Technical requirements for die casting mold assembly
Final assembly of die-casting molds involves precisely assembling all mold components into a complete mold according to design requirements. Technical requirements permeate every step of the assembly process, directly impacting the mold’s performance, die-casting quality, and service life. The primary technical requirement for final assembly is ensuring the relative positional accuracy of mold components, particularly the fit of the parting surfaces and the coaxiality of the cavity and core. The flatness error of the parting surfaces must be controlled within 0.02 mm/m, with a minimum fit area of 80% to prevent flash and metal leakage during mold closing. For molds with multiple cavities or complex cores, the positional error between cavities should be no greater than 0.03 mm, and the coaxiality error between the core and cavity must be controlled within 0.02 mm to ensure dimensional consistency in the die-casting. For example, the coaxiality of the multiple valve seat cores in a die-casting mold for an automotive engine cylinder head must be controlled within 0.015 mm with the cavity. Otherwise, the valves and seat inserts will not fit properly during die-casting assembly.
The final assembly of the mold must ensure that the movements of all moving parts are flexible and coordinated, without any jamming or abnormal noise. This is one of the core technical requirements of the final assembly. The push rod and push tube of the ejection mechanism should move smoothly within the full stroke range, and the parallelism error of the push plate should not exceed 0.02mm/100mm to ensure that the ejection force is evenly distributed. The slider movement of the core pulling mechanism must be smooth, the core pulling and reset positions must be accurate, and the fitting clearance between the locating pin and the locating groove must be controlled at 0.01-0.02mm to ensure the stability of the core pulling size. The fitting clearance between the guide pin and the guide sleeve must meet the design requirements (usually 0.01-0.03mm), and there must be no looseness or skewness during the opening and closing of the mold, and the guiding accuracy must meet the use requirements. For example, for molds with inclined guide pins for core pulling, the fitting clearance between the inclined guide pins and the slider holes must be controlled at 0.02-0.04mm to ensure that the core pulling action is synchronized and there is no interference, otherwise it will cause the slider to get stuck or the core pulling to be incomplete.
The strength and rigidity of the mold assembly are crucial to ensuring stable operation in high-pressure environments. The assembled mold must withstand the clamping force of the die-casting machine (typically 40-2500 kN ) without noticeable deformation, with maximum mold plate deflection not exceeding 0.1 mm/m . Fasteners (such as bolts and screws) must be tightened to the specified torque, and the preload should be evenly distributed to avoid localized stress and mold plate deformation. For large molds, high-strength bolts (such as 12.9 -grade hexagon socket head cap bolts) are required. The tightening torque is determined by the bolt diameter; for example, an M16 bolt should have a tightening torque of 300-350 N · m to ensure a secure connection. Furthermore, the mold’s lifting rings must be securely installed, with a load-bearing capacity greater than 1.5 times the mold’s weight, to prevent safety accidents during lifting.
The sealing and exhaust performance of the mold assembly must meet the technical requirements to ensure the smooth progress of the die-casting process. The pipe connections of the cooling system and the heating system must be sealed reliably without leakage. The water pressure test pressure is 1.5 times the working pressure (usually 0.6-1.0MPa), and the pressure is maintained for 30 minutes without pressure drop. The exhaust groove of the exhaust system must be unobstructed, and the depth and width must meet the design requirements. During the mold trial, the exhaust effect must be verified through a smoke test or an appearance inspection of the die-casting to ensure that the gas in the cavity can be completely discharged. For example, when die-casting high-fluidity aluminum alloys, the depth of the exhaust groove must be controlled at 0.05-0.08mm. If the exhaust groove is blocked or the size is not consistent during assembly, it will cause air holes or insufficient pouring defects in the die-casting.
The appearance and marking requirements of the mold after final assembly are also an important part of the technical specifications. The outer surface of the mold must be clean, free of obvious scratches, rust, or oil stains, and sharp edges must be rounded (R0.5-R1) to prevent scratches during operation. The mold’s reference surfaces, locating pin holes, lifting eye holes, etc. must be clearly marked to facilitate installation and positioning of the mold on the die-casting machine. In addition, the mold must be equipped with a complete set of accessories, such as cooling water pipe connectors, heating rod terminal blocks, and limit blocks. All accessories must be securely installed and properly positioned. After final assembly is completed, a trial mold verification is required. Through continuous production of at least 30 molds, the dimensional accuracy, surface quality, and operating stability of the die-casting parts are checked. Based on the trial mold results, necessary adjustments are made until the design requirements and production needs are met. After the trial mold is qualified, a detailed final assembly inspection report must be issued, recording the measured values of each key parameter to provide a basis for the subsequent maintenance and use of the mold.
