The formation of burrs in Machining Operations occurs by three Basic Mechanisms: 1) Lateral Extrusion of material 2) Bending of the chip 3) Tearing of the chip form the workpiece Each of these mechanisms has been studied analytically and compared to experimental results. The agreement between predictions and measurements has been found to be close. Drilling, milling, grinding, and turning burrs were produced in 303Se stainless steel and their properties were related to tool geometry, feedrates, and depth of cut. One thousand measurements were made and subsequently analyzed by analysis of variance techniques. The properties measured include burr length and thickness. Both the theory and the empirical results indicate that burrs cannot be prevented by changing machine variables. Burr size can be minimized, however, by appropriate machining conditions.

During the drilling process, sharp edges of material called burrs are produced and protrude from the original surface. When a through-hole is drilled, burrs form on both the entry and exit surfaces around the hole, requiring expensive deburring operations to be performed in order to meet part specifications. A common hole producing operation in aircraft assembly is drilling holes through multiple sheet metal layers in order to fasten them together. However, at the interface between two layers, burrs form on both the exit of the first layer (termed "skin") and entry of the second layer (termed "frame"). Consequently, the layers frequently need to be taken apart, deburred, and put back together again before being fastened, resulting in additional costs and increased assembly time. The goal of this thesis was to understand the role of key factors such as drill geometry, drill wear and clamping conditions on burr formation at the interface of two thin sheets of 2024-T3 aluminum so that interlayer burr formation could be minimized. This problem was approached from three different angles. First, an experimental study was performed to find the drill geometry parameters for minimization of interlayer burrs and to ascertain the relationship between the average burr size and drill wear. Next, a new kind of clamping system for holding sheet metal layers together during drilling was designed, prototyped, and tested for its effectiveness. Finally, a preliminary analytical model of interlayer burr formation was created in order to better understand the burr formation process in stacked layers of sheet metal and to better understand the effect that each drilling parameter has on the resulting burr size.

En av de mest oönskade bieffekterna vid metallbearbetning är att det blidas grader. Grader kan definieras som plastiskt deformerat material som bildas på en produkts kanter och hörn. De uppstår oftast vid skär- och skjuvande operationer och kan bero på många olika faktorer. Verktygshastighet, skärpa på verktyget och materialvariationer för att nämna några. Dessa grader kan påverka en produkts egenskaper negativt i många avseenden. Att avlägsna dessa grader är både kostsamt, tidskrävande och ett slitsamt monotont arbete. Side Systems AB i Oviken tillverkar ventilblock i aluminium 2007/2033, Automatstål 11SMnPb30 och Segjärn 500–7 och lägger i dagsläget stora resurser på att avlägsna grader. Därför finns en efterfrågan från företaget i att minska denna kostnad och undersöka om det med en vakuumgradningsmaskin EDS-900 går att avlägsna grader på ett effektivt sätt. En bieffekt av vakuumgradning kan vara att Ra-värdet förändras. I detta projekt undersöktes hur olika medier (granulat) hanterade uppgiften att avlägsna grader och hur de förändrade ytjämnheten. Detta utfördes genom mätningar av Ra före och efter gradningsprocessen och genom visuell undersökning av grader i färdigbehandlade produkter. Detta gjordes på ett urval av olika medier och material för att påvisa hur de faktorerna påverkar den slutgiltiga produkten och dess ytjämnhet. Denna undersökning visade att granulat med glaskulor med storlek 90–150 μm påverkade ytjämnheten för aluminium 2007, Automatstål 11SMnPb30 så att Ra-värdet låg under det av Side Systems ställda gränsvärde på 1,6. För segjärn 500–7 uppfyllde inga granulat de ställda kraven. Resultatet av denna undersökning visar även att granulat med glaskulor och storleken 90–150 µm avlägsnar grader på ventilblock tillverkade i aluminium 2007. För resultat på automatstål 11SMnPb30 och segjärn 500–7 behövs vidare studier. Som slutsats kan arbetet användas som underlag för inköp. / One of the most undesirable side effects in metal processing is the formation of burrs. Burrs can be defined as plastic deformations that occur on the edges and corners of a product. They are most commonly generated during cutting and shearing operations and can be attributed to various factors, such as tool speed, sharpness, and material variations, among others. These burrs can have negative implications on the properties of a product in multiple ways. The removal of these burrs is both costly and time-consuming, requiring tedious and labor-intensive work. Side Systems AB in Oviken manufactures valve blocks using Aluminum 2007/2033, Automaton Steel 11SMnPb30, and Cast Iron 500–7 and currently invests significant resources in burr removal. Therefore, there is a request from the company to reduce this cost and investigate whether it is possible to effectively remove burrs using a vacuum deburring machine EDS-900. One side effect