Actual Machining Process Research Articles

Optimization of Cutting Parameters Based on Multi-Objective Genetic Algorithm NSGA- II

This paper investigates optimization problem of the cutting parameters in milling on NAK80 mold steel with high hardness. In the study, by applying non-dominated sorting genetic algorithm-II, multiple sets of cutting parameters conformed to the requirements are acquired through solving the models, underlied by the design of orthogonal experiment with respect to cutting speed, feed rate and cutting depth, and the statistical model of cutting force and surface roughness by regression method, and the theoretical formula of material cutting rate. The proposed model and algorithm works well in the actual machining process as the experimental results show.

Numerical modelling of high-speed ball end milling with cutter inclination angle

This paper describes the development of a simulation model for ball end milling with inclination angle based on a finite element method. The Johnson–Cook model and isotropic hardening rule were used to describe the properties of the workpiece material, and re-meshing technology was adopted to obtain accurate results. The Cockcroft–Latham criteria rule was used to determine the chip formation. The ball end mill was modelled, and then imported into a finite element analysis system for simulation of machining process. The heat conducted into the cutter was taken into account in the present simulation, giving a better accordance with the actual machining process. Thirty combinations of cutting parameters and inclination angle of the ball end milling process were simulated in the finite element environment, and the corresponding ball end milling experiments were conducted in a five-axis machine. Evolution of the chip and the effective stress predicted in the shear zone during simulation were presented. The cutting forces derived from the simulation were compared with the experimental results, and the overall trend of the maximum cutting forces in each direction showed a good agreement with the experimentally measured values. The potential possibility to study five-axis ball end milling with both inclination angle in feed and cross-feed direction was pointed out.

Research about Numerical Control Machining of STL Files Based on Fagor CNC System

According to the situation that surface grid models are widely used, this article summarizes the research status of numerical control machining based on Triangle facets models, introduces the STL files in detail, expounds the process of machining STL files by using Pro/Toolmaker system, designs an independent post processor for generating NC code for Fagor machine, simulates the virtual machining process through Vericut software, verifies the actual machining process on Fagor three axis CNC milling machine. Proves the method of numerical control machining based on STL files is actually feasible for planar milling、cavity milling、profile milling, Realizes the machining of STL files based on Fagor CNC system.

Microstructure of electrochemical micromachining using inert metal mask

Electrochemical micromachining (EMM) has been gaining popularity as an alternative method to fabricate microstructure. A method of EMM is proposed to produce microhole array or micro-dimple array, in which a patterned inert metal mask (platinum plate) is closely attached to workpiece (anode), not bonded to the anode. When voltage is applied across the anode and the cathode over which electrolyte flows at a high speed, the patterns in the mask are transferred to the anode, and microstructures are produced. A mathematical model to describe the actual machining process is established. By considering the effect of nonlinear electrolyte, the parametric finite element method is adopted to simulate and numerically analyze the erosion process. Some experiments are performed to verify the proposed model.

Virtual Machining Process System for Marine Diesel Engine Key Parts

The virtual machining process system is built based on VERICUT platform to simulate the whole procedure of machining marine diesel engine key parts. It changes the traditional method of test-cutting, shortens development time and ensures the safety of the actual machining process system. Examples of machining marine diesel engine frame and cylinder cover are done to verify the effectiveness of this system. It is demonstrated that it has a wide application future and spreading value in the production of marine diesel engine key parts and the whole manufacturing industry.

Research on Machining Simulation of Ultra High-Speed Grinding Machine Tool Based on Web

The future development of the manufacturing is using VR technology to make the machining simulation before the actual machining process made. The machining simulation of Ultra High-speed Grinding Machine Tool is researched in this paper. Firstly, using UG/NX software and VRML, the geometric modeling of machine tool is modeled. Secondly, through using Java and Javascript language, the operation and display of machining process of ultra high-speed grinding are realized. The main technologies include NC codes compiling, collision detection and material removal. Thirdly, the example of machining simulation using virtual ultra high-speed grinding machine tool can be obtained in the paper. Compared to other CNC machining simulation methods, the method in the paper has reality display, rich features, a good man-machine interaction, etc., and it does not rely on expensive CAD/CAM software. The system files generated by the machining simulation have the small size and can be transferred on the network easily.

