scispace - formally typeset
Search or ask a question

Showing papers in "International Journal of Machine Tools & Manufacture in 2005"


Journal ArticleDOI
TL;DR: In this article, the authors present an overview of major advances in machining techniques that have resulted to step increase in productivity, hence lower manufacturing cost, without adverse effect on the surface finish, surface integrity, circularity and hardness variation of the machined component.
Abstract: Significant advances have been made in understanding the behaviour of engineering materials when machining at higher cutting conditions from practical and theoretical standpoints. This approach has enabled the aerospace industry to cope with constant introduction of new materials that allow the engine temperature to increase at a rate of 10 °C per annum since the 1950s. Improvements achieved from research and development activities in this area have particularly enhanced the machining of difficult-to-cut nickel base and titanium alloys that have traditionally exhibited low machinability due to their peculiar characteristics such as poor thermal conductivity, high strength at elevated temperature, resistance to wear and chemical degradation, etc. A good understanding of the cutting tool materials, cutting conditions, processing time and functionality of the machined component will lead to efficient and economic machining of nickel and titanium base superalloys. This paper presents an overview of major advances in machining techniques that have resulted to step increase in productivity, hence lower manufacturing cost, without adverse effect on the surface finish, surface integrity, circularity and hardness variation of the machined component.

847 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used neural network models to predict surface roughness and tool flank wear over the machining time for variety of cutting conditions in finish hard turning of hardened AISI 52100 steel.
Abstract: In machining of parts, surface quality is one of the most specified customer requirements. Major indication of surface quality on machined parts is surface roughness. Finish hard turning using Cubic Boron Nitride (CBN) tools allows manufacturers to simplify their processes and still achieve the desired surface roughness. There are various machining parameters have an effect on the surface roughness, but those effects have not been adequately quantified. In order for manufacturers to maximize their gains from utilizing finish hard turning, accurate predictive models for surface roughness and tool wear must be constructed. This paper utilizes neural network modeling to predict surface roughness and tool flank wear over the machining time for variety of cutting conditions in finish hard turning. Regression models are also developed in order to capture process specific parameters. A set of sparse experimental data for finish turning of hardened AISI 52100 steel obtained from literature and the experimental data obtained from performed experiments in finish turning of hardened AISI H-13 steel have been utilized. The data sets from measured surface roughness and tool flank wear were employed to train the neural network models. Trained neural network models were used in predicting surface roughness and tool flank wear for other cutting conditions. A comparison of neural network models with regression models is also carried out. Predictive neural network models are found to be capable of better predictions for surface roughness and tool flank wear within the range that they had been trained. Predictive neural network modeling is also extended to predict tool wear and surface roughness patterns seen in finish hard turning processes. Decrease in the feed rate resulted in better surface roughness but slightly faster tool wear development, and increasing cutting speed resulted in significant increase in tool wear development but resulted in better surface roughness. Increase in the workpiece hardness resulted in better surface roughness but higher tool wear. Overall, CBN inserts with honed edge geometry performed better both in terms of surface roughness and tool wear development. q 2004 Elsevier Ltd. All rights reserved.

599 citations


Journal ArticleDOI
TL;DR: In this article, a second-order response model for the geometric error was developed and the utilization of the response surface model was evaluated with constraints of the surface roughness and the material removal rate.
Abstract: The geometric error in the surface grinding process is mainly affected by the thermal effect and the stiffness of the grinding system. For minimizing the geometric error, the selection of grinding parameters is very important. This paper presented an application of Taguchi and response surface methodologies for the geometric error. The effect of grinding parameters on the geometric error was evaluated and optimum grinding conditions for minimizing the geometric error were determined. A second-order response model for the geometric error was developed and the utilization of the response surface model was evaluated with constraints of the surface roughness and the material removal rate. Confirmation experiments were conducted at an optimal condition and selected two conditions for observing accuracy of the developed response surface model.

