High-speed milling of titanium alloys using binderless CBN tools

The performance of conventional tools is poor when used to machine titanium alloys. In this paper, a new tool material, which is binderless cubic boron nitride (BCBN), is used for high-speed milling of a widely used titanium alloy Ti–6Al–4V. The performance and the wear mechanism of the BCBN tool have been investigated when slot milling the titanium alloy in terms of cutting forces, tool life and wear mechanism. This type of tool manifests longer tool life at high cutting speeds. Observations based on the SEM and EDX suggest that adhesion of workpiece and attrition are the main wear mechanisms of the BCBN tool when used in high-speed milling of Ti–6Al–4V.     

Cutting performance of PVD-coated carbide and CBN tools in hardmilling

In this study, cutting performance of CBN tools and PVD-coated carbide tools in end-milling of hardened steel was investigated. In high-speed dry hardmilling, two types of CBN tools were applied: the CBN-rich type and an ordinary one. In the case of relatively low-speed milling, on the other hand, a few coated carbide tools were selected where four kinds of coating films, TiN, TiCN, TiAlN and multi-layered TiAlN/AlCrN, were deposited on the K10 and P30 grade carbide. The cutting performance was mainly evaluated by tool wear, cutting temperature, cutting force and surface roughness. In dry cutting of hardened carbon steel with the ordinary CBN tool, the cutting tool temperature rose rapidly with increase in cutting speed; and tool temperature reached approximately 850 °C at the cutting speed of 600 m/min. In the case of the CBN-rich tool, the cutting temperature decreased by 50 °C or more because of its high thermal conductivity. It is remarkable that tool wear or damage on a cutting tool was not observed even when the cutting length was 156 m in both CBN tools. In the case of coated carbide tools, the temperatures of TiN-, TiCN- and TiAlN-coated carbide tools rose as cutting proceeded because of the progress of tool wear, but that of TiAlN/AlCrN-coated carbide tool hardly rose due to little tool wear. When the base material was K10 grade carbide, tool temperature was lower than that of P30 with any coating. The tool flank wear depends considerably on hardness and oxidizing temperature of the coating film.     

Tool wear and chip formation during hard turning with self-propelled rotary tools

This paper presents a performance assessment of rotary tool during machining hardened steel. The investigation includes an analysis of chip morphology and modes of tool wear. The effect of tool geometry and type of cutting tool material on the tool self-propelled motion are also investigated. Several tool materials were tested for wear resistance including carbide, coated carbide, and ceramics. The self-propelled coated carbide tools showed superior wear resistance. This was demonstrated by evenly distributed flank wear with no evidence of crater wear. The characteristics of temperature generated during machining with the rotary tool are studied. It was shown that reduced tool temperature eliminates the diffusion wear and dominates the abrasion wear. Also, increasing the tool rotational speed shifted the maximum temperature at the chip–tool interface towards the cutting edge.     

高速切削刀具系统

根据高速切削对刀具系统的要求,分析了高速回转刀具的结构特点以及常规7：24锥度刀柄结构存在的不足,介绍了国外对7：24锥度刀柄的多种改进型设计和替代性设计方案,分析了各种设计方案的优缺点。     

High-speed machining of titanium alloys using the driven rotary tool

Machining of titanium at high cutting speeds such as from 4 m/s to 8 m/s is very challenging. In this paper, a new generation of driven rotary lathe tool was developed for high-speed machining of a titanium alloy, Ti–6Al–4V. The rotary tool was designed and fabricated based on the requirements of compact structure, sufficient stiffness and minimal edge runout. Cylindrical turning experiments were conducted using the driven rotary tool (DRT) and a stationary cutting tool with the same insert, for comparison in the high-speed machining of Ti–6Al–4V. The results showed that the DRT can significantly increase tool life. Increase in tool life of more than 60 times was achieved under certain conditions. The effects of the rotational speed of the insert were also investigated experimentally. Cutting forces were found to decline slightly with increase of the rotational speed. Tool wear appears to increase with the rotational speed in a certain speed range.     

