Laser Machining Research Articles

A New Compact Wideband Filter Based on a Coupled Stepped Impedance Resonator.

A new compact wideband filter is introduced to address the requirements of recent communication and radar systems. The filter is based on a quarter-wavelength short-circuit coupled stepped impedance resonator (SIR). The analytical solution shows that the suggested SIR resonator provides a compact size and a wide stopband response, which are essential features in many wireless communication systems. The analytical results also reveal that increasing the impedance ratio of the SIR extends the stopband by increasing the first spurious response and reducing its total length. A compact two-coupled short-circuit SIR filter is designed at 1.23 GHz. The design approach is validated using an ideal transmission line modeling analysis and electromagnetic simulation using CST Microwave Studio 2021. The proposed structure is shown to be flexible, allowing the achievement of a relative bandwidth as low as 5% and as high as 50%. A four-resonator filter is designed by cascading two stages of the designed two-coupled short-circuit SIR filter, which are coupled through a quarter-wavelength line. The simulation results illustrate that the suggested structure can be used to design a filter with any number of resonators. The filter is implemented using a high-resolution LPKF laser machine on Rogers RT/duroid 6010.2LM material with a thickness of 0.635 mm. From the measurements, the bandwidth is found to be 390 MHz and centered at 1325 MHz (29.4% relative bandwidth) and the insertion loss is 1.3 dB. The simulation and experimental results verify the proposed approach and indicate the potential of this component in meeting the design requirements of next-generation microwave circuits related to flexibility and size-compactness.

Controlling nonlinear collapse of ellipticity and orientation of a co-variant vector optical field.

A vector optical field with inhomogeneous spatial polarization distribution offers what we believe to be a new paradigm to form controllable filaments. However, it is challenging to steer multiple performances (e.g. number, orientation, and interval) of filaments in transparent nonlinear media at one time. Herein, we theoretically self-design and generate a kind of believed to be novel ellipticity and orientation co-variant vector optical field to interact with Kerr medium to solve this issue. The collapsing behaviors of such a new hybrid vector optical field reveal that, by judiciously adjusting the inherent topological charge and initial phase of incident optical field, we are able to give access to stable collapsing filamentation with tunable numbers, orientations and interval. Additionally, the collapsing patterns presented are immune nearly to the extra random noise. The relevant mechanism behind the collapse of the vector optical field is elucidated as well. The findings in this work may have huge potential in optical signal processing, laser machining, and other related applications.

Fabrication of polycrystalline diamond micro-milling cutter with different grain sizes by picosecond laser

Polycrystalline diamond (PCD) is an excellent material for machining micro-tools due to its high hardness and wear resistance. However, the diameter of micro-milling tools is generally required to be less than 500 μm. When preparing micro-milling tools with a large aspect ratio, the processing load introduced by traditional grinding methods is easy to cause tool fracture. Therefore, a composite structure of carbide tool holder and diamond tool head is proposed in this paper. A technique of picosecond laser machining PCD micro-milling tool was studied, and the overall manufacturing process of tool blank preparation, nanosecond laser roughing and picosecond laser finishing was formed. A two-dimensional ablation mathematical model for tangential machining of PCD with a multi-pulse picosecond laser was established, and experiments verified the reliability of the mathematical model. In addition, the effects of picosecond laser pulse pitch, pulse energy, and track spacing on the surface quality of PCD materials with different particle sizes and cutting edge radius were studied by orthogonal experiments. The results showed that after picosecond laser processing, the surface roughness (Sa) of PCD with a particle size of 2 μm was the best, which can reach 0.33 μm, and the cutting edge radius of PCD micro-milling tool with a particle size of 25 μm was the smallest, which can get 1.67 μm. Using the optimized picosecond laser parameters, the high-sharpness single-edge micro-milling cutters with different particle sizes PCD with a diameter of 100 μm, aspect ratio greater than 3, and a cutting edge radius less than 3 μm were successfully fabricated.

