Predictive modeling of surface roughness in grinding

The surface roughness is a variable often used to describe the quality of ground surfaces as well as to evaluate the competitiveness of the overall grinding system. This paper presents the prediction of the arithmetic mean surface roughness based on a probabilistic undeformed chip thickness model. The model expresses the ground finish as a function of the wheel microstructure, the process kinematic conditions, and the material properties. The analysis includes a geometrical analysis of the grooves left on the surface by ideal conic grains. The material properties and the wheel microstructure are considered in the surface roughness prediction through the chip thickness model. A simple expression that relates the surface roughness with the chip thickness was found, which was verified using experimental data from cylindrical grinding.     

Influence of surface topography evolution of grinding wheel on the optimal material removal rate in grinding process of cemented carbide

Most of the reported studies on the optimization of grinding parameters do not consider the evolution of the surface topography of grinding wheels, and the established empirical models will no longer apply when the surface conditions of the grinding wheel changes. In this paper, an integrated model based on the surface topography of grinding wheel is established. The grinding process of cemented carbide is simulated using the established model, and the simulation results are analyzed to obtain the surface roughness model and the specific grinding energy model based on the undeformed chip thickness distribution. Subsequently, the grinding constraint models are defined according to the two grinding constraints—surface roughness and specific grinding energy. Through inversion analysis, the maximum material removal rate of the given grinding wheel surface conditions satisfying the defined grinding constraints are obtained, and the influence rules of the grinding wheel surface conditions on the maximum material removal rate are analyzed. Then the grinding wheel surface conditions are adjusted by changing the radial dressed height of the grinding wheel and the arrangement distance of the grains in wheel circumferential direction to improve the maximum material removal rate of the grinding wheel. Finally, the optimization results are verified through grinding tests of cemented carbide.     

Study on surface roughness model and surface forming mechanism of ceramics in quick point grinding

The quick-point grinding experiment of fluorophlogopite was conducted by using a MK9025A profile grinder which considered the simple single factor, such as the grinding wheel and table feed speed, grinding depth, inclining angle and deflection angle. The experimental results indicated that the surface roughness was mainly influenced on inclining angle and deflecting angle. Moreover, the modified model of the quick-point grinding process was proposed in the paper, which based on Malkin kinematics model, Snoeys empirical model and grinding thickness empirical model. The inclining angle and deflecting angle was introduced in the modified model. Comparison of the predicted results of these models and experimental ones indicated that the modified model was in well agreement with the experimental data. Further, standard deviation of these models and experiment was studied in the paper, it is found that the modified model was the more ideal. In order to study the effect of various technology factors on the sensitivity of surface roughness, “Relative extremum error” concept was first proposed in the paper. It was found that simple single factor in the modified model were relatively sensitive to surface roughness than other models.     

Selection of optimum conditions for maximum material removal rate with surface finish and damage as constraints in SiC grinding

Efficient grinding of structural ceramics requires judicious selection of operating parameters to maximize removal rate while controlling surface integrity. Grinding of silicon carbide is difficult because of its low fracture toughness, making it very sensitive to cracking. In the present work, experiments were carried out to study the effect of wheel parameters; grain size and grain density and grinding parameters; depth of cut and feed on the surface roughness and surface damage. The significance of the grinding parameters on the selected responses was evaluated using analysis of variance. Mathematical models were developed using the experimental data considering only the significant parameters. A genetic algorithm (GA) code has been developed to optimize the grinding conditions for maximum material removal, using a multi-objective function model, by imposing surface roughness and surface damage constraints. The choice of including manufacturer’s constraints on the basis of functional requirements of the component for maximizing the production rate was also embedded in the GA code.     

镀镍金刚石在硬质合金精密磨削中的性能

为研究镀镍金刚石砂轮在硬质合金精密磨削时的磨削性能,用裸料金刚石砂轮同其进行对比磨削实验,分析二者在磨削功率、磨削比、磨削表面粗糙度以及砂轮表面形貌等方面的差异。研究结果表明:在磨削参数相同的情况下,镀镍金刚石砂轮在磨削时消耗的功率比裸料金刚石砂轮大,但是相对稳定;镀镍金刚石砂轮的体积磨削比要高于裸料金刚石砂轮的体积;在粗糙度方面,镀镍金刚石砂轮优于裸料金刚石砂轮,但是其黏屑较多,砂轮有堵塞现象。      

Investigation of grinding modes in horizontal surface grinding of optical glass BK7

Grinding is one of the most important processes to manufacture hard-brittle materials such as optical glass. It is often desired to increase the material removal rate while maintaining the desired surface quality. The success of this approach relies on the better understanding of the relationship between the grinding modes and the characteristics of surface and subsurface integrities. Based on the kinematic analysis of horizontal surface grinding as well as the features of grinding-induced cracks, four grinding modes were proposed. They are brittle mode, semi-brittle mode, semi-ductile mode and ductile mode. The horizontal surface grinding of optical glass BK7 has been studied using diamond grinding wheel. The four different grinding modes have been investigated with the characteristics of surface morphologies before and after etching, surface roughness, subsurface damages as well as indentation depth. It was found that the level of surface roughness and depth of subsurface damage were strongly dependent on grinding mode. This study provides valuable insights into the material removal mechanism and the dependence of surface and subsurface integrities on grinding mode.     

