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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Micromoulding: process measurements, product morphology and properties.

Whiteside, Benjamin R., Martyn, Michael T., Coates, Philip D., Greenway, G., Allen, P., Hornsby, P. January 2004 (has links)
No / The growth in Micro Electro-Mechanical Systems (MEMS) and demand for functional devices at smaller and smaller length scales has placed increasing demands on industry for product miniaturisation. Consequently, the micro-injection moulding (micromoulding) technology has evolved for the mass production of minute, intricate, polymer and composite components. Although there has been significant growth in the technology, there is little understanding of the effects of the process dynamics on product properties. This paper presents details of a programme of work conducted within these laboratories with the objectives of enhancing the understanding of polymer processing-property interaction. More particularly, the effects of microscale processing on the rheological, mechanical and tribological properties of engineering and commodity polymers, nanocomposites, metal and ceramic injection moulded feedstock and biomaterials are being explored. Simple analysis reveals that process conditions are potentially more severe on melts than those encountered during conventional moulding. High shear and rapid cooling rates combined with a large surface area to volume ratio may have a much greater influence over the resultant properties of a micromoulded product. A Battenfeld Microsystem50 micromoulding machine has been instrumented with a variety of sensors and data acquisition equipment, producing process data for a number of different cavity geometries. A novel microinjection compounding (MIC) machine has also been developed minimising the process stages and reducing material exposure to excessive residence times. This paper gives details of the effects of micromoulding process conditions on component surface morphology and mechanical properties measured using SEM, atomic force microscopy and nano-indentation techniques.
2

An Integrated Process Planning System for Machining and Inspection

Zhao, Yaoyao 01 December 2009 (has links) (PDF)
Due to the deterministic nature of manufacturing processes, measuring important process parameters and performing timely adjustment is an effective way to improve manufacturing efficiency and quality. In-process measurement is such a method. It is capable of monitoring manufacturing processes in real time. However, the current information flow between different manufacturing processes is segmented due to the lack of a consolidated data model to represent sufficient information of a product. This directly results in segmented process planning for in-process measurement. The establishment of STEP (STandard for Exchange of Product data) offers manufacturers a new method to exchange product data through the entire product lifecycle. As an extension to STEP, STEP-NC provides the potential to finally close the gap between design and manufacturing in the drive for a complete and integrated product development environment. The STEP/STEP-NC data model is a long overdue improvement in the domain of process planning for Computer Numerical Controlled (CNC) machining in the industry where G-codes have been in use for more than half a century. STEP/STEP-NC brings richer information to the CNC machining industry presenting an opportunity for the development of more intelligent, interoperable and informative machining processes. The research work documented in this thesis introduces a consolidated STEP/STEP-NC data model and system for an automatic and integrated process planning system for machining, in-process measurement, and feedback. This research first developed the current STEP/STEP-NC data model with new definitions covering tolerance requirement information, and measurement operation information. A mechanism to link tolerance requirements and machining feature information was also developed to provide the crucial connection between machining and measurement. With sufficient information provided by the proposed STEP data model, the concept of an integrated process planning system was conceived to carry out automated process planning for machining and in-process measurement. The system is able to analyse and select critical tolerance(s) from an input data file, generate measuring operation(s) for each critical tolerance in-between machining operations. Measurement of each critical tolerance is also planned by the developed system including generating, allocating, and sequencing measurement points for each measuring operation. After the measurement results of each measuring operation are collected, the system analyses the results and provides proper adjustments to the immediate subsequent machining operation(s). A software prototype was developed to test the proposed data model and the integrated process planning and feedback concept. The ultimate goal of performing measurement in a manufacturing system is to gain close control of the machining process based on tolerance requirements and to adjust process errors as they occur. The key issue is to connect machining and tolerance requirements. What to measure and when to measure is another critical issue. This research has made an attempt to address these issues in order to realize a long-awaited paradigm of automatic placement of measurement procedures in-between machining operations and provide automated process-intermittent feedback to the machining process.
3

Nova metodologia para monitoramento dimensional de peças, em processo, utilizando uma retificadora cilíndrica / New methodology for in process workpiece measurement, using a cylindrical grinding

