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Showing papers in "International Journal of Machine Tools & Manufacture in 2003"


Journal ArticleDOI
TL;DR: Electrical discharge machining (EDM) has been continuously evolving from a mere tool and die making process to a micro-scale application machining alternative attracting a significant amount of research interests as mentioned in this paper.
Abstract: Electrical discharge machining (EDM) is a well-established machining option for manufacturing geometrically complex or hard material parts that are extremely difficult-to-machine by conventional machining processes. The non-contact machining technique has been continuously evolving from a mere tool and die making process to a micro-scale application machining alternative attracting a significant amount of research interests. In recent years, EDM researchers have explored a number of ways to improve the sparking efficiency including some unique experimental concepts that depart from the EDM traditional sparking phenomenon. Despite a range of different approaches, this new research shares the same objectives of achieving more efficient metal removal coupled with a reduction in tool wear and improved surface quality. This paper reviews the research work carried out from the inception to the development of die-sinking EDM within the past decade. It reports on the EDM research relating to improving performance measures, optimising the process variables, monitoring and control the sparking process, simplifying the electrode design and manufacture. A range of EDM applications are highlighted together with the development of hybrid machining processes. The final part of the paper discusses these developments and outlines the trends for future EDM research.

1,421 citations


Journal ArticleDOI
TL;DR: In this article, the authors present the various methodologies and practices that are being employed for the prediction of surface roughness, including machining theory, experimental investigation, designed experiments and artificial intelligence (AI).
Abstract: The general manufacturing problem can be described as the achievement of a predefined product quality with given equipment, cost and time constraints. Unfortunately, for some quality characteristics of a product such as surface roughness it is hard to ensure that these requirements will be met. This paper aims at presenting the various methodologies and practices that are being employed for the prediction of surface roughness. The resulting benefits allow for the manufacturing process to become more productive and competitive and at the same time to reduce any re-processing of the machined workpiece so as to satisfy the technical specifications. Each approach with its advantages and disadvantages is outlined and the present and future trends are discussed. The approaches are classified into those based on machining theory, experimental investigation, designed experiments and artificial intelligence (AI).

903 citations


Journal ArticleDOI
TL;DR: In this article, a three-dimensional model based on finite element analysis is used to study the thermal history and thermomechanical process in the butt-welding of aluminum alloy 6061-T6.
Abstract: Friction stir welding (FSW) is a relatively new welding process that may have significant advantages compared to the fusion processes as follow: joining of conventionally non-fusion weldable alloys, reduced distortion and improved mechanical properties of weldable alloys joints due to the pure solid-state joining of metals. In this paper, a three-dimensional model based on finite element analysis is used to study the thermal history and thermomechanical process in the butt-welding of aluminum alloy 6061-T6. The model incorporates the mechanical reaction of the tool and thermomechanical process of the welded material. The heat source incorporated in the model involves the friction between the material and the probe and the shoulder. In order to provide a quantitative framework for understanding the dynamics of the FSW thermomechanical process, the thermal history and the evolution of longitudinal, lateral, and through-thickness stress in the friction stirred weld are simulated numerically. The X-ray diffraction (XRD) technique is used to measure the residual stress of the welded plate, and the measured results are used to validate the efficiency of the proposed model. The relationship between the calculated residual stresses of the weld and the process parameters such as tool traverse speed is presented. It is anticipated that the model can be extended to optimize the FSW process in order to minimize the residual stress of the weld.

448 citations


Journal ArticleDOI
TL;DR: In the last two decades or so, spinning and flow forming have gradually matured as metal forming processes for the production of engineering components in small-to medium-batch quantities as discussed by the authors.
Abstract: In the last two decades or so, spinning and flow forming have gradually matured as metal forming processes for the production of engineering components in small to medium batch quantities. Combined spinning and flow forming techniques are being utilised increasingly due to the great flexibility provided for producing complicated parts nearer to net shape, enabling customers to optimise designs and reduce weight and cost, all of which are vital, especially in automotive industries. In this paper, process details of spinning and flow forming are introduced. The state of the art is described and developments in terms of research and industrial applications are reviewed. Also, the direction of research and development for future industrial applications are indicated.