356 citations


Journal ArticleDOI
TL;DR: In this paper, the knowledge about machining of nonconducting materials using electrochemical discharge phenomenon is reviewed up to this date with some particular attention to the electrochemical point of view.
Abstract: Machining with electrochemical discharges is an unconventional technology able to machine several electrically non-conductive materials like glass or some ceramics. After almost 40 years of its first mention in literature, this technology remains an academic application and was never applied in industrial context. The knowledge about machining of non-conducting materials using electrochemical discharge phenomenon is reviewed up to this date with some particular attention to the electrochemical point of view. Some main limiting factors are highlighted and possible solutions are discussed.

294 citations


Journal ArticleDOI
Z. C. Li1, Yue Jiao1, Timothy W. Deines1, Zhijian Pei1, C. Treadwell 
TL;DR: In this article, rotary ultrasonic machining (RUM) is introduced into drilling holes on CMC panels for the first time, and the feasibility to machine CMC using RUM is investigated.
Abstract: Ceramic matrix composites (CMC) are enabling materials for a number of high-temperature and demanding applications in aerospace, power generation, ground transportation, nuclear, environmental, and chemical industries. Tremendous progress has been made in technology development, manufacturing, commercialization, and applications of CMC over the last few years. However, significant challenges (such as the lack of specifications, databases, and in-service repair methodology, and high machining cost) still remain for their widespread applications. In this paper, rotary ultrasonic machining (RUM) is introduced into drilling holes on CMC panels for the first time. The feasibility to machine CMC using RUM is investigated. Cutting forces and material removal rates (MRR) are compared for machining of CMC with and without ultrasonic vibration and for two types of CMC materials and one typical advanced ceramic material (alumina). Chippings at the hole exit are also observed under a microscope. Furthermore, the paper presents the results of a designed experimental investigation into RUM of CMC. A three-variable two-level full factorial design is employed to reveal main effects as well as interaction effects of three RUM process parameters (spindle speed, feedrate, and ultrasonic power). The process outputs studied include cutting force, MRR, and hole quality (in terms of chipping dimensions).

257 citations


Journal ArticleDOI
TL;DR: In this paper, the relationship between the friction of a tool-workpiece and the minimum cutting thickness in micro cutting was investigated and an ultra-precision cutting model was proposed in which the tool edge radius and the friction coefficient were the principal factors determining the minimum cut thickness with a continuous chip.
Abstract: In the ultra precision diamond cutting process, the rake angle of the tool is likely to become negative because the edge radius of tool is considerably large compared to the sub-micrometer depth of cut. The round edge of the tool might sometimes cause plowing results in a poor surface, or burnishing which results in a shiny surface depending on the depth of cut. This study deals with the relationship between the friction of a tool-workpiece and the minimum cutting thickness in micro cutting. Proposed is an ultra precision cutting model in which the tool edge radius and the friction coefficient are the principal factors determining the minimum cutting thickness with a continuous chip. According to the model, a smaller edge radius and a higher friction coefficient make the cutting depth thinner. The experimental results verify the proposed model and provide various supporting evidence.

240 citations


Journal ArticleDOI
TL;DR: In this paper, the performance of different CBN tool grades in finish turning Ti-6Al-4V (IMI 318) alloy at high cutting conditions, up to 250m/min−1, with various coolant supplies was evaluated.
Abstract: Cubic Nitride Boron (CBN) tools are generally used for machining harder alloys such as hardened high Cr steels, titanium and nickel alloys. The tools are expected to withstand the heat and pressure developed when machining at higher cutting conditions because of their high hardness and melting point. This paper evaluates the performance of different CBN tool grades in finish turning Ti–6Al–4V (IMI 318) alloy at high cutting conditions, up to 250 m min−1, with various coolant supplies. Tool wear, failure modes, cutting and feed forces and surface roughness of machined surfaces were monitored and used to access the performance of the cutting tools. Comparative trials were carried out with uncoated carbide tools when machining at a speed of 150 m min−1. Test results show that the performance of CBN tools, in terms of tool life, at the cutting conditions investigated is poor relative to uncoated carbide tools, as expected and often, reported due probably to rapid notching and excessive chipping of the cutting edge associated with a relatively high diffusion wear rate that tends to weaken the bond strength of the tool substrate. An increase in the CBN content of the cutting tool also led to a reduction in tool life when machining at the cutting conditions investigated.

