中国CBN磨具的研发历程与技术发展趋势

本文回顾我国CBN磨具制造技术与产品的主要研发历程,以总结CBN磨具在结合剂体系、加工技术、品种规格等方面的主要发展特征。从市场结构和制造技术等方面对其未来发展趋势进行分析预测,并展望未来轴承行业等重点领域用CBN磨具及难加工材料磨削用CBN磨具的发展。      

Minimization of effect of CBN wheel wear on ground gear errors

Resistance to wear of CBN grinding wheels is much higher than that of conventional (Al₂O₃) wheels. However, CBN grinding wheels are seldom used in gear grinding, when production scale is small, due to the difficulty in truing. Moreover, wear of the grinding wheel greatly affects the accuracy of tooth trace, in most cases. Considering this problem, the authors proposed new processes in which the accuracy of the tooth trace and tooth profile was hardly affected by wear of the wheel. While grinding was performed using a conventional method, a concave tooth-trace error of about 2 μm occurred after grinding only 30 teeth. In one of the proposed methods, the concave tooth trace error never occurred even when 2000 teeth were ground by the same wheel. In the third method, the CBN layer is effectively used for gear grinding by giving an additional motion which is independent of the tooth profile generating motion.     

Development of a patterning system for vitrified CBN wheels based on modal analysis

One of the alternatives under development by industry to reduce tailpipe emissions in internal combustion engines is the texturing of the crankshaft bearings using patterned grinding wheels. As modern industrial grinding solutions for forged crankshafts are based on vitrified CBN wheels, a new approach is needed for rotary dressing patterning. This paper describes the development of patterning system for vitrified CBN wheels based on modal vibration analysis. Aspects related to the device design, modelling and simulation of the texturing process are discussed in the paper. The obtained results reported in this paper indicate a high potential for industrial application.     

Analysis of the different forms of application and types of cutting fluid used in plunge cylindrical grinding using conventional and superabrasive CBN grinding wheels

The work reported here involved an investigation into the grinding process, one of the last finishing processes carried out on a production line. Although several input parameters are involved in this process, attention today focuses strongly on the form and amount of cutting fluid employed, since these substances may be seriously pernicious to human health and to the environment, and involve high purchasing and maintenance costs when utilized and stored incorrectly. The type and amount of cutting fluid used directly affect some of the main output variables of the grinding process which are analyzed here, such as tangential cutting force, specific grinding energy, acoustic emission, diametrical wear, roughness, residual stress and scanning electron microscopy. To analyze the influence of these variables, an optimised fluid application methodology was developed (involving rounded 5, 4 and 3 mm diameter nozzles and high fluid application pressures) to reduce the amount of fluid used in the grinding process and improve its performance in comparison with the conventional fluid application method (of diffuser nozzles and lower fluid application pressure). To this end, two types of cutting fluid (a 5% synthetic emulsion and neat oil) and two abrasive tools (an aluminium oxide and a superabrasive CBN grinding wheel) were used. The results revealed that, in every situation, the optimised application of cutting fluid significantly improved the efficiency of the process, particularly the combined use of neat oil and CBN grinding wheel.     

Precision grinding using CBN wheels

The paper systematically reviews experimental research on the performance of cubic boron nitride (CBN) grinding wheels and discusses advantages and difficulties experienced in the application of CBN wheels particularly for internal grinding with fine-grain wheels.The hardness of CBN grains potentially increases re-dress life and improves dimensional stability. The problem is that increased re-dress life increases the importance of avoiding wheel loading, particularly for small-grain wheels. This paper highlights the importance of touch dressing for improved dimensional stability and other operational techniques to maintain an open surface topography of the wheel. The paper also demonstrates the benefit of an open-structured small-grain CBN wheel for precision grinding. Effects on grinding temperature are also illustrated.     

