Notes for designing die casting parts


If you want to master the design of die casting parts attention, need to start from the design basis of die casting, so that it is easier to understand.

一 . The design of die casting involves four aspects:

A. Requirements of shape and structure of parts for pressure casting; B. Process performance of die casting; c. Dimensional accuracy and surface requirements of die casting parts; d. Determination of die casting parting surface; Die casting parts design is the important part in die casting production technology, the design must consider the following questions: the mold parting surface selection, gate opening, the choice of position of plunger, the contraction of the casting, the casting dimension accuracy assurance, prevention of internal defects of castings, cast hole of the requirements, the related requirements of contraction deformation and the size of the machining allowance, etc;

二. The design principles of die casting are:

a, choose the material of die casting correctly, b, determine the dimensional accuracy of die casting reasonably; c, try to make the wall thickness distribution uniform; d. Add craft park corners at each corner to avoid sharp corners.

三. Classification of die castings:

According to the use of requirements can be divided into two categories, a large load of parts or parts with a high relative speed of movement, the inspection items are size, surface quality, chemical composition, mechanical properties (tensile strength, elongation, hardness); The other category is other parts, the inspection items are size, surface quality and chemical composition. In the design of die casting, we should also pay attention to the parts should meet the process requirements of die casting.

The technology of die casting is considered from the position of parting surface, the position of pushing rod on the top surface, the relevant requirements of casting hole, the relevant requirements of shrinkage deformation and the size of machining allowance. Reasonable determination of parting surface of die casting surface can not only simplify the structure of die casting, but also ensure the quality of casting. Requirements for the design of die cast parts.

四. Requirements for round corners of casting design:

(1) die casting shape structure requirements: a, eliminate internal side concave; b. Avoid or reduce the core pulling part; c. Avoid core crossing; Reasonable structure of die casting can not only simplify the structure of die casting mold, reduce manufacturing cost, but also improve casting quality.

(2) Wall thickness requirements for casting design: Die casting wall thickness (often referred to as wall thickness) is a special significance in die casting technology factors, the wall thickness has close relationship with the whole process specification, such as filling time of calculation, the choice of gate velocity, coagulation time of calculation, the analysis of the mold temperature gradient, the action of pressure (final pressure), the duration of stay mould, casting temperature of pack out and operation efficiency;

a. The thickness of the wall thickness of the parts will significantly reduce the mechanical properties of the die casting, and the compactness of the thin-wall castings is good, which relatively improves the strength and pressure resistance of the castings; b, casting wall thickness can not be too thin, too thin will cause poor liquid aluminum filling, forming difficulties, aluminum alloy welding is not good, casting surface is easy to produce cold isolation and other defects, and bring difficulties to the die casting process; Die casting with the increase of wall thickness, its internal pores, shrinkage holes and other defects increase, so in the premise of ensuring sufficient strength and stiffness of the casting, should try to reduce the thickness of the casting wall and keep the thickness of the section uniform, in order to avoid shrinkage and porosity and other defects, the thick wall of the casting should be reduced (reduced material), increase reinforcement;

For large-area slab thick-walled castings, reinforcement is provided to reduce the thickness of the casting wall. According to the surface area of die casting, the reasonable wall thickness of aluminum alloy die casting is as follows: die casting surface area /mm2 wall thickness S/mm ≤25 1.0 ~ 3.0 > 25~100 1.5 ~ 4.5 > 100~400 2.5 ~ 5.0 > 400 3.5 ~ 6.0

(3) Requirements for casting design bars:

After the effect of reinforcement is thin wall thickness change, in order to improve the strength and rigidity of the parts, prevent to reduce casting contraction deformation, and avoid the workpiece deformation during ejection from the mould and filling to function when the secondary circuit (metal flow path), the thickness of the die casting steel should be less than the thickness of the wall, generally take the place of the thickness of the 2/3 to 3/4;

(4) Requirements for round corners of casting design:

Die casting on every wall and wall connection, regardless of right Angle, acute or obtuse, the root of the blind holes and grooves, should be designed with rounded corners, only when is expected to determine the parting surface position, do not use the rounded connection, the rest parts generally must be rounded, rounded shoulds not be too big or too small, too small die casting cracks easily, too easy to loose shrinkage cavity, die casting round generally take: 1/2 wall thickness ≤R≤ wall thickness;

The role of rounded corners is to facilitate the flow of metal, reduce eddy or turbulence; Avoid parts due to the presence of rounded corners resulting in stress concentration and resulting in cracking; When the parts to be electroplated or coated, the rounded corners can be obtained uniform coating, to prevent the deposition of sharp corners; Can prolong the service life of die casting die, not due to the existence of die cavity sharp Angle caused by Angle collapse or cracking;

(5) Casting slope requirements for die casting design:

The role of slope is to reduce the friction between the casting and the mold cavity, easy to remove the casting; Ensure that the casting surface is not strained; Prolong the service life of die casting die, the general minimum casting inclination of aluminum alloy die casting is as follows: the minimum casting inclination of aluminum alloy die casting outer surface and inner surface core hole (single side)1° 1°30 ‘2°