Acquisition and reconstruction of 3D objects for robotic machining

With the evolution of the techniques of acquisition of Three-Dimensional (3D) image it became possible to apply these in more and more areas, as well as to be used for research and hobbyists due to the appearance of low cost 3D scanners. Among the application of 3D acquisitions is the reconstruction of objects, which allows for example to redo or remodel an existing object that is no longer on the market. Another rise tech is industrial robot, that is highly present in the industry and can perform several tasks, even machining activities, and can be applied in more than one type of operation. The purpose of this work is to acquire a 3D scene with low-cost scanners and use this acquisition to create the tool path for roughing a workpiece, using an industrial robot for this machining task. For the acquisition, the Skanect software was used, which had satisfactory results for the work, and the exported file of the acquisition was worked on the MeshLab and Meshmixer software, which were used to obtain only the interest part for the milling process. With the defined work object, it was applied in Computer Aided Manufacturing (CAM) software, Fusion 360, to generate the tool path for thinning in G-code, which was converted by the RoboDK software to robot code, and this also allowed to make simulation of the machining with the desired robot. With the simulation taking place as expected, it was implemented in practice, performing the 3D acquisition machining, thus being able to verify the machining technique used. Furthermore, with the results of acquire, generation of toolpath and machining, was possible to validate the proposed solution and reach a conclusion of possible improvements for this project.Com a evolução das técnicas de aquisição de imagem 3D tornou-se possível aplicá-las em cada vez mais áreas, bem como serem utilizadas por pesquisadores e amadores devido ao surgimento de scanners 3D de baixo custo. Entre as aplicações de aquisições 3D está a reconstrução de objetos, o que permite, por exemplo, refazer ou remodelar um objeto existente que não está mais no mercado. Outra tecnologia em ascensão é o robô industrial, que está muito presente na indústria e pode realizar diversas tarefas, até mesmo atividades de fabrico, e ser aplicado em mais de um tipo de operação. O objetivo deste trabalho é adquirir uma cena 3D com scanners de baixo custo e utilizar esta aquisição para criar o caminho da ferramenta para o desbaste de uma peça, utilizando um robô industrial nesta tarefa de usinagem. Para a aquisição foi utilizado o software Skanect, que obteve resultados satisfatórios para o trabalho, e o arquivo exportado da aquisição foi trabalhado nos softwares MeshLab e Meshmixer, os quais foram utilizados para obter apenas a parte de interesse para o processo de fresagem. Com o objeto de trabalho defino, este foi aplicado em software CAM, Fusion 360, para gerar o caminho de ferramentas para o desbaste em G-code, o qual foi convertido pelo Software RoboDK para código de rôbo, e este também permitiu fazer simulação da maquinação com o rôbo pretendido. Com a simulação ocorrendo de acordo com o esperado, esta foi implementada em prática, realizando a maquinação da aquisição 3D, assim podendo verificar a técnica de maquinação utilizada. Além disso com os resultados de aquisição, geração de toolpath e maquinação, foi possível validar a solução proposta e chegar a uma conclusão de possíveis melhorias para este projeto

Modeling and rendering for development of a virtual bone surgery system

A virtual bone surgery system is developed to provide the potential of a realistic, safe, and controllable environment for surgical education. It can be used for training in orthopedic surgery, as well as for planning and rehearsal of bone surgery procedures...Using the developed system, the user can perform virtual bone surgery by simultaneously seeing bone material removal through a graphic display device, feeling the force via a haptic deice, and hearing the sound of tool-bone interaction --Abstract, page iii

Tooling performance in micro milling: Modelling, simulation and experimental study

