An experimental study on the grinding of alumina with a monolayer brazed diamond wheel

A monolayer diamond grinding wheel was fabricated by brazing in vacuum. The wheel was then used to grind alumina at three different grinding speeds. The horizontal and vertical grinding forces, and the grinding temperatures were measured during grinding. SEM observations were made for the ground workpiece surfaces. The influences of the peripheral wheel speed on the grinding forces, specific grinding energy and grinding temperatures were analyzed under different combinations of depth of cut and workpiece velocity. The dependence of the average grinding force per grain and specific grinding energy on the maximum undeformed chip thickness was discussed respectively. It was found that an increase in the peripheral wheel speed reduced grinding force, but increased force ratio, specific grinding energy, and grinding temperature.     

Effects of Abrasive Types on Grinding of Chopped Strand Mat Glass Fiber-Reinforced Polymer Composite Laminates

A grindability study of chopped strand mat glass fiber reinforced polymer laminates (CSM GFRP) has been carried out to evaluate the effects of abrasive types on grinding force ratio and area roughness at varying grinding parameters such as speed, feed and depth of cut. Performances of alumina (Al₂O₃) and cubic boron nitride (CBN) wheels were compared. Both wheels delivered the maximum grinding force ratios at low speed, high feed and low depth of cut. Alumina wheel produced smoother surface when grinding at low speed, low feed and high depth of cut. CBN wheel, on the other hand, gave smoother surface at high feed and low depth of cut conditions, regardless of speed. With CBN wheel, it is likely that a single grinding condition exists that maximizes grinding force ratio and minimizes area roughness. The findings indicate that CBN wheel exhibited higher grinding force ratio than alumina grinding wheel in general. CBN grinding wheel also outperformed alumina grinding wheel by producing smoother ground surface in most cases.     

Temperature control in CBN grinding

The main advantage of CBN grinding wheels is the long wheel life owing to the hardness of the CBN abrasive. Recent research has confirmed another advantage of CBN, which is cooler grinding. The new research allows the temperature in grinding to be predicted based on experimentally validated CBN thermal properties. This work also provides for in-process prevention of thermal damage in grinding. A well-documented feature of CBN grinding is the reduced risk of thermal damage to the workpiece. This advantage can allow a marked increase in removal rate whilst maintaining surface quality of the component compared to grinding with conventional abrasives such as aluminium oxide. The reduced risk of thermal damage in CBN grinding is sometimes attributed to the lower grinding specific energies. While lower specific energies when achieved are an advantage, this explanation ignores a fundamental advantage of the CBN abrasive. The experimental investigation has shown that a major advantage of CBN grinding is that a substantially lower proportion of the total grinding energy enters the workpiece compared to grinding with alumina wheels. The results further indicate that the effective thermal conductivity of CBN grains is considerably lower than its reported theoretical value of 1300 W(mK)^–1.     

A study on the surface grinding of 2D C/SiC composites

This paper aims at studying the machinability of 2D C/SiC composite with 0°/90° woven carbon fibers using a resin bond diamond grinding wheel. The effects of grinding parameters on the grinding force, force ratio, specific grinding energy, surface topography, surface roughness, and grinding chips were investigated. And the grinding mechanism of the 2D C/SiC composite was discussed by analyzing the chip components and material removal characteristics. The results indicate that the grinding force and surface roughness increase with the increase of feeding speed and depth of cut, while decrease with the increase of wheel speed. The force ratio F _n /F _t and the specific grinding energy of 2D C/SiC composite were lower than those of conventional ceramics under the defined experimental conditions. Additionally, the grinding chips were composed of carbon powder, carbon fiber fragments, and SiC matrix debris. It can be deduced that the dominant removal mechanism of the 2D C/SiC composite was brittle fracture mode during grinding process.     