of vacuum deburring may be a change in the Ra value. This project aimed to examine how different media (granules) handled the task of removing burrs and how they affected the surface finish. This was achieved through measurements of Ra before and after the deburring process and through visual inspection of burrs in finished products. This was carried out on a selection of different media and materials to demonstrate how these factors impact the final product and its surface finish. This study revealed that granules with glass beads sized 90–150 μm had an impact on the surface smoothness of Aluminum 2007 and Automaton Steel 11SMnPb30, resulting in Ra values below the threshold set by Side Systems at 1.6. For Cast Iron 500–7, none of the tested granules met the specified requirements. However, it should be noted that the aforementioned granules were not examined specifically on cast Iron in this study. This investigation demonstrated that granules with glass beads sized 90–150 µm affected the surface smoothness of Aluminum 2007 and Automaton Steel 11SMnPb30, resulting in Ra values below the specified threshold of 1.6 set by Side Systems. However, none of the tested granules met the requirements for Cast Iron 500–7. The results of this investigation also indicated that granules with glass beads, sized 90–150 µm, effectively remove burrs on valve blocks manufactured in Aluminum 2007. Further studies are required to assess the results for Automaton Steel 11SMnPb30 and Cast Iron 500–7. The conclusion of the work can be used as a basis for procurement. / <p>Betygsdatum 2023-06-28</p>

A micromanufatura via usinagem apresenta algumas dificuldades, principalmente aquelas relacionadas à formação do cavaco, pois a espessura de corte passa a ter a dimensão do tamanho de grão do material da peça e da microgeometria da aresta de corte. Em operações de microcorte, a microestrutura do material é um fator importante no controle da geração da superfície da peça, mecanismo de formação de cavaco, etc. Este trabalho de pesquisa avaliou o efeito do tamanho ultrafino dos grãos do material da peça sobre os fenômenos inerentes ao corte no microfresamento. As variáveis de usinagem investigadas foram avanço por dente (fz), velocidade de corte (vc), diâmetro da microfresa (d&#934) e raio de aresta de corte (re), visando avaliar o mecanismo de formação do cavaco, acabamento da peça e integridade superficial. Os materiais utilizados nos experimentos foram um aço bifásico (ferrita-perlita) com tamanho de grão ferrítico de 11 µm e outro de microestrutura homogênea de grãos ultrafinos com 0,7 µm, ambos com mesma composição química e baixo-carbono. Dois grupos de ensaios foram propostos: (1) macro e microfresamento e (2) microfresamento de canais. O tipo de usinagem foi o de fresamento de topo, sem emprego de fluido de corte. Os ensaios de usinagem foram executados em centros de usinagem CNC. As ferramentas de corte foram de metal duro com recobrimentos, diâmetro 16 mm na escala macro de usinagem, 200 e 800 µm na escala micro. A adequação da microestrutura do material da peça à redução da escala de usinagem, através do mecanismo de refino de grão, gerou alguns aspectos favoráveis à microusinagem, como melhor acabamento (Ssk&#8776;0 e Sku&#8776;3), formação de cavaco contínuo e menor formação de rebarbas com a redução da espessura de corte (fz&#8804re), possibilitando aplicações em microfabricação por corte com ferramenta de geometria definida utilizando aços baixo carbono, antes limitadas à estruturas na construção civil e peças obtidas por conformação mecânica. / Micro manufacturing by means of machining presents difficulties, mainly those related to chip formation, since chip thickness become as small as normal material grain size, as well as the cutting edge radius. At such micro cutting operations material microstructure ascends as a very important issue in terms of machining output, i.e. surface roughness, subsurface damages, cutting forces, etc. This research evaluated the effect of the intervention on the metallurgical microstructure of the material on the cutting phenomena inherent in micromachining. The variables investigated were the feed per tooth (ft), cutting speed (vc), micro end-mill diameter (d&#934) and cutting edge radius (re). The materials used in the experiments were a steel two-phase (ferrite-pearlite) with ferritic grain size of 11 µm and similar one with homogeneous microstructure and ultrafine grains (0.7 µm), both low carbon. The mechanism of chip formation, surface finish and surface integrity were investigated and correlated with the studied variables. Two groups of machining experiments were proposed: (1) macro and micro end-milling and (2) microchannels. Overall, the type of machining was the end milling, without using cutting fluid. The machining tests were carried on a CNC machining center. The cutting tools are coated, diameter 16 mm in macro scale of machining, 200 and 800 &#956m in micro scale. the adequacy of the microstructure of the workpiece material to the reduce the scale of machining generated some favorable aspects to micromachining, such as better finishing (Ssk&#8776;0 e Sku&#8776;3), continuous chip formation and lesser burr formation by reducing the cutting thickness (fz&#8804re), enabling micromanufacturing applications for low carbon steels, once limited to structures in the civil construction and pieces obtained by mechanical forming.

