Study On The Method And Experimental Of Incremental Forming By Non-continuous Contact Between Tooland Sheet Metal

Incremental sheet forming is especially suitable for the development of new product,the production of small batch and flexible manufacturing of sheet metal parts because it does not need a bolster or just needs a simple bolster.It has a wide range of applications in automotive,aerospace,building and biomedical devices.Due to the limitation of forming limit angle in single pass increental forming,improving the perfomance of incremental sheet forming is always an important research topics in this field.In order to improve the formability of sheet metal in incremental forming,a new incremental forming by non-continuous contact between tool and sheet metal is proposed in this paper:incremental forming by equal diameter spiral tool path.The basic idea of this method is that in the forming process,the tool feeds at each layer while making an equal diameter spiral movement around the forward direction.By controlling the screw parameters,the material flow between different regions and the thickness of different regions can be realized,which is expected to improve the sheet metal formability.This paper expounds the idea of this method,gives the steps of tool path transformation in detail,deduces the mathematical equation of tool path point space transformation in each step,and verifies the feasibility of this method by experiment.In this paper,the variation of wall thickness and the influence of technological parameters on the uniformity of wall thickness in incremental forming by equal diameter spiral tool path are studied by measuring the variation of wall thickness on the side of cone cup with fixed angle and taking the theoretical wall thickness and the uniformity of wall thickness as evaluation criteria.The results show that the wall thickness of incremental forming by equal diameter spiral tool path conforms to cosine law.Under counter-clockwise machining,the side wall thickness increases obviously with the negative spiral motion of the tool head,and the formability is higher than that with the positive spiral motion of the tool head.In this case,the larger the helical radius r,the smaller the helical lead s,the better the formability,and the overall formability of equal-diameter helical incremental forming is higher than that of ordinary incremental forming.In the aspect of low surface quality and forming accuracy,the size of helical radius r has little effect on the surface quality of workpiece.In counterclockwise machining,with the increase of helical radius r,the precision of workpiece is improved first and then decreased by the positive helical motion of the tool head,and the forming precision is continuously improved by the negative helical motion of the tool head.Cheng s has a great influence on the surface quality.With the increase of the spiral lead s,the surface quality of the tool head becomes worse under the two motion states,and the accuracy also becomes worse.furthermore,in view of the fact that ultrasonic incremental sheet metal forming can also improve the sheet metal incremental forming performance effectively,the related research is still in the initial stage yet.This study based on the basic principle of ultrasonic-assisted forming,designing a set of ultrasonic-assisted incremental forming device independently,constructing a laboratory prototype of ultrasonic-assisted incremental forming.And The feasibility of ultrasonic-assisted incremental forming is verified by forming one-word groove,while the experimental results also verifide that under the condition of high temperature grease lubrication,the larger the feed rate and the faster the processing speed,the higher the formability of sheet metal.