407 citations


Journal ArticleDOI
TL;DR: In this paper, a three-dimensional heat transfer model for friction stir welding (FSW) is presented; a moving coordinate is introduced to reduce the difficulty of modeling the moving tool.
Abstract: A three-dimensional heat transfer model for friction stir welding (FSW) is presented in this paper; a moving coordinate is introduced to reduce the difficulty of modeling the moving tool. Heat input from the tool shoulder and the tool pin are considered in the model. The finite difference method was applied in solving the control equations. A non-uniform grid mesh is generated for the calculation. FSW experiments have been done to validate the calculated results. The calculated results are in good agreement with the experimental results. The calculation result also shows that preheat to the workpiece is beneficial to FSW.

395 citations


Journal ArticleDOI
TL;DR: In this paper, a closed-loop control system based on infrared image sensing is built for control of the heat input and size of the molten pool in the laser-based additive manufacturing (LBAM) process.
Abstract: Laser-Based Additive Manufacturing (LBAM) is a promising manufacturing technology that can be widely applied to part preparation, surface modification, and Solid Freeform Fabrication (SFF). A large number of parameters govern the LBAM process. These parameters are sensitive to the environmental variations, and they also influence each other. This paper introduces the research work in RCAM on improving the performance of the LBAM process. Metal powder delivery real-time sensing and control is studied to achieve a controllable powder delivery for fabrication of functionally graded material. A closed-loop control system based on infrared image sensing is built for control of the heat input and size of the molten pool in the LBAM process. The closed-loop control results show a great improvement in the geometrical accuracy of the built features. A three-dimensional finite element model is also established to explore the thermal behavior of the molten pool in the closed-loop controlled LBAM process.

315 citations


Journal ArticleDOI
TL;DR: In this article, the machinability of unidirectional carbon fiber reinforced by epoxy composites when subjected to orthogonal cutting was investigated. And the authors found that the subsurface damage and its mechanisms of a machined component are greatly influenced by fibre orientation.
Abstract: This paper aims to understand the machinability of epoxy composites reinforced by unidirectional carbon fibres when subjected to orthogonal cutting. It was found that the subsurface damage and its mechanisms of a machined component are greatly influenced by fibre orientation. The material’s bouncing back is a characteristic phenomenon associated with the cutting of a fibre-reinforced composite. Three distinct deformation zones appear, i.e., chipping, pressing and bouncing when the fibre orientation is

304 citations


Journal ArticleDOI
TL;DR: In this paper, the dynamic stability of the milling process is investigated through a single degree of freedom mechanical model and two alternative analytical methods are introduced, both based on finite dimensional discrete map representations of the governing time periodic delay differential equation.
Abstract: The dynamic stability of the milling process is investigated through a single degree of freedom mechanical model. Two alternative analytical methods are introduced, both based on finite dimensional discrete map representations of the governing time periodic delay-differential equation. Stability charts and chatter frequencies are determined for partial immersion up- and down-milling, and for full immersion milling operations. A special duality property of stability regions for up- and down-milling is shown and explained.

298 citations


Journal ArticleDOI
TL;DR: In this article, the milling process is modelled, based on dedicated experiments on both the material behaviour of the workpiece material and the machine dynamics, and a method for the prediction of the chatter boundaries is proposed and applied in order to predict the chatter boundary as a function of process parameters, such as spindle speed and depth-of-cut, for varying material and machine parameters.
Abstract: High-speed milling is widely used in the manufacturing industry. For the efficiency of the milling process, high demands on the material removal rate and the surface generation rate are posed. The process parameters, determining these two rates, are restricted by the occurrence of regenerative chatter. Chatter is an undesired instability phenomenon, which causes both a reduced product quality and rapid tool wear. In this paper, the milling process is modelled, based on dedicated experiments on both the material behaviour of the workpiece material and the machine dynamics. These experiments show that both the material properties and the machine dynamics are dependent on the spindle speed. Furthermore, a method for the prediction of the chatter boundaries is proposed and applied in order to predict the chatter boundaries as a function of process parameters, such as spindle speed and depth-of-cut, for spindle speed varying material and machine parameters. Finally, experiments are performed to estimate these chatter boundaries in practice. The modelled chatter boundaries are compared to the experimental results in order to validate the model and the stability analysis.