A micromanufatura via usinagem apresenta algumas dificuldades, principalmente aquelas relacionadas à formação do cavaco, pois a espessura de corte passa a ter a dimensão do tamanho de grão do material da peça e da microgeometria da aresta de corte. Em operações de microcorte, a microestrutura do material é um fator importante no controle da geração da superfície da peça, mecanismo de formação de cavaco, etc. Este trabalho de pesquisa avaliou o efeito do tamanho ultrafino dos grãos do material da peça sobre os fenômenos inerentes ao corte no microfresamento. As variáveis de usinagem investigadas foram avanço por dente (fz), velocidade de corte (vc), diâmetro da microfresa (d&#934) e raio de aresta de corte (re), visando avaliar o mecanismo de formação do cavaco, acabamento da peça e integridade superficial. Os materiais utilizados nos experimentos foram um aço bifásico (ferrita-perlita) com tamanho de grão ferrítico de 11 µm e outro de microestrutura homogênea de grãos ultrafinos com 0,7 µm, ambos com mesma composição química e baixo-carbono. Dois grupos de ensaios foram propostos: (1) macro e microfresamento e (2) microfresamento de canais. O tipo de usinagem foi o de fresamento de topo, sem emprego de fluido de corte. Os ensaios de usinagem foram executados em centros de usinagem CNC. As ferramentas de corte foram de metal duro com recobrimentos, diâmetro 16 mm na escala macro de usinagem, 200 e 800 µm na escala micro. A adequação da microestrutura do material da peça à redução da escala de usinagem, através do mecanismo de refino de grão, gerou alguns aspectos favoráveis à microusinagem, como melhor acabamento (Ssk&#8776;0 e Sku&#8776;3), formação de cavaco contínuo e menor formação de rebarbas com a redução da espessura de corte (fz&#8804re), possibilitando aplicações em microfabricação por corte com ferramenta de geometria definida utilizando aços baixo carbono, antes limitadas à estruturas na construção civil e peças obtidas por conformação mecânica. / Micro manufacturing by means of machining presents difficulties, mainly those related to chip formation, since chip thickness become as small as normal material grain size, as well as the cutting edge radius. At such micro cutting operations material microstructure ascends as a very important issue in terms of machining output, i.e. surface roughness, subsurface damages, cutting forces, etc. This research evaluated the effect of the intervention on the metallurgical microstructure of the material on the cutting phenomena inherent in micromachining. The variables investigated were the feed per tooth (ft), cutting speed (vc), micro end-mill diameter (d&#934) and cutting edge radius (re). The materials used in the experiments were a steel two-phase (ferrite-pearlite) with ferritic grain size of 11 µm and similar one with homogeneous microstructure and ultrafine grains (0.7 µm), both low carbon. The mechanism of chip formation, surface finish and surface integrity were investigated and correlated with the studied variables. Two groups of machining experiments were proposed: (1) macro and micro end-milling and (2) microchannels. Overall, the type of machining was the end milling, without using cutting fluid. The machining tests were carried on a CNC machining center. The cutting tools are coated, diameter 16 mm in macro scale of machining, 200 and 800 &#956m in micro scale. the adequacy of the microstructure of the workpiece material to the reduce the scale of machining generated some favorable aspects to micromachining, such as better finishing (Ssk&#8776;0 e Sku&#8776;3), continuous chip formation and lesser burr formation by reducing the cutting thickness (fz&#8804re), enabling micromanufacturing applications for low carbon steels, once limited to structures in the civil construction and pieces obtained by mechanical forming.