A review of modeling and simulation of laser beam machining

Laser beam machining (LBM) is a widely used thermal advance machining process capable of high accuracy machining of almost any material with complex geometries. CO₂ and Nd:YAG lasers are mostly used for industrial purposes. Drilling, cutting, grooving, turning and milling are the applications of LBM with different material removal mechanisms. Modeling and simulation of the LBM process is indispensable for optimization purposes. Modeling can be done by implementing analytical, numerical, experimental and artificial intelligence-based methods. This paper provides a review of the various methods used for modeling and simulation of the laser beam machining process as well as key researches done in this field so far.     

An investigation of laser-assisted machining of Al2O3 ceramics planing

Laser-assisted machining (LAM), an alternative method of fabricating difficult-to-machine materials, uses primarily laser power to heat the local area (without necessarily evaporating or melting any material) before the material is removed. It not only efficiently reduces the cutting force during the manufacturing process but also improves the machining characteristics and geography with regard to difficult-to-machine materials, especially structural ceramics.This study on the application of laser-assisted machining to Al₂O₃ ceramics examines the measurements of cutting force and workpiece surface temperature as well as surface integrity and tool wear. Specifically, it uses the lattice Boltzmann method (LBM) to calculate the temperature distribution inside the ceramic workpiece during the LAM process and ensure that the laser energy causes no subsurface damage. The experimental results reveal that the LAM process efficiently reduces the cutting force by 22% (feed force) and 20% (thrust force) and produces better workpiece surface quality than conventional planing.     

Picosecond laser machining of tungsten carbide

Hard materials such as tungsten carbide (WC) are extensively used in cutting tools in high-value manufacturing, and the machining of these materials with sufficient speed and quality is essential to exploit their full potential. Over the last two decades, short (nanosecond (ns)) and ultra-short (picosecond (ps); femtosecond (fs)) pulse laser machining has been evaluated by various researchers and proposed as an alternative to the current state-of-the-art machining techniques for advanced materials like WC, which include mechanical grinding and electrical discharge machining. However, most of the established/existing research on this topic is based on low power lasers, which may not be adopted in industrial production environments due to its low material removal rate. This paper presents the results of a fundamental study, on using a 300 W picosecond laser for the deep machining of tungsten carbide. The influence of various laser parameters on the geometric precision and quality (surface and sub-surface) of the ablated area was analysed, and the ablation mechanism is discussed in detail. Laser pulse frequency and scanning speed have minimal effect on ablation rate at high power levels. The surface roughness of the ablated area increases with the ablation depth. At optimal conditions, no significant thermal defects such as a recast layer, micro crack or heat affected zone were observed, even at a high average power of 300 W. The material removal rate (MRR) seems to be proportional to the average power of the laser, and a removal rate of around 45 mm³ per minute can be achieved at 300 W power level. Edge wall taper appears to be a significant issue that needs to be resolved to enable industrial exploitation of high power ultra-short pulse lasers.     

New Developments in Laser Sintering of Diamond Cutting Disks

The analysis of techniques and problems in the fabrication of cutting tools based on super hard composites results in a solution by the application of lasers. The results of systematic study of diamond composites sintering with laser radiation are discussed. A mathematical modeling of the heat transfer process at high speed laser beam scanning has resulted in connections between working conditions and irradiated material characteristics. Experimental results of the influence of the laser parameters on the diamonds strength, the reliability of their fixing and composite materials structure changes are demonstrated. The possibilities to use new bonding materials based both on iron or other metals to improve the workability of the cutting tools are discussed.     

Analysis and prediction of laser cutting parameters of fibre reinforced plastics (FRP) composite materials

A theoretical model is presented considering the spatial distribution of the laser beam, interaction time between the laser and the work material, absorption coefficient of the laser beam at the laser wavelength and the thermal properties of the material. It is assumed that the laser energy is absorbed through the entire thickness of the material. The developed model predicts the various parameters in laser cutting of composite materials such as kerf width at the entry and at the exit, material removal rate and energy transmitted through the cut kerf. The theoretical analysis also determines the position of the beam with respect to the cutting front. Experiments for different laser and material combinations to evaluate the effects of cutting parameters on the cut quality were carried out to compare with the predicted results. The results obtained show very good agreement.     

