, verspreiding en voordele van die tegnologie word hoofsaaklik belemmer deur ‘n tekort aan inligting daaroor. Baie lande, akademiese en industrieële organisasies is nog nie eens bewus dat sulke tegnologieë bestaan nie. Die tekort aan inligting veroorsaak dat kostes hoog bly en verhoed die vinnige uitbreiding van nog meer gevorderde tegnologieë en materiale. Verder bemoeilik dit ook die bemarking van die tegnologieë. Die aantal toevoegende vervaardigingsmasjiene groei jaarliks met beter vermoëns, laer kostes en ‘n groter verskeidenheid van toepassings. Tans is daar meer as 40 vervaardigers wat meer as 100 verskillende masjiene vervaardig in Kanada, China, Frankryk, Duitsland, Israel, Italië, Japan, Suid-Korea, Swede en Amerika. Al die masjiene verskil ten opsigte van hul funksies, beperkings en ook ten opsigte van sterkte, materiale en toepassings van parte. Die groei het gelei tot ‘n toename in gebruik van die tegnologie deur huidige en potensiële nuwe gebruikers van beide die vervaardigings en akademiese sektore. Die keuse van ‘n geskikte sisteem wat aan al ‘n gebruiker se vereistes voldoen, raak elke dag meer kompleks. Die doel van hierdie studie is die ontwikkeling van ‘n seleksie program vir toevoegende vervaardigingmasjiene. Die program sal dien as ‘n opleidingshulpmiddel en as ‘n basis vir masjienseleksie deur potensiële kopers. Die program bestaan uit twee dele: die opleidingsgedeelte en die selekteringsgedeelte. Die opleidingsgedeelte beskryf die verskeie toevoegende prosesse en motiveer gebruikers om die tegnologie aan te skaf weens die voordele. ‘n Agtergrond oor die verskeie tegnologieë stel die gebruiker in staat om ingeligte besluite te neem en tegniese vrae te kan stel aan verskaffers. Die selekteringsdeel het ‘n besluitnemingstruktuur wat help om die regte masjien te kies ten opsigte van verlangde vereistes. Hierdie studie kan help met die bevordering van toevoegende tegnologieë en hul voordele, veral vir lande en organisasies wat nog nooit voorheen sulke tegnologieë gebruik het nie.

CAPES / Um dos processos de manufatura aditiva mais popularesse baseia na fusão e deposição do material. O princípio de funcionamento aplicado nestes equipamentos restringe o fornecimento de matéria-prima, principalmente no mercado nacional, e a gama de materiais aplicáveis. O desenvolvimento de um equipamento capaz de processar o material na forma granulada contribuiria para a popularização do processo e para a ampliação da gama de materiais disponíveis a serem utilizados. Este trabalho descreve o desenvolvimento de um cabeçote de extrusão capaz de processar polipropileno granulado e extrudá-lo em forma de filamento contínuo e controlado. Este foi projetado de forma a reduzir o efeito da degradação sobre o material. Experimentos foram conduzidos a fim de caracterizar o comportamento dimensional dos filamentos gerados e assim permitir o seu melhor controle. A degradação do material no interior do cilindro aquecido foi avaliada por ensaios de espectroscopia no infravermelho e de tração em amostras de filamentos. Os resultados dos experimentos de extrusão mostraram que os filamentos apresentam variação de vazão ao longo do comprimento extrudado, sendo que a sua largura aumenta até atingir um patamar onde estabiliza. Os ensaios de espectroscopia mostram ocorrer degradação dentro do cilindro aquecido, mas os efeitos negativos sobre a resistência mecânica dos filamentos são menos acentuados quando empregando o cabeçote projetado. Concluiu-se que o princípio de extrusão por êmbolo com alimentação granulada é viável, necessitando, no entanto, desenvolver mecanismos de controle da extrusão mais adequados ao processo. / One of the most popular additive manufacturing processes is based on fuseddeposition of the material. The principleapplied to these machines makes difficult to find suppliers of raw materials, especially in brazilian market, and narrow the variety of materials applicable. The development of equipment able to process the material in the granular form will contribute to the process popularization and extension of available material to be used. This work describes the development of an extrusion head capable to process polypropylene granules and extrudeit as continuous and controlled filament. The extrusion head was designed in order to minimize the volume of material to be fused and reduce the effect of material degradation. Experiments were conducted to characterize the dimensional behavior of the filaments generated and thus allow its better control. The material degradation inside the extrusion head was assessed by infrared spectroscopyand its negative effects over filaments strength by tensile tests.The results of the extrusion experiments showed that the filaments have flow variation along the extruded length, following an increasing curve until a value where its average stabilizes. Spectroscopy showed that degradation occurs inside the heated cylinder, but its negative effects on material strength are less intense when using the designed extrusion head. It was concluded that the extrusion plunger principle with granulated feeding is viable for Additive Manufacturing, requiring, however, better control mechanisms of the extrusion to enable the manufacture of uniform and cohesive parts. / 5000

Thesis: M.S., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1981 / Includes bibliographical references. / by Clinton Sebastian Stanovsky. / M.S. / M.S. Massachusetts Institute of Technology, Department of Mechanical Engineering

