Laser Micromilling Research Articles

Parametric Analysis and Optimization on Fiber Laser Micro-Milling on AZ31 Magnesium Alloy

One of the proficient machining technologies to create micro-features in a variety of materials is the laser micro-milling process. This procedure involves irradiating a highly concentrated laser beam on the sample and performing laser cutting at various cutting patterns to change the surface conditions and enhance the characteristics of that surface tribology. In this work, an effort has been made to mill magnesium alloy (AZ31) material using a laser. The pulse frequency, laser beam power, cutting speed, number of passes, and transverse feed are among the different process variables taken into account for the current research effort. Measured results include depth of cut and surface roughness. To ensure the validity of the established empirical models, this paper also presents experimental data. Several surface plots have been used to examine the test data. To get the lowest values of surface roughness and depth of cut, multiperformance optimization is also utilized. The influence of process factors on response has also been examined using optical microscopic images. Gray relational analysis approach is also applied to obtain the multiobjective optimization parametric combination and based on the calculated results of gray relational grade, it is revealed that improvement in the value of gray relational grade at predictive setting is 0.054 compared to the initial parametric combination.

A numerical and experimental analysis of CO2 laser micro-milling on PMMA sheet considering a multipass approach for microfluidic devices

Laser-assisted machining is an advanced manufacturing process that provides excellent cutting quality, flexibility, and precision. The current study used a CO2 laser to create microchannels in polymethyl methacrylate (PMMA) sheets using a series of laser passes by varyingparameters such as laser power (30–40 Watt), number of passes (1–4), and cutting speed (20–25 mm/s). A finite element analysis is performed using ABAQUS with subroutines such as Distributed Flux (DFLUX) and User Defined Field (USDFLD) to simulate and predict the upper and lower kerf width, kerf angle, and heat-affected zone (HAZ) during the process. Thermal analysis has been performed by considering the laser beam as body heat flux with a moving heat source. It has been observed that the HAZ tends to reduce with the increase of laser cutting speed. During the laser cutting process, the upper kerf width is found to increase with increasing laser power, as well as with increasing the number of passes at a given laser power and cutting speed. It is also predictedthat when laser cutting speed increases, the kerf width for a given laser power decreases. The experimental and simulation results are in good agreement and the results demonstrated thatthe average percentage error in HAZ, kerf angle,upper kerf, and lower kerf width was 3.21 %, 5.06 %, 7.60 %, and 22.2 %, respectively. The results of this study have significance for the advancement of precise and state-of-the-art manufacturing for application in microfluidic devices.

Thermal Conductivity Gas Sensors for High-Temperature Applications.

This paper describes a fast and flexible microfabrication method for thermal conductivity gas sensors useful in high-temperature applications. The key parts of the sensor, the microheater and the package, were fabricated from glass-coated platinum wire and the combination of laser micromilling (ablation) of already-sintered monolithic ceramic materials and thick-film screen-printing technologies. The final thermal conductivity gas sensor was fabricated in the form of a complete MEMS device in a metal ceramic package, which could be used as a compact miniaturized surface-mounted device for soldering to standard PCB. Functional test results of the manufactured sensor are presented, demonstrating their full suitability for gas sensing applications and indicating that the obtained parameters are at a level comparable to those of standard industrially produced sensors. The results of the design and optimization principles of applied methods are discussed with regard to possible wider applications in thermal gas sensor prototyping in the future. The advantage of the developed sensors is their ability to operate in air environments under high temperatures of 900 °C and above. The sensor element material and package metallization were insensitive to oxidation compared with classical sensor-solution-based metal-glass packages and silicone MEMS membranes, which exhibit mechanical stress at temperatures above 700 °C.

Experimental investigations and modeling for multi-pass laser micro-milling by soft computing-physics informed machine learning on PMMA sheet using CO2 laser

Laser micro-machining has gained significant attraction from industries and researchers due to the wide range of processability and material flexibility with micro-scale accuracy. However, only a few process variables and soft computing approaches are taken into consideration in micro-scale sectors. This provides the opportunity to explore a new and relatively unexplored area of physics-informed advanced soft computing techniques for laser beam machining. This study aims to develop a framework to investigate the micro-milling capabilities of 10 mm thick poly-methyl-methacrylate (PMMA) using various input parameters such as laser power (8–16 W), scanning speed (25–50 mm/s), number of passes (2–6), and incident energy (0.107–0.64 J/mm). A soft computing technique to build depth, width and surface roughness prediction models on a CO2 laser machine, is presented. Advanced soft computing approaches such as random forest, gradient boost, ridge regression, linear regression, support vector regression and gaussian process regression are evaluated to predict the microchannel's depth, surface roughness, and kerf width. The proposed work is validated experimentally and compared with the different prediction/regression models available in the literature. The values of hyper tuning parameters are optimized using by grid search method. Based on the 5-fold cross-validation analysis, the most accurate predictions of the depth, surface roughness and kerf width could be achieved through the gaussian process regression (GPR) model with highest accuracy of 98.34 %, 97.68 % and 96.38 % for depth, surface roughness and kerf width respectively.