Application of Taguchi and response surface methodologies for geometric error in surface grinding process

The geometric error in the surface grinding process is mainly affected by the thermal effect and the stiffness of the grinding system. For minimizing the geometric error, the selection of grinding parameters is very important. This paper presented an application of Taguchi and response surface methodologies for the geometric error. The effect of grinding parameters on the geometric error was evaluated and optimum grinding conditions for minimizing the geometric error were determined. A second-order response model for the geometric error was developed and the utilization of the response surface model was evaluated with constraints of the surface roughness and the material removal rate. Confirmation experiments were conducted at an optimal condition and selected two conditions for observing accuracy of the developed response surface model.     

Use of surface roughness measurements to improve the estimation of the heat partition in grinding

In grinding, the heat partition is used to estimate the percentage of energy entering the workpiece which makes it possible to estimate grinding temperatures. In this work, a correlation was observed between surface roughness and the heat partition when grinding 1018 steel with an 80 grit aluminum oxide wheel. This correlation was used to improve the usability of a popular heat partition model by making it easier to estimate the grain radius, which is an important parameter in this model. The grain radius is used to account for the grinding wheel surface topography and is virtually impossible to directly measure in practice. To validate the proposed model, infrared temperature measurements along with 3D finite element simulations were used to determine the heat partition for different dressing conditions and techniques. For the experimental conditions used in this research, the measurements and simulations confirmed that one can use surface roughness to estimate the grain radius. The average difference between the heat partition predicted using the proposed model and the conventional approach was 7.5%, while the resulting maximum grinding temperatures predicted using the proposed model agreed with infrared temperature measurements to within 5%.     

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。      

Research on the surface characteristics in ultrasonic grinding nano-zirconia ceramics

Nano-ceramics possesses ascendant mechanical property and physical characteristics contrast with traditional engineering ceramics, and its machining with ultrasonic assistance has been considered as one of the most efficient methods. In the present paper a novel ultrasonic grinding vibration device has been designed and the theoretical models of surface roughness was created for ultrasonic vibration grinding. The influences of grinding parameters on surface roughness were tested. According to the experimental data and AFM pictures, the microsurface characteristics and the critical ductile depth of cut with/without ultrasonic assistance was analyzed. It has been discovered that the critical ductile depth of cut is larger than that in common grinding and than that of traditional ZrO₂ engineering ceramics. The experimental results showed that machining nano-ZrO₂ ceramics with ultrasonic assistance by nano-class scale is feasible.     

Generalized practical models of cylindrical plunge grinding processes

This paper presents generalized grinding process models developed for cylindrical grinding processes based on the systematic analysis and experiments. The generalized model forms are established to maintain the same model structures with a minimal number of parameters so that the model coefficients can be determined through a small number of experiments when applied to different grinding workpiece materials and wheels. The relationships for power, surface roughness, G-ratio and surface burning are established for various steel alloys and alumina grinding wheels. It is shown that the established models provide good predictive capabilities while maintaining simple structures.     

Analysis and simulation of the grinding process. Part III: Comparison with experiment

A method of simulating dressing and grinding was described in Parts I and II of this three-part series. In Part III, the effects on grinding performance of varying the dressing conditions are simulated and compared with experimental results. The results show that a coarse dressing condition leads to low grinding force and grinding power but a high workpiece surface roughness. The grinding performance of the wheel in the dwell period for “spark-out” is simulated. Simulated and experimental results both show that grinding power in the dwell period decreases following an exponential decay function, however the reduction of surface roughness does not follow an exponential decay.     

几种因素对快速点磨削表面粗糙度的影响

分析了点磨削加工表面形貌及其精度的几种影响因素.研究发现:砂轮速度和磨削深度对表面粗糙度的影响都可归结为未变形切屑厚度的改变.减小点磨削倾斜角,可以减小未变形切屑厚度,从而得到理想的表面粗糙度.加大磨削深度和轴向进给量可提高材料去除率,但会造成粗糙度增大.这可归结为砂轮有效磨粒数的减少导致工件的表面粗糙度降低.点磨削通过改变倾斜角大小来增加参与磨削的有效磨粒数,保证高材料去除率的同时获得良好表面质量.增加光磨次数和应用倾斜型砂轮都增加了磨粒和工件表面轮廓突峰的接触次数,对于改善表面粗糙度十分有益.     

