Reliability of electrode wear compensation based on material removal per discharge in micro EDM milling

This paper investigates the reliability of workpiece material removal per discharge (MRD) estimation for application in electrode wear compensation based on workpiece material removal. An experimental investigation involving discharge counting and automatic on the machine measurement of removed material volume was carried out in a range of process parameters settings from fine finishing to roughing. MRD showed a decreasing trend with the progress of the machining operation, reaching stabilization after a number of machined layers. Using the information on MRD and discharge counting, a material removal simulation tool was developed and validated.     

一种电火花加工螺纹电极的定位方法

介绍了一种电火花加工螺纹电极的定位方法,使得电火花加工螺纹型腔时,可以使用多个电极进行粗、精加工,达到提高螺纹精度及降低表面粗糙度值的目的,并可实现模具试模后对螺纹型腔的尺寸修整。     

电火花加工中电极保护层厚度预测研究

针对电火花加工的时变非线性特性,提出了基于神经网络的电极保护层预测模型,利用该网络预测电极保护层的厚度,有效地利用覆盖效应实现电极低损耗加工。在模型建立的过程中,为克服前馈式多层神经网络算法的不足,提出了一种基于改进遗传算法的前馈神经网络自动优化设计方法,用以完成对网络结构和权值空间的搜索,提高神经网络的收敛速度和搜索全局最优解的能力。     

Dendrite fragmentation and the effects of fluid flow in castings

In the absence of grain-refining additions to a melt or of any significant heterogeneous nuclei, equiaxed grains can only originate in a casting from primary dendrite fragments. Thus, it is pertinent to understand how dendrites become fragmented and to explain why liquid stirring should appear to “break up” and refine the grain structure. Dendrite fragmentation occurs by local remelting, and fluid flow is important as a dispersal mechanism. A. Hellawell earned his D.Phil. in physical science at Oxford University in 1956. He is currently emeritus research professor at Michigan Technological University. He is also a member of TMS. S. Liu earned his M.S. in materials science and engineering at Northwestern Polytechnical University, China, in 1989. He is currently a Ph.D. candidate at Michigan Technological University. S.Z. Lu earned his Ph.D. in metallurgical engineering at Michigan Technological University in 1986. He is currently a research associate professor at Michigan Technological University. He is also a member of TMS.     

Investigation of lead and tilt angle effects in 5-axis ball-end milling processes

Five-axis milling is widely used in aerospace, die-mold and automotive industries, where complex surfaces and geometries are machined. Being special parameters of 5-axis milling, lead and tilt angles have significant effects on the process mechanics and dynamics which have been studied very little up to now. In this paper, first of all, effects of tool tip contact on the surface finish quality is presented, and conditions to avoid tip contact in terms of lead and tilt angles and depth of cut are stated. The effects of lead and tilt angles on cutting forces, torque, form errors and stability are investigated through, modelling and verified by experimental results. It is shown that the cutting geometry, mechanics and dynamics vary drastically and non-linearly with these angles. For the same material removal rate, forces and stability limits can be quite different for various combinations of lead and tilt angles. The results presented in the paper are expected to help understanding of complex 5-axis milling process mechanics and dynamics in a better way. The results should also help selection of 5-axis milling conditions for higher productivity and machined part quality.     

石墨电极电火花加工性能的影响因素分析

影响石墨电极电火花加工性能的因素很多，各因素的合理配合对电火花加工特性有重要的影响。分析了主轴性能、脉冲电源及智能控制、工作液、电参数和加工极性选择等对石墨电极加工性能的影响，为生产实践提供了理论依据。     

石墨电极在彩电模具电火花加工中的应用

通过彩电前壳模具喇叭网孔镶件电火花加工,对紫铜电极和石墨电极加工结果进行分析比较,指出石墨材料在制作大电极,特别是在对电极损耗有严格要求的电火花加工时,石墨电极比紫铜电极有许多优点。指出专用石墨作电火花加工电极的优势正逐渐被大家认识,将成为企业首选的电火花加工电极材料。     

球磨时间和转速对球磨法制备纳米锑粉的影响

以250 μm大小的锑粉为原料,在添加相同含量蒸馏水和烷基酚聚氧乙烯醚的条件下,采用湿法机械球磨的方式制备出不同类型的锑基粉末.采用XRD、TEM及FT-IR对制备的锑基粉末的结构、形貌及粒径大小进行了表征分析,研究了球磨时间和球磨转速对锑粉制备的影响.结果表明:当锑粉原料中加入1 ml/g蒸馏水和0.2 ml/g OP-1O湿磨时,球磨转速为150r/min、球磨时间为18 h可制备出分散良好、粒径分布均匀、平均粒径约为10 nm的锑粉.     

石墨电极在模具零件电火花加工中的应用

介绍了石墨材料的电火花加工特性、石墨电极材料的选择和石墨电极的制作技术,阐述了石墨电极的电火花加工参数,列举了多个石墨电极加工的应用案例,对扩大石墨电极材料的应用范围和提高其应用水平具有一定参考价值。     

电加工电极专用石墨的物理特性及选用原则

阐述了电加工电极专用石墨的物理特性及其对放电加工工艺效果的影响,详细介绍了电加工电极专用石墨的选用原则,有助于根据加工需要科学地选用电加工电极专用石墨材料,提高电火花成形加工效果。     

柔性钛电极电火花合成TiN涂层

文中提出一种利用柔性钛电极在钛合金TC4表面合成TiN涂层以改善工件表面性能的新方法.在加工中利用柔性钛电极与钛合金TC4表面进行电火花放电,同时通过钛电极内部向加工区域通入氮气,利用电火花放电能量在工件表面反应生成TiN涂层.测量其表面硬度并利用SEM,XRD等手段对其涂层微观形貌和组分进行测试.结果表明,在TC4工件表面制备出了TiN强化涂层,涂层致密、均匀、连续;TiN涂层厚度超过1 mm;涂层主要由TiN强化相组成,显微硬度高达1859.6 MPa;涂层表面的放电坑大而浅且存在刮削痕迹,柔性钛电极丝对TiN涂层有较强的刮削涂覆作用;TiN涂层与基体之间相互渗透形成冶金结合.     

