| Ball screw is a kind of precision transmission components,and it can realize the conversion of rotary motion and linear motion and the transmission of force.Due to the advantages of high transmission efficiency,high positioning accuracy,small friction coefficient,great stability,etc.,ball screw is widely used in precision machine tools,precision instruments and other fields.As mechanisms such as robots and industrial manipulators pursue higher transmission speeds,it is particularly vital to improve the feed speed of ball screw.Generally,the method of increasing the lead of ball screw is used to increase the feed speed of the ball screw.The high-lead ball screw comes into being.However,as the lead of the ball screw increases,the difficulty of precision manufacturing the raceway of the high-lead ball-nut increases.The manufacturing quality of the high-lead ball-nut is the key to ensure the excellent performance of the high-lead ball screw.Therefore,it is of great significance to study and improve the precision manufacturing technology of the high-lead ball-nut to improve the technical level of China’s equipment manufacturing industry.In this context,this thesis focuses on the topic of "Research on key technologies for precision machining of high-lead ball-nut".1.In this paper,the shape and key geometry parameters of the ball-nut are introduced at first,and the equation of the ball-nut helical surface is derived in detail by using the principle of differential geometry under the condition that the normal cross-section of the helical groove is known.Next,the key mathematical model of turning helical surface is described.The derivation process of the contact condition formula between grinding wheel and ball-nut,the mathematical model for calculating the grinding wheel and the model for reversely calculating the helical surface of the ball-nut are given.It lays a theoretical foundation for the following research on the precision manufacturing of the high-lead ball-nut.2.In order to study the high-lead ball-nut layered envelope cutting technology,the paper firstly introduces the basic principle of envelope cutting,secondly introduces the envelope cutting tool position equations and the optimization strategy was proposed according to the interference of tool position.In order to improve the machining quality and efficiency,the methods of the optimization of machining step and the design of relative position of cutting edge are proposed.Then the fast circumferential positioning scheme of ball nut was designed to realize symmetric raceway through the radial hole.Finally,the high-lead ball-nut precision turning software is developed based on the above theory to generate line-by-line CNC precision turning instructions that can be read by machine tools.3.In order to study the interference grinding technology of high-lead ball-nut,the paper introduces the solution process of the forming wheel and proposes the method of selecting the installation parameters of the forming grinding wheel under the condition that the ball-nut and the wheel shaft do not interfere.According to the analysis of an example,the changing trend of the change of grinding wheel installation parameters to the solution of grinding wheel truncation is revealed,and the "bad points" of grinding wheel profile are analyzed and optimized.Then the analytical method is used to verify the optimum grinding wheel profile.The results show that the method can obtain better ball-nut profile.In order to compensate the process system error,the error compensation method of high-lead ball-nut based on wheel redesign is proposed.Finally,according to the above theoretical calculation,the interference grinding software of high-lead ball-nut is developed.4.The virtual simulation and manufacturing tests were performed on the high-lead ball-nut.Based on the secondary development of UG GRIP,the paper designs interference grinding simulation and envelope turning simulation of high-lead ball-nut to verify the correctness and applicability of the established theory and software.Finally,a high-lead ball-nut envelope turning test was carried out.The test results show that the layered envelope turning method proposed in this paper can ensure the high-lead ball-nut inner raceway to meet the accuracy requirements. |
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