This project demonstrates an understanding of how a manufacturing organization can use the methodology of open systems integration to upgrade the design of the network architecture for their manufacturing information system. In upgrading the design of their manufacturing information system's network architecture, a limited application of the system engineering process is used to produce an initial conceptual design. As technology grows, many manufacturing organizations are taking the necessary steps to upgrade their operations to remain competitive in these changing times. This project explores this problem which many manufacturing organizations are experiencing as technology continues to leap frog past its current limitations. Many of the manufacturing organizations which have been in operation for years are having difficulties competing with many of the new manufacturing organizations with their current technologies. / Master of Science

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2008. / Low Cost Automation (LCA) is of immense importance to industry, and even more so for small scale industries. In implementing LCA determining cost effective and efficient actuator alternatives present challenges for design engineers. Most often decisions are experiential or entirely based on manufacturer recommendations. Experience based decisions are most often biased with respect to the engineers’ knowledge. Similarly, manufacturer recommendations are restricted to their own products and are as such also biased. Either way, sub-optimum drive alternatives may sometimes be chosen. This demonstrates the need for making better informed decisions based on more than experience and what is available for use. This thesis reports the development of an electric actuator selection procedure and aid for use in the early layout design phase. It provides readily accessible information on technically viable actuator options. Experiential knowledge of experts in the field, commercial information, as well as data obtained from experimentation was used in its development. Being orientated towards LCA, the procedure has been targeted at the application of electric motors and their associated control technologies but can be extended to hydraulic, pneumatic and other actuators. In achieving a wider applicability of the selection aid, a generic set of actuator properties descriptive of most actuators was formulated. An AC drives control evaluation was conducted for developing the selection procedure and aid. It provided a means to validate some selection aid rules associated with actuator controllability. Quantitative data on speed and positioning accuracies of common AC three phase motors and their associated inverter technologies were the targeted results of the experimentation.

Este trabalho utiliza a Programação Linear Inteira Mista (MILP) para investigar as diferenças de produtividade encontradas em uma Linha de Montagem de Modelo Misto. A abordagem de solução foi através da construção e resolução de modelos matemáticos do problema de balanceamento de linhas de montagem de modelo misto (MALBP – Mixed-Model Assembly Line Balancing Problem), seguido do problema de sequenciamento de carros (PSC – Car Sequencing Problem). Uma simulação discreta foi utilizada para verificar os resultados dos modelos matemáticos. O estudo relata o caso real de uma linha de montagem da indústria automotiva das partes móveis das carrocerias de três diferentes veículos compartilhando a mesma linha de produção. A linha de produção é caracterizada como baixa cadência (de até 15 veículos/hora) e totalmente manual. A linha é constituída por mesas de rolos em série onde o acionamento é do tipo de passo não sincronizado. O objetivo é investigar como manter o melhor nível de produtividade da linha de produção e, ao mesmo tempo, manter a característica de flexibilidade para atender a uma demanda variável em volume e diversidade de produto. São apresentados resultados desse trabalho que indicam que é possível a obtenção de alguns balanceamentos flexíveis para alguns mixes de produtos, o que permite manter a diferença nos tempos de produção no limite de 6%, para esta correta combinação de balanceamento-sequenciamento. No entanto, verificando as demais combinações possíveis para os seis mixes de produtos avaliados, o tempo de produção apresentou diferenças de até 19%, dependendo da sequência de entrada dos produtos para um certo mix. Outro fator que também ocasionou diferenças dos tempos produtivos, de 20% em média, foi em relação a alocação/ausência de postos pulmões (buffers). O horizonte da análise, a priori, foi de um lote de produção de uma hora para o modelo matemático e de uma semana de produção para o modelo de simulação discreta. Os resultados obtidos no estudo indicam que é possível operar uma linha de montagem flexível com uma produtividade equiparável a linhas de montagem de único modelo, se cuidados relativos ao balanceamento e sequenciamento produtivos forem observados. Por outro lado, se as condições operacionais de balanceamento e sequenciamento para as linhas de montagem de modelos/produtos mistos não forem consideradas, as perdas acumuladas na taxa de produção podem ser significativas (por exemplo, tempos de produção para algumas condições de teste ultrapassaram em 30% o valor teórico estimado). / This work uses Mixed Integer Linear Programming (MILP) to investigate productivity differences found in a Mixed-Model Assembly Line. The solution approach was based on construction and resolution of mathematical models for the Mixed-Model Assembly Line Balancing Problem (MALBP), followed by the Car Sequencing Problem (CSP). A discrete simulation was used to check the results obtained by the mathematical models. The study reports the real case of an automotive metal line that assemblies the closures of three different vehicles, sharing the same production line. The production line is characterized as low cadence (e.g., up to 15 vehicles/hour) and fully manual. The line is formed by roller tables in series with unpaced devices. The main objective is to investigate how to maintain productivity, while maintaining the flexibility characteristic to meet a variable demand in volume and product diversity. Results of this study are presented and indicate that some flexible balancing mixes are viable. Production time differences of no more than 6% were observed in such flexible choices. However, the checking of some possible combinations for the six mixes of evaluated products showed a production time difference up to 19%, depending on the sequence of products for a certain mix. Another factor that also influenced production time differences, 20% on average, was the allocation of buffers. The horizon of analysis encompasses a lot of production of one hour, to the mathematical model, and a week for discrete simulation. The obtained results indicate that it is possible to operate a flexible assembly line with a level of productivity similar to a single product line, in case of careful choices in balancing/sequencing. On the other hand, if the operating conditions of balancing and sequencing were not taken into account the cumulative loss in throughput may be significant (e.g., for some studied cases, production time exceed 30% the theoretical value).