Research On Quick-point Grinding Mechanism And Workpiece Surface Topography

Quick-point grinding technology is highly efficient and versatile, combining with super hard abrasives, CNC technology and high/super high speed grinding technology. A very slim CBN or diamond grinding wheel is used in quick-point grinding. A tilt of the grinding wheel axis relative to the horizontal workpiece axis creates a relief angle that reduces the contact zone between the grinding wheel and the workpiece from a contact line to a contact point. It is possible to perform plunge-cut grinding, thread grinding, form grinding, etc. of components in one clamping. To date in China, not very much theoretic or experimental research has been done on subjects of grinding mechanism, quality control, grinding process of quick-point grinding.Surface micro topography of workpiece is generated through interference effect of ground workpiece and grinding wheel. In grinding process, as grinding wheel moves, workpiece surface materials in the contact zone of workpiece and grinding wheel are gradually removed by cutting effect of numerous abrasive grains distributed on surface of grinding wheel. Performance of components are depends largely on texture characteristics of surface micro topography, which can be parametrically evaluated by roughness, texture direction, and observed by SEM or3D profiler. It is necessary to decorate and improve workpiece surface texture to obtain components that own high reliability and to realize quality control of components.A method of numerical simulation analysis was used to do theoretical research on grinding mechanism of quick-point-grinding. According to grinding craft characteristics, the quick-point grinding angle a was taken into consideration in this paper. The existence of angle a made quick-pointing different from regulate outside round grinding in processes of workpiece material removal and surface topography formation. To find out how angle a influence these two processes, three models of interference between grinding wheel and workpiece were established. A workpiece removal model was established to do a kinematic analysis of one single abrasive grain in quick-point grinding. Two surface topography formation models, separately based on continuous profile curves and prism cutting grooves, were established to find out relation between surface roughness parameters and angle a. In the three interference models described above, wheel diameter ds workpiece diameter dw wheel peripheral velocity vs and workpiece peripheral velocity vw. were separately replaced by their equivalent in condition of quick-point grinding. In use of MATLAB, numerical simulation analysis was carried out based on the mathematical models derived from the three models. Actual process parameters, grinding wheel parameters and abrasive grain parameters were substituted into the mathematical models for numerical simulation. In addition, a mathematical model was established to modify surface texture direction angle, considering both angle a and axial feed speed. An empirical formula of surface roughness was given as a reference and supplement of above research.Summarizing theoretical research of this paper, the details of the study are as following:(1) Maximum cutting depth amax(maximum undeformed chip thickness) decreases as angle a increases. Lower maximum cutting depth amax will reduces normal grinding force Fn, temperature in grinding zone and has a good influence in improvement of quick-point grinding precision. Further, different types of chip formation conditions and boundary conditions were discussed based on relation of maximum cutting depth amax and grinding depth△, and relation of length of cutting path Lk and continuous cutting edge feed s.(2) Length of cutting path Lk of one single abrasive grain increases as angle a increases. Maximum grinding angle εmax decreases as angle a increases. For these two reasons, abrasive grain cutting depth of quick-point grinding will decreases as angle a increases. This is consistent with the relation of maximum cutting depth amax and angle a.(3) According to two surface topography formation models, separately based on continuous profile curves and prism cutting grooves, both surface roughness parameters Ra and Ry decreases as angle a increases. Continuous cutting edge per unit area Ce increases as angle a increases. The relation of Length of cutting path Lk of one single abrasive grain and angle a is one reason for the increase of continuous cutting edge per unit area in quick-point grinding. A smoother workpiece surface and a lower surface roughness can be achieved. A higher grinding efficiency can be achieved for the increase of workpiece material removal rate.