Hard turning of an alloy steel on a machine tool with a polymer concrete bed

Finish turning of 39NiCrMo3 alloy steel in the hardened state has been widely investigated under dry, minimum quantity of lubricant and wet cutting conditions, using inserts in ceramic and PCBN materials, on turning centers equipped with polymer concrete and cast iron beds. The progress of workpart surface roughness and tool wear with cutting time has been measured and the results analysed and discussed in detail. It has been observed that dry cutting leads to the lowest values of tool wear and surface roughness, whilst the minimal quantity of lubricant technique does not provide advantages regarding to dry turning. Furthermore, the PCBN inserts are characterised by a longer tool life than the one exhibited by the ceramic inserts. Finally, the outstanding damping and high rigidity of the polymer concrete bed has a beneficial effect on both tool wear and workpiece surface finish.     

Temperature fields in a chip during high-speed orthogonal cutting—An experimental investigation

During the cutting process, the temperature field in the chip is measured by using the principle of pyrometry in the visible spectral range. The mechanical device developed to reproduce orthogonal cutting conditions and to reach very high cutting speed (up to 120 m/s) is used for a range of velocities from 10 to 70 m/s. The presented experimental results concern two materials chosen following the form of chip generated: a low carbon steel (C15) and a low alloyed medium carbon steel (42CrMo4). The performances of the measurement set-up are completed by the possibility of recording real time photographs of the chip formation. These records make the analysis of temperature maps easier and allow specific parameters as the contact length at the tool-chip interface or the shear angle to be determined. The non-uniform heating in the chip is emphasized by the presence of a maximal temperature area. The temperature fields measured for a cutting speed around 20 m/s present maximums of 870 °C for 42CrMo4 and 630 °C for C15 located near the tool–chip interface. The effects of cutting velocity on the maximum temperature value in the chip and the location of this heat zone are presented. This maximum increases with the cutting velocity contrary to its location which presents few variations. The experimental results are compared with an analytical approach.     

切削参数对碳钢微量润滑切削温度的影响

为了了解切削参数影响碳钢微量润滑切削温度的规律,通过45钢的车削实验,利用自然热电偶测温,探明在干切削、传统浇注润滑和微量润滑条件下,不同切削参数对切削温度的影响及原因。实验结果表明:MQL切削温度随切削参数增大而上升,切削速度对MQL温度影响最大,切削深度影响最小;在低切削速度时,MQL冷却效果优于传统浇注润滑,在中、高速时,MQL冷却效果比浇注润滑差;MQL冷却能力随切削速度和进给量增大而减弱,不随切削深度而变化。     

Effect of the lubrication-cooling technique, insert technology and machine bed material on the workpart surface finish and tool wear in finish turning of AISI 420B

The paper is focussed on the effects produced by cutting operations on workpiece surface finish and tool wear. To this end, finish turning of AISI 420B stainless-steel was carried out under wet, minimum quantity of lubricant and dry cutting conditions, using both conventional and wiper technology inserts, on turning centres equipped with beds made in polymer concrete and cast iron. The workpiece surface finish and tool wear versus cutting volume were measured, and the results analysed and discussed in detail. The most significant results were: (i) the lubrication-cooling technique does not significantly affect the tool wear, whilst wet cutting produces the worst surface finish, (ii) the wiper inserts allow obtaining of the best surface finish, and (iii) the use of polymer concrete bed leads to an improved behaviour in terms of tool wear and surface roughness.     

基于微磨削方法的微织构刀具制备与切削性能研究

目的研究表面微织构对硬质合金刀具切削性能的影响。方法采用微磨削方法在硬质合金刀具前刀面加工出具有不同结构参数的横向、纵向和交叉微织构,通过AL6061切削试验和有限元切削仿真,研究表面微织构对硬质合金刀具的切削温度及刀具磨损的影响。结果采用V形金刚石砂轮微磨削方法能够加工出几何形状规则且表面质量良好的表面微织构。与无织构刀具相比,微织构刀具的切削温度明显降低,高温区域明显减少,其中横向织构刀具降温效果最为显著。微织构刀具的切削温度随沟槽间距的增大而升高,沟槽间距为150μm时,切削温度最低。表面微织构能够有效减轻刀具前刀面的粘结磨损,横向织构刀具减摩抗粘效果最好,且采用较小的沟槽间距更利于减轻刀具的粘结磨损。随着切削速度的增加,表面微织构的抗粘结作用更加明显,当切削速度为150 m/min时,沟槽间距为150μm的横向织构刀具的切屑粘结面积最小。结论在横向、纵向和交叉织构刀具中,沟槽间距为150μm的横向织构刀具切削性能最好,即降温效果、抗粘结性能最为显著。     

