International Journal of Mechatronics and Manufacturing Systems (17 papers in press)
A STRATEGY FOR ACHIEVING ACCURATE BENDING BY MULTI-PASS LASER LINE HEATING
by Polash Dutta, U.S. Dixit, Karuna Kalita
Abstract: Laser bending has emerged as a promising technique to bend sheet metals by thermal residual stresses in the last two decades. Several mathematical models are available to predict the bend angle after the laser bending process. However, due to the limitations in the mathematical models and precision of input parameters, the sufficiently accurate prediction of bend angle is not possible. In this work, a strategy is proposed for choosing the parameters of multi-pass laser line heating for obtaining an accurate bend angle when the accuracy of prediction is known. The guidelines have also been provided for ascertaining the accuracy of prediction. The strategy is verified with experiments for three different materials.
Keywords: laser bending; precision manufacturing; laser; heuristic method; line heating; mild steel; aluminum alloy; stainless steel.
Micro drilling of hard-to-cut materials: an experimental analysis.
by Aldo Attanasio
Abstract: The introduction of machine tools specifically designed and industrialized for micro cutting processes, the development of high performance micro tools, and the possibility of easily realizing complex shaped surfaces have increased the competitiveness and the industrial interest on these processes. Consequently, many researchers are studying the phenomena involved in the mechanics of micro cutting processes. This paper is focused on the micro drilling process for difficult to cut materials. An experimental analysis, consisting tool life tests, was performed with the aim of highlighting limits and advantages of this cutting process. Three hard-to-cut alloys, namely AISI 310H stainless steel, Hastelloy C22 and Inconel 625 nickel based alloys, were tested. By using standard micro drills, holes 500
Keywords: hard-to-cut material; hard machining; micro machining; drilling; experimental analysis.
Prediction of formability of adhesive bonded sheets through neural network
by Satheeshkumar V, R.Ganesh Narayanan, Deepak Sharma
Abstract: The present work aims to predict the formability of adhesive bonded sheets accurately. The difficulty during incorporation of accurate adhesive and adhesion properties in finite element (FE) simulations predicting the formability is addressed. Here an artificial neural network (ANN) model is developed based on the experimental data of adhesive bonded sheets which inherently includes actual properties of adhesive and adhesion. Feed forward back propagation algorithm is used for predicting forming limit from tensile test and cup height from deep drawing process. In FE simulations, thickness heterogeneities with factor f have been designed in the base materials to predict the forming limit without adhesive and adhesion properties. The ANN results are validated through experimental results and also compared with FE results. A good correlation between experimental and ANN predicted results, and a considerable variation with FE results confirm the viability of ANN for predicting the formability of adhesive bonded sheets accurately.
Keywords: Adhesive bonded sheets; Neural network; Numerical Prediction; Tensile behaviour; Deep drawing; Forming limit; Cup height; Feed forward back propagation algorithm; Thickness heterogeneity; Adhesive properties.
Zero Magnitude-Error Tracking Control for Servo System with Extremely Low-resolution Digital Encoder
by Zhenyu Zhang, Nejat Olgac
Abstract: Harmonic magnitude control presents no particular difficulty when it uses appropriate sensors. The size, costs and accessibility of technology of these hardware may, however, severely constrain the capabilities in particular applications. Very commonly used extremely low-resolution encoders, for instance, present two complications, (a) large quantization errors at and between two successive measurements; (b) stochasticity of actual amplitude given the desired discrete encoder readings. This paper proposes a method which enables accurate peak-to-peak stroke control when extremely low-resolution encoder is utilized. Essentially it treats a stochastic stroke control problem by converting it into a deterministic one. The proposed control strategy consists of a two-stage tuning: (I) coarse tuning which results in desired encoder readings in peak-to-peak swings, (II) fine tuning which adapts the control gains to achieve the actual peak-to-peak stroke based on the derived deterministic relationships between the amplitude and encoder readings. Simulations and experiments are provided to validate the proposed method.
Keywords: Extremely low-resolution digital encoder; Zero magnitude error tracking; Servo control; ICSI.
Dynamics and chatter analysis in robotic milling
by yiqing yang, xingzheng pei, xi wang
Abstract: The industrial robot has been employed in the field of machining processes due to its high flexibility, while its applications are restricted by the structural disadvantages (i.e. poor stiffness and low positional accuracy). The robotic high flexibility is evidenced by the ability of reaching a specified position through various postures. Therefore it is important to identify the dynamic behaviors of a specific point at different postures. The frequency responses of the cutter tip of a robot are measured by separating the working area into several layers. The result shows that dynamic characteristics are dependent on posture. The critical depth of cut is ranged from 0.35 mm to 0.93 mm by taking an example of spindle speed 2000 rpm. And the critical depth of cut when feeding in Y direction is much larger than the X direction.
