Experimental and finite element analysis of temperature and energy partition to the workpiece while grinding with a flexible robot

Grinding processes performed with flexible robotic tool holders are very unlike conventional types of grinding because of low stiffness of the robot's structure. A special flexible robotic grinding process is used for in situ maintenance of large hydroelectric equipment for bulk material removal over large areas rather than as a finishing step, as is the case for most conventional grindings. Due to the low structural stiffness of tool holder, cutting is interrupted at each revolution of wheel during the grinding process. In this study, an investigation is carried out to determine the temperatures and energy partition to the workpiece for the above-mentioned flexible robotic grinding process by a three-dimensional finite element thermal model. Experiments were undertaken using embedded thermocouples to obtain the subsurface temperature at several points in the workpiece during the process. Then, energy partition to the workpiece was evaluated using a temperature-matching method between the experimental and numerical results. This ratio is used for predicting the temperature field at the wheel–workpiece interface with a relevant heat source function. Kinematics of cut and the flexible robot's dynamic behavior are considered in applying the heat input to the model. The energy partition to the workpiece in this specific flexible grinding process is found to be lower than for analogous conventional precision grinding processes. Two models, one from the literature and one from the power model of the process, are modified and proposed for determining the energy partition. The results showed that the energy partition ratio decreases by increasing the process power. Also, this ratio slightly decreases at higher feed speeds. In addition, lower temperatures were seen at higher powers due to the lower intensity of heat input over a larger contact area. Experimental observations show close agreement between simulated contact temperatures and measured results.     

Mirror surface grinding of ceramics using a three-axis precision cnc grinding machine

In this paper, the mirror surface grinding of ceramics, such as Si₃N₄ and Al₂O₃---TiC, was realized with average roughness less than 10 nanometers. For the grinding operation, a three-axis CNC grinding machine tool was designed and manufactured. The grinding machine is composed of an air spindle, a high damping resin concrete bed and a three-axis CNC controller with high resolution AC servo motors. The dynamic properties of the grinding machine, such as the natural frequencies and damping of the spindle, were experimentally measured to improve the ground surface quality. Also, the truing method to improve the straightness of the grinding wheel with 1 μm accuracy, was developed.     

CSS-42L钢磨削力和比磨削能的实验研究

采用白刚玉和绿碳化硅两种不同磨料的砂轮对CSS-42L钢进行了平面切入式磨削实验.选取磨削力、磨削力比和比磨削能为指标,通过单因素实验分析比较了在白刚玉砂轮和绿碳化硅砂轮平面切入式磨削条件下,CSS-42L钢的磨削加工性.实验结果表明,相同条件下,绿碳化硅砂轮磨削时的磨削力、磨削力比和比磨削能均明显高于白刚玉砂轮;绿碳化硅砂轮从初期磨损阶段进入稳定磨损阶段所用时间至少是白刚玉砂轮的2倍;两种砂轮磨削时的比磨削能均随着当量磨削厚度的增加呈幂函数降低.     

陶瓷磨削中新型多孔金属结合剂金刚石砂轮磨损特征研究

在磨削Al2O3工程陶瓷材料过程中,利用三维视频显微镜跟踪观察了新型多孔金属结合剂金刚石砂轮,金刚石的磨损过程以及砂轮表面形貌的变化。分析了新型砂轮中金刚石磨损的主要形式及原因,砂轮工作表面的状态变化特征。试验结果表明：新型多孔金属结合剂金刚石砂轮在加工过程中,金刚石的磨损形式包括磨耗磨损,破碎及脱落等磨损过程,其中以磨耗磨损为主;同时,随着结合剂的不断磨除,砂轮深层磨料能够不断出露,取代表面钝化失效、脱落的金刚石,且砂轮表面孔隙结构,随磨损过程呈交替更迭变化,砂轮具有较好的自锐性。     

