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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.
341

Agentenbasierter Programmassistent zur Verwaltung von NC-Informationen in Produktionssystemen mit Kommunikationsnetzwerken

Dang, Thien Ngon 30 April 2008 (has links) (PDF)
In den letzten Jahren hat sich die rapide Entwicklung der Elektrotechnik ebenso wie die der Softwaretechnologie auf die numerischen Steuerungen in den heutigen CNC-Maschinen groß ausgewirkt. Diese numerischen Steuerungen sind sowohl intelligenter und flexibler als auch mit größerer Internspeicherkapazität ausgerüstet. Dies führt zu einer Änderung der Art und Weise, wie DNC-Systeme zu etablieren sind, besonders solcher, die auf bisher verfügbaren, aber ungleichartigen DNC-Systemen basieren. In einem solch heterogenen DNC-System wird Datenspeicherungsfähigkeit stärker verteilt angeordnet, d.h., sie ist nicht nur in einem zentralen DNC-Server vorhanden, sondern auch in Terminals oder Steuerungen selbst angelagert. Diese Änderung des Archivierungsmittels benötigt neue DNC-Software, die die DNC-Grundfunktionen voll realisiert. Zudem sollte sie auch den neuen spezifischen Softwareanforderungen entsprechen und erlauben, neue Funktionen, z.B. Maschinendatenerfassung, Betriebsdatenerfassung usw., als Module hinzuzufügen. Derzeit wird die Agententechnologie bzw. ein MAS (Multiagentensystem) als ein aussichtsreicher Ansatz angesehen, um die Probleme der heutigen komplexen Softwaresysteme, wie ungleichartige Systemumgebungen und verteilte Strukturen, zu lösen. Die vorliegende Arbeit stellt die Idee zum Aufbau eines heterogenen DNC-Systems und die Konzipierung zur Gestaltung der agentenbasierten DNC-Software vor. Ausgehend von dem vorgestellten Lösungskonzept wird zudem der Programmassistent als erster Modul der agentenbasierten DNC-Software präsentiert. / In the network-based DNC systems and especially heterogeneous DNC systems data get more distributed due to the ability to store not only in the DNC Server but also in the CNC controller or CNC Terminal. This leads a challenge to the DNC software in the implementation of its basic functions. The agent-based DNC software with assistants (ADNC) is suggested to solve the above problem. Its tasks are to collect distributed NC information and transfer data safely as well as performing other extended functions, i.e. NC program generation, machine data collection, production data collection, control machines in system, etc. The present work presented the concept to develop the ADNC and its first prototype. This prototype was developed in a process using a framework of agent-based assistants, called AgentAP. It is applicable on distributed manufacturing data and had been implemented on the agent platform JADE. The module Program Assistant, one of these prototype modules, which is responsible for management, bidirectional transfer, and monitoring change of NC programs, is also discussed.
342

Automated estimation of time and cost for determining optimal machining plans

Van Blarigan, Benjamin 30 July 2012 (has links)
The process of taking a solid model and producing a machined part requires the time and skillset of a range of professionals, and several hours of part review, process planning, and production. Much of this time is spent creating a methodical step-by-step process plan for creating the part from stock. The work presented here is part of a software package that performs automated process planning for a solid model. This software is capable of not only greatly decreasing the planning time for part production, but also give valuable feedback about the part to the designer, as a time and cost associated with manufacturing the part. In order to generate these parameters, we must simulate all aspects of creating the part. Presented here are models that replicate these aspects. For milling, an automatic tool selection method is presented. Given this tooling, another model uses specific information about the part to generate a tool path length. A machining simulation model calculates relevant parameters, and estimates a time for machining given the tool and tool path determined previously. This time value, along with the machining parameters, is used to estimate the wear to the tooling used in the process. Using the machining time and the tool wear a cost for the process can be determined. Other models capture the time of non-machining production times, and all times are combined with billing rates of machines and operators to present an overall cost for machining a feature on a part. If several such features are required to create the part, these models are applied to each feature, until a complete process plan has been created. Further post processing of the process plan is required. Using a list of available machines, this work considers creating the part on all machines, or any combination of these machines. Candidates for creating the part on specific machines are generated and filtered based on time and cost to keep only the best candidates. These candidates can be returned to the user, who can evaluate, and choose, one candidate. Results are presented for several example parts. / text
343

