Maximum Machining Efficiency Research Articles

Tool inclination angle designing for low-deformation and high-efficiency machining of thin-wall blade based on edge-workpiece-engagement

The maximum flexibility direction(MFD) is solved for establishing the deformation estimation criterion of the blade during machining process, and the larger the milling force in MFD, the bigger the deformation of the blade during machining process. A new milling force calculation algorithm based on edge-workpiece-engagement(EWE) is proposed by analyzing the contact process between the ball-end milling tool and the chip. The chip thickness of each tool element of each edge curve at any rotation angle is calculated, the milling force of MFD and SLDs under different inclination angles are calculated. The average absolute milling force in MFD reaches the minimum value of 0.65126N when the lead/tilt angle is 30°/-45°, and the maximum machining efficiency is reached when the lead/tilt angle is 45°/-45°.The optimized tool inclination angle, which is 30°/-45° for lead/tilt angle, is obtained by solving the multi-objective optimization problem of machining deformation represented by relative deformation and machining efficiency represented by relative stable machining area. The effectiveness of the proposed scheme is verified by comparison of simulation and experiment for blade machining error under two kinds of tool orientations.

Multi-objective optimization of machining parameters in complete peripheral milling process with variable curvature workpieces

The mechanism of peripheral milling with variable curvature has yet to be revealed. There is an urgent need to develop a composite optimization approach for the full milling process, including rough and fine machining. The influence of curvature on the energy consumption mechanism in peripheral milling is investigated in this paper. Firstly, the geometric parameters of peripheral milling are analyzed, and the material removal rate calculation method with variable curvature is proposed. The effects of workpiece curvature, machining parameters, and tool wear on energy consumption and surface quality are revealed. Secondly, prediction models for machine tool specific energy and surface roughness are developed in accordance with the examined material removal mechanism. Then, the carbon emission calculation method for the complete peripheral milling process is put forward based on the developed energy consumption mechanism. Finally, a genetic algorithm with elite strategy is used to optimize the multi-dimensional and multi-objective machining parameters. The objective is to achieve the maximum machining efficiency, minimize carbon emissions, and attain excellent surface quality during the complete milling process. The research aims to concurrently optimize machining parameters for rough and fine machining processes, thereby enabling effective and environmentally friendly peripheral milling while maintaining machining quality. The determination coefficient R2 for the proposed model exceeds 0.97, while the average accuracy of predictions surpasses 96 %. The research holds particular importance in providing guidance for peripheral milling operations involving workpieces with variable curvature.

Investigation of the Titanium Alloy Turning Process with Prime A Tools under High-Pressure Cooling Conditions

When turning titanium alloys, it is difficult to ensure the required quality with maximum machining efficiency. A typical problem in the turning process of titanium alloys is to achieve effective breaking and removal of chips from the machining zone. The combination of the new construction of cutting tools and machining methods in the machining of titanium alloys increases the efficiency of the machining. For this reason, the use of tools typical for the Prime Turning method in combination with the high-pressure cooling (HPC) method was analysed. The longitudinal turning of the Ti6Al4V ELI titanium alloy was performed using Sandvik Coromant grade 1115 carbide tools. An increase in the pressure of the cutting fluid to p = 70 bar was used. Measurements of the components of the total cutting force for finishing machining with variable cutting parameters in the range of: feed rates f = <0.1;0.4> mm/rev, cutting depth ap = <0.25;1.0> mm and cutting speed vc = <40;80> m/min were performed. It has been shown that the values of cutting force are mainly dependent on the feed and the depth of cut. An analysis of the forms of chips obtained is presented. The dependence of the applied cutting parameters on the value of the chip breakage coefficient Cch was determined. The method of searching for the maximum efficiency of the turning process was determined, taking into account the desired value of the chip breakage coefficient.

Plunge milling with constant scallop height by adaptively modifying the step interval for pocket wall

Plunge milling plays an important role in machining of components with cavity structures. As a non-continuous material removal strategy, residual material is inevitably remained between two adjacent plunge cutter locations, also named as scallop. Large scallop height causes machining error, as well as fluctuations of cutting width in the following machining operation like semi-finish milling. As such, a constant scallop from plunge milling is essential to improve machining stability and tool life in following operation. In this paper, a new plunge milling toolpath generation method with adaptive interval is developed to restrict the maximum scallop height within a given value. Geometric relationship between plunge tool location and cusp of the constant scallop is firstly analyzed to determine the curves that the cusp of the constant scallop and plunge tool location located on. Then an iterative cusp of the constant scallop calculation algorithm is constructed based on the constructed geometric relationship. The next plunge tool location is obtained through a similar algorithm. Therefore, interval between current and its previous tool location is determined. In this way, the generated plunge milling toolpath can satisfy the given machining error allowance and keep a constant scallop height. It also has minimum number of plunge cutter locations to achieve maximum machining efficiency. Advantages of the proposed method are validated through a machining experiment by comparing the machining results with conventional plunge milling toolpath with constant step interval.

