Laser Beam Micromachining Research Articles

Machining technologies and structural models of microfluidic devices

In the past decades, microfluidic chips have been one of the hottest research topics in the “lab-on-a-chip” field. However, it is still a challenge for design the perfect microchannels with high functional integration, complex geometry, and high production efficiency. This review paper provides a comprehensive overview of microfluidic structural models and designs, manufacturing techniques, and bonding methods. The effect of three types of microfluidic channel structure models and their configuration parameters on the fluid behaviors of microfluidics was investigated. Surface-to-volume ratio of the flow channel is a critical parameter for determining the mixing and diffusion capabilities of the microfluidic devices (MDs). Thereafter, the main manufacturing techniques for microstructures were discussed, including etching, photolithography, soft lithography, molding, mechanical micro-machining, laser beam micromachining, printing, and 3D printing. We performed a statistical analysis to discuss the relative advantages and disadvantages of these manufacturing methods. In addition, the current bonding methods for MDs were also summarized, including thermal bonding, solution adhesive bonding, dry adhesive bonding, plasma bonding, and anodic bonding. a comparison of different bonding methods was presented to provide a reference to select a suitable bonding method for the assembly of microfluidic device. Finally, the tendencies and challenges of microchannel manufacturing were discussed, and the prospects were also provided.

A novel numerical modeling of microsecond laser beam percussion micro-drilling of Hastelloy X: experimental validation and multi-objective optimization

The paper investigates the characteristics of the laser beam percussion micro-drilling (LBPMD) process in aerospace nickel-based superalloy Hastelloy X using microsecond pulses. The quality of the drilled hole is crucial in laser beam micromachining, and selecting appropriate process parameters significantly impacts the hole’s quality. The objective is to achieve predefined hole dimensions with minimal taper angles. Additionally, the study focuses on the alteration of pulse width, which is a combination of laser pulse frequency and duty cycle. Laser power (P), duty cycle % (D), focal plane position (FPP), and laser frequency (f) are considered input parameters, while geometric features such as inlet and outlet diameters, hole taper angle, and inlet circularity are examined as process responses. ANOVA is employed to establish significant relationships between process parameters and response variations based on experimental tests. Creating a precise simulation model that accurately accounts for the moving boundary of the target material’s receding surface is a crucial and challenging task in formulating the laser heat conduction problem. It is necessary to simultaneously capture the material’s dynamic front movement and update the boundary conditions of the laser source. To model the micro-drilled hole with LBPMD, the UMESHMOTION and DFLUX subroutines, along with the arbitrary Lagrangian-Eulerian (ALE) adaptive remesh algorithm in the Abaqus™ software, are utilized. Notably, no previous numerical study has predicted the geometry of micro-drilled holes using this technique. The proposed procedure is validated through the predictions of inlet and outlet hole diameters. Special emphasis is placed on the validation of models. Consequently, the numerical model and statistical model are compared as well as the need to define model applicability. The study demonstrates that all input parameters significantly influence the inlet hole diameter, while the pulse width notably affects the taper angle and circularity. The interaction between high laser frequency and low duty cycle results in reduced pulse duration. Multi-objective optimization is performed to determine the optimal process parameter settings for desired quality characteristics, considering minimum hole taper angle, precise inlet diameter, and maximum inlet circularity of the hole as optimization criteria. The findings show that with the optimized predicted results obtained from the optimal input variables, a composite desirability of 92% can be achieved.

Exploring AZ31B magnesium alloy for innovative micro products by reverse-μEDM

• Fabrication feasibility test for arrayed microprotrusions of AZ31B Mg alloy. • The arrayed microprotrusions are in elliptical and aerofoil cross-sections. • Exploring Reverse-µEDM integrated with Laser beam µ-machining for this purpose. • Analysing surface finish, migration of tool materials to workpiece and MRR. Fabrication of complex and filigree magnesium alloy 3D-medical implants is very difficult by conventional processes. The present work examines the feasibility of fabricating arrayed microstructures (protrusions) of magnesium AZ31B Mg alloy in unconventional profiles. For this, Reverse-µEDM integrated with laser beam micromachining (LBµM), as a new hybrid technology, is employed. A capacitance of 10 nF, a voltage of 110 V and a feed rate of 10 µm/min for Reverse-µEDM led to better machining responses in terms of materials removal rate, tool wear, and avg. surface roughness compared to other parametric settings. Considering the importance of the biocompatibility of materials, the surface integrity of the fabricated microstructures is also analyzed.

