中小型轴承零件硬车削工艺试验

以某型空心圆柱滚子、5302/01和3206/01中小型轴承零件为试验对象,通过硬车削加工工艺试验,分析了小批量中小型轴承零件精加工工序采用硬车削的工艺可行性和优势。     

硬车削进给量对加工表面应力的影响

以32216轴承内滚道和NJ3226X1滚子倒角的硬车削为试验对象,在不同的进给量下进行工艺试验,通过对加工后零件表面的应力测试,得出了切削进给量对硬车削后表面应力的影响规律。     

特大型圆锥滚子轴承内圈越程槽加工工艺改进

分析特大型圆锥滚子轴承内圈越程槽在目前工艺方法下存在的问题,为减小淬火变形的影响,将越程槽加工改为淬回火之后硬车,并增加附加回火;设计专用成形车刀。工艺改进后满足了特大型圆锥滚子轴承内圈的设计要求,越程槽加工质量提高,避免了缺陷的发生。     

精密硬车削代替磨削加工的试验研究

简要介绍了精密硬车削在轴承行业的应用,以7016AC/TAP4轴承套圈为试验对象,从试样的加工精度指标和表面完整性分析精密硬车削的特点,证明了在轴承零件加工中精密硬车削工艺代替磨削加工的可行性。     

基于正交试验法的CBN刀具车削表面粗糙度研究

基于CBN刀具的淬硬钢车削加工工艺,能否顺利替代传统的半精车、表面淬火后外圆磨加工工艺,其中重要的一点是新工艺技术必须能保证原有工艺技术的质量,还要求提高效率.在与企业的生产实际中采用正交试验法,找出基于CBN刀具加工影响表面粗糙度的主要因素,同时试验CBN刀具代替磨削加工的可行性.通过对试验数据的直观、方差分析,基于CBN刀具的硬车削加工工艺能满足产品加工的要求,且走刀量是影响表面粗糙度的主要因素.     

硬车削技术及其应用

分析了硬车削加工的特点、硬车削加工所需的条件以及硬车削技术在生产中的应用，并对其关键技术进行了探讨，指出硬车削技术是一种高效、洁净的工艺方法，具有广泛的应用前景。     

圆锥滚子轴承车削工艺的改进

1 问题的提出 以31318圆锥滚子轴承内圈外表面车加工工序为例,如图1所示.传统的车加工工艺为:由液压仿形车床一次装卡,上刀架纵向走刀车削外表面中的内外径和内滚道,下刀架成形刀车削小内外径和弯头刀向上走刀车削大端面,一次加工完成.     

精密硬车加工轴承套圈的表面完整性试验研究

针对磨削加工中套圈精密加工存在的不足,进行精密硬车削加工轴承套圈新工艺的开发,通过加工试验分析了精密硬车加工轴承套圈的表面完整性,探究了基准面平面度、刀具磨损量等工艺参数与加工精度的对应关系。基于精密硬车削套圈试样的表面粗糙度、沟道圆度、显微硬度、热损伤、金相组织、残余应力分布、加工效率等方面的研究,得出了精密硬车削可达到磨削加工精度的结论,且金相组织稳定,不易存在热损伤,具有可控的残余应力分布和较高的加工效率,有利于产业化生产高精密轴承。利用磁性卡盘装夹套圈,分析试样基准面平面度对精密硬车削套圈沟道圆度的影响,发现提高基准面平面度可以有效提高加工套圈的沟道圆度;分析了刀具磨损对硬车削套圈加工精度的影响,得出在精密加工阶段刀具磨损量是控制套圈圆度的重要监控工艺参数的结论。     

滚子制造工艺(5)

第六章 滚子毛坯的车 削成形 在整个滚子生产中,金属车削加工占有重要的地位。而车削加工又是金属切削加工中最基本的加工方式,所以,在学习滚子毛坯车削成形之前,应先熟习有关车削加工的基本知识(见套圈车削加工部分)。     

