1, structural process analysis of die casting
1.1 The reasonable choice of materials used in die casting. Aluminum alloy because of its good die-casting performance, specific strength, and specific stiffness is high, high and low-temperature mechanical properties are also good, its surface has a dense oxide film, and certain corrosion resistance and in the production of die castings are used in large quantities, widely.
1.2 The minimum wall thickness of the die casting is 3mm, and the minimum wall thickness is also by the process requirements, and the 3mm*54mm rib on the two long sides, 8mm*4mm rectangular hole, R4mm flange, etc. are also by the requirements of the die casting process.
1.3 Because of the strong affinity between aluminum alloy and iron at high temperatures, it is easy to bond with the pressure chamber, and the die-casting mold design should use a cold chamber die-casting machine as far as possible.
2, the choice of parting surface
According to the middle shell for the long frame hollow parts, both sides of the long side have different side convex, step, small rectangular hole structure characteristics. The die casting parting surface of this die casting, except for the horizontal parting between the moving die and the fixed die, is chosen in the upper face of the shell, and the forming of both long sides needs to adopt the lateral parting mold structure form (i.e. the form of lateral core extraction of the inclined pin slider).
3, the determination of the pouring system
Due to the thin wall thickness of the four sides of the intermediate shell and the difference between the plant and width dimensions, to prevent cold separation and ensure the thermal balance of the mold, the pouring system uses side gates. The molten alloy is pressed in simultaneously from both ends of the long side of the casting, and a larger overflow slot is set at the part where the metal liquid meets or is likely to produce eddy currents. A larger overflow slot can be set both exhaust role and can set slag and conducive to the thermal balance of the mold.
4, the choice of die-casting machine
The middle shell is no insert die-casting, can choose horizontal cold room die-casting machine, according to the actual production of enterprises to choose the appropriate die-casting machine, to meet the actual production requirements.
5, die-casting mold forming parts working size calculation and determination
By die-casting alloy comprehensive shrinkage rate list data can be seen: aluminum alloy shrinkage rate in the free shrinkage rate of 0.50%-0.75%; hindered shrinkage rate of 0.40%-0.65%. After separate analysis and calculation, it is determined.
6, die-casting process protocol
The process protocol is mainly to determine the process parameters of die-casting production. Die-casting production process parameters mainly include die-casting with new, old material reasonable ratio (old material is impossible to abandon, new, old material unreasonable ratio will affect the material performance and shrinkage rate), determine the die-casting production process protocol, equipment, the correct use of paint (because it has the role of improving the working conditions of the mold, improve molding conditions, improve the quality of castings and extend the life of the mold and essential), etc.
7, die-casting mold assembly design
There are two structural options in the design of die assembly.
Program one: die-casting forming castings, the shape of the inner cavity mold forming part are designed into the form of the overall structure; program two: forming castings, the shape of the mold work parts are designed into the set, set block set combination of structural form.
After analysis and comparison, although program one uses less material, good strength, short processing cycle, but the mold manufacturing accuracy is difficult to ensure that the mold damage and wear are not easy to repair. While the second option increases the use of alloy steel, the processing cycle is extended, but the precision of the working parts of the mold is easy to ensure, and the size adjustment of the working parts of the mold and the wear and damage formed after a certain period of production is also convenient to repair and replace.
In the assembly structure of the mold, the fixed mold insert and the fixed mold insert of the fixed mold part are set into the fixed mold plate in the form of grouping. For the moving side, the moving die insert and the moving die insert are inserted into the moving template in a group. The die plate is made of medium carbon steel.
The working parts are made of hot work die steel for die casting, the strength, and processing accuracy of the die can be guaranteed, and the adjustment of each forming size is also convenient.
Because the hollow shell of die casting has long sides of rectangular holes, flanges, convex tendons, and other structures respectively. So both sides need to use different slider structure forming, tilt pin core parting, wedge tight block locking lateral forming form. Considering the thin wall thickness around the middle shell, and the size of the overflow groove has been enlarged, so pushrods are set on the overflow groove and the cross sprue, and 8 rectangular sheet pushrods are set on both sides of the long side of the die casting to ensure the smooth and synchronous launch of the overflow groove, cross sprue and die casting.
The mold is reset by the reset rod to push the pushrod fixed plate to reset.