高速精密磨削9CrWMn冷作模具钢的磨削力和比磨削能

分析了高速精密磨削9CrWMn冷作模具钢的机理,采用DEFORM软件对高速磨削模具钢9CrWMn过程进行了磨削力仿真。使用高精密高速平面磨床对模具钢9CrWMn进行了高速精密磨削试验,并在线测量了多种工况下的磨削力。结果表明:在其他两组工艺参数不变时,随着工件进给速度增加,磨削力特别是法向磨削力会增大近45%;法向磨削力和切向磨削力随着砂轮的线速度上升而下降,法向磨削力下降近33%;磨削深度对磨削力影响较大,大的磨削深度对法向磨削力的影响尤其显著,可使法向磨削力增大近100%。分析了磨削工艺参数对比磨削能的影响规律,结果显示:随着磨削深度和工件进给速度的增大,比磨削能呈比较明显的下降趋势,符合磨削加工中的尺寸效应;随着砂轮线速度的增大,比磨削能呈上升趋势。最后,对高速磨削前后工件表面的微观形貌进行了对比分析,磨削力试验结果和仿真理论分析相一致。     

MODELING OF DRESSING FORCES DURING ROTARY DIAMOND CUP DRESSING OF VITRIFIED CBN GRINDING WHEELS

This paper presents a mathematical model of dressing of vitrified CBN grinding wheels by a diamond cup dresser. It predicts the dressing forces during rotary diamond cup dressing of vitrified CBN grinding wheels. This model is based on the fracture of abrasive grits, the fracture of the bond and the contact forces between dresser and grinding wheel. It considers the kinematical influences and in particular speed ratio and overlap factor during the dressing process. A Weibull distribution is used to predict the probability of bond fracture and also the collision number between the diamond grits of a rotating dresser and the CBN grits. This model is validated by experimental results. The theoretical modeling values agree reasonably well with the experimental results. On the basis of this model the effect of different cup dressing parameters on dressing forces is theoretically discussed with the aim of establishing appropriate dressing process configurations. Furthermore the presented model provides a basis for further prediction of wheel topography and the grinding process.     

45钢高效深磨磨削力的实验研究

采用CBN砂轮,在砂轮线速度为90～210m/s的磨削条件下,对45钢进行了高效深磨实验.分析了不同工况对磨削力的影响.实验表明,在高效深磨过程中,提高砂轮线速度使磨削力减小,工件表面粗糙度值下降;增加磨削深度使磨削力上升、比磨削能下降、提高磨削效率,也能保证工件表面质量.     

钛合金Ti6Al4V高速磨削试验研究

为实现难加工材料钛合金的高效磨削,进一步发挥高速磨削的潜力,开展了钛合金Ti6Al4V高速磨削工艺试验研究,对磨削过程的磨削力、磨削比能以及磨削温度随单颗磨粒最大切屑厚度agmax的变化特征进行了分析。研究结果表明：不同砂轮线速度vs条件下,磨削力、磨削比能及磨削温度三者随单颗磨粒最大切屑厚度agmax变化的特征曲线略有不同,具体表现为,单颗磨粒最大切屑厚度agmax一定条件下,磨削力及磨削比能随着磨削速度的提高呈减小趋势,磨削温度则呈上升趋势,同时钎焊CBN砂轮的磨削力、磨削比能低于陶瓷结合剂及电镀CBN砂轮的磨削力、磨削比能,因此,利用钎焊CBN砂轮磨料有序排布的优势,选择合理的单颗磨粒最大切屑厚度,可在提高砂轮线速度的同时提高进给速度,从而提高磨削效率,实现钛合金的高速高效磨削。     

超高速磨削温度的实验研究

用人工热电偶方法对40Cr和45#钢的超高速磨削温度做了深入的实验研究.发现提高砂轮线速度,工件的磨削温度随之升高;但从某一速度开始继续提高砂轮线速度,磨削温度却呈明显下降的趋势.这就预示超高速磨削温度较低,适合磨削.同时对超高速磨削的比磨削能进行了研究,表明大切深超高速磨削是可行的,发现40Cr钢的超高速磨削性能优于45#钢.     

