Research On Precision Grinding Method For Axisymmetric Revolving Curved Surface

With the demand for low-carbon green manufacturing, there is an increasing demand of injection molding to form parts. The mold technology has been an important sign to judge the level of manufacturing industry. The products performance is mainly determined by the mold surface, such as the curved surface of tyre and lamp mold. The traditional fine turning, polishing methods can not meet requirements of the processing efficiency and product performance. So, aiming for the manufacture of axisymmetric products, it has been a great practical significance in the engineering field to ensure the machining precision and efficiency.Based on analysis of profile feature of those typical revolving curved surface, a novel CNC grinding machine with Arc Envelope Grinding Method (AEGM) has been developed. Then, the corresponding grinding process is researched.Firstly, according to the peculiarity of AEGM, the envelope procedure of workpiece is analyzed, then, the interference between the grinding wheel and workpiece is analyzed based on the Euler formula. Besides, the relationship between the working width of grinding wheel and the wheel radius,the radius of curvature of workpiece, is studied, and as a result, a way to improve the wheel life is presented. And, according to the tangent line at any point on the surface and the wheel radius, a mathematical calculation way to find the wheel center against this point is presented, so as to establish a foundation for practical applications.A novel CNC grinding machine to grind the large-scale tyre revolving mold is developed (the largest diameter workpiece 01250mm). According to the feature of this tyre mold, the structure with two spindles is adopted. It can grind and polish the workpiece to improve the profile accuracy and roughness within only one set-up. Furthermore, another grinding apparatus based on a cylindrical grinder is also developed, and its accessories such as the diamond dresser, the acquisition and analysis system of grinding force, are set up. These can be used to study the grinding process with AEGM.Based on the theoretical model of grinding, the residual error on the surface with AEGM is studied. And the results show that residual height error is directly proportional to the feeding speed of wheel, and inversely proportional to the revolving speed of the workpiece. So the residual height error can be presented evenly by changing the feeding speed of wheel. As a result, a stable residual height error grinding method and stable material removal grinding method are presented. Based on the experiments, it shows that the fluctuating roughness all over the whole surface is about 35.06% with constant speed grinding, which is identical to the theoretical residual error 30.7%. However, it can be reduced to 11.33% with variable feeding speed, which verifies the feasibility.Higher form accuracy and better wheel surface topography can be obtained by using CNC diamond dresser. As for the wheel with the diameter of 0400mm and ross-section radius R28, its profile error after dressed is only about 0.01mm. Due to the problem of wheel uneven wear, the contacting time between the wheel of unit width and workpiece is studied. In order to solve this problem, another grinding method with variable feeding speed is presented, which can improve 25% profile accuracy of wheel.According to the deformation of workpiece during the grinding process, a new method to solve this problem based on the material removal principle is presented. Then, the workpiece is divided into 16 segments with different feeding speed. After grinding with this method, not only the profile error of workpiece can be reduced by 50%, but also reduce the roughness fluctuation effectively.The grinding force when grinding the curved surface and its influencing factors are studied. By analyzing the component force within time domain, and the grinding force ratio, the distribution characteristic of grinding force at the different places is researched. With the AEGM, Fy is the main component force, because it not only presents the larger amplitude, but also grows fastest. During the grinding process with AEGM, the contacting area between the wheel and workpiece is relatively small, as well as the value of grinding force. In the experiments, the grinding force with WA240H6V fluctuates within 5-55N, and when it exceeds 50N, the workpiece can be burned easily. And the distribution of grinding force at different curvature of workpiece is revealed.