Micromachining

To present their work in the field of micromachining, researchers from distant parts of the world have joined their efforts and contributed their ideas according to their interest and engagement. Their articles will give you the opportunity to understand the concepts of micromachining of advanced materials. Surface texturing using pico- and femto-second laser micromachining is presented, as well as the silicon-based micromachining process for flexible electronics. You can learn about the CMOS compatible wet bulk micromachining process for MEMS applications and the physical process and plasma parameters in a radio frequency hybrid plasma system for thin-film production with ion assistance. Last but not least, study on the specific coefficient in the micromachining process and multiscale simulation of influence of surface defects on nanoindentation using quasi-continuum method provides us with an insight in modelling and the simulation of micromachining processes. The editors hope that this book will allow both professionals and readers not involved in the immediate field to understand and enjoy the topic

FABRICATION OF CERAMIC MICROPATTERNS AND THEIR IMPACT ON BONE CELLS

The main objective of this study is to elucidate possible methods of producing ceramic calcium phosphate micropatterns ranging from 5 to 100 µm. Today, micropatterned ceramic surfaces are of great interest for fundamental materials research as well as for high-end industrial processes, whereas the fabrication of these patterns in the sub-100 µm range is still a challenge. Therefore, six different patterning techniques have been applied in order to generate ceramic patterns: Microtransfer molding (µTM), modified micromolding (m-µM), Aerosol-Jet® printing, CNC-micromachining, laser ablation and direct laser interference patterning (DLIP). The patterning techniques have been evaluated concerning their capability of fabricating ceramic patterns smaller than 100 µm. Another objective of this study has been the investigation of the influence of ceramic patterns on human osteoblasts (HOB). This investigation has revealed that ceramic hydroxyapatite-based patterns ranging from 16 to 77 µm in widths have a strong influence on the contact guidance of the HOB, whereas the cells showed distinct orientations between 0°-15° in reference to the pattern direction

Investigation into micro machinability of Mg based metal matrix compostites (MMCs) reinforced with nanoparticles

PhD ThesisAs composite materials with combination of low weight and high engineering strength, traditional metal matrix composites (MMCs) with micro-sized reinforcement (micro-MMCs) have been utilized in numerous area such as aerospace, automobile, medical and advanced weapon systems in the past two decades. With the development of composite materials, metal matrix composites reinforced with small volume fraction of nano-sized reinforcements (nanoMMCs) exhibits an equivalent and even better properties than that reinforced with large volume of micro-sized reinforcement and thus receive increasing attention from academia and industries. MMCs components are typically fabricated in near net shape process such as casting. But micro machining processes are indispensable in order to meet the increasing demands on the component with high dimensional accuracy and complex shapes. However, the enhanced mechanical properties of MMCs and tool-like hardness of reinforced particles bring challenges to machining process. The deteriorative machined surface finish and excessive tool wear have been recognised as the main obstacles during machining of MMCs due to their heterogeneous and abrasive nature. In this research, the detailed material removal mechanism of nano-MMCs in terms of micro machinability, micro tool wear and simulated material removal process with finite element analysis (FEA) is investigated. The systematic experimental studies on micro machining mechanism of magnesium-based MMCs reinforced with nanoparticles (Ti, TiB2, BN, ZnO) are conducted. The cutting force, burr formation, surface roughness and morphology are characterised to investigate the micro machinability under the effect of various machining parameters, particle volume fraction and matrix/reinforcement materials using design of experiment (DoE) and analysis of variance (ANVOA) methods. The micro structure changes of Mg-MMCs by addition of nanoparticles were taken into account. In addition, surface morphology and the minimum chip thickness is obtained and characterised with the aim of examining the specific cutting energy. A comprehensive investigation of tool wear mechanisms in the micro milling of Mg-MMCs is conducted. The tool wear is characterised both quantitatively and qualitatively by observing tool wear patterns and analysing the effect of cutting parameters and tool coating on average flank wear, reduction in tool diameter, cutting forces, surface roughness, and burr formation. The main wear mechanisms at different machining conditions are determined. Finally, the tool wear phenomenon observed from experiments is explained by simulating the tool-particles interaction using finite element modelling, and hence new wear mechanisms are proposed for machining nano-MMCs. iv The two dimensional micromechanical finite element (FE) models are established to study the material removal mechanism of MMCs reinforced with micro-sized and nanoparticles in micro machining process with consideration of size effect. Two phases, namely particle and matrix are modelled in FE cutting models. Particle fracture properties are involved in micro-sized particles to study the fracture behaviours. The cutting force, tool-particles interaction, particle fracture behaviours, stress/strain distribution, chip formation process and surface morphology are investigated in the FE models. The surface defect generation mechanism is studied in details by developing the additional three dimensional (3D) FE models in machining micro-MMCs. Moreover, the cutting mechanism comparison between machining nano-MMCs and microMMCs is conducted to investigate the effect of significant particle size reduction from micro to nano-scale. The model validation is carried out by studying the chip morphology, cutting force, surface morphology obtained from machining experiments and good agreements are found with the simulation results

