Normal Grinding Force Research Articles

プランジ研削における切込み過程の研究 (第1報)

In the grinding process the effects of grinding conditions on the accuracy and quality of the work-piece are not clear sufficiently. Those are the main difficulty to promote the efficiency of the grinding process. From that viewpoint this study takes note of the plunge grinding which is the representative grinding method, and analyzes the grinding phenomenon theoretically and experimentally. The aim of this study is to decide the ideal in-feed curve which fulfills the requirements of high efficiency, accuracy and quality based on the distinct basis of evaluation. In this report the formulation of real cutting depth, normal grinding force and wheel wear were conducted and a mathematical model of the plunge grinding was constructed. Then making use of this model the size generation process and the process changes of grinding phenomenon were analyzed quantitatively under some in-feed processes and a fundamental theory was developed to obtain the ideal in-feed curve.

Bivariate Time Series Analysis of the Effective Force Variation and Friction Coefficient Distribution in Wood Grinding

A new technique for analyzing the normal and tangential grinding force is presented, which can be used to extract the dynamic characteristics of the grinder structure, the work material, and measurement transducers from experimentally measured forces. The technique involves developing bivariate time series models from the data which represent the dynamics imparted to the random force variation at the wood-stone interface. Removing the dynamics allows a simple model for the grinding force to be postulated, from which the statistical distribution of the resultant force and friction coefficient can be determined. Two sets of data from an experimental wood grinder are analyzed. Based on independent experiments, the frequencies in the measured normal and tangential forces can be related to factors other than the true grinding forces. The methodology developed is used to remove these dynamic effects and find the force and friction coefficient distributions. The mean value of the friction coefficient determined with this method appears to be more sensitive in detecting changes in friction for different grinding conditions.

An Orthomorphic Rheological Model of the Grinding of Wood

Grinding wood to produce a pulp for papermaking is termed mechanical pulping. To better understand and control this grinding process, a rheological model is postulated that accounts for the elastic and viscous properties of the wood in two orthogonal directions. From the model it is shown that these properties impart a phase lag between the normal and tangential grinding forces, and experimental measurements collected under five grinding conditions agree with the model prediction. Based on measured pulp properties, the grinding condition with the minimum phase lag yielded the best quality pulp, suggesting that the calculated phase lag could be used as a quality control tool to eliminate conventional pulp testing during production or as a feedback signal to control grinder operation in the mechanical pulping process.

Some factors affecting the efficiency of individual grits in simulated grinding experiments

This study of the mechanics of grinding used a single grit approach and involved the development of a high frequency dynamometer to measure grinding forces at speeds of up to 37 m s −1. Experiments have been carried out using idealised cutters to simulate abrasive grits; the grinding forces, the grinding coefficient and the specific energy were measured for a wide range of cutting speeds and workpiece hardness. For a grit of a given geometry the main factors affecting efficiency were found to be the hardness of the workpiece and the cutting speed. A theoretical model of the grinding process has been developed which enables normal grinding forces to be predicted from the flow pressure of the workpiece and the geometry and cutting efficiency of the grit. The implications of the work are discussed with particular reference to surface finish.

精密円筒プランジ研削における砥石寿命判定の一方法

This paper describes a new criterion to determine the wheel redress life in fine cylindrical plunge grinding. In most cases of dressing using a single point diamond dresser a thread is generated on the wheel face, and the thread, changing its form with the lapse of grinding time, finally disappears. In fine cylindrical plunge grinding the wheel face profile is printed on to the workpiece surface and the same thread is generated on it. The wheel redress life based on the new criterion is determined as follows : changes in the ground surface profile with the lapse of grinding time are pursued by means of spectrum analysis, and when the thread caused by dressing disappears, it is considered that the wheel has just reached its wheel redress life. A few experiments were carried out to compare the new criterion with the criteria heretofore in use, and the new criterion gave almost the same wheel redress lives as those based on the normal grinding force or the radial wheel wear.

研削中の工作物の振動について

The relation between amplitude and frequency of workpiece in external-grinding is analysed in a single degree-of-freedom system with contact and grinding stiffnesses and examined experimentally in plunge-grinding. As a result of analytical investigation it is derived that with increase in amplitude the frequency of workpiece decreases, slightly in smaller amplitude due to the property of contact stiffness, and considerably in larger amplitude due to the loss of contact between workpiece and grinding wheel for a part of the cycle of vibration of workpiece. Then, applying Laser projected to the cutting zone tangentially to workpiece and grinding wheel, the phenomenon of this loss of contact can be directly observed in considerably larger amplitude of workpiece than the depth of cut. And from the results of plunge-grinding tests it can be seen that experimental values about amplitude and frequency of workpiece are relatively close to the analytical values, especially at the smaller depth of cuts. In this report the grinding stiffness is determined from the steady normal grinding force in plunge-grinding under various depth of cuts.