Kerf characteristics in abrasive waterjet cutting of ceramic materials

An abrasive water jet (AWJ) can provide a more effective means for precision cutting of ceramic materials as compared with conventional machining methods, but many aspects about this cutting technology are still under flux and development. In this study, experimental techniques based on statistical experimental design principles and theoretical investigations were conducted to study AWJ cutting of alumina-based ceramics. Semi-empirical cutting depth equations are determined for the prediction and optimization of the AWJ cutting performance. Topographical characteristics of uncut-through kerf and the effects of various parameters are discussed. In addition, visualization studies are conducted to develop further understanding of the macromechanics of the AWJ cutting process.     

An Experimental Investigation of Laser Cladding

Laser cladding uses a laser beam to fuse materials with enhanced metallurgical properties on a substrate. A thin layer of the substrate is molten achieving good metallurgical bonding with the added material. In this paper experimental data from an industrial application of laser cladding are presented and discussed. The material of the substrate was an aluminum alloy and the cladding material was copper based powder. Under constant laser power and beam diameter, experiments were performed using various powder feed rates, process speeds and gas supply. The dimensions of the clad as well as the alloying and dilution depth were measured. The experimental data were analyzed in order to obtain a working range for the process parameters.     

Examination of wire electrical discharge machining of Al2O3p/6061Al composites

Alumina particle reinforced 6061 aluminum matrix composites (Al₂O₃p/6061Al) have excellent physical and chemical properties than those of a traditional metal; however, their poor machinability lead to worse surface quality and serious cutting tool wear. In this study, wire electrical discharge machining (WEDM) is adopted in machining Al₂O₃p/6061Al composite. In the experiments, machining parameters of pulse-on time were changed to explore their effects on machining performance, including the cutting speed, the width of slit and surface roughness. Moreover, the wire electrode is easily broken during the machining Al₂O₃p/6061Al composite, so this work comprehensively investigates into the locations of the broken wire and the reason of wire breaking.The experimental results indicate that the cutting speed (material removal rate), the surface roughness and the width of the slit of cutting test material significantly depend on volume fraction of reinforcement (Al₂O₃ particles). Furthermore, bands on the machined surface for cutting 20 vol.% Al₂O₃p/6061Al composite are easily formed, basically due to some embedded reinforcing Al₂O₃ particles on the surface of 6061 aluminum matrix, interrupt the machining process. Test results reveal that in machining Al₂O₃p/6061Al composites a very low wire tension, a high flushing rate and a high wire speed are required to prevent wire breakage; an appropriate servo voltage, a short pulse-on time, and a short pulse-off time, which are normally associated with a high cutting speed, have little effect on the surface roughness.     

Direct laser assisted machining with a sapphire tool for bulk metallic glass

Bulk metallic glasses (BMGs) are amorphous metallic alloys with high strength and hardness. This paper discusses the machining process of Zr-BMG using a transparent sapphire tool with direct laser assistance. The laser beam passes through the tool and directly heats the workpiece material to improve its machinability. Micro textures were generated on the tool rake face to facilitate chip formation. Reduced cutting forces and improved surface finish were observed with direct laser assistance. The effects of machining speed and laser power on the material deformation mechanism were investigated. A finite element model was developed to investigate the cutting forces.     

Review on ultrasonic machining

Ultrasonic machining is of particular interest for the cutting of non-conductive, brittle workpiece materials such as engineering ceramics. Unlike other non-traditional processes such as laser beam, and electrical discharge machining, etc., ultrasonic machining does not thermally damage the workpiece or appear to introduce significant levels of residual stress, which is important for the survival of brittle materials in service. The fundamental principles of ultrasonic machining, the material removal mechanisms involved and the effect of operating parameters on material removal rate, tool wear rate and workpiece accuracy are reviewed, with particular emphasis on the machining of engineering ceramics. The problems of producing complex 3-D shapes in ceramics are outlined.     

Study on the relationship between laser processing sound and material removal characteristics

Laser processing is an important manufacturing technology in machining difficult-to-cut materials. It is known that a sound is generated when laser processing is carried out, the intensity of the sound changing according to the processing conditions. The purpose of this research is to clarify experimentally the relationship between the material removal characteristics and the pressure level of the processing sound when a low and a high frequency laser beam are applied to the processing of ceramic materials.     