超硬磨料砂轮的激光修锐技术研究

激光修整超硬磨料砂轮的原理,利用Ｎｄ：ＹＡＧ固体脉冲激光器进行激光修锐青铜结合剂和树脂结合剂硬磨料砂轮的试验,用扫描电镜观察了激光修锐前后砂轮表面的微观表貌,对激光作用下砂轮表面不同结合剂材料的去除机理进行了分析,通过磨削陶瓷试验,研究激光修锐的金刚石砂轮的磨削性能,并与普通砂轮磨削肖修锐的金刚石砂轮进行对比。结果表明,采用试验所确定的激光参数可选择性地去除砂轮表面的结合剂材料,而不损伤超硬磨粒,     

A precision grinding method for screw rotors using CBN grinding wheel

Aiming at the high precision machining of screw rotors, a new grinding method for screw rotors using cubic boron nitride (CBN) grinding wheel is presented in this paper. Small electroplated CBN grinding wheel is firstly used to grind screw rotors. The mathematical model for the axial profiles of CBN grinding wheel is developed based on gear engagement theory. Taking the backlash of screw rotors and the coating thickness of CBN layer into consideration, the modification of the base body of the wheel shape is introduced into the design of the CBN grinding wheel. Wire cut electrical discharge machining low speed (WEDM-LS) was used to machine the base body of the CBN grinding wheel. The formed turning tools of the base body of CBN grinding wheel using WEDM-LS and the wheel shapes of CBN grinding wheel using the formed turning tool were performed. The CBN grinding wheels for the screw rotors were made to verify the validity and effectiveness of the presented method. The electroplated CBN grinding wheels were used to machine the screw rotors, and the machining experiments were performed. The data obtained in the experiments reach the fifth class of Chinese Standard GB10095-88.     

CBN砂轮超高速磨削条件下加工表面粗糙度的实验研究

在高速超高速磨削工艺实验基础上,分析了砂轮线速度、切削深度、最大未变形切屑厚度等工艺参数对45#钢、40Cr两种材料磨削表面粗糙度的影响,揭示了在高速超高速磨削条件下用CBN砂轮进行磨削时,表面粗糙度值随砂轮线速度的提高而减小,随切削深度及最大未变形切屑厚度增加而加大的变化规律和机理。为特定材料在高速超高速磨削条件下的加工提供了参考依据。     

超硬磨粒CBN砂轮的磨削性能

本研究的目的是评价三种砂轮在磨削高速工具钢时的磨削性能。采用ABWOOD平面磨床,在不同磨削条件下对材料去除率,比磨削能和磨削表面的热损伤进行了实验研究,同时借助专用装置采集了磨削过程中砂轮的动态磨损数据。研究结果表明,超硬磨粒CBN砂轮磨削M2高速钢时磨性能最佳,这种砂轮在硬铁族金属加工领域具有良好的应用前景。     

硬质合金YG8高速磨削工艺试验研究

采用树脂结合剂金刚石砂轮,对硬质合金YG8进行了高速磨削工艺试验研究,测得了不同砂轮线速度、磨削深度和工作台速度条件下的磨削力和表面粗糙度,并对磨削的表面形貌进行了观测,揭示了硬质合金YG8高速磨削的材料去除机理。试验结果表明:将高速磨削技术应用于硬质合金材料的加工是一种切实可行的加工方法,能得到较好的表面质量并提高加工效率。随着砂轮线速度的增加,或者工作台速度和磨削深度的减小,磨削的最大未变形切屑厚度减小,磨削力减小,材料的比磨削能增加,使得工件的加工表面质量得到改善。     

超音速火焰喷涂WC-17Co涂层的高速磨削机理试验研究

针对超音速火焰喷涂WC-17Co高硬涂层的加工难题,对WC-17Co涂层进行了高速/超高速磨削试验。通过考察不同金刚石砂轮和磨削工艺参数对磨削力、磨削温度和表面残余应力、表面/亚表面微观形貌和表面粗糙度的影响,讨论了最大未变形切屑厚度与比磨削能的内在关系,分析了磨削温度对表面残余应力的作用规律,探讨了法向磨削力对涂层亚表面损伤的作用规律。结果表明：WC-17Co涂层磨削去除是脆性和延性去除并存;提高砂轮线速度将使磨削力先快速减小后缓慢增大,磨削温度持续升高,涂层磨削从脆性去除转为延性去除的趋势也逐渐增强,表面残余应力由压应力逐渐转变为拉应力,而磨削高温引起涂层热塑性变形是表面残余应力状态转变的根本原因。涂层亚表面磨削损伤层平均深度随法向磨削力的增大而变大。提高砂轮线速度、降低工作台速度和减小磨削深度均能增大涂层磨削塑性去除的比例。     