Keywords: industrial robot; milling; modal analysis; chatter stability
Experimental Investigations into Rotary Magnetic Field and Tool assisted Electric Discharge Machining using Magneto Rheological Fluid as Dielectric
by Lokesh Upadhyay, M. L. Agarwal, Pulak M Pandey
Abstract: The present study focuses on the development of an electric discharge machining method that used magneto rheological fluid as dielectric and rotary magnetic field assisted electric discharge tool. The work aims to improve performance of electric discharge machining by utilizing the combined effect of magneto rheological fluid with rotating electrode and magnetic field. This developed hybrid machining process has been designed to attain higher material removal rate for improving production rate. In this process, the surface roughness has been found higher as compared to when magnetic field and tool was kept stationary. M2 grade high speed steel workpiece was used for parametric study. The experimentation was performed to evaluate the effect of percentage contribution of alumina particles, discharge current, duty cycle, and pulse on time effect on material removal rate and surface roughness. The experimental findings demonstrated that EDM process with rotary magnetic field and tool with magneto rheological fluid as dielectric resulted in an increased material removal rate as compared to EDM with static magnetic field and tool. The following findings were found significant for a certain limit of carbonyl iron percentage in magneto rheological fluid.
Keywords: Electric discharge machining, roughness, magneto rheological fluid, alumina.
Modeling and Analysis of Tool Deflections in Tailored Micro End Mills
by Samad Nadimi Bavil Oliaei, Yigit Karpat
Abstract: The deflection of micro end mills has a detrimental effect on surface quality of the machined micro components and adversely affects the achievable dimensional and geometrical tolerances. In this paper, the analysis and modeling of tool deflections of tailored micro end mills have been considered. The tool deflections are obtained using analytical models as well as finite element simulations, and verified using a dedicated measurement setup, which uses a capacitive sensor with a nanometer resolution for static tool deflection measurements. The optimization of the micro end mill geometry has been performed to determine optimum neck taper angle and transition radius of the single edge micro end mill to have minimum tool deflections. With the developed model, tool failure predictions for a given process parameter set can be performed and it can be used for better micro milling process planning.
Keywords: Micromilling; Tailored Micro End Mill; Tool Deflection; Optimization; Tool Failure
Special Issue on: ICHSM2016 Advances in Machine Tools and Monitoring Systems
Diversity of Assembly Error Migration and Its Solution Model for Heavy Duty Machine Tool
by Bin Jiang, Yunpeng Gu, Tiantian He, Shouzheng Sun, Chongmin Jiang
Abstract: Aiming at the ever-changing assembly error along with operation in the large scale assembly space, the diversity of machine tool assembly error migration and its operation route are characterized by making use of the correspondence relationship between joint surface error and operation distance. The formation and retention of assembly error are respectively revealed by the forward migration and the reverse migration of assembly error. Furthermore, the delayed step function of assembly error migration is constructed to recognize the potential control operation of error migration. Based on the response surface method, the solution model of assembly error migration is established to reveal the diversity of assembly error migration process and the effect of multiple operations. Finally, the design method of assembly process about heavy duty machine tool is proposed, and its effectiveness is verified by gantry-moving type turning-milling machining centre.
Keywords: heavy duty machine tool; assembly error; assembly operation; error migration; delayed step function; response surface method.
Experimental Investigation on Surface Quality in Ultrasonic Vibration Assisted High Speed Grinding of BK7 Optical Glass
by Ming Zhou, Peiyi Zhao, Huang Shaonan
Abstract: Knowledge of surface formation mechanism plays a key role in implementing precision machining of optical glass. In order to evaluate the surface quality and to explore surface formation mechanism, in this paper, ultrasonic vibration assisted grinding (UVAG) experiments were carried out on BK7 optical glass by employing diamond wheel. Quite a few micro and macro brittle-fractured pits of different shapes, sizes and morphologies were observed on machined surfaces by using scanning electron microscope. Spindle rotation speed, feed rate, grinding depth and ultrasonic vibration amplitude had be found to exert significant effects on the surface generation and machined surface roughness in ultrasonic vibration assisted grinding of this kind of materials. It was also demonstrated that the value of machined surface roughness would become much smaller if the pits size was small. Based on the observation and classification of pits morphologies, the machined surfaces forming mechanism was extensively investigated in this work.
Keywords: Surface formation; Optical glass; Ultrasonic vibration; Grinding.