236 citations


Journal ArticleDOI
TL;DR: In this article, a method for obtaining the instability or stability lobes, applicable when both the machine structure and the machined workpiece have similar dynamic behaviours, is presented. But this method is not suitable for the case of very thin walls with the possibility of lateral vibration of them in some cutting conditions.
Abstract: High speed machining of low rigidity structures is a widely used process in the aeronautical industry. Along the machining of this type of structures, the so-called monolithic components, large quantities of material are removed using high removal rate conditions, with the risk of the instability of the process. Very thin walls will also be milled, with the possibility of lateral vibration of them in some cutting conditions and at some stages of machining. Chatter is an undesirable phenomenon in all machining processes, causing a reduction in productivity, low quality of the finished workpieces, and a reduction of the machine-spindle's working life. In this study, a method for obtaining the instability or stability lobes, applicable when both the machine structure and the machined workpiece have similar dynamic behaviours, is presented. Thus, a 3-dimensional lobe diagram has been developed based on the relative movement of both systems, to cover all the intermediate stages of the machining of the walls. This diagram is different and more exact than the one that arises out of the mere superposition of the machine and the workpiece lobe diagrams. A previous step of rejecting resonance modes that are not involved in the milling at the bottom zones of the thin walls must be previously performed. Finally, the proposed method has been validated, by machining a series of thin walls, applying cutting conditions contrasted with the limits previously obtained in the three-dimensional lobe diagram.

235 citations


Journal ArticleDOI
TL;DR: In this article, the influence of the machining characteristics on pure titanium metals using an electrical discharge machining (EDM) with the addition of urea into distilled water was investigated.
Abstract: This study investigates the influence of the machining characteristics on pure titanium metals using an electrical discharge machining (EDM) with the addition of urea into distilled water. Additionally, the effects of urea addition on surface modification are also discussed. In the experiments, machining parameters such as the dielectric type, peak current and pulse duration were changed to explore their effects on machining performance, including the material removal rate, electrode wear rate and surface roughness. Moreover, the elemental distribution of nitrogen on the machined surface was qualitatively determined by EPMA to assess the effects on surface modification. Micro hardness and wear resistance tests were performed to evaluate the effects of the reinforced surface. Experimental results indicate that the nitrogen element decomposed from the dielectric that contained urea, migrated to the work piece, forming a TiN hard layer, resulting in good wear resistance of the machined surface after EDM.

227 citations


Journal ArticleDOI
TL;DR: In this article, a new model to understand the behavior of how materials are removed from workpiece in nano cutting is proposed, which postulates that the mechanism of nano-scale material removal is based on extrusion, which is different from the shearing mechanism in conventional cutting.
Abstract: A new model to understand the behaviour of how materials are removed from workpiece in nano cutting is proposed. This model postulates that the mechanism of nanometric scale material removal is based on extrusion, which is different from the shearing mechanism in conventional cutting. It also explains why brittle materials are removed in ductile mode. Analytical results from molecular dynamics and nano indentation show good agreement with the proposed modelling. Experiments are conducted to verify the new model for nanometric cutting of monocrystalline silicon. The theoretical modelling and experimental verification present a good understanding of nano-scale material removal and provide an approach to fundamentally control the machining performance.

216 citations


Journal ArticleDOI
TL;DR: In this paper, a comparative study of electro jet drilling with another non-traditional hole-drilling process (laser percussion drilling) has been presented which shows the potential and versatility of the electrochemical hole drilling processes.
Abstract: Electrochemical machining processes provide a viable alternative for drilling macro- and micro-holes with exceptionally smooth surface and reasonably acceptable taper in numerous industrial applications particularly in aerospace, electronic, computer and micro-mechanics industries. Advanced hole-drilling processes like jet-electrochemical drilling have found acceptance in producing large number of quality holes in difficult-to-machine materials. This paper highlights the recent developments, new trends and the effect of key factors influencing the quality of the holes produced by these processes. A comparative study of electro jet drilling with another non-traditional hole-drilling process (laser percussion drilling) has been presented which shows the potential and versatility of the electrochemical hole drilling processes.

