Beam Machining Process Research Articles

Study on multiscale modeling and simulation of liquid-assisted laser beam machining process

Liquid-assisted laser beam machining (LA-LBM) process is used as an alternative to existing laser beam machining (LBM) process to address the problems associated with the extreme heat of the laser. In this research, the thermal effects of laser and hydrodynamics effects of the liquid medium in the LA-LBM process are investigated to understand the complex interactions involved in the material removal during LA-LBM process. The study utilizes the versatile multiscale modeling approach by coupling the molecular and continuum domains. The research investigates the role of the water layer in the LA-LBM process along with the material transformations taking place in the water layer in the vicinity of the machined zone. The results of the study augment our existing knowledge of the complex mechanisms involved in the LA-LBM process. Investigation on cavity depth revealed the increase in material removal with the increase in laser heat. The change in water layer thickness revealed the reduction in the radius of the heat-affected zone while further explaining the nodal temperature distribution profile and electron temperature distribution in the water layer.

Material characterization and unconventional machining on synthesized Niobium metal matrix

The Purpose of this work is to develop a niobium based metal matrix alloy through sintering based powder metallurgy technique. The 2, 4 and 6 weight percentage of Titanium Carbide (TiC) is added to the alloy. Various material properties such as hardness, tensile strength, impact strength and density are measured after the addition of TiC particle. The characterization, microstructure and particle size of the developed metal matrix are learnt through Scanning Electron Microscope (SEM) and Energy Dispersive Analysis of x-rays (EDAX). Finally, the synthesized niobium metal matrix is machined by unconventional machining processes namely Ultrasonic Machining (USM) and Laser Beam Machining (LBM) processes. The various input and output parameters have been considered for this experimental work. The most influential parameters on Material Removal Rate (MRR) and Surface Roughness (SR) are found by Analysis of variance. The systematic evaluation of optimal parameters of MRR and SR are carried out by using taguchi approach.

A study on the preparation method of vaporized amplification sheets and electron beam machining characteristics

An electron beam was used to mainly utilize for polishing, finishing, welding, a lithography process, etc. However, the drilling process does not develop in the country because it is difficult to make high power parts and backing materials. The backing materials are one of the important factors and decided the quality of machined micro holes according to the constituents. This study considers the preparation of vaporized amplification sheets and the analysis of key factors for improving the electron beam processability and efficiency. We evaluated the defoaming process (for removing pores from the sheets), distribution, processability and hole shape (all based on the type of metal powder), and thermal characteristics (based on the type of silicon). Also, we identified process parameters for the optimization of the electron beam machining process.

Experimental Investigation of Varying Laser Pass on Micro-channel Characteristics of Thick PMMA by Laser Transmission Micro-machining

Abstract Depth of fabrication is an essential characteristic of micro-channels. The laser beam machining process is one of the most suitable processes to fabricate micro-channels. This process has an excellent potential for the fabrication of microfluidic devices which are instrumental for various biomedical applications such as electrophoresis, chromatography, blood protein studies, DNA analysis, etc. In this research work, an attempt has been made to fabricate micro-channels on a thick Polymethyl methacrylate (PMMA) plate at submerged condition by utilizing laser transmission micro-machining process. The laser transmission micromachining operation is conducted here at submerged condition to reduce the adverse thermal effect during machining. Nanosecond pulsed Nd: YAG laser with wavelength in near infrared region has been used here. The depth of micro-channel and heat affected zone (HAZ) width has been taken into account as machining responses. Total 3 sets of experiments which contain 31 experiments in each set have been conducted for three different laser beam pass with the aid of response surface methodology (RSM). The effects of varying laser beam pass on the depth and HAZ width has been studied.

Molecular Dynamics Simulation Study of Liquid-Assisted Laser Beam Micromachining Process

Liquid Assisted Laser Beam Micromachining (LA-LBMM) process is an advanced machining process that can overcome the limitations of traditional laser beam machining processes. This research involves the use of a Molecular Dynamics (MD) simulation technique to investigate the complex and dynamic mechanisms involved in the LA-LBMM process both in static and dynamic mode. The results of the MD simulation are compared with those of Laser Beam Micromachining (LBMM) performed in air. The study revealed that machining during LA-LBMM process showed higher removal compared with LBMM process. The LA-LBMM process in dynamic mode showed lesser material removal compared with the static mode as the flowing water carrying the heat away from the machining zone. Investigation of the material removal mechanism revealed the presence of a thermal blanket and a bubble formation in the LA-LBMM process, aiding in higher material removal. The findings of this study provide further insights to strengthen the knowledge base of laser beam micromachining technology.

