Evaluation of the root-mean-square slope of 3D surface topography

Based on the application of fractal geometry theory, a quantitative evaluation method of root-mean-square (RMS) slope of 3D homogeneous and stochastic surface topography is proposed, by means of the concept of surface spectral moments. Through the FFT of discrete data from the profiles measured by a Talysurf-5 contact stylus instrument, the power spectrum and the fractal dimensions of the profiles are obtained. Furthermore, the second order spectral moments of the profiles and the surfaces are found. These parameters are used to define the evaluation measure of RMS slope of the surface. By the experiments for ground and fine turned specimen, the results confirm the correctness of this method.     

Mechanisms in the generation of grinding wheel topography by dressing

For the process of dressing vitrified bonded grinding wheels with diamond tools it has been unknown how the wheel topography is generated. Moreover, the influence of the kinematical dressing parameters on the wheel wear behavior has not been quantified. In the course of this article the grinding wheel was dealt with as a porous ceramic composite. In FEM simulations common dressing forces and usual dressing tool geometries were applied. The results were verified by dressing tests and grinding wheel scratch tests which show the wheel wear mechanisms. The common practice of decreasing the grinding wheel surface roughness by a finishing dressing stroke has to be reconsidered, because previous dressing strokes with higher depths of cut can weaken the grinding wheel structure and lead to an unsteady phase with high grinding wheel wear after dressing.     

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.     

Experimental study on grinding force and grinding temperature of Aermet 100 steel in surface grinding

This paper investigates grinding force and grinding temperature of ultra-high strength steel Aermet 100 in conventional surface grinding using a single alumina wheel, a white alumina wheel and a cubic boron nitride wheel. First, mathematical models of grinding force and grinding temperature for three wheels were established. Then, the role of chip formation force and friction force in grinding force was investigated and thermal distribution in contact zone between workpiece and wheel was analyzed based on the mathematical model. The experimental result indicated that the minimum grinding force and the maximum grinding force ratio under the same grinding parameters can be achieved when using a CBN wheel and a single alumina wheel, respectively. When the phenomenon of large grinding force and high grinding temperature appeared, the workpiece material would adhere locally to the single alumina wheel. Grinding temperature was in a high state under the effect of two main aspects: poor thermal properties of grinding wheel and low coolant efficiency. The predicted value of grinding force and grinding temperature were compared with those experimentally obtained and the results show a reasonable agreement.     

Simulation of precision grinding process, part 1: generation of the grinding wheel surface

This paper is in two parts describing the kinematic simulation of the grinding process. The first part is concerned with the generation of the grinding wheel surface. A numerical procedure for effectively generating the grinding wheel topography is suggested. The procedure is based on the transformation of a random field. The sufficient condition for the transformation is discussed, and two transformations satisfying the condition are introduced. Numerical examples are used to illustrate the viability of the approach. It will be shown that the generated and measured grinding wheel topography share the same probabilistic characteristics.     

Simulation of surface grinding process, part 2: interaction of the abrasive grain with the workpiece

This paper is the second part of the two-part series, which describes the kinematic simulation of the grinding process. The complex wheel–workpiece interaction is taken into consideration in the generation of the workpiece surface. An algorithm is proposed to identify the active abrasive grains and their attack angles from the wheel topography. Based on the critical values of the attack angle, the abrasive grain is determined either to cut, plough or rub the workpiece. A numerical example is used to validate the approach.     

金刚石砂轮磨削铁氧体的表面粗糙度与形貌分析

本文研究了树脂结合剂金刚石砂轮磨削铁氧体材料时,磨削深度、工件进给速度对磨削表面粗糙度和材料去除方式的影响规律,以此探索提高铁氧体磨削表面质量的有效途径。采用单因素法设计试验方案对铁氧体进行磨削,测量表面粗糙度数据并对其进行方差分析,对铁氧体磨削表面形貌进行观察。结果表明：随着磨削深度、工件进给速度的增加,表面粗糙度值升高,同时表面塑性痕迹减少,脆性断裂痕迹增加,且磨削深度对表面粗糙度的影响要比工件进给速度的更显著,因此,制定磨削工艺时,考虑到粗磨为了提高效率,降低表面损伤,优化得到磨削工艺为磨削深度5μm,工件进给速度10 m/min;精磨为了获得较低的表面粗糙度,采用磨削深度5μm、工件进给速度为5 m/min,可以提高磨削表面延展性。     