Effect of process parameters on the laser microdrilling performance of stainless steel, aluminium and copper

Micromachining techniques are being used regularly in various engineering and production sectors such as Micro Electromechanical Systems, Aerospace, Automotive, Electronics and Biomedical industries. For Laser Beam Micromachining, highly energized laser beam is focused on a small region of the workpiece surface. As a result, it is heated up rapidly to sufficiently high temperatures, then the material starts to melt and/or vaporize from the surface. This phenomenon of material removal is called laser ablation. The holes that are produced by one-dimensional laser beam drilling (LBD) can come with defects like taper, heat affected zone (HAZ) and Recast Layer. On the other hand, LBD process offers high control, high efficiency, precision, and production rate, particularly for drilling microscopic holes in a variety of materials. LBD performance is measured on different parameters such as taper and recast layer of the machined holes. Previous studies report many observations regarding the performance parameters and the process input parameters. But a thorough study of the performance parameters with respect to different material properties has not been reported yet. The research work for this paper focuses on the experimental investigation for different materials such as stainless steel (type SS304), Aluminum and Copper to observe the effects of Laser input parameters (namely laser power, scanning speed, and pulse repetition rate) on the performance of the LBD. The study also considers different thermophysical as well as optical properties such as thermal conductivity, specific heat, melting point, absorptivity and how it affects the outcome of LBD in a combined manner. Characterization of different output parameters such as Entry area, Exit Area and Recast Area is done by SEM (Scanning Electron Microscope) machine. For 75 Loop count, 90% Laser Power, 950 mm/s Scanning Speed and 10kHz pulse repetition rate, the highest amount of Recast Area is observed in SS, valued at 0.053 mm2. The largest amount of taperness is found in Cu at 44.404°. Scanning Speed and Laser Power has been identified as the most significant process factors for LBD performance.

Laser Micromachining in Fabrication of Reverse-µEDM Tools for Producing Arrayed Protrusions.

This paper focuses on the fabrication of high-quality novel products using a µEDM process variant called Reverse-µEDM. The tool plate required for the Reverse-µEDM is fabricated using Nd: YAG-based laser beam micromachining (LBµM) at the optimized process parameters. The Grey relation analysis technique is used for optimizing LBµM parameters for producing tool plates with arrayed micro-holes in elliptical and droplet profiles. Titanium sheets of 0.5 mm thickness were used for such micro-holes, which can be used as a Reverse-µEDM tool. The duty cycle (a combination of pulse width and frequency) and current percentage are considered as significant input process parameters for the LBµM affecting the quality of the micro-holes. A duty cycle of 1.25% and a current of 20% were found to be an optimal setting for the fabrication of burr-free shallow striation micro-holes with a minimal dimensional error. Thereafter, analogous protrusions of high dimensional accuracy and minimum deterioration were produced by Reverse-µEDM using the LBµM fabricated tool plates.

Dual-stage artificial neural network (ANN) model for sequential LBMM-μEDM-based micro-drilling

A sequential process combining laser beam micromachining (LBMM) and micro electro-discharge machining (μEDM) for the micro-drilling purpose was developed to incorporate both methods’ benefits. In this sequential process, a guiding hole is produced through LBMM first, followed by μEDM applied to that same hole for more fine machining. This process facilitates a more stable, efficient machining regime with faster processing (compared to pure μEDM) and a much better hole quality (compared to LBMMed holes). Studies suggest that strong correlations exist between the various input and output parameters of the sequential process. However, a mathematical model that maps and simultaneously predicts all these output parameters from the input parameters is yet to be developed. Our experimental study observed that the μEDM finishing operation’s various output parameters are influenced by the morphological condition of the LBMMed holes. Hence, an artificial neural network (ANN)-based dual-stage modeling method was developed to predict the sequential process’s outputs. The first stage of the dual-stage model was utilized to predict various LBMM process outputs from different laser input parameters. Furthermore, in the second stage, LBMM-predicted outputs (such as pilot hole entry area, exit area, recast layer, and heat-affected zone) were used for the final prediction of the sequential process outputs (i.e., machining time by μEDM, machining stability during μEDM in terms of short circuit/arcing count, and tool wear during μEDM). The model was evaluated based on the average RMSE (root mean square errors) values for the individual output parameters’ complete set data, i.e., μEDM time, short circuit/arcing count, and tool wear. The values of average RMSE for the parameters as mentioned earlier were found to be 0.1272 (87.28% accuracy), 0.1085 (89.15% accuracy), and 0.097 (90.3% accuracy), respectively.