A combined approach of artificial neural network, multi-objective genetic algorithm, and response surface methodology for enhanced PMMA micro-channeling in low power fiber laser beam machining

The most cost-effective approach for generating micro-channels on polymethyl methacrylate (PMMA), a polymer highly sought after in the biomedical industry, is by employing laser technology. The study aims to evaluate the feasibility of utilizing a low-power fiber laser for the purpose of generating micro-channels on PMMA, as well as enhance the data analysis and forecasting of results for implementation in the biomedical sector. This study utilizes response surface methodology (RSM) to conduct experiments by creating micro-channels on PMMA using low-power fiber lasers. Furthermore, a multi-objective genetic algorithm (MOGA) is employed to optimize the responses, namely the cut width and depth, within the predetermined range of process parameters. Moreover, the artificial neural network (ANN) technique is utilized to predict the results of MOGA and RSM. The study encompasses process parameters such as laser power, pulse frequency, scan speed, and number of passes. The ANN is trained using input-output patterns derived from RSM. Three methods are integrated not only to optimize but also to forecast the data set in order to reduce material waste, costs, and increase efficiency. The experimental research shows that the artificial neural network technique has higher prediction accuracy compared to the other two methods. All three strategies utilized in this study have been well aligned with the empirical results for predicting the dimensions of the micro-channels.

Comparison of effect of machine muteness to reduce noise anxiety vs regular settings on patient compliance during pan-retinal photocoagulation.

This Quasi Experimental study was conducted at Major Eye Clinic, Gujranwala, from January to December 2022, to study the effect of muting the sound of Argon Laser machine on patient compliance and the pain felt during pan-retinal photocoagulation (PRP). Eighty patients were included in the study with proliferative diabetic retinopathy (PDR), retinal breaks, lattice and myopic fundus degenerations for which PRP was performed. A total of 80 patients were enrolled, who were divided in two groups with 40 patients in each group. Group A patients received muted machine settings, while group B underwent regular PRP. The mean age was 54.6±3.4 years. Sixty-eight (85%) cases were of PDR, 4 (5%) of retinal breaks, 3 (3.75%) of lattice degenerations associated with breaks, and 5 (6.25%) of laser barrage. In group A, 28 (70%) patients had grade 1 and grade 2 pain score, while in group B, 26 (65%) had grade 3 and grade 4 pain score. It was concluded that by eliminating machine sound, noise anxiety can be greatly reduced ensuring better patient cooperation.

Femtosecond laser induced damage threshold incubation and oxidation in AS2S3 and AS2Se3 thin films

Laser surface structuring has emerged as a versatile technology for precise and localized material processing. When dealing with femtosecond lasers, thermal effects and collateral damage are reduced due to nonlinear light-matter interaction, improving the processing. This study explores the fabrication of microstructures using femtosecond pulses on thin films of chalcogenide glasses, which can be used for photonics applications, such as waveguides, fiber lasers, and photonic crystals. Moreover, the photoinduced changes in chalcogenide glasses have opened up new possibilities in optoelectronics, data storage, and other applications. Femtosecond laser machining of amorphous thin films of As2S3 and As2Se3 using femtosecond laser pulses is investigated through various microscopy techniques and spectroscopy tools, focusing on the impact of incubation effects and controlled photo-oxidation. This research contributes to a deeper understanding of the interaction of ultrafast pulses with chalcogenide glasses, promoting further advancements in photonics and optoelectronic applications.

Automated, real-time material detection during ultrashort pulsed laser machining using laser-induced breakdown spectroscopy, for process tuning, end-pointing, and segmentation.

The rapid, high-resolution material processing offered by ultrashort pulsed lasers enables a wide range of micro and nanomachining applications in a variety of disciplines. Complex laser processing jobs conducted on composite samples, require an awareness of the material type that is interacting with laser both for adjustment of the lasering process and for endpointing. This calls for real-time detection of the materials. Several methods such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-Ray spectroscopy (EDS) can be used for material characterization. However, these methods often need interruption of the machining process to transfer the sample to another instrument for inspection. Such interruption significantly increases the required time and effort for the machining task, acting as a prohibitive factor for many laser machining applications. Laser induced breakdown spectroscopy (LIBS) is a powerful technique that can be used for material characterization, by analyzing a signal that is generated upon the interaction of laser with matter, and thus, it can be considered as a strong candidate for developing an in-situ characterization method. In this work, we propose a method that uses LIBS in a feedback loop system for real time detection and decision making for adjustment of the lasering process on-the-fly. Further, use of LIBS for automated material segmentation, in the 3D image resulting from consecutive lasering and imaging steps, is showcased.