树脂基圆弧金刚石砂轮的在位精密成形修整技术

针对球面、非球面及自由曲面超精密磨削加工用树脂基圆弧形金刚石砂轮难以精密修整的问题,提出基于旋转绿碳化硅(GC)磨棒的在位精密成形修整技术。在分析GC磨棒和圆弧砂轮几何关系的基础上,确定修整过程中圆弧插补轨迹的补偿方法及GC磨棒运动轨迹的设计方案。采用KEYENCE激光测微仪采集砂轮圆弧特征点,表征圆弧砂轮的修整状况。研究不同粒度的GC磨棒、进给深度和圆弧插补速度对圆弧金刚石砂轮修整率和修整精度的影响规律。研究结果表明,该修整方法可根据加工曲率半径要求实现不同圆弧半径砂轮的精密在位修整,修整后可自动消除砂轮垂直方向的位置偏差;采用400#和800#的GC磨棒对D3和D7砂轮均有较高的修整率(0.7~6.7);与400#和1500#的GC磨棒相比,800#GC磨棒更适合粒度为D3和D7圆弧金刚石砂轮的精密修整;相比圆弧插补速度,进给深度对砂轮的圆弧半径尺寸误差和形状误差影响更大,进给深度越小,圆弧半径尺寸误差和形状误差越小;修整后两种砂轮的圆弧半径误差均可控制在5%以内,D3砂轮的形状误差可控制在3μm/4 mm以内,D7金刚石砂轮可控制在6μm/4 mm以内,修整后比修整前形状误差提高14倍左右。     

On the temperature field during superficial grinding: an experimental study

Grinding is a mechanical process that involves a great amount of energy per unit volume of removed material. This energy is almost all converted into heat, causing a significant rise of the temperature, mainly on the surface of the workpiece. Therefore, locally, the surface of the workpiece will experience high increases in temperature during small periods of time, while the rest of the part remains at a low temperature. In this work we describe an experimental process to determine the temperature distribution on the workpiece, during a grinding operation. The forces acting on the workpiece and the temperature are measured simultaneously during the grinding process. Two different materials and three grinding wheels were used at three different depths of cut. It is possible to conclude that the high temperatures generated in the surface of the piece depend (among other factors) on the type of the piece material and on the physical characteristics of the used grinding wheels. Additionally, for steels, CBN wheels are the most suitable whenever high superficial temperatures must be avoided since alumina wheels produce temperatures substantially higher. This is a part of a broader work involving finite element method simulation of the grinding process.     

FORCE ANALYSIS FOR GRINDING WITH SEGMENTAL WHEELS

This paper describes a force model for grinding with segmental wheels. Both experimental and analytical results show that average grinding force decreases and peak force increases using segmental wheels as compared to conventional wheels. Larger spaces between segments further reduce the average force and increase the peak force. The reduction in average force is due to the size effect whereby the specific energy decreases at higher instantaneous material removal rates. An investigation of surface roughness and wheel wear reveals that modest amounts of segmentation reduce average force without increasing surface roughness or wheel wear.     

FORCE ANALYSIS FOR GRINDING WITH SEGMENTAL WHEELS

This paper describes a force model for grinding with segmental wheels. Both experimental and analytical results show that average grinding force decreases and peak force increases using segmental wheels as compared to conventional wheels. Larger spaces between segments further reduce the average force and increase the peak force. The reduction in average force is due to the size effect whereby the specific energy decreases at higher instantaneous material removal rates. An investigation of surface roughness and wheel wear reveals that modest amounts of segmentation reduce average force without increasing surface roughness or wheel wear.     

Some remarks on the chemical wear of diamond and cubic BN during turning and grinding

Previous experiments using simple grinding wheels consisting of a single layer of cubic boron nitride (CBN) or diamond grits on an electroplated rod have shown that the production of wear flats on the grits leads to an increasing grinding force which eventually results in the destruction of the nib. In one of the present experiments, similar worn areas are observed on the grits in a conventional type grinding wheel. The wear of the flats appears to be similar in type to that observed on the flanks of turning tools fabricated from single crystals of diamond and CBN. Experiments with such turning tools show wide variations in the rates of wear between diamond and CBN and between different difficult metal workpieces. These and previous results imply that the flats are formed by an attritious wear process conditioned by the chemical constitution of the tool, workpiece and environment. Further consideration of these various points should lead to the enhanced performance of diamond and CBN grinding wheels.