Showing papers on "Machining published in 2016"

Wire + Arc Additive Manufacturing

Abstract: Depositing large components (>10 kg) in titanium, aluminium, steel and other metals is possible using Wire + Arc Additive Manufacturing. This technology adopts arc welding tools and wire as feedstock for additive manufacturing purposes. High deposition rates, low material and equipment costs, and good structural integrity make Wire+Arc Additive Manufacturing a suitable candidate for replacing the current method of manufacturing from solid billets or large forgings, especially with regards to low and medium complexity parts. A variety of components have been successfully manufactured with this process, including Ti–6Al–4V spars and landing gear assemblies, aluminium wing ribs, steel wind tunnel models and cones. Strategies on how to manage residual stress, improve mechanical properties and eliminate defects such as porosity are suggested. Finally, the benefits of non-destructive testing, online monitoring and in situ machining are discussed.

State-of-the-art in surface integrity in machining of nickel-based super alloys

Abstract: Nickel-based super alloys are gaining more significance, now-a-days, with extensive applications in aerospace, marine, nuclear reactor and chemical industries. Several characteristics including superior mechanical and chemical properties at elevated temperature, high toughness and ductility, high melting point, excellent resistance to corrosion, thermal shocks, thermal fatigue and erosion are primarily responsible for wide domain of application. Nevertheless, machined surface integrity of nickel-based super alloys is a critical aspect which influences functional performance including fatigue life of the component. This review paper presents state-of-the-art on various surface integrity characteristics during machining of nickel-based super alloys. Influence of various cutting parameters, cutting environment, coating, wear and edge geometry of cutting tools on different features of surface integrity has been critically explained. These characteristics encompass surface roughness, defects (surface cavities, metal debris, plucking, smeared material, redeposited material, cracked carbide particles, feed marks, grooves and laps), metallurgical aspects in the form of surface and sub-surface microstructure phase transformation, dynamic recrystallisation and grain refinement and mechanical characteristics such as work hardening and residual stress. Microstructural modification of deformed layer, profile of residual stresses and their influence on fatigue durability have been given significant emphasis. Future research endeavour might focus on development of new grades, advanced processing techniques of the same to ensure their superior stability of microstructure and thermo-mechanical properties along with advanced manufacturing processes like additive manufacturing to achieve highest level of fatigue durability of safety critical components while maintaining acceptable surface integrity and productivity.

Advanced Machining Processes of Metallic Materials: Theory, Modelling, and Applications

Abstract: This book updates our knowledge on the metal cutting processes in relation to theory and industrial practice. In particular, many topics reflect recent developments, e.g. modern tool materials, computational machining, computer simulation of various process phenomena, chip control, monitoring of the cutting state, progressive and hybrid machining operations, and generation and modelling of surface integrity. This book addresses the present state and future development of machining technologies. It provides a comprehensive description of metal cutting theory, experimental and modelling techniques along with basic machining processes and their effective use in a wide range of manufacturing applications.The topics covered include fundamental physical phenomena and methods for their evaluation, available technology of machining processes for specific classes of materials and surface integrity. The book also provides strategies for optimalization techniques and assessment of machinability. Moreover, it describes topics not currently covered in other sources, such as high performance and multitasking (complete) machining with a high potential for increasing productivity, and virtual and e-machining. The research covered here has contributed to a more generalized vision of machining technology, including not only traditional manufacturing tasks but also new potential (emerging) applications such as micro- and nanotechnology; many practical examples of modern machining technology; applicable for various technical, engineering and scientific levels; and collects together 20 years of research in the field and related technical information.

Fabrication and Machining of Metal Matrix Composites: A Review

Abstract: 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 ra...

Metal additive-manufacturing process and residual stress modeling

Abstract: Additive manufacturing (AM), widely known as 3D printing, is a direct digital manufacturing process, where a component can be produced layer by layer from 3D digital data with no or minimal use of machining, molding, or casting. AM has developed rapidly in the last 10 years and has demonstrated significant potential in cost reduction of performance-critical components. This can be realized through improved design freedom, reduced material waste, and reduced post processing steps. Modeling AM processes not only provides important insight in competing physical phenomena that lead to final material properties and product quality but also provides the means to exploit the design space towards functional products and materials. The length- and timescales required to model AM processes and to predict the final workpiece characteristics are very challenging. Models must span length scales resolving powder particle diameters, the build chamber dimensions, and several hundreds or thousands of meters of heat source trajectories. Depending on the scan speed, the heat source interaction time with feedstock can be as short as a few microseconds, whereas the build time can span several hours or days depending on the size of the workpiece and the AM process used. Models also have to deal with multiple physical aspects such as heat transfer and phase changes as well as the evolution of the material properties and residual stresses throughout the build time. The modeling task is therefore a multi-scale, multi-physics endeavor calling for a complex interaction of multiple algorithms. This paper discusses models required to span the scope of AM processes with a particular focus towards predicting as-built material characteristics and residual stresses of the final build. Verification and validation examples are presented, the over-spanning goal is to provide an overview of currently available modeling tools and how they can contribute to maturing additive manufacturing.