In-Situ Characterization of Burr Formation in Finish Machining of Inconel 718

One of the undesirable byproducts that occur during the machining process is the development of burrs, which are defined as rough excess material that forms around the geometric discontinuities of a part. Burrs are especially problematic because they have negative impacts across the triple bottom line: economic, environmental, societal. For one, they are expensive to remove because the deburring process is entirely manual and requires skill. Further, burr material is typically discarded which is adding to the already mounting waste generated from machining such as in coolant and chip disposal. Lastly, there are many societal implications, such as operator injury during assembly and the failure of parts in service because of leftover burrs that turned into stress concentrations. Therefore, optimizing the machining process to minimize burrs and promote sustainable manufacturing is a central challenge for manufacturers today. However, the burr formation mechanism is complex, and research on the phenomenon is scarce. The current state of the art focuses almost exclusively on drilling and micro-milling processes, with very little work investigating burr formation in the conventional machining processes of turning and milling. Research as it pertains to materials that are difficult-to-machine like nickel and titanium-based superalloys is even less common, as most of the literature focuses on softer materials like aluminum and steel alloys. Superalloys are especially crucial to the aerospace industry, comprising most of the components in jet engines. Thus, the objective of this study was to characterize burr formation for nickel-based superalloy Inconel 718 using a custom-built in-situ testbed capable of ultra-high-speed imaging in orthogonal cuts. Experiments were carried out to measure the variation in burr development with respect to several cutting parameters: uncut chip thickness, tool-wear, and cutting speed. Firstly, the exit and side burr geometry were measured after each machining trial for a variety of different metrics. Results showed that all cutting parameters have an influence on the burr geometry, although not every cutting parameter had statistical significance on certain burr metrics. For instance, it was found that side burrs were much more sensitive to tool-wear than exit burrs. Then, by combining digital image correlation (DIC) with a physics-based model, the flow stress was calculated during exit burr formation and results revealed that the stress at the exit burr root was approximately equal to the flow stress. Finally, this study investigates the fracture phenomenon during exit burr formation—it was found that besides the requirement of high strain rate and depth of cut, negative exit burrs, there is a microstructural size effect, which had not been reported by prior work

Titanium Alloys

Titanium alloys, due to unique physical and chemical properties (mainly high relative strength combined with very good corrosion resistance), are considered as an important structural metallic material used in hi-tech industries (e.g. aerospace, space technology). This book provides information on new manufacturing and processing methods of single- and two-phase titanium alloys. The eight chapters of this book are distributed over four sections. The first section (Introduction) indicates the main factors determining application areas of titanium and its alloys. The second section (Manufacturing, two chapters) concerns modern production methods for titanium and its alloys. The third section (Thermomechanical and surface treatment, three chapters) covers problems of thermomechanical processing and surface treatment used for single- and two-phase titanium alloys. The fourth section (Machining, two chapters) describes the recent results of high speed machining of Ti-6Al-4V alloy and the possibility of application of sustainable machining for titanium alloys

Modelling of Tool Life and Micro-Mist flow for Effective Micromachining of 316L Stainless Steel.

Recent technoligical advancement demands new robust micro-components made out of engineering materials. The prevalent methods of manufacturing at micro-nano level are established mostly for silicon structures. Therefore, there is interest to develop technologies for micro-fabrication of non silicon materials. This research studies microend-milling of 316L stainless steel. Machine tool requirement, tool modeling, cutting fluid evaluation, and effect of cutting parameters are investigated. A machine tool with high rigidity, high spindle speed, and minimal runout is selected for successful micro-milling. Cumulative tool wear and tool life of these micro-tools are studied under various cutting conditions. Ideal abrasive wear is observed when applying mist cooling whereas inter-granular shearing is the major failure mode while flood cooling or dry cutting during micro-machining. Various experiments and computational studies suggest an optimal position of the mist nozzle with respect to a tool that provides maximum lubrication at the cutting edge. Mist droplets effectively penetrate the boundary layer of a rotating tool and wet the cutting edge and significantly improve the tool life