A study of surface topography, friction and lubricants in metalforming

In this paper are presented the results of investigations concerning the relation between friction behaviour and surface topography using various lubricants and initial workpiece surface conditions in ring upsetting and rod extrusion processes. The tests were carried out using either a liquid lubricant or under clean dry conditions. Two types of workpiece surfaces, random and directional, were prepared by either shotblasting, or EDM or turning to different levels of surface finish. Not only has the friction effect of lubricant and initial surface been studied, but also the surface topography of the finished products has been examined in detail, to obtain a better understanding of the mechanism of lubrication and surface interaction. It was found that, for random surfaces, smoother ones could retain more lubricant and decrease friction resistance. The experimentation also demonstrated that turned surfaces were effective in reducing friction, but the final surface finish of the workpiece was not as good as that from random surfaces.     

基于图像拼接的砂轮表面三维形貌图重构

为了实现大面积砂轮表面形貌的计算机视觉检测,本文利用视频系统从两个不同视角采集钎焊金刚石砂轮表面形貌,通过特征配准法找出两幅图像的特征点和匹配点,然后对图像进行拼接融合,最终得到拼接后的目标图像,实现了砂轮表面三维形貌图的有效重构。     

Effect of grinding wheel spindle vibration on surface roughness and subsurface damage in brittle material grinding

The external interference and vibration can seriously affect the machining errors in brittle materials grinding process. This paper proposes a new model to analyze the relationship between surface roughness (SR) and subsurface damage (SSD) depth on the basis of grinding kinematics analysis and indentation fracture mechanics of brittle materials taking the wheel spindle vibration into account. The basic equations, for example, equations of grain trajectory and penetration depth are derived in new forms. Based on the basic equations above, the existing SR and SSD formulae are modified for further study. The effects of grinding and vibration parameters on SR and SSD are respectively analyzed in detail. Results show that both SR and SSD increase with the increase of table speed and vibration amplitude resulting in bad surface and subsurface quality. On the other hand, both the increasing grinding speed and decreasing vibration frequency can improve the quality of ground surface and subsurface with small SR and SSD. In addition, the increase of initial grinding depth and vibration initial phase increase the depth of SSD but have little effect on SR. The penetration depth and distance between grain's tip and finished surface are the two main factors considered to cause the different effect laws on SR and SSD among these parameters. Experiment is carried out to validate the rationality of proposed model. The effect trends of various grinding parameters on SR obtained by our model consist with measured experimental data. The typical subsurface crack system is clearly revealed through the experimental observation on SSD using SEM. Finally, the relationship between the two is fitted utilizing quadratic polynomial. Results show that the SSD depth is nonlinear monotone increasing with SR and the fitting accuracy is more or less affected by both grinding and vibration parameters.     

A study on surface grinding of 300 mm silicon wafers

Most of today's IC chips are made from 200 mm or 150 mm silicon wafers. It is estimated that the transition from 200 mm to 300 mm wafers will bring a die cost saving of 30–40%. To meet their customers' needs, silicon wafer manufacturers are actively searching for cost-effective ways to manufacture 300 mm wafers with high quality. This paper presents the results of a study on surface grinding of 300 mm silicon wafers. In this study, a three-factor two-level full factorial design is employed to reveal the main effects as well as the interaction effects of three process parameters (wheel rotational speed, chuck rotational speed and feedrate). The process outputs studied include spindle motor current, surface roughness, grinding marks and depth of subsurface cracks.     

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.     

An analysis of grinding power and surface roughness in external cylindrical grinding of hardened SCM440 steel using the response surface method

The aim of this study was to analyze effectively the grinding power spent during the process and the surface roughness of the ground workpiece in the external cylindrical grinding of hardened SCM440 steel using the response surface method. A Hall effect sensor was used for measuring the grinding power of the spindle driving motor. The surface roughness was also measured and evaluated according to the change of the grinding conditions. Response surface models were developed to predict the grinding power and the surface roughness using the experimental results. From adding simply material removal rate to the contour plot of these mathematical models, it was seen that useful grinding conditions for industrial application could be easily determined.     

