不锈钢材料数控加工参数优化研究

运用数学方法对不锈钢数控加工参数进行优化,提出了新的最低成本目标函数,使用MATLAB/Optimization Toolbox编制优化程序,优化结果能缩短加工时间35.54%,降低加工成本10.97%.基于对优化结果的分析,发现机床转速和表面加工精度是限制不锈钢加工的主要约束,提出了"高转速低进给量"的加工策略.     

Experiment and simulation study on concentrated magnetic field-assisted ECM S-03 special stainless steel complex cavity

A novel concentrated magnetic field-assisted electrochemical machining (ECM) technology is proposed in this paper to machine contemporaneously seven workplaces’ complex cavity with high efficiency and good precision. An ECM clamping apparatus with concentrated magnetic field, periodic magnetic field, and no magnetic field was designed. The magnetic field simulation was carried out. Comparing the results of the concentrated magnetic field to the periodic magnetic field, the magnetic field intensity of the former is increased by 9.8 % than the latter. The ECM cathode with the same gap was designed and manufactured. Under the conditions of 12 % NaNO₃, 14-V voltage, 0.8-MPa electrolyte pressure, temperature 32 °C, cathode feed rate 0.9 mm/min, initial machining gap 0.1 mm, and the S-03 special stainless steel workpiece material, the experiments with concentrated magnetic field, periodic magnetic field, and no magnetic field were carried out. The results show that the gap magnetic field strength was increased by 16.7 % in the concentrated magnetic field than in the periodic magnetic field. Through a sectioning test, the precision in the concentrated magnetic field is increased by 33.3 % compared with no magnetic circuit and increased by 14.8 % compared with the periodic magnetic field. The concentrated magnetic field-assisted ECM technology cannot only reduce the cathode design cycle and cost but also increase the process accuracy.     

Experimental study on micro electrical discharge machining of porous stainless steel

Various cutter strategies have been developed during milling freeform surface. Proper selection of the cutter path orientation is extremely important in ensuring high productivity rate, meeting the better quality level, and longer tool life. In this work, finish milling of TC17 alloy has been done using carbide ball nose end mill on an incline workpiece angle of 30°. The influence of cutter path orientation was examined, and the cutting forces, tool life, tool wear, and surface integrity were evaluated. The results indicate that horizontal downward orientation produced the highest cutting forces. Vertical downward orientation provided the best tool life with cut lengths 90–380 % longer than for all other orientations. Flank wear and adhesion wear were the primary wear form and wear mechanisms, respectively. The best surface finish was achieved using an upward orientation, in particular, the vertical upward orientation. Compressive residual stresses were detected on all the machined surfaces, and vertical upward orientation provided the minimum surface compressive residual stress. In the aspect of tool wear reduction and improvement of surface integrity, horizontal upward cutter path orientation was a suitable choice, which provided a tool life of 270 m, surface roughness (R _a ) of 1.46 μm, and surface compressive residual stress of ?300 MPa.     

不锈钢薄壁件精密加工工艺分析

通过对不锈钢筒形薄壁件结构工艺性和影响加工变形的因素及其原理进行分析,提出了减小加工变形的技术途径,实践证明合理的装夹方式、工艺参数等措施较好地解决了此类零件的精密加工工艺问题。     

An optimization method of the machining parameters in high-speed machining of stainless steel using coated carbide tool for best surface finish

