A review on conventional and nonconventional machining of SiC particle-reinforced aluminium matrix composites

Among the various types of metal matrix composites, SiC particle-reinforced aluminum matrix composites (SiC_p/Al) are finding increasing applications in many industrial fields such as aerospace, automotive, and electronics. However, SiC_p/Al composites are considered as difficult-to-cut materials due to the hard ceramic reinforcement, which causes severe machinability degradation by increasing cutting tool wear, cutting force, etc. To improve the machinability of SiC_p/Al composites, many techniques including conventional and nonconventional machining processes have been employed. The purpose of this study is to evaluate the machining performance of SiC p/Al composites using conventional machining, i.e., turning, milling, drilling, and grinding, and using nonconventional machining, namely electrical discharge machining (EDM), powder mixed EDM, wire EDM, electrochemical machining, and newly developed high-efficiency machining technologies, e.g., blasting erosion arc machining. This research not only presents an overview of the machining aspects of SiC_p/Al composites using various processing technologies but also establishes optimization parameters as reference of industry applications.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00313-2     

Fabrication and Machining of Metal Matrix Composites: A Review

Intrinsically smart, metal matrix composites (MMCs) are lightweight and high-performance materials having ever expanding industrial applications. The structural and the functional properties of these materials can be altered as per the industrial demands. The process technologies indulged in fabrication and machining of these materials attract the researchers and industrial community. Hybrid electric discharge machining is a promising and the most reliable nonconventional machining process for MMCs. It exhibits higher competence for machining complex shapes with greater accuracy. This paper presents an up-to-date review of progress and benefits of different routes for fabrication and machining of composites. It reports certain practical analysis and research findings including various issues on fabrication and machining of MMCs. It is concluded that polycrystalline tools and diamond-coated tools are best suitable for various conventional machining operations. High speed, small depth of cut and low feed rate are a key to better finish. In addition, hybrid electrical discharge machining has proved to be an active research area in critical as well as nonconventional machining since last few years. This paper incorporates year-wise research work done in fabrication, conventional machining, nonconventional machining, and hybrid machining of MMCs. Conclusions and future scope are addressed in the last section of the paper.     

Comparative study of jetting machining technologies over laser machining technology for cutting composite materials

There has been a great interest for improving the machining of composite materials in the aerospace and other industries. This paper focuses on the comparative study of jetting techniques and laser machining technics. This paper concentrates on the machining of composite materials like epoxy pre-impregnated graphite woven fabric and fibre reinforced plastic materials that are used in aerospace industries. While considering machining these materials with the traditional machining there are many disadvantages projected. One of these advantages is that all the traditional machining processes involve the dissipation of heat into the workpiece. This serious shortcoming has been dealt by the jetting technologies, which, contrary to the traditional machining, operate under cold conditions. The two methods in the jetting technologies used for processing materials are water jet machining and abrasive water jet machining. The first of these, water jet machining, has been around for the past 20 years and has paved the way for abrasive water jet technology. Water jet machining and abrasive water jet machining have been used for processing composite materials because of the advantages offered by this technologies as compared to traditional techniques of processing. The high surface and structural integrity required of any technique used for processing composite materials has created an opportunity for abrasive water jet machining. Cutting of composites using laser is also an option, and experiments were also conducted to reveal the extent of using laser technique.     

An approach towards damage free machining of CFRP and GFRP composite material: a review

Over the last decade, the use of polymeric composite material has increased considerably, and as a result, machinability of such material has also increased. The main aim of this work is to emphasize on the conventional and unconventional machining of composite materials, more specifically on drilling of carbon fiber-reinforced polymer and glass fiber-reinforced polymer. Additional concentration on tool materials and geometry, roughness of drill surface, thrust force and delamination at entry and exit with influence of point angle of tool, variable feed rate, and variable spindle speed. Over the last few years, many studied on the effect of cutting parameters and tool geometry using conventional machining, the phenomena associated with unconventional machining of composite material requires some supplementary studies in order to make damage free machining of composite materials.     

Wire electrical discharge machining characteristics of AA6061/cenosphere as-cast aluminum matrix composites

Machining of metal matrix composites (MMCs) reinforced with low-density waste byproduct particulates using nonconventional processes is relatively new in the field of material science. However, more attention has been paid for investigations on nontraditional machining of such MMCs currently as the conventional machining may generate additional complexity. This study investigates the wire electro-discharge machining behavior of compo-casted cenosphere-reinforced AA6061 alloys. Cu₆₀Zn₄₀-coated copper wire was used as electrode material. The investigation demonstrates that melting and vaporization are the dominant machining mechanisms. The weight fraction of cenosphere was observed to be the most substantial process variables affecting the cutting rate, on-time, and the wire speed of tool were the next in the order of importance. The presence of nonconductive cenosphere particles along with thermal degradation of the aluminum matrix composites leads to degrading processed machined surface quality. The issues related to wire breakage and poor quality of the machined surface, surface finish, and dimensional accuracy are described in detail.     