工程陶瓷小砂轮轴向大切深缓进给磨削加工的砂轮磨损分析

小砂轮轴向大切深缓进给磨削以较大切深实现了较高的材料去除率,且使用的砂轮直径比常规磨削用砂轮小很多,我们针对这一特点开展了研究。实验通过改变砂轮转速、工件转速和磨削深度等加工参数,对轴向大切深缓进给磨削加工后的砂轮表面进行了形貌观测和磨损分析。分析表明,砂轮各部分的磨损形式与其在磨削过程中所起的作用有关:砂轮端面是磨削加工的主磨削区,磨粒和结合剂主要发生较大程度的磨损;砂轮圆周面主要对已加工表面进行修磨,因而结合剂和磨粒磨损为主要磨损形式;砂轮拐角作为过渡磨削区,承受的磨削力也比较大,而且由于磨粒与结合剂的结合力相对较小,因此易发生磨粒和结合剂的脱落。     

粗磨粒金刚石砂轮精密磨削工程陶瓷的试验研究

为了实现粗磨粒金刚石砂轮延性域磨削加工SiC陶瓷材料,采用碟轮对粒径为297~420μm的粗磨粒金刚石砂轮进行了精密修整。然后,使用经过修整好的粗磨粒金刚石砂轮对SiC陶瓷进行磨削加工。在此基础上,对不同的砂轮线速度、工件进给速度、磨削切深对SiC陶瓷表面粗糙度和表面形貌的影响进行了研究。试验结果表明:经过精密修整的粗磨粒金刚石砂轮是能够实现SiC陶瓷材料的延性域磨削的,表面粗糙度值Ra达到0.151μm;随着砂轮线速度增大、工件进给速度和磨削切深减小,SiC陶瓷表面的脆性断裂减小,塑性去除增加。     

Depth-of-cut errors in ELID surface grinding of zirconia-based ceramics

Based on the analysis of a surface grinding system and the material removal mechanism, a mathematic model has been proposed to predict the accumulated error between the total set depth-of-cut (DoC) and the total actual depth-of-cut (ADoC) in multi-pass surface grinding of zirconia-based ceramic materials. Design of Experiments (DoE) approach has been implemented to carry out experiments. The influence of the set DoC of each grinding pass, the total set DoC, and the grinding wheel velocity on the accumulated errors in ADoC has been investigated in detail in surface grinding of zirconia-based ceramics both with electrolysis in-process dressing (ELID) and without ELID. It has been observed that the accumulated DoC errors increase faster in the first few passes and gradually reach a saturation after a certain total DoCs (about 8–10 grinding passes) and a higher step DoC leads to a faster (fewer passes) saturation of the accumulated DoC errors. Compared to grinding without ELID, it has been found that ELID-grinding is characterized with better process stability and ELID offers positive effects on material removal rate (MRR), especially in case of removing large volume of material with the same grinding parameters.     

高速磨削颗粒增强钛基复合材料的热分配分析

针对颗粒增强钛基复合材料(PTMCs)高速磨削的特征,以均匀热源为模型,提出了一种计算磨削过程中热分配比例的新方法。采用CBN超硬磨料砂轮在80~160m/s的速度范围内进行了高速磨削验证,试验结果表明:PTMCs高速磨削热传递过程中比能es与ds1/4ap-3/4vw-1/2呈直线关系,与理论分析相一致,并基于此得到电镀CBN砂轮高速磨削PTMCs进入工件的热量比例为52.0%~79.5%。同时,进行了电镀砂轮高速磨削PTMCs温度场仿真,探明了其温度分布特征。     

3C陶瓷用钎焊金刚石小磨头的端面磨损

金刚石微铣磨头广泛用于3C产品的先进陶瓷构件加工中。通过对3C产品中最常用的氧化锆陶瓷工件进行磨削试验,观察钎焊金刚石微铣磨头磨损过程中的形貌演变,并统计氧化锆陶瓷的累计去除体积与磨头上金刚石磨粒磨损数量的对应关系,对比分析铜基和镍基钎料金刚石微铣磨头的磨损失效情况及寿命。结果表明:在相同加工参数条件下,铜基磨头的寿命较长,是镍基磨头寿命的1.2倍;在磨削过程中,金刚石磨头端面的磨粒存在破碎、磨平、脱落3种主要失效形式,且磨头的磨损主要从磨头端面边缘开始,逐步向其中心扩散,直至磨粒磨损严重而导致磨头失效。      