Studies on Passive Cooling Techniques in Dry Machining

The article presents the numerical model and computational evaluation of cutting tool insert for passive cooling technique, which reduces the temperature of the insert during dry machining. The technique developed uses heat sink materials for extracting the thermal load of the cutting tool insert indirectly. The developed technique is not affecting the actual machining process. The computational model developed is validated with the experimental data. Also, by using validated computational models, temperatures at the tip of the cutting tool inserts are predicted. The scanning electron microscope photographs reveal that the bonding of work material to the rake surface is considerably reduced for the passive cooling technique.

Prediction of machining chatter based on FEM simulation of chip formation under dynamic conditions

Machining chatter is an inherently nonlinear phenomenon that is affected by many parameters such as cutting conditions, tool geometry e.g., nose radius and clearance angle and frictional conditions at the tool/workpiece interface. Models for chatter prediction often ignore nonlinearities or introduce them through simple models for friction and geometry. In particular, the effect of chip–tool interaction on the occurrence of chatter is not investigated thoroughly. This paper presents a novel approach for prediction of chatter vibration and for investigation of the effects of various conditions on the onset of chatter. This approach uses finite element simulation to investigate the inter-relationship between the chatter vibration and the chip formation process. Simulation of chip formation is combined with dynamic analysis of machine tool to determine the interaction between the two phenomena. Mesh adaptation technique is used to move the tool inside the workpiece to form the chip, while a flexible tool is used to allow the tool to vibrate under variable loading conditions. By repeating the simulations under various widths of cut, it is shown that the onset of chatter can be detected, and the simulation is able to realistically predict various phenomena observed in actual machining process such as variation of shear angle and the increase of stability at lower speeds known as process damping. The stability map obtained from simulations is compared with experimental data attained through orthogonal cutting tests. Reasonable agreement observed between the two sets of results demonstrates the effectiveness of the simulation approach.

Modeling Research of Hypoid Gear Based on Real Machining Process

In this paper, two modeling methods, the forming method and the generating method, for hypoid gears with two kinds of transmission ratio are discussed by simulating the actual machining process. In the generating modeling method, the tooth profile of the gear is generated by boolean algorithm step by step after creating the models of the gear blank and the cutter and then rotating around their own axis by certain degrees until the cutter is outside the gear blank completely. In contrast with the generating modeling method, the tooth profile is formed by carrying out the boolean algorithm for one time after creating the models of the gear blank and cutter seperately in the forming modeling method. Then using feature instance, all the teeth are created both in the generating modeling method and in the forming modeling method. Using the two modeling methods given in this paper, the modeling process can be shortened and the modeling precision can be improved.

Surface roughness model for micro electrical discharge machining

Asperities produced by electrical discharge machining (EDM) are covered by a multitude of overlapping craters, which results in the formation of corresponding workpiece profiles with a specified accuracy and surface finish. This paper proposes a surface roughness model for micro-EDM based on the crater geometry estimation. Surface factors are introduced into the model formulation to take into account the effects of overlapping craters, pockmarks, microcracks, and reattachment of debris in the actual machining process. Based on the experimental results using AISI 4140 as the workpiece, the surface factors are found to be 0.2985 and 0.3443 for the theoretical surface roughness for Ra and Rt respectively. Extension of the surface roughness prediction model to other materials is demonstrated using Ti—6Al—4V. Through this preliminary study, the proposed model generated theoretical results that have an average error of 6.5 per cent for Ra and 4.5 per cent for Rt when compared with the respective experimental results, thereby revealing the potential usefulness of the surface roughness prediction model.

An Adaptive Fuzzy Controller for Constant Cutting Force in End-Milling Processes

A novel multilevel fuzzy control system is introduced and implemented for online force control of end-milling processes to increase machining productivity and improve workpiece quality, where the cutting force is maintained at its maximum allowable level in the presence of different variations inherent in milling processes, such as tool wear, workpiece geometry, and material properties. In the controller design, the fuzzy rules are generated heuristically without any mathematical model of the milling processes. An adaptation mechanism is embedded to tune the control parameters online, and the resultant closed-loop system is guaranteed to be stable based on the input-output passivity analysis. In the experiment, the control algorithm is implemented using a National Instrument real-time control computer in an open architecture control environment, where high metal removal rates are achieved and the cycle time is reduced by up to 34% over the case without any force controller and by 22% compared with the regular fuzzy logic controller, thereby indicating its effectiveness in improving productivity for actual machining processes.