Micro-grooving of silicon wafer by Nd:YAG laser beam machining

Laser beam machining process is one of the thermal advanced machining processes use for machining all the types of metals, non metals, ceramics, semiconductor, polymeric materials and alloys. For the past few decades laser Beams are being used in various manufacturing processes. Viewing this fact, the researchers have explored number of ways to improve micromachining using Nd: YAG lasers of different materials in recent years. Hence, the present research attempts to explore the effects of the different process parameters such as diode current, frequency, on surface roughness, MRR during micro-grooving of silicon wafer.

Experimental and Modeling Study of Liquid-Assisted—Laser Beam Micromachining of Smart Ceramic Materials

Smart ceramic materials are next generation materials with the inherent intelligence to adapt to change in the external environment. These materials are destined to play an essential role in several critical engineering applications. Machining these materials using traditional machining processes is a challenge. The laser beam micromachining (LBMM) process has the potential to machine such smart materials. However, laser machining when performed in air induces high thermal stress on the surface, often leading to crack formation, recast and re-deposition of ablated material, and large heat-affected zones (HAZ). Performing laser beam machining in the presence of a liquid medium could potentially resolve these issues. This research investigates the possibility of using a Liquid Assisted—Laser Beam Micromachining (LA-LBMM) process for micromachining smart ceramic materials. Experimental studies are performed to compare the machining quality of laser beam machining process in air and in a liquid medium. The study reveals that the presence of liquid medium helps in controlling the heat-affected zone and the taper angle of the cavity drilled, thereby enhancing the machining quality. Analytical modeling is developed for the prediction of HAZ and cavity diameter both in air and underwater conditions, and the model is capable of predicting the experimental results to within 10% error.

Experimental Investigation Of Quality Characteristics In Nd:YAG Laser Drilling Of Stainless Steel (AISI 316)

Micro-machining of advanced engineering materials such as stainless steels, titanium alloys, nickel alloys, and ceramics is a challenging task due to properties like high strength to weight ratio, toughness, slenderness ratio, and low thermal conductivity. Stainless steel of grade AISI 316 has wide applications in medical science, automobile engineering, aviation, and aerospace industry due to their favourable material properties such as low thermal conductivity, high corrosion resistance, and high strength to weight ratio. Micro-machining of AISI 316 with high aspect ratio is a difficult task due to excessive heat generation, micro-structural changes, and tool breakage. Laser beam machining (LBM) process is a suitable alternative machining process, since it localizes the heat source to control the micro-structural changes. The difficulty arises during laser drilling because of spatter area and heat affected zone (HAZ), which adversely affects the quality of laser drilled holes. The present study attempts to experimentally investigate the effect of laser process parameters such as pulse width, laser energy, pulse frequency, and flushing pressure on the performance measures such as spatter deposition and heat affected zone (HAZ) during drilling operation. To reduce the total number of experimental run and obtain maximum information for the experimental trials, Taguchi L27 has been adopted. Analysis of variance (ANOVA) is performed to identify significant laser parameters influencing both the performance measures. From the study, it is revealed that pulse width is the most significant parameter in the formation of spatter and HAZ. From the results, it is identified that spatter area initially increases with increase in pulse frequency and then decreases for any level of pulse width. As pulse frequency increases, laser power increases resulting in more heat input into the material. This causes increase in vapour pressure inside the laser drilled hole, more material ejection, and increase in spatter area. However, laser supported absorption (LSA) waves developed at higher value of pulse frequency brings about blockage of laser energy from the material surface as an engrossing plasma, which results in reduction of material ejection and reduction in spatter area. It is observed that HAZ increases with increase in pulse width and pulse frequency. It may be due to higher average power of the laser beam, which is directly proportional to pulse width and pulse frequency. Higher the value of pulse width, higher will be the laser thermal energy and higher HAZ.