291 citations


Journal ArticleDOI
TL;DR: In this article, a new method of blending the copper powders contained resin with chromium powders to form tool electrodes was proposed, which facilitated the formation of a modified surface layer on the work piece after EDM, with remarkable corrosion resistant properties.
Abstract: Electrode materials for electrical discharge machining (EDM) are usually graphite, copper and copper alloys because these materials have high melting temperature, and excellent electrical and thermal conductivity. The electrodes made by using powder metallurgy technology from special powders have been used to modify EDM surfaces in recent years, to improve wear and corrosion resistance. However, electrodes are normally fabricated at high temperatures and pressures, such that fabrication is expensive. This paper proposes a new method of blending the copper powders contained resin with chromium powders to form tool electrodes. Such electrodes are made at low pressure (20 MPa) and temperature (200 °C) in a hot mounting machine. The results showed that using such electrodes facilitated the formation of a modified surface layer on the work piece after EDM, with remarkable corrosion resistant properties. The optimal mixing ratio, appropriate pressure, and proper machining parameters (such as polarity, peak current, and pulse duration) were used to investigate the effect of the material removal rate (MRR), electrode wear rate (EWR), surface roughness, and thickness of the recast layer on the usability of these electrodes. According to the experimental results, a mixing ratio of Cu–0wt%Cr and a sinter pressure of 20 MPa obtained an excellent MRR. Moreover, this work also reveals that the composite electrodes obtained a higher MRR than Cu metal electrodes; the recast layer was thinner and fewer cracks were present on the machined surface. Furthermore, the Cr elements in the composite electrode migrated to the work piece, resulting in good corrosion resistance of the machined surface after EDM.

252 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented an algorithm for identifying particular deviations such as angular deviations around linear axes relating to rotary axes in 5-axis machining centers, where three kinds of simultaneous three-axis control motions are designed for each rotary axis to identify the deviations.
Abstract: This paper presents an algorithm for identifying particular deviations such as angular deviations around linear axes relating to rotary axes in 5-axis machining centers. In this study, three kinds of simultaneous three-axis control motions are designed for each rotary axis to identify the deviations. In the measurement, two translational axes and one rotary axis are simultaneously controlled keeping the distance between a tool and a worktable constant. Telescoping ball bar is an effective instrument for measuring the relative displacement to the reference length in the work volume because its attitude is freely changed. In these three-axis control motions, the sensitive direction of the ball bar is kept constant. In order to determine the deviations, we derive eight equations from the relationship between the eccentricities obtained from the measured circular trajectories and the approximations derived from the mathematical model based on the simulation. In the simulation, a mathematical model considering the particular deviations is developed and then the characteristic diagrams are prepared for every deviation and every three-axis control motion. Based on the results, we propose a procedure for identifying the particular deviations in 5-axis machining centers and its procedure has been applied to identify the deviations actually. From both the simulation and the experiment, it has been confirmed that the proposed method gives precision results and is able to apply to the measurement of 5-axis machining center which is a tilting rotary table type.