Journal ArticleDOI
TL;DR: In this paper, the effect of the machining conditions on the fatigue life was investigated through a fatigue test using the specimen finished under various cutting conditions, and it was shown that it is possible to get longer fatigue life for machined parts than the virgin material or the carefully finished material without affected layer.
Abstract: The affected layer is generated within the machined surface layer through the cutting process. Cutting conditions such as the nose radius of the tool, feed rate and shape of cutting edge at the finishing operation affect the residual stress, surface hardness, and surface roughness. In this paper, it is shown that such machined surface property could be controlled by the setting of the cutting conditions to some extent. Then the effect of the machining conditions on the fatigue life was investigated through a fatigue test using the specimen finished under various cutting conditions. It was shown that it is possible to get longer fatigue life for machined parts than the virgin material or the carefully finished material without affected layer, only by setting the proper cutting conditions. Such a situation was realized when the generated residual stress was small and the induced surface hardness was high. A longer fatigue life for the machined components can be obtained by applying such cutting conditions as a low feed rate, a small corner radius and a chamfered cutting edge tool.

Journal ArticleDOI
TL;DR: In this article, a special technique using medical equipment for computerized tomography is presented for the evaluation of delamination damage in carbon fiber-based composites, which is compared to techniques using ultrasonic and is demonstrated as a feasible and an effective tool for evaluation of drilling-induced delamination.
Abstract: Whilst drilling is the most frequently employed operation of secondary machining for structure joining, delamination is a very serious defect during drilling of fiber-reinforced composite materials,. The evaluation of the delamination damage in the material is important but rather difficult, particularly for carbon fiber-based composites, because their colour makes visual inspection difficult. A special technique using medical equipment for computerized tomography is presented in this paper. It is compared to techniques using ultrasonic and is demonstrated as a feasible and an effective tool for the evaluation of drilling-induced delamination.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the stability of 2-dof milling by using the zeroth order approximation (ZOA) and semi-discretization (SD) methods.
Abstract: Stability of 2-dof milling is investigated. Stability boundaries are predicted by the zeroth order approximation (ZOA) and the semi-discretization (SD) methods. While similar for high radial immersions, predictions of the two methods grow considerably different as radial immersion is decreased. The most prominent difference is an additional type of instability causing periodic chatter which is predicted only by the SD method. Experiments confirm predictions of the SD method, revealing three principal types of tool motion: periodic chatter-free, quasi-periodic chatter and periodic chatter, as well as some special chatter cases. Tool deflections recorded during each of these motion types are studied in detail.

Journal ArticleDOI
TL;DR: In this article, the results of application of different coolant strategies to high-speed milling of aluminum alloy A356 for automotive industry were described and the effect of flood coolant, dry cutting, and minimum quantity of lubricant (MQL) technologies on tool wear, surface roughness and cutting forces were investigated.
Abstract: This paper describes the results of application of different coolant strategies to high-speed milling of aluminum alloy A356 for automotive industry. The paper investigates the effect of flood coolant, dry cutting, and minimum quantity of lubricant (MQL) technologies on tool wear, surface roughness and cutting forces. The cutting speed range was up to 5225 m/min. The feed rate used was up to 20 m/min. The result of MQL application is compared with dry milling and milling with flood coolant application. It was found that the MQL technology could be a viable alternative to the flood coolant application. The adhesive tool wear mechanism and adhesion activated surface quality deterioration are revealed and the role of lubricant in their reduction is defined.

