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.     

Assessment of vitrified CBN wheels for precision grinding

Methods of measuring topographical features of grinding wheels are reviewed. Each technique has advantages and limitations for resolution, measuring depth, ease of application, data analysis and interpretation. Results obtained vary according to the method and instrument employed. Advantages and difficulties experienced with different techniques are discussed. Different replication techniques and materials are compared and suggestions made. A set of parameters that describe the wheel and grain characteristics is defined. Experimental studies with grinding wheels having different structures are carried out in terms of observations and measurements of changes in wheel topography. Experimental results are analysed and discussed in relation to theoretical understanding of abrasive wear and loading.     

Assessment method of cutting ability of CBN grinding wheels

In the paper authors described a method of CBN grinding wheel cutting ability evaluation and research results achieved with this method during grinding process. Research results, which allowed for verification of the method (e.g. measurements of grinding force components, surface roughness and waviness parameters and stress level in surface layer) were also presented.     

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.     

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.     

CBN高效深磨砂轮主轴的建模分析与实验研究

基于对CBN端面砂轮的研究,提出一种高效率深度端面磨削的砂轮主轴系统.主轴单元的静态特征和影响因素分析了理论计算和建模仿真分析,并验证主轴结构和参数的合理性.基于模态分析理论,砂轮主轴系统的模态测试是由锤击方法,并得到了前6阶模态参数和分析结果.结果表明:该磨削主轴系统满足了高效深磨技术要求.最后,研磨应用开发测试平台应用了磨削主轴单元和一些实验来完成高效深磨的研究.对Cr12Mo1V1工件在砂轮转速为80 ～ 100 m/s时进行了端面磨削实验,其结果为:切削深度0.175～0.5 mm,表面粗糙度0.8～3.2 μm以及圆柱度5-10 μm.     

Improving minimum quantity lubrication in CBN grinding using compressed air wheel cleaning

The application of minimum quantity lubrication (MQL) in grinding has emerged as an alternative for reducing the abundant flow of cutting fluids, thus achieving cleaner production. Although considered an innovative technique in grinding operations, its widespread application is hindered due primarily to the high heat generation and wheel pore clogging caused by machined chips, harming the final product quality and increasing tool wear on the machine. This study sought to improve MQL use in grinding. In addition to the conventional MQL injected at the wheel/workpiece interface, a compressed air jet was used to clean the mixture of MQL oil and machined chips from clogged wheel pores. Experiments were conducted using external cylindrical plunge grinding on AISI 4340 quenched and tempered steel, and a vitrified cubic boron nitrite (CBN) wheel. The cooling-lubrication methods employed were the conventional flood coolant application, MQL (without cleaning), and MQL with a cleaning jet directed at the wheel surface at different angles of incidence. The main goal of these experiments was to verify the viability of replacing the traditional abundant flow of cutting fluid with MQL and wheel cleaning. The analyses were conducted by measuring the following output variables of the process: workpiece surface roughness and roundness errors, diametrical wheel wear, acoustic emission generated by the process, and metallographic images of the ground surface and subsurface. Results show the positive effects of implementing the cleaning jet technique as a technological improvement of minimum quantity lubrication in grinding in order to reduce the usage of cutting fluids. The MQL technique with cleaning compressed air jet, for a specific angle of incidence (30°), proved to be extremely efficient in the improvement of the surface quality and accurate workpiece shape; it also reduced wheel wear when compared to the other cooling-lubrication methods that were tested (without a cleaning jet).     

Power and Wheel Wear for Grinding Nickel Alloy with Plated CBN Wheels

Electroplated CBN grinding wheels are manufactured with a single layer of abrasive grains. The grinding performance of these plated wheels changes significantly as the wheel wears down. The present investigation was undertaken to understand the transient grinding behavior with electroplated CBN wheels in order to provide a logical basis for process control. In this paper, particular attention is directed to the effect of wheel wear and operating parameters on grinding of a nickel alloy. Wheels were worn to various stages and then used to perform grinding tests under various grinding conditions to measure grinding forces and power and to produce ground specimens. Based on models for grinding with conventional aluminum oxide wheels, a power model for grinding of a nickel alloy with plated CBN wheels was established and validated. Microscopic observations of the ground specimens reveal that thermal damage in the form of a White Etch Layer (WEL) appears only when grinding with a worn wheel under conditions that lead to high temperatures.     

Factors Affecting Grinding Performance with Electroplated CBN Wheels

An experimental investigation was conducted to evaluate the effect of CBN crystal characteristics and plating thickness on the performance of electroplated CBN wheels. Wheels containing tougher CBN crystals generally exhibited less wear and a higher G-ratio, and also required less power. Furthermore, contrary to expectations, less wear and higher G-ratio were also obtained for wheels with a thinner layer of nickel plating despite an increased tendency for large-scale crystal loss. This would indicate that the overall wheel wear depends more on crystal exposure than on active grain density, which could facilitate chip removal and grinding fluid access. Extended grinding tests up to wheel failure ascertain the improved grinding performance with tougher crystals and thinner electroplated layers.     

