Grinding Wheel Topography Research Articles

Theoretical and Experimental Research on Generation Mechanism of Grinding Wheel Topography by Laser Dressing and 3D Laser Scanning

Theoretical and Experimental Research on Generation Mechanism of Grinding Wheel Topography by Laser Dressing and 3D Laser Scanning

Optimization design of grinding wheel topography for high efficiency grinding

In view of the limitation of prior topography models of the grinding wheel, a new method for optimization design of grinding wheel topography is advanced. The optimization model can be used to optimize the topography in accordance with machining demands and grinding parameters as well as optimize grinding parameters in accordance with the topography and machining demands. Furthermore, a superabrasive slotted grinding wheel is designed as a practical application of the optimization model and a creep-feed deep grinding experiment is carried out to verify the optimization results.

研削面プロフィル創成シミュレーションから考察した砥石面トポグラフィの具備条件

The purpose of this study is to analyze the requisite conditions of grinding wheel topography for improving surface finish. In this report, a wide variety of wheel surface topography is examined with the previously developed simulation in which measured distribution of mounting spring constant, dimensional position and shape of abrasive grains are considered. The simulation makes clear that the necessity of wheel surface topography for the fine ground surface profile are to have the extremely small spring constant of grain mounting in a very top surface and its higher average and variation in the inner position from the wheel surface. In addition, to true up the grain edge position and to make a pointed edge of grains flat are necessary. The knowledge obtained from these analysis may be an important guideline in manufacturing, dressing and truing a grinding wheel.

画像解析による砥石作業面の評価 （第２報） 研削過程における砥石作業面変化の追跡測定

This study deals with the post-process measurement of the grinding wheel topography by means of a newly improved image processing system. In this system, grinding wheel is driven by the high-power electric servomotor with a built-in rotary encoder so that both grinding operation and consecutive measurement of the individual abrasive grains by the accurate wheel positioning are possible. The contraction/expansion process is useful for the separation of adjacent grains. The dark field microscopy is effective in order to extract monochromatic CBN grains from the lustrous metal bond. This system is applicable to the practical grinding operation with resinoid and metal bonded superabrasive wheels with a good degree of accuracy and efficiency. In grinding normally sintered silicon nitride with the resinoid-bonded diamond wheel at a given grinding condi-tion, this system reveals that cutting-edge ratio decreases rapidly due to the micro-fracture of grain tips at the transient stage just after truing/dressing, and it increases slightly with the promotion of attritious wear under the successive steady state. This phenomena are explained by the fact that abrasive grains are damaged during truing/dressing operation.

Kinematic Simulation for Analyzing and Predicting High-Performance Grinding Processes

In grinding technology, the application of superabrasives and increasing demands for higher productivity and higher quality require an appropriate selection of optimum set-up parameters. Therefore, the development of analytical or empirical models for reliable prediction of machining performance and work results is a key issue. This paper presents a comprehensive concept for process modeling which provides a software tool for analyzing and designing high performance grinding processes, using the method of kinematic simulation. On the basis of synthetic 3D-models describing the macro- and micro-geometry of the grinding wheel and the workpiece, together with mathematical models describing the relative motions and kinematic engagement conditions, grinding processes can be reproduced as the cumulation of multiple grit engagements. The proposed simulation tool allows the generation of optional grinding wheel topographies and the analysis and prediction of the machining performance and work result for different grinding techniques, taking into account thermo-mechanical and dynamic effects in the contact area.

Mechanical and thermal response of a nickel-base superalloy upon grinding with high removal rates

The formation of a plastically deformed and a heat affected zone during grinding of superalloy IN738LC with a high depth of cut but slow work speed (creep feed grinding) was investigated. In order to obtain a better understanding of material removal mechanisms, the alloy strength and contact temperatures under typical machining conditions were evaluated. Temperature calculations comprised both the stationary equilibrium between global heat input and heat transfer to the coolant, as well as flash-like pulses at small contact spots. As a result, it was found that local melting at contact spots seems to be a rather common mechanism during grinding of superalloys, leading to so-called white layers which can easily be observed on metallographic cross sections. Grinding wheel topography has a significant influence on the maximum contact temperature and the width of the white layer. Sufficient cooling is very essential in limiting the width of the molten zone to few micrometers, which then is not critical in respect to mechanical properties. On the other hand severe damage was observed after creep feed grinding without coolant.

砥石作用面のフラクタル構造の形成要因

This study has been done for the purpose of understanding the mechanisms by which the grinding wheel topographies are formed. The irregularity of distribution of grain tips over the wheel surface and the complexity of their morphology can be characterized by the fractal dimensions. Therefore, it was investigated how the fractal dimensions correlated with the dressing parameters and the composition and properties of wheels themselves. Based on the experimental data, the models adequate to describe the mechanisms were built by the technique, which is called “group method of data handling”. On the basis of the obtained models, the following conclusions could be drawn. (1) The dressing at bigger depth of cut on the harder-grade and more open wheel results in the increased morphological complexity of grain tips. (2) The finer dressing on the denser wheel results in the decreased irregularity of grain tips distribution.