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.With the continuing trend towards miniaturization, micro milling plays an increasingly important role in fabrication of freeform and high-accuracy micro parts or components directly and cost-effectively. The technology is in kinematics scaled down from the conventional milling, however, existing knowledge and experiences are limited and comprehensive studies on the micro tooling performance are essential and much needed particularly for the process planning and optimization. The cutting performance of micro tools is largely dependent on the dynamic performance of machine tools, tooling characteristics, work material properties and process conditions, and the latter three aspects will be focused in the study. The state of the art of micro milling technology with respect to the tooling performance has been critically reviewed, together with modelling work for performance prediction as well as metrology and instrumentation for the performance characterization. A novel 3D finite element method taking into account the geometry of a micro tool, including the tool diameter, rake angle, relief angle, cutting edge radius and helix angle, has been proposed for modelling and simulation of the micro milling process. Validation through well-designed micro milling trials demonstrates that the approach is capable of characterizing the milling process effectively. With the support of FEM simulation developed, the tooling geometrical effects, including those from helix angle, rake angle and cutting edge radius with influences on cutting forces, tool stresses, tool temperatures, milling chip formation and temperatures have been comprehensively studied and compared for potential micro tool design and optimization purposes. In an effort to prolong the tool life and enhance the tooling efficiency, DLC and NCD coatings have been deposited on micro end mills by PE-CVD and HF-CVD processes respectively. Corresponding cutting performance of these coated tools have been assessed and compared with those of WC micro tools in both dry and wet cutting conditions so as for better understanding of the coating influence on micro tools. Furthermore, the cutting characteristics of the DLC coated and uncoated tools have been analysed through verified plane-strain simulations. The effects of coating friction coefficient, coating thickness and UCT have been determined and evaluated by design of simulation method. Mechanical, chemical and physical properties of a work material have a direct influence on its micro-machinability. Five most common engineering materials including Al 6061-T6, C101, AISI 1045, 304 and P20, have been experimentally investigated and their micro milling behaviours in terms of the cutting forces, tool wear, surface roughness, and micro-burr formation have been compared and characterized. Feed rate, cutting speed and axial depth of cut constitute the complete set of process variables and they have significant effects on the tooling performance. Fundamental understanding of their influences is essential for production engineers to determine optimum cutting parameters so as to achieve the maximum extension of the tool life. 3D FE-based simulations have been carried out to predict the process variable effects on the cutting forces, tool stresses, tool temperatures as well as micro milling chip formation and temperatures. Furthermore, experimental approach has been adopted for the surface roughness characterization. Suggestions on selecting practical cutting variables have been provided in light of the results obtained. Conclusions with respect to the holistic investigation on the tooling performance in micro milling have been drawn based on the research objectives achieved. Recommendations for future work have been pointed out particularly for further future research in the research area.This study is funded by Brunel University and the UK Technology Strategy Board (TSB)

Robots and tools for remodeling bone

The field of robotic surgery has progressed from small teams of researchers repurposing industrial robots, to a competitive and highly innovative subsection of the medical device industry. Surgical robots allow surgeons to perform tasks with greater ease, accuracy, or safety, and fall under one of four levels of autonomy; active, semi-active, passive, and remote manipulator. The increased accuracy afforded by surgical robots has allowed for cementless hip arthroplasty, improved postoperative alignment following knee arthroplasty, and reduced duration of intraoperative fluoroscopy among other benefits. Cutting of bone has historically used tools such as hand saws and drills, with other elaborate cutting tools now used routinely to remodel bone. Improvements in cutting accuracy and additional options for safety and monitoring during surgery give robotic surgeries some advantages over conventional techniques. This article aims to provide an overview of current robots and tools with a common target tissue of bone, proposes a new process for defining the level of autonomy for a surgical robot, and examines future directions in robotic surgery

Burrs understanding, modeling and optimization during slot milling of aluminium alloys