Medalha, Giuliano Cardozo 10 July 2001 (has links)
Atualmente, a maior parte das indústria de manufatura utiliza seus operadores de máquinas para fazer a verificação dimensional das peças usinada. Esses operadores geralmente escolhem algumas amostras aleatoriamente, num determinado período de tempo, para fazer a inspeção manual, ou utilizam dispositivos de medição automáticos no lote todo. Esses procedimentos podem implicar em perda de tempo, ou grandes investimentos, o que eleva os custos do produto final. Este trabalho propõe uma nova metodologia para a medição de peças em processo de retificação, utilizando uma máquina retificadora com funções inteligentes. As tecnologias de um encoder incremental óptico rotacional e de um chip contador são utilizadas para fazer o monitoramento da posição do cabeçote porta rebolo. Utilizando um sistema de cooordenadas baseado no Comando Numérico (CN) da máquina, associado a inspeção por Emissão Acústica (EA) pode-se monitorar a posição do rebolo do ponto de início ciclo de retificação até o início do contato com a peça. Os erros associados a deformação térmica da máquina e o desgaste do rebolo são levados em consideração e compensados. Desta maneira, é possível medir a dimensão e a excentricidade das peças geradas pela operação imediatamente anterior, com uma precisão suficiente. Este sistema pode ajudar na redução do nível de refugo e do tempo total de e produção, criando um diferencial para o aumento da confiabilidade do processo e da automação. / Most of the industries today use their machine operators to make the Workpiece dimensional verification. For this task they generally chose samples, doing manual inspection, or use automatic measuring devices in a whole lot. These procedures can implies in loss of time, a high investment, what may raise the costs of the final product. This work proposes a new methodology for in-process workpiece gagging, using a grinding machine associated with intelligent functions. The technology of an incremental rotational optical encoder and an external counter chip are used to perform the wheel head position monitoring. Using a NC (Numerical Control) coordinate system associated with AE (Acoustic Emission) inspection it was possible to get the position of the grinding wheel from the start of the grinding cycle until the first contact with the workpiece. The errors associated with the grinding machine deformation and wheel wear are considered and compensated. Thus, it is possible to measure the dimension and the run out of the workpiece, generated by a previous operation, with enough precision. This system may help to reduce the scrap leveI and the overall production time, creating a differential for process reliability and automation.
4

Designing a Process Measurement Program as a part of Measurement & Analysis Process Area of CMMI Level 2

Ghalambor, Afrooz, Latifi, Madeleine January 2009 (has links)
This master’s dissertation stands as a guideline for defining a measurement program for GEEE that can be piloted at the Gothenburg site EEEG. The measurement program is based on the “CMMI process area Measurements and Analysis, Level 2”. The proposed measurement program is designed in such a way that is applicable for repeatable process measurement with potential minor alters depending on the nature of the process being examined. Major effort has been made on creating a program that not only collects the numerical data but also delivers substantial results in terms of goal setting, data analysis and decision making. Designing a process for measurement facilitate organizational strategy toward process improvements. This measurement program is designed with the help of some well-known methods such as: GQM (Goal-Question-Metric), PDCA (Plan-Do-Check-Act) and ETVX (Entry-Task-Validation- Exit) where five major phases are resulted, namely; Identify, Define, Collect data, Analysis, Evolve, thereafter embedded in a template-shaped tool. The whole template, after a complete fulfillment, would provide the organization with a guideline to achieve the organizational objectives. It is vital to mention that this template itself does not improve the processes. It only shows the status of the chosen project/process after having the filled template executed. What this template generates is to provide the stakeholders with necessary information and basis to make informed decision afterwards in order to improve the chosen processes/projects. Since the processes in “Maturity Level 2 of CMMI” are project based, it is important the status of processes can be measured and communicated. This procedure plays a crucial role in creating a platform for moving to the next maturity level.
5