High precision laser micromachining for sensing applications

In this PhD thesis the development of laser-based processes for sensing applications is investigated. The manufacture of optical fibre sensors is of particular interest because fibre optics offers advantages in space constraint environments or in environments where electronic sensors fail. Laser micromilling of the transparent and mechanically challenging to machine materials sapphire and fused silica is investigated. An industrial picosecond laser providing 6 ps pulses with the ability to emit at 1030 nm (IR), 515 nm (green) and 343 nm (UV) is used for processing of these materials; providing a maximum laser pulse energy of 25 μJ at UV, 75 μJ at green and 125 μJ in IR. The UV wavelength is identified as the most reliable machining wavelength for these materials with the least amount of cracking and achieving a surface roughness Rq of just 300 nm compared to 1220 nm (green) and 1500 nm (IR) in fused silica. In sapphire the surface roughness is 420 nm using UV , with green it is 500 nm and using IR it is 800 nm. The material removal rates using this laser milling process are larger than with other micromachining techniques, hence it was applied to manufacture cantilever sensors on the end of an optical fibre. The monolithic fibre top sensor is carved out of conventional telecommunications optical fibre. The cantilever is a structure of less than 10 μm thickness, 20 μm width and 125 μm length. Using the Fabry-Perot interferometer method the sensor detects small movements with a resolution better than 15 nm. A technique is developed to correct for laser machining angles and hence generate parallel interferometer faces. An electric arc cleaning process of the laser manufactured cantilever sensors is investigated that reduces the surface roughness to 30 nm. The manufacturing process reduces manufacturing times by a factor of 100. A working sensor is demonstrated in a deflection experiment. Such short pulses are not always required to manufacture the highest resolution sensors. The manufacture of high precision optical encoder scales (pitch 8 μm, depth 200 nm) with two processes (i) ablative removal of a polyimide layer and (ii) a melt reflow process on nickel coated scales is demonstrated. Both processes are using 33 ns laser pulses at 355 nm generating a pulse energy of up to 1 mJ

Meso scale component manufacturing: a comparative analysis of non-lithography and lithography-based processes

The paper identifies the meso scale (10 µm to few millimeters) component size that can be manufactured by using both lithography and non-lithography based approaches. Non-lithography based meso/micro manufacturing is gaining popularity to make micro 3D artifacts with various engineering materials. Being in the nascent stage, this technology looks promising for future micro manufacturing trends. Currently, lithography based micro manufacturing techniques are mature, and used for mass production of 2D, 2.5D features and products extending to 3D micro parts in some cases. In this paper, both the techniques at state-of-the-art level for meso/micro scale are explained first. The comparison is arranged based on examples and a criterion is set in terms of achievable accuracy, production rate, cost, size and form of artifacts and materials used. The analysis revealed a third combined approach where a mix of both techniques can work together for meso scale products. Critical issues affecting both the manufacturing approaches, to advance in terms of accuracy, process physics, materials, machines and product design are discussed. Process effectiveness guideline with respect to the component scale, materials, achievable tolerances, production rates and application is emerged, as a result of this exercise

A Micro-milling cutting force and chip formation modeling approach for optimal process parameters selection

Las últimas décadas evidencian una demanda creciente por componentes miniaturizados con dimensiones reducidas y tolerancias estrechas, lo cual ha conllevado al desarrollo de la micro y nanotecnología. El micro-fresado, dentro de los procesos de micro-mecanizado, tiene el potencial de ser uno de los procesos de remoción de material más costo-efectivos y eficientes debido a su facilidad de aplicación, variedad de materiales de trabajo y flexibilidad geométrica. Se enfrenta a unos retos complejos debido al efecto de tamaño, vibraciones y otros factores incontrolables. Este estudio analiza dicho proceso orientado hacia desarrollar una mejor comprensión de la mecánica del micro-corte para ser aplicada en la optimización de parámetros de proceso. Se propone un acercamiento al modelado híbrido en forma novedosa, que permite una evaluación numérica a priori para evaluación de fuerzas y esfuerzos, combinado con experimentación para evaluar parámetros relevantes a la industria (formación de rebabas, desgaste de herramientas, entre otros).DoctoradoDoctor en Ingeniería Mecánic