A Comparison of Topographic Characterization Parameters in Grinding

Parameters for characterizing topographies and a method of selecting these parameters are investigated. Conventional and scale-sensitive fractal parameters are tested for cross-correlations, ability to differentiate process variables and ability to relate grinding wheel topography with ground surface topography. Surfaces were ground using different wheels, dress leads and removal rates. Profiles were acquired by contact stylus profiling parallel and perpendicular to the grinding direction on the grinding wheels and the ground surfaces. The conventional height parameters tend to be more cross-correlated than the spacing and fractal parameters. No parameters in this study could differentiate the process variables or could relate wheel and workpiece topographies in all situations. The waviness height (Wt) was the best for differentiating process variables, and a scale-sensitive fractal-based parameter, the smooth-rough crossover (SRC), was best at relating workpiece and wheel topographies.

The application of three-dimensional surface measurement techniques to characterizing grinding wheel topography

Two differing grinding wheels were dressed under similar conditions and their resulting surface topographies were measured using three-dimensional contacting profilometery techniques. Through the use of newly developed three-dimensional numerical surface characterization parameters, aerial estimations of the number of static cutting points and static cutting grains were made, and the results compared with those obtained by other workers. The techniques used proved useful for both qualitative and quantitative analysis of the wheel topography. The results obtained compared favourably with those of other workers. The effects of sampling strategy on the results are discussed and optimum sampling conditions suggested.

A model for the topography of diamond grinding wheels

A mathematical model is presented to characterize the topography of a freshly dressed resin/metal bonded diamond grinding wheel. The planar grain density, the area due to exposed abrasives and the abrasive protrusion height distribution of a wheel are estimated with regard to the grit size and volumetric concentration of the abrasives. The model indicates that the protrusion height is approximately uniformly distributed and the percentage of area due to exposed abrasives on the wheel surface is independent of the abrasive grit size for a particular concentration.

Monitoring of Grinding Wheel Wear

A new, optical sensor has been developed in order to monitor the cutting capacity of grinding wheels. This sensor is based on the principle of triangulation. For the investigation of the grinding wheel topography even during the grinding process the sensor has been mounted at the opposite side of the working area of an external grinding machine. The output signals of the sensor are processed by a digital data acquisition system controlling the position of the sensor and calculating different parameters to describe the state of wheel wear. These parameters take various aspects of macroscopic and microscopic wheel wear into consideration. Some results which have been obtained using a corundum grinding wheel are presented. These results were achieved during the rotation of the wheel at cutting speed.

A New Approach for Investigating Dynamic Effects in Grinding

Dynamic effects in grinding can be investigated by using a mathematical model which describes a closed loop consisting of frequency responses. Each frequency response represents the dynamic behaviour of a component of the machine-wheel-workpiece system. Of importance for the dynamics are among others the physical mechanisms taking place within the wheel-work-interface. These phenomena are usually idealized by what is called the dynamic contact length or by the dynamic material removal rate. An alternative to these two approaches is reproducing the dynamic processes within the contact zone cutting edge by cutting edge with the aid of computer simulation. Among others this approach offers the advantage that plastomechanical processes at the engaging cutting edges and the friability of the latter as well as the grinding wheel topography can be taken into account directly. It will be shown how the frequency responses of the wheel-work-interface processes can be simulated. These calculations are carried out in time steps. The resulting time dependent frequency responses can be used to analyse the dynamic stability of the machine-wheel-workpiece system.

Internal Grinding of High Strength Ceramic Workpiece Materials with Diamond Grinding Wheels

With increasing requirements for highly stressed components in respect to wear and friction behaviour, temperature stability and resistance to aggresive chemicals, ceramic materials have many advantages in comparison to metals. Beside these characteristics, high quality in dimension, shape and surface is often required. Ceramic components therefore often have to be ground or lapped. Up to now the influence of machine setting conditions and grinding wheel specifications on the grinding process has net been investigated very much. Therefore results about internal grinding of B 4 C, SiC, Al 2 O 3 , and Si 3 N 4 (hot pressed, reaction sintered) with resinoid and metal bonded and as well electroplated diamond wheels are explained. Results about G-ratios, grinding forces, workpiece roughness and shape deviations are described as function of cutting speeds, feed velocities, material removal rates and speed ratios. The dressing process of diamond wheels in combination with jet-sharpening is shown. The grinding wheel topography is described as function of sharpening period, jet pressure and abrasive flow rate.

Characterization and Analysis of Grinding Wheel Topography as a Stochastic Isotropic Surface

The grinding wheel topography is characterized and analyzed as a stochastic isotropic surface. An explicit procedure is given to check the assumption of surface isotropy. Geometric statistical properties such as the number of active cutting points per unit area, the ratio of real to apparent area of contact, and the mean and root-mean-square rake angle of ten grinding wheels are calculated. Using the characteristic parameters as responses, the relative contribution of the wheel grit size, hardness, and structure to the total wheel topography is quantified by factorial design analysis. The procedure of characterization is also applicable to other homogeneous stochastic isotropic surface.