Micromachining – Review of Literature from 1980 to 2010

Trend of miniaturization of products and consequently its components nowadays can be evident in almost every production field. To accomplish requirements imposed by miniaturization micromachining proved to be a satisfied manufacturing technique. Herein the term micromachining refers to mechanical micro cutting techniques where material is removed by geometrically determined cutting edges. The aim of this review article is to summarize existing knowledge and highlight current challenges, restrictions and advantages in the field of micromachining

Multi-response optimization of CuZn39Pb3 brass alloy turning by implementing Grey Wolf algorithm

Machinability of engineering materials is crucial for industrial manufacturing processes since it affects all the essential aspects involved, e.g. work­load, resources, surface integrity and part quality. Two basic ma­chin­ability para­meters are the surface roughness, closely associated with the functional and tribological performance of components, and the cutting forces acting on the tool. Knowledge of the cutting forces is needed for estimation of power re­quirements and for the design of machine tool elements, tool-holders and fix­tures, adequately rigid and free from vibration. This work in­ve­stigates the in­flu­ence of cutting conditions on machinability indicators such as the main cutting force Fc and surface roughness parameters Ra and Rt when longitudinally turning CuZn39Pb3 brass alloy. Full quadratic regression models were de­veloped to correlate the machining conditions with the imparted machinability characteristics. Further on, an advanced artificial grey wolf optimization algorithm was implemented to optimize the aforementioned responses with great success in finding the final optimal values of the turning parameters

硬質粒子被膜を有する高機能タップ工具の開発

Tohoku University堀切川一男課

Surface integrity in metal machining - Part I: Fundamentals of surface characteristics and formation mechanisms

The surface integrity of machined metal components is critical to their in-service functionality, longevity and overall performance. Surface defects induced by machining operations vary from the nano to macro scale, which cause microstructural, mechanical and chemical effects. Hence, they require advanced evaluation and post processing techniques. While surface integrity varies significantly across the range of machining processes, this paper explores the state-of-the-art of surface integrity research with an emphasis on their governing mechanisms and emerging evaluation approaches. In this review, removal mechanisms are grouped by their primary energy transfer mechanisms; mechanical, thermal and chemical based. Accordingly, the resultant multi-scale phenomena associated with metal machining are analyzed. The contribution of these material removal mechanisms to the workpiece surfaces/subsurface characteristics is reviewed. Post-processing options for the mitigation of induced surface defects are also discussed

Cutting Force Modelling for Drilling of Fiber-Reinforced Composites

Although used in a very large variety of applications, drilling is one of the most complex and least understood manufacturing processes. Most of the research on drilling was done in the field of metal cutting for mechanical parts since, in this case, high precision and quality are needed. The use of composite materials in engineering applications has increased in recent years, and in many of these applications drilling is one of the most critical stages in the manufacturing process. This is because it is among the last operations in the manufacturing plan of composite parts. Delamination and extensive tool wear are among the problems which drilling of composite materials are currently facing. A major difference between metallic and composite plates is their structure: isotropic for metals and anisotropic for composite materials; meaning that while for metallic materials all the structure will respond in a similar manner under the machining loads, the composite structure will have localized responses from the same loads, leading to defects in the internal structure of the remaining work-piece material (i.e. delamination). Delamination can lead to failure in use and parts with such defects are usually discarded. Delamination is not usually visually detectable and special testing is necessary, affecting the costs of the final parts. Delamination during drilling was found to occur at tool entry (peel-up) or tool exit (push-out) and depends on the loads at inter-laminar level. The work presented in the current thesis focuses in providing reliable information about the thrust and torque distribution along the drill radius (and work-piece thickness) during drilling for varying cutting parameters, drill geometry and work-piece material. Such data should assist in the development of delamination models capable of capturing the influence of the drill geometry and cutting parameters on delamination onset and propagation during both exit and entry of the drill in the work-piece. A cutting force model is proposed to obtain the elementary cutting force distribution along the drill radius which is able to account for changes in axial feed rate and drill geometry. Based on oblique cutting, forces are considered on both rake and relief faces. A generic relationship in the form of a transformation matrix is developed to relate oblique cutting to drilling, valid for any drill geometry. The mathematical description of the drill geometry in the scope of cutting force modeling has been revised. The kinematics of the drilling process is now taken into account for (i) all geometrical parameters of the drill and for (ii) the elementary cutting forces decomposition. Additionally, a new drill type and its geometric features have been described mathematically and the definition of the geometrical parameters has been generalized so that other drills types or variations could be easily implemented into the model. It proved therefore possible to adopt simpler expressions for the empirical force coefficients of the cutting force model. Up to four empirical coefficients are used, which are calculated from experiments for each work-piece material and drill type. Most experimental investigations on drilling fiber reinforced composites analyze only the total thrust and torque generated during drilling or separately the forces caused by the chisel edge and cutting lips by drilling with or without a pilot hole. The later type of analysis suggested that is possible to obtain more detailed information about the distribution of the loads in drilling from the analysis of the forces variation during tool entry into the work-piece. Pursuing this direction, an experimental analysis method is proposed to obtain the axial and tangential elementary cutting force distribution along the tool radius or work-piece thickness. The cutting force distribution obtained experimentally was used to calibrate the cutting force model, rather than the total thrust and torque. The experimentally obtained cutting force distribution can also be used alone for analyzing the drilling process (i.e. the loads distribution among the plies of the composite laminate and how this load is influenced by changes in the drill geometry and the cutting conditions)

