Milling is a commonly used machining process where a rotating cutter removes material from the workpiece. In recent years, attention has been turned towards so called dynamic milling methods which differ from the conventional way of milling. Dynamic milling normally uses, as opposed to the conventional way, more of the axial cutting edge, smaller radial depth of cut, significantly higher cutting speed and feed per tooth. The method has demonstrated potential to save both time and money under specific circumstances, for manufacturing companies.This thesis was conducted at ISCAR Sverige AB in Uppsala, Sweden. ISCAR Metalworking is a full service supplier of carbide cutting tools. The objective is to establish if there are benefits with dynamic milling methods with regard to material removal rate and lifetime of the tool by experimentally investigating and comparing tool wear that occur with conventional- and dynamic milling methods in hardened steels. Tools used were ISCAR’s MULTI-MASTER end mills, MM A and MM B, and the hardened steels were Hardox 600 and Dievar. Analysis was performed by using a USB-microscope, scanning electron microscope (SEM) and a Wyko-profilometer. The results of this study show that dynamic milling parameters can give several benefits regarding tool life and material removal rate. When machining in Hardox 600 and Dievar, both end mills were able to achieve a higher material removal rate and lifetime with dynamic parameters compared to more conventional ones. MM A outperformed MM B in Dievar, but the results were reversed in Hardox, MM B performed better. Results from the profilometry analysis showed that in Dievar, the dynamic parameters generated a smoother surface while the surface results from Hardox were more equivocal. The main conclusion was that milling with dynamic parameters is generally more advantageous and should be utilised, if possible.

Doctor of Philosophy (PhD) / This thesis aims to establish a sound scientific methodology for the effective and efficient polishing of thermally stable PCD composites (consisting of diamond and SiC) for cutting tools applications. The surface roughness of industrial PCD cutting tools, 0.06 μm Ra is currently achieved by mechanical polishing which is time consuming and costly because it takes about three hours to polish a 12.7 mm diameter PCD surface. An alternative technique, dynamic friction polishing (DFP) which utilizes the thermo-chemical reactions between the PCD surfaces and a catalytic metal disk rotating at high peripheral speed has been comprehensively investigated for highly efficient abrasive-free polishing of PCD composites. A special polishing machine was designed and manufactured in-house to carry out the DFP of PCD composites efficiently and in a controllable manner according to the requirements of DFP. The PCD polishing process and material removal mechanism were comprehensively investigated by using a combination of the various characterization techniques: optical microscopy, SEM and EDX, AFM, XRD, Raman spectroscopy, TEM, STEM and EELS, etc. A theoretical model was developed to predict temperature rise at the interface of the polishing disk and PCD asperities. On-line temperature measurements were carried out to determine subsurface temperatures for a range of polishing conditions. A method was also developed to extrapolate these measured temperatures to the PCD surface, which were compared with the theoretical results. The material removal mechanism was further explored by theoretical study of the interface reactions under these polishing conditions, with particular emphasis on temperature, contact with catalytic metals and polishing environment. Based on the experimental results and theoretical analyses, the material removal mechanism of dynamic friction polishing can be described as follows: conversion of diamond into non-diamond carbon takes place due to the frictional heating and the interaction of diamond with catalyst metal disk; then a part of the transformed material is detached from the PCD surface as it is weakly bonded; another part of the non-diamond carbon oxidizes and escapes as CO or CO2 gas and the rest diffuses into the metal disk. Meanwhile, another component of PCD, SiC also chemically reacted and transformed to amorphous silicon oxide/carbide, which is then mechanically or chemically removed. Finally an attempt was made to optimise the polishing process by investigating the effect of polishing parameters on material removal rate, surface characteristics and cracking /fracture of PCD to achieve the surface roughness requirement. It was found that combining dynamic friction polishing and mechanical abrasive polishing, a very high polishing rate and good quality surface could be obtained. The final surface roughness could be reduced to 50 nm Ra for two types of PCD specimens considered from pre-polishing value of 0.7 or 1.5 μm Ra. The polishing time required was 18 minutes, a ten fold reduction compared with the mechanical abrasive polishing currently used in industry.