Nowadays due to global competition, manufacturing industries must provide high quality products on time and within the cost constraints to remain competitive. High quality mechanical parts include those with better surface finish and texture, dimension and form accuracies, reduced tensile residual stress and burr-free. The burr formation is one of the most common and undesirable phenomenon occurring in machining operations, which reduces assembly and machined part quality. Therefore, it is desired to eliminate the burrs or reduce the effort required to remove them. Amongst machining operations, slot milling has a more complex burr formation mechanism with multiple burrs appear in machined part edges with non-uniform dimensions. The ultimate goal of this research work is burr minimization in slot milling operation. To this end, new strategies for understanding, modeling and optimizing burrs during slot milling of aluminum alloys are proposed for improving the part quality and ultimately reducing the non-value added expenses caused by deburring processes. In order to have a better understanding of slot milling burr formation mechanism, multi-level experimental studies and statistical methods are used to determine the effects of machining conditions, tooling and workpiece materials on burrs size (height and thickness) when using dry high speed condition. It was found that optimum setting levels of process parameters to minimize each burr are dissimilar. The analysis of results shows that cutting tool, feed per tooth and depth of cut have certain level of influence on slot milling burrs. However most of the burrs are strongly affected by interaction effects between process parameters that consequently complicate developing burr size prediction models. An analytical model is proposed to predict the thickness of the largest burr during slot milling of ductile materials. The model is based on the geometry of burr formation and continuity of work at the transition from chip formation to burr formation, which also takes into account the effect of the cutting force involved in the machining process. A computational model is also developed to predict the exit up milling side burr thickness based on the use of cutting parameters and material properties such as yield strength and specific cutting force coefficient, which are the only unknown variables in the model. Both analytical and computational models are validated using experimental results obtained during slot milling of 2024-T351 and 6061-T6 aluminium alloys. Machining parameters optimization to minimize the burr size could have a negative impact on other machining performance characteristic, such as surface finish, tool life and material removal rate. Therefore, surface finish is also investigated with burr formation in this research work. For simultaneous multiple responses optimization, a new modification to the application of Taguchi method is suggested by proposing fitness mapping function and desirability index. The proposed modification is validated by simultaneous minimization of surface roughness and thickness of five burrs during slot milling of 6061-T6 aluminium alloy. The optimization results demonstrate the potential and capability of the proposed approach

Emergent properties of microbial activity in heterogeneous soil microenvironments:Different research approaches are slowly converging, yet major challenges remain

Over the last 60 years, soil microbiologists have accumulated a wealth of experimental data showing that the usual bulk, macroscopic parameters used to characterize soils (e.g., granulometry, pH, soil organic matter and biomass contents) provide insufficient information to describe quantitatively the activity of soil microorganisms and some of its outcomes, like the emission of greenhouse gases. Clearly, new, more appropriate macroscopic parameters are needed, which reflect better the spatial heterogeneity of soils at the microscale (i.e., the pore scale). For a long time, spectroscopic and microscopic tools were lacking to quantify processes at that scale, but major technological advances over the last 15 years have made suitable equipment available to researchers. In this context, the objective of the present article is to review progress achieved to date in the significant research program that has ensued. This program can be rationalized as a sequence of steps, namely the quantification and modeling of the physical-, (bio)chemical-, and microbiological properties of soils, the integration of these different perspectives into a unified theory, its upscaling to the macroscopic scale, and, eventually, the development of new approaches to measure macroscopic soil characteristics. At this stage, significant progress has been achieved on the physical front, and to a lesser extent on the (bio)chemical one as well, both in terms of experiments and modeling. In terms of microbial aspects, whereas a lot of work has been devoted to the modeling of bacterial and fungal activity in soils at the pore scale, the appropriateness of model assumptions cannot be readily assessed because relevant experimental data are extremely scarce. For the overall research to move forward, it will be crucial to make sure that research on the microbial components of soil systems does not keep lagging behind the work on the physical and (bio)chemical characteristics. Concerning the subsequent steps in the program, very little integration of the various disciplinary perspectives has occurred so far, and, as a result, researchers have not yet been able to tackle the scaling up to the macroscopic level. Many challenges, some of them daunting, remain on the path ahead