Hybrid laser and micro milling methods for higher depth microchannel fabrication

The performance of microchannels is dependent on the geometry, dimensions and surface quality. The most widely used methods for manufacturing microchannels are laser micro-milling (LMM), conventional micro-milling (CMM), micro-forming, and chemical etching. The main challenges in manufacturing microchannels with LMM are non-uniform dimensions, tapering effect, and low aspect ratio. In addition to that, tool wear and burrs formation on the top surface of channels are common challenges in conventional micro milling (CMM) techniques. In the present study, Hybrid micro milling techniques have been proposed to manufacture the better quality of micro-channels. The proposed methods include the application of laser and conventional micro milling in two approaches; laser pre-channel micro milling (LPCMM) and laser assisted sequential micro milling (LASMM). In the LPCMM approach, a pre-channel was fabricated by LMM followed by CMM, whereas in LASMM, the material was removed layer by layer by LMM followed by CMM. The proposed methods were compared with CMM considering cutting forces, surface finish, top burrs, tool morphology and flank wear as responses. As compared to CMM, results revealed that the hybrid methodologies mean down burr width decreased by 75 % and 20 %; mean up burr width reduced by 81 % and 20 %; and cutting force decreased by 24 % and 60 % in LASMM and LPCMM, respectively. However, surface roughness (Sa) increased by 7.5 % and 32 % in LASMM and LPCMM, respectively, because of the thermal effect of the laser beam on the fabricated channels.

Experimental Investigation on Dimensional Characteristics and Surface Morphology of Microchannels Fabricated on Smart Ceramic by DPSS Nd:YAG Laser

Smart ceramic material like barium titanate (BaTiO3) is in high demand in today's highly competitive precision industries; as it has numerous applications in electronic, biomedical, and aerospace engineering.In this endeavor, laser micro-milling approach (LMMA) hasbeenattempted with a suitable experimental design plan; to scrutinize the laser influencing variables against the LMMA outcomes during the processing of BaTiO3 throughout the fabrication of microchannels. This article presents an investigational act on the fabricated micro-channels to discern the impacts of LMMA parameters (gas pressure, scan strategy, current and scanning speed) against the dimensional (like deviations in channel upper and lower width) and surface characteristics of the surface feature. The surface morphology study hasbeen accomplished with the support of energy dispersive spectroscopy (EDS) in conjunction with scanning electron microscope (SEM) to scrutinize the elemental alterations and surface characteristics at the zone of laser ablation. A statistical multi-objective optimization (MOO) technique known as grey relational analysis (GRA) has beenused later in this paper to predict an optimal parametric setting. The MOO results’ efficacy has been validated further in the corroboration assessments, the predicted optimal solutions have been obtained with an error of 4.57 %, 3.89 % and 4.88 % for W-RCL, LWD and UWD respectively.

Combination of Ceramic Laser Micromachining and Printed Technology as a Way for Rapid Prototyping Semiconductor Gas Sensors.

The work describes a fast and flexible micro/nano fabrication and manufacturing method for ceramic Micro-electromechanical systems (MEMS)sensors. Rapid prototyping techniques are demonstrated for metal oxide sensor fabrication in the form of a complete MEMS device, which could be used as a compact miniaturized surface mount devices package. Ceramic MEMS were fabricated by the laser micromilling of already pre-sintered monolithic materials. It has been demonstrated that it is possible to deposit metallization and sensor films by thick-film and thin-film methods on the manufactured ceramic product. The results of functional tests of such manufactured sensors are presented, demonstrating their full suitability for gas sensing application and indicating that the obtained parameters are at a level comparable to those of industrial produced sensors. Results of design and optimization principles of applied methods for micro- and nanosystems are discussed with regard to future, wider application in semiconductor gas sensors prototyping.

Neural network-based prediction for surface characteristics in CO2 laser micro-milling of glass fiber reinforced plastic composite

Neural network-based prediction for surface characteristics in CO2 laser micro-milling of glass fiber reinforced plastic composite

Ceramic packages prototyping for electronic components by using laser micromilling technology

The use of adaptive laser micromilling technology for the fast prototyping ceramic package of electronic components in a miniature surface mount form factor (SMD) is describing. Current experimental results and practical evaluation of one show that using the developed software and hardware is possible successfully producing SMD packages starting from the SOT-723 form-factor in the direction of larger overall dimensions to SOT-475 form-factor. Also discussed are the limiting physical factors arising in the course of the application of laser micromilling technology, which affect the production speed and quality of the resulting product from monolithic ceramics.