A fixture is a critical link in a machining system. The majority of prior work treats the fixture-workpiece system as quasi-static and ignores the system dynamics. In addition, material removal effect (MRE) on fixture-workpiece dynamics is generally ignored. The primary goal of this thesis is to develop a model-based framework for analysis and synthesis of the fixturing dynamic stability of a machining fixture-workpiece system accounting for the MRE. Five major accomplishments of this thesis are summarized as follows: First, a systematic procedure for analysis of fixturing dynamic stability of an arbitrarily configured machining fixture-workpiece system is developed. Second, models and approaches developed in this work are experimentally validated. It is found that consideration of dynamics and characterization of system dynamic properties are crucial for an accurate analysis. Third, an in-depth investigation of the MRE on fixture-workpiece dynamics is performed. The results show that material removal can significantly change the system characteristics and behavior and approaches developed are capable of capturing the change. Fourth, roles of important fixture design and machining process parameters in affecting fixturing dynamic stability are studied and understood via a parameter effect analysis. Additionally, fixturing dynamic stability is found to be sensitive to the parameter imprecision. Finally, a generic approach for determination of minimum clamping forces that ensure fixturing dynamic stability is developed. Because of MRE, dynamic clamping is found to be an option to achieve the best possible system performance. Models and approaches developed in this thesis are generic and can be used as simulation tools in fixture design. Insights obtained from this research advance the knowledge base of machining fixtures and provide general fixture design guidelines.

Using the envelope theory, the mathematical model of the end face profile and the working tool path of a special optical fiber polishing machine is deve- loped in this study. During the polishing process, the polisher is controlled by three parameters including the fiber rotational angle, the height H and the angle between the fiber and polisher. The contact points between the optical fiber and the polishing plate will determine the profile of the fiber end face. The 3-D end face with double-variable curvatures can be fabricated by properly controlling these three parameters. Since the grinding (polishing) material removal rate is related to machining time and normal contact force, the grinding (polishing) tool path and parameters are needed some modification in order to get the precise end profiles. Example of fiber end faces of 2-D elliptical face and 3-D ellipsoid are given to check the developed mathematical model in this study by computer solid modeling.

Doctor of Philosophy (PhD) / This thesis aims to establish a sound scientific methodology for the effective and efficient polishing of thermally stable PCD composites (consisting of diamond and SiC) for cutting tools applications. The surface roughness of industrial PCD cutting tools, 0.06 μm Ra is currently achieved by mechanical polishing which is time consuming and costly because it takes about three hours to polish a 12.7 mm diameter PCD surface. An alternative technique, dynamic friction polishing (DFP) which utilizes the thermo-chemical reactions between the PCD surfaces and a catalytic metal disk rotating at high peripheral speed has been comprehensively investigated for highly efficient abrasive-free polishing of PCD composites. A special polishing machine was designed and manufactured in-house to carry out the DFP of PCD composites efficiently and in a controllable manner according to the requirements of DFP. The PCD polishing process and material removal mechanism were comprehensively investigated by using a combination of the various characterization techniques: optical microscopy, SEM and EDX, AFM, XRD, Raman spectroscopy, TEM, STEM and EELS, etc. A theoretical model was developed to predict temperature rise at the interface of the polishing disk and PCD asperities. On-line temperature measurements were carried out to determine subsurface temperatures for a range of polishing conditions. A method was also developed to extrapolate these measured temperatures to the PCD surface, which were compared with the theoretical results. The material removal mechanism was further explored by theoretical study of the interface reactions under these polishing conditions, with particular emphasis on temperature, contact with catalytic metals and polishing environment. Based on the experimental results and theoretical analyses, the material removal mechanism of dynamic friction polishing can be described as follows: conversion of diamond into non-diamond carbon takes place due to the frictional heating and the interaction of diamond with catalyst metal disk; then a part of the transformed material is detached from the PCD surface as it is weakly bonded; another part of the non-diamond carbon oxidizes and escapes as CO or CO2 gas and the rest diffuses into the metal disk. Meanwhile, another component of PCD, SiC also chemically reacted and transformed to amorphous silicon oxide/carbide, which is then mechanically or chemically removed. Finally an attempt was made to optimise the polishing process by investigating the effect of polishing parameters on material removal rate, surface characteristics and cracking /fracture of PCD to achieve the surface roughness requirement. It was found that combining dynamic friction polishing and mechanical abrasive polishing, a very high polishing rate and good quality surface could be obtained. The final surface roughness could be reduced to 50 nm Ra for two types of PCD specimens considered from pre-polishing value of 0.7 or 1.5 μm Ra. The polishing time required was 18 minutes, a ten fold reduction compared with the mechanical abrasive polishing currently used in industry.

