A method for identification of geometrical tool changes during machining of titanium alloy Ti6Al4V

There exists an increasing demand for cost and time-efficient cutting tests for describing the performance of different combinations of cutting tools and workpiece materials in the cutting process both in industry and academia. Cutting tools are expected to withstand the heat and the pressure developed during the machining of difficult-to-machine materials such as Ti6Al4V. This article introduces a new test method which may be used in order to analyze both the machinability of a workpiece material as well as the cutting tool behavior. The experiments were performed by using a predefined sequence of feeds, a so-called Stepwise Increased Feed Test. A gradually increased load on the cutting edge was thus applied up to the point where plastic deformation of the cutting edge was obtained. The limit for the initial change in tool geometry was identified through analysis of measured cutting forces.     

Tool wear and cutting forces under cryogenic machining of titanium alloy (Ti17)

Titanium alloy is well known for its difficulty to machine, owing to the important “tool wear” phenomenon. Machining assistance is an interesting solution to lengthen the tool lifetime. In this study, we focused on the effect of cryogenic assistance—during machining of Ti17—on the tool wear and cutting forces for different combinations of cutting speed, feed rate and depth of cut. Compared to conventional lubrication, cryogenic support lengthens the tool life for all tested conditions and has no significant influence on cutting force. A comparison of the cryogenic effect and high-pressure water jet assistance is also presented.     

智能化主轴单元

结合对智能化机床的借鉴,概括了智能化主轴单元的特征,介绍了其发展现状,并对其关键技术做出归纳,最后对其发展前景做出展望.     

车削加工工艺参数优化

针对车削加工中的约束优化问题,建立以切削速度v和进给量f为优化变量、以加工成本最小为目标的约束优化设计模型.提出了改进约束处理的自适应罚函数法和一种改进差分进化(Improved Differential Evolution,IDE)算法.应用IDE算法求解切削参数约束优化问题的全局最优解.给出了数值实例,通过与已有结果的比较,表明结合约束处理的IDE算法的有效性和稳健性.     

Effect of microstructure and cutting speed on machining behavior of Ti6Al4V alloy

Machining of aerospace and biomedical grade titanium alloys has always been a challenge because of their low conductivity and elastic modulus. Different machining methods and parameters have been adopted for high precision machining of titanium alloys. Machining of titanium alloys can be improved by microstructure optimization. The present study focuses on the effect of microstructure on machinability of Ti6Al4V alloys at different cutting speeds. Samples were subjected to different annealing conditions resulting in different grain sizes and local micro-strains (misorientation). Cutting forces were significantly reduced after annealing; consequently, sub-surface residual stresses were reduced. Deformation twinning was also observed on samples annealed at a higher temperature due to larger grain size. Initial strain free grains and deformation twinning during machining reduces the cutting force at higher cutting speed.     

核电稳压封头数控加工参数优化及加工仿真研究

核电稳压封头尺寸大,质量大,难以加工,生产效率低.目前,国内对提高核电稳压封头加工效率的研究很少.本研究首先以最高生产效率为目标建立铣削参数数学模型,通过遗传算法对数控加工参数优化,利用优化的参数对封头进行加工仿真.研究结果表明:适当的参数优化在保证加工要求的情况下,能够缩短加工时间,提高加工效率.     

The effects of cooling conditions on surface integrity in machining of Ti6Al4V alloy

This paper presents results from a comparative study of machining of Ti6Al4V alloy under dry, minimal quality lubrication, and cryogenic cooling conditions using coated tools at varying cutting speeds and feed rates. The influence of the cooling conditions on surface integrity and the product performance was studied in terms of surface roughness, metallurgical conditions, including microstructure, hardness, grain refinement, and phase transformation of the machined product. Results show that cooling conditions affect surface integrity of the product signifying the benefits of cryogenic cooling in improving the overall product performance.     

Tool wear prediction of machining hydrogenated titanium alloy Ti6Al4V with uncoated carbide tools

Tool wear is a problem in the turning of titanium alloy, and it is thus of great importance to understand and quantitatively predict tool wear and tool life. In this paper, a combined tool wear model including abrasive, adhesion, and diffusion wear has been implemented in a commercial finite element (FE) code to predict tool wear. Many key problems in tool wear simulation are presented and discussed such as temperature distribution, the updating of tool geometry, and the smoothing of wear boundary. Subsequently, a finite element method wear prediction model is built, and the results are compared with the experimental value; a good agreement was found. Simulated results showed that cutting force will decrease first and then increase with the increase of the concentration of hydrogen, while tool life varies in the opposite way; therefore, the optimum value of hydrogen content is about 0.3 %. The addition of 0.3 % hydrogen could improve tool life greatly, and its tool life is more than three times that of the as-received material. The hydrogenation process's favorable effect is limited by cutting parameters and cooling conditions. According to the numerical results, an appropriate machining speed and higher feed is the selection criterion for high-efficiency machining of hydrogenated titanium alloy. Furthermore, a reasonable range of cutting parameters is found; the cutting speed is in the range of 50–100 m/min, and the feed is in 0.15–0.25 mm/rev.     