An on-line monitoring system for a micro electrical discharge machining (micro-EDM) process

A pulse-type discriminating system to monitor the process of micro electrical discharge machining (micro-EDM) is developed and implemented. The specific features are extracted and the pulses from a RC-type power source are classified into normal, effective arc, transient short circuit and complex types. An approach to discriminate the pulse type according to three durations measured at three pre-determined voltage levels of a pulse is proposed. The developed system is verified by using simulated signals. Discrimination of the pulse trains in actual machining processes shows that the pulses are mainly the normal type for micro wire-EDM and micro-EDM milling. The pulse-type distribution varies during the micro-EDM drilling process. The percentage of complex-type pulse increases monotonically with the drilling depth. It starts to drop when the gap condition is seriously deteriorated. Accordingly, an on-line monitoring strategy for the micro-EDM drilling process is proposed.

Analytical modeling of chatter stability using multi‐dimensional approach

AbstractMachining is one of the most common manufacturing processes in industry due to its high flexibility and ability to produce parts which excellent quality. Chatter, a type of self excited vibrations arising in metal cutting operations, is a major limitation in machining resulting in poor quality and reduced productivity. Under certain conditions, the cutting process may become unstable yielding oscillations with high amplitudes and cutting forces. Stability analysis of the dynamic cutting process can be used to determine chatter‐free machining conditions with high material removal rate. Usually, one dimensional models are used for stability analysis of machining. However, based on the geometry of the actual machining process, multi‐directions would have to be used for accurate modeling of the process dynamics and the stability. In this presentation, multi directional models for turning and milling processes are presented. The effects of multi directional process mechanics on the stability are demonstrated by applications. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Off-line optimization on NC machining based on virtual machining

Virtual machining, based-on the model of a machining system, aims to simulate, evaluate and optimize the actual machining process with high sense of reality. It provides digital off-line optimization tools for NC machining. Taking advantage of virtual machining used in machining process simulation, one can build the framework of optimization system on NC machining so that the processes of reliability verification, cutting parameter optimization and error compensation can be integrated into one system to improve machining processes comprehensively. The optimization is realized via modifying NC programs. Several key issues such as virtual machining, cutting parameters optimization, error prediction and compensation are also highlighted. Optimization systems based on virtual machining have been developed to demonstrate the effectiveness of off-line optimization for different purposes. The results show that the machining process is obviously improved.

Computer simulation and experimental study of machining deflection due to original residual stress of aerospace thin-walled parts

Aerospace thin-walled parts have a complex structure and high accuracy. Factors such as original residual stress, fixing, and machining may make low-rigidity parts deform easily, which is difficult for traditional craftwork to forecast and control. Especially in machining big aerospace parts, original residual stress has a great effect on machining deflection. In this paper finite element model of original residual stress is established to analyze the corresponding deflection by machining aerospace thin-walled parts. Simulation results are validated consistent with experimental results approximately. At last the paper puts forward the corresponding mend methods to control the deflection caused by original residual stress during the actual machining process.

The neighborhood method and its coupling with the wavelet method for signal separation of chaotic signals

Signal separation, i.e., the elimination or suppression of extraneous components from measured signals, is an essential module of modern signal analysis. We report the development of two novel signal separation methods—(i) the neighborhood method (NM) and (ii) a modified wavelet method (MWM)—that seem to be aptly suited for signals acquired from machining process sensors, i.e., for chaotic signals with small, uniform Lyapunov exponents. For the NM, a variant of shadowing signal separation methods used for signal separation of chaotic signals, we establish theoretical bounds on performance under various noisy conditions and analyze its algorithmic complexity. Our MWM is an adaptation of Donoho's wavelet method to nonlinear, and possibly chaotic, signals with multiplicative noise. It incorporates certain features of the NM and it has lower algorithmic complexity than the NM, and is, therefore, more suitable for on-line implementation. Both methods were tested on chaotic signals corresponding to the reconstructed Rossler attractor. A discussion on the application of both methods to signals obtained from actual machining process sensors is provided in order to motivate their suitability to real-world nonlinear processes.