Optical Sensor for Measurement of Clad Height during Laser Cladding Process

Asselin, Matthew January 2006 (has links)
The process of laser cladding consists of depositing successive layers of molten metallic powder to create a near-net shape. A high-power laser is used to melt incoming metallic powder, which forms a melt pool on the surface. As the latter moves beneath the laser, this newly created melt pool solidifies. By properly controlling the trajectory of deposition tracks, one can create a diverse range of shapes with varying complexities. However, the process is very sensitive to parameters, requiring constant attention from technicians. This lends itself perfectly to the addition of automatic controllers whereby supervision is minimal. <br /><br /> In this thesis, an optical sensor is developed to monitor the process zone. The sensor will output a measurement of the height of solidified clad, which in turn can be used by a controller to adjust this geometrical feature. The thesis is divided into three main parts, each contributing to the final algorithm. <br /><br /> First, in Chapter 3 an analysis is performed on the light irradiating from the interaction zone (or melt pool). It is stated that the dominating source of light is governed by blackbody radiation from this molten metal. This is confirmed by analyzing a series of images captured through a digital camera, where various narrow bandpass filters were utilized to selectively view a portion of the CCD-sensor's spectrum. This investigation also leads to the selection of bandpass filter such that a stable, relatively intense melt pool is captured through the digital camera's CCD-sensor. <br /><br /> Second, in Chapter 4 the captured images are taken through a pair of image processing techniques, outputting a series of coordinates representating the melt pool's boundary. The image is first analyzed to calculate an optimal threshold level based on the minimization of fuzzy entropy. With this threshold selected, the grayscale image is converted into black-and-white, where the white pixels represent the melt pool. After this step, the melt pool's boundary is extracted through an 8-connectivity border tracing algorithm. This technique outputs a series of coordinates (in pixels) as though one were traveling along the melt pool in a clockwise rotation. <br /><br /> Last, Chapter 5 analyzes these pixel coordinates to extract the melt pool's height. The coordinates are first transformed into real-world coordinates, by use of a perspective transformation. This transformation essentially yields the melt pool's shadow, as created by a light-source coincident with the camera. As a result, the melt pool's height is estimated based upon a right-angle triangle, where the camera's angle is known, and the projected coordinates represent the shadow length (triangle's base). <br /><br /> The result of applying this series of steps to the estimation of clad heights is found at the end of Chapter 5. Results varied dramatically, from 4% error to 393%. Although the errors are large at times, they are mainly caused by a bias in the estimate. That is, the dynamics of the true clad formation are very well predicted by the algorithm, however, shifting by a certain amount. This amount varies both with substrate velocity, and the clad's direction of travel, relative to the camera. A partial explanation is given such that the clad's height is offset from the laser center-point, which is a function of both these parameters. However, the specific relationship requires further experimentation.
6

Optical Sensor for Measurement of Clad Height during Laser Cladding Process

Asselin, Matthew January 2006 (has links)
The process of laser cladding consists of depositing successive layers of molten metallic powder to create a near-net shape. A high-power laser is used to melt incoming metallic powder, which forms a melt pool on the surface. As the latter moves beneath the laser, this newly created melt pool solidifies. By properly controlling the trajectory of deposition tracks, one can create a diverse range of shapes with varying complexities. However, the process is very sensitive to parameters, requiring constant attention from technicians. This lends itself perfectly to the addition of automatic controllers whereby supervision is minimal. <br /><br /> In this thesis, an optical sensor is developed to monitor the process zone. The sensor will output a measurement of the height of solidified clad, which in turn can be used by a controller to adjust this geometrical feature. The thesis is divided into three main parts, each contributing to the final algorithm. <br /><br /> First, in Chapter 3 an analysis is performed on the light irradiating from the interaction zone (or melt pool). It is stated that the dominating source of light is governed by blackbody radiation from this molten metal. This is confirmed by analyzing a series of images captured through a digital camera, where various narrow bandpass filters were utilized to selectively view a portion of the CCD-sensor's spectrum. This investigation also leads to the selection of bandpass filter such that a stable, relatively intense melt pool is captured through the digital camera's CCD-sensor. <br /><br /> Second, in Chapter 4 the captured images are taken through a pair of image processing techniques, outputting a series of coordinates representating the melt pool's boundary. The image is first analyzed to calculate an optimal threshold level based on the minimization of fuzzy entropy. With this threshold selected, the grayscale image is converted into black-and-white, where the white pixels represent the melt pool. After this step, the melt pool's boundary is extracted through an 8-connectivity border tracing algorithm. This technique outputs a series of coordinates (in pixels) as though one were traveling along the melt pool in a clockwise rotation. <br /><br /> Last, Chapter 5 analyzes these pixel coordinates to extract the melt pool's height. The coordinates are first transformed into real-world coordinates, by use of a perspective transformation. This transformation essentially yields the melt pool's shadow, as created by a light-source coincident with the camera. As a result, the melt pool's height is estimated based upon a right-angle triangle, where the camera's angle is known, and the projected coordinates represent the shadow length (triangle's base). <br /><br /> The result of applying this series of steps to the estimation of clad heights is found at the end of Chapter 5. Results varied dramatically, from 4% error to 393%. Although the errors are large at times, they are mainly caused by a bias in the estimate. That is, the dynamics of the true clad formation are very well predicted by the algorithm, however, shifting by a certain amount. This amount varies both with substrate velocity, and the clad's direction of travel, relative to the camera. A partial explanation is given such that the clad's height is offset from the laser center-point, which is a function of both these parameters. However, the specific relationship requires further experimentation.
7