Processing of titanium alloys with improved efficiency and accuracy by laser and electrochemical machining

Processing of titanium alloys with improved efficiency and accuracy by laser and electrochemical machining

Femtosecond laser machining of the novel superhydrophobic microstructure for the oil-water separation

Bionic micro/nano structures with superhydrophobicity is extensively used in oil-water separation. However, the fabrication of such tiny structures involves intricate processes, often requiring additional steps such as chemical or mechanical post-processing. With the development of the laser machining, it is feasible to fabricate structures in micro/nano scale via the ablation of ultrafast laser beam. Inspired by the function of the funnel, a novel through-hole structure was designed and manufactured by femtosecond laser in high dimensional precision. The copper film with the funnel-like through-hole structure exhibited remarkable hydrophobic properties, with a water contact angle of 160 ± 2° and a sliding angle ≤ 5°, facilitating the high-quality and high-efficiency separation of water-oil/organic liquids, compared with the conventional through-hole structures, such as circular or rectangular structures. Furthermore, the prepared film demonstrated exceptional capabilities of anti-freezing, anti-pollution, environmental stability, and versatility, examined by enduring treatments involving acidic liquids, immersion in hot solutions, freezing, and scratching. In sum, this work offers innovative concepts and valuable insights on the design and fabrication of functional structures with ultrafast laser machining.

Effects of pulsed laser processing on structural evolution of diamonds - A molecular dynamics and experimental study

The pulsed laser processing has been used for machining ultrahard diamonds. However, structural evolutions, along with microscopic mechanisms, have hardly been clarified. In the present study, a molecular dynamics model for describing the pulsed laser processing of diamonds was developed, and the calculation results were verified through corresponding experiments, by using the typical nanosecond pulsed laser processing. At first, the temporal evolution of the temperature field was calculated, establishing the correlation between the temperature distribution and material ablation phenomena. Besides, intricacies of dislocation generation mechanism were elaborately explained, indicating that stress waves played prominent roles in formation and propagation of dislocations. In order to understand the phase transition phenomena, including the graphitization, vaporization and solidification, variations in coordination numbers based on calculations, together with Raman and XPS characterizations on diamond samples before and after laser processing, were examined and compared. Moreover, different effects of the pulsed laser processing on polycrystalline and monocrystalline diamonds were compared. It was found that the polycrystalline diamond shows lower rate of temperature fall and lower velocity of stress waves. This study provides valuable insights into the microscopic mechanisms governing pulsed laser processing of diamonds, thereby broadening the scope for optimizing laser machining processes.

Comparison of 2D and 3D measurement methods for evaluating laser structured aluminum surfaces using fractal dimension

The interlaminar strength of mechanically interlocked polymer-metal hybrids is strongly determined by the surface geometry at the interface. To improve the interlaminar strength, laser beam machining is among the most applied technologies for manufacturing a predefined and complex surface structure. Previously, the fractal dimension of interfaces in polymer-metal-hybrids has been introduced as scale-independent measure. It has been correlated quantitatively with the interlaminar strength using values derived from cross-sectional images. Therefore, the quality of the prediction directly depends on the accuracy of the measured surface data. However, a holistic acquisition of surface structure for the determination of the fractal dimension including 3D methods has not been investigated so far. In this study, laser machining was used to generate five different pin-structures on samples of the aluminum alloy EN AW-6082. Surface characterization was realized by light microscopy (2D), laser scanning microscopy (3D) and X-ray microscopy (3D). Subsequently, the fractal dimension was determined using a box-counting algorithm as well as slit-island method. The results show that all methods regarded are appropriate to determine the fractal dimension, but differ in the specific results. The functional characteristics of each method are described in detail and potentials for applications are outlined.

