International Journal of Mechatronics and Manufacturing Systems (11 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.
Co-spray-formed graded steel for micro rotary swaging tools
by Chengsong Cui, Alwin Schulz, Eric Moumi, Bernd Kuhfuss, Florian Böhmermann, Oltmann Riemer
Abstract: Micro rotary swaging tools are required to have different material properties in different functional areas. These requirements can be fulfilled by applying different materials in the specific regions of the tools. The different materials can be combined with a gradient zone in between to reduce critical stresses at the interface during heat treatment and in swaging process. Such graded tool materials are supposed to be manufactured by means of a newly developed co-spray forming process. In this study, a flat deposit of graded tool steel (HS6-5-3C/HS6-5-2C) was produced via co-spray forming, followed by hot rolling and heat treatment. Micro infeed rotary swaging tools with fine geometrical structures were precisely machined from the graded steel. The tool performance during swaging of stainless steel wires was evaluated.
Keywords: micro forming; rotary swaging; tool steel; spray forming.
Wear resistance performance of boron nitride coatings on end milling cutters
by Baris Çetin, Goksel Durkaya, Huseyin Kurtuldu, Tugce Hacaloglu, Merve Gurbuz, Bilgin Kaftanoğlu
Abstract: For defence industry applications, the machining of ultra-high strength steels or aluminium with ballistic temper grades is a widely-used operation. Therefore, it is a great challenge to find an optimum solution for tool wear. In that sense, tool coatings provide various solutions for machining of hard materials or improving wear resistance. A cost-effective tool coating provides longer tool life, hence decreases the tool cost contribution in production. Boron nitride (BN) coating could be thought as a new generation coating method compared to titanium nitride (TiN), aluminium titanium nitride (AlTiN) or silicon aluminium oxy-nitride (SiAlON). BN coating material has a great strength, toughness and chemical stability whereas it has an important disadvantage of high intrinsic stress. In this industrial study, standard end mill cutters are coated with BN material by physical vapour deposition (PVD) method. The coated and uncoated milling tools are compared according to their wear resistance and the obtained workpiece surface roughness. First results of the study are presented in this paper.
Keywords: wear; end milling; BN coating.
Integrated optimisation method for controlled dynamic mechanical systems
by Yanwei Wang, Yan Wang, Hanxin Chen
Abstract: It is difficult to consider the interaction among mechanical parts, mechanical system and control system when carrying out design optimisation of mechatronic products which are usually controlled dynamic mechanical systems. A cosimulation based integrated optimisation method, which achieve topology optimisation of mechanical parts, mechanical system optimisation and controller parameter optimisation in one optimisation process, is presented. The proposed optimisation process considers the interaction among mechanical parts, the mechanical system and the control system within a controlled dynamic mechanical product. The principles of the optimisation process and a software framework are given. Different discipline software tools can run automatically in the presented framework. With the integrated optimisation process, the mechanical properties of the parts, the dynamics performance of the mechanical system and the overall dynamic properties of the mechatronic product can simultaneously achieve the optimum. The effectiveness is verified by a controlled crank-connecting rod mechanism with a flexible connecting rod.
Keywords: mechatronic product; integrated optimisation; PID control; topology optimisation; dynamic mechanical system.
Interactive programming of industrial robots for edge tracing using a virtual reality gaming environment
by S. Michas, E. Matsas, G-C. Vosniakos
Abstract: This paper presents the methodology and development tools employed to specify the path of an industrial robot in a virtual environment (VE) that is typically used for game development. Initially, the cell and the robot are designed and then imported into the VE, followed by the development of the kinematic chain of the robot. Forward and inverse kinematics analysis of the robot is accomplished, implemented in the C# programming language and embedded into the VE vie inbuilt functionality. The end-effector path consists of edges to be traced, such as in welding, deburring, water jet machining, etc. The path is planned in the VE using the teaching or lead-through paradigm, where instead of a teaching pendant the controller of a computer game console is used in connection with visual aids augmenting the VE to help the programmer. The robot path is, then, transcribed in the real robot, the pertinent code being derived automatically within the VE. The method was applied to a 6-axis industrial robot, the obtained V+ program was run on the real robotic cell and accuracy attained was documented proving that user friendly VR interfaces deriving from the gaming world can provide an efficient and effective robot programming paradigm.
Keywords: industrial robot; robotic manufacturing cell; virtual reality; interactive path planning; virtual manufacturing; robot kinematics; game development.
Dynamic modelling and vibration simulation of air bearing spindle systems due to unbalance
by Hongrui Cao, Oltmann Riemer, Ekkard Brinksmeier
Abstract: Air bearing spindles are popularly used in ultra-precision machining, however, any slight mass unbalance in spindles can induce vibrations which may result in dimensional errors or poor surface finish of fabricated parts. In this paper, a complete dynamic model is proposed for air bearing spindle systems including air bearings, shaft, housing, and joint connections with the machine tool structure. The model is validated with experiments, and then vibration responses due to different types of unbalance are simulated quantitatively to reveal the characteristics of unbalance-induced vibrations. The results can provide proofs for the position selection of balancing planes as well as measurement points in automatic balancing process of air bearing spindles.
Keywords: dynamic modelling; vibration simulation; unbalance; air bearing spindles; ultra-precision machining.
Special Issue on: Advances in Intelligent Machine Tools and Manufacturing
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.