Underwater laser micro-milling of fine-grained aluminium and the process modelling by machine learning

Nanosecond-pulsed laser ablation is often accompanied by adverse thermal effects, such as oxidation, debris recast and burr formation. To reduce these effects, in this paper, the authors present the underwater laser milling process using RSA-905 fine-grained aluminium as the target material for the first time. The results show that channels up to 200 μm in width, 700 μm depth and bottom roughness around 1 µm Ra could be fabricated with reduced thermal effects. By conducting multi- and single-factor experiments, empirical models relating the laser processing parameters to the key dimensions of channels were derived using an artificial neural network algorithm and polynomial regression, and the models’ accuracies were evaluated. Based on the models, the cross-section profile of a channel subject to a given set of processing parameters can be predicted. The process can serve as a pre-treatment technique in mechanical milling such that the tool life will be extended and the profile of a desired feature can be precisely defined.

Microchannel fabrication and metallurgical characterization on titanium by nanosecond fiber laser micromilling

ABSTRACTLaser micromilling technique is used to manufacture microchannel on metals and nonmetals. Microfeatures ≤100 µm are still challenging for fabrication by common methods. Nanosecond fiber laser micromachining has become more popular owing to its prospective implementation in laser micromilling. Microchannel application relies on its geometric dimension, profile, and surface quality. In this study, an attempt was made to explore the impact of process parameters scanning times, scanning velocity, pulse repetition rate, and assist gas pressure on top kerf width, taper, surface roughness, and metal removal rate in laser micromilling experimentally. Microchannel width varied between 45.5 and 70.9 µm. A regression model has been developed for each response. ANOVA (analysis of variance) has been carried out to remove insignificant parameters. Thermal stress analyzed by surface cracks inside microchannel by Scanning Electrone Microscopy (SEM) images. Higher PRR, lower no. of scans, higher scanning speed and high air pressure found suitable for lesser surface cracks. Redeposition observed at slower scanning velocity and minimum scanning times. Oxidation zone from boundary of channel varies between 37 and 58 µm. Oxide formed on Ti surface which increases oxygen content toward center of channel from 51.08 to 76.22% compared to outside surroundings.

Improvement of Field Effect Capacity Type Gas Sensor Thermo Inertial Parameters by Using Laser Micromilling Technique

This paper presents a verification of technology aspects for improvement of field effect capacity type gas sensor parameters by using laser micromilling technique for fabrication ceramic surface mounting device (SMD) package and microheater for sustentation working temperature of metal-insulator-semiconductor structure (MIS structure). Innovative claims include: demonstration of flexible opportunities for new digital fabrication process flows based on laser micromilling tech: fast design of SMD sensor 3-D model, flexible changing topology of microheater, thick and thin film technology combination for reducing of power consumption. The results show possibility to fast fabrication functional sensor in customer ceramic SMD package with base 9x9 mm with twice reduced power consumption and improving mechanical properties compare with classical metal-glass microelectronic packages using before for such type sensors.

Parameter Studies of Ceramic MEMS Microhotplates Fabricated by Laser Micromilling Technology

This paper presents a modeling of technology aspects for fabrication ceramic microelectromechanical systems (MEMS) microhotplate and surface mounting device (SMD) packaging for (MOX) gas sensors applications. Innovative claims include: demonstration of flexible opportunities for new fabrication process flows based on laser micromilling tech; modeling of power consumption MEMS microhotplate depending on the thickness and topology; demonstration of necessity changing thick film technology of metallization to vacuum sputtering by reducing of power consumption. The results show possibility to fast fabrication of different topologies for ceramic MEMS microhotplate in form-factor of SOT-23 type SMD package.

Technology of SMD MOX Gas Sensors Rapid Prototyping

This work discusses the design of flexible laser micromilling technology for fast prototyping of metal oxide based (MOX) gas sensors in SMD packages as an alternative to traditional silicon clean room technologies. By laser micromilling technology it is possible to fabricate custom Micro Electro Mechanical System (MEMS) microhotplate platform and also packages for MOX sensor, that gives complete solution for its integration in devices using IoT conception. The tests described in the work show the attainability of the stated results for the fabrication of microhotplates.

Using Field-Effect Gas Sensors for Monitoring H2 in Transformer Oil

Hydrogen can be released during the thermal decomposition of organic materials, therefore, monitoring its level in the working industrial high-voltage transformer oil allows you to identify the development of degenerative processes in advance, because these processes can lead to an accident in the future. In experiments has shown that highly sensitive and small-sized field effect gas sensor based on the metal-insulator-semiconductor structure can be used for measuring of Hydrogen in oil with direct contact of its structure with transformer oil. Given the harsh environmental conditions of hydrogen measurement the field effect capacity type gas sensor were fabricated by using laser micromilling technique for fabrication compact ceramic surface mounting device package and microheater for sustentation working temperature of metal-insulator-semiconductor structure.