Ductile-regime machining model for ultrasonic elliptical vibration cutting of brittle materials

Ultrasonic elliptical vibration cutting (UEVC) is attracting much attention in ultra-precision machining of brittle materials as it was found be able to effectively increase the critical depth of cut (dc) of brittle materials. However, the mechanisms for the increased dc are still not fully understood. In this study, a ductile-regime machining model was developed for the UEVC of brittle materials to achieve maximum dc and thus the maximum machining efficiency. It shows that the reasons for the increase of dc are: (1) The actual undeformed chip thickness (UCT) is smaller than the nominal depth of cut (DOC); (2) The distance from transient surface to target surface (DTSTS) can endure the crack propagation within a certain range when UCT exceeds the critical UCT (tc). Based on the ductile-regime machining model, a predictive model was developed for the determination of dc in microgroove plunge-cutting with respect to several determining factors, including DTSTS, UCT, tc and length of the crack (Cm). A series of experiments on plunge-cutting of KDP crystal were conducted. Results showed that the predicted dc match well with the experimental ones. In addition, it was found that dc increases as the amplitude of vibration along the cutting direction increases or the cutting speed decreases, and dc increases first and then decreases as the amplitude of vibration along the thrust direction increases.

Optimization of cutting parameters with a sustainable consideration of electrical energy and embodied energy of materials

In a milling process, proper selection of cutting parameters can significantly reduce the electrical energy consumption. Many researchers have conducted cutting parameter optimization of the milling process for electrical energy saving during the past several years. However, in the milling process, a large amount of auxiliary materials such as cutting tools and cutting fluids are consumed. The production process of these materials is energy-intensive and a lot of energy are consumed. Optimizing cutting parameters considering both the electrical energy consumption and embodied energy consumption of auxiliary materials can further reduce the environmental impact of the milling process. In this paper, an approach of cutting parameter optimization is proposed to maximize energy efficiency and machining efficiency for milling operation. Firstly, an energy consumption model of milling operation considering both the electrical energy consumption and embodied energy consumption of cutting tools and cutting fluids is proposed. Then a multi-objective optimization model is established to achieve maximizing energy efficiency and machining efficiency. Finally, to verify the proposed multi-objective model, case studies are carried out and the results indicate that (i) the optimum cutting parameters of milling process vary with the energy boundaries whether considering the embodied energy of the auxiliary materials or not; (ii) the optimum cutting parameter schemes for maximum machining efficiency do not ensure maximum energy efficiency; (iii) multi-objective optimization is an effective method to address the conflicts of the two objectives.

Multi-objective optimization of tool path considering efficiency, energy-saving and carbon-emission for free-form surface milling

An urgent challenge in the manufacturing industry is increasing efficiency while decreasing energy consumption and environmental impact. Past studies addressing these issues have mainly focused on tool path optimization only considering machining efficiency. In this paper, we present a methodology to optimize the tool path for high efficiency, low energy consumption and carbon footprint in milling process. Firstly, the description and influencing factors of tool path are introduced. Then, a multi objective tool path optimization model with maximum machining efficiency, minimum energy consumption and carbon emission is proposed. Furthermore, the solution of the proposed model is introduced, which including two steps, one is the calculation of the number of cutter contact points (CCP), the other is using adaptive dynamic GA to optimize the connection sequence and ways of each CCP. Finally, the effectiveness and practicability of the method are verified by the machining experiments.

Effects of temperature on the removal efficiency of KDP crystal during the process of magnetorheological water-dissolution polishing.

As a kind of important nonlinear optical element, KDP crystal has great demand in the inertial confinement fusion system. Based on the dissolution mechanism of solid materials, the factors that affect the material removal rate of KDP crystal in magnetorheological (MR) water-dissolution polishing are investigated to improve the machining efficiency. It is found that the material removal rate is proportional to the product of the saturation concentration and diffusion coefficient, and the relationship between the removal efficiency and the temperature meets the unilateral Gaussian function. Polishing experiments are carried out on a magnetorheological finishing (MRF) machine with self-designed MRF fluid heating devices. The experimental results show that practical efficiency-temperature curve is consistent with the theoretical curve, and the maximum machining efficiency increases by about 50% with the rise of temperature from 294 to 302 K. Meanwhile, when the MR fluid temperature is lower than 308 K, the crystal surface quality and surface roughness in different processing temperatures have no remarkable difference with constant crystal temperature (294 K). This research indicates that it is feasible to drastically improve KDP crystal MRF efficiency by controlling the processing temperature.

Study on high-speed cutting parameters optimization of AlMn1Cu based on neural network and genetic algorithm

In this article, the cutting parameters optimization method for aluminum alloy AlMn1Cu in high-speed milling was studied in order to properly select the high-speed cutting parameters. First, a back propagation neural network model for predicting surface roughness of AlMn1Cu was proposed. The prediction model can improve the prediction accuracy and well work out the higher-order nonlinear relationship between surface roughness and cutting parameters. Second, considering the constraints of technical requirements on surface roughness, a mathematical model for optimizing cutting parameters based on the Bayesian neural network prediction model of surface roughness was established so as to obtain the maximum machining efficiency. The genetic algorithm adopting the homogeneous design to initialize population as well as steady-state reproduction without duplicates was also presented. The application indicates that the algorithm can effectively avoid precocity, strengthen global optimization, and increase the calculation efficiency. Finally, a case was presented on the application of the proposed cutting parameters optimization algorithm to optimize the cutting parameters.