Machining of aluminum alloys: a review

Abstract: The use of aluminum alloys in manufacturing industry has increased significantly in recent years. This is because primarily to their ability to combine lightness and strength in a single material. Concomitant to this growth, the machining of aluminum alloys has enormously increased in volumetric proportions—so that the chip volume represents up to 80 % of the original volume of the machined material in certain segments of the industry, like aerospace. In this context, knowledge of the characteristics of machinability of aluminum alloys is essential to provide industry and researchers with information that allows them to make the right decisions when they come to machining this fantastic material. The purpose of this review is to compile relevant information about the characteristics of machinability of aluminum alloys into a single document.

Towards an automated robotic arc-welding-based additive manufacturing system from CAD to finished part

Abstract: Arc welding has been widely explored for additive manufacturing of large metal components over the last three decades due to its lower capital cost, an unlimited build envelope, and higher deposition rates. Although significant improvements have been made, an arc welding process has yet to be incorporated in a commercially available additive manufacturing system. The next step in exploiting "true" arc-welding-based additive manufacturing is to develop the automation software required to produce CAD-to-part capability. This study focuses on developing a fully automated system using robotic gas metal arc welding to additively manufacture metal components. The system contains several modules, including bead modelling, slicing, deposition path planning, weld setting, and post-process machining. Among these modules, bead modelling provides the essential database for process control, and an innovative path planning strategy fulfils the requirements of the automated system. A user friendly interface has been developed for non-experts to operate the developed system. Finally, a thin-walled aluminium structure has been fabricated automatically using only a CAD model as the informational input to the system. This exercise demonstrates that the developed system is a significant contribution towards the ultimate goal of producing a practical and highly automated arc-welding-based additive manufacturing system for industrial application. An automated arc-welding-based additive manufacturing system was reported.Integrated additive and subtractive manufacturing methodology was developed.Deposition paths and welding parameters were automatically generated.User interface using only CAD models as inputs was developed.The proposed automated system was verified experimentally.

Finishing of Fused Deposition Modeling parts by CNC machining

Abstract: Fused Deposition Modeling is a filament extrusion-base Additive Manufacturing process that integrates Computer Aided Design system, material science, Computer Numerical Control and the extrusion process to fabricate physical parts without geometrical limitations. Notwithstanding the wide industrial diffusion, one of the most limiting aspects of this technology is the obtainable surface roughness. This limitation implies that secondary finishing operations are necessary in order to comply with the design requirements. Several efforts have been done in this field but a lack exists about Computer Numerical Control machining: the Fused Deposition Modeling mesostructure and the anisotropic surface morphology, which strongly depends upon the deposition angle, make very difficult the determination of the cutting process parameters. The aim of this work is to develop a methodology able to unlock the possibility to finish Fused Deposition Modeling parts by Computer Numerical Control machining. A variable cutting depth has been considered to avoid inner defects arising and to eliminate initial surface morphology. An experimental campaign allowed to determine how cutting depth should be set as a function of deposition angle. A particular virtual model offset permitted to generate in Computer Aided Manufacturing the machine code. A case study characterized by functional surfaces confirmed the applicability of the method to complex geometry: a great reduction of average roughness and a reliable uniformity of finished surfaces have been obtained. A methodology to improve Fused Deposition Modeling roughness has been developed.The finishing has been performed by Computer Numerical Control machining.A variable cutting depth as a function of the deposition angle has been determined.The surface inside a Pelton bucket has been successfully finished.

Machining Parameters Optimization of Titanium Alloy using Response Surface Methodology and Particle Swarm Optimization under Minimum-Quantity Lubrication Environment

Abstract: The present paper depicts an application of response surface methodology (RSM) and particle swarm optimization (PSO) technique for optimizing the machining factors in turning of titanium (Grade-II) alloy using cubic boron nitride insert tool under minimum quantity lubricant (MQL) environment. The three machining factors, i.e., cutting speed (Vc), feed rate (f) and side cutting edge angle (approach angle π), are designed as three factors by using RSM design, which is withal subject to several constraints including tangential force (Fc), tool wear (VBmax), surface roughness (Ra) and tool-chip contact length (L). The multiple regression technique was used to establish the interaction between input parameters and given responses. Moreover, the results have been presented and optimized process parameters are acquired through multi-response optimization via desirability function as well as the PSO technique. The lower values of Vc (200 m/min), f (0.10 mm/rev) and higher values of ϕ (90°) are the optimum machini...