Finite element analysis and simulation of liquid-assisted laser beam machining process

Laser beam micromachining (LBMM) process is one of the important advanced manufacturing processes which can shape almost all engineering materials with micron scale precision even for complex geometries. LBMM process when performed in air generates high heat flux causing thermal damage and poor surface finish on the substrate material. Liquid-assisted laser beam micromachining is considered as an alternate approach to the traditional laser beam micromachining process performed under air to reduce the thermal damages caused due to high heat of laser. The presence of liquid medium also helps in carrying away the molten material from the machining zone thereby preventing re-deposition. The focus of this research is to understand the effect of critical process parameters involved in liquid-assisted laser beam micromachining using finite element simulation technique. The study revealed that the width (diameter) and depth of the heat-affected zone decreased considerably with water film thickness of 0.50 mm and higher. Further experimentation is used to validate the results of the simulation model. The experimental results closely matched with the predictions of the simulation study. Micromachining performed under thin films of water and ethylene glycol showed better surface finish as compared to machining performed without water. This suggests that the liquid medium occupies the void during material removal due to laser beam and helps reducing the thermal damage.

New models for energy beam machining enable accurate generation of free forms.

We demonstrate that, despite differences in their nature, many energy beam controlled-depth machining processes (for example, waterjet, pulsed laser, focused ion beam) can be modeled using the same mathematical framework-a partial differential evolution equation that requires only simple calibrations to capture the physics of each process. The inverse problem can be solved efficiently through the numerical solution of the adjoint problem and leads to beam paths that generate prescribed three-dimensional features with minimal error. The viability of this modeling approach has been demonstrated by generating accurate free-form surfaces using three processes that operate at very different length scales and with different physical principles for material removal: waterjet, pulsed laser, and focused ion beam machining. Our approach can be used to accurately machine materials that are hard to process by other means for scalable applications in a wide variety of industries.

Reactive ion beam figuring of optical aluminium surfaces

Ultra-smooth and arbitrarily shaped reflective optics are necessary for further progress in EUV/XUV lithography, x-ray and synchrotron technology. As one of the most important technological mirror optic materials, aluminium behaves in a rather difficult way in ultra-precision machining with such standard techniques as diamond-turning and subsequent ion beam figuring (IBF). In particular, in the latter, a strong surface roughening is obtained. Hence, up to now it has not been possible to attain the surface qualities required for UV or just visible spectral range applications. To overcome the limitations mainly caused by the aluminium alloy structural and compositional conditions, a reactive ion beam machining process using oxygen process gas is evaluated. To clarify the principle differences in the effect of oxygen gas contrary to oxygen ions on aluminium surface machining, we firstly focus on chemical-assisted ion beam etching (CAIBE) and reactive ion beam etching (RIBE) experiments in a phenomenological manner. Then, the optimum process route will be explored within a more quantitative analysis applying the concept of power spectral density (PSD) for a sophisticated treatment of the surface topography. Eventually, the surface composition is examined by means of dynamic secondary ion mass spectrometry (SIMS) suggesting a characteristic model scheme for the chemical modification of the aluminium surface during oxygen ion beam machining. Monte Carlo simulations were applied to achieve a more detailed process conception.

Effects of material combination on laser beam drilling of a metal foil using a cover plate

ABSTRACTThis research investigated the microdrilling characteristics of metal foils depending on the materials of the cover plates and metal foils in the cover plate-laser beam machining (c-LBM) process, which is a method to achieve better quality in metal foil machining with a given piece of equipment. Laser beam drilling using a nanosecond pulsed laser was carried out on 10-µm-thick stainless steel 304 (STS304), nickel, and copper foils with 100-µm-thick cover plates of each material. Consequently, STS304 was found to be an effective cover plate material for reducing the hole diameter and spatter deposition on metal foils. Compared to the results without using a cover plate, the average hole diameter and the area of spatter deposition decreased by up to 77% and 96%, respectively, by using the STS304 cover plate. Meanwhile, the thermal deformation of the STS304 and nickel foils was prevented by using a cover plate, while the copper foil was barely deformed even without a cover plate. Lastly, it was remarkable that the copper foil was drilled with approximately 67% lower pulse energy than the effective minimum pulse energy required to drill it by using the STS304 cover plate, resulting in a smaller hole with little spatter.

Fabrication of various shaped tungsten micro pin arrays using micro carving technology

This paper describes a state of the art in micro-structuring high strength metallic materials. Tungsten micro pin arrays in a variety of shapes are fabricated using a micro carving technology, which combines laser beam machining and electrochemical etching processes. First, micro pin arrays were rough-shaped by laser beam machining along a pre-defined scanning path to control their structural shape. The micro pin array in this stage had near-conical shape of structures due to a recast layer. Next, the genuine shape of micro pin arrays came to the surface via electrochemical etching process to elute the recast layer into electrolyte. Quantitative elemental analysis with energy-dispersive spectroscopy (EDS) was implemented to characterize the formation of recast layer on a micro pin structure after the laser beam machining process. The atomic percentage EDS maps indicated that higher percentage of tungsten was detected on the core micro pin structure, whereas relatively large percentage of oxygen was found on the recast layer (O 9%, W 91% in the center area, and O 53%, W 47% in the outer area).

