In the fast injection speed phase, the moving parts in the system have considerable kinetic energy. The hydraulic oil, hydraulic cylinder piston, punch, punch and molten metal all have quality and move at a high speed. When the cavity is full, these substances must stop moving. The energy is dissipated by generating a very high pressure peak (impact pressure), causing elastic deformation of the equipment and mold components. "Peak shock pressure is the cause of many problems in the high-pressure die casting process. The peak shock pressure causes the equipment and the mold to bear additional pressure, thereby shortening the service life of both. When the shock occurs, the high pressure in the cavity is The main cause of flash. The magnitude of the peak impact pressure is affected by many factors, including equipment design, punch size, punch speed, quality of moving parts and the time required to stop the movement.
The punch speed is the most important factor that determines the impact pressure. I think "the size of the pressure peak is proportional to the square of the velocity." Therefore, if the fast injection velocity is reduced by 50%, the peak pressure should be reduced to only 25% of the original value. The simplified hypothesis that supports the relationship stated is that energy is absorbed after passing through a certain stroke, and the size of the stroke is constant regardless of speed. The increase of the peak pressure requires the increase of the clamping capability of the equipment accordingly. In actual observations, the increase in this value even exceeds the ratio of the square of the speed. We found that the impact pressure value is very sensitive to the punch velocity at the moment when the cavity and overflow are filled. Other important factors that determine the impact pressure, including the design of the equipment, the quality of the moving parts of the equipment, and the amount of metal during injection, all need to be considered. However, it is almost impossible to change these factors to reduce the impact pressure to achieve significant results. Major changes to the equipment design are beyond the scope of this paper. It is feasible to only reduce the quality of the moving injection parts, but for die casting a certain designed die casting, the amount of metal used can only be slightly reduced.