Nova metodologia para monitoramento dimensional de peças, em processo, utilizando uma retificadora cilíndrica / New methodology for in process workpiece measurement, using a cylindrical grinding

Giuliano Cardozo Medalha 10 July 2001 (has links)
Atualmente, a maior parte das indústria de manufatura utiliza seus operadores de máquinas para fazer a verificação dimensional das peças usinada. Esses operadores geralmente escolhem algumas amostras aleatoriamente, num determinado período de tempo, para fazer a inspeção manual, ou utilizam dispositivos de medição automáticos no lote todo. Esses procedimentos podem implicar em perda de tempo, ou grandes investimentos, o que eleva os custos do produto final. Este trabalho propõe uma nova metodologia para a medição de peças em processo de retificação, utilizando uma máquina retificadora com funções inteligentes. As tecnologias de um encoder incremental óptico rotacional e de um chip contador são utilizadas para fazer o monitoramento da posição do cabeçote porta rebolo. Utilizando um sistema de cooordenadas baseado no Comando Numérico (CN) da máquina, associado a inspeção por Emissão Acústica (EA) pode-se monitorar a posição do rebolo do ponto de início ciclo de retificação até o início do contato com a peça. Os erros associados a deformação térmica da máquina e o desgaste do rebolo são levados em consideração e compensados. Desta maneira, é possível medir a dimensão e a excentricidade das peças geradas pela operação imediatamente anterior, com uma precisão suficiente. Este sistema pode ajudar na redução do nível de refugo e do tempo total de e produção, criando um diferencial para o aumento da confiabilidade do processo e da automação. / Most of the industries today use their machine operators to make the Workpiece dimensional verification. For this task they generally chose samples, doing manual inspection, or use automatic measuring devices in a whole lot. These procedures can implies in loss of time, a high investment, what may raise the costs of the final product. This work proposes a new methodology for in-process workpiece gagging, using a grinding machine associated with intelligent functions. The technology of an incremental rotational optical encoder and an external counter chip are used to perform the wheel head position monitoring. Using a NC (Numerical Control) coordinate system associated with AE (Acoustic Emission) inspection it was possible to get the position of the grinding wheel from the start of the grinding cycle until the first contact with the workpiece. The errors associated with the grinding machine deformation and wheel wear are considered and compensated. Thus, it is possible to measure the dimension and the run out of the workpiece, generated by a previous operation, with enough precision. This system may help to reduce the scrap leveI and the overall production time, creating a differential for process reliability and automation.
8

Sens-o-Spheres – Mobile, miniaturisierte Sensorplattform für die ortsungebundene Prozessmessung in wässrigen Lösungen

