PRECISION OF HSK TOOLING SYSTEM IN HIGH SPEED MACHINING

Based on the theory of elastic mechanics and material mechanics, the orientation precision of the hohl schaft kegel（HSK） tooling system in static and dynamic states is theoretically and experimentally studied. The relation between the clamping force and the shank taper is obtained. And a proper clamping force is found to be essential to assure the axial and radial orientation precisions of the HSK tooling system in high speed machining （HSM）. Analytical results show that the reason why the HSK tooling system can keep high precision at the high rotational speed is that the actual axial clamping force keeps the two surfaces of the shank and the spindle in contact all the time.

Wear Mechanism of Cemented Carbide Tool in High Speed Milling of Stainless Steel

Adhesion of cutting tool and chip often occurs when machining stainless steels with cemented carbide tools. Wear mechanism of cemented carbide tool in high speed milling of stainless steel 0Cr13Ni4 Mo was studied in this work. Machining tests on high speed milling of 0Cr13Ni4 Mo with a cemented carbide tool are conducted. The cutting force and cutting temperature are measured. The wear pattern is recorded and analyzed by high?speed camera, scanning electron microscope(SEM) and energy dispersive X?ray spectroscopy(EDS). It is found that adhesive wear was the dominant wear pattern causing tool failure. The process and microcosmic mechanism of the tool’s adhesive wear are analyzed and discussed based on the experimental results. It is shown that adhesive wear of the tool occurs due to the wear of coating, the a nity of elements Fe and Co, and the grinding of workpiece materials to the tool material. The process of adhesive wear includes both microcosmic elements di usion and macroscopic cyclic process of adhe?sion, tearing and fracture.

ZERO TRANSMISSION AND ITS APPLICATION IN HIGH SPEED CNC MACHINE TOOLS

In order to realize high speed machining,the special requirements for the transmission and sturctrue of CNC machine tool have to be satisfied.A high speed spindle unit driven by a built-in motor is developed.An oil-water heat exchange system is used for cooling the spindle motor.The spindle is supported by Si_4N_3 ceramic ball angular contact bearings. An oil-air lubricator is used to lubricate and cool the spindle bearings.Some special structures are taken for balancing the spindle.

Tool Failure Analysis in High Speed Milling of Titanium Alloys

In high speed milling of titanium alloys the high rate of tool failure is the main reason for its high manufacturing cost. In this study,fractured tools which were used in a titanium alloys 5-axis milling process have been observed both in the macro scale using a PG-1000 light microscope and in the micro scale using a Scanning Electron Microscope (SEM) respectively. These observations indicate that most of these tool fractures are the result of tool chipping. Further analysis of each chipping event has shown that beachmarks emanate from points on the cutting edge. This visual evidence indicates that the cutting edge is failing in fatigue due to cyclical mechanical and/or thermal stresses. Initial analyses explaining some of the outlying conditions for this phenomenon are discussed. Future analysis regarding determining the underlying causes of the fatigue phenomenon is then outlined.

Wear Patterns and Mechanisms of Cutting Tools in High Speed Face Milling

High speed machining has received an important interest because it leads to an increase of productivity and a better workpiece surface quality. However, at high cutting speeds, the tool wear increases dramatically due to the high temperature at the tool-workpiece interface. Tool wear impairs the surface finish and hence the tool life is reduced. That is why an important objective of metal cutting research has been the assessment of tool wear patterns and mechanisms. In this paper, wear performances of PCBN tool, ceramic tool, coated carbide tool and fine-grained carbide tool in high speed face milling were presented when cutting cast iron, 45# tempered carbon steel and 45# hardened carbon steel. Tool wear patterns were examined through a tool-making microscope. The research results showed that tool wear types differed in various matching of materials between cutting tool and workpiece. The dominant wear patterns observed were rake face wear, flank wear, chipping, fracture and breakage. The main wear mechanisms were mechanical friction, adhesion, diffusion and chemical wear promoted by cutting forces and high cutting temperature. Hence, the important considerations of high speed cutting tool materials are high heat-resistance and wear-resistance, chemical stability as well as resistance to failure of coatings. The research results will be great benefit to the design and the selection of tool materials and control of tool wear in high-speed machining processes.

