The Analysis About Accuracy And Stiffness Of The End-toothed Disc Of A Servo Turret

The servo turret is one of the important part of the numerical control machine tool. The performance of the machine tool is affected by the servo turret to a great extent. The end-toothed disc which is the key component of the servo turret is the research object, focusing on its accuracy and stiffness, in this paper. The main work can be concluded as follows:(1) A finite element model is established according to the servo turret of a company. The method with the coupling of rigid and flexible is employed to analyze the effects of the parts to the tangential stiffness of the servo turret. Then the importance of the end-toothed disc to the servo turret is proved.(2)The tooth profile angle and the tooth length ratio of the inner and outer discs of the end-toothed disc are set as the parameters to optimize the tangential stiffness of the servo turret. Then the relationship between tangential stiffness of the servo turret and the two parameters is obtained and the values of the two parameters are determined according to which the servo turret will have the maximal tangential stiffness.(3) The influence of the main tooth machining errors of the end-toothed disc, which is consisted of accumulated error of teeth distance, error of tooth width and error of toothed half-angle, on the indexing accuracy of the servo turret is analyzed. The mathematical relationship between tooth machining errors and indexing error of servo turret is established. A method is proposed for making tolerance of tooth machining errors, based on stochastic mathematics. In this method, tooth machining errors follow a normal distribution as the premise. And the target is that the pass rate of the indexing accuracy should be greater than 99.99%(the target can be changed according to the actual situation). In this paper, mathematical model of the pass rate is built and the tolerance of the main tooth machining errors is made.(4)The effect of the elastic deformation of the teeth to the accuracy of the servo turret is researched in this paper. Two discs cannot fully mesh and there are gaps between teeth because of the tooth machining errors. So, the deformation of the teeth according to the hydraulic pressure is analyzed to obtain the relationship between the elastic deformation and the teeth to the accuracy of the servo turret. The tolerance is revised according to the analysis.(5)Special test equipment about the repeated positioning accuracy of the servo turret is designed. Suitable tolerance clearance and the revolute are chosen in the equipment. The equipment can realize the moving of the micrometer while there is a part to ensure the accuracy of the equipment. The analysis of the error of the equipment is displayed in the paper and the result shows the correctness. The experiments about the repeated positioning accuracy of the servo turrets both domestic and overseas are conducted to evaluate the performance of the servo turret.(6)A method for measure the static stiffness of the servo turret is designed. The joint with ball is used in the method to make sure that the load is unidirectional, in a straight line and acting on a point. So, the method solves the problem of loading force offset. The experiments about the static stiffness of the servo turrets both domestic and overseas are conducted to evaluate the performance of the servo turret, too.