Research On Spinning Precision Of Die-less

Die-less molds,which are not limited by core molds,can process various curved workpiece lines,increasing the flexibility of spinning products,and are particularly suitable for the manufacture of reduced diameter products,thus receiving widespread attention.However,due to the lack of support and constraints from specific core molds in coreless spinning,the stress situation during the forming process is more complex.The blank is in a free deformation state during the forming stage,resulting in large overall and local rebound of the workpiece,which further affects the forming quality and accuracy of the workpiece.In this paper,the precision of coreless die spinning is studied through experimental and simulation methods.Based on the response surface experiment,the precision of conical parts without core die and with core die is studied,and the variation law of the precision of the two forming methods under different process parameters is analyzed.The research results show that the maximum precision deviation(standard deviation)of the spinning workpiece with and without mandrel occurs at the fillet transition of the mandrel and the edge of the flange.Within the range of selected process parameters,for die-less spinning,the influence of forming angle and diameter ratio on accuracy deviation is highly significant,the influence of feed speed on accuracy deviation is significant,and the influence of mandrel speed on accuracy deviation is not significant.For mandrel spinning,the feed speed and mandrel speed have a significant impact on the accuracy deviation,and the interaction of the clearance between the mandrel and the roller,the rotation speed and the clearance between the mandrel and the roller has a significant impact on the accuracy deviation.Based on the simulation,the forming process of conical parts without core die and with core die is studied.The variation rules of equivalent stress,circumferential stress,radial stress and equivalent strain in the forming process of the two forming methods are summarized through the numerical simulation results.The results show that the distribution of deformation stress and strain in different positions of spinning without mandrel is similar to that of spinning with mandrel.The stress distribution law of the workpiece in the initial rotation,stable rotation and final rotation stages is obtained.On this basis,three schemes to improve the forming accuracy are proposed.According to the simulation results,three methods to improve the accuracy and dimensional deviation of the die-less conical parts are proposed: multi-pass forming method,trajectory compensation method,and 3D printing die method.Based on the experience of the above methods,a combination method of multi-pass and trajectory compensation is designed.It is found that these four forming methods can improve the forming accuracy of the workpiece.Among them,the forming method of 3D printing die has the best effect on improving the accuracy deviation,followed by the method of combining multi-pass and track compensation,followed by the method of track compensation,and finally the method of multi-pass forming.For the workpiece with third-order Bessel function curve,the accuracy deviation of the workpiece with concave-convex trajectory curve is significantly better than that of single-pass spinning without mandrel by using the combination of multi-pass and trajectory compensation,which shows that the two combined forming methods can also significantly improve the accuracy of the workpiece with the generatrix as a curve.