Journal ArticleDOI
TL;DR: In this article, the number of contacting and cutting grains in a wheel was analyzed for both form and finish grinding and stock removal, and it was found that only a small fraction of the grains merely rubbed or plough into the work material and even a smaller fraction participated in actual cutting.
Abstract: Grinding of metals is a complex material removal operation involving cutting, ploughing, and rubbing depending on the extent of interaction between the abrasive grains and the workmaterial under the conditions of grinding. It is also a stochastic process in that a large number of abrasive grains of unknown geometry, whose geometry varies with time, participate in the process and remove material from the workpiece. Also, the number of grains passing through the grinding zone per unit time is extremely large. To address such a complex problem, it is necessary to analyze the mechanics of the grinding process using probability statistics, which is the subject of this investigation. Such an analysis is applicable to both form and finish grinding (FFG), such as surface grinding and stock removal grinding (SRG), such as cut-off operation. In this investigation, various parameters of the process including the number of abrasive grains in actual contact, the number of actual cutting grains per unit area for a given depth of wheel indentation, the minimum diameter of the contacting and cutting grains, and the volume of the chip removed per unit time were determined analytically and compared with the experimental results reported in the literature. Such an analysis enables the use of actual number of contacting and cutting grains in the grinding wheel for thermal and wheel wear analyses. It can also enable comparison of analytical work with the experimental results and contribute towards a better understanding of the grinding process. The analysis is applied to some typical cases of fine grinding and cut-off operations reported in the literature. It is found that out of a large number of grains on the surface of the wheel passing over the workpiece per second (~million or more per second), only a very small fraction of the grains merely rub or plough into the workmaterial (∼3.8% for FFG and ∼18% for SRG) and even a smaller fraction (∼0.14% for FFG and ∼1.8% for SRG) of that participate in actual cutting, thus validating Hahn’s rubbing grain hypothesis.

Journal ArticleDOI
TL;DR: In this article, a slicing procedure is proposed for Fused Deposition Modeling based on real-time edge profile of deposited layers, which is implemented and examples are included to explain the adaptive slicing method.
Abstract: Improvement of part surface quality and geometric accuracy in Rapid Prototyping has been a major concern. Reduction in build time and increase of part surface quality are two factors which contradict with each other as decreasing build time detracts part quality because of staircase effect. There has been a number of attempts to tackle this problem and adaptive slicing procedures are proposed. In these procedures the layer edge profiles are implicitly assumed as rectangular. But in real practice the edge profiles of a layer manufactured part are not rectangular and is found to be parabolic in case of Fused Deposition Modelling. A geometrical parameter known as cusp height is limited to a pre-specified value in existing adaptive slicing procedures, which is defined for rectangular edge profiles only. In this paper, a slicing procedure is proposed for Fused Deposition Modelling based on real time edge profile of deposited layers. The procedure is implemented and examples are included to explain the adaptive slicing method.

Journal ArticleDOI
TL;DR: In this paper, a probabilistic chip thickness model was proposed to predict the arithmetic mean surface roughness of ground surfaces using a geometrical analysis of the grooves left on the surface by ideal conic grains.
Abstract: The surface roughness is a variable often used to describe the quality of ground surfaces as well as to evaluate the competitiveness of the overall grinding system. This paper presents the prediction of the arithmetic mean surface roughness based on a probabilistic undeformed chip thickness model. The model expresses the ground finish as a function of the wheel microstructure, the process kinematic conditions, and the material properties. The analysis includes a geometrical analysis of the grooves left on the surface by ideal conic grains. The material properties and the wheel microstructure are considered in the surface roughness prediction through the chip thickness model. A simple expression that relates the surface roughness with the chip thickness was found, which was verified using experimental data from cylindrical grinding.

Journal ArticleDOI
TL;DR: In this paper, the performance improvement of conventional electrical discharge machining with a powder-mixed dielectric was evaluated through quality surface indicators and process time measurements, over a set of different processing areas.
Abstract: Electrical discharge machining (EDM) is a technological process with a large industrial implementation. Its use is particularly intense when very complex shapes on hard materials with a high geometrical and dimensional accuracy are required. However, the technological capability of the process has limited its application when the specification of the part surface quality imposes polished and mirror-like characteristics. The addition of powder particles in suspension in the dielectric modifies some process variables and creates the conditions to achieve a high surface quality in large areas. This paper presents a new research work aiming to study the performance improvement of conventional EDM when used with a powder-mixed dielectric. A silicon powder was used and the improvement is assessed through quality surface indicators and process time measurements, over a set of different processing areas. The results show the positive influence of the silicon powder in the reduction of the operating time, required to achieve a specific surface quality, and in the decrease of the surface roughness, allowing the generation of mirror-like surfaces.