ベルト研削における加工条件の選定

In this paper, it is defined that the failure criterion of coated abrasive belts under constant force plunge grinding is the time when the stock removal rate is reduced to zero and under fixed feed plunge grinding is the time when the normal grinding force reaches to the specified value. Then the tool-life equation is derived theoretically on the basis of the metal removal mechanism and wear process of coated abrasive belts which have been reported in the previous papers. This tool-life equation may be considered to be the one which introduces the initial wear into the Taylor equation. And then stock removal during a belt life, the machining cost and the time to change belts are theoretically and experimentally investigated. As the result, optimum conditions of belt grinding on the total stock removal and the machining cost are reasonably determined.

平面研削中の工作物の熱変形と研削後の形状誤差

This paper describes some experiments with the thermal deformations of workpieces, caused by the heat generated in surface grinding, and their influences upon the geometrical accuracies of finished workpieces. The thermal deformations and the temperature distributions of workpieces have been measured directly by using strain gauge type pickups and thermocouples. The straightness of finished workpieces have been measured and compared with the.deformations during grinding. The influences of some parameters on the thermal deformations are investigated. From this study, the following results are obtained. The temperature differences are produced between the top and bottom surfaces of workpieces during grinding operations. Consequently, the workpieces are deformed into convex shape, in addition to the simple expansion in the direction of thickness. As the result, the profiles of finished work-pieces become concave. The cooling effects of grinding fluid are remarkable, but insufficient. The suppressing effects of the electromagnetic chucks and the normal grinding forces on the.thermal deformations are comparatively small.

研削ベルトの研削機構

The purpose of this paper is to investigate the metal removal mechanism of coated abrasive belts considering the wear of active grains. For this purpose, following assumptions are applied. (1) The new grain cutting edge is a conical shape and the worn one is the shape of a truncated cone. (2) Grinding force F is resolved into the normal grinding force FN and the tangential grinding force FT. FN is composed of FNC (cutting component of FN) which is the sum of normal forces acting upon rake faces of grain cutting edges and FNS (sliding component of FN) which is the sum of normal forces acting upon worn grain flats. Similarly, FT is composed of FTC and FTS. Under the above assumptions the relation among the percent wear flat area, grinding force and rate of stock removal is theoretically developed. By experiments, C (value of FTC/ FNC), KS (specific grinding force), e (exponent of the size effect), pm (average contact force intensity between wear flats of abrasive grains and workpiece) and μ (coefficient of friction between wear flats of abrasive grains and workpiece) are obtained and discussed. As the result, the metal removal mechanism of coated abrasive belts is considerably made clear.

研削砥石の減耗状態の評価法

The wear process of grinding wheels is discussed by the following methods.1) The value of tan a is calculated by measuring the normal grinding force, where a is the half apical angle of the cone assumed to keep with ability of grain tips. On the basis of this result, the variation of the mean shape of grain tips is discussed.2) The profile curve of mild steel surface ground under constant conditions is measured by use of a tracer instrument. By measuring the Abbott's bearing curve and the maximum height of its profile, the variation of the number of grain tips in a wheel is discussed.3) Autocorrelation function is calculated for the above profile curve. On the basis of this result, the variation of the pitch of grain tips is discussed.4) The number of times that the above profile crosses the center line is counted. On the basis of this result, the variation of the shape and the pitch of grain tips is discussed.

Preparation of phase diffraction gratings by vacuum evaporation.

This experimental study deals with the effect of machine structural loop stiffness on grinding of ceramics. The objective of the study is to investigate how the loop stiffness affects grinding forces, wheel actual depth of cut (ADOC) and workpiece strength. A compliant workholder is specifically designed and attached to a precision grinder to simulate grinding machines of various compliances so that the effect of machine loop stiffness can be isolated under otherwise identical conditions. Silicon nitride is used as workpiece material and ground with diamond wheels of two bond types and three grit sizes at machine loop stiffness of four different levels. The ground workpieces are assessed in terms of residual workpiece strength, grinding damage, grinding forces, and ADOC. Theoretical analyses are given to indicate that machine loop stiffness can affect on normal grinding forces and workpiece strength. A discussion is provided to reveal how residual workpiece strength is affected by residual stress and grinding-induced damage.