Research On Silent Blanking Based On Mechanical Press Of Servo Drive

Blanking is one of the most important stamping processes, not only can it be the preparation for the complex stamping, but also it can get work pieces with a certain accuracy directly. There are lots of difficulties to study sheet metal blanking process since the deformation is limited in a tiny area of sheet metal and ends with fracture. Moreover, as most blanking works on traditional crank presses, along with the fixed dynamic characteristics, and the limitation of the movement characteristics with stamping equipments, the studies on blanking focused chiefly on die structure, craft parameters and so on while the study about the effect of dynamic characteristics of slide on the blanking process is unreported.Sheet metal blanking ends with the fracture, and thus the elastic energy accumulated in the press body releases with the fracture, bringing severe vibration, great noise and damage to the die and equipments. Up to now, passive damping, for example adding vibration-reducing components between the press base and the ground, has mainly been adopted to deal with the noise generated by stamping process. Though this method separates the vibration from the ground so as to partially reduce the vibration and noise, it fails to eliminate the noise completely. Ever since the early beginning of this century, servo presses has come out and brought us hope to solve this problem. The presses are driven by AC servo electric motors, and the dynamic characteristics of the slide can be adjusted freely. The releasing time of elastic energy accumulated during the blanking could be altered to guarantee the elastic energy to be completely released before the fracture so as to reduce the vibration maximally, realizing silence blanking. This method could be called active vibration reducing.Starting from the finite element theories of sheet metal blanking, this thesis analyzes its plastic deformation, fracture process, mathematical model and the finite element method. It emphasizes on grid remeshing, dealing with fracture problems and different blanking parameters' effects on metal sheet fracture.Deform-2D is used to simulate blanking process of sheet metal with different thicknesses according to the Normal Cockroft & Latham fracture principle. The stress and strain distribution, blanking parameters' effects on the crack and the force-stroke curve of the entire blanking process are obtained, setting a foundation for reducing blanking vibration and lowering blanking noises.According to the structure of the 80t screw coining press designed by our group, the mathematical model of blanking is made. The numerical simulation model based on Matlab/Simulink software is set up, and series simulations of blanking process are carried out. The press vibration can be judged based on the amplitudes and vibration times.According to the idea that lowering the velocity of the ram before the fracture to release the elastic energy, many types of dynamic curves are designed to attain a best vibration effect. By improving with minimum vibration as target, speed reducing spot and velocity reducing amplitude as varies, the best vibration reducing craft parameters of certain sheet metal with different depth is approached. The simulation reveals that blanking with the best blanking craft, more than 70% vibration is reduced compared to blanking at a fixed velocity and silent blanking can basically realize.