Laser Processing of Multilayered Thermal Spray Coatings: Optimal Processing Parameters

Laser processing offers an innovative approach for the fabrication and transformation of a wide range of materials. As a rapid, non-contact, and precision material removal technology, lasers are natural tools to process thermal spray coatings. Recently, a thermoelectric generator (TEG) was fabricated using thermal spray and laser processing. The TEG device represents a multilayer, multimaterial functional thermal spray structure, with laser processing serving an essential role in its fabrication. Several unique challenges are presented when processing such multilayer coatings, and the focus of this work is on the selection of laser processing parameters for optimal feature quality and device performance. A parametric study is carried out using three short-pulse lasers, where laser power, repetition rate and processing speed are varied to determine the laser parameters that result in high-quality features. The resulting laser patterns are characterized using optical and scanning electron microscopy, energy-dispersive x-ray spectroscopy, and electrical isolation tests between patterned regions. The underlying laser interaction and material removal mechanisms that affect the feature quality are discussed. Feature quality was found to improve both by using a multiscanning approach and an optional assist gas of air or nitrogen. Electrically isolated regions were also patterned in a cylindrical test specimen.     

Pulsed Nd:YAG laser turning of micro-groove on aluminum oxide ceramic (Al2O3)

The present study investigates the relationship of processes parameters of pulsed Nd:YAG laser-turning operation for production of micro-groove on cylindrical workpiece of ceramic material. A microprocessor-based work holding device has been developed to provide the rotational motion of cylindrical work pieces for micro-turning operation. Laser turning of micro-grooves on ceramics is highly demanded in the present industry because of its wide and potential uses in various fields such as automobile, aerospace and bio-medical engineering applications, etc. Experiments have been conducted on laser micro-grooving of aluminum oxide (Al₂O₃). The central composite second-order rotatable design (CCD) had been utilized to plan the experiments and response surface methodology was employed for developing empirical models. Analysis on machining characteristics of pulsed Nd:YAG laser micro-grooving operation was made based on the developed models. In this study, lamp current, pulse frequency, pulse width, assist air pressure and cutting speed of work piece are considered as laser machining process parameters. The process performances such as upper deviation (Y_uw), lower deviation (Y_lw) and depth (Y_d) characteristics of laser-turned micro-grooves produced on cylindrical work piece made of Al₂O₃ were evaluated. Analysis of variance (ANOVA) test had also been carried out to check the adequacy of the developed regression empirical models. The observed optimal process parameter settings are lamp current of 22.517 A, pulse frequency of 1.477 kHz, pulse width of 2.394% of duty cycle, cutting speed of 10.4283 rpm and assist air pressure of 1.3 kgf/cm² for achieving minimum upper deviation, lower deviation and depth of laser-turned micro-grooves, and finally the results were experimentally verified. From the analysis, it was found that proper control of the process parameters lead to achieve minimum upper deviation, lower deviation and depth of laser-turned micro-grooves produced on cylindrical workpiece of Al₂O₃.     

激光切割机用横梁的无模铸造工艺优化设计研究

激光切割机作为现代机械加工中重要的特种加工设备,其Y轴横梁结构复杂,制造难度大。为避免横梁结构砂铸过程中出现气孔、缩松、浇不足等缺陷,设计了双侧底注式浇注系统。结果表明,采用无模铸造成形技术设计了铸造型芯,采用Procast软件仿真优化了浇冒口工艺,最终确定了激光切割机横梁的铸造工艺方案。     

基于需求分类遗传算法的Al/15% SiC_p复合材料电化学加工工艺参数的优化

电化学加工（ECM）是一种重要的非传统加工工艺,主要用于加工难加工材料和错综复杂的型材。作为一个复杂的过程,很难确定最优参数去改善切削性能。金属去除率和表面粗糙度是最重要的输出参数,决定切削性能。由于切削参数对金属去除率和表面粗糙度的影响不一致,从而没有简单的切削参数的最佳组合。用多元回归模型来表示输出与输入变量之间的关系,并用基于需求分类遗传算法（NSGA-II）的多目标优化方法来优化ECM过程,得到一个需求解集。     