Smart Textile-Integrated Microelectronic Systems for Wearable Applications

The programmable nature of smart textiles makes them an indispensable part of an emerging new technology field. Smart textile-integrated microelectronic systems (STIMES), which combine microelectronics and technology such as artificial intelligence and augmented or virtual reality, have been intensively explored. A vast range of research activities have been reported. Many promising applications in healthcare, the internet of things (IoT), smart city management, robotics, etc., have been demonstrated around the world. A timely overview and comprehensive review of progress of this field in the last five years are provided. Several main aspects are covered: functional materials, major fabrication processes of smart textile components, functional devices, system architectures and heterogeneous integration, wearable applications in human and nonhuman-related areas, and the safety and security of STIMES. The major types of textile-integrated nonconventional functional devices are discussed in detail: sensors, actuators, displays, antennas, energy harvesters and their hybrids, batteries and supercapacitors, circuit boards, and memory devices.     

Experimental Study of the Tool Wear During the Electrochemical Discharge Machining

Electrochemical discharge machining is a nonconventional machining method which can be used to machine nonconductive materials such as glass and ceramics. However, machining of the refractory materials such as ceramics requires high voltages to produce the required thermal energy. In this condition, the tool wear would be increased significantly. This paper reports the study of the wear of the different tool materials. The selected tool materials have different melting/boiling temperatures responding to the high voltages in different ways. The possibility of using different tool materials in high voltages along with estimation of tool surface temperature is discussed in this paper.     

Investigating the effect of machining processes on the mechanical behavior of composite plates with circular holes

The influence of the machining quality on the mechanical behavior of CFRP composites is yet not fully understood. There are only few works in the literature that have investigated the effect of the machining quality on CFRP. In fact, most of these works focus only on conventional machining such as axial or orbital drilling. The aim of this paper is to examine the influence of two machining processes namely conventional machining (CM) and abrasive water jet machining (AWJM) on the mechanical behavior of composite plates under cyclic loading. For this purpose, an experimental study using several composite plates drilled with a cutting tool and an abrasive water jet machining was carried out. In order to study the impact of the process of machining on the mechanical behavior, thermographic infrared testing and fatigue cyclic tests were performed to assess temperature evolutions, stiffness degradation, and the damage evolution in these plates. Fatigue testing results have shown that the damage accumulation in specimens drilled with CM process was higher than the AWJM specimens. Furthermore, the endurance limit for a composite plate drilled with CM was approximately 10% inferior compared to specimens drilled with AWJM. This difference can be related to the initial surface integrity after machining induced by the difference in the mechanism of material’s removal between the two processes used.     

Fabrication and machining of ceramic composites — A review on current scenario

Ceramic matrix composites (CMCs) are the best-suited material for various engineering application due to their superior properties. The different processing methods involved in the fabrication and machining of these CMCs are a center for attraction to researchers and industrial society. This review article primarily focuses on the development of different processing methods and machining methods for ceramic matrix composites since the last few years. Out of these fabrication methods, powder metallurgy emerged as a most promising and cost-effective technique. In addition, electric discharge machining (EDM) has proved to be time saving, cost effective, and capable of machining complex shapes in composites. At the end, challenges in the processing and machining of ceramic matrix composites have been identified from the literature, and further benefits of microwave sintering and electric discharge machining of materials have been addressed in the paper.     

Reverse engineering of machining operation planning

Computer-aided process planning (CAPP) is becoming increasingly crucial to today's computer-integrated manufacturing (CIM) and rapid production. To automate the process planning, feature-based operation planning systems have been suggested and studied extensively. In such a system, given a machining feature, the operator requires practical machining operation data for the feature. In this research, a system of reverse engineering is proposed to extract machining features and their associated machining operation data. Furthermore, a machining know-how database containing the extracted data is created for future operation planning. Since successful NC programs contain the machining know-how of skilled workers, the system is aimed at extracting the machining know-how data from the NC programs through reverse engineering. The extraction of the machining features and feature topologies has been addressed previously. The present paper deals with the extraction of machining operation data, including operation sequence, cutting conditions, machining type and cutting mode. A prototype of the system is developed and a machining know-how database is generated. The extraction of machining features and their associated machining operations has been verified through a variety of NC programs.     

