Design principles and requirements for zinc alloy Die castings
A. The requirements for shape and structure of the part by pressure casting; B. Technical performance of Die casting; C. Dimensional accuracy and surface requirements of Die casting; D. Determination of surface of Die casting; design of Die casting parts is an important component of Die casting production technology In part, the design must consider the following issues: selection of mold parting surface, opening of gate, choice of plunger position, shrinkage of casting, dimensional accuracy of casting, prevention of internal defects of castings, requirements for casting holes, shrinkage deformation Related requirements and the size of the machining allowance;
First, the principle of Die casting design:
Correct selection of die-casting materials; b. Reasonable determination of dimensional accuracy of die-casting; C. Try to evenly distribute wall thickness; D. Add corners of craft parks to avoid sharp corners.
2. Classification of Die castings
According to the requirements of use can be divided into two categories, a large load of parts or relatively high speed parts, inspection of the size of the project, surface quality, chemical composition, mechanical properties (tensile strength, elongation, hardness); One type is other parts, and the items examined are size, surface quality and chemical composition. In the Die casting design, it should also be noted that the parts should meet the requirements of the Die casting process. The Die casting process is considered in terms of the position of the parting surface, the position of the pusher on the top surface, the relevant requirements of the casting hole, the relevant requirements of the shrinkage deformation, and the size of the machining allowance. Reasonable determination of the parting surface of the die-casting surface not only simplifies the structure of the die-casting, but also ensures the quality of the casting. Die casting part design requirements.
Second, Die casting design requirements:
(1) Requirements for the shape and structure of die-casting parts: a. b. Avoid or reduce core-pulling parts; C. Avoid core cross-section; reasonable die-casting structure not only simplifies the structure of die-casting molds, reduces manufacturing costs, but also improves the quality of die-casting.
(2) Design casting wall thickness requirements: Die-casting wall thickness (often referred to as wall thickness) is a special important factor in the process of die-casting. The wall thickness has a close relationship with the entire process specification, such as the calculation of filling time, the door speed. Selection, calculation of solidification time, analysis of mold temperature gradient, effect of pressure (final pressure), duration of mold retention, packaging temperature and operating efficiency; A. thicker part wall thickness will significantly reduce the mechanical properties of Die casting, The density of thin-walled castings is good, and the strength and pressure resistance of the castings are relatively increased. B. The wall thickness of the castings should not be too thin, which will result in poor filling of liquid aluminum, difficulty in forming, poor welding of aluminum alloys, and easy insulation of castings. Defects cause difficulties on the surface of the casting. Die casting process; as the wall thickness of Die casting increases, internal defects such as porosity and shrinkage porosity also increase. Therefore, under the premise of ensuring sufficient strength and rigidity of the casting, the wall thickness of the casting should be reduced as much as possible to make the thickness of the section uniform. For large-area thick-wall castings, steel bars are placed to reduce the wall thickness of the casting. According to the surface area of die-casting, the reasonable wall thickness of aluminum alloy die-casting is as follows: Surface area/mm2 Wall thickness smm 25 1.0 ~ 3.0° 25 ~ 100 1.5 ~ 4.5 > 100 ~ 400 2.5 ~ 5.0 > 400 3.5 ~ 6. 0
(3) Casting design requirements:
The effect of the rear steel bar is the change of the thickness of the thin wall. In order to improve the strength and rigidity of the part, the shrinkage deformation of the casting is prevented, and the workpiece is prevented from being deformed from the mold and the filling process. When functioning the secondary circuit (metal flow path), the thickness of the die-cast steel should be less than the thickness of the wall surface, generally replacing the thickness of 2/~ ();
(iv) Requirements for casting design fillets:
Die casting is connected to each wall and wall. Regardless of the right corner, sharp or blunt, the root of the blind hole and the groove should be designed with rounded corners. When the position of the parting surface is expected to be determined, do not use rounded corners. The rest must generally be round, the round shoulders should not be too big or too small, the Die casting is too small to be prone to cracks, and the shrinkage holes are too easy to loosen. The Die casting circle generally takes: half wall thickness r or less wall thickness or less; Used to help metal flow, reduce eddy currents or turbulence; avoid stress concentration of parts due to the presence of rounded corners, and cause cracking; when parts are plated or coated, rounded corners can be evenly coated to prevent tipping Angular deposition. It can extend the life of the die-casting mold without causing collapse angles or cracks due to the presence of sharp corners of the cavity.
(5) Casting gradient requirements for Die casting design:
The gradient function is to reduce the friction between the casting and the cavity, to facilitate the removal of the casting; to ensure that the surface of the casting does not pull; to extend the service life of the mold, the minimum casting angle of the aluminum alloy die-casting is as follows: The minimum casting aluminum alloy is die-cast on the inclined surface of the core hole ( Unilateral) 1°1°30 ' 2°
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