Investigation of corrosion behavior at elbow by array electrode and computational fluid dynamics simulation

The present study focuses on the flow-accelerated corrosion (FAC) behavior of A106Gr.B steel at 90° elbow by electrochemical measurement and computational fluid dynamics (CFD) simulation. The FAC rates under turbulent flows with a velocity of 3 and 1.5 m/s were measured by an array electrode technique in a loop system. The experimental results reveal that the maximum FAC rate appears at the extrados of 90° elbow, consistent with the locations from the rupture of the carbon steel piping in the worst cases at elbows. In addition, an effective mass transfer coefficient in consideration of the geometric factor was used to evaluate the FAC rate at intrados and extrados of the 90° elbow by CFD simulation. The predicted results are in good agreement with the experimental values.     

Compound machining of titanium alloy by super high speed EDM milling and arc machining

A novel compound machining of titanium alloy (Ti6Al4V) by super high speed electrical discharge machining (EDM) milling and arc machining was proposed in this paper. The power supply consisted of a pulse generator and a DC power source which were isolated from each other. A rotating pipe graphite electrode was connected to the negative pole of the power supply. The plasma channel was able to deionize, and maximum material removal rate (MRR) reached 21,494 mm³/min with a relative electrode wear ratio (REWR) of 1.7% because of high current and efficient flushing. Compared with traditional EDM, the compound machining achieved a significantly higher MRR but a similar REWR. To investigate the characteristics of the compound machining, the effects of electrode polarity, peak voltage, peak current, and flushing pressure on the performance of the process, including its MRR, REWR, and radius of overcut (ROC), were determined. In addition, scanning electron microscopy, X-ray diffraction, and microhardness analysis were conducted. Result shows that the proposed method can machine difficult-to-machine materials efficiently.     

Feasibility of wear compensation in micro EDM milling based on discharge counting and discharge population characterization

This paper investigates the applicability of real time wear compensation in micro EDM milling based on discharge counting and discharge population characterization. Experiments were performed involving discharge counting and tool electrode wear measurement in a wide range of process parameters settings involving different current pulse shapes. A strong correlation is found between average discharge energy of the populations and wear and material removal per discharge. A validation was carried out showing the feasibility of the proposed approach.     

不同电极电火花加工硬质合金的效率研究

通过实验的方式对采用不同电极电火花加工技术加工硬质合金的效率进行了研究。通过调整加工过程中的脉冲宽度和开路电压，变换加工电极，探讨了不同电极材料、开路电压及脉宽加工硬质合金的加工效率的影响.     

Dependence of the melting rate of the electrode in CO2 welding on electrode extension

The data obtained for the variation of the melting rate and voltage in CO₂ welding with the change of the electrode extension are analysed. The dependences of the mean resistance of the unit length of the extension, the increase of the melting factor and the arc voltage on the electrode wire diameter are determined. The appropriate approximating dependences are derived. The average value of the melting factor in the reverse polarity arc at zero extension is determined.     

Fuzzy control of feed rate in end milling operations

In order to improve productivity in end milling operations, a new adaptive control system based on fuzzy logics to maintain a constant cutting force is developed. It is shown, by experimental cutting tests, that the cutting tool travels in the air cut with fast feed rate, yet in the varying depths of cut, the tool travels with an adjustable feed rate to prevent the occurrence of tool breakage and maintain a high metal removal rate.     

Effect of temperature,strain rate and fibre orientation on the plastic flow behaviour and formability of AZ31 magnesium alloy

The sheet formability of AZ31 magnesium alloy has been widely investigated by means of uniaxial tensile and hemispherical punch tests, performed at different temperatures and strain rates, using samples with different fibre orientations. The results of the uniaxial tensile tests were analysed in terms of flow curves, ductility and microstructural evolution. They show that the flow stress decreases and ductility increases as temperature rises and strain rate reduces; the ductility is almost independent of the fibre orientation that, however, slightly affects the flow stress values. The formability, described by the forming limit curves (FLCs), improves with increasing temperature and decreasing strain rate. Moreover, formability along the rolling direction (RD) is higher than that along the transversal one (TD), even if the FLCs obtained along the TD have a larger extension in the drawing side than the ones along the RD. Such behaviours were related to the constitutive parameters and microstructure developed during deformation.     

Influence of the direction and flow rate of the cutting fluid on tool life in turning process of AISI 1045 steel

High-pressure coolant (HPC) delivery is an emerging technology that delivers a high-pressure fluid to the tool and machined material. The high fluid pressure allows a better penetration of the fluid into the tool–workpiece and tool–chip contact regions, thus providing a better cooling effect and decreasing tool wear through lubrication of the contact areas.The main objective of this work is to understand how the tool wear mechanisms are influenced by fluid pressure, flow rate and direction of application in finish turning of AISI 1045 steel using coated carbide tools.The main finding was that when cutting fluid was applied to the tool rake face, the adhesion between chip and tool was very strong, causing the removal of tool particles and large crater wear when the adhered chip material was removed from the tool by the chip flow. When cutting fluid was not applied to the rake face, adhesion of chip material to the face did occur, but was not strong enough to remove tool particles as it moved across the face, and therefore crater wear did not increase.