High-speed machining (HSM) has emerged as a key technology in rapid tooling and manufacturing applications. Compared with traditional machining, the cutting speed, feed rate has been great progress, and the cutting mechanism is not the same. HSM with coated carbide cutting tools used in high-speed, high temperature situations and cutting more efficient and provided a lower surface roughness. However, the demand for high quality focuses extensive attention to the analysis and prediction of surface roughness and cutting force as the level of surface roughness and the cutting force partially determine the quality of the cutting process. This paper presents an optimization method of the machining parameters in high-speed machining of stainless steel using coated carbide tool to achieve minimum cutting forces and better surface roughness. Taguchi optimization method is the most effective method to optimize the machining parameters, in which a response variable can be identified. The standard orthogonal array of L₉ (3⁴) was employed in this research work and the results were analyzed for the optimization process using signal to noise (S/N) ratio response analysis and Pareto analysis of variance (ANOVA) to identify the most significant parameters affecting the cutting forces and surface roughness. For such application, several machining parameters are considered to be significantly affecting cutting forces and surface roughness. These parameters include the lubrication modes, feed rate, cutting speed, and depth of cut. Finally, conformation tests were carried out to investigate the improvement of the optimization. The result showed a reduction of 25.5% in the cutting forces and 41.3% improvement on the surface roughness performance.     

Electrical discharge machining with ultralow discharge energy

The possibility of electrical discharge machining (EDM) with ultralow discharge energy has been investigated. EDM using an RC discharge circuit was performed at low open-circuit voltages and a capacitance of approximately 30 pF. Workpieces were ultrasonically vibrated to remove debris and bubbles from the discharge gap, thus preventing short-circuiting. The machining proceeded at voltages lower than 15 V at a vibration amplitude of 0.4 μm. The maximum discharge energy per pulse is as small as approximately 3 nJ under these conditions. The volumetric electrode wear ratio can be 0.2% at voltages lower than 40 V, while it is normally more than 1% for EDM using an RC discharge circuit. Workpiece surfaces processed at voltages of 20 V or lower are smooth and free of observable discharge craters, and show no typical features of surfaces machined by EDM.     

基于灰色关联分析的电火花加工不锈钢小孔工艺参数优化

采用DS307A高速穿孔机,开展在6mm厚不锈钢板上加工直径为1.2 mm小孔的试验研究。运用正交试验法,研究电火花加工电参数对加工时间、电极损耗和加工间隙的影响,并对试验结果进行灰色关联分析,得出最优加工参数。结果表明,经参数优化后,减少了加工时间、降低了电极损耗,以及表面粗糙度得以明显改善,满足快速精加工的技术要求。     

Electrical discharge machining in distilled water

The performances of kerosene and distilled water as the dielectric fluid in electrical discharge machining (EDM) were compared over the pulse energy range 0.72 – 288 mJ. Machining in distilled water resulted in a higher metal removal rate and a lower wear ratio than in kerosene when a high pulse energy range (72 – 288 mJ) was used. With distilled water, the machining accuracy was poor but the surface finish was better. Electron microprobe analysis revealed that the deposition of tool material (copper) on the work surface (high carbon steel) was low when machining took place in distilled water at a high pulse energy (288 mJ) and in kerosene at a low pulse energy (72 mJ). It is concluded that distilled water may be used as a dielectric fluid in EDM at a high pulse energy range.     

Multi-objective parametric optimization on machining with wire electric discharge machining

The selection of optimum machining conditions, during wire electric discharge machining process, is of great concern in manufacturing industries these days. The increasing quality demands, at higher productivity levels, require the wire electric discharge machining process to be executed more efficiently. Specifically, the material removal rate needs to be maximized while controlling the surface quality. Despite extensive research on wire electric discharge machining process, determining the desirable operating conditions in industrial setting still relies on the skill of the operators and trial-and-error methods. In the present work, an attempt has been made to optimize the machining conditions for maximum material removal rate and maximum surface finish based on multi-objective genetic algorithm. Experiments, based on Taguchi’s parameter design, were carried out to study the effect of various parameters, viz. pulse peak current, pulse-on time, pulse-off time, wire feed, wire tension and flushing pressure, on the material removal rate and surface finish. It has been observed that a combination of factors for optimization of each performance measure is different. So, mathematical models were developed between machining parameters and responses like metal removal rate and surface finish by using nonlinear regression analysis. These mathematical models were then optimized by using multi-objective optimisation technique based on Non-dominated Sorting Genetic Algorithm-II to obtain a Pareto-optimal solution set.     

