The local modular structure of a die-casting mold refers to the use of a modular form in the key molding parts of the mold, while other non-critical parts still maintain an integral structure. This design has significant advantages in balancing mold rigidity and processing convenience. For example, when a part of a die-casting part has a complex pattern, deep cavity or special-shaped structure, this area can be designed as a removable insert, connected to the integral template with screws and pins, while the remaining parts are processed as a whole. The advantage of the local modular structure is that it can reduce the processing difficulty of complex parts while ensuring the rigidity and strength of the mold as a whole, making it suitable for the production of medium-complexity die-casting parts. Taking the die-casting mold of an automobile door handle as an example, the curved surface structure of the gripping part can be processed as a whole, while the complex molding surface around the keyhole is designed as a local insert, which not only simplifies the processing technology but also facilitates subsequent wear and tear replacement.
The fit between the insert and the formwork in a partially modular structure requires high precision, typically employing a transition fit of H7/n6 or an interference fit of H7/r6 to prevent relative displacement during the high-pressure die-casting process. The insert is typically positioned using a combination of stopper and pin positioning, with the stopper clearance controlled to 0.01-0.02mm and the pin-to-pinhole clearance no greater than 0.005mm. This ensures accurate positioning of the insert even after repeated stresses. Furthermore, the mating surfaces between the insert and formwork are precision-ground to a flatness tolerance of no more than 0.005mm/m to prevent metal leakage and flash due to a poor fit. The material selection for the partially modular structure is targeted. The forming inserts are constructed of H13 hot-working die steel (HRC 45-50 hardness) to withstand the high-temperature and high-pressure working environment, while the formwork can be constructed of lower-cost 45 steel or S50C steel. After quenching and tempering, the hardness reaches HB220-250, ensuring support strength while reducing manufacturing costs.
A fully modular structure is one in which all major components of the mold, such as the cavity, core, and template, are designed as independent modules, which are assembled into a complete mold through standardized connectors. This structural form is widely used in large and complex die-casting molds. For example, the die-casting mold for the cylinder block of an automobile engine adopts a fully modular structure. Its cavity is composed of a combination of multiple side inserts, bottom inserts, and top inserts. Each insert is responsible for molding a specific part of the cylinder block, and the overall cavity is formed through precise positioning and fastening connections. The biggest advantage of the fully modular structure is its high degree of modularity, which facilitates the individual processing, heat treatment, and assembly of each component, significantly shortening the mold manufacturing cycle and facilitating mold maintenance and refurbishment. When a certain insert is worn or damaged, only the corresponding component needs to be replaced, without the need to scrap the entire mold, which greatly reduces the cost of use.
Controlling assembly precision for the fully modular structure is central to the design. The relative positional error between each insert must be controlled within 0.01mm to ensure the dimensional accuracy and surface quality of the die-cast part. A unified datum principle is typically employed, with the mold’s guide pin and sleeve holes serving as the positioning reference. All insert machining and assembly are performed around this datum to minimize cumulative errors. Various methods are used to connect the inserts. For locations subject to high stress, bolts and locknuts are used for fastening, with tapered surfaces used for enhanced stability. For locations subject to less stress, a combination of screws and locating pins can be used. The fully modular structure places high demands on machining equipment, requiring the use of precision equipment such as five-axis machining centers and coordinate grinders to ensure the shape accuracy and dimensional consistency of each insert. Furthermore, precision measuring tools (such as coordinate measuring machines) are used for real-time inspection during the assembly process to ensure that the assembled mold meets design accuracy requirements.
The choice between a partial combination and a fully combined structure should be determined comprehensively based on the structural characteristics, production batch, and precision requirements of the die-casting. For die-castings with moderately complex shapes and small production batches, the partial combination structure is more cost-effective; for large, complex, and mass-produced die-castings, the fully combined structure can better reflect its economy and flexibility. In practical applications, the two structural forms can also be used in combination. For example, in a fully combined mold, a partial combination design is used inside a complex insert to further improve the adaptability of the mold. With the promotion of modular design concepts and advancements in precision machining technology, the proportion of combined structures used in die-casting molds continues to increase. The use of standardized inserts and connectors not only reduces mold manufacturing costs, but also improves the interchangeability and versatility of the mold, providing strong support for rapid response to market demand.