Special Issue on: Advances in Intelligent Machine Tools and Manufacturing
Simulation of surface structuring considering the acceleration behavior by means of spindle control
by Dennis Freiburg, Felix Finkeldey, Michael Hensel, Petra Wiederkehr, Dirk Biermann
Abstract: Due to the increasing demands on surface quality of machined surfaces, deviations of the feed velocity, which can occur in complex 5-axis milling processes and are caused by the insufficient acceleration and deceleration behaviour of the machining centre, have to be avoided. This is crucial in the case of surface structuring by means of high-feed milling. The high-feed rate can be used to generate quasi-deterministic surface structures on forming tools. Applying surface structures for forming processes, the friction can be tailored to improve the form filling of small cavities. However, in order to generate homogeneous surface structures, it is important to ensure a constant feed per tooth during the milling process. Inrnthis work, a novel approach for the predicting surface structures using a geometric physically-based simulation system is shown. Furthermore, an empirical model was developed which represents the acceleration and deceleration behaviour of the used machining centre for predicting the deviations of the feed rate. Therefore, it is possible to take the alternating feed rate into account when simulating the milling process. In addition, an control approach, for adapting the spindle speed online, is used to keep the tooth feed constant.
Keywords: Milling simulation; Surface structuring; Control
High Strength Aluminum Alloy Fatigue Damage Alert of High Speed Train Gearbox Shell Using Acoustic Emission Instrument
by Yibo Ai, Tao Lv, Weidong Zhang
Abstract: As a key component of high speed train, the gearbox shell must be running safely. The main damage form of high speed train gearbox shell is fatigue, and to effectively predict the working state and give out safety alert is of great significance of operation safety. In this study, the acoustic emission instrument has been used for real-time and non-destruction monitoring fatigue damage progress of high strength aluminum alloy which is the material of high speed train gearbox shell. By comparing with the fatigue damage progress, the feature parameter and its threshold of acustic emission (AE) signal for classifying the states has been defined. The consistence of the feature is discussed by Hurst index method. A particle swarm opimization least square support vector machines (PSO-LSSVM) prediction model has been designed to predict the feature of next step, and the safety alert is given by comparing with the threshold of the feature. In this study, the prediction result is about 600s to 1600s earlier than the critical time, and by comparing acceleration test and real condition, it can give enough time for the train to stop and evacuate passengers.
Keywords: High strength aluminum alloy; material fatigue damage; acoustic emission; safety alert; PSO method; SVM method; high speed train gearbox.
Experimental investigation on tool wear and measurement method in micro milling with carbide tools
by Yanshuai Yang, Yu Liu, Kuo Liu
Abstract: In this paper, the carbide tool wear in micro milling is investigated and a new tool wear measurement method is proposed. Al7075 alloy and C45 steel is used as the work-piece materials due to their common application. The cutting tools with different machining time are obtained by experiments and the states of tool wear with different work-piece materials are compared. The influence of tool wear on micro milling forces and surface topographies is studied through experiments. The traditional tool wear measurement methods based on the tool edge radius, tool diameter and flank wear width are introduced. For a more complete explanation of the tool wear, a new tool wear measurement method based on the wear area is proposed. The carbide tool wear values based on the tool edge radius, tool diameter, and flank wear width and wear area are measured and the tool wear process is obtained. Compared with the traditional methods, the new tool wear measurement method based on the wear area can explain the tool wear process more reasonable.
Keywords: micro milling; tool wear; wear measurement; tool edge radius; flank wear width.
Transient Morphology Analysis and Sparse Representation for Bearing Fault Diagnosis under Variable Speed Condition
by Juanjuan Shi, Nan Wu, Xingxing Jiang, Changqing Shen, Zhongkui Zhu
Abstract: Sparse representation has been extensively applied for bearing fault diagnosis under constant speed operation. However, its application to the variable speed case is confined as, unlike the constant speed case, the fault-induced transients under variable speed are more complex and the changing pattern of transient morphology along rotating speed is uncertain. As such, this paper firstly investigates the morphology of faulty bearing vibration response to reveal that the rotating speed variations have negligible effects on morphology of the fault-induced transients. Then an efficient dictionary spanned by a single atom can be constructed, where the optimal wavelet atom is selected by the correlation filtering strategy. The Stage-wise Orthogonal Matching Pursuit (StOMP) is subsequently adopted to enable the target signal to be sparsely represented and fast reconstructed. By analyzing the characteristic order extracted from the reconstructed signal, the fault diagnosis can be completed. The experimental signals validate the effectiveness of the proposed method.
Keywords: Bearing fault diagnosis; Variable speed; Dictionary construction; Sparse representation; Fault feature extraction.