A feasibility approach by simulated annealing on optimization of micro-wire electric discharge machining parameters

Due to the presence of large number of process variables and complicated stochastic nature, selection of optimum machining parameter combinations for obtaining higher material removal rate with minimum overcut and surface roughness is a challenging task in Micro Wire Electric Discharge Machining (μ-WEDM). The important parameters of Material Removal Rate (MRR), overcut and surface roughness are considered in this study of single pass μ-WEDM machining of aluminium. The system model is created with statistical based regression analysis using experimental data. This system model is employed to maximize the material removal rate and minimize the surface roughness and overcut using Simulated Annealing (SA) scheme. Finally consistency of the method is tested with trial values. The model is found as capable of predicting the response characteristics as a function of different control variables. Experiments are carried out to check the validity of the developed model and then optimal parametric combinations are searched out using an advanced optimization strategy.     

An experimental investigation on machining parameters of AISI D2 steel using WEDM

The performance of the wire electrodischarge machining (WEDM) machining process largely depends upon the selection of the appropriate machining variables. Optimization is one of the techniques used in manufacturing sectors to arrive for the best manufacturing conditions, which are essential for industries toward manufacturing of quality products at lowest cost. As there are many process variables involved in the WEDM machining process, it is difficult to choose a proper combination of these process variables in order to maximize material removal rate and to minimize tool wear and surface roughness. The objective of the this work is to investigate the effects of process variables like pulse on time, pulse off time, peak current, servo voltage, and wire feed on material removal rate (MRR), surface roughness (SR), gap voltage, gap current, and cutting rate in the WEDM machining process. The experiment has been done using Taguchi’s orthogonal array L27 (3⁵). Each experiment was conducted under different conditions of input parameters and statistically evaluated the experimental data by analysis of variance (ANOVA) using MINITAB and Design Expert tools. The present work also aims to develop mathematical models for correlating the inter-relationships of various WEDM machining parameters and performance parameters of machining on AISI D2 steel material using response surface methodology (RSM).The significant machining parameters and the optimal combination levels of machining parameters associated with performance parameters were also drawn. The observed optimal process parameter settings based on composite desirability (61.4 %) are pulse on time 112.66 μs, pulse off time 45 μs, spark gap voltage 46.95 V, wire feed 2 mm/min, peak current of 99.99 A for achieving maximum MRR, gap current, gap voltage, cutting rate, and minimum SR; finally, the results were experimentally verified.     

The effect of electrolyte current density on the electrochemical machining S-03 material

Selecting an appropriate electrolyte is very important for high-efficiency electrochemical machining novel S-03 special stainless steel aerospace component. A series of experiments were conducted with NaCl, NaNO₃, and their admixture solutions. This research focused on the relationship between current efficiency and current density. The current density effects on surface roughness, machining velocity, and grain boundary corrosion were analyzed. The results showed that: the current efficiency in NaCl electrolyte was 100 % with different concentrations. Under the conditions of 24 V voltage, 30 °C electrolyte, and 0.8 MPa electrolyte pressure, the 10 % NaCl electrolyte can obtain 3.6 mm/min cathode feed speed; the surface roughness is Ra 0.08 μm; and the material removal rate is 411.4 mm³/min. Comparing forward flow to forward flow with added backpressure, we found that: the surface roughness value decreased sharply at 3.6 mm/min in NaCl electrolyte.     

A note on influential control parameters for drilling of hard-to-machine steel by electrochemical discharge machining

In machining processes, determination of influence of process parameters on performance parameters is an interesting field for many researchers. Recently, Cotea?? et al. (Mater Manuf Process 26:1466–1472, 2011) have presented a regression model and the most effective factors on axial wear in electrochemical discharge machining (ECDM). They applied machined hole depth as an input parameter in predicting the axial tool wear. Using the hole length as a factor of variation in this case can be seen in two scenarios. In the current note, these two possible states are investigated, and the most effective process parameters on ECDM are determined by mean analysis, main effect plot and Pareto ANOVA.     