Empirical Modeling and Analysis of Process Parameters in Laser Beam Cutting Process

The research has been originated based on the persuasive applications of Lasers in the field of various engineering industries, i.e., Aerospace, Automobile, Electronic and Heavy manufacturing industries to machine a variety of metals and alloys. Out of all the machining processes available, Laser Beam Machining is considered to be the best one, because of the following advantages, i.e., quick material removal, non-contact, non-wearing tool, involves highly localized heat input to the work piece, reduces distortion, and offers no tool wear, diminishes tendency of cracking. The present paper focused mainly on developing the empirical relationships between the input process parameters and the output responses in Laser beam cutting process. Laser power, Cutting Speed, Gas pressure and Focal distance are the input process parameters. The output responses considered are related to the quality of cut. Surface roughness is the first output responses considered and the second one is Burr height. Total number of experiments carried out is 27 based on the Taguchi Design of Experiments. Haste alloy C276 is the work material. Response Surface Methodology is applied for the Experimental data of 31 samples to derive the empirical relationships. Later ANOVA analysis is also carried out to check the adequacy of the derived equations. Based on the ANOVA analysis, the models are classified as significant or not significant. Further the significant models can be used for optimizing the Laser beam cutting process. Once the process is optimized, it can be automated, so that the process can be run very efficiently and economically.

Machine-learning-enhanced femtosecond-laser machining: Towards an efficient and deterministic process control

Femtosecond laser nanomachining represents a frontier in precision manufacturing, excelling in micro-and nanopatterning across diverse materials. However, its wider adoption is hindered by unintended surface damage or modifications stemming from complex non-linear laser-material interactions. Moreover, traditional effective process optimisation effort to mitigate these issues typically necessitate extensive and time-consuming trial-and-error testing. In this scenario, machine learning (ML) has emerged as a powerful solution to address these challenges. This paper provides an overview of ML’s contributions to making femtosecond laser machining a more deterministic and efficient technique. Leveraging data from laser parameters and both in-situ and ex-situ imaging of processing outcomes, ML techniques—spanning supervised learning, unsupervised learning, and reinforcement learning—can significantly enhance process monitoring, process modeling and prediction, parameter optimisation, and autonomous beam path planning. These developments propel femtosecond laser towards an essential tool for micro-and nanomanufacturing, enabling precise control over machining outcomes and deepening our understanding of the laser machining process.

Dependency of beam diameter on the resistance time of laser guards

Laser manufacturers and users of material processing machines must implement technical protective measures. The assessment of the protective effect of laser guards for use in laser machines with respect to the accessible laser parameters (e.g. beam diameter and irradiance) is currently problematic, as extensive individual resistance time tests are often required. The aim and focus of the project is to determine mathematically representable relationships between beam diameter, irradiance and resistance time for commercially available laser safety shield materials. The functional relationships found should enable the manufacturers and users of lasers to determine the appropriate shielding for the respective application solely on the basis of existing standard tests and without further time-consuming, case-specific tests. A standardized test setup (test box) is being developed to ensure globally uniform laser resistance time tests of shielding materials.

Reducing rubber-plastic friction in syringes through microstructured surface design and manufacturing

Plastic syringes often rely on silicone oil lubrication to reduce plunger-barrel friction, leading to potential issues like oil droplet release and drug aggregation. This study explored an alternative approach combining two-photon polymerization, laser machining, and microinjection molding to manufacture micro-dimpled structures for low friction. Plastic microdimples with high area density and low aspect ratio significantly reduced the coefficient of friction against rubber, while the dimple profile proved crucial in facilitating replication and demolding. The results of this study provide valuable insights into reducing friction between rubber and plastic, particularly in applications like syringes.

High-resolution low-cost LCD 3D printing for microfluidics and organ-on-a-chip devices.

The fabrication of microfluidic devices has progressed from cleanroom manufacturing to replica molding in polymers, and more recently to direct manufacturing by subtractive (e.g., laser machining) and additive (e.g., 3D printing) techniques, notably digital light processing (DLP) photopolymerization. However, many methods require technical expertise and DLP 3D printers remain expensive at a cost ∼15-30 K USD with ∼8 M pixels that are 25-40 μm in size. Here, we introduce (i) the use of low-cost (∼150-600 USD) liquid crystal display (LCD) photopolymerization 3D printing with ∼8-58 M pixels that are 18-35 μm in size for direct microfluidic device fabrication, and (ii) a poly(ethylene glycol) diacrylate-based ink developed for LCD 3D printing (PLInk). We optimized PLInk for high resolution, fast 3D printing and biocompatibility while considering the illumination inhomogeneity and low power density of LCD 3D printers. We made lateral features as small as 75 μm, 22 μm-thick embedded membranes, and circular channels with a 110 μm radius. We 3D printed microfluidic devices previously manufactured by other methods, including an embedded 3D micromixer, a membrane microvalve, and an autonomous capillaric circuit (CC) deployed for interferon-γ detection with excellent performance (limit of detection: 12 pg mL-1, CV: 6.8%). We made PLInk-based organ-on-a-chip devices in 384-well plate format and produced 3420 individual devices within an 8 h print run. We used the devices to co-culture two spheroids separated by a vascular barrier over 5 days and observed endothelial sprouting, cellular reorganization, and migration. LCD 3D printing together with tailored inks pave the way for democratizing access to high-resolution manufacturing of ready-to-use microfluidic and organ-on-a-chip devices by anyone, anywhere.

