Relationship between die casting gate speed, injection speed and pressure
The ingate velocity, injection speed, and pressure in die casting are closely linked. Together, these three parameters constitute the core parameter system of the die casting process. Their synergistic effect directly determines the filling quality of the molten metal and the ultimate performance of the casting. The injection speed is the speed at which the punch pushes the molten metal, indirectly affecting the ingate velocity by changing the molten metal flow rate. The injection pressure, on the other hand, is the driving force behind the punch, and its magnitude affects the stability of the injection speed and the kinetic energy of the molten metal flow. Understanding the inherent connection between these three parameters is key to optimizing the die casting process.
From a physical perspective, the gate velocity and injection speed are positively correlated. Given a constant molten metal viscosity and ingate cross-sectional area, increasing the injection speed increases the molten metal flow rate through the ingate per unit time, thereby increasing the ingate velocity. This relationship is similar to a water pipeline system: the higher the pump speed (equivalent to the injection speed), the faster the water flows through the pipe joint (equivalent to the ingate). However, it should be noted that this positive correlation is not absolutely linear. When the injection speed is too high, the molten metal may splash due to inertia, causing the actual flow rate entering the ingate to fluctuate, which in turn causes the ingate velocity to deviate from the theoretically calculated value.
The impact of injection pressure on ingate velocity is primarily reflected in dynamic regulation. The magnitude of the injection pressure determines the acceleration of the injection punch. In the initial stages of injection, higher pressure allows the punch to quickly reach the set velocity, ensuring a rapid increase in ingate velocity to meet filling requirements. At the end of the filling phase, appropriately reducing the pressure can reduce the punch velocity and avoid cavity impact caused by excessive ingate velocity. Furthermore, when the molten metal encounters resistance during the filling process (such as flow obstruction in complex areas of the cavity), the injection pressure increases the punch thrust to maintain a stable injection velocity, thereby preventing a significant decrease in ingate velocity and ensuring a continuous filling process.
The gate speed, in turn, will also affect the setting of the injection pressure. When the gate speed is too high, the flow resistance of the molten metal in the mold cavity increases. At this time, a higher injection pressure is required to overcome the resistance and maintain the movement speed of the punch; on the contrary, if the gate speed is too low, the flow resistance of the molten metal is small, and the injection pressure can be appropriately reduced. This mutual influence relationship requires two-way optimization during process debugging: it is necessary to set a reasonable injection speed according to the requirements of the gate speed, and to adjust the injection pressure according to the actual flow resistance to form a dynamic balance among the three. For example, when producing highly complex castings, a higher gate speed is usually required, which requires the injection speed and pressure to cooperate with each other to ensure filling efficiency while avoiding excessive impact.
In actual production, the coordinated control of the three needs to be fine-tuned in combination with the specific characteristics of the casting. For example, for thin-walled and complexly structured castings, a higher gate speed is required to ensure rapid filling. At this time, a higher injection speed should be set, and the corresponding injection pressure should be used to maintain a stable speed. For thick-walled castings, the gate speed needs to be appropriately reduced, and the injection speed and pressure should also be adjusted accordingly to reduce air entrainment and oxidation. By adopting a closed-loop control system, real-time monitoring of changes in gate speed, injection speed, and pressure, and dynamic adjustment based on feedback data, precise matching of the three can be achieved, significantly improving the stability of casting quality. This collaborative optimization approach is an important sign that modern die-casting processes are moving from empiricism to precision, and is also a core technical means to improve production efficiency and product quality.
