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Three special requirements of casting method for casting structure
（1） Investment casting:
Easy to manufacture wax mold
The holes and grooves on the casting should not be too small or too deep or too deep, which is not conducive to the smooth filling of the corresponding holes on the investment mold by the coating and sand particles during the shell making process, so as to form a suitable mold cavity; at the same time, the too deep holes and grooves also bring difficulties to the sand cleaning of the casting. In general, the hole diameter shall be greater than 2mm (thin piece > 0.5mm). When through-hole, the hole depth / hole diameter is less than 4-6; when through-hole, the hole depth / hole diameter is less than 2. The groove width shall be more than 2mm, and the groove depth shall not be more than 2-6 times of the groove width.
Reduce the hot spot and make sure the wall thickness is uniform. Generally, riser is not set separately in investment casting, but the roughened sprue is used as riser to directly feed the casting. In accordance with this process, the thin-walled structure should be adopted as far as possible, and the wall thickness distribution should conform to the directional solidification principle.
Avoid the large flat plate structure because the high temperature strength of the shell is low and easy to deform, so when designing the casting structure, try to avoid the large flat surface.
（2） Metal castings:
The shape and inner cavity of the casting shall be as simple as possible, the structural inclination of the casting shall be increased as much as possible, and holes with too small or too deep diameter shall be avoided, so as to facilitate the extraction of the core and ensure the smooth extraction of the casting.
The wall thickness of the casting shall be uniform to prevent shrinkage and crack defects; at the same time, it shall be noted that the wall thickness shall not be too thin, and large horizontal wall shall be avoided as far as possible to prevent defects such as pouring failure and cold separation. For example, the minimum wall thickness of the aluminum silicon alloy casting is 2mm-4mm, and the minimum wall thickness of the aluminum magnesium alloy is 3mm-5mm.
（3） Die casting:
The side concave and deep cavity of the die casting shall be eliminated as far as possible.
Try to use thin-walled structure with uniform wall thickness. The suitable wall thickness of die casting is generally 1mm-3mm for zinc alloy, 1.5mm-5mm for aluminum alloy and 2mm-5mm for copper alloy.
Inlay can be used in die casting. The advantages of inlay should be brought into full play in order to make complex parts, improve the local properties of die casting and simplify the assembly process. In order to make the connection of the insert in the casting reliable, the insert should be inserted into the casting part to make grooves, bosses or knurling, etc.