Journal ArticleDOI
TL;DR: In this paper, an integrated model with experimental validation and sensitivity analysis for studying various thermo-mechanical-dynamic spindle behaviors at high speeds was presented, including bearing preload effects on bearing stiffness, and subsequently on overall spindle dynamics.
Abstract: High speed machining (HSM) is a promising technology for drastically increasing productivity and reducing production costs. Development of high-speed spindle technology is strategically critical to the implementation of HSM. Compared to conventional spindles, motorized spindles are equipped with built-in motors for better power transmission and balancing to achieve high-speed operation. However, the built-in motor introduces a great amount of heat into the spindle system as well as additional mass to the spindle shaft, thus complicating its thermo-mechanical-dynamic behaviors. This paper presents an integrated model with experimental validation and sensitivity analysis for studying various thermo-mechanical-dynamic spindle behaviors at high speeds. Specifically, the following effects are investigated: the bearing preload effects on bearing stiffness, and subsequently on overall spindle dynamics; high-speed rotational effects, including centrifugal forces and gyroscopic moments on the spindle shaft and, subsequently, on overall spindle dynamics; and the spindle dynamics on the cutting point receptance. The proposed integrated model is a useful tool for differentiating quantitatively different effects on the spindle behaviors. The results show that a motorized spindle softens at high speeds mainly due to the centrifugal effect on the spindle shaft.

Journal ArticleDOI
TL;DR: In this paper, the influence of feed rate, cutting speed, and tool wear on the effects induced by hard turning on case-hardened 27MnCr5 gear conebrakes and point out the technical limitations in mass production.
Abstract: Highly stressed steel components, e.g., gears and bearing parts, are appropriate applications for hard turning. Therefore, the process effects on significant engineering properties of work materials have to be carefully analyzed. Roughness, residual stresses, and white layers as parts of surface integrity, are functions of the machining parameters and of the cuttability of the cutting edge, i.e. of the tool wear. The aim of this work was to study the influence of feed rate, cutting speed, and tool wear on the effects induced by hard turning on case-hardened 27MnCr5 gear conebrakes and to point out the technical limitations in mass production.

Journal ArticleDOI
TL;DR: An extensive study of the wire lag phenomenon in wire-cut electrical discharge machining has been carried out and the trend of variation of the geometrical inaccuracy caused due to wire lag with various machine control parameters has been established in this paper.
Abstract: An extensive study of the wire lag phenomenon in Wire-cut Electrical Discharge Machining (WEDM) has been carried out and the trend of variation of the geometrical inaccuracy caused due to wire lag with various machine control parameters has been established in this paper. In an extremely complicated machining process like Wire-cut EDM, which is governed by as many as ten control factors, it is very difficult to select the best parametric combination for a particular situation arising out of customer requirements. In the present research study, all the machine control parameters are considered simultaneously for the machining operation which comprised a rough cut followed by a trim cut. The objective of the study has been to carry out an experimental investigation based on the Taguchi method involving thirteen control factors with three levels for an orthogonal array L27 (313). The main influencing factors are determined for given machining criteria, such as: average cutting speed, surface finish characteristic and geometrical inaccuracy caused due to wire lag. Also, the optimum parametric settings for different machining situations have been found out and reported in the paper.