硬车削及其加工技术

介绍了硬车削加工的特点,硬车削加工所需的条件;分析了硬车削应用不广的原因,指出硬车削是一种高效洁净的工艺方法,具有广阔的应用前景。     

PCBN刀具超声振动车削45淬火钢的切削力与温度研究

应用正交试验设计，通过PCBN刀具对45淬火钢进行的普通硬车削与超声振动硬车削的对比试验，研究切削用量在两种切削方式下对切削力和切削温度的影响规律。试验结果表明：在合理的切削速度下，采用小进给量和小切削深度时，超声振动硬车削的切削力和切削温度要比相应的普通硬车削小得多。     

硬车削在滚动轴承套圈加工中的应用

分析硬车削的特点及加工条件,详细介绍了采用硬车削加工滚动轴承套圈时的机床设备、装卡夹具、刀具选择等参数的确定,采用正交试验法对试验中的切削速度、进给量和切削深度3参数的影响水平进行了分析,得出了以硬车削加工代替磨削加工的可行性。     

Analysis of tool wear and surface finish in hard turning

Hard turning is a profitable alternative to finish grinding. The ultimate aim of hard turning is to remove work piece material in a single cut rather than a lengthy grinding operation in order to reduce processing time, production cost, surface roughness, and setup time, and to remain competitive. In recent years, interrupted hard turning, which is the process of turning hardened parts with areas of interrupted surfaces, has also been encouraged. The process of hard turning offers many potential benefits compared to the conventional grinding operation. Additionally, tool wear, tool life, quality of surface turned, and amount of material removed are also predicted. In this analysis, 18 different machining conditions, with three different grades of polycrystalline cubic boron nitride (PCBN), cutting tool are considered. This paper describes the various characteristics in terms of component quality, tool life, tool wear, effects of individual parameters on tool life and material removal, and economics of operation. The newer solution, a hard turning operation, is performed on a lathe. In this study, the PCBN tool inserts are used with a WIDAX PT GNR 2525 M16 tool holder. The hardened material selected for hard turning is commercially available engine crank pin material.     

Performance improvement of hard turning with solid lubricants

Product quality is one of the most important criteria for the assessment of hard turning process. However, in view of the high temperatures developed in hard turning process, the surface quality deteriorates due to the tool wear. Because of the strict environmental restrictions on the use of cutting fluids, new cutting techniques are required to be investigated to reduce the tool wear. In the present work, the use of solid lubricants during hard turning has been explored while machining bearing steel with mixed ceramic inserts at different cutting conditions and tool geometry. Results show considerable improvement in the surface finish with the use of solid lubricants. Due to the presence of solid lubricants, there is a decrease of surface roughness values from 8 to 15% as compared to dry hard turning.     

Modeling and analyzing the effects of air-cooled turning on the machinability of Ti–6Al–4V titanium alloy using the cold air gun coolant system

This study provides the mathematical models for modeling and analyzing the effects of air-cooling on the machinability of Ti–6Al–4V titanium alloy in the hard turning process. A cold air gun coolant system was used in the experiments and produced a jet of compressed cold air for cooling the cutting process. The air-cooling process seems to be a good environment friendly option for the hard turning. In this experimental investigation, the cutting speed, feed rate and cutting depth were chosen as the numerical factor; the cooling method was regarded as the categorical factor. An experimental plan of a four-factor (three numerical plus one categorical) D-optimal design based on the response surface methodology (RSM) was employed to carry out the experimental study. The mathematical models based on the RSM were proposed for modeling and analyzing the cutting temperature and surface roughness in the hard turning process under the dry cutting process and air-cooling process. Tool wear and chip formation during the cutting process were also studied. The compressed cooling air in the gas form presents better penetration of the lubricant to the cutting zone than any conventional coolants in the cutting process do. Results show that the air-cooling significantly provides lower cutting temperature, reduces the tool wear, and produces the best machined surface. The machinability performance of hard turning Ti–6Al–4V titanium alloy on the application of air-cooling is better than the application of dry cutting process. This air-cooling cutting process easily produces the wrinkled and breaking chips. Consequently, the air-cooled cutting process offers the attractive alternative of the dry cutting in the hard turning process.     

