Reduce core pulling areas in die castings
Core pulling mechanisms are components within the die that form die-cast parts, including holes, slots, and bosses that are perpendicular to or angled with the die-casting direction. Their presence increases mold complexity, cost, and the risk of failure. Reducing the number of core pulling areas in die-cast parts can simplify the mold structure, improve production efficiency, and reduce costs, while also reducing mold wear and extending mold life. Therefore, during the die-casting design phase, structural optimization should be implemented to minimize or eliminate areas requiring core pulling, leading to more economical and efficient die-casting production.
Optimizing the structural direction of die-casting parts so that structures such as holes and grooves are aligned with the die-casting direction as much as possible is the most effective way to reduce the number of core-pulling locations. If the holes and grooves on the die-casting part are perpendicular to the die-casting direction or at a certain angle, a core-pulling mechanism is required. However, if the direction of these structures is adjusted to be parallel to the die-casting direction, they can be directly formed using a fixed core without the need for core pulling. For example, by changing the through-holes on the side of the casting to through-holes on the end face so that their axes are aligned with the die-casting direction, the use of a lateral core-pulling mechanism can be avoided; designing the grooves on the side as grooves on the top surface can also eliminate the need for core pulling. During the design process, priority should be given to the consistency of the structural direction with the die-casting direction to fundamentally reduce the number of core-pulling locations.
Using an inclined structure instead of a vertical one to reduce the core-pulling angle is also an effective measure to reduce the number of core-pulling locations. For some structures that cannot be perfectly aligned with the die-casting direction, they can be designed at a certain angle to the die-casting direction, utilizing the casting’s inherent draft angle to achieve molding and avoid the need for a core-pulling mechanism. For example, if a casting requires a boss on the side, core-pulling is required if the boss is perpendicular to the side (i.e., perpendicular to the die-casting direction). However, if the boss is designed at a certain angle to the side (i.e., a smaller angle to the die-casting direction) that is greater than the casting’s draft angle, molding can be achieved through the inclined core design, eliminating the need for core-pulling. This design approach requires precise calculation of the inclination angle to ensure that it meets the required performance and allows for smooth demolding of the casting.
Merging or eliminating unnecessary core-pulling structures and simplifying the functions of castings can also reduce the number of core-pulling locations. Without affecting the performance of the casting, the need for core-pulling can be significantly reduced by merging multiple small structures that require core-pulling into a large structure that does not require core-pulling, or by eliminating some unnecessary bosses and grooves. For example, if there are multiple small lateral bosses distributed on the casting, these bosses can be merged into a larger boss along the die-casting direction, or these small bosses can be formed through post-processing to avoid the use of multiple core-pulling mechanisms. At the same time, the functional requirements of the casting should be examined, and those complex core-pulling structures that are set up for aesthetics or non-critical functions should be removed, giving priority to ensuring the realization of the core functions of the casting, thereby reducing the number of core-pulling locations.
Using the casting’s own structure or subsequent processing to replace core-pulling molding is also an important way to reduce the number of core-pulling parts. For some complex core-pulling structures, if it is easier to achieve them by post-processing after die-casting, these structures can be designed to be processed and formed later to avoid the use of core-pulling mechanisms during the die-casting process. For example, high-precision lateral threaded holes on castings are difficult to form directly by die-casting, have low precision, and require a complex spiral core-pulling mechanism. However, by reserving a bottom hole by die-casting and then using tapping processing later, not only can the thread accuracy be guaranteed, but the use of a core-pulling mechanism can also be avoided. In addition, for some shallow lateral grooves, the elastic deformation of the casting can be used to achieve demolding without the need for core-pulling. This method is suitable for alloy materials with good plasticity, such as zinc alloys.
Rationally design the parting surface of the casting and use it to achieve the molding of complex structures and reduce the use of core-pulling mechanisms. The parting surface is the junction between the movable mold and the fixed mold of the mold. By optimizing the position and shape of the parting surface, some structures that require core pulling can be molded at the parting surface, thus avoiding the use of core-pulling mechanisms. For example, if the parting surface is set in the middle of the annular groove on the casting, the upper and lower parts of the groove can be formed separately by the parting surface of the movable mold and the fixed mold, without the need for a core-pulling mechanism. This method requires precise design of the parting surface to ensure that it does not affect the appearance and performance of the casting, while facilitating mold processing and demolding of the casting. By cleverly utilizing the parting surface, it is possible to achieve the molding of complex structures and reduce the number of core-pulling areas without increasing the complexity of the mold.
By combining these methods, the core-pulling area of die castings can be significantly reduced, simplifying the mold structure, improving production efficiency, and reducing production costs. In the actual design process, comprehensive consideration should be given to factors such as the functional requirements of the casting, material properties, and production batch size. The most appropriate solution should be selected to minimize the core-pulling area while ensuring the performance of the casting, thereby achieving economical and efficient die casting production.