Fundamental investigation of ultra-precision ductile machining of tungsten carbide by applying elliptical vibration cutting with single crystal diamond

This paper presents essential investigations on the feasibility of ductile mode machining of sintered tungsten carbide assisted by ultrasonic elliptical vibration cutting technology. It lays out the foundations toward efficient application of elliptical vibration cutting technology on tungsten carbide. Tungsten carbide is a crucial material for glass molding in the optics manufacturing industry. Its grain size and binder material have significant influence not only on the mechanical and chemical properties but also on the machining performance of tungsten carbide. In order to investigate the influence of material composition on tungsten carbide machining, a series of grooving and planing experiments were conducted utilizing single crystal diamond tools. The experimental results indicated that as compared to ordinary cutting where finished surface deteriorates seriously, ductile mode machining can be attained successfully by applying the elliptical vibration cutting technique. It was also clarified that the binder material, the grain size, cutting/vibration conditions as well as crystal orientation of the diamond tool have significant influence on the tool life and the machined surface quality. Based on these fundamental results, feasibility of micro/nano-scale fabrication on tungsten carbide is investigated. By applying amplitude control sculpturing method, where depth of cut is arbitrary changed by controlling the vibration amplitude while machining, ultra-precision textured grooves and a dimple pattern were successfully sculptured on tungsten carbide in ductile mode.     

高速球铣路径对淬硬钢SKD11表面摩擦特性的影响

通过高速铣削试验与环-块摩擦磨损试验,借助白光干涉仪、超景深三维显微镜、显微硬度计等分析检测设备,研究了走刀路径对淬硬模具钢SKD11表面摩擦特性的影响。结果表明:球铣加工表面摩擦特性具有方向性,当走刀方向与摩擦方向垂直时,摩擦因数最小,磨痕宽度最窄,当二者夹角成45°时,摩擦因数最大,磨痕宽度最宽。球铣走刀路径影响加工表面形貌取向,表面形貌通过改变接触应力和磨屑捕捉能力来影响犁耕效应和黏着效应,进而影响摩擦特性。干摩擦工况下,主要磨损机理是磨粒磨损与氧化磨损,试验15 min后表面微沟槽形貌均已消失;而润滑工况下,表面微沟槽依然清晰,走刀路径与摩擦方向夹角成0°与45°试样表面出现磨粒磨损特征,而夹角成90°试样表面无明显划痕,表明采用该路径进行球铣加工具有较好的减磨效果。     

Refrigerated cooling air cutting of difficult-to-cut materials

One approach to enhance machining performance is to apply cutting fluids during cutting process. However, the use of cutting fluids in machining process has caused some problems such as high cost, pollution, and hazards to operator's health. All the problems related to the use of cutting fluids have urged researchers to search for some alternatives to minimize or even avoid the use of cutting fluids in machining operations. Cooling gas cutting is one of these alternatives. This paper investigates the effect of cooling air cutting on tool wear, surface finish and chip shape in finish turning of Inconel 718 nickel-base super alloy and high-speed milling of AISI D2 cold work tool steel. Comparative experiments were conducted under different cooling/lubrication conditions, i.e. dry cutting, minimal quantity lubrication (MQL), cooling air, and cooling air and minimal quantity lubrication (CAMQL). For this research, composite refrigeration method was adopted to develop a new cooling gas equipment which was used to lower the temperature of compressed gas. The significant experimental results were: (i) application of cooing air and CAMQL resulted in drastic reduction in tool wear and surface roughness, and significant improvement in chip shape in finish turning of Inconel 718, (ii) in the high-speed milling of AISI D2, cooling air cutting presented longer tool life and slightly higher surface roughness than dry cutting and MQL. Therefore, it appears that cooling air cutting can provide not only environment friendliness but also great improvement in machinability of difficult-to-cut materials.     