Intelligent scheduling of automated machining systems

An automated machining system involves concurrent use of manufacturing resources, alternative process plans and flexible routings. High investment in the installation of automated facilities requires an efficient scheduling system that is able to allocate the resources specified for operations over a scheduling horizon. The primary emphasis of this paper is to generate schedules that accurately reflect details of the automated environment and the objectives stated for the system. In this paper, a rule for dispatching operations, named the Most Dissimilar Resources (MDR) dispatching rule, is introduced. A scheduling algorithm for automated machining is presented. Using the previous simulation research for this topic, a rule-based scheduling system is constructed. An architecture for an intelligent scheduling system is proposed, and the system has a high potential to provide efficient schedules based on the task-specific knowledge for the dynamic scheduling environment.     

轻金属合金的高速加工

1．引言 高速加工技术是极具潜力的先进制造技术,但是,它从理论概念到工业化经过了大约60年的时间,这主要是因为在初始研究阶段当时的生产设备无法满足高速加工的要求。     

Mechanical properties of subsurface layers in the machining of the titanium alloy Ti10V2Fe3Al

Journal of Mechanical Science and Technology - We experimentally analyzed the forming of micromechanical properties in subsurface layers of machined workpieces depending on cutting parameters such...     

A study on laser assisted machining of Ti10V2Fe3Al alloy with varying laser power

Laser-assisted machining (LAM) is a promising technique to improve the machinability of various difficult-to-machine materials such as steels, nickel and titanium alloys and metal-matrix composites. Most of the research studies are focused on analyzing the effect of various cutting parameters such as cutting speeds, feed rates and depth of cut at a constant laser power despite being reported that the maximum benefit of the LAM technique can be realised when all parameters including laser power are optimised. Therefore, the primary objective of this paper is to assess the effect of laser power on the cutting temperature and cutting forces including force fluctuations during the machining of Ti10V2Fe3Al alloy. A cutting force reduction of at least 10 % was found using the assistance of a 1,600 W laser beam between cutting speeds of 55–140 m/min. Nevertheless, it was concluded that a power of 800–1200 W for the laser beam is best suited during LAM of Ti10V2Fe3Al alloy within a cutting speed range of 55–100 m/min. Further, higher cutting speeds were recommended when employing a higher power laser beam to avoid problems such as chatter and chip pile-up.     

Tool wear analysis and improvement of cutting conditions using the high-pressure water-jet assistance when machining the Ti17 titanium alloy

This paper presents experimental results concerning the machinability of the titanium alloy Ti17 with and without high-pressure water jet assistance (HPWJA) using uncoated WC/Co tools. For this purpose, the influence of the cutting speed and the water jet pressure on the evolution of tool wear and cutting forces have been investigated. The cutting speed has been varied between 50 m/min and 100 m/min and the water jet pressure has been varied from 50 bar to 250 bar. The optimum water jet pressure has been determined, leading to an increase in tool life of approximately 9 times. Compared to conventional lubrication, an increase of about 30% in productivity can be obtained.     

Intelligent diagnostic technique of machining state for grinding

Successful grinding of a final product depends upon a large number of parameters that affect the grinding result and are strongly interlinked. It is, therefore, difficult to detect directly the generation of grinding faults such as chatter vibration and burning. In this paper, to achieve the development of an intelligent diagnostic technique for chatter vibration and burning phenomena on grinding process, acoustic emission signals were processed and signal parameters of the acoustic emission were also determined. In addition, a neural network was used as a diagnostic technique of the grinding state. A momentum coefficient, learning rate, and structure of the hidden layer were determined during the iterative learning process and the performance of the diagnostic technique was evaluated.     

普通高速钢刀具加工高温合金零件

介绍普通高速钢立铣刀加工GH864高温合金时的切削特点 ,分析加工中的磨损机理 ,通过改变刃磨角度 ,选取了合理的几何参数 ,并给出切削用量     

加工直排网格孔的R参数程序改进

利用西门子840D数控系统的可编程偏移、镜像功能,改进加工直排网格孔的普通R参数程序,极大地提高了生产效率.     

Experimental investigation of tool wear and machining rate in rotary ultrasonic machining of nickel alloy

Nickel alloys possess the excellent potential at high temperature and resistance to oxidation/corrosion owing to its high nickel content. These materials necessitate non-traditional machining methods. The rotary ultrasonic machining (RUM) process comes into existence as a superior alternative to the conventional machining of nickel alloys. The processing of these alloys using RUM needs attention. This article details the multi-response optimization in RUM of nickel alloy using the desirability concept. The present work is carried out with two shapes of the tool: (i) Plain tool and (ii) lateral slotted tool. During RUM, the process parameters—power rating tool rotation, abrasive diamond grit size and feed rate are varied. Compared with the plain tool, the lateral slotted tool shows the more efficient machining rate (MR) with less tool wear (TW). The micro-graphs disclose the mechanism of MR and TW during RUM.     

钛合金薄壁零件加工工艺技术研究

结合钛合金零件的加工特点,对钛合金薄壁零件进行深入分析,通过切削刀具材料、刃磨角度、切削要素、加工流程、浇注方式和夹紧力的制定等参数选择,解决钛合金薄壁零件精度高、难加工和易变形的切削难题。提高零件加工质量,从而达到保证零件尺寸精度及形位公差的目的。