Arrangement of die-casting inserts in the sleeve
The placement of die-casting inserts within the mold core is a crucial aspect of mold structural design, directly impacting mold force uniformity, venting efficiency, and die-cast part quality. A reasonable placement must adhere to the principles of force balance, ease of processing and maintenance, and compliance with the specific characteristics of the die-casting process. Insert placement must ensure uniform force distribution during the die-casting process to avoid deformation of the mold core or loosening of inserts due to localized excessive force. For multi-cavity molds, inserts should be symmetrically distributed around the center of the mold core, with consistent spacing between adjacent inserts (typically no less than 30mm) to ensure uniform filling conditions across all cavities and to allow sufficient space for cooling channels and fastening bolts. For example, in a four-cavity connector die-casting mold, inserts should be symmetrically arranged in a square or diamond pattern around the center of the mold core, with spacing controlled at 40-50mm. This ensures uniform force distribution under die-casting pressure (60-80MPa) and reduces the risk of deformation.
The positioning of the insert within the sleeve is crucial for ensuring accurate placement. Common positioning methods include spigot, pin, and key. Spigot positioning involves machining a stepped hole in the sleeve that matches the insert’s profile. A corresponding spigot is then designed on the insert’s bottom or side, with a clearance of 0.01-0.02mm. This method is reliable, easy to manufacture, and suitable for most insert placements. Pin positioning is often used as a supplementary positioning method. Two to four dowel pins are placed at the insert-sleeve interface, with a pinhole diameter tolerance of H7 and a pin tolerance of M6. This ensures the insert maintains accurate positioning even after repeated assembly and disassembly. Key positioning is suitable for large inserts or applications requiring high lateral forces. By inserting a flat key between the insert’s side and the sleeve, the insert’s shear resistance is enhanced. The clearance between the key and keyway is controlled to 0-0.015mm. For example, large-cavity inserts in automotive engine block die-casting molds require both spigot and key positioning. The spigot ensures axial positioning accuracy, while the key resists lateral forces during molten metal filling.
The arrangement of inserts within the sleeve depends on the shape and size of the die-casting. Common arrangements include linear, matrix, and circular. The linear arrangement is suitable for long die-castings or single-cavity molds. The inserts are arranged along the length of the sleeve, with their centerlines aligned to ensure balanced forces. The matrix arrangement is suitable for small to medium-sized, multi-cavity die-castings, such as electronic connectors and small gears. The inserts are evenly distributed in rows and columns, with equal spacing between each row and column. This facilitates symmetrical gating system layout and uniform cooling channel design. The circular arrangement is suitable for circular or annular die-castings, such as bearing sleeves and gear blanks. The inserts are evenly distributed in a circular pattern around the center of the sleeve, typically 3-6 in number. Adjacent inserts are placed at equal angles to ensure uniform metal filling from the center gate into each cavity. For example, in a six-cavity bearing sleeve die-casting mold, the inserts are arranged in a regular hexagonal pattern with equal center spacing, ensuring consistent filling time and pressure for each cavity.
The design of the gap between the insert and the sleeve must take into account both the requirements of exhaust and preventing molten metal leakage. Typically, a gap of 0.03-0.05mm is set on the mating surface of the insert and the sleeve to serve as a venting channel. At the same time, a sealing groove is set on the outside of the gap, and a heat-resistant sealing ring (such as a fluororubber sealing ring) is installed to prevent molten metal from overflowing from the gap. For large inserts, venting grooves with a width of 5-10mm and a depth of 0.05-0.1mm are also required on the mating surface. The grooves are distributed along the circumference of the insert and spaced 50-100mm apart to ensure that the gas inside the cavity can be smoothly discharged through the gap and venting grooves. For example, the cavity insert of a large gearbox housing die-casting mold has 4-6 venting grooves on the mating surface with the sleeve . Together with the venting holes at the bottom of the insert, they form a complete exhaust system to reduce porosity defects in the die-casting.
The placement of inserts within the mold plate should also consider the mold’s overall dimensions and ease of assembly and removal. The distance between the edge of the insert and the edge of the mold plate should be no less than 50 mm to ensure mold plate rigidity and prevent edge deformation due to insufficient strength. For inserts that require frequent replacement (such as in molded areas prone to wear), sufficient clearance should be provided to facilitate the use of removal and installation tools. Typically, 20-30 mm of clearance should be reserved around the insert. Furthermore, the placement of the inserts should be coordinated with the mold’s ejection and core pulling mechanisms to avoid interference with components such as the push rod, guide pins, and core pulling sliders. For example, the mold plate area below the insert should provide clearance for the push rod retaining plate and ejector plate, and the side of the insert should allow for the sliding travel of the core pulling mechanism’s slider to ensure smooth operation. Using 3D modeling software for virtual assembly and motion simulation can proactively identify interference issues during placement, optimize the position and spacing of the inserts, and ensure the rationality of the overall mold structure.