Experimental study on the effect of coolant on the thermal characteristics of gear grinding machine under load
by Lijun Fan, Xiaojun Shi, Ke Zhu, Jianmin Gao
Abstract: It is very important to reduce the thermal deformation of machine tools for modern precision machining because the machining error induced by the thermal deformation is up to 75% of the total errors. In this paper a special measurement system was established for a five-axis gear grinding machine and the effect of coolant on thermal behavior of the machine tool during various grinding processes has been studied experimentally. The results show that the coolant has a strong influence on the thermal behavior. This is mainly because the coolant absorbs a large amount of cutting heat and the uneven flows of coolant on the bed surface increase the temperature gradient of the machine tool. In addition, coolant atomization lead to higher ambient temperature inside the machine tool housing. The measured thermally induced errors increase with the increase of the coolant temperature. Although coolant cause the machine tool temperature increase, it can also positively affect the thermal behavior if coolant is controlled to flow correctly and stabilize the machine tool temperature. In order to further reduce the thermal error, controlling coolant flow has to be considered in earl design stages.
Keywords: gear grinding machine; thermal characteristics; coolant; experimental study.
Special Issue on: Advances in Laser-Based Manufacturing
Effect of niobium on microstructure-property relationship in H11 hot-work tool steel via wire- and powder-based laser metal deposition
by Mahesh Teli, Fritz Klocke, Kristian Arntz, Kai Winands
Abstract: This paper presents an effect of niobium (Nb) on the microstructure-property relationship in H11 hot-work tool steel. Various amounts of Nb powder were introduced into the molten pool of H11 wire through a novel wire- and powder-based laser metal deposition (WP-LMD) process. With the increase in Nb content upto 3.45 wt.%, the average grain size of H11 decreased from 14.3 µm to 2.83 µm, while the average Vickers microhardness decreased from 706 HV0.2 to 301 HV0.2. The critical amount of Nb was then found to be 1.73 wt.%, which produced a hard (average hardness of 606 HV0.2), and refined (average grain size of 3.01 µm) microstructure of H11. Such kind of microstructures can assure high toughness and high hardness; hence more suitable for hot-working industries such as die & mold, forging and cutting tools.
Keywords: Laser metal deposition; AISI H11 wire; Niobium powder; Microstructure refinement; Toughness; Hardness.
Intelligent Scan Trajectories for Pulsed Laser Polishing
by Madhu Vadali, Chao Ma, Xiaochun Li, Frank Pfefferkorn, Neil Duffie
Abstract: The objective of this work is to generate irregular, smooth, adaptive laser scan trajectories for pulsed laser polishing. Traditionally pulsed laser polishing, like other surface finishing processes has used zig-zag scan paths. Zig-zag trajectories are simple in nature, are comprised of sharp turns, the dynamics of the positioning system are not considered, and more importantly are not adaptable because the path generation is independent of surface condition. In this paper, the authors present an intelligent scan trajectory generation scheme that can overcome these limitations. These trajectories are based on the artificial potential fields method of path planning that take the surface condition into account. Computer simulations are presented to illustrate the characteristics of the path and guidelines are developed for choosing the trajectory generation parameters. Experiments show that these trajectories result in marginal improvements in the average surface roughness when compared to the traditional zig-zag trajectories, all the while overcoming the limitations. Finally, smooth, irregular scan trajectories are generated for a micro end milled Ti6Al4V surface with a feature that needs no polishing, thus illustrating the versatility of the trajectory generations scheme.
Keywords: Laser; Polishing; Intelligent; Path planning; Surface Roughness; Zig-zag; Artificial fields; Marangoni flows; Smoothness; Micro Melting.
Metallurgical and tribological investigation of microscale fiber laser based surface hardening
by Yogesh Wagh, Santanu Paul, Neeraj Gupta, Ramesh Singh
Abstract: Laser surface hardening (LSH) is a useful technique to improve the hardness and wear resistance of the surfaces of critical structural components. Limited work has been reported in the literature on micro-scale LSH using fiber lasers, which provide precise control over the targeted areas. In this work, a comprehensive analysis of the mechanical, metallurgical and tribological responses of the various laser hardened patterns of EN-8 steel at different process conditions was conducted. A 100 W continuous wave fiber laser with specially designed optics varying the beam between ~200-900 μm was used for micro-scale hardening. Electron Backscatter Diffraction (EBSD) technique was used to investigate the microstructural variation and the hardness values were measured using micro hardness tester (Shimadzu-HMV). Additionally, to measure the tribological response, four different hardened patterns were analyzed using the pin on disk set-up (DUCOM wear and friction monitor TR-20LE). The preliminary results revealed improved surface hardness values with increase in percentage overlap due to the formation of martensite. Furthermore, it was observed that the average wear rate of hardened specimen decreases by ~91% as compared to the unhardened specimen. The results revealed an inverse relationship between friction force and percent-hardened area, with minimum friction force obtained for fully hardened pattern.
Keywords: Laser hardening; fiber laser; EBSD; wear and friction force.