Journal ArticleDOI
TL;DR: In this paper, a finite element thermo-mechanical model with mechanical tool loading was developed considering a uniform value for contact conductance and used for predicting the stress at the workpiece and backplate interface.
Abstract: Thermo-mechanical simulation of friction stir welding can predict the transient temperature field, active stresses developed, forces in all the three dimensions and may be extended to determine the residual stress. The thermal stresses constitute a major portion of the total stress developed during the process. Boundary conditions in the thermal modeling of process play a vital role in the final temperature profile. The heating and cooling rates with the peak temperature attained by the workpiece determine the thermal stress. Also, predicting realistic peak temperature becomes important as the operating temperature at the interface of tool-workpiece is very close to the solidus temperature of the aluminum workpiece. The convection heat-transfer coefficients of the surfaces exposed to air can be theoretically determined using Newton's law of cooling. Contact conductance depends on the pressure at the interface and has a non-uniform variation. The actual pressure distribution along the interface is dependent on the thermal stress from local temperature and non-linear stress–strain state. Therefore, applying an adaptive contact conductance can make the model more robust for process parameter variations. A finite element thermo-mechanical model with mechanical tool loading was developed considering a uniform value for contact conductance and used for predicting the stress at the workpiece and backplate interface. This pressure distribution contours are used for defining the non-uniform adaptive contact conductance used in the thermal model for predicting the thermal history in the workpiece. The thermo-mechanical model was then used in predict stress development in friction stir welding.

Journal ArticleDOI
TL;DR: In this article, an artificial neural network (ANN) model was developed for the analysis and prediction of the relationship between cutting and process parameters during high-speed turning of nickel-based, Inconel 718, alloy.
Abstract: An artificial neural network (ANN) model was developed for the analysis and prediction of the relationship between cutting and process parameters during high-speed turning of nickel-based, Inconel 718, alloy. The input parameters of the ANN model are the cutting parameters: speed, feed rate, depth of cut, cutting time, and coolant pressure. The output parameters of the model are seven process parameters measured during the machining trials, namely tangential force (cutting force, Fz), axial force (feed force, Fx), spindle motor power consumption, machined surface roughness, average flank wear (VB), maximum flank wear (VBmax) and nose wear (VC). The model consists of a three-layered feedforward backpropagation neural network. The network is trained with pairs of inputs/outputs datasets generated when machining Inconel 718 alloy with triple (TiCN/Al2O3/TiN) PVD-coated carbide (K 10) inserts with ISO designation CNMG 120412. A very good performance of the neural network, in terms of agreement with experimental data, was achieved. The model can be used for the analysis and prediction of the complex relationship between cutting conditions and the process parameters in metal-cutting operations and for the optimisation of the cutting process for efficient and economic production.

Journal ArticleDOI
TL;DR: In this article, the effect of surfactant and Al powders added in the dielectric on the surface status of the workpiece after EDM is investigated, and it is observed the best distribution effect is found when the concentrations of the Al powder and surfactants are 0.1 and 0.25 g/L, respectively.
Abstract: Electrical discharge machining (EDM) process is widely used to process hard materials in the industry. Electrical discharge distribution effects can be achieved by the addition of Al powder in the dielectric. A fine surface roughness value of the workpiece is thus obtained. However, the electrostatic force among fine Al particles is found to agglomerate the Al powders in the dielectric. A surfactant can be adopted to separate the Al powder in the dielectric homogenously. A better surface even the mirror-like quality of the EDMed workpiece is thus desired. In the study, the effect of surfactant and Al powders added in the dielectric on the surface status of the workpiece after EDM is investigated. It is observed the best distribution effect is found when the concentrations of the Al powder and surfactant in the dielectric are 0.1 and 0.25 g/L, respectively. An optimal surface roughness (Ra) value of 0.172 μm is achieved under the following parameter—positive polarity, discharge current 0.3 A, pulse duration time 1.5 μs, open circuit potential 140 V, gap voltage 90 V and surfactant concentration 0.25 g/L. The surface roughness status of the workpiece has been improved up to 60% as compared to that EDMed under pure dielectric with high surface roughness Ra of 0.434 μm.