Laser Micromilling Technology as a Key for Rapid Ceramic MEMS Devices

The flexible laser micromilling technology for ceramic MEMS production of microhotplates in the surface mount device (SMD) package is described. Current results demonstrate that using described technology makes it possible to manufacture all parts of MEMS sensor in the SMD with form factor of SOT-23 package type.

Prediction model of the depth of the femtosecond laser micro-milling of PMMA

The femtosecond laser technology is emerging as a powerful and flexible tool for the fabrication of miniaturized polymeric devices, thanks to the micrometric precision and the minimum thermal damage on the workpiece obtainable through ultrafast laser ablation. However, parametrization of femtosecond laser processes is often based on a trial and error approach, which requires a lot of expensive experimental efforts. The design of experiment (DoE) approach can offer a methodical way to quickly determine the laser process settings limiting the use of resources. In this work, we define an accurate DoE procedure to estimate the influence of the laser repetition rate, pulse energy, scanning speed, and hatch distance on the fs-laser micromilling process of PMMA specimens in terms of depth of removed material (Dh). We show that the laser pulse energy is the parameter that mainly affects the milling depth. A predictive model describing the relationship between the response variable depth and the main laser parameters is defined and then validated.

Direct laser writing to fabricate capacitively transduced resonating sensor

This article reports on laser technology based fabrication approach to develop a micro-size capacitive gap based transducer useful for a variety of applications. A low-cost prototype has been fabricated via a rapid and advanced laser micro-milling technique to achieve a parallel kerf-width (capacitive gaps) of about 60 µm into a piece of aluminum and a stainless steel each of 1 and 2 mm thickness, respectively, thus leading to a high-aspect ratio (> 33) structure. A device is demonstrated to facilitate actuation via electrostatic means and sense a capacitive change across its electrode. Experiments have been performed with a structure made of aluminum. Results comprising analytical modeling, fabrication, and electrical characterization are presented. An applicability of a device as a two degree-of-freedom resonating mode-localization sensor that employs a weak electrostatic coupling is demonstrated to offer vibration amplitude based sensitivity to a relative change in the stiffness. This sensor is able to resolve a minimum stiffness perturbation (normalized), $$\delta_{{k_{\rm{min} } }} = \frac{\Delta k}{{K_{eff} }}$$ of the order of 7.98 × 10−4.

Thermal and hydraulic performance of micro pin fin heat sinks with different pin fin shapes

Efficient cooling of high heat flux devices has promoted the development of micro pin fin heat sinks. In this study, four micro pin fin heat sinks (MPFHSs) with different pin fin shapes, i.e., circular, square and diamond and streamline ones are fabricated by laser micromilling methods. Their single-phase heat transfer and fluid flow performance are explored to assess the pin fin shape effect. Convective flow tests are conducted at Reynolds number of 150-750 at two heat fluxes using deionized water as the coolants. It was found that the streamline MPFHS presented the best heat transfer performance. On the contrary, the diamond fin pin heat sink presented the worst heat transfer performance, whereas it featured the smallest pressure drop among the four MPFHSs. The diamond micro pin fins showed the smallest thermal resistance at a certain pressure drop, and should be selected as the optimum one for the MPFHS applications when the overall thermal and hydraulic performance is considered.

Effect of Laser Beam Conditioning on Fabrication of Micro-Channels in Al2O3 Bio-ceramics Using Nd:YAG Laser

In the present study, laser micro-milling tests were carried out to fabricate micro-channels on Alumina bio-ceramics (Al2O3), using a Q-Switched 30W Nd:YAG pulsed laser. A systematic approach based on a full factorial Design of Experiment (DoE) has been successfully applied with the aim to detect which and how the key input laser process parameters affect the channel dimensional accuracy. The examined process parameters were the laser beam scanning speed, the pulse frequency and the pulse intensity. Optical microscope was used to analyze the channel geometries responses (i.e. channel's top width, bottom width, depth, and taper wall angle). Moreover, mathematical models for predicting the micro-channel geometries are successfully proposed for controlled micro-milling of micro-channels in Al2O3. Results reveal that, the change of scanning speed and laser intensity significantly affected the ablated channel’s geometries. Further it is observed that the channel depth and width increase linearly with increasing of laser intensity and decreasing of scanning speed and not much affected by changing of pulse frequency. Finally, the experimental results bear a good agreement with the proposed prediction models.