Design and manufacture of a taper thermosyphon drill for dry drilling operations

Abstract: Previous studies have indicated that the use of metal working fluids is harmful and poses health risks, also indicating that they are increasingly expensive. There is a drive to look for more environmentally friendly methods of machining, one such being the option of removing the need to use metal working fluids to cool off drill bits. There are studies which have highlighted the option of dry drilling without use of metal working fluids. Dry drilling has been researched and methods such as the minimal use of cutting fluid have proved to reduce the temperature of the drill bit during drilling to a certain extent when compared to the full use of metal working fluid. Dry drilling introduces options which include the use of a thermosiphon for reducing temperature of the drill bit tip, during drilling operations. The use of thermosiphons has been proved to be the most effective in cooling drill bits for dry drilling. This study focused on the design, manufacturing and testing of a reverse tapered thermosiphon, which is efficient for evaporation and condensation within a drill bit for dry drilling operations. The methodology consisted of a virtual design and a stress analysis conducted on the reverse tapered thermosyphon through the use of SolidWorks software. The stress analysis conducted on the drill bit demonstrated optimal positions of the largest diameter of the taper thermosyphon and distance from the cutting edge...M.Phil. (Mechanical Engineering

Machining Fibre Metal Laminates and Al2024-T3 aluminium alloy

The present thesis investigates the machining performance of an aerospace structural material commercially known as GLARE fibre metal laminate and its metal constituent aluminium Al2024-T3 aerospace alloy using commercially available solid carbide twist drills. The objective is to quantify the effects of the cutting parameters and two modern coolant technologies on cutting forces and a number of hole quality parameters. The generated drilling cutting forces, quality of machined hole and drilling-induced damage and defects when drilling GLARE fibre metal laminates were experimentally studied. Drilling-induced defects and damage investigated were surface roughness, burr formation at both sides of the workpiece and interlayer burr, hole size and circularity error, chip formation as well as damage described at the macro level (delamination area) using computerised tomography (CT) scan, and at the micro level (fibre matrix debonding, chipping, adhesions, cracks) using scanning electron microscopy (SEM). The experimental results have been statistically analysed using full factorial and response surface methodology statistical techniques to generate multiple regression models which makes it attractive as an indirect tool predicting the machining outputs prior the start of actual tests. Moreover, the analysis of variance (ANOVA) was employed to determine the percentage contribution of drilling parameters on cutting forces and hole quality outputs. The results indicated that the presence of coolant during the drilling process of GLARE could significantly improve hole quality. The use of cryogenic liquid nitrogen was found to eliminate the formation of waste on the borehole surface and burr formation at the hole exit. Using minimum quantity lubrication coolant was found to reduce the workpeice temperature compared to dry drilling at room temperature. Both coolants reduced the surface roughness compared to dry drilling but increased the cutting forces especially when using cryogenic liquid nitrogen. The cutting parameters results indicated that a maximum operating feed rate of 300 mm/min and a maximum spindle speed of 6000 rpm is recommended for superior hole quality results. Moreover, drilling at or below those levels of cutting parameters did not lead to severe delamination or fibre pull outs in the laminate compared to the higher cutting parameters used in the study. In addition, the fibre orientation and workpiece thickness were found to play a significant role on surface roughness and hole size but did not have a considerable impact on cutting forces due to the small thickness of glass fibre layers in the laminate. Adhesion and built up edge was found to be the main wear mechanism when drilling monolithic aluminium alloy, while adhesion and abrasion of the primary and secondary facets of the drill were identified to be the main wear process that occurs in drilling GLARE laminates