Improved monolayer CBN wheel for load free grinding

A galvanically bonded wheel made of a monolayer of CBN grits may not always ensure free cutting action when a large volume of chips is to be handled because of the fact that about two thirds or more of the grit height has to be covered by the matrix for effective anchorage. The present study shows that the problem of chip accomodation during grinding is further aggravated when the CBN wheel has some surface defect like growth of the galvanic layer in the space between the grits. In order to utilize more effectively the extraordinary capability of CBN grits, a new kind of monolayer CBN wheel has been developed, using a special bonding technique (patent pending). This technique keeps the level of the bond material low but sufficient to hold the grits during grinding. Performance of this CBN wheel relative to that of a galvanically bonded wheel, with particular reference to its grinding capability while grinding unhardened 100 Cr6 steel is discussed in this paper.     

滑动齿套拨叉槽的立方氮化硼刀具切削工艺试验研究

为了确定硬态切削代替磨削加工滑动齿套拨叉槽时各参数对其表面质量的影响,采用立方氮化硼刀具对20CrMnTi棒料进行切削,利用正交试验法对加工表面粗糙度进行了直观分析和方差分析,得出切削速度、进给量、背吃刀量对拨叉槽表面粗糙度的影响规律,并给出拨叉槽加工时合理的切削用量;同时也对加工过程中刀具的磨损进行分析,为滑动齿套拨叉槽的立方氮化硼切削工艺参数的选取提供了依据。     

Internal mirror grinding with a metal/metal–resin bonded abrasive wheel

Precision internal cylindrical surfaces are increasingly utilized in industries where highly efficient methods to fabricate such surfaces are of great importance. Presently, several processes usually performed on different machines are used successively to achieve a mirror finish. In this paper, a novel method is presented to accomplish roughing and finishing processes on one machine, using super abrasive cast–iron–bond CBN (CIB–CBN) wheels and metal–resin–bond CBN (MRB–CBN) wheels. Two dressing methods, electrolytic interval dressing and electrolytic in-process dressing (ELID), are also developed for these wheels respectively. The CIB–CBN wheel is trued by an on-machine electrical discharge truer (EDT) and dressed at intervals with a pipe-shape electrode; the MRB–CBN wheel is dressed in process, in which no specific dressing electrode is utilized, instead the conductive workpiece acts as a dressing electrode. Precision grinding has been carried out on an ordinary grinder with an attachment for internal cylindrical grinding. Wheels of #325, #1200, #2000, and #4000 grit sizes have been applied in the process to obtain mirror surfaces.     

Design and application of CBN shape grinding wheel for gears

In the field of gear precision manufacturing, the CBN shape grinding technique is of great importance. In this research, a mathematical model for the profile of CBN grinding wheel base body has been developed based on the theory of gear engagement; the modification of the gear shape is introduced into the design of the CBN grinding wheel. Biarc segments are used to approximate the theoretical profile. Approximation deviation can be controlled within prescribed tolerance under optimized conditions. A series of wheels were made to ascertain the validity and effectiveness of the presented method, the final gear precision reaches the fifth class of GB10095-88 (China).     

Continuous generating grinding—Tooth root machining and use of CBN-tools

Profile accuracy, no burning and residual compressive stresses at the tooth root fillet are required for the durability of highly stressed gears. This paper reveals the challenges for continuous generating grinding with corundum and CBN. For this purpose, material removal simulations and experimental investigations were carried out to gain knowledge of the tool–workpiece contact conditions. The potential of CBN tools was analysed due to the fact that the mechanical loads at the grinding worm tip result in high profile wear of the corundum tools. In this context, especially the interrelationship between the dressing strategy and the workpiece quality was investigated in detail.     