线切割加工工艺参数优化方法综述

线切割是一种非传统的材料加工方法,其主要的工艺参数有峰值电流、开路电压、脉冲宽度、脉冲间隔、伺服电压、丝速和丝的张力等,主要的工艺指标有材料去除率、表面质量、切缝宽度和白层厚度。综述了线切割工艺参数优化的研究方法,主要包括:人工神经网络、响应曲面法、田口法、灰色关联分析法和遗传算法。通过这些方法可以建立工艺参数和工艺指标之间的关系,从而发现影响工艺的重要参数,确定工艺参数的优化组合,预测基于优化参数的工艺指标。     

分流法小孔电火花加工与试验

介绍一种等面积分流法的小孔电火花加工方法,分析等面积电极放电的电火花加工过程,重点研究在等面积电极条件下,等面积单电极与分流多电极加工对加工速度、电极损耗、放电间隙的影响。进行了验证性试验,研究结果表明：小孔分流法加工与单电极加工相比,使加工速度略有减小、放电间隙略有变小、电极损耗略有增加,加工效果具有一致性;分流法电火花加工有利于小孔电火花加工的尺寸控制,通过等面积分流法改变加工工艺,用电火花机床稳定加工参数进行小于机床稳定加工临界值的更小尺寸的小孔加工,是一种新的微小孔电火花加工方法。     

基于加工精度的齿轮几何参数的选择

应用网格图法分析研究采用蜗杆砂轮磨齿机加工高精度渐开线圆柱齿轮齿廓时,节点附近出现凹下的齿形误差 现象,得到了避免由于与刀具啮合齿数的变化所引起的齿形误差的齿轮变位系数选择方法,并通过实验进行验证。     

Experimental investigation and parameter optimization of near-dry wire-cut electrical discharge machining using multi-objective evolutionary algorithm

The near-dry wire-cut electrical discharge machining (WEDM) process is an environment-friendly manufacturing process, in which there is no harmful effect to the operators. The authors focus on the non-polluting ways to cut the materials and to meet the technical requirements like high material removal rate (MRR) and low surface roughness (Ra). In the near-dry WEDM, the finite discrete periodic series sparks between the wire electrode and conducting work material separated by minimum quantity of deionized water mixed with compressed air (air-mist) as a dielectric medium. In the present research, parametric analysis of the process has been performed with the molybdenum wire tool and high speed steel (HSS-M2) work piece. Experiments have been performed using air-mist as the dielectric medium to study the impact of gap voltage, pulse-on time, pulse-off time, air-mist pressure and discharge current on the MRR and Ra using the mixed orthogonal (L₁₈) array-Taguchi method. Taguchi based analysis of variance test was performed to identify the significant parameters. The gap voltage, pulse-on time, discharge current and air-mist pressure were found to have momentous effects on MRR and Ra. The best regression models for MRR and Ra have been developed by regression analysis. The optimal rough and finish cutting parameters have been predicted by Pareto-front using the multi-objective evolutionary algorithm (MOEA).     

Electrical discharge machining of submicron holes using ultrasmall-diameter electrodes

We have carried out the electrical discharge machining (EDM) of submicron holes using ultrasmall-diameter electrodes. Two types of electrode were used: tungsten electrodes fabricated by the combination of wire electrodischarge grinding and electrochemical machining, and silicon electrodes originally designed as probes for scanning probe microscopes. The diameters of the former and latter were 1 μm or less, and less than 0.15 μm, respectively. Holes were drilled using a relaxation-type pulse generator at an open-circuit voltage of less than or equal to 20 V with the machine's stray capacitance as the only capacitance. Using tungsten electrodes, holes of less than 1 μm in diameter and more than 1 μm in depth were successfully drilled. A 1.3-μm-wide slot was also fabricated by drilling many holes with a small pitch. It was possible to drill holes of approximately 0.5 μm diameter using silicon electrodes because the electrode diameter was less than those of the tungsten electrodes. These holes have the smallest reported diameter for holes drilled by EDM, indicating the possibility of submicron- and nanoscale machining by EDM.