Process Capability in a Computer Integrated Manufacturing Cell

Austin, Andrew 01 May 2014 (has links)
With the rise of automation in traditional manufacturing processes, more companies are beginning to integrate computer integrated manufacturing (CIM) cells on their production floors. Through CIM cell integration, companies have the ability to reduce process time and increase production. One of the problems created with CIM cell automation is caused by the dependency the sequential steps have on one another. Dependency created by the previous step increases the probability that a process error could occur due to previous variation. One way to eliminate this dependency is through the use of an in-process measuring device such as a Renishaw spindle probe used in conjunction with a computer numerical control (CNC) milling machine. Western Kentucky University (WKU) utilizes a CIM cell in the Senator Mitch McConnell Advanced Manufacturing and Robotics laboratory. The laboratory is located in the Architectural and Manufacturing Sciences department and gives students the opportunity to learn how automated systems can be integrated. The CIM cell consists of three Mitsubishi six-axis robots, a Haas Mini-mill, a Haas GT-10 lathe, an AXYZ, Inc. CNC router table, 120 watt laser engraver, an Automated Storage and Retrieval System (ASRS), material handling conveyor, and vision station. The CIM cell functions throughout the curriculum as a means for applied learning and research. The researcher used this CIM cell in order to determine if an in-process measuring device, such as the Renishaw spindle probe, had the ability to affect process capability. The researcher conducted the study to see if an in-process measuring device can be integrated into the CIM cell located in the Senator Mitch McConnell Advanced Manufacturing and Robotics laboratory to eliminate compounding variation. The researcher discovered that through the use of a Renishaw 40-2 spindle probe used in conjunction with a CNC Haas Mini Mill, process capability has the potential to be improved in a CIM cell by accounting for compounding variation present in the process.
344

The p97 ATPase and the Drosophila Proteasome : Protein Unfolding and Regulation

Björk Grimberg, Kristian January 2010 (has links)
For all living systems, there is a requirement to recycle and regulate proteins. In eukaryotic organisms this is accomplished by the proteasome. The p97 ATPase is another highly conserved and essential complex present throughout the eukaryotic cell. In Paper I we utilized UFD fluorescent substrates to address the role of p97 and cofactors in soluble proteasome degradation. Results using RNAi and Drosophila p97 mutants propose p97 to function upstream of the proteasome on cytosolic proteasome targets as an important unfoldase together with its Ufd1/Npl4 cofactors. The results implicate p97 to be important for degradation of proteasome substrates lacking natural extended peptide regions. In Paper II we focused on identifying transcription factors essential for production of proteasomal subunits and associated proteins in Drosophila S2 cells. We utilized an RNA library targeting 993 known or candidate transcription factors and monitored RNAi depleted Drosophila S2 cells expressing the UFD reporter UbG76VGFP. We identified a range of potential candidates and focused on the bZIP transcription factor Cnc-C. RNAi and qrt-PCR experiments implicated Cnc-C to be involved in transcription of proteasomal subunits. In Paper III we applied our knowledge gained from Paper I about p97 dependent substrates and set up a high-throughput microscopy screening method to potentially find inhibitors specifically targeting the p97 proteasomal sub-pathway. Utilizing UFD substrates with and without C-terminal peptide tails we determined if compounds inhibited the core proteasomal machinery or the p97 pathway specifically. Through a primary and secondary round of screening we identified several new compounds inhibiting the ubiquitin-proteasome pathway though none from our initial screening had specificity for p97. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 3: Manuscript.
345

Verfahren zur Minimierung des Einflusses von Störkräften in lagegeregelten Vorschubantrieben

Doenitz, Steffen. Unknown Date (has links)
Techn. Universiẗat, Diss., 2003--Darmstadt.
346

Toolpath and Cutter Orientation Optimization in 5-Axis CNC Machining of Free-form Surfaces Using Flat-end Mills