基于比磨削能的聚晶金刚石磨削机理研究

本文基于试验所测定的聚晶金刚石（PCD）比磨削能u与磨削工艺参数的关系,结合所观查的对应磨削表面微观形貌,研究了磨削机理与比磨削能的关系。结果表明：比磨削能u值小即u〈25000J／mm^3时,PCD材料磨削机理为疲劳脆性去除;比磨削能u值较大即25000J／mm^3≤u〈120000J／mm^3时,PCD材料磨削机理为随着比磨削能u值的增大,疲劳脆性去除的比例减少、机械热量除及热化学去除的比例增大;比磨削能u值很大,即us≥120000j／mm^3时,PCD材料磨削机理为机械热去除及热化学上除、基本不发生疲劳脆性去除。     

小直径砂轮超声振动磨削SiC陶瓷的表面质量研究

用小直径砂轮超声振动磨削和普通磨削加工SiC陶瓷零件,对比研究砂轮线速度、工件进给速度、磨削深度和超声振幅对其磨削表面质量的影响。结果表明:与普通磨削相比,超声振动磨削的磨粒轨迹相互交叉叠加,工件表面形貌更均匀,表面质量更好。由于超声振动时的磨粒划痕交叉会使磨粒产生空切削,因而降低了其磨削力,使磨削过程更加稳定。超声振动磨削的表面粗糙度和磨削力随砂轮线速度和超声振幅的增加而降低,随工件进给速度和磨削深度的减小而降低。且砂轮线速度、工件进给速度较小时,超声振动磨削的效果更明显。      

Li-Ti铁氧体陶瓷精密磨削的试验研究

铁氧体陶瓷的应用因其表面加工质量难以保证而受到很大限制。本文采用80/100#树脂结合剂金刚石砂轮和W 20石墨白刚玉砂轮对Li-Ti铁氧体陶瓷进行了磨削试验。研究了单位宽度磨削力、表面粗糙度和单位宽度材料去除率随磨削参数的变化规律,观察并分析了铁氧体工件磨削后的表面微观形貌。结果表明:Li-Ti铁氧体的表面粗糙度值可达到Ra0.084μm,实际单位宽度材料去除率达到90%,材料以塑性方式去除;采用上述砂轮可实现铁氧体陶瓷的高效精密磨削。     

超声振动磨削纳米氧化锆陶瓷材料的磨削力及表面残余应力的研究

纳米陶瓷由于其相对于工程陶瓷优越的力学性能及物理特性,在各行业都有广泛的应用前景。采用超声复式加工方法,针对不同的磨削参数对纳米ZrO2陶瓷进行了普通和超声磨削实验,研究了磨削参数对磨削力的影响,并通过X射线衍射分析了在普通和超声磨削状态下对工件表面残余应力及纳米ZrO2陶瓷各晶相的影响。研究结果表明:利用超声振动磨削能有效减少磨削力,不同的磨削方式对纳米ZrO2陶瓷表面残余应力影响较大,采用普通磨削工件表面残余应力为拉应力,当超声振动方向平行于砂轮速度方向时,工件表面残余应力为压应力,振动方向垂直于砂轮速度方向时工件表面残余应力绝对值较小。     

Single point diamond dressing of aluminium oxide grinding wheels and its influence in cylindrical traverse grinding

An investigation conducted at Loughborough University of Technology into the dressing of grinding wheels using single point diamond tools [1], has shown the importance of the correct selection of dressing variables when preparing the grinding wheel for both rough and finish cylindrical traverse grinding operations, since they influenced both the useful working life of the wheel when rough grinding, and the resulting workpiece surface finish when fine grinding.This particular paper deals with those aspects of wheel dressing which influence rough grinding conditions, and highlights the usefulness of grinding force as a means of assessing the severity of dressing on wheel performance at the start of grinding; and force ratio and grinding ratio through their ability to pinpoint the various stages of wheel wear.The dressing variables found to have the greatest influence on both rough and finish cylindrical traverse grinding conditions were the cross-feed rate and diamond geometry, with the depth of cut being of secondary importance.     