Robust optimisation of Nd: YLF laser beam micro-drilling process using Bayesian probabilistic approach

Nd: YLF laser beam machining (LBM) process has a great potential to manufacture intricate shaped microproducts with its unique characteristics. Continuous improvement (CI) effort for LBM process is usually realised by response surface methodology, which is an important tool in Design of Six Sigma. However, when determining the optimal machining parameters in CI for LBM process, model parameter uncertainty is typically neglected. Performing worst case analysis in CI, this paper presents a new loss function method that takes model parameter uncertainty into account via Bayesian credible region. Unlike existing CI methods in LBM process, the proposed Bayesian probabilistic approach is based on seemingly unrelated regression which can produce more precise estimations of the model parameters than ordinary least squares in correlated multiple responses problems. An Nd: YLF laser beam micro-drilling process is used to demonstrate the effectiveness of the proposed approach. The comparison results show that micro-holes produced by the proposed approach have better quality than those of existing approaches in terms of robustness and process capability.

A haptic digital tool to assist the design, planning and manufacture of micro- and nanostructures

This work addresses the engineering demands for precise interactive process planning for the manufacture of high precision in the manufacturing of 3D micro- and nanoproducts. It outlines the development of a digital tool based on a haptics-based human–machine interface. This interface is underpinned using an empirical model derived from a series of experimental results obtained from a focused ion beam machine through a series of experiments, which produced the surface topographies of a number of micro- and nanograting arrays; these were systemically analysed to provide an underpinning empirical database, which could be accessed via the haptic process planning system. On accessing these data, highly accurate geometrical models are then input into a haptics human machine interface to emulate the focused ion beam machining process as defined by the customised fabrication parameters. The haptic planning system predicts and simulates the shape and form of the finished product profiles as the haptic device is passed across a virtual substrate. Once the simulation is complete and the outputs verified by the user, the system then automatically outputs a stream file to drive the focused ion beam process to produce the surface topographies required. The simulation results reveal that compared with trial and error method, the haptics-based simulation method is a reliable way to plan and optimise the fabrication parameters in design and manufacture of micro- and nanogratings by focused ion beam machining cost-effectively. This could potentially provide substantial lead time and cost reductions associated with these currently inherently expensive unit cost products as well as demonstrate a novel tool not only for the planning of nanomachining cutting sequences but also for the interactive design of such products. This work also highlights the benefits of an empirical model as a means of underpinning and supporting real-time haptics interaction, something not possible using more numerical-based techniques.

Parametric Optimization of Nd:YAG Laser Beam Machining Process Using Artificial Bee Colony Algorithm

Nd:YAG laser beam machining (LBM) process has a great potential to manufacture intricate shaped microproducts with its unique characteristics. In practical applications, such as drilling, grooving, cutting, or scribing, the optimal combination of Nd:YAG LBM process parameters needs to be sought out to provide the desired machining performance. Several mathematical techniques, like Taguchi method, desirability function, grey relational analysis, and genetic algorithm, have already been applied for parametric optimization of Nd:YAG LBM processes, but in most of the cases, suboptimal or near optimal solutions have been reached. This paper focuses on the application of artificial bee colony (ABC) algorithm to determine the optimal Nd:YAG LBM process parameters while considering both single and multiobjective optimization of the responses. A comparative study with other population-based algorithms, like genetic algorithm, particle swarm optimization, and ant colony optimization algorithm, proves the global applicability and acceptability of ABC algorithm for parametric optimization. In this algorithm, exchange of information amongst the onlooker bees minimizes the search iteration for the global optimal and avoids generation of suboptimal solutions. The results of two sample paired t-tests also demonstrate its superiority over the other optimization algorithms.

