A simulated investigation on the machining instability and dynamic surface generation

In this paper, the authors propose the generic concept of machining instability based on the analysis of all kinds of machining instable behaviors and their features. The investigation covers all aspects of the machining process, including the machine tool structural response, cutting process variables, tooling geometry and workpiece material property in a full dynamic scenario. The paper presents a novel approach for coping with the sophisticated machining instability and enabling better understanding of its effect on the surface generation through a combination of the numerical method with the characteristic equations and using block diagrams/functions to represent implicit equations and nonlinear factors. It therefore avoids the lengthy algebraic manipulations in deriving the outcome and the solution scheme is thus simple, robust and intuitive. Several machining case studies and their simulation results demonstrate the proposed approach is feasible for shop floor CNC machining optimisation in particular. The results also indicate the proposed approach is useful to monitor the machining instability and surface topography and to be potentially applied in adaptive control of the instability in real time

Optimization of 5-Axis milling processes based on the process models with application to airfoil machining

5-axis milling is widely used in machining of complex surfaces such as airfoils. Improper selection of machining parameters may cause low productivity and undesired results during machining. There are several constraints such as available power and torque, chatter stability, tool breakage etc. In order to respect such constraints proper machining parameters should be determined. In this paper, methodologies for improving 5-axis milling processes are presented. Selection of machining parameters is performed using process simulations. The developed methodologies are presented on an example airfoil

The effects of machining process variables and tooling characterisation on the surface generation: modelling, simulation and application promise

The paper presents a novel approach for modelling and simulation of the surface generation in the machining process. The approach, by integrating dynamic cutting force model, regenerative vibration model, machining system response model and tool profile model, models the complex surface generation process. Matlab Simulink is used to interactively perform the simulation in a user-friendly, effective and efficient manner. The effects of machining variables and tooling characteristics on the surface generation are investigated through simulations. CNC turning trials have been carried out to evaluate and validate the approach and simulations presented. The proposed approach contributes to comprehensive and better understanding of the machining system, and is promising for industrial applications with particular reference to the optimisation of the machining process based on the product/component surface functionality requirements

Machining dynamics: Fundamentals, applications and practices

Information regarding this edited book can be found at this link:Machining dynamics play an essential role in the performance of machine tools and machining processes in manufacturing. Current advances in computational modelling, sensors, diagnostic equipment and analysis tools,3D surface metrology and manufacturing science are giving researchers and practising engineers a new perspective on the machining process. Machining Dynamics: Fundamentals, Applications and Practices reflects the new integrated approach to studying machining dynamics by presenting state-of-the-art applications, practices and research in the field. Written by experts in each field, the first part of the book presents the basic theory, analysis and control methodology in addition to detailed modelling and diagnostic techniques for machining dynamics, while part two focuses on applying the fundamentals of machining dynamics in a variety of machining processes including turning, grinding, gear machining and nontraditional machining. Advanced undergraduate and postgraduate students studying manufacturing engineering and machining technology will find Machining Dynamics: Fundamentals, Applications and Practices a comprehensive and up-to-date introduction to the subject while the book’s thoroughness allows it to serve as a useful reference for manufacturing engineers, production supervisors, planning and application engineers and designers. The Springer Series in Advanced Manufacturing publishes the best teaching and reference material to support students, educators and practitioners in manufacturing technology and management. This international series includes advanced textbooks, research monographs, edited works and conference proceedings covering all subjects in advanced manufacturing. The series focuses on new topics of interest, new treatments of more traditional areas and coverage of the applications of information and communication technology (ICT) in manufacturing

Investigation on different composition of powder metallurgy electrode (Cu-W) in high performance edm (HPEDM) on AISI D2 hardened steel

The ideal selection of manufacturing conditions is one of the most important aspects to take into consideration in the majority of manufacturing processes and particularly in processes related to Electrical Discharge Machining (EDM). EDM die sinking machines are used to machine conductive metals of any hardness or difficult to machine with traditional methods. The problem in the capabilities of tool electrodes which are not utilized at the optimum levels of the operating parameters has attracted the attention of researchers and practicing engineers to manufacture tool electrodes with highly great performance. In this work, an experimental design was conducted to characterize the machining performances and surface integrity of three different composition of copper tungsten (CuW) tool electrode in EDM of D2 hardened steel (58-62 HRC). Machining performances i.e. material removal rate (MRR), tool wear rate (TWR), workpiece surface roughness (Ra) and micro-hardness (MH) were studied for the three different composition of CuW tool electrode made through powder metallurgy (PM) method. Machining variables were peak current and pulse duration, meanwhile machining voltage, depth of cut and duty factor were kept constant. The 65%W electrode is the best choice of CuW electrode on machining D2 hardened steel due to the highest machining rate, reasonable tool wear rate and acceptable surface characteristics. The improvement of MRR is obviously affected by the increment of current intensity. MRR increased as the value of peak current increased. The increment of pulse duration is not essentially improving MRR. There is no clear relation between the alteration of pulse duration and MRR. However, the MRR becomes the optimum at an optimal set of variables which is set at 40A and 400µs. The results of the machining performance can extent the availability of database on EDM machinability and surface characteristics of D2 hardened steel for machinist practices in industrial application of roughing operation