Machinability aspects of heat-treated Al-(6-11)%Si cast alloys : role of intermetallics and free-cutting elements

Le besoin de combler le vide entre les procédés de coulé et d'usinage donne de bonnes raisons d'examiner les nombreux aspects affectant l'usinabilité des alliages de fonderie Al-Si. Les alliages quasi-eutectiques sont, parmi les alliages Al-Si, les plus difficiles à usiner, puisque les particules de la phase Si sont environ 10 fois plus dures que la matrice d'aluminium, lesquelles expliquent pourquoi les outils de coupe s'usent prématurément. Toutes ces difficultés nécessitent une meilleure compréhension des effets de la microstructure sur l'usinabilité de ces alliages. Ce travail a été mené dans le but d'étudier un nouvel alliage expérimental appartenant au groupe des alliages de fonderie Al-Si quasi-eutectique contenant environ 10,8%Si, à savoir l'alliage 396. Suite à ce qui a été soulevé, l'objectif principal de se travail est de rapporter les changements des critères d'usinage résultant des effets des intermétalliques de fer, à savoir a-Fe, /?-Fe et « sludge »; de deux niveaux de Cu, à savoir 2,25 et 3,5%; et de deux niveaux de Mg, à savoir 0,3 et 0,6%. De plus, les effets des alliages sans Mg et modifiés au Sr ont également été étudiés en plus des effets des éléments de décolletage tels que Sn, Bi et Pb. Le traitement thermique T6 a été sélectionné pour établir le niveau de dureté des alliages étudiés à l'intérieur d'une plage de 110± 10 BHN, conforme à la plupart des niveaux de dureté pour les applications commerciales des alliages d'aluminium. La mesure de la dureté a été faite directement sur les blocs d'usinage pour assurer que les échantillons possèdent le niveau de dureté requis. Tous ces alliages ont également été testés mécaniquement de façon à obtenir une compréhension des effets des additifs sur les propriétés mécaniques de tractions pour les mêmes conditions appliquées aux blocs de test d'usinage. Les tests d'usinage ont été faits sur une machine d'usinage horizontale haute vitesse Makino A88E sous des conditions fixes lesquelles incluent la vitesse de coupe, la vitesse d'avance, la longueur de la coupe, la géométrie de l'outil, le matériau de l'outil ainsi que le liquide de refroidissement. Les critères d'usinage observés sont les forces et les moments total de coupe, la durée de vie de l'outil en termes de nombre de trous percés ou taraudés jusqu'au bris de l'outil, la morphologie des copeaux et l'arête rapporté (BUE). Les résultats démontrent que la présence de « sludge » sous la forme de points durs a un effet sur la force de coupe et la durée de vie de l'outil qui est réduite de moitié par rapport à l'alliage de base. La formation de la phase a-Fe dans l'alliage Ml a un effet bénéfique sur la durée de vie de l'outil, ainsi cet alliage est celui qui donne le plus grand nombre de trous percés comparativement aux alliages contenant le « sludge » ou /?-Fe; ces résultats pourraient être expliqués par le fait que la formation des intermétalliques a-Fe avec leur morphologie de scripts chinois arrondis et de leur présence à l'intérieur des dendrites a-Al améliore l'homogénéité de la matrice par un durcissement des dendrites. L'augmentation du fer de 0,5% à 1% dans l'alliage 396-T6 contenant 0,5% Mn produit une amélioration distincte de l'usinabilité en termes de force de coupe et de durée de vie de l'outil. Lors des tests de taraudage, il a été trouvé que les outils en acier