Effect of laser parameters on sequential laser beam micromachining and micro electro-discharge machining

Laser beam micromachining (LBMM) and micro electro-discharge machining (μEDM) based sequential micromachining technique, LBMM-μEDM, has drawn significant research attention to utilize the advantages of both methods, i.e., LBMM and μEDM. In this process, a pilot hole is machined by the LBMM, and subsequently finishing operation of the hole is carried out by the μEDM. This paper presents an experimental investigation on the stainless steel (type SS304) to observe the effects of laser input parameters (namely, laser power, scanning speed, and pulse frequency) on the performance of the finishing technique, that is, the μEDM in this case. The scope of the work is limited to 1-D machining, i.e., drilling microholes. It was found that laser input parameters mainly scanning speed and power influenced the output performance of μEDM significantly. Our study suggests that if an increased scanning speed at a lower laser power is used for the pilot hole drilling by the LBMM process, it could result in significantly slower μEDM machining time. On the contrary, if the higher laser power is used with even the highest scanning speed for the pilot hole drilling, then μEDM processing time was faster than the previous case. Similarly, μEDM time was also quicker for LBMMed pilot holes machined at low laser power and slow scanning speed. Our study confirms that LBMM-μEDM-based sequential machining technique reduces the machining time, tool wear, and instability (in terms of short circuit count) by a margin of 2.5 x, 9 x, and 40 x, respectively, in contrast to the pure μEDM process without compromising the quality of the holes.

Oxidation of Biocompatible Graphite–Ti Composite after Laser Ablation in Different Atmospheres

The field of biocompatible material surfaces is a widely researched topic. Surface energy, surface topography and surface chemistry are important properties of biocompatible surfaces. These properties contribute to better osseointegration and adhesion of cells to implant surfaces. This article investigates the chemical and phase composition of the surface of a new titanium composite produced by powder metallurgy. Surface oxidation of the graphite– titanium metal matrix composite (TiMMC) after laser beam micromachining (LBMM) is discussed in this paper. Laser micromachining was performed in an argon shielding atmosphere and air. The aim was to determine the influence of the shielding atmosphere and the input parameters of LBMM on the presence of oxygen on the surface. Laser-treated surfaces were examined with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The phase composition was analysed with X-ray diffraction (XRD). Experiments confirmed that an argon shielding atmosphere reduces surface oxidation. The oxidation was also affected by the energy of the laser beam acting on the material. The maximum amount of oxygen detected on the surface after LBMM in air and argon was 38.6 wt. % and 24.2 wt. %, respectively. The presence of TiO, TiO2 and Ti2O3 oxides were detected on the surface after laser ablation in air. In contrast, Ti2O3 and TiO oxides were detected after laser ablation in the argon shielding atmosphere.

Rheological study of the developed medium and its correlation with surface roughness during abrasive flow finishing of micro-slots

Abrasive flow finishing (AFF) is an advanced finishing process employed for finishing macro- to micro-features of workpieces. Finishing improves the functioning of the components by reducing their surface roughness. AFF process uses a polymer-based flexible medium containing abrasive particles as a finishing tool. Medium used during the AFF process plays a vital role in deciding the final surface roughness on the workpiece surface. It is the medium properties in combination with AFF input parameters that decide the end surface roughness. Micro-features on the components are mostly machined with the help of processes involving thermal energy (electrical discharge micro-machining, laser beam micro-machining). This leads to the formation of hard recast layer on the micro-machined workpiece surface. Component size and hardness of the recast layer possesses a great challenge to the finishing processes. In the current article, an economic viscoelastic medium is developed for the finishing of micro-features and its detailed rheological study is carried out. Later, experimental study of the AFF process during the finishing of micro-slots (440 ± 10 µm width) in surgical steel is performed. Developed medium successfully finishes the micro-slots with an initial surface roughness of 3.54 µm to a final surface roughness of 0.21 µm (94.07% reduction in surface roughness).

Effects of Laser Fluence and Pulse Overlap on Machining of Microchannels in Alumina Ceramics Using an Nd:YAG Laser

The quality of micro-features in various technologies is mostly affected by the choice of the micro-fabrication technique, which in turn results in several limitations with regard to materials, productivity, and cost. Laser beam micro-machining has a distinct edge over other non-traditional methods in terms of material choices, precision, shape complexity, and surface integrity. This study investigates the effect of laser fluence and pulse overlap while developing microchannels in alumina ceramic using an neodymium-doped yttrium aluminum garnet (Nd:YAG) laser. Microchannels 200 µm wide with different depths were machined using different laser peak fluence and pulse overlap (percentage of overlap between successive laser pulses) values. It was found that high pulse overlaps and fluences should be avoided as they give rise to V-shaped microchannels i.e., 100% bottom width errors. The optimal peak fluence range was found to be around 125–130 J/cm2 corresponding to 3–5 µm depth per scan. In addition, channels fabricated with moderate pulse overlap were found to be of good quality compared to low pulse overlaps.

A Study of Laser Micromachining of PM Processed Ti Compact for Dental Implants Applications.

The paper deals with the experimental study of laser beam micromachining of the powder metallurgy processed Ti compacts applying the industrial grade fibre nanosecond laser operating at the wavelength of 1064 nm. The influence of the laser energy density on the surface roughness, surface morphology and surface elements composition was investigated and evaluated by means of surface roughness measurement, scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. The different laser treatment parameters resulted in the surfaces of very different characteristics of the newly developed biocompatible material prepared by advanced low temperature technology of hydride dehydride (HDH) titanium powder compactation. The results indicate that the laser pulse energy has remarkable effects on the machined surface characteristics which are discussed from the point of view of application in dental implantology.