高速数控切削用刀柄工具系统

在分析传统BT(7:24锥度)实心长刀柄基础上介绍国外HSK,Big-plus,KMShowa D-F-C等新型工具系统,分析和对比不同高速刀柄的结构特点、装卡过程及其应用场合。指出高速加工工具系统中存在的主要问题及对策,展望高速加工工具系统发展趋势和研究前景,为选用高速工具系统提供了参考。     

Influences of chip serration on micro-topography of machined surface in high-speed cutting

Saw-tooth chip changes from macroscopically continuous ribbon to separated segments with the increase of cutting speed. The aim of this study is to find the correlations between chip morphology and machined surface micro-topography at different chip serration stages encountered in high speed cutting. High strength alloy steel AerMet100 was employed in orthogonal cutting experiments to obtain chips at different serration stages and corresponding machined surfaces. The chips and machined surfaces obtained were then examined with optical microscope (OM), scanning electron microscope (SEM), and white light interferometer (WLI). The result shows that chip serration causes micro-waves on machined surface, which increases machined surface roughness. However, wave amplitudes (surface roughness) at different serration stages are different. The principal factor influencing wave amplitude is the thickness of the sawed segment (tooth) of saw-tooth chip. With cutting parameters in this study, surface roughness contributed by chip serration ranges from 0.39 μm to 1.85 μm. This may bring on serious problems in the case of trying to replace grinding with high-speed cutting in rough machining. Some suggestions have been proposed to control the chip serration-caused surface roughness in high-speed cutting based on the results of the current study.     

The relation between chip morphology and tool wear in ultra-precision raster milling

In the field of ultra-precision machining, the study of the relation between chip morphology and tool wear is significant, since tool wear characteristics can be reflected by morphologies of cutting chips. In this research, the relation between chip morphology and tool flank wear is first investigated in UPRM. A cutting experiment was performed to explore chip morphologies under different widths of flank wear land. A geometric model was developed to identify the width of flank wear land based on chip morphology. Theoretical and experimental results reveal that the occurrence of tool flank wear can make the cutting chips truncated at both their cut-in and cut-out sides, and reduce the length of cutting chips in the feed direction. The width of truncation positions of the cutting chip can be measured and used to calculate the width of flank wear land with the help of the mathematical model. The present research is potentially used to detect tool wear and evaluate machined surface quality in intermittent cutting process.     

Wear and cutting performance of diamond composite material-a comparison with tungsten carbide

A series of wear and rock cutting tests were undertaken to assess the wear and cutting performance of a thermally stable diamond composite (TSDC). The wear tests were conducted on a newly designed wear testing rig in which a rotating aluminium oxide grinding wheel is turned (also known as machined) by the testing tool element.The rock cutting tests were performed on a linear rock-cutting planer. The thrust and cutting forces acting on the tool were measured during these tests. A tungsten carbide element was also studied for comparative purposes. The wear coefficients of both materials were used to evaluate wear performance while cutting performance was assessed by tool wear and the rates of increase in forces with cutting distance.     

高速切削刀具材料的研究进展

本文结合高速切削过程中速度的变化规律,介绍了高速切削加工所使用的几种刀具材料硬质合金、陶瓷、金刚石和立方氮化硼的性能特点及其应用,并对今后高速切削刀具材料的研究提出了建议。     

PcBN刀具连续车削淬硬钢性能的研究

为了研究PcBN刀具在干式连续车削条件下刀具的性能,选用两种不同的PcBN刀具,在不同切削速度及不同工件硬度条件下,对淬硬钢进行车削试验。在此基础上,对刀具前、后刀面的显微形貌特征进行了观察,分析了刀具的失效机理。结果表明:切削速度对刀具的切削寿命影响很大,随着切削速度的增加刀具寿命几乎线性下降。硬度也是影响刀具切削寿命的重要因素之一,当v190 m/m in时,刀具切削硬度为(64±1)HRC工件的寿命比相同条件下切削硬度为(61±1)HRC工件的寿命下降约40%~60%。刀尖温度随着切削速度的增加不多,切屑温度要比刀尖温度高出许多。在本试验中,刀具的失效判据为崩刃或后刀面平均磨损超过0.3 mm。     

High-speed rotary cutting of difficult-to-cut materials on multitasking lathe

This paper aims to realize the high-speed rotary dry cutting of an Inconel 718 at 500 m/min on a multitasking lathe which has an additional milling spindle with an X/Y/Z-axis and inclination control. A series of experiments were conducted and are discussed with respect to the tool face temperature analysis by FEM. It was verified that it is necessary to select an optimum inclination angle, tool rotation speed and tool diameter so as to enable the main cutting force direction to align with the highest rigidity direction of an applied rotary tool. Under preferable cutting conditions, the average tool rake face temperature measured by a thermograph camera was about 300 °C even at a high cutting speed of 500 m/min under dry cutting conditions, and the tool wear decreased dramatically compared with the conventional tools.