Thermodynamics Analysis of Oxidation Wear Behavior of Cemented Carbide Tools in High Speed Machining

The essence of oxidation wear machanism of cenmented carbide tool was studied based on thermodynamics. Standard Gibbs free energy of possible reactions in cutting process at different temperature was calculated using substance Gibbs free energy function methods, and the sequence of reaction possibility order was researched as well as characteristics of every reaction. Theoretical calculation shows that WO3, Co3O4, TiO2 and CoWO4 are the main resultants, which are proved with the experiment results.

MICROSTRUCTURE OF LASER MELTED-RESOLIDIFIED LAYER ON HIGH SPEED TOOL STEEL

The laser melted-resolidified processing on W18Cr4V high speed tool steel has been made us- ing a 1 kW CO_2 continuous wave laser device.The microstructure of the laser melted- resolidified layer has been examined by optical microscopy and transmission electron microscopy(TEM).It was characteristic of extremely fine dendrite in the laser melted- resolidified layer and δ-ferrite in bulk form in the center of dendrite.The predominant twin martensite and a little dislocation martensite existed in the dendrite.The thin plate-like M_(213)C_6 carbide precipitated coherently on the twin martensites along their twin plane.There were both austenite rich in W,V and Cr and M_6C carbide in the interdendritic regions.

HIGH SPEED MILLING OF GRAPHITE ELECTRODE WITH ENDMILL OF SMALL DIAMETER

Graphite becomes the prevailing electrode material in electrical discharging machining （EDM）currently.Orthogonal cutting experiments are carried out to study the characteristics of graphite chip formation process.High speed milling experiments are conducted to study tool wear and cutting forces.The results show that depth of cut has great influence on graphite chip formation.The removal process of graphite in high speed milling is the mutual result of cutting and grinding process. Graphite is prone to cause severe abrasion wear to coated carbide endmills due to its high abrasiveness nature.The major patterns of tool wear are flank wear,rake wear,micro-chipping and breakage. Cutting forces can be reduced by adoption of higher cutting speed,moderate feed per tooth,smaller radial and axial depths of cut,and up cutting.

Effects of honing treatment on AIP-TiN and TiAlN coated end-mill for high speed machining

The objective of this work is to compare the tool performance of TiN and TiA1N coated carbides end-mills deposited by an arc ion plating （ALP） method, using honing treatment to polish the cutting edge surface sleekly. The curve of surface roughness versus honing time showed a rapid improvement initially and thereafter became steady, manifesting a saturation effect. The optimal honing time related to surface roughness was determined to be approximately 20 s. As the surface roughness increased, the critical loads reduced. At an average surface roughness （Ra） of 0.028 p.m, the highest critical loads of TiN and TiAlN coating layers were 98 and 114 N, respectively. Tool performances of uncoated and coated tools were conducted under high speed machining （HSM） of AISI D2 cold-worked die steel （62 HRC）. Consequently, the TiAlN coated end-mill using honing treatment showed excellent tool life under HSM conditions.

High Speed Cutting Inconel 718 with Coated Carbide and Ceramic Inserts

High speed machining (HSM) technology is one of important aspects of advanced manufacturing technology. Nickel-based superalloys have been widely used in the aircraft and nuclear industry due to their exceptional thermal resistance and the ability to retain mechanical properties at elevated temperatures of service environment over 700 ℃. However, they are classified as difficult-to-cut materials due to their high shear strength, work hardening tendency, highly abrasive carbide particles in the microstructure, strong tendency to weld and form built-up edge and low thermal conductivity. They have a tendency to maintain their strength at high temperature that is generated during machining. The Inconel 718 workpiece material used in the experiment was in the hot forged and annealed condition. The commercially available inserts (all inserts were made by Kennametal Inc.) were selected for the tests, a PVD TiAlN coated carbide, a CVD/PVD TiN/TiCN/TiN coated carbide and a CVD Al 2O 3/TiC/TiCN coated carbide were used at the cutting speed range about 50～100 m/min. Three kinds Sialon grade inserts with various geometry and cutting angles were used at the cutting speed range from 100 m/min to 300 m/min. For evaluating the inserts machinability when high speed cutting Inconel 718, Taylor Formula within certain cutting speeds, an high speed cutting experiment of tool life was carried out to establish the models of tool life by means of rapid facing turning test. The conclusions drawn from the turning of Inconel 718 with silicon nitride based ceramic; PVD and CVD coated carbide inserts are as follows: Studies on tool wear in high speed machining. The thorough investigations and studies were made on the tool wear form, wear process and wear mechanism in high speed cutting of difficult-to-machine materials with ceramic tools and with coated carbides. The major wear mechanisms of nickel-based alloys are interactions of abrasive wear, adhesion wear, micro-breakout and chipping. Optimization analysis on the application of high speed machining. Based on the experimental results, the optimal cutting parameters were determined for machining of Inconel 718 at high speed. The recommendation of tool inserts for high speed cutting inconel 718 were ceramic inserts of KY2000 with negative rake angle and KY2100 with round type, the PVD coated carbide insert KC7310 was recommended for its lower price.

