Research On The Fitting Method Of Descending VBHF By Gradient Drawbead

Blank-holder force is the important technological parameter in the process ofstamping. The appropriate blank-holder force can effectively improve the quality ofstamping. Due to traditional CBHF (Constant Blank Holder Force) remains the sameduring the stamping process,the large complicated stampings are difficult to achieveideal effect, such as automotive covering parts, especially with the promotion andapplication of new materials, such as high strength steel sheet, aluminium alloy plate,titanium alloy sheet and laser tailor-welded blanks in the field of stamping, thedeficiency of CBHF shows more obvious.Although variable blank holder force has powerful advantages in technology, it’svery difficult in engineering practical application. The difficulty is that the variableblank-holder force is a kind of process parameters, which need to achieve relying onpress by real time adjustment of blank-holder force in the process of stamping press.But now the existing large stamping press production lines use almost mechanicalpress of constant blank-holder force, which can’t achieve that blank holder forcechanges with stamping trip in real time in process of stamping. Although the existinglarge servo presses can realize variable blank-holder force, but the manufacturing costis high. Meanwhile, most large complicated stampings, such as automotive coveringparts, often appear parts defect in the process of stamping, partition variable blankholder force is needed in local control.A new method of fitting the descending VBHF, the most common type of VBHF,by gradient drawbead is put forth and it can achieve the same effect of descendingVBHF in the CBHF stamping process.The main work is as follows:1.First CBHF is employed to calculate the region where VBHF is applied, andthen, VBHF curve which is obtained by using optimization calculation.2.The VBHF curve derives from relationship between the constrained force ofVBHF on the blank and the travel distance of the blank edge and the constrained curveof gradient drawbead, by which the parameters such as the number, location andmagnitude of the constrained force of gradient drawbead can be obtained, is fittedbased on it, the method can be applied in not only the whole VBHF, but also thepartition. 3. The variation in thickness of formed parts is seen as optimized objectivefunction, Using box-shaped pieces to verify the based on fitting method of descendingVBHF by gradient drawbead, comparing with the optimized calculation results ofconstant pressure variable force, and comparison analysis results show that the basedon fitting method of descending VBHF by gradient drawbead can improve the qualityof sheet metal stamping with an example.Through the above methods，the fitting Descending VBHF by Gradient Drawbeadhas a certain guiding significance to improve the quality of sheet metal formin g.