Review of molecular dynamics simulations in laser-based micro/nano-fabrication.

Laser technology is integral to the advancement of micro/nano-fabrication. While laser machining offers numerous advantages over alternative micro/nano-fabrication techniques, several challenges and bottlenecks continue to impede its large-scale industrial implementation. In response to these constraints, the molecular dynamics (MD) method has emerged as a formidable tool for optimizing the process parameters of laser micro/nano-fabrication and investigating alternative laser-based micro/nano-fabrication techniques. In this review, the application of MD in laser-based micro/nano-fabrication is comprehensively examined, including numerical simulations of short-pulse, long-pulse, continued laser and hybrid laser machining. The corresponding MD simulation schemes for lasers with different pulse widths are outlined. The mechanisms of laser-material interactions across diverse processing scenarios and the complete process of laser-based micro/nano-fabrication are also elucidated. Furthermore, the prevailing challenges in this domain and potential solutions are discussed, with future research directions being charted based on current knowledge and technological advancements.

Developments, challenges and future trends in advanced sustainable machining technologies for preparing array micro-holes.

The use of array micro-holes is becoming increasingly prevalent across a range of industries, including the aerospace, automotive, electronics, medical and chemical industries. The utilization of advanced sustainable machining technologies offers distinctive advantages and is pivotal for the sustainable manufacture of array micro-holes. This paper examines the sustainable machining techniques commonly employed in the production of array micro-holes, including electrical discharge machining, laser machining, electrochemical machining and composite machining technologies. The paper begins with an elaboration of the processing principles and characteristics of multiple non-traditional machining techniques. The performance indicators of the most commonly used processing technologies in industrial production are summarized from seven perspectives. Six significant avenues for the advancement of sustainable manufacturing technology for array micro-holes have been identified and categorized. This article provides a summary and evaluation of the previous relevant literature, with the aim of offering guidance for the development of array micro-hole processing technologies.

Energy consumption monitoring in DED-LB for enhancing the process sustainability

Energy efficiency is a highly relevant aspect in modern manufacturing processes, not only for economic reasons, but also because of the environmental impact it generates. With the aim of contributing to a more efficient and environmentally friendly manufacturing process, this research analyses the energy consumption of the Laser Directed Energy Deposition (DED-LB).First, the energy efficiency of the laser generator is characterized. In a second step, the deposition process is evaluated, which enables to categorize the process according to the amount of energy required per gram of material deposited, and the mass-deposition efficiency. For this purpose, a 3-level design of experiment (DOE) is performed in order to study the effect of the laser power, mass rate, and machine feed rate on the process efficiency. Besides, a metallographic study is also performed to ensure the metallurgical quality. Energy and material saving of 35% are obtained without influencing the clad quality.

Millisecond fibre laser drilling of alumina-alumina CMC

Alumina-Alumina (OX-Ox)CMCs are a technical ceramic composed of alumina fibres in an alumina matrix, with a primary usage case in the aerospace industry. Ox-Ox CMCs offer the traditional benefits of high toughness and bending strength, along with resistance to oxidation and corrosion associated with monolithic alumina, coupled with low brittleness and crack arresting behaviour of fibre in matrix composites. Whilst these properties are highly desirable, CMCs present significant difficulties for conventional mechanical machining, with laser machining offering potential solutions providing the impetus to the work presented in this paper. This work presents a parametric study of the effects of frequency and pulse energy for 10mm deep laser percussion drilled holes and a response surface study for these two variables, using an industrially representative 20kW peak power laser. Results show that for an 800µm diameter hole, a taper angle of <1⁰ and average recast layer thickness of <40µm are achievable, while the response surface study highlights the importance of considering input variables as a complex system, particularly for recast layer thickness.