Laser ablation of titanium alloy under a thin and flowing water layer

Underwater laser ablation has become an alternative machining process that is able to reduce the thermal damage in work materials caused by lasers. However, the disturbance of water to the laser beam is a crucial concern for the ablation performance in water and cut surface quality obtained. In this study, a new laser ablation technique has been proposed, in which a waterjet was applied to impinge the top workpiece surface in order to form a thin and flowing water layer. With the assist of such water layer during the laser ablation, the redeposition and heat-affected zone can be minimized. Titanium alloy (Ti–6Al–4V) selected as a work sample was grooved by using a nanosecond-pulse laser under different machining conditions. The cut geometry and heat-affected zone were observed and analyzed to justify the process performance. The metallurgical change and cracks that occurred on and underneath the groove surface were also investigated in this study. The experimental results revealed that a clean cut with less thermal damage can be obtained when the workpiece was ablated by a laser under the flowing water layer. In addition, a narrower and deeper groove can be fabricated when a higher waterjet flow rate was applied. The laser ablation under the flowing water layer developed in this study could be a potential method for machining titanium alloy or even other thermal-sensitive materials.     

硬脆材料皮秒激光微加工试验研究

硬脆材料微加工中常存在材料易崩裂、刀具磨损严重、加工效率低等不足,引入超短脉冲激光微加工技术,通过光-热-力效应引发材料去除,可有效克服上述加工难题。以羟基磷灰石生物陶瓷、氧化铝工程陶瓷、单晶硅三种典型硬脆材料为加工对象,探索基于皮秒激光的微加工工艺方法,尝试利用激光干切、液体辅助、化学辅助等不同手段,完成微槽、微孔等结构的高质量加工,并分析微加工表面特征形貌,评估工艺方法可行性。     

Investigation on disk and CO2 laser beam fusion cutting differences based on power balance equation

In this work the calculation of the process temperatures in fusion cutting was carried out based on the power balance approach. Cutting experiments with CO₂ and disk lasers were performed on 1, 5 and 8 mm thick cold work tool steel sheets. The experimental, numerical and analytical evaluation of the single terms of the power balance equation allowed the explanation of the observed cut quality differences between disk and CO₂ laser cuts. Lower process temperatures calculated by a power balance equation for disk laser cuts lead to the increase of viscosity of molten material. The subsequent increase in difficulty for ejection of the molten material from the cut kerf explains the worse cut quality if compared with CO₂ laser cuts. Experimental evidence and theoretical calculations showed that the additional physical mechanisms like plasma formation should be considered in the overall power balance under particular cutting conditions.     

陶瓷基复合材料加工技术及其表面亚表面损伤机制研究进展

综述了陶瓷基复合材料的传统机械加工、超声辅助加工、激光加工、多能场复合加工等加工方式的研究进展,并简述了几种加工方式的优缺点.对陶瓷基复合材料的表面及亚表面损伤机制进行了总结和分析,包括材料表面亚表面损伤形式、材料表面亚表面理论及模型研究.提出了传统的陶瓷基复合材料加工技术需要进一步优化刀具材料、开发新的刀具结构、优化工艺参数等,以减少加工缺陷.研究了复合加工中材料去除率最大条件下的损伤容限条件、材料加工后的性能保持性等,同时探究了高效高质量的多能场复合加工新方法及其应用理论,以及研究探索了在复杂载荷及动载荷(如动态切削力、高温切削及超声动态冲击载荷)耦合作用下陶瓷基复合材料的内在损伤机理及演化问题.     

Special features of laser processing of layered materials

This article deals with the problems concerning the quality of laser machining of workpieces of laminates of natural and artificial origin (mica, thermoplastics and thermosetting plastics, foil sheets, and composite materials). The basic disadvantages of the laser machining operations (contour cutting and drilling of holes) are the material’s delamination at the edges of the processed workpieces, its melting, and destruction. These disadvantages arise because the irradiation conditions and the machining modes are not optimal; the selected mechanism of the workpiece material’s damage in the applied technological patterns of operations is not suitable. Theoretical and experimental studies of the machining process of various laminates allowed us to formulate and realize high-quality machining principles. The modes and results of the precision machining of workpieces of mica, foiled fiberglass laminate, and hybrid composites are presented.