金刚石钻磨头超声振动钻磨硬脆材料表面质量的试验研究

硬脆材料以其优良的性能在生产实践中得到了广泛应用，但其低塑性、易脆性及不导电性等使得加工十分困难，尤其是超精密表面制作更加困难。为此，本文将超声振动引入普通钻磨中，介绍了超声振动切削原理，通过超声与普通两种方式下的表面粗糙度试验和微观形貌观察得出以下结沦：1）不同加工参数时，超声振动钻磨时的工件表面粗糙度值均低于普通钻磨时的表面粗糙度值；2）随着进给量、工件转速和输入功率的增加，超声和普通钻磨时的表面粗糙度均呈上升趋势；3）普通钻磨加工后孔壁表面有宽度和间距不均匀的沟槽，并且沟槽较宽，而超声钻磨加工后表面沟槽（划痕）较浅且均匀。     

镍基单晶高温合金磨削润滑方式对表面完整性的影响

为提高镍基单晶高温合金DD5的磨削表面质量,采用单因素试验探究3种磨削加工方法（干磨削、传统浇注式、微量润滑（minimum quantity lubrication, MQL））对其表面完整性的影响。结果表明:在不同冷却条件下,DD5磨削表面粗糙度从低到高依次为MQL、传统浇注式、干磨削方式下的。当砂轮线速度较小时,磨削表面质量较差,存在较深划痕和沟槽;当砂轮线速度较大时,磨削表面质量较好,磨痕较小,且分布均匀。在距磨削表面为5～15 μm时,DD5亚表面显微硬度随着深度的增加而急剧下降;在距磨削表面为20～150 μm时,DD5亚表面显微硬度趋于平衡,其在540 HV附近波动。      

Modeling and prediction of surface roughness in ceramic grinding

Surface quality of workpiece during ceramic grinding is an ever-increasing concern in industries now-a-days. Every industry cares to produce products with supposedly better surface finish. The importance of the surface finish of a product depends upon its functional requirements. Since surface finish is governed by many factors, its experimental determination is laborious and time consuming. So the establishment of a model for the reliable prediction of surface roughness is still a key issue for ceramic grinding. In this study, a new analytical surface roughness model is developed on the basis of stochastic nature of the grinding process, governed mainly by the random geometry and the random distribution of cutting edges on the wheel surface having random grain protrusion heights. A simple relationship between the surface roughness and the chip thickness was obtained, which was validated by the experimental results of silicon carbide grinding.     

机匣零件气道面及支板面的机器人磨抛加工

提出机匣零件气道及支板面机器人磨抛加工技术。针对机匣的气道面及支板面开发高带宽长悬伸自适应磨具,根据力控磨具的受力分析进一步设计PID力控制器,采用Robotmaster进行磨抛刀路规划,在机匣试验件上开展力控磨抛方案和无力控磨抛方案的对比试验。结果显示:力控磨抛方案的精度为±1.5 N, 且平均表面粗糙度为1.450 μm;而无力控磨抛方案中的力为20.0 N, 平均表面粗糙度为2.069 μm。力控磨抛后的机匣表面质量更高。      

Mirror surface grinding for brittle materials with in-process electrolytic dressing

Use of a diamond wheel with superabrasive is required for mirror-like surface grinding of brittle materials. However, conventional dressing methods cannot apply to the diamond wheel with superabrasive. Recently, an electrolytic dressing method was developed for use with a cast iron-bonded diamond wheel and superabrasive. This technique can replace lapping and polishing. Using electrolytic dressing, surface roughness of the workpiece was improved significantly, and the grinding force was very low and the continuity of the grinding force was also improved. The purpose of this study was to achieve mirror-like surface grinding of ferrite with electrolytic dressing of a metal-bonded diamond wheel. For application of ultraprecision grinding for brittle material, superabrasive, air spindle, and in-process electrolytic dressings were used. Additionally, the effects of pick current and pulse width on ground surface were investigated, and suitable dressing conditions for ferrite were determined.     

砂轮刚性对磨削性能及产品加工质量的影响

通过测量不同砂轮磨削时机床功率、磨削区温度、刀具的表面粗糙度和刃口质量,分析砂轮刚性改变对砂轮磨削性能和刀具质量的影响。研究发现:在一定范围内降低砂轮的刚性可以提高砂轮的磨削性能,改善刀具的加工质量。其中,加入体积分数10%的尼龙制备的砂轮对其刚性改善比较明显,在相同的磨削条件下,其磨削区的平均温度较普通砂轮磨削区的平均温度低50℃左右;累计磨削相同工件后,机床负载约为使用普通砂轮时的30%~50%;磨削得到的刀具表面粗糙度降低,可以达到R_a0.02μm以下,且磨削纹路规则;在×500倍显微镜下,观察不到刀具崩刃等缺陷,刃口质量得到明显改善。      

Relationship between surface roughness and subsurface crack depth during grinding of optical glass BK7

Subsurface damages induced by grinding strongly influence the mechanical strength and optical quality of optical glasses. It is meaningful to rapid evaluate the depth of subsurface cracking through the measurement of surface roughness under different grinding parameters. Based on the features of surface and subsurface cracks as well as the kinetic analysis of surface grinding, the relationship between surface roughness and subsurface crack depth was established. Surface grinding experiments for optical glass BK7 were conducted. Utilizing optical microscope, optical profiling system and polishing-etching technique, the dependence of surface roughness and subsurface crack depth on grinding parameters was systematically analyzed. The predicted model of the relationship between surface roughness and subsurface crack depth was compared with experimental results. It was found that the relationship between surface roughness and subsurface crack depth is influenced by the half apex angle of abrasive grain as well as the magnitude of extra grain extrusion.