Modeling and Analysis of Homopolar Motors and Generators

The dc homopolar motor converts electrical energy into mechanical rotational energy using the Lorentz force. The same machine can be operated in reverse to convert mechanical energy into dc electrical energy. To better understand homopolar motors and their suitability for use in various applications, a computer model was created using PSpice. Forces opposing the motor rotation include back voltage, eddy currents, moment of inertia, and sliding contact friction and are analyzed in detail. Forces and torques are discussed and calculated analytically. The capabilities of the homopolar machine operating as both a motor and a generator are considered. Using current research from the University of Missouri on helical guns and railguns, which utilize similar electromagnetic forces for linear acceleration, the maximum efficiency of the homopolar motor during transient start-up phase is examined. The measured homopolar motor efficiency in this paper asymptotically approaches 50% and is determined by several variables. Experimental data are collected and used to compare the simulation results and verify the accuracy of motor performance. Sensitivity analysis and the estimated maximum machine efficiency obtained from simulation are presented.

Operating Strategies of Switched Reluctance Machines for Exhaust Gas Energy Recovery Systems

This paper presents an operating strategy for high-speed switched reluctance (SR) generators employed in exhaust gas energy recovery systems. The machine is operated in “single pulse” mode, and a parametric study of the control angles is performed to analyze the machine operation. It is shown that, for given speed and power, optimum sets of control angles exist, which achieve maximum machine efficiency and minimum thermal stress. This study is undertaken using a coupled nonlinear modeling approach, combining magnetostatic finite-element analysis with time-domain circuit simulation. The results are compared with measurements performed on an SR generator designed for a prototype exhaust gas energy recovery system, showing overall good agreement.

High-Speed Milling of Tool Steel Dies for Aluminium Extrusion: Surface Roughness, Dimensional Tolerance and Chip Removal Mechanisms

Die finishing has a fundamental importance to ensure a good quality of aluminium extruded parts and involves important economic effects due to the vastness of metalworking industry and the relatively short tool life in this field. Maximum machining efficiency is thus crucial. The research addresses optimization of finishing performances on tool steel extrusion dies. Milling tests are carried out on semimanufactured parts to ensure adherence to standard industrial technological chain, varying cutting parameters towards the field of high-speed machining (HSM). Dimensional tolerance is determined on die lands. Land surface roughness is measured through a multiscale approach and modelled as a function of cutting speed and feed. The above methodology enables a correlation between macroscopic process outcomes and chip removal mechanisms in the microscale.

Integrated tool path and feed rate optimization for the finishing machining of 3D plane surfaces

An integrated approach for the concurrent optimization of tool path and feed rate for the finishing machining of 3D plane surfaces using ball-end milling is presented in this paper. This work is important, as the developed optimization approach is readily applicable to the finishing machining of sculptured surfaces. The concurrently optimized tool path and feed rate correspond to the maximum machining efficiency and satisfy the scallop height and machining error requirements. The cutter feed direction is employed as the optimization variable. For each cutter feed direction, tool path is determined according to the scallop height requirement and feed rate is maximized with the tolerance requirement by using a mechanistic cutting force model for three-dimensional ball-end milling. Optimization results have indicated that the shortest total tool path length, favored by most existing optimization approaches, does not result in maximum efficiency because the corresponding feed rate is often constrained by the specified tolerance. The optimum cutter feed direction is in general not unique but falls within an optimum range in the finishing machining of 3D plane surfaces.

Experimental nonlinear torque control of a permanent-magnet synchronous motor using saliency

In this paper, a new nonlinear control strategy is proposed for a permanent-magnet salient-pole synchronous motor. This control strategy simultaneously achieves accurate torque control and copper losses minimization without recurring to an internal current loop nor to any feedforward compensation. It takes advantage of the rotor saliency by allowing the current (i/sub d/) to have nonzero values. This, in turn, allows us to increase the power factor of the machine and to raise the maximum admissible torque. We apply input-output linearization techniques where the inputs are the stator voltages and the outputs are the torque and a judiciously chosen new output. This new output insures a well-defined relative degree and is linked to the copper losses in such a way that, when forced to zero, it leads to maximum machine efficiency. The performance of our nonlinear controller is demonstrated by a real-time implementation using a digital signal processor (DSP) chip on a permanent-magnet salient-pole synchronous motor with sinusoidal flux distribution. The results are compared to the ones obtained with a scheme which forces the i/sub d/ current to zero.

Microcomputer-Controlled Electric Discharge Machine

Principle of operation of EDM is briefly outlined. It is shown that the automatic nature of this unconventional machine lends itself easily to computer control. The parameters to be computer-controlled for maximum machining efficiency are discussed with particular reference to the interface required. Current status in the field of computer-controlled EDM is reviewed. Work going (Hi in NAL in this area is presented with particular emphasis on the hardware realization of microcomputer-controlled EDM.