Energy-Efficient Machining Process Analysis and Optimisation Based on BS EN24T Alloy Steel as Case Studies

Computer Numerical Controlled (CNC) machining, which is one of the most widely-deployed manufacturing techniques, is an energy-intensive process. It is important to develop energy-efficient CNC machining strategies to achieve the overall goal of sustainable manufacturing. Due to the complexity of machining parameters, it is challenging to develop effective modelling and optimisation approaches to implement energy-efficient CNC machining. To address the challenge, in this paper, BS EN24T alloy (AISI 4340) has been used as a case study to conduct energy-efficient analysis and optimisation. Using a combination of experimentation and Taguchi analysis, the impact of the key machining parameters of CNC machining processes on energy consumption has been investigated in detail. A multi-objective optimisation model has been formulated, and a novel improved multi-swarm Fruit Fly optimisation algorithm (iMFOA) has been developed to identify optimal solutions. Case studies and algorithm benchmarking have been conducted to validate the effectiveness of the optimisation approach. The relationships between energy consumption and key machining parameters (e.g., cutting speed, feed per tooth, engagement depth) have been analysed to support process planners in implementing energy-saving measures efficiently. The optimisation approach developed is effective in fine-tuning key parameters for enhancing energy efficiency while meeting other technical requirements of production

Process simulation for 5-axis machining using generalized milling tool geometries

Multi-axis machining (especially 5-axis machining) is widely used in precision machining for automotive, aerospace and die-mold manufacturing. The goal in precision machining is to increase production while meeting high part quality needs which can be achieved through decision of appropriate process parameters considering machine tool constraints (such as power and torque), chatter-free operations and part quality. In order to predict and decide on optimal process parameters, simulation models are used. In the literature, individual tool geometries for multi-axis machining are examined in detailed with different modeling approaches to simulate cutting forces. In this study, a general numerical model for 5-axis machining is proposed covering all possible tool geometries. Tool envelope is extracted from CAD data, and helical flutes points are represented in cylindrical coordinates. Equal parallel slicing method is utilized to find cutter engagement boundaries (CEB) determining cutting region of the tool surface. for each axial level in the tool axis direction. For each level uncut chip thickness value is found and total forces are calculated by summing force values for each point along the cutting flutes. For arbitrary cases forces are simulated and obtained results are experimentally verified

Modeling and Optimal Design of Machining-Induced Residual Stresses in Aluminium Alloys Using a Fast Hierarchical Multiobjective Optimization Algorithm

The residual stresses induced during shaping and machining play an important role in determining the integrity and durability of metal components. An important issue of producing safety critical components is to find the machining parameters that create compressive surface stresses or minimise tensile surface stresses. In this paper, a systematic data-driven fuzzy modelling methodology is proposed, which allows constructing transparent fuzzy models considering both accuracy and interpretability attributes of fuzzy systems. The new method employs a hierarchical optimisation structure to improve the modelling efficiency, where two learning mechanisms cooperate together: NSGA-II is used to improve the model’s structure while the gradient descent method is used to optimise the numerical parameters. This hybrid approach is then successfully applied to the problem that concerns the prediction of machining induced residual stresses in aerospace aluminium alloys. Based on the developed reliable prediction models, NSGA-II is further applied to the multi-objective optimal design of aluminium alloys in a ‘reverse-engineering’ fashion. It is revealed that the optimal machining regimes to minimise the residual stress and the machining cost simultaneously can be successfully located

Performance evaluation of electrical discharge machine on titanium alloy using copper impregnated graphite electrode

Electrical discharge machining (EDM) which is very prominent amongst the non conventional machining methods is expected to be used quite extensively in machining titanium alloys due to the favorable features and advantages that it offers. This thesis presents the EDMing of titanium alloy (Ti-6246) using copper impregnanted graphite electrode with diameter of 8 mm. The main purpose of this study was to investigate the influenced of various parameters involved in EDM on the machining characteristics, namely, material removal rate (MRR), electrode wear ratio (EWR), surface roughness (Ra) and overcut. In this investigation, the machining trials were performed using a Sodick linear motor EDM sinker series AM3L The experimental plan for the processes were conducted according to the design of experimental (DOE) and the results were statistically evaluated using analysis of variance (ANOVA). Results showed that current was the most significant parameter that influenced the machining responses on EDM of Ti-6246. Confirmation tests were also conducted for the selected conditions for each machining characteristics in order to verify and compare the results from the theoretical prediction using Design Expert software and experimental confirmation tests. Overall, the results from the confirmation tests showed that the percentage of performance was acceptable due to all results obtained were within the allowable values which was less than 15% of marginal error