The ability to pattern in the nanoscale to drill holes, to draw lines, to make circles, or more complicated shapes that span a few atoms in width is the main driver behind current efforts in the rapidly growing area of nanomanufacturing. In applications ranging from the microprocessor industry to biomedical science, there is a constant need to develop new tools and processes that enable the shrinking of devices. For this and more applications, nanomanufacturing using electron beams offers a window of opportunity as a top-down approach since electrons, unlike light, have a wavelength that is in the order of the atomic distance. Though the technology based on electron beams has been available for more than twenty years, new concepts are constantly being explored and developed based on fundamental approaches. As such, a tool that utilizes electron field-emission from carbon nanotubes was proposed to accomplish such feats. A full numerical analysis of electron field-emission from carbon nanotubes for nanomachining applications is presented. The different aspects that govern the process of electron field-emission from carbon nanotubes using the finite element method are analyzed. Extensive modeling is carried here to determine what the effect of different carbon nanotube geometries have on their emission profiles, what energy transport processes they are subject to, and establish what the potential experimental parameters are for nanomachining. This dissertation builds on previous efforts based on Monte Carlo simulations to determine electron deposition profiles inside metals, but takes them to next level by considering realistic emission scenarios. A hybrid numerical approach is used that combines the two-temperature model with Molecular Dynamics to study phase change and material removal in depth. The use of this method, allows the determination of the relationship between the amount of energy required to remove a given number of atoms from a metallic workpiece and the number of carbon nanotubes and their required settings in order to achieve nanomachining. Finally, the grounds for future work in this area are provided, including the need for novel electron focusing systems, as well as the extension of the hybrid numerical approach to study different materials.

Dans le cas des pièces aéronautiques de grandes dimensions et de formes complexes nécessitant un bon état de surface, les opérations de polissage sont la plupart du temps réalisées manuellement par des opérateurs spécialisés. Ces opérations étant longues, pénibles et coûteuses, il paraît pertinent de s’intéresser à leur automatisation. Dans ces travaux de thèse, nous nous intéressons à la mise en place d’un processus de polissage robotisé pour un train d'atterrissage en acier à haute résistance. La définition du processus robotisé passe par la définition des outils adéquats (taille de grain, forme et souplesse), des conditions de polissage (effort, vitesse de coupe, vitesse d’avance, angle de dépinçage et recouvrement) et le réglage des paramètres de la commande en effort en fonction du matériau à polir et de la spécification de rugosité visée. Un modèle d’enlèvement de matière est ensuite proposé afin de maîtriser le défaut d’état de surface généré pour des outils « disques ». Une campagne expérimentale permet enfin de valider la mise en œuvre du robot et du processus de polissage sur une pièce spécifique, notamment en ce qui concerne la chaîne numérique. / In the case of aircraft large parts and complex shapes requiring a good finish state, polishing operations are mostly performed manually by specialized operators. These operations are long, painful and expensive, it seems relevant to be interested in their automation. In the thesis work, we focus on the development of a robotic polishing process for high strength steel landing gear. The definition of the robotic process involves the definition of appropriate tools (grain size, shape and flexibility), polishing conditions (force, cutting speed, feed rate, inclination angle and overlap) and adjustment of parameters the force control based on the material to be polished and the specification roughness. A material removal model is then proposed to control the surface state generated for discs tools. Finally, an experimental campaign validates the implementation of the robot and the polishing process on a specific part, in particular as regards the numerical chain.