Optimization of machining techniques — A retrospective and literature review

In this paper an attempt is made to review the literature on optimizing machining parameters in turning processes. Various conventional techniques employed for machining optimization include geometric programming, geometric plus linear programming, goal programming, sequential unconstrained minimization technique, dynamic programming etc. The latest techniques for optimization include fuzzy logic, scatter search technique, genetic algorithm, Taguchi technique and response surface methodology.     

A review of machining theory and tool wear with a view to developing micro and nano machining processes

This paper reviews the current state-of-the-art surrounding macro scale machining; it discusses how these factors will influence the future development of micro and nano scale machining. The paper begins by reviewing machining theory, and then discusses high speed machining, tool wear, tool coatings, micromachining, meso machine tool design and future applications and research directions. Tool wear is a factor that determines the economy of the machining process. Therefore, an extensive part of the paper is devoted to the development of materials used to coat tools; in turn, it is anticipated these coatings will used in future micro machining applications. Consideration is also given to machine structures that are required to use these cutting tools at speeds in excess of one million revolutions per minute. This review provides a timely explanation of the literature surrounding the factors required for successful micro and nano machining.     

Real-time control of ultrafast laser micromachining by laser-induced breakdown spectroscopy

Ultrafast laser micromachining provides many advantages for precision micromachining. One challenging problem, however, particularly for multilayer and heterogeneous materials, is how to prevent a given material from being ablated, as ultrafast laser micromachining is generally material insensitive. We present a real-time feedback control system for an ultrafast laser micromachining system based on laser-induced breakdown spectroscopy (LIBS). The characteristics of ultrafast LIBS are reviewed and discussed so as to demonstrate the feasibility of the technique. Comparison methods to identify the material emission patterns are developed, and several of the resulting algorithms were implemented into a real-time computer control system. LIBS-controlled micromachining is demonstrated for the fabrication of microheater structures on thermal sprayed materials. Compared with a strictly passive machining process without any such feedback control, the LIBS-based system provides several advantages including less damage to the substrate layer, reduced machining time, and more-uniform machining features.     

Real-time scheduling in manufacturing system with machining and assembly operations: a state of art

Manufacturing systems producing multiple products are common in many industries, where products are made from several parts and/or sub-assemblies that require machining operations in first stage and assembly operations at later stage. Several scheduling techniques are proposed in the literature for such manufacturing system to develop near optimal schedule. A disruption in the manufacturing necessitates adjusting previously planned schedule which is known as real-time scheduling. This paper presents a comparative evaluation of different scheduling methods proposed by different investigators for dealing such situations. The literature indicates that real-time scheduling of manufacturing system with machining and assembly operations is hardly attempted. The paper offers a framework for developing rescheduling methodologies for such manufacturing situations.     

Advanced ceramic tool materials for machining

Cutting tools made of advanced ceramics have the potential for high-speed finish machining as well as for high-removal-rate machining of difficult-to-machine materials. The raw materials used in these ceramics are abundant, inexpensive, and free from strategic materials. In spite of this, solid or monolithic ceramic tools are currently used only to a limited extent partly due to certain limitations of these materials and partly due to the inadequacy of the machine tools used. The advances in ceramic materials and processing technology, the need to use materials that are increasingly more difficult to machine, increasing competition, and the rapidly rising manufacturing costs, have opened new vistas for ceramics in machining applications. The development of ceramic tool materials can be broadly categorized into three types: monolithic forms, thin coatings, and whisker-reinforced composites. Such a classification provides a totally new perspective on ceramic tool materials and broadens their scope considerably, and is justified on the basis that it is the ceramic addition that makes the tool material more effective. A brief overview of these materials is presented in this paper.     

Controlling the material removal and roughness of Inconel 718 in laser machining

Nickel alloys including Inconel 718 are considered as challenging materials for machining. Laser beam machining could be a promising choice to deal with such materials for simple to complex machining features. The machining accuracy is mainly dependent on the rate of material removal per laser scan. Because of the involvement of many laser parameters and complexity of the machining mechanism it is not always simple to achieve machining with desired accuracy. Actual machining depth extremely varies from very low to aggressively high values with reference to the designed depth. Thus, a research is needed to be carried out to control the process parameters to get actual material removal rate (MRR_act) equals to the theoretical material removal rate (MRR_th) with minimum surface roughness (SR) of the machined surfaces. In this study, five important laser parameters have been used to investigate their effects on MRR and SR. Statistical analysis are performed to identify the significant parameters with their strength of effects. Mathematical models have been developed and validated to predict the machining responses. Optimal set of laser parameters have also been proposed and confirmed to achieve the actual MRR close to the designed MRR (MRR_% = 100.1%) with minimum surface roughness (R_a = 2.67 µm).     