Turning of interrupted and continuous hardened steel surfaces using ceramic and CBN cutting tools

In the machining of hardened steel surfaces, turning instead of grinding has been employed increasingly due to several advantages it offers, such as flexibility and the possibility of dry cutting. The main tool materials used for this purpose are CBN and ceramic due to their high hardness and, in the case of some grades of these materials, high chemical stability with iron. However, when interrupted surfaces are turned, the tool requires not only these properties but also sufficient toughness to resist impacts against workpiece interruptions. Therefore, the main goal of this work is to compare CBN and ceramic tools in continuous and interrupted cutting. To this end, several turning experiments were carried out on continuous surfaces (in this case, CBN with an added ceramic phase and a mixed ceramic were compared, due to their high chemical stability and hardness) and on interrupted surfaces (here, a high CBN content and a SiC-reinforced ceramic were compared due to their good ability to withstand impacts), applying different cutting speeds. The main conclusions of this work were that in both continuous and interrupted cutting, the CBN tools exhibited a much better performance with respect to both tool life and workpiece surface roughness than the ceramic tools.     

GCr15钢平面磨削力仿真分析与实验研究

目的 对不同磨削工艺参数下的平面磨削力进行预测,对磨削机理进行研究,进而控制磨削加工质量。方法 考虑CBN砂轮表面磨粒形状的多样性、姿态的多样性和空间分布的随机性,建立CBN砂轮模型,对GCr15材料模型进行有限元砂轮磨削仿真。同时使用CBN砂轮,采用不同的工件进给速度对GCr15进行单因素平面磨削实验,使用三坐标测力仪测量不同磨削参数下的磨削力。结果 建立的仿真砂轮模型的表面形貌与真实砂轮接近,仿真砂轮上的磨粒出刃高度均服从正态分布,与实际砂轮一致。对比随机多面体磨粒模型和真实CBN磨粒照片,两者形貌相似。磨削力实验和仿真结果表明,工件进给速度由3 m/min增大到18 m/min时,磨削力逐渐增大,仿真所得法向磨削力最大误差远小于切向磨削力。结论 实验结果与仿真结果具有一致性,证明了砂轮磨削有限元仿真模型可用于磨削力预测。因为仿真中无法考虑实际砂轮尺寸和砂轮表面结合剂对磨削的影响,结果具有一定误差,仿真的准确性有待进一步提高。研究结果为使用有限元方法研究磨削机理和控制磨削加工质量提供了思路。     

高速立方氮化硼砂轮与绿色制造

以磨削加工汽车发动机凸轮轴、曲轴为例,对陶瓷CBN砂轮与普通刚玉砂轮进行了加工效果对比。结果表明:高速陶瓷CBN砂轮的耐用度是普通陶瓷刚玉砂轮的100倍,寿命是普通砂轮的的44.4倍,而原材料消耗仅为其1/56;加工相同的工件数量,使用刚玉砂轮进行加工,磨料消耗是高速CBN砂轮的400余倍;采用高速陶瓷CBN砂轮代替刚玉砂轮可提高生产效率30%以上,综合生产成本比刚玉砂轮磨削降低60%。高速CBN砂轮具有高效率、高精度、低磨削成本,低环境污染的技术优势,其代表了当今世界磨具产品发展的一个主要方向,是实现绿色加工目标的有效手段。     

Influence of the type of coolant lubricant in grinding with CBN tools

Oil and emulsion are two main grinding coolant lubricants (CLs) used in grinding processes with CBN tools. A comparison of these two CLs was performed as part of the long systematic research made by KSF. The comparison criteria presented in this paper are grinding forces and G-ratio. The results show that oil presents better function almost in every case for the selected grinding parameters and workpiece. However, it should be noted that the results could probably be different with other types of oil and emulsion.     

齿轮成形磨削能耗与表面粗糙度研究

齿轮成形磨削的能耗研究对于高精度齿轮的低碳制造具有重要意义.从数控成形磨齿机床的部件层面出发,分析齿轮成形磨削的能耗组成部分;基于磨削功率和材料切除率,建立齿轮成形磨削的净能耗密度模型;通过齿轮成形磨削试验发现,增加磨削能耗,会使表面粗糙度减小,但随着磨削能耗的持续增加,表面粗糙度减小幅度有限.研究结果为齿轮成形磨削的能耗与加工质量协同优化控制奠定了理论基础.     