rapide sont considérablement plus sensibles aux phases intermétalliques de fer que les outils en carbure11 utilisés pour le perçage L'ajout de Fe ou de Mn semblent avoir aucun effet sur l'arête rapporté (BUE) et sur la morphologie des copaux comparativement à l'alliage de base. L'augmentation des niveaux de Cu ou de Mg dans l'alliage 396-T6 ont tous des effets nuisibles sur la durée de vie du foret. Cette réduction de la durée de vie du foret pourrait être attribuée à la formation d'une grande quantité de blocs de la phase A^Cu et à la formation de plaques épaisses de la phase Al-Si-Cu-Mg. L'alliage expérimental sans Mg affiche les plus faibles force et moment de coupe en plus de produire le plus grand nombre de trous de tous les alliages étudiés. Cette observation pourrait être expliquée par une précipitation combinée des phases durcissantes AI2CU, Mg2Si, Al2CuMg et AlsSiôQ^Mgg dans les alliages contenant du Mg lesquels confèrent une plus grande résistance à l'alliage que la précipitation seule de la phase AI2CU de l'alliage sans Mg. Une comparaison entre l'alliage modifié et non-modifié (contenant les mêmes niveaux de Mg et de Cu) en terme de nombre de trous percés, révèle que la morphologie des particules de Si a un effet sur la durée de vie de l'outil. L'ajout de petites, mais efficaces, quantités d'éléments de décolletages aux alliages de fonderie Al-Si améliore considérablement l'usinabilité de ces derniers. L'alliage contenant du Sn a un effet sur la durée de vie des forets en carbure et des tarauds en acier rapide. D'un autre côté, les alliages contenant du Bi mènent à un grossissement des particules de Si eutectique résultant à une détérioration de la durée de vie de l'outil. L'ajout simultané d'une petite quantité de deux ou de plusieurs éléments insolubles dans l'aluminium a un plus grand effet sur l'usinabilité en termes de réduction de la force et du moment de coupe que les ajouts individuels de chaque élément. L'ajout de Pb, Bi et Sn semble n'avoir aucun effet sur la formation de l'arête rapporté (BUE) ou sur la morphologie des copeaux excepté que l'alliage contenant du Bi montre un légère tendance à réduire la formation de l'arête rapporté (BUE) et il produit également des copeaux en forme d'éventail plus petit que ceux observés pour les alliage sans Bi. Un examen visuel des copeaux révèle que la forme d'éventail est de loin la forme prédominante pendant le perçage, de plus elle est considérée comme la forme idéale pour beaucoup d'application de perçage. La fragmentation des copeaux des alliages contenant la phase AbCu était supérieure à celle des alliages contenant la phase Mg2Si. Ainsi, l'addition combinée de Cu et de Mg devrait raffiner davantage la taille des copeaux produits. L'examen des forets usés a montré que le maximum d'usure prend place au coin extérieur de l'arête du foret, alors qu'un minimum d'usure se produit à, ou près de, la pointe du foret. Lorsque les coins du foret sont arrondis, le foret colle à la pièce et se brise si le procédé de coupe n'est pas arrêté à temps. Pour les tests de taraudage, le principal mécanisme d'usure observé est l'adhésion, même si une certaine abrasion pourrait se produire lors du taraudage des alliages contenant le « sludge » et le Bi. La rupture se produit fréquemment dans la patrie chanfreinée du taraud puisqu'elle génère une majeure partie de la force résultante, en raison de la plus grande section de copeaux apparentée aux dents du chanfrein