Luo, Shan 24 December 2015 (has links)
Planning of optimal toolpath, cutter orientation, and feed rate for 5-axis Computer Numerical Control (CNC) machining of curved surfaces using a flat-end mill is a challenging task, although the approach has a great potential for much improved machining efficiency and surface quality of the finished part. This research combines and introduces several key enabling techniques for curved surface machining using 5-axis milling and a flat end cutter to achieve maximum machining efficiency and best surface quality, and to overcome some of the key drawbacks of 5-axis milling machine and flat end cutter use. First, this work proposes an optimal toolpath generation method by machining the curved surface patch-by-patch, considering surface normal variations using a fuzzy clustering technique. This method allows faster CNC machining with reduced slow angular motion of tool rotational axes and reduces sharp cutter orientation changes. The optimal number of surface patches or surface point clusters is determined by minimizing the two rotation motions and simplifying the toolpaths. Secondly, an optimal tool orientation generation method based on the combination of the surface normal method for convex curved surfaces and Euler-Meusnier Sphere (EMS) method for concave curved surfaces without surface gouge in machining has been introduced to achieve the maximum machining efficiency and surface quality. The surface normal based cutter orientation planning method is used to obtain the closest curvature match and longest cutting edge; and the EMS method is applied to obtain the closest curvature match and to avoid local gouging by matching the largest cutter Euler-Meusnier sphere with the smallest Euler-Meusnier sphere of the machined surface at each cutter contact (CC) point. For surfaces with saddle shapes, selection of one of these two tool orientation determination methods is based on the direction of the CNC toolpath relative to the change of surface curvature. A Non-uniform rational basis spline (NURBS) surface with concave, convex, and saddle features is used to demonstrate these newly introduced methods. Thirdly, the tool based and the Tri-dexel workpiece based methods of chip volume and cutting force predictions for flat-end mills in 5-axis CNC machining have been explored for feed rate optimization to achieve the maximum material removal rate. A new approach called local parallel slice method which extends the Alpha Shape method - only for chip geometry and removal volume prediction has been introduced to predict instant cutting forces for dynamic feed rate optimization. The Tri-dexel workpiece model is created to get undeformed chip geometry, chip volume, and cutting forces by determining the intersections of the tool envelope and continuously updating the workpiece during machining. The comparison of these two approaches is made and several machining experiments are conducted to verify the simulation results. At last, the chip ploughing effects that become a more serious problem in micro-machining due to chip thickness not always being larger than the tool edge radius are also considered. It is a challenging task to avoid ploughing effects in micro-milling. A new model of 3D chip geometry is thus developed to calculate chip thickness and ploughing volume in micro 5-axis flat-end milling by considering the minimum chip thickness effects. The research forms the foundation of optimal toolpath, cutter orientation, cutting forces/volume calculations, and ploughing effects in 5-axis CNC machining of curved surfaces using a flat-end mill for further research and direct manufacturing applications. / Graduate / 0548 / luoshan@uvic.ca
347

Process and machine improvements and process condition monitoring for a deep-hole internal milling machine

Wilmot, Wessley January 2017 (has links)
Milling is a widely used cutting process, most commonly applied to machining external surfaces of workpieces. When machining operations are required within hard to reach areas of components, or deep within the bore of components, alternative methods of metal removal are generally employed. Typically when milling at extended reaches, difficulties may increase exponentially when trying to achieve distances several meters into a component. Essentially every topic of the milling process becomes difficult and more convoluted. Firstly to generate a stable cutting condition, and ultimately for an operator to be able to understand the cutting conditions, when all normal senses to interpret the machining stability are removed. The aim for the research is, to enable the operation of high slenderness ratio internal milling operations to become a viable technology, by detailing the measures required, to obtain a stable cutting condition. The process needs to be monitored for degradation of the tooling due to wear, and to prevent catastrophic machine damage from tool breakage or machine component failure. This research addresses the lack of knowledge available for milling with extended reaches, and the knowledge gained to overcome the real difficulties that exist for this process. Initial experiments are conducted on a prototype machine to gain experience of the internal machining operation and the many issues that it faced. Establishing requirements of the process via investigation of the tooling and necessary auxiliary equipment, it becomes possible to consider countermeasures to address the errors generated by torsional twisting of the milling arm. A system for applying a counter torque to reduce torsional deflection errors has been employed to successfully reduce the unavoidable issue over such long distances. For the process to become manageable for an industrial operator without a high level of specialist knowledge, the application of tool condition monitoring (TCM) and process condition monitoring (PCM) had to be applied. This addresses a void in available literature and research with respect to internal machining, and enables the process to become practical for an industrial environment. For this reason the research project will concentrate on the application of TCM and PCM onto the machining system. The completion of the research resulted in the process becoming satisfyingly stable, and with a resulting accuracy that satisfies the requirements of the component. Performance of the final system rivalled or achieved better results than had been experienced by the project sponsor.
348

Uso de usinagem por jato de água, usinagem por controle numérico computadorizado e corte a laser no design de superfícies tácteis a partir de padrões modulares encaixáveis em ágata e cedro