In-process monitoring of end milling cutter runout

An on-line methodology for the monitoring of end milling cutter runout is presented. Runout has been a limiting factor for achievable productivity in machining due to its adverse effect on tool fife and part quality. However, calibration and adjustment of cutter runout have been- difficult in that runout characteristics react dynamically to the actual machining process. The approach discussed utilizes the time-dependent spectral analysis of cutting force to estimate the cutter runout characteristics of magnitude and angular orientation. The presence of cutter runout generates a cutting force component at the spindle rotational frequency. Given a priori knowledge of the part's material properties, tool geometry, cutting parameters, and machining configuration, the instantaneous runout characteristics are recursively updated from their previous values and the recent measurement of cutting force. The recursive nature of this approach facilitates the in-process implementation of runout monitoring and provides opportunities for control and optimization. The analytical basis of the method is introduced, system mechatronics elaborated, implementation procedure presented, and resulting machining data examined.

Expert system-supported fuzzy diagnosis of finish-turning process states

Developing an effective method for on-line machining condition monitoring has been of great interest with the advent of automated machining systems. By effective it is meant that reliable and timely diagnosis of machining process states, such as tool breakage, severe wear and chip hazard, should be provided under various work conditions in a practical workshop environment. This is difficult as the machining process, especially finish-turning process, is complex, random and uncertain in nature, and influenced by numerous process parameters. In an attempt to tackle the problem, a new approach based on fuzzy state diagnosis is presented in this paper by introducing a series of fuzzy feature-state relationship matrices to quantify the strength between each key signal feature identified from cutting force-tool vibration data and various actual machining process states. The knowledge-intensive fuzzy feature-state relationship matrices are off-line developed with the support of a knowledge-based expert system that is constructed by a well-established machining reference database, expert intelligence on logic reasoning and decision-making, and experimental results of signal characteristics under various work conditions. These matrices, once established, can be on-line implemented to generate an integrated fuzzy feature-state matrix (ten features and nine states in this work) which is the essence for a fast and reliable diagnosis of machining process states. Finally, a detailed case study is worked out to demonstrate the work principle of the methodology presented in this paper.

予圧切換スピンドルの性能評価

The following deals with the static and dynamic specification of the motor integrated spindle. This spindle unit has a fixed position and constant pressure preload switching mechanism operated using hydraulic pressure. With respect to the static specification, measurement of the static rigidity and natural frequency confirms that preload switching occurs. The performance of the rotating spindle was evaluated using a fixed position preload for low speeds provided high rigidity, while using a constant pressure preload provided sufficient high speed performance. A bench test was carried out to evaluate temperature and runout characteristics and further tests were performed in an actual machining process. Both tests showed that the switching of the spindle's preload provided sufficient performance.

The Study on Human-Oriented Manufacturing System. 2nd Report, The Study on Human-Oriented NC Machine Tools.

This paper deals with the fundamental research for the development of human-oriented NC machine tools with which workers can feel pride and pleasure making full use of their ability in manufacturing. As a first step toward human-oriented NC machine tools, Machining Phenomenon Visualizing System (MPVS) which allows workers to see and check actual machining process as stationary state has been developed and installed on a NC lathe. Through many practices, it has been proved that the vision by MPVS provides much usefull information on machining for workers. Meanwhile, the study in the first report has proved that the factors contributing to worker's satisfaction in manufacuring originate from the following seven satisfaction factors-technical skill, interest, social contribution, creativity, subjectivity, feedback effect and diversity. In this paper, according to these seven satisfaction factors, MPVS has been evaluated by inexperienced workers, lathe skilled workers and NC lathe skilled workers using Information Integration Method. The results show that MPVS greatly improves worker's satisfaction and has immediate strong effect on feedback effect and creativity for all types of workers.