Assessment of the effectiveness of a spindle power signal for tool condition monitoring in machining processes

Less expensive and ‘readily available’ process monitoring techniques are needed to be effective in industrial machining processes. Spindle motors on modern computer numerical control machine tools allow easy access to the monitoring of spindle power. Whilst a spindle power signal fulfils the requirements for simple process monitoring, such a signal can trigger ‘machine alarms’ when process malfunctions occur. Little analysis has been done to assess the sensitivity of a spindle power signal relative to interrupted/continuous cutting processes. This paper aims to assess the effectiveness of a spindle power signal for tool condition monitoring in three machining processes: milling, drilling and turning. Based on cutting force/torque, the cutting power was calculated and a comparison between the theoretical cutting power and the spindle power signal was performed. Tool condition monitoring using spindle power could be successful in continuous machining processes (turning and drilling), while for discontinuous machining operations (milling), the spindle power signal showed reduced sensitivity to detect small uneven events such as chipping of one tooth. The results were used to define the sensitivity limitations when using a spindle power signal for tool condition monitoring on different computer numerical control machining centres where continuous and discontinuous machining operations are performed.     

Micro-electro-discharge machining as microsensor fabrication technology

This paper presents the design and fabrication of three miniaturized mechanical sensors to demonstrate the three-dimensional machining capabilities of micro-electro-discharge machining (EDM). The first sensor is an inertial bi-axial inclination sensor. The displacement of an inertial mass is measured optically by means of a two-dimensional position sensitive device (PSD). The machining freedom of micro-EDM makes it possible to produce both sensor and housing in one monolithic structure. The second sensor is an inertial uni-axial inclination sensor, which demonstrates the compatibility of the micro-EDM technology with the conventional photolithographic micromachining technologies. The mechanical structure of the sensor is machined by micro-EDM and the capacitive sensing part is produced by lithography. The aim of the integration is to set up a hybrid technology, which inherits the benefits of both micro-EDM and photolithography. The third miniaturized sensor is a three-component force sensor. The mechanical structure of the force sensor converts forces into displacements, which are measured optically. The mechanical structure of the force sensor is produced by wire-EDM and micro-EDM.     

Development of an integrated model for process planning and parameter selection for machining processes

The concept of ‘do it right the first time’ in the machining industry not only expects the best quality products but also at the best possible cost. The cost of machining depends on intelligent process planning and selection of machining parameters such as speed, feed, and depth of cut. The problem of machining parameter selection has received great attention by researchers and many techniques have been developed. A review of these techniques reveals that the selection of the machine and cutting tool is done before the process of cutting parameter selection and process sequencing, and often the selection is based on experience. The current research is an attempt to develop an integrated model (ExIMPro: Expert system based Integrated model for Machining Processes) which finds the sequence of operations with set of machines, tools, and other process parameters to minimise the cost of machining for a cylindrical part. This system consists of existing expert system Machining Parameter SELection (MPSEL) for machine and tool selection and a Microsoft Excel® and Visual Basic® based parameter selection model. The present model focuses on turning and cylindrical grinding operations but other processes can be incorporated with little modification to the software.     

Extracting alternative machining features: An algorithmic approach

Automated recognition of features from CAD models has been attempted for a wide range of application domains. In this article we address the problem of representing and recognizing a complete class of features in alternative interpretation for a given design.We present a methodology for recognizing a class of machinable features and addressing the computational problems posed by the existence of feature-based alternatives. Our approach addresses a class of volumetric features that describe material removal volumes made by operations on three-axis vertical machining centers, including drilling, pocket-milling, slot-milling, face-milling, chamfering, filleting, and blended surfaces.This approach recognizes intersecting features and is complete over all features in our class; i.e., for any given part, the algorithm produces a set containing all features in our class that correspond to possible operations for machining that part. This property is of particular significance in applications where consideration of different manufacturing alternatives is crucial.This approach employs a class of machinable features expressible as MRSEVs (a STEP-based library of machining features). An example of this methodology has been implemented using the ACIS solid modeler and the National Institute's of Health C++ class library.