Research on dynamic characteristics of high speed milling force based on discontinuous functions

This paper begins with a consideration of the influence of feed per revolution upon the depth of a cut and the impact of the machining method on the direction of tool pressure average and subsequent description of efficient cutting directions and the methods for load cell orientation. The paper goes further into the key conclusions concerning the dependences of the cutting depth at high-speed milling as in the case of discontinuous functions. It ends with recommendations offered for positioning of load cells for cut-up milling and cut-down milling.

高速铣削-激光切割机床数控加工高精度控制技术

激光切割机铣削过程中会因工件变形导致表面出现凹凸不平或波浪状,表面局部区域高低不等,致使机床的浮动轴偏离实际运动轨迹,影响工件铣削加工的质量。为此,提出一种高速铣削-激光切割机床数控加工高精度控制技术。采用运动学理论、矩阵转换函数建立激光切割机床运动数学模型,利用PLC控制器、伺服驱动器及电机等搭建激光切割机床高速铣削加工控制模型,使用负反馈控制算法、位移误差函数控制机床铣削加工浮动轴运动,即当浮动轴执行上浮或者下浮运动时,若浮动轴运动轨迹偏离预设轨迹,调节PLC控制器参数来驱动电机控制作业,使其反向运动,直到落在预设轨迹上,实现铣削加工的高精度控制。实验结果表明,所提技术工件的铣削加工质量高,高速铣削过程中上浮点、下浮点控制误差最大值分别为6 mm、6 mm,铣削加工控制的响应时间为6.8 ms。

TOOL PATH OPTIMIZATION OF POCKET CORNER

In milling around sharp corners, residual materials are left at sharp corners when the stepover is extremely long in the contour-parallel tool path. Milling force at the sharp corner rises momentarily due to the increase of the cutter contact length, thus shortening the tool life and leading to machine chatter, even cutter breakage. Then a tool path improvement method by inserting biarc transition segments in the contour-parallel tool path is proposed for milling the pocket. Using the method, the cutter moves along the biarc transition tool path. And the corner material is removed. The improved tool path is continuous for clearing residual materials at the sharp corner. Finally, the machining experiment validates the proposed method.

Inconel 718镍基高温合金高速切削仿真与刀具磨损机理研究

Inconel 718高温合金因强度高和导热系数低导致其切削加工性较差,采用陶瓷刀具高速切削Inconel 718时存在磨损快、寿命短等问题。通过仿真和试验对比分析,研究切削用量对切削力、切削温度和刀具磨损的影响规律,并获取高速切削过程中刀具前、后刀面温度场和应力场的动态分布规律,为镍基高温合金的高速切削及刀具设计制备提供指导依据。结果表明,切削速度对切削力和切削温度的影响程度小于背吃刀量和进给量;在选择切削参数时,优先选取较高的切削速度;沟槽磨损是抑制陶瓷刀具耐用度的关键因素,主要失效机理是黏结磨损。

高速铣削GH4169合金的刀具磨损研究

为研究高速铣削GH4169合金的刀具磨损问题,采用正交试验法基于DEFORM软件对GH4169合金的铣削加工过程进行了仿真,得到不同组刀具磨损仿真结果,并对仿真结果进行极差分析,得出不同铣削用量对刀具磨损的影响程度和最优方案。同时,对GH4169合金进行实际铣削加工试验,并与仿真结果进行对比分析,验证了仿真模型的有效性和可行性。选取不同的铣削用量,基于DEFORM有限元仿真软件,通过单因素试验法模拟GH4169合金的铣削过程,得出铣削用量对刀具磨损的影响规律。研究结果表明:对刀具磨损的影响程度由大到小依次为每齿进给量、切削速度和背吃刀量,并通过铣削试验验证了此规律的准确性。