Study on the grinding of advanced ceramics with slotted diamond wheels

Slotted diamond wheel grinding is a new machining technology. In this paper, an experimental study on the cutting force and the grinding temperature for ceramic face grinding using slotted diamond wheels is presented. Moreover, the empirical relationships related with the material removal rate, the surface roughness, the depth of cut, the wheel speed and the grain size are discussed. With these relationships, a temperature field for face grinding has been built. The work contributes to the fundamental theories for optimal design of slotted diamond wheels.     

金刚石砂轮磨削轴承用ZrO2 陶瓷表面质量研究

在氧化锆陶瓷磨削中为获得较高质量表面,采用单因素试验研究磨削深度、砂轮线速度、工件进给速度对氧化锆陶瓷精密磨削表面质量的影响规律及材料去除机理,通过超景深三维显微镜以及扫描电子显微镜,观察氧化锆陶瓷试件磨削后的表面形貌,最后用正交试验法进行优选并验证。结果表明:磨削表面的粗糙度随磨削深度、工件进给速度增大而增大,随砂轮线速度增大先减小、后增大。在磨削深度5 μm、砂轮线速度40 m/s、工件进给速度1 000 mm/min的优化组合条件下,磨削3组氧化锆陶瓷的平均表面粗糙度R_a为0.388 9 、0.417 0和0.403 7 μm。      

Influence of coolant conditions in ultrasonic assisted grinding of high performance ceramics

Ultrasonic-assisted grinding finds its main application in the processing of hard, brittle materials. In particular through the superposition of the conventional feed rate and the high velocity with ultrasonic frequency, advantages in drilling processes can be reached. The application of ceramic and glass materials for high performance parts in the aerospace and aeronautical industries, in biomedical components and for parts exposed to wear in the automotive industry is steadily increasing due to their favorable properties. The drilling of these materials in their sintered state with high accuracy and reproducibility presents a significant challenge with respect to the choice of tool and the process parameters implemented. This paper focuses on the influence of the cooling lubricant in combination with different tool specifications on the grinding process. The grain size of the diamond grinding pins was varied in the range of 30 to 126 μm. As bond types, electroplated, sintered bronze and sintered Fe/Co bonds were investigated as well as the pressure of the cooling lubricant and the influence of these factors on the process behavior. In additional to the process behavior, the residual stress profiles of the workpieces were evaluated.     

陶瓷刀片周边磨床数控加工系统

介绍了陶瓷刀片周边磨床数控加工系统的性能、硬件结构和软件设计。系统的控制核心采用工业工作站电脑 ,系统软件采用模块化设计 ,用C语言编程     

氧化铝增韧陶瓷的高效ELID精密磨削实验研究

氧化物增韧陶瓷是一种高技术陶瓷材料,具有高强度、高韧性以及良好的耐磨、耐腐蚀性能。在一般的加工过程中,采用普通树脂砂轮对硬度较高的氧化铝增韧陶瓷材料进行磨削时,磨料的消耗比较快,磨削比较低,仅为8,10左右。通过ELID磨削对氧化铝陶瓷进行高效磨削实验,从砂轮速度、进给速度、砂轮粒度和砂轮电解活化钝化趋势等因素中,找到合适的加工工艺参数,使效率和精度达到最优。实验表明,砂轮速度和进给速度对磨削比影响较大;砂轮粒度和砂轮电解活化钝化趋势对表面质量影响较多。使用优化后的ELID磨削工艺使氧化铝陶瓷材料的加工效率提高了50％。磨削比增大到60～100。     

纳米复相陶瓷超声振动平面磨削温度的试验研究

本文采用人工热电偶测温方式,对纳米ZrO2增韧氧化铝复相陶瓷,进行了普通和超声平面磨削温度试验研究.给出了普通和超声磨削两种情况下温度场的分布状态与规律,研究了不同的磨削参数,对陶瓷磨削温度的影响.研究得出:超声磨削的表面温度,一般比普通磨削的温度至少低70℃,复相陶瓷由于其材料的热特性,表现出距离表面越近,温度梯度越大的规律.磨削参数对表面温度的影响规律是,磨削深度影响最大,进给速度次之,砂轮速度最小.