Journal ArticleDOI
TL;DR: In this paper, the authors focused on the combined study of the evolution of tool wear, quality of machined holes and surface integrity of work-piece, in the dry drilling of alloy Ti-6Al-4V.
Abstract: This work is focused on the combined study of the evolution of tool wear, quality of machined holes and surface integrity of work-piece, in the dry drilling of alloy Ti–6Al–4V. Tool wear was studied with optical microscope and SEM–EDS techniques. The quality of machined holes was estimated in terms of geometrical accuracy and burr formation. Surface integrity involves the study of surface roughness, metallurgical alterations and microhardness tests. The end of tool life was reached because of catastrophic failure of the drill, but no significant progressive wear in cutting zone was observed previously. High hole quality was observed even near tool catastrophic failure, evaluated from the point of view of dimensions, surface roughness and burr height. However, microhardness measurements and SEM–EDS analysis of work-piece showed important microstructural changes related with a loss of mechanical properties. Depending on the application of the machined component, the state of the work-piece could be more restrictive than the tool wear, and the end of tool life should be established from the point of view of controlled damage in a work-piece.

Journal ArticleDOI
TL;DR: In this article, an elasto-plastic finite element (FE) model is presented to simulate the erosion process in 3D configuration, which takes into account numerical and material damping, thermal elasticplastic material behavior and the effect of multiple particle impacts as well as material removal.
Abstract: Material damage caused by the attack of particles entrained in a fluid system impacting a surface at high speed is called ‘Erosion’. Erosion is a phenomenon that takes place in several engineering applications. It also can be used in several manufacturing process such as abrasive waterjet machining. Erosion is a complex process dependent on particle speed, size, angle of attack as well as the behavior of the eroded material. Extensive experimental results have been reported in the literature on the erosion of different materials. Simulating the erosion process through finite element enables the prediction of erosion behavior of materials under different conditions, which will substitute the need of experimentation, and will enable the identification of constants required for existing analytical models. In this paper, an elasto-plastic finite element (FE) model is presented to simulate the erosion process in 3D configuration. The FE model takes into account numerical and material damping, thermal elastic–plastic material behavior and the effect of multiple particle impacts as well as material removal. The workpiece material modeled was Ti–6Al–4V. The effects of strain hardening, strain rate and temperature were considered in the non-linear material model. Comparison against results reported in literature and erosion models by Finnie, Bitter and Hashish are made. It is shown that the predicted results are in agreement with published results obtained experimentally and from analytical erosion models.

Journal ArticleDOI
TL;DR: In this article, an intelligent tool breakage detection system which uses a support vector machine (SVM) learning algorithm is proposed to provide the ability to recognize process abnormalities and initiate corrective action during a manufacturing process, specifically in a milling process.
Abstract: In this paper, an intelligent tool breakage detection system which uses a support vector machine (SVM) learning algorithm is proposed to provide the ability to recognize process abnormalities and initiate corrective action during a manufacturing process, specifically in a milling process The system utilizes multiple sensors to record cutting forces and power consumptions Attention is focused on training the proposed system for performance improvement and detecting tool breakage Performance of the developed system is compared to the results from an alternative detection system based on a multiple linear regression model It is expected that the proposed system will reduce machine downtime, which in turn will lead to reduced production costs and increased customer satisfaction

Journal ArticleDOI
TL;DR: A process monitoring and diagnosis approach based on a Bayesian belief network for incorporating multiple process metrics from multiple sensor sources in sequential machining operations to identify the root cause of process variations and provide a probabilistic confidence level of the diagnosis.
Abstract: This paper addresses the challenges inherent in root cause diagnosis of process variations in a production machining environment. We develop and present a process monitoring and diagnosis approach based on a Bayesian belief network for incorporating multiple process metrics from multiple sensor sources in sequential machining operations to identify the root cause of process variations and provide a probabilistic confidence level of the diagnosis. The vast majority of previous work in machining process monitoring has focused on single-operation tool wear monitoring. The focus of the present work is to develop a methodology for diagnosing the root cause of process variations that are often confounded in process monitoring systems, namely workpiece hardness, stock size, and tool wear variations. To achieve this goal, multiple sensor metrics have been identified with statistical correlations to the process faults of interest. Data from multiple sensors on sequential machining operations are then combined through a causal belief network framework to provide a probabilistic diagnosis of the root cause of the process variation.

