Influence Of Forming Parameters On Forming Quality Of Double-pass Incremental Forming

Incremental sheet metal forming(ISF) is a new rapid prototyping technology, it does not need the design and manufacture of mold so that can save time and cost,and it is very suitable for product processing with automotive, aerospace and commercial applications. ISF is a promising advanced manufacturing technology. But there are many problems for forming complex parts by incremental forming technology,especially for the part with large forming angle which can be formed by multi-pass incremental forming technology. Therefore, considering the formability and efficiency of the forming technology in the paper, the multi-pass incremental forming was studied.First, a car taillight bracket was studied as a case, it was processed by single-stage incremental forming and double-stage incremental forming to show the feasibility of double-stage incremental forming technology. But the poor workpiece surface quality and springbcak of the inclined wall were found during the validation test.Then, the straight-walled cylinder was set as the research object to study the influence of process parameters on the surface quality and the springback, and numerical models were constructed to predict and optimize the springback angle and surface roughness of the straight-wall cylinder in double-stage incremental forming. It is found that angle interval has the maximum influence on the springback, followed by step size and feed rate. And the springback angle increases then decreases with the increase of the three process parameters. However, it will only increase or decrease with the increase of feed rate unless step size is kept as 0.25 mm and 0.75 mm respectively. At the same time, the same phenomenon happens between step size and springback angle when the feed rate value is set as 1000mm/min and 2000mm/min respectively. Then it is found that step size has the maximum influence on the roughness, followed by angle interval and feed rate. And roughness value will increase with the increase of ?z, ??and V. However, it will decrease first and then increase with the increase of feed rate unless step size is decreased to be 0.3mm. At last, the accuracy of the models was verified by a validation test.In addition to, to address the problem that there are some deformation region in the first-stage forming are no longer involved in the second-stage deformation process during a straight wall cylinder was formed, the numerical relationship between the preformed height in the first-stage incremental forming and the forming angle in thesecond-stage foming was obtained by theoretical analysis and was verified by the finite element numerical simulation technology. Then, the forming angle in the second-stage forming remained constant, the influence of the preformed height in the first-stage incremental forming on the quality of the double-stage incremental forming was studied.It is found that the minimum thickness of sheet metal parts increases then decreases with the increase of the preformed height in the first-stage incremental forming. With the increse of the preformed height in the first-stage incremental forming, the start point of the equivalent plastic strain in the second-stage forming gets greater and keeps the value unchanged for longer time, the range of the equivalent plastic strain gets smaller.In addition to, the smaller height in the first-stage incremental forming can decrease the springback. Finally, the simulation results were acknowledged by verification tests.