Precision rapid die casting is a die casting technology developed by General Dynamics in the 1950s and 1960s. Compared with the traditional die-casting process, this process combines stable filling and directional solidification technology while increasing the processing speed. It pioneered four frontiers in die casting technology: thermodynamic analysis, flow and filling modeling, hot workability and high integrity die casting, indirect squeeze casting.
Thermodynamic analysis is the first step in any die casting process. This was done by building an electrical simulation of the thermodynamic system, first drawing a cross-section of the mold on electrical recording paper, and then drawing the thermal load and cooling system distribution on the paper. The magnitude of the different magnetic fields represents the liquidus line, and the reciprocal of the resistivity represents the thermal conductivity.
Precision rapid die casting uses an underfill system, which requires a stable flow front. Because it is still difficult to carry out computer simulation for precision and rapid die casting, logical thinking and trial and error methods are usually used at present, but these methods will become the basis for computer simulation of flow and filling modeling.
Precision rapid die casting is the first die casting process that can successfully cast aluminum alloys containing a small amount of iron, including A356, A357, etc. In traditional die casting, these alloys are welded to the mold. Similarly, precision rapid die casting can process special alloys for military use.
Precision rapid die casting uses two punches, so it is sometimes called sleeve double punch die casting. The second punch is located inside the first heavy head, and the second punch can be used to continue to apply pressure when the casting near the first punch in the cavity or sleeve solidifies locally. Although the efficiency of this system is not high, but according to the research of precision rapid die casting machine manufacturers, its efficiency is equivalent to the first punch applying enough pressure at a certain suitable time, which is a kind of indirect squeeze casting. The re-pressurization of the second punch reduces porosity and shrinkage cavities in the casting. The speed of filling molten metal in precision and rapid die casting is only one tenth of that of traditional die casting, which can reduce the eddy current phenomenon and reduce the appearance of shrinkage cavity. At the same time, in order to play the role of the second punch, its gate is relatively large, and the order of cooling can also be artificially controlled.
Compared with other metal materials (such as brass, bronze, zinc, etc.) in precision rapid die-casting, aluminum alloy materials have many excellent casting properties such as good fluidity, small shrinkage, easy absorption, and easy oxidation, making it a precision and rapid die-casting tool. The main selected material for die casting accounts for more than 80%. Usually, the dimensional accuracy of precision rapid die-casting products is within 5 wires (1 wire = 0.01 mm), the product surface roughness (Ra) is within 1.6 microns, and the product shape and position tolerance is within 0.1 mm/300 mm; the processing methods used are mainly There are precision casting, CNC cutting, abrasive belt grinding and polishing, precision polishing, EDM, WEDM, etc.
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