Journal ArticleDOI
TL;DR: A comparison between several architectures of the multi-layer feed-forward neural network with a back propagation training algorithm for tool condition monitoring (TCM) of twist drill wear shows that the frequency domain features are more efficient in training the neural network than the time domain statistical moments.
Abstract: In automated flexible manufacturing systems the detection of tool wear during the cutting process is one of the most important considerations. This study presents a comparison between several architectures of the multi-layer feed-forward neural network with a back propagation training algorithm for tool condition monitoring (TCM) of twist drill wear. The algorithm utilizes vibration signature analysis as the main and only source of information from the machining process. The objective of the proposed study is to produce a TCM system that will lead to a more efficient and economical drilling tool usage. Five different drill wear conditions were artificially introduced to the neural network for prediction and classification. The experimental procedure for acquiring vibration data and extracting features in both the time and frequency domains to train and test the neural network models is detailed. It was found that the frequency domain features, such as the averaged harmonic wavelet coefficients and the maximum entropy spectrum peaks, are more efficient in training the neural network than the time domain statistical moments. The results demonstrate the effectiveness and robustness of using the vibration signals in a supervised neural network for drill wear detection and classification.

Journal ArticleDOI
TL;DR: In this paper, the surface integrity of advanced ceramics, including alumina, alumina-titania, and yttria partially stabilized tetragonal zirconia, were studied under high speed deep grinding conditions.
Abstract: Machining characteristics and surface integrity of advanced ceramics, including alumina, alumina-titania, and yttria partially stabilized tetragonal zirconia, were studied under high speed deep grinding conditions. Material removal mechanisms involved in the grinding processes were explored. The material removal in the grinding of alumina and alumina-titania was dominated by grain dislodgement or lateral cracking along grain boundaries. The removal for zirconia was via both local micro fracture and ductile cutting. It was found that under a feed rate of 500 mm/min and for all the wheel speeds used, an increase in the wheel depth of cut (DOC) from 0.1-2 mm slightly improved the ground surface finish, but greatly prolonged the wheel life. This increase did not deepen the subsurface damage layer for the alumina and alumina-titania, but resulted in a slightly deeper damage layer for the zirconia.

Journal ArticleDOI
J Simao1, H.G Lee1, David K. Aspinwall1, R.C. Dewes1, E.M Aspinwall1 
TL;DR: In this paper, experimental results are presented on the surface alloying of AISI H13 hot work tool steel during a die sink operation using partially sintered WC/Co electrodes operating in a hydrocarbon oil dielectric.
Abstract: Electrical discharge machining (EDM) is a widely used process in the mould / die and aerospace industries. Following a brief summary of the process, the paper reviews published work on the deliberate surface alloying of various workpiece materials using EDM. Details are given of operations involving powder metallurgy (PM) tool electrodes and the use of powders suspended in the dielectric fluid, typically aluminium, nickel, titanium, etc. Following this, experimental results are presented on the surface alloying of AISI H13 hot work tool steel during a die sink operation using partially sintered WC / Co electrodes operating in a hydrocarbon oil dielectric. An L8 fractional factorial Taguchi experiment was used to identify the effect of key operating factors on output measures (electrode wear, workpiece surface hardness, etc.). With respect to microhardness, the percentage contribution ratios (PCR) for peak current, electrode polarity and pulse on time were ~24, 20 and 19%, respectively. Typically, changes in surface metallurgy were measured up to a depth of ~30 μm (with a higher than normal voltage of ~270 V) and an increase in the surface hardness of the recast layer from ~620 HK 0.025 up to ~1350 HK 0.025 .

Journal ArticleDOI
TL;DR: In this article, the authors present a method of assembling known dynamics of the spindle-tool holder with an analytically modeled end mill using the receptance coupling technique, which includes both translational and rotational degrees of freedom.
Abstract: Identification of chatter free cutting conditions, the chatter stability lobes, requires a measurement of the frequency response function (FRF) of each tool mounted on the spindle. This paper presents a method of assembling known dynamics of the spindle–tool holder with an analytically modeled end mill using the receptance coupling technique. The classical receptance technique is enhanced by proposing a method of identifying the end mill–spindle/tool holder joint dynamics, which include both translational and rotational degrees of freedom. The method requires measurement of FRFs with impact tests applied on the spindle–tool holder assembly and blank calibration cylinders attached to the spindle. The spindle and tool holder characteristics are completely identified from the two experiments, and used for the mathematical prediction of FRF for end mills with arbitrary dimensions. The proposed method is experimentally proven and verified in cutting tests.