An Investigation of Grinding with Electroplated CBN Wheels

Grinding of hardened bearing steel with electroplated CBN wheels was Investigated with particular attention to how the wear of the abrasive grains affects the wheel topography and grinding performance during the wheel ire. Power, surface roughness, and wheel topography data were obtained throughout the wheel life for internal cylindrical grinding. Dulling of CBN gratis by attrition was found to cause an increase in the grinding power, but the degree of dulling was restricted mainly by grain fracture and also by grain pullout. Grain fracture and pullout had a much smaller effect on the progressive increase in active grain density, which caused the surface roughness to progressively decrease. Wheel failure tended to occur by stripping of the abrasive layer when the radial wear reached about 70% - 60% of the grain dimension     

精密研磨高压共轨柴油发动机喷油嘴中间体的CBN磨盘

制备了微粉粒度的陶瓷结合剂CBN磨盘,并将其用于柴油发动机喷油嘴中间体精密端面磨削。在制备陶瓷CBN磨盘过程中,辅助磨料含量、结合剂质量分数对磨盘性能有较大影响,其中结合剂质量分数影响最大。结合剂在650~720℃烧成时,制得的陶瓷CBN磨盘结构致密、组织均匀,抗折强度达140 MPa。在实际磨削应用中,研究了磨削盘数对磨削压力和效率的影响。结果表明:单盘磨削时间与机床压力随磨削盘数的变化趋势基本一致,且磨削100Cr6轴承钢工件的表面精度和磨削效率均满足要求。     

一种新型超精磨金属陶瓷CBN砂轮的研究

通过考察不同因素对砂轮锋利性、寿命及加工工件表面粗糙度的影响,优选出了端面超精磨CBN砂轮的制备工艺。通过对比实验,得出最优配比如下:CBN磨料的粒径优选添加40μm,陶瓷空心球的粒度优选添加240目,其添加量优选体积分数为20%,金属粉的优选体积分数为9%。该配方制备的CBN砂轮的锋利性、寿命及加工工件的表面粗糙度均达到了较好的效果。     

不同CBN砂轮高速加工PTMCs的磨削性能对比

为分析CBN砂轮高速磨削颗粒增强钛基复合材料(particulate reinforced titanium matrix composites,PTMCs)的磨削性能,采用3种CBN砂轮开展PTMCs的高速磨削试验,对比研究其磨削力、温度、表面粗糙度及表面形貌。结果表明:相对陶瓷砂轮,钎焊砂轮的法向磨削力减小16.2%～40.4%、切向力减小25.2%～44.4%,磨削温度降低了26.0%～74.3%;相对电镀砂轮,钎焊砂轮的法向磨削力减小7.1%～31.1%、切向力减小23.3%～31.1%,磨削温度降低了14.5%～58.9%;钎焊砂轮在加工中表现出了最低的磨削力和温度,获得了最低的表面粗糙度和最好的表面质量,表面粗糙度可以达到0.60～0.77 μm。因此,在高速磨削PTMCs时,钎焊砂轮更具优势。      

Model-based manufacturing and application of metal-bonded grinding wheels

The tool properties of grinding wheels can vary in a wide range due to the variety of processes. The properties, in turn, affect the grinding process and the grinding results. Understanding the interdependencies from the initial manufacturing to the final grinding results is the key to achieve the target-oriented generation of the grinding wheel properties for the grinding task at hand. This paper presents a novel approach to model the interdependencies between the manufacturing of bronze-bonded grinding wheels and the resulting grinding behaviour. The manufacturing steps are described with sub models in order to forecast properties and application behaviour.     

CBN砂轮在航空发动机零件高效精密加工中的应用

分析了航空发动机零件磨削加工的特点及现状,综述了砂轮在航空领域高效精密磨削中的研究进展,介绍了CBN砂轮制备技术的突破,指出了CBN砂轮在航空发动机零件的高效精密加工中具有广阔的应用前景,并提出了推广应用中存在的问题。     

Cycle optimization in cam-lobe grinding for high productivity

Cycle optimization in cam-lobe grinding is presented for improving productivity. It includes novel modeling of the instantaneous geometry, kinematics and temperature for any workpiece form. A technical assessment of three process-control strategies – (1) constant specific material removal rate, (2) constant power, and (3) constant temperature – is made. The constant-temperature process provides the shortest cycle time without thermal damage. A detailed analysis of this process considers the role of machine limitations, including maximum speed, acceleration, and jerk, as well as the cam-lobe geometrical effects. The optimization results are validated by grinding tests in an actual production line.     

陶瓷结合剂CBN砂轮在凸轮轴加工中的应用

本文介绍了陶瓷结合剂立方氮化硼(CBN)砂轮的优越的磨削性能,总结了应用经验.采用郑州磨料磨具磨削研究所研制的陶瓷结合剂CBN砂轮在我厂进口的Landis数控高速磨床上进行了磨削冷激铸铁凸轮轴应用性试验.试验结果表明,加工工件粗糙度、砂轮的耐用度和寿命均达到进口CBN砂轮的水平.     

高速陶瓷CBN砂轮贴片的实验研究

本文从影响高速CBN砂轮陶瓷贴片性能的因素入手,凭借扫描电镜、差热分析仪等先进精密仪器对磨料进行了常温性能、差热分析、焙烧处理（870℃）分析;同时对陶瓷结合剂配成原理、比例和性能进行了试验探讨;利用ANSYS软件对陶瓷砂轮贴片的尺寸大小进行了优化分析;最后,利用超高速点磨削试验台对焙烧好的砂轮贴片进行了磨削性能实验。实验表明：研发的低温高强陶瓷结合剂,该配方结合剂的耐火度890℃,抗折强度达到了60.13 MPa;烧制的陶瓷贴片在小进给、小切深、超高速磨削下,表面粗糙度Ra值为0.002 mm左右。     

Engineered wheels for grinding of optical glass

This paper focuses on the evaluation of topographical parameters characterizing the influence on the behaviour and finally the process results by applying engineered diamond wheels in machining hard and brittle materials. Here, coarse-grained, single-layered diamond grinding wheels with electroplated abrasive layers and active-brazed, defined grain pattern have been dressed by a special conditioning process and used in precision grinding experiments on optical glass. The characterization of the abrasive layer topography was done by two topographical parameters, the specific total grain plateau area A′_G,total and the average grain cutting edge width b_G,a, determined by 3D-profilometry of replicated abrasive layers after each dressing step.