改变立方氮化硼磨具修整方向的研究

树脂结合剂CBN磨具的磨削性能取决于磨具的修整效果,磨具修整的效果关键在于其修整方向。本丈通过不同的修整方向的对比试验和磨削试验,分析用不同的修整角所修整出的磨具表面,找出了CBN磨具修整的最佳方法。     

THERMAL STUDY ON THE GRINDING OF GRANITE WITH SUPERABRASIVE TOOLS

Diamondabrasivetoolsareextensivelyusedintheprocessingofstone ,frominitialsawingtofinalfinishing .Infact,abrasiveprocessingofgraniteandmarbleforconstructionisthemostimportantfactorintheconsumptionofindustrialdiamond .Duringgrinding ,diamondabrasivegritsonthewheelsurfaceinteractwiththeworkpieceanddothecutting .Theenergyexpendedbythegrindingprocesscanleadtoelevatedtemperaturesatthegrindingzone ,whichmaycausethermaldamagetotheworkpieceandpromotewheelwear.Accordinglyextensivepastresearchhasbeenconc…     

Thermal Analysis of Grinding

Thermal damage is one of the main limitations of the grinding process, so it is important to understand the factors which affect grinding temperatures. This paper presents an overview of analytical methods to calculate grinding temperatures and their effect on thermal damage. The general analytical approach consists of modeling the grinding zone as a heat source which moves along the workpiece surface. A critical factor for calculating grinding temperatures is the energy partition, which is the fraction of the grinding energy transported as heat to the workpiece at the grinding zone. For shallow cut grinding with conventional abrasive wheels, the energy partition is typically 60%-85%. However for creep-feed grinding with slow workspeeds and large depths of cut, the energy partition is only about 5%. Such low energy partitions are attributed to cooling by the fluid at the grinding zone. Heat conduction to the grains can also reduce the energy partition especially with CBN abrasives which have high thermal conductivity. For High Efficiency Deep Grinding (HEDG) using CBN wheels with large depths of cut and fast workspeeds, preheated material ahead of the grinding zone is removed together with the chips, thereby lowering the temperature on the finished surface. Analytical models have been developed which take all of these effects into account. Much more research is needed to better understand and quantify how grinding temperatures affect the surface integrity of the finished workpiece.     

单颗钎焊金刚石磨粒磨损试验研究

采用单颗磨粒试验方法,以碳钢碟轮为修整工具,研究金刚石和CBN磨粒修整过程中的磨损特征。结果表明:砂轮和修整碟轮的相对速度对金刚石磨粒的磨损有重要影响;相对速度为51.9 m/s时,金刚石磨粒的磨损高度为50.1 μm;相对速度为17.3 m/s时,金刚石磨粒的磨损高度显著减小,为19.5 μm。通过相同条件下金刚石与CBN磨粒的磨损特征对比,表明金刚石磨粒在磨损过程中同碟轮之间发生化学作用,加速金刚石磨粒的磨损;对试验后金刚石磨粒进行拉曼光谱分析,并未检测到石墨物质。      

Evaluation of superabrasive grinding points for the machining of hardened steel

Small diameter grinding points offer greater flexibility for machining free-form contours compared to traditional grinding wheels, despite fewer effective cutting edges. The paper evaluates the influence of grit size (B32, B46, B76), feed rate (125, 250 mm/min) and depth of cut (20, 40 μm) when machining D2 tool steel using electroplated CBN grinding points. Highest G-ratios (～2441) were obtained using B32 tools with corresponding workpiece surface roughness (Ra) of ～0.8 μm after ～6000 mm³ material removed, due to the greater number of effective cutting edges. Attritious wear was the primary wear mechanism although material loading was observed with B76 tools.