| With the rapid development of industry and the increasing demand for the shape of the plate,especially for the three-dimensional complex surface parts.Traditional forming processes such as stamping are suitable for mass production of the surface parts,but not for the three-dimensional complex surface parts with small batches and high flexibility.Considering factors such as production cost and process complexity,flexible forming technology is used to process the three-dimensional surface parts as far as possible,such as multi-point die forming,incremental forming or spinning forming technology,but there are still some difficulties.In order to better meet the needs of production automation and product individualization,a multi-point spinning forming method is proposed,and the forming equipment and process of this technology are studied.Multi-point spinning process is a new low-cost and high-precision surface processing method,which combines the characteristics of multi-point die forming,incremental forming and ball spinning forming.The forming theory is to use the multi-point die composed of cluster steel balls to form a counter-pressing mode against the sheet metal by controlling the bottom die of the forming part shape,and to drive the steel balls to rotate disorderly so that the sheet metal gradually fits with the bottom die surface,and finally to form a three-dimensional surface part.The bottom dies of different profiles can be replaced to form the complex surface parts of revolving body or non-revolving body.Therefore,the multi-point spinning technology has high application and value in the manufacture of small batch and high precision surface parts.The specific research contents and conclusions of this paper are as follows:1.Firstly,the forming theory of multi-point spinning process is introduced,and the stress,strain and thinning rate of sheet metal during multi-point spinning process are explored.The influences of process parameters such as bite angle and steel ball size on the forming process are analyzed.The track and force of steel balls in the multi-point spinning model are also calculated theoretically,which provides a theoretical basis for simulation and experiment.2.Firstly,the three-dimensional model of synchronous spinning and asynchronous multi-point spinning is established,then the distribution and variation of stress and strain in the forming process of the two processes are studied respectively.Finally,the comparative analysis of the two processes is carried out,and it is concluded that the stress and strain of synchronous spinning are larger and more uniform,while the spring backs of asynchronous spinning is small and the forming quality of asynchronous spinning is high because the residual stress of the formed part is fully released during the ball spinning process.3.The forming simulation of balls with different sizes and feed ratios in the synchronous multi-point spinning model is carried out,and the stress,strain and thickness of the formed parts are studied.The results show that the distribution of stress,strain and thickness is more uniform under the action of mixed steel beads,and the forming quality is the best.With the increase of the feed ratio of steel beads under loading,wrinkling increases and the forming quality decreases.4.The forming simulation of balls with different sizes and loading turns in asynchronous multi-point spinning is carried out,and the stress,strain and thickness of the simulation results are studied.The results show that the forming effect of 3mm steel balls is the best,and with the increase of loading turns,the stress value decreases gradually.At the same time,the uniformity of stress and strain distribution increases,and the forming quality improves obviously.5.The multi-point spinning forming equipment is introduced,and experimental research on different technological parameters is carried out.By comparing the results of experiment and simulation,it is concluded that the thinning rate of forming parts is consistent with the precision of closing die and the simulation results,and the forming quality is very high.Thus,a new and effective forming method for the three-dimensional surface parts is provided. |