Lauterbach, Tim, Walther, Thomas, Grösel, Michael, Lenk, Stephan, Gernandt, T., Moll, R., Seidel, F., Brunner, D., Lüke, T., Hedayat, C., Peters, A., Lenk, F. 17 May 2018 (has links) (PDF)
Zur Prozessmessung in Flüssigkeiten wird ein Konzept vorgestellt, das mittels miniaturisierter Sensorkugeln eine ortsveränderliche Aufnahme von Prozessmesssignalen – z. B. der Temperatur – ermöglicht und diese kontinuierlich aus dem Reaktionsvolumen an eine Basisstation überträgt. Das System beinhaltet nicht nur die Miniaturisierung der Messstelle auf einen Kugeldurchmesser von 7,8 mm sondern auch die Abstimmung der Gesamtdichte auf die Prozessbedingungen, um eine gleichmäßige Verteilung der Messpunkte auf das gesamte Reaktionsvolumen zu ermöglichen. Für die Verwendung im Bioprozess wurde eine bio-inerte Kapselung für die gesamte Messelektronik entwickelt und die Funktionstüchtigkeit in mehreren Bioreaktorsystemen demonstriert. Das Messsystem wird mit einer induktiv wieder aufladbaren Energiequelle betrieben und hat eine Reichweite von mehr als 30 cm durch die Flüssigkeitssäule.
9

Maturity m easurement for industrialized house building - A study of VeidekkeMAX / Mognadsmätning inom industriellt husbyggande - En studie av VeidekkeMAX

Ekelund, Hugo January 2016 (has links)
The construction industry is today well known for its way to work in projects where each one is unique and needs its own detail solutions, ways to work and different processes. That means that in the start up phase of each project there has been a need to start all over again since just a fraction of knowledge and solutions pass from one project to another. Companies has been able to work this way due to the fact that lately the interest level has been favourable and the customers has had a buying power which enable construction to be carried out this way. Today the interest is so low that it cannot almost go any lower and the construction industry is therefore forced to find new ways to build houses more efficiently and cheaper to be able to match the market. The answer to this problem was found in the manufacturing industry and the way they work with repeated processes. The construction industry has looked into manufacturing and their ways of working before when they looked at the car industry in the early 20th century but it took about 100 years from that for the industrialized house building that we know today to be born. One of Scandinavia´s largest construction companies Veidekke is currently putting an effort in developing an industrialized house building concept called VeidekkeMAX that consists of three different areas. The three areas are a technical platform, process and an organisation with the purpose to find more effective ways to construct houses without compromising with the final outputs quality. When the work today is carried out with more repeatable process than before it is possible to measure the development of industrialized house building by looking at the maturity of its processes within the company. This study´s aim is to investigate a maturity measurement tool from the manufacturing industry and use it in the construction industry. This study will measure the maturity of the concept VeidekkeMAX and the measurement tool being used is CMM. CMM was developed in the software industry and it measure maturity in five different levels. It is important that the measurement can be repeated so it is possible to see how the development is going. Specific fields within the concept have been chosen for investigation and the empirics for the study has been collected through interviews with employees in the chosen fields. The respondent’s answers have been evaluated and the result is presented in this paper. The result shows that today the maturity in VeidekkeMAX is low since the employees are working in different ways and the observed processes within the company today are individual and varies a lot. The result also shows that it is possible to use CMM within the construction industry but it is as most useful if there are clear processes to measure. This thesis also briefly investigates the question whether it is possible to take standardisation within the construction industry too far and each interviewed was asked for their opinions on where VeidekkeMAX is going. The result showed that within the company there is a fear to take it one step too far which shows the importance to make sure that every employee is on-board with the change and that everyone is motivated to work with the concept and help develop it making it more efficient. / Bostadsbyggbranschen är idag välkänd för sitt sätt att arbeta i projekt där varje projekt är unikt och kräver sina egna detaljlösningar, sätt att arbeta samt processer. Vad det innebär är att man inför varje nytt projekt har varit tvungen att till stora delar återuppfinna hjulet då relativt lite kunskap och lösningar har gått från ett projekt till nästa. Företag har kunnat arbeta på det här viset då ränteläget den senaste tiden har varit gynnsamt och kunderna har haft en köpkraft som möjliggör att producera bostäder på detta vis. Idag är räntan på en så låg nivå att den snart inte kan sjunka lägre och således måste byggbranschen hitta nya sätt att producera bostäder på ett effektivare och billigare sätt för att kunna matcha marknaden. Svaret fanns hos tillverkningsindustrin och hur de arbetar med återupprepande processer. Byggindustrin tittade redan på tidigt 1900-tal hur tillverkningsindustrin arbetar men från det tog dröjde drygt 100 år till innan det industriella husbyggandet, som det ser ut idag, skapades. Ett av Skandinaviens största bygg företag, Veidekke, bedriver i dagsläget en satsning inom det industriella husbyggandet som heter VeidekkeMAX som är ett koncept bestående av i tre olika delar. De tre delarna är en teknisk plattform, process och organisation som alla syftar till att bygga på ett effektivare sätt utan att kompromissa på slutproduktens kvalitet. När arbetet nu sker med flera återupprepande processer så öppnar sig möjligheterna att mäta utvecklingen för det industriella husbyggandet genom att se hur mogna dessa processer hos företaget är. Den här studien syftar till att undersöka huruvida det är möjligt att använda mognadsmätningsverktyg tagna från tillverkningsindustrin och sedan använda inom byggindustrin. Mognadsmätningen i denna studie kommer att ske av VeidekkeMAX och mätverktyget som testas är CMM. CMM kommer ursprungligen från mjukvaruindustrin och processmognaden mäts i fem olika nivåer. Viktigt är att mätningen går att återupprepa kontinuerligt för att på så vis kunna se hur utvecklingen sker. Specifika områden inom konceptet har valts ut för granskning och empirin för att genomföra mätningen samlas in genom intervjuer med anställda inom områdena. Därefter utvärderas deras svar och ett resultat av mätningen redovisas. Resultatet visade att mognaden inom VeidekkeMAX var relativt låg då de anställda arbetar på väldigt olika vis och de processer som observerade till stor del var individuella. Resultatet visar också att det går att använda mätverktyget CMM inom byggindustrin men det når sin största potential om det finns tydligt uppstyrda processer att mäta. Studien går även in på frågan om man kan gå för långt med standardisering inom byggbranschen och varje intervjuad anställd tillfrågades även om deras syn på vart VeidekkeMAX är på väg. Resultatet visar att det finns en rädsla att gå för långt och det belyser vikten av att se till att ha alla anställda med på tåget och se till att varje individ är motiverad till att hjälpa till att utveckla och förbättra satsningen.
10