Surface Integrity and Machineability in Intermittent Hard Turning

Despite the large amount of research on hard turning, there are few results on intermittent hard turning. In this paper, the feasibility of internal intermittent hard turning has been investigated. First, the cutting tools with different cubic boron nitride (CBN) contents were evaluated, based on machineability: tool wear, surface roughness, and cutting forces. In the case of intermittent turning, low CBN content tools had better machineability than high CBN content tools. The depth of the machining damaged layer and the magnitude and distribution of residual stress were evaluated. The experimental results showed that intermittent hard turning can produce surface integrity which is good enough for replacing the grinding process.     

Experimental study and evaluation methodology on hard surface integrity

The Taguchi method is adopted experimentally to investigate the surface integrity (surface roughness, residual stress, and thermal damage layer) of hardened bearing steel in hard dry turning, and the validation experiments are consequently performed. It was revealed that the value and effect sequence of optimal hard turning parameter varies with different objectives of surface integrity. However, it is quite difficult to select or determine the optimal combination of hard turning parameters. A hard-turned component performance, which reflects an integrated impact of surface integrity, should be fully recognized to resolve the inherent conflict in the selection process. Based on it, an evaluation methodology composed of four steps is proposed that surface integrity should be evaluated by the service/fatigue life of hard-turned components and therefore turning parameters. It bears significance for super-finish hard turning further application in respect that it provides an integrated approach for hard turning parameter optimization to achieve a superior surface integrity. Funded by the Ministry of Education of China- “985” of international cooperation project “Clean Manufacturing Technology”.     

CUTTING DISTURBANCES INFLUENCED BY VARIATIONS IN CONTACT SURFACE GEOMETRY

The significant cutting disturbances appearing in hard turning processes cause shifting of the process dynamics. Therefore, in this paper the turning process is evaluated by radial force variation analysis, as a function of depth of cut, tool nose radius and effective lead edge angle, through static and dynamic indicators. The tool/workpiece contact zone is, in the case of hard turning, mostly limited within the tool nose radius region. Therefore in this paper, geometry of the tool/workpiece contact line is analyzed. The depth of cut is calculated as a geometric difference of prior and instantaneous tool pass profiles. The calculated values of the depth of cut are time dependant, and can vary by 60%. Various process monitoring techniques have been used to identify and confirm these variations, as well as quantify the level of process stability. The results obtained confirm the assumption that effective lead edge angle and radial force are influenced by depth of cut, feed rate and tool nose radius. Additionally, it is shown that low values of depth of cut and geometry of prior pass-machined surface valleys shift the hard turning process to a dynamically more sensitive level as compared the case of soft machining.     

CBN tool wear in hard turning: a survey on research progresses

Direct machining steel parts at a hardened state, known as hard turning, offers a number of potential benefits over traditional grinding in some applications. In addition, hard turning has several unique process characteristics, e.g., segmented chip formation and microstructural alterations at the machined surfaces, fundamentally different from conventional turning. Hard turning is, therefore, of a great interest to both the manufacturing industry and research community. Development of superhard materials such as polycrystalline cubic boron nitride (known as CBN) has been a key to enabling hard turning technology. A significant pool of CBN tool wear studies has been surveyed, in an attempt to achieve better processing and tooling applications, and discussed from the tool wear pattern and mechanism perspectives. Although various tool wear mechanisms, or a combination of several, coexist and dominate in CBN turning of hardened steels, it has been suggested that abrasion, adhesion (possibly complicated by tribochemical interactions), and diffusion may primarily govern the CBN tool wear in hard turning. Further, wear rate modeling including one approach developed in a recent study, on both crater and flank wear, is discussed as well. In conclusion, a summary of the CBN tool wear survey and the future work are outlined.