Complex Micro Machining of an Injection Mold Surface for a Conductive Polymeric Composite Product

Hydrogen and fuel cell technologies were identified amongst new renewable energy technologies which contribute strongly to mitigating climate change. Important research activities were directed to the injection molded bipolar plates made by conductive polymeric composites. The mold surface quality can help obtaining better conductivity. In this paper are presented the experiments regarding complex micro-machining of the surfaces of an injection mold for a conductive polymeric composite product by micro-milling and for finishing and cleaning by laser beam micro-machining. The laser ablation consists in removing material from a solid surface by irradiating it with a laser beam, in successive layers in order to achieve complex geometries with accuracy of about micrometres. Injection moulding experiments evidenced the very good replication of the micro-machined surface pattern.

Laser Beam Micromachining of Metals: A Review

Abstract Laser Beam Micromachining has revolutionized the industrial world by providing a better solution for machining the materials at micro level. LBMM has a wide application in these days because of its precise machining capability. In this paper, an overview of LBMM of metals is given so that an idea can be obtained about the process. The use of various type of laser and previous researches have been studied in this paper. The effect of various parameters like fluence energy, wavelength, pulse rate, threshold fluence and pulse frequency have been studied. In previous researches, it was observed that these parameters effect the geometries, morphology, machining speed, scanning speed and machining efficiency and many other characteristics of the material to a great extent which have been studied in this paper.

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.

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 investigations of nanosecond-pulsed Nd:YAG laser beam micromachining on 304 stainless steel

The demand for miniaturized components is increasing day by day as their application varies from industry to industry such as biomedical, micro-electro-mechanical system and aerospace. In the present research work, high-quality micro-channels are fabricated on 304 stainless steel by laser beam micromachining process with nanosecond Nd:YAG laser. The laser pulse energy (LPE), scanning speed (SS) and scanning pass number (SP No.) are used as the process parameters, whereas the depth and width of the kerf as well as the surface roughness are used to characterize the micro-channels. It is found that the kerf depth, width and surface roughness decrease with increase in the SS. The kerf depth sharply increases with increase in the SP No. The kerf width is minimum at 30 mJ LPE, 400 µm s‒1 SS and 10 SP No. The minimum surface roughness is observed at 30 mJ LPE, 500 µm s‒1 SS and 10 SP No. The oxygen content is found to gradually decrease with the distance from the centre of the micro-channel. Based on the experimental results, optimized input parameters can be offered to control the micro-channel dimensions and improve their surface finish effectively on stainless steel.

Extended focus depth for Gaussian beam using binary phase diffractive optical elements.

A novel technique to improve the focus depth of a Gaussian beam is presented in this paper. The improvement is based on two-step beam shaping using a cascade of binary phase diffractive optical elements (BPDOEs). The first BPDOE transforms the incident Gaussian beam into a high-order radial Laguerre-Gaussian beam (LGp0). Then the second BPDOE rectifies the obtained LGp0 beam and gives rise to a quasi-Gaussian one in the focal plane of a converging lens. This resulting quasi-Gaussian beam exhibits a lower divergence and larger focus depth compared to the pure Gaussian beam having the same beam waist. These results open new possibilities in laser beam manufacturing and micromachining, and in applications that need an extended focus depth.

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.

Fabrication of micro-features on 304 stainless steel (SS-304) using Nd:YAG laser beam micro-machining

In the present study, micro-channels and micro-dimples are fabricated with different dimensions on the surface of SS-304 alloy by pulsed Nd:YAG laser beam micro-machining. The effect of various laser parameters on the machining performance characteristics is evaluated. The effect of process parameters viz. laser scanning speed, current, laser pulse frequency and pulse duration are studied using argon gas. The width or diameter and depth of micro-features are considered as the output responses. 3D laser surface profilometer is used to study and measure the dimensions of fabricated micro-features. The results showed that the selection of micro-feature size is critical to achieve desired machining results. All the processing parameters have noticeable effect on the geometry and quality of micro-features. The dimensions (diameter, width and depth) of micro-features are decreased with higher scanning speed and increased with increase in pulse frequency, pulse duration as well as current. The appropriate combination of parameters can yield the better results for quality and size of micro-features. Lower scanning speed with higher pulse frequency with a proper set of current and pulse duration can be used in order to fabricate micro-channel, whereas higher scanning speed and lower pulse frequency can be used to obtain micro-dimples.

Fabrication of micro-features on 304 stainless steel (SS-304) using Nd:YAG laser beam micro-machining

Fabrication of micro-features on 304 stainless steel (SS-304) using Nd:YAG laser beam micro-machining