An investigation of redeposition effect for deterministic fabrication of nanodots by focused ion beam

► A 3D surface topography model and simulation program was developed to imitate the focused ion beam machining process. ► The simulation program was a good tool to determine machining parameters for deterministic fabrication by focused ion beam. ► Redeposition effect reduced more than 1/3 of intended depth of the nanodots machined by focused ion beam. Focused ion beam machining is a powerful technique for micro/nanofabrication. However its machined surface form accuracy will be degrade due to atoms redeposition in the nanofabrication process. In this paper, a 3D surface topography model and associated simulation program are developed to study redeposition effect for precise and deterministic fabrication of nanodots by focused ion beam. The simulation is implemented by level set method. The angular dependence of sputtering yield is calculated by a Monte Carlo simulation program – TRIDYN. The simulation results have been evaluated by focused ion beam fabrication of nanodots experiment on a silicon substrate. It demonstrates that the simulation method can precisely describe the generation of 3D surface in focused ion beam machining process (with less than 10% simulation error). Redeposition has made significant contribution to the surface generation in nanoscale fabrication by reducing more than 1/3 of intended depth. The model and simulation program developed has approved to be a good tool to determine proper machining parameter to achieve deterministic nanofabrication by focused ion beam.

Development of a compliance tester for assessing and reducing the static compliance of fixture-workpiece systems

This chapter provides comprehensive knowledge regarding the fabrication of nanoproducts and element of micro-electromechanical systems using various techniques and processes. Both well-established techniques, such as nanomachining (ultra-precision) and new trends in improving nanoprocesses taking into account AFM, laser beam machining, electron beam machining processes are overviewed. The background of nanomachining processes, including typical machining operations such as turning, milling and grinding and different construction materials (metallic and nonmetallic), is outlined. The physical mechanisms responsible for the transition from brittle to ductile regime machining are explained. Moreover, a special focus is given on new constructions, control systems and effective applications of nanomachining techniques. In addition, the focus was directed towards the nanotools applied, special tooling systems, fixturing systems and selection of machining conditions. All nanomachining techniques discussed are supported by new research works, original investigations and practical examples. In addition, measurement scaling to nanolevels is highlighted and a number of appropriate measuring devices and measurement systems are presented. Some developing trends in nanomanufacturing termed tip-based nanomanufacturing are discussed.

Evaluation of Standard Defects Using Surface Acoustic Waves Generated by Phase Velocity Scanning of Laser Interference Fringes

In order to maintain the reliability of structural materials such as ceramics and micromachines, it is important to nondestructively evaluate micrometer-order surface defects that reduce the strength of these materials. Standard defects whose size and shape are precisely defined are needed but until now, only Vickers and Knoop indentation cracks were available. However, since indentation cracks are created stochastically, it is difficult to define their precise size and shape. Alternatively, we tried to make standard defects on a Si (001) wafer using the focused ion beam machining process. Four grooves of 200 µm length and 6.8, 7.8, 12.4 and 28.7 µm depth were formed by a 90-nm-diameter Ga ion beam on Si surface. We used iodine gas for making fine edges. We then tried to evaluate these defects by using the phase velocity scanning (PVS) method which generates surface acoustic waves (SAW) with excellent directivity. We used 60–110 MHz SAW generated by the PVS method and the distance from defects to probe of SAW was about 2 mm. We succeeded in detecting the scattered wave from the 6.8-µm-deep slit (d/λ∼0.08) and confirmed the usefulness of these standard defects. Next, we compared the theoretical reflection coefficient of an infinite-length crack with our experimental result and confirmed that they agree qualitatively.

Evaluation of standard defects using surface acoustic waves generated by phase velocity scanning of laser interference fringes

In order to maintain the reliability of structural materials such as ceramics, it is important to nondestructively evaluate micrometer-order surface defects that reduce the strength of materials. The standard defects are needed whose size and shape are precisely defined, but only a Vickers and Knoop indentation crack can be used traditionally. However, since indentation cracks are created stochastically, it is difficult to precisely define the size and shape. Alternatively creation of standard defects on Si(100) wafers was attempted by using the focused ion beam (FIB) machining process, and three grooves of 3-μm depth and 50-, 100-, and 200-μm length were made by a 90-nm-diam Ga ion beam on a Si surface. Iodine gas was used for making fine edges. Then these defects were evaluated by using the phase velocity scanning (PVS) method which generates excellently directive surface acoustic waves (SAWs). A 60-MHz SAW generated by the PVS method was used and the distances from detects to the probe of SAW were about 4 mm. The reflection coefficients of 200-, 100-, and 50-μm defects were evaluated to be about 9.6%, 3.5%, and 1%, respectively, and the usefulness of these standard defects was confirmed.