Journal ArticleDOI
TL;DR: In this article, the optimal range of chisel edge length with respect to drill diameter is derived for a pre-drilled pilot hole, which can reduce the delamination rate significantly.
Abstract: Drilling-induced delamination often occurs both at the entrance and the exit of the workpiece during drilling of composite material. Investigators have studied analytically and experimentally that delamination in drilling can be correlated to the thrust force of the drill. With a pre-drilled pilot hole, the delamination can be reduced significantly. Early reference reported models of drilling-induced delamination, however, the effect of chisel edge length and pilot hole diameter on delamination is rarely discussed. The optimal range of chisel edge length with respect to drill diameter is derived in this paper.

Journal ArticleDOI
TL;DR: In this paper, the stability of interrupted cutting in a single degree of freedom milling process was studied experimentally and an instrumented flexure was used to provide a flexible workpiece with a natural frequency comparable to the tooth pass frequency, mimicking high speed milling dynamics.
Abstract: The stability of interrupted cutting in a single degree of freedom milling process was studied experimentally. An instrumented flexure was used to provide a flexible workpiece with a natural frequency comparable to the tooth pass frequency, mimicking high speed milling dynamics. The displacement of the system was sampled continuously and periodically once per cutter revolution. These data samples were used to asses the stability of the system. Results confirm the theoretical predictions obtained in Part 1.

Journal ArticleDOI
TL;DR: In this paper, the development and application of a hybrid artificial neural network and genetic algorism methodology to modelling and optimisation of electro-discharge machining was discussed. And the hybridization approach is aimed not only at exploiting the strong capabilities of the two tools, but also at solving manufacturing problems that are not amenable for modelling using traditional methods.
Abstract: This paper discusses the development and application of a hybrid artificial neural network and genetic algorism methodology to modelling and optimisation of electro-discharge machining. The hybridisation approach is aimed not only at exploiting the strong capabilities of the two tools, but also at solving manufacturing problems that are not amenable for modelling using traditional methods. Based on an experimental data, the model was tested with satisfactory results. The developed methodology with the model is highly beneficial to manufacturing industries, such as aerospace, automobile and tool making industries.

Journal ArticleDOI
TL;DR: In this article, the combined effects of power and feed rate on kerf width, surface roughness, striation frequency and the size of heat affected zone (HAZ) have been studied.
Abstract: Samples of 4130 steel were cut on a CO2 laser cutting system and the combined effects of power and feed rate on kerf width, surface roughness, striation frequency and the size of heat affected zone (HAZ) have been studied. Regression analysis was used to develop models that describe the effect of the independent process parameters on laser cut quality. For the range of operation conditions tested, it was observed that power had a major effect on kerf width and size of HAZ, while feed rate affects were secondary. On the other hand, surface roughness and striation frequency were affected most by feed rate. At low power levels, the smallest kerf width and HAZ are obtained and the effect of feed rate is moderate. Low feed rates gave good surface roughness and low striation frequency. For optimum cut quality, kerf width, HAZ and surface roughness are kept at a minimum. However, operating conditions that satisfy these requirements while maintaining high productivity could not be identified.  2002 Elsevier Science Ltd. All rights reserved.

Journal ArticleDOI
TL;DR: In this article, a new approach for machining of Inconel 718 is presented, which combines traditional turning with cryogenically enhanced machining and plasma-enhanced machining.
Abstract: A new approach for machining of Inconel 718 is presented in this paper. It combines traditional turning with cryogenically enhanced machining and plasma enhanced machining. Cryogenically enhanced machining is used to reduce the temperatures in the cutting tool, and thus reduces temperature-dependent tool wear to prolong tool life, whereas plasma enhanced machining is used to increase the temperatures in the workpiece to soften it. By joining these two non-traditional techniques with opposite effects on the cutting tool and the workpiece, it has been found that the surface roughness was reduced by 250%; the cutting forces was decreased by approximately 30–50%; and the tool life was extended up to 170% over conventional machining.