新型CVD金刚石涂层刀具铣削高性能各向同性石墨研究

利用自主研发的新型CVD金刚石复合涂层刀具对自行研制的高密高强各向同性石墨材料进行了铣削加工试验,对比测试了新型CVD金刚石复合涂层刀具与PCD刀具的切削性能。试验结果表明,PCD刀具铣削加工25min其后刀面磨损已超过磨钝标准0.3 mm,新型CVD金刚石复合涂层刀具加工到45 min时,其后刀面磨损量仅为0.25 mm,这说明新型CVD金刚石复合涂层刀具高速铣削石墨时表现出良好的耐磨性和使用寿命,可以适应高性能各向同性石墨的加工需求。铣削加工试验还发现新型CVD金刚石复合涂层刀具加工的石墨表面质量在初期不如PCD刀具,但在更长时间加工情况下,其加工表面质量优于PCD刀具。

基于五轴平台的枞树型轮槽铣刀加工工艺分析

轮槽成型铣刀是加工汽轮机轮毂槽的重要工具,其结构复杂且加工困难。为提高加工效率和精度,以某型高速钢轮槽铣刀为例,提出基于五轴平台的加工工艺方法。使用UG软件基于五轴车铣复合机床规划粗加工刀具路径,并采用专用后置处理器生成数控加工程序,通过虚拟机床进行仿真验证;采用NUMROTO软件规划精加工路径,获得磨削NC代码并进行虚拟加工验证;进行实际切削验证,通过DOOSAN PUMA SMX2600ST车铣复合加工中心对刀具进行粗加工后,在SAACKE UWIF五轴工具磨床上完成刀具的精加工。实验结果证明,该工艺方法不仅能保证产品质量符合工艺设计要求,而且制造效率提高了20%。

基于GA-BP网络的数控机床动态误差预测研究

动态误差是高速高精度数控机床的重要误差源,针对实际加工过程中动态误差对工件精度影响较大的问题,提出了一种基于遗传算法优化的反向传播(GA-BP)神经网络以预测动态误差。首先,为了提高神经网络对动态误差的预测精度,从线性特征与非线性特征两方面对动态误差影响因素进行了深入分析,确定了神经网络输入输出参数;然后,采用了遗传算法对BP神经网络进行了优化,建立了动态误差模型,获得了最优网络学习参数,从而实现了对动态跟随误差的精准预测;之后,采用三次样条插值的方法对理想轨迹与实际轨迹之间的轮廓误差进行了计算,有效提高了轮廓误差估算精度;最后,采用了五轴数控机床进行了实验,对模型的有效性进行了验证。研究结果表明:所建神经网络模型可以精准预测机床反向越冲特性对轮廓误差的影响,各轴的动态误差预测精度为±3μm,复杂轨迹轮廓误差预测精度为±1.5μm。实验结果验证了所建模型的可靠性,为后续机床动态误差建模与控制研究提供了一定的参考价值。

高速钢大圆刀的热处理

高速钢大圆刀外径为200~420 mm、内径为145~254 mm、厚度为5~10 mm,不仅精度要求高,硬度要求高达62.5~64 HRC,大多采用盐浴炉淬火、回火。安徽嘉龙锋钢公司对外径为310 mm、内径为190 mm、厚5 mm的W6Mo5Cr4V2钢刀具在锻后退火和去应力退火后,在保护气氛炉中加热至1175~1185℃奥氏体化和氮气冷却,随后在台车式炉中540~550℃×3 h回火3次。结果表明:大圆刀的精度和硬度均符合要求。

基于高速钢对TC4钛合金的车削研究

文章针对TC4钛合金车削进行了探索性研究,并对TC4钛合金材料进行了分析。通过对刀具参数、切削参数、切削液的合理选择,以及多次车削试验和分析,确定了适用于TC4钛合金材料零件的高速钢车削加工方法,并验证了不同的参数在车削过程中对钛合金零件加工的影响。该研究为钛合金材料零件采用高速钢车削提供了可参考的相关依据,具有一定的应用价值。