Sens-o-Spheres – Mobile, miniaturisierte Sensorplattform für die ortsungebundene Prozessmessung in wässrigen Lösungen

Lauterbach, Tim, Walther, Thomas, Grösel, Michael, Lenk, Stephan, Gernandt, T., Moll, R., Seidel, F., Brunner, D., Lüke, T., Hedayat, C., Peters, A., Lenk, F. 17 May 2018 (has links)
Zur Prozessmessung in Flüssigkeiten wird ein Konzept vorgestellt, das mittels miniaturisierter Sensorkugeln eine ortsveränderliche Aufnahme von Prozessmesssignalen – z. B. der Temperatur – ermöglicht und diese kontinuierlich aus dem Reaktionsvolumen an eine Basisstation überträgt. Das System beinhaltet nicht nur die Miniaturisierung der Messstelle auf einen Kugeldurchmesser von 7,8 mm sondern auch die Abstimmung der Gesamtdichte auf die Prozessbedingungen, um eine gleichmäßige Verteilung der Messpunkte auf das gesamte Reaktionsvolumen zu ermöglichen. Für die Verwendung im Bioprozess wurde eine bio-inerte Kapselung für die gesamte Messelektronik entwickelt und die Funktionstüchtigkeit in mehreren Bioreaktorsystemen demonstriert. Das Messsystem wird mit einer induktiv wieder aufladbaren Energiequelle betrieben und hat eine Reichweite von mehr als 30 cm durch die Flüssigkeitssäule.

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