To achieve efficient planarization with reduced device dimensions in integrated circuits, a better understanding of the physics, chemistry, and the complex interplay involved in chemical mechanical planarization (CMP) is needed. The CMP process takes place at the interface of the pad and wafer in the presence of the fluid slurry medium. The hardness of Cu is significantly less than the slurry abrasive particles which are usually alumina or silica. It has been accepted that a surface layer can protect the Cu surface from scratching during CMP. Four competing mechanisms in materials removal have been reported: the chemical dissolution of Cu, the mechanical removal through slurry abrasives, the formation of thin layer of Cu oxide and the sweeping surface material by slurry flow. Despite the previous investigation of Cu removal, the electrochemical properties of Cu surface layer is yet to be understood. The motivation of this research was to understand the fundamental aspects of removal mechanisms in terms of electrochemical interactions, chemical dissolution, mechanical wear, and factors affecting planarization. Since one of the major requirements in CMP is to have a high surface finish, i.e., low surface roughness, optimization of the surface finish in reference to various parameters was emphasized. Three approaches were used in this research: in situ measurement of material removal, exploration of the electropotential activation and passivation at the copper surface and modeling of the synergistic electrochemical-mechanical interactions on the copper surface. In this research, copper polishing experiments were conducted using a table top tribometer. A potentiostat was coupled with this tribometer. This combination enabled the evaluation of important variables such as applied pressure, polishing speed, slurry chemistry, pH, materials, and applied DC potential. Experiments were designed to understand the combined and individual effect of electrochemical interactions as well as mechanical impact during polishing. Extensive surface characterization was performed with AFM, SEM, TEM and XPS. An innovative method for direct material removal measurement on the nanometer scale was developed and used. Experimental observations were compared with the theoretically calculated material removal rate values. The synergistic effect of all of the components of the process, which result in a better quality surface finish was quantitatively evaluated for the first time. Impressed potential during CMP proved to be a controlling parameter in the material removal mechanism. Using the experimental results, a model was developed, which provided a practical insight into the CMP process. The research is expected to help with electrochemical material removal in copper planarization with low-k dielectrics.

A theory of the sub-ambient fluid pressure phenomenon observed during the wet sliding of a disk on a polymeric pad is presented. Two-dimensional fluid pressure mapping using membrane pressure sensors reveals a large, asymmetrical sub-ambient pressure region occupying about 70 percent of the disk-pad contact area. At the same time, a small positive pressure region exists near the trailing edge of the disk. This phenomenon is believed to be present during chemical mechanical polishing (CMP) and can contribute to the contact pressure, affecting the material removal rate and removal uniformity. Depending on the load and pad speed, the real contact pressure can be more than 2 times the nominal contact pressure due to the applied load. Tilt measurements of the disk carried out by a capacitive sensing technique indicate that the disk is tilted towards the leading edge and pad center when the pad is rotating. In addition, wafer bow is found to be less than 2 m and wafer tilt with respect to the wafer carrier is 5 to 7 m in the CMP configuration. A two-dimensional mixed-lubrication model based on the Reynolds equation is developed and solved using a finite differencing scheme. The pad is modeled as two layers: a top asperity layer described by the Greenwood and Williamson equation, and the bulk pad as linearly elastic. The orientation of the disk is determined by balancing the fluid and solid forces acting on it and solving using a modified Newtons method. It is found that the tilt of the disk and the pad topography play important roles in the distribution of fluid pressure through affecting the film thickness distribution. For a pad with severe topography, minimum and maximum fluid pressures of -90 kPa and +51 kPa respectively are detected. The model is able to recreate the experimental pressure maps. A material removal rate model based on mechanical abrasion and statistics has also been developed. Comparisons of model predictions and silicon oxide polishing results show agreement.

Mechanical grinding process is the most popular way to fabricate the fiber micro lenses, although there are some other methods, such as chemical etching, laser machining and focused ion beam micro-cutting. Mechanical grinding has its uniqueness in grinding Conical-Wedge-Shaped Fiber Endface, fiber endface with polygon-cone-shape, and fiber endface with double-variable curvatures. The double-variable curvatures fiber endface polisher, designed and manufactured by Mechanism Design Lab of NSYSU, is employed in this study. The normal force of the fiber endface is derived firstly and then the experimental parameters and data are substituted into the material removal rate (M.R.R.) formula to obtain M.R.R. and the Preston¡¦s constant K. The process parameters of the feed rate and polishing time on the fabrication of the fiber endface are analyzed. The polisher is calibrated and adjusted to improve the precision of the optical-fiber endface. A fiber endface with double-variable curvature is successfully fabricated in a single grinding process by properly controlling the fiber rotation angle, inclining angle, and the distant between the endface and the grinding film simultaneously. The grinding process developed in this study can be applied for fabricating optical fiber lenses in fiber optics communication as well as different types of micro probes, and micro spectroscopefors in other applications.