Journal ArticleDOI
TL;DR: In this article, the development of mathematical models for the selection of process parameters and the prediction of bead geometry (bead width, bead height and penetration) in robotic GMA (Gas Metal Arc) welding is discussed.
Abstract: Generally, the quality of a weld joint is strongly influenced by process parameters during the welding process In order to achieve high quality welds, mathematical models that can predict the bead geometry and shape to accomplish the desired mechanical properties of the weldment should be developed This paper focuses on the development of mathematical models for the selection of process parameters and the prediction of bead geometry (bead width, bead height and penetration) in robotic GMA (Gas Metal Arc) welding Factorial design can be employed as a guide for optimization of process parameters Three factors were incorporated into the factorial model: arc current, welding voltage and welding speed A sensitivity analysis has been conducted and compared the relative impact of three process parameters on bead geometry in order to verify the measurement errors on the values of the uncertainty in estimated parameters The results obtained show that developed mathematical models can be applied to estimate the effectiveness of process parameters for a given bead geometry, and a change of process parameters affects the bead width and bead height more strongly than penetration relatively

Journal ArticleDOI
TL;DR: In this paper, a method for programming spindle speed variation for machine tool chatter suppression is presented, which is based on varying the spindles speed for minimum energy input by the cutting process.
Abstract: This paper presents a novel method for programming spindle speed variation for machine tool chatter suppression. This method is based on varying the spindle speed for minimum energy input by the cutting process. The work done by the cutting force during sinusoidal spindle speed variation S 3 V is solved numerically over a wide range of spindle speeds to study the effect of S 3 V on stable and unstable systems and to generate charts by which the optimum S 3 V amplitude ratio can be selected. For on-line application, a simple criterion for computing the optimal S 3 V amplitude ratio is presented. Also, a heuristic criterion for selecting the frequency of the forcing speed signal is developed so that the resulting signal ensures fast stabilization of the machining process. The proposed criteria are suitable for on-line chatter suppression, since they only require knowledge of the chatter frequency and spindle speed. The effectiveness of the developed S 3 V programming method is verified experimentally.

Journal ArticleDOI
TL;DR: In this article, the workpiece roughness in multiaxis finishing milling with ball end tools is predicted by means of the computer supported milling simulation algorithm "ballmill " by considering the individual movements of the cutting tool and the work piece due to the milling kinematics, the undeformed chip geometry, the cutting force components, the tool deflections and the final surface topomorphy expected.
Abstract: CAD/CAM systems offer various possibilities for finishing milling of parts such as dies and moulds, turbine blades and other high quality components, but most of them do not take into account the surface topomorphy expected, which is significantly affected, among others, by the milling kinematics and the contact conditions between the tool and the workpiece. In order to predict the workpiece roughness in multiaxis finishing milling with ball end tools, the computer supported milling simulation algorithm ‘ ballmill ’ was developed. By means of this algorithm, considering the individual movements of the cutting tool and of the workpiece due to the milling kinematics, the undeformed chip geometry, the cutting force components, the tool deflections and the final surface topomorphy expected are determined. Numerous investigations concerning the parameters mentioned above, with various workpiece materials have been carried out in order to determine the correlation of the experimental results with the corresponding calculated ones with the aid of the ballmill algorithm. Moreover the algorithm validity was extensively evaluated in milling of free form surfaces of large hydroturbine blades. The convergence between the experimental and the related calculated surface topomorphies by means of the ballmill computer program was found out to be satisfactory. Thus, the prediction of appropriate cutting conditions and milling kinematics to fulfill surface topomorphy requirements was enabled.