Research On The Thick Sheet Fine-blanking Technology With Plane Blank-holder And The Prediction Of The Cut Surface

Fine blanking is a kind of precision machining craft developed on the basis ofordinary stamping. It is a new field in the development of blanking technology,which has characteristics of high efficiency, high quality, and low expenditure. Thefine blanking technology has been widely used in many fields such as automobile,precision machine and aerospace. However, general enterprises are unable to buyfine blanking presses because of the high price, where the application of fineblanking technology has been restricted. Therefore, it is an important tendency tomake this technology more and more popular by the development of fine blankingprocess on common press. In this paper, take the20steel with the thickness of5mmfor example, the systemic studies on the mechanism of fine-blanking process withplane blank pressing technology and the prediction of the cut surface wereinvestigated by a synthesis method such as dimensional analysis, FEM numericalsimulation and sample experiments.Firstly, the process and principle of fine blanking process were introduced.Besides, the characteristic of stresses in deformation zone and the hydrostaticpressure were analyzed. Two necessary conditions for fine blanking process weresmall clearance and three-dimensional compressive stress, which made the fineblanking process on common press available.In present study, DEFORM-2D was used as a tool to simulate the fine blankingprocess of the symmetry blank. The conditions with higher or lower pressure andcounter pressure were discussed respectively. The material flow and distribution ofhydrostatic pressure were analyzed in detail. Moreover, the cut surface quality wasinvestigated with Normalized Cockroft&Latham ductile fracture model. As a result,the vortex motion near the shear zone the higher pressure combinations revealedlower speed, and the hydrostatic pressure was increased accordingly. Thus the cutsurface of smooth zone revealed a large ratio because of its delay of crack evolution.With adding additional technological measures on common press, the feasibilityof fine blanking on common press was demonstrated, and the symmetric blanking diewith nitrogen gas springs was introduced for the following test. The research resultsreveals that the fine blanking process on common press is available by the novel diedesigned with nitrogen gas springs, which can obtain fine cut surface with highdimensional precision. Finally, based on the dimensional analysis method, the theorem was applied toderive the form of the smooth ratio of cut surface. Using the form associated withfinite element calculation, a numerical model of prediction the smooth ratio wasestablished. The prediction results show a good agreement with the existedexperiments, which certifies the validity and feasibility of our numerical model.