基于聚焦合成的砂轮表面三维重构方法

提出一种基于聚焦合成的重构砂轮三维地貌的新方法。利用显微镜物镜焦深范围有限,观察砂轮样本时不能聚焦清晰图像的特点,先采集同一区域的一系列聚焦在不同深度的图像,用图像聚焦评价函数进行图像叠合、比较,得到图像中不同位置的深度信息,最后通过高斯插值法得到砂轮表面的三维地貌。并根据所得到的三维地貌数据,对砂轮磨刃高度分布进行了计算。     

电火花修锐对金属结合剂CBN砂轮表面形貌的影响

采用电火花修锐方法对青铜结合剂锯齿形CBN砂轮在平面磨床上进行修锐实验,对修锐前后的砂轮表面形貌进行观测,修锐后砂轮的有效磨粒数、磨粒凸出高度明显增加,修锐时间以4~6h为宜;采用修锐后的砂轮对材料2T8/SK5进行了锯齿磨削加工实验,经测量,锯齿角度轮廓精度有较大提高。电火花修锐方法适合于金属基CBN砂轮的修锐。     

Wave-shift and its effect on surface quality in super-abrasive grinding

One of the problems limiting the use of many super-abrasive wheels is the wheel run-out, which cannot be effectively reduced below the value of several micrometers. Work waviness, generated by the run-out, depends on a wave-shift, overlapping the pattern of wheel revolutions in subsequent revolutions of the workpiece. A suitably selected wave-shift can result in a significant reduction of waviness. The present day machines are not equipped with wheel-work synchronisation control and wave-shift remains one of the random factors in the grinding process. The wave-shift phenomenon was investigated in the mid seventies in conjunction with the wheel unbalance of conventional wheels. The run-out of these wheels can be reduced to a fraction of a micrometer by suitable balancing and dressing so the wave-shift control, difficult to implement at that time, was not required. The present super-abrasive wheels exhibit significant run-outs and the advances in motor control make wheel-work synchronisation of sufficient accuracy possible.     

A survey of recent grinding wheel topography models

This paper provides a survey of grinding wheel topography models. Recent 1D, 2D, and 3D models are reviewed, and the important model components for a state-of-the-art 3D topography model are identified. Future directions for topography modeling are recommended and, based on this survey, a general modelling approach using grain size, shape, arrangement, and wheel dressing is proposed.     

A novel contact/non-contact hybrid measurement system for surface topography characterization

A novel surface profile measurement instrument, developed for the characterization of engineering surfaces, is presented. The instrument is of a hybrid type and is capable of contact and non-contact measurement, making it suitable for a wider range of applications. It has an optical displacement sensor and a stylus displacement sensor. For contact measurement, the vertical measurement range and resolution of the instrument are 1 mm and 10 nm, respectively. For non-contact measurement, they are 500 μm and 3 nm, respectively. The instrument has been successfully used for several forensic applications, demonstrating its unique flexibility and high reliability as a novel surface topography instrument.     

Model for surface topography prediction in peripheral milling considering tool vibration

This paper presents a model for the prediction of surface topography in peripheral milling operations taking into account that the tool vibrates during the cutting process. The model includes the effect of tool vibrations in the equations of the cutting edge paths, which are transformed into equivalent polynomial equations and solved for discrete positions along the feed direction by applying a standard root finder. Through this procedure, surface topography generation is simplified with respect to other models in literature. The model allows the topography, the roughness values and the form errors of the milled surface to be predicted. Cutting test results show good agreement with model predictions.     

A study on the effects of vibrations on the surface finish using a surface topography simulation model for turning

In this paper, a surface topography simulation model is established to simulate the surface finish profile generated after a turning operation. The surface topography simulation model incorporates the effects of the relative motion between the cutting tool and the workpiece with the effects of tool geometry to simulate the resultant surface geometry. It is experimentally shown that the surface topography simulation model can properly simulate the surface profile generated by turning operations. The surface topography simulation model is used to study the effects of vibrations on the surface finish profile. It is found that the vibration frequency ratio is a more important vibration parameter than the vibration frequency on the characterization of the surface finish profile. The vibration frequency ratio is the ratio between the vibration frequency and the spindle rotational speed.