Silveira, Flávia Lopes da January 2011 (has links)
Este trabalho tem por objetivo o design e a fabricação de superfícies tácteis a partir de padrões modulares encaixáveis. Estas superfícies foram construídas em diferentes materiais naturais (minerais e madeiras) e em distintos processos de fabricação inovadores (usinagem por jato de água, usinagem por controle numérico computadorizado ou CNC e corte a laser). A intenção foi desenvolver uma metodologia de design & tecnologia para aplicá-la em painéis de revestimento que possam ser produzidos em baixa escala de forma semi-industrial. A grande variedade de materiais naturais encontrados no estado do Rio Grande do Sul; a carência de design associado a estes materiais quando do produto final e o volume de rejeitos oriundos deste beneficiamento, foram os principais motivadores para a utilização destas matérias primas. O estudo de diferentes técnicas de design de superfície auxilia na transformação destes materiais, para que os mesmos passem a ter o formato de módulo. Dentro deste contexto, foram estudadas as técnicas desenvolvidas pelo artista Maurits Cornelis Escher. Ele dedicou boa parte de sua vida profissional à composição de desenhos que, justamente, partem da utilização da simetria, modularidade, continuidade e encaixe. Neste sentido, após a compreensão das técnicas utilizadas por Escher, alguns de seus desenhos foram aplicados nos materiais selecionados através dos processos de fabricação adequados, possibilitando a construção das diferentes superfícies tácteis. Os resultados obtidos identificam que a utilização de processos de fabricação inovadores para interferência nos materiais naturais são ferramentas importantes para a promoção de uma nova geração de produtos locais. Conclui-se que estas interferências viabilizam a fabricação de produtos com maior valor estético, social e econômico. / This work aims at the design and the manufacturing of tactile surfaces from modular plug patterns. These surfaces were built in different natural materials (mineral and wood) and in distinct innovative manufacturing processes (waterjet machining, computerized numerical control machining or CNC and laser cutting). The objective was to develop a design & technology methodology for applying it in coating panels that can be produced on a semiindustrial small scale. The huge variety of natural materials found in Rio Grande do Sul State, the lack of design associated to these materials as to the final product and the volume of waste from this processing were the main motivators for the use of these raw materials. The study of these different techniques of surface design helps the transformation of these materials in order that they start to have the modular format. Within this context, the techniques developed by the artist Maurits Cornelis Escher were studied. He devoted much of his professional life to the composition of drawings beginning exactly with the use of symmetry, modularity continuity and joint. In this sense, after understanding the techniques used by Escher, some of his drawings were applied in the materials selected through suitable manufacturing processes, enabling the construction of different tactile surfaces. The results obtained identify that the utilization of innovative manufacturing processes to interfere in the natural materials are important tools for the promotion of a new generation of local products. It is conclude that these interferences enable the manufacture of products with greater aesthetic, social and economic value.
349

Uso de usinagem por jato de água, usinagem por controle numérico computadorizado e corte a laser no design de superfícies tácteis a partir de padrões modulares encaixáveis em ágata e cedro

Silveira, Flávia Lopes da January 2011 (has links)
Este trabalho tem por objetivo o design e a fabricação de superfícies tácteis a partir de padrões modulares encaixáveis. Estas superfícies foram construídas em diferentes materiais naturais (minerais e madeiras) e em distintos processos de fabricação inovadores (usinagem por jato de água, usinagem por controle numérico computadorizado ou CNC e corte a laser). A intenção foi desenvolver uma metodologia de design & tecnologia para aplicá-la em painéis de revestimento que possam ser produzidos em baixa escala de forma semi-industrial. A grande variedade de materiais naturais encontrados no estado do Rio Grande do Sul; a carência de design associado a estes materiais quando do produto final e o volume de rejeitos oriundos deste beneficiamento, foram os principais motivadores para a utilização destas matérias primas. O estudo de diferentes técnicas de design de superfície auxilia na transformação destes materiais, para que os mesmos passem a ter o formato de módulo. Dentro deste contexto, foram estudadas as técnicas desenvolvidas pelo artista Maurits Cornelis Escher. Ele dedicou boa parte de sua vida profissional à composição de desenhos que, justamente, partem da utilização da simetria, modularidade, continuidade e encaixe. Neste sentido, após a compreensão das técnicas utilizadas por Escher, alguns de seus desenhos foram aplicados nos materiais selecionados através dos processos de fabricação adequados, possibilitando a construção das diferentes superfícies tácteis. Os resultados obtidos identificam que a utilização de processos de fabricação inovadores para interferência nos materiais naturais são ferramentas importantes para a promoção de uma nova geração de produtos locais. Conclui-se que estas interferências viabilizam a fabricação de produtos com maior valor estético, social e econômico. / This work aims at the design and the manufacturing of tactile surfaces from modular plug patterns. These surfaces were built in different natural materials (mineral and wood) and in distinct innovative manufacturing processes (waterjet machining, computerized numerical control machining or CNC and laser cutting). The objective was to develop a design & technology methodology for applying it in coating panels that can be produced on a semiindustrial small scale. The huge variety of natural materials found in Rio Grande do Sul State, the lack of design associated to these materials as to the final product and the volume of waste from this processing were the main motivators for the use of these raw materials. The study of these different techniques of surface design helps the transformation of these materials in order that they start to have the modular format. Within this context, the techniques developed by the artist Maurits Cornelis Escher were studied. He devoted much of his professional life to the composition of drawings beginning exactly with the use of symmetry, modularity continuity and joint. In this sense, after understanding the techniques used by Escher, some of his drawings were applied in the materials selected through suitable manufacturing processes, enabling the construction of different tactile surfaces. The results obtained identify that the utilization of innovative manufacturing processes to interfere in the natural materials are important tools for the promotion of a new generation of local products. It is conclude that these interferences enable the manufacture of products with greater aesthetic, social and economic value.
350