Journal ArticleDOI
TL;DR: In this paper, the dimensional and material characteristics of directed deposited H13 tool steel by CO 2 laser are investigated for the DMD process with a feedback height control system using statistical techniques.
Abstract: Laser aided direct metal/material deposition (DMD) process builds metallic parts layer-by-layer directly from the CAD representation. In general, the process uses powdered metal/materials fed into a melt-pool, creating fully dense parts. Success of this technology in the die and tool industry depends on the parts quality to be achieved. To obtain designed geometric dimensions and material properties, delicate control of the parameters such as laser power, spot diameter, traverse speed and powder mass flow rate is critical. In this paper, the dimensional and material characteristics of directed deposited H13 tool steel by CO 2 laser are investigated for the DMD process with a feedback height control system. The relationships between DMD process variables and the product characteristics are analyzed using statistical techniques. The performance of the DMD process is examined with the material characteristics of hardness, porosity, microstructure, and composition.

Journal ArticleDOI
TL;DR: A number of different approaches have been proposed by various researchers that attempt to effectively address the problem of tracking and contour errors in CNC machine tools as mentioned in this paper, which is a complex interaction of several factors that includes the basic design of the machine as well as the capability and performance of the corresponding axis servo system.
Abstract: The dynamic response of a machine tool is a complex interaction of several factors that includes the basic design of the machine as well as the capability and performance of the corresponding axis servo system. In terms of the performance of the servo system, tracking and contour errors are two important aspects that significantly affect the machine tool. Extensive research has been conducted over the last several decades into the study of these error components. A number of different approaches have been proposed by various researchers that attempt to effectively address this problem. This paper attempts to study the work that has been carried out in minimising tracking and contour errors in CNC machine tools.

Journal ArticleDOI
TL;DR: In this paper, a capacitance displacement sensor is integrated into the spindle and measures static and dynamic variations of the gap between the sensor head and the rotating spindle shaft under cutting load.
Abstract: This article presents a method of measuring cutting forces from the displacements of rotating spindle shafts. A capacitance displacement sensor is integrated into the spindle and measures static and dynamic variations of the gap between the sensor head and the rotating spindle shaft under cutting load. To calibrate the sensing system, the tool is loaded statically while the deflection of the tool is measured with the capacitance probe. With this calibration, the displacement sensor can be used as an indirect force sensor. However, the measurement bandwidth is limited by the natural modes of the spindle structure. If cutting force frequency contents are within the range of the natural modes of the spindle structure or higher, the measurements are distorted due to the dynamic characteristics of the spindle system. In order to increase the bandwidth of the indirect force sensor by compensating for the spindle dynamics, the design of a Kalman filter scheme, which is based on the frequency response function (FRF) of the displacement sensor system to the cutting force, is presented in this paper. With the suggested sensing and signal processing method, the frequency bandwidth of the sensor system is increased significantly, from 350 to approximately 1000 Hz. The proposed indirect force sensor system is tested experimentally by conducting cutting tests up to 12,000 rpm with a five-fluted end mill. Besides cutting forces, the measured displacements can also be affected by factors such as roundness errors, unbalance at different speeds, or dilatation of the spindle shaft due to temperature variations. Methods to compensate for these disturbing effects are also described in the paper.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a tool wear measurement method using projected laser raster lines on a tool surface to obtain a 3D image of the relief surface of a tool without using a very complicated measuring system.
Abstract: This paper suggests a reliable direct measuring procedure for measuring different tool wear parameters. Modern image processing techniques and machine vision systems today enable direct tool wear measurement to be accomplished in-cycle. The presented system is characterized by its measurement flexibility, high spatial resolution and good accuracy. The system consists of a light source to illuminate the tool, CCD camera, laser diod (used in conjunction with profile deepness assessment) with linear projector, grabber for capturing the picture, and a PC. The technique is specially characterized by its determination of profile deepness with the help of projected laser raster lines on a tool surface. So it has advantage comparing with other techniques, which can measure only 2D profiles. With the technique presented in this paper a 3D image of relief surface can be obtained without having need to employ a very complicated measuring system. All indirect methods like acoustic emission, force measurement, spindle current measurement, vibration sensors, etc. are very time consuming and demand very expensive subsidiary measurement equipment, compared with the method presented here.