Effect of micro-textured tools on machining of Ti–6Al–4V alloy: An experimental and numerical approach

Abstract: In this work, an attempt is made to reduce the detrimental effects that occurred during machining of Ti–6Al–4V by employing surface textures on the rake faces of the cutting tools. Numerical simulation of machining of Ti–6Al–4V alloy with surface textured tools was employed, taking the work piece as elasto-plastic material and the tool as rigid body. Deform 3D software with updated Lagrangian formulation was used for numerical simulation of machining process. Coupled thermo-mechanical analysis was carried out using Johnson-cook material model to predict the temperature distribution, machining forces, tool wear and chip morphology during machining. Turning experiments on Ti–6Al–4V alloy were carried out using surface textured tungsten carbide tools with micro-scaled grooves in preferred orientation such as, parallel, perpendicular and cross pattern to that of chip flow. A mixture of molybdenum disulfide with SAE 40 oil (80:20) was used as semi-solid lubricant during machining process. Temperature distribution at tool–chip interface was measured using an infrared thermal imager camera. Feed, thrust and cutting forces were measured by a three component-dynamometer. Tool wear and chip morphology were captured and analyzed using optical microscopic images. Experimental results such as cutting temperature, machining forces and chip morphology were used for validating numerical simulation results. Cutting tools with surface textures produced in a direction perpendicular to that of chip flow exhibit a larger reduction in cutting force, temperature generation and reduced tool wear.

Influence of B4C particle reinforcement on mechanical and machining properties of Al6061/B4C composites

Abstract: This study investigates the mechanical and machinability properties of the aluminum 6061 reinforced with boron carbide (B4C). Four aluminum 6061 composite specimens reinforced with 5 wt%, 10 wt%, 15 wt%, and 20 wt% B4C were fabricated using a powder metallurgy and hot-extrusion method. The composite samples were investigated to elucidate the influence of different weight fractions of B4C reinforcement content on the hardness, fracture toughness, tensile strength, transverse rupture strength (TRS) and milling properties of the resulting composites. The milling tests were performed based on the Taguchi mixed-orthogonal-array for experiments, L16 (44 × 21), to determine the effect of B4C content on surface quality and energy consumption for different cutting parameters under dry- and compressed-air cooling and using an uncoated carbide insert. The results reveal that the B4C particles are uniformly distributed in the matrix and that the fracture toughness decreases and the hardness increases as the weight fraction of the reinforcement increases. The highest tensile and transverse rupture strength are for Al6061/5 wt% B4C and Al6061 reinforced with 10 wt% B4C composite material has the best fracture toughness from among the specimens measured. At higher milling speed and lower cutting feed and under dry machining conditions, an excellent surface quality is obtained after milling all composites materials and the surface finish improves with increasing B4C content in the matrix. The power consumption and surface roughness increases when cooling with compressed air.

Developments in electrochemical discharge machining: A review on electrochemical discharge machining, process variants and their hybrid methods

Abstract: Electrochemical discharge machining (ECDM) is a hybrid non-conventional machining process, used to machine electrically conductive and non-conductive materials. It is a preferred process to fabricate micro scale features like micro holes, micro channels, microgrooves and 3-dimensional intricate shapes on variety of materials. In order to improve the efficacy of ECDM process, certain technical augmentations are provided with basic configuration of ECDM. These augmentations result in developments of ECDM process variants. Further, research community has developed ECDM based triplex hybrid methods for further process enrichment. This review article presents a comprehensive review of these recent developments in ECDM process, its variants and their triplex hybrid methods. The future research possibilities are identified and presented as research potentials.

Rotary Ultrasonic Machining: A Review

Abstract: Rotary ultrasonic machining (RUM) is a mechanical type of nontraditional hybrid machining process that has been utilized potentially to machine a wide range of latest and difficult-to-machine materials, including ductile, hard and brittle, ceramics, composites, etc. In RUM, the basic material removal phenomenon of ultrasonic machining (USM) and conventional diamond grinding amalgamates together and results in higher material removal rate (MRR), improved hole accuracy with superior surface finish. In the current article, several investigations carried out in the domain of RUM for enormous materials have been critically reviewed and reported. It also highlights several experimental and theoretical ensues of RUM to improve the process outcomes and it is reported that process performance can be substantially improved by making the right selection of machine, diamond tooling, material and operating parameters. In recent years, various investigators have explored umpteen ways to enhance the RUM process performa...

Cutting forces in micro-end-milling processes

Abstract: Micro-end-milling is capable of machining complex structures in a wider variety of materials at the micro- and meso-scales as compared to other micro machining processes. However, the exact prediction of cutting forces in micro-end-milling is still not fully developed. In order to predict the general three-dimensional cutting force components, the related cutting edge radius size-effect, tool run-out, tool deflection and the exact trochoidal trajectory of tool flute are considered and presented in the proposed analytical prediction model. The proposed cutting force model also includes an algorithm for the calculation of the variable entry and exit angles caused by tool run-out and tool deflection. In the cutting force prediction model, the actual instantaneous uncut chip thickness is evaluated by considering the theoretical instantaneous uncut chip thickness, the minimum uncut chip thickness and a certain critical chip thickness value governed by three types of material removal mechanisms, in the elastic and the elastic–plastic deformation region and the complete chip formation region, respectively. To verify the model, the parameters of tool run-out and tool deflection were obtained from experimental measurements. The proposed cutting force model is validated through micro slot end milling tests with a two-flute carbide micro-end-mill on Al6061 workpieces. The experimental results agree with simulation results very well. The proposed theoretical model offers a basis for real-time machining process monitoring as well as cutting parameters optimization.