Modelagem numérica e experimental dos erros térmicos de um centro de usinagem CNC 5 eixos. / Numerical and experimental modeling of thermal errors in a five-axis CNC machining center.

Marcelo Otávio dos Santos 12 July 2018 (has links)
Esta tese teve por objetivo desenvolver um algoritmo preciso e robusto capaz de compensar os erros térmicos volumétricos de um centro de usinagem 5 eixos em diferentes condições operacionais. O comportamento térmico da máquina foi modelado usando técnicas do método dos elementos finitos (MEF) com base na teoria do calor de atrito e calor de convecção, e validadas através dos vários campos de temperatura obtidos experimentalmente usando termopares e imagens térmicas. Os principais subsistemas da máquina foram inicialmente modelados, como o conjunto de fusos de esferas, guias lineares e motofuso, o que permitiu posteriormente a validação do comportamento termoelástico da máquina completa para onze ciclos de trabalho em vazio, seis ciclos de usinagem, nove ciclos de posicionamento e dois ciclos com temperatura ambiente variando, obtendo erros máximos inferiores a 9%, ao comparar os resultados numéricos com os resultados experimentais. A validação do modelo em elementos finitos permitiu usar os resultados obtidos para treinar e validar uma rede neural artificial (RNA) para prever os erros térmicos do centro de usinagem. Os desvios entre os erros térmicos previstos pela RNA e os calculados pelo MEF foram inferiores a 5%. Baseado nos resultados obtidos pelas medições das peças de trabalho usinadas foi possível formular e implementar um modelo de compensação dos erros térmicos no CNC do centro de usinagem, que obteve uma redução dos erros entre 62% e 100% nas peças usinadas com compensação. Foi também proposto um algoritmo de previsão e compensação dos erros térmicos para o centro de usinagem, baseado em todos os ciclos e simulações realizadas, e que se comparando com os resultados experimentais mostrou-se capaz de reduzir os erros térmicos entre 50% e 95%. Após sua validação, foi possível concluir que o algoritmo desenvolvido é uma ferramenta precisa e robusta para compensar os erros térmicos da máquina para várias condições de trabalho, podendo compensá-los mesmo com esta movendo-se a diferentes velocidades, em usinagem ou mesmo operando em temperatura ambiente variável. / This thesis aims to develop an accurate and robust algorithm capable of compensating the volumetric thermal errors of a 5-axis machining center under different operating conditions. The thermal behavior of the machine was first modeled using finite element method (FEM) techniques based on theory of friction heat and convection heat, and validated with the various experimentally raised temperature fields using thermocouples and thermal imaging. The main machine subsystems were initially modeled, such as the ball screw system, linear guides and spindle, which allowed for validating of the thermoelastic behavior of the entire machine for eleven no load duty cycles, six cycles of machining, nine cycles of positioning and two cycles with varying ambient temperature, obtaining errors lower than 9%, when comparing the numerical results with the experimental results. The validation of the finite element model allowed for the use of the results obtained to train and validate an artificial neural network (ANN) for predicting the thermal errors of the machining center. The deviations between the thermal errors predicted by ANN and the FEM simulation results were less than 5%. Based on the results obtained by the measurements of the machined workpieces, it was possible to formulate and implement a model of compensation of the thermal errors in the CNC of the machining center, which obtained a reduction of errors of 62% and 100% of the machined parts with compensation. It was also proposed a thermal error prediction and compensation algorithm for the machining center, based on all cycles and simulations performed, and that, comparing with the experimental results, it was able to reduce the thermal errors between 50% and 95%. After its validation, it was possible to conclude that the developed algorithm is an accurate and robust tool to compensate the thermal errors of the machine for various duty conditions, being able to compensate the errors even when it is moving at different speeds, in machining process or even operating in variable ambient temperature.

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