Journal ArticleDOI
TL;DR: In this article, a hybrid approach of 3D welding and milling is proposed, which uses gas metal arc welding as an additive and subtractive technique, thereby exploiting the advantages of both processes.
Abstract: Solid Freeform Fabrication (SFF) gives engineers a new freedom to build parts that have thus far proved difficult to manufacture using conventional machining. However, the surface finish and accuracy of SFF parts are lower than those of conventionally machined parts. A process combination of additive and subtractive techniques is currently being developed in order to overcome this problem. A novel hybrid approach of our group called ‘3D welding and milling’ uses gas metal arc welding as an additive and milling as a subtractive technique, thereby exploiting the advantages of both processes. Compared to other deposition processes, gas metal arc welding is the most economic way of depositing metals. In this paper, the initial results of the process development and the characterization of the parts fabricated by this process are reported.

Journal ArticleDOI
TL;DR: In this article, the effects of backup plate on delamination in composite materials using saw drill and core drill were analyzed and compared with that without backup plate, showing that the use of back-up plate does reduce the delamination.
Abstract: Machining of composites has caught greater attention in manufacturing of structural parts in aerospace, automobile and sporting goods Composite materials have advantageous features in strength and stiffness coupled with lightweight compared to the conventional metallic materials Amongst all machining operations, drilling is the most commonly applied method for generating holes for riveting and fastening the structural assembly Delamination is one of the serious concerns in drilling holes in composite materials at the bottom surface of the workpiece (drill exit) Quite a few references of the drilling of fiber-reinforced plastics report that the quality of cut is strongly dependent on drilling parameter as well as the drill geometry Saw drills and core drills produce less delamination than twist drills by distributing the drilling thrust toward the hole periphery Delamination can be effectively reduced or eliminated by slowing down the feed rate when approaching the exit and by using back-up plates to support and counteract the deflection of the composite laminate leading to exit side delaminations The use of the back-up does reduce the delamination in practice, which its effects have not been well explained in analytical fashion This paper predicts the effects of backup plate on delamination in drilling composite materials using saw drill and core drill The critical drilling thrust force at the onset of delamination is calculated and compared with that without backup The well known advantage of industrial use of backup can be understood fundamentally by the fact that the threshold thrust force at the onset of delamination is increased making the delamination less induced

Journal ArticleDOI
TL;DR: In this article, wire electrical discharge machining (WEDM) is adopted in machining Al2O3p/6061Al composite, and 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.
Abstract: 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.

Journal ArticleDOI
TL;DR: In this paper, an integrated recurrent neural network (IRNN) is introduced to identify the nonstationarity of the thermo-elastic process with a deterministic linear trend.
Abstract: This paper presents a new modeling methodology for nonstationary machine tool thermal errors. The method uses the dynamic neural network model to track nonlinear time-varying machine tool errors under various thermal conditions. To accommodate the nonstationary nature of the thermo-elastic process, an Integrated Recurrent Neural Network (IRNN) is introduced to identify the nonstationarity of the thermo-elastic process with a deterministic linear trend. Experiments on spindle thermal deformation are conducted to evaluate the model performance in terms of model estimation accuracy and robustness. The comparison indicates that the IRNN performs better than other modeling methods, such as, multi-variable regression analysis (MRA), multi-layer feedforward neural network (MFN), and recurrent neural network (RNN), in terms of model robustness under a variety of working conditions.