Die Casting Structural Design Specification and Process Requirements

Jul. 30, 2020

The structural design of die casting is the first step of die casting work. The rationality of the design and process adaptability will affect the smooth progress of subsequent work, such as parting surface selection, internal gate opening, push-out mechanism layout, mold structure and manufacturing difficulty, alloy solidification, and shrinkage law, casting accuracy guarantee, and defects The types of die castings will be based on the quality of the structural process of the die casting itself. The quality of the structural design directly affects the production yield and cost. This article introduces the relevant requirements for the structural design of die castings.

1. Matters needing attention in the design of die casting parts

1.1 The design of the Compressor casting part involves four aspects

a. That is, the requirements of pressure casting on the shape and structure of parts;

b. Process performance of die castings;

c. The dimensional accuracy and surface requirements of die castings;

d. Determination of parting surface of die casting;

The part design of die casting is an important part of die casting production technology. The following issues must be considered when designing: a selection of mold parting surface, the opening of the gate, selection of ejector position, shrinkage of casting, a guarantee of dimensional accuracy of casting, casting Prevention of internal defects, relevant requirements for casting holes, relevant requirements for shrinkage and deformation, and the size of machining allowances;

1.2 Structural design principles of die castings

a. Correctly choose the material of die-casting;

b. Reasonably determine the dimensional accuracy of die castings;

c. Try to make the wall thickness evenly distributed;

d. Add craft around corners at each corner to avoid sharp corners

1.3 Process principles of die-casting structure

1) Try to eliminate the undercut inside the casting to make the mold structure simple.

2) Try to make the wall thickness of the castings as uniform as possible, and use ribs to reduce the wall thickness and reduce defects such as porosity, shrinkage, and deformation of the casting.

3) Try to eliminate deep holes and deep cavities on castings. Because the small core is easy to bend and break, the filling and exhaust of the deep cavity are poor.

4) The designed casting should be easy to de-mold and core pulling.

5) The uniformity of meat thickness is necessary.

6) Avoid sharp corners.

7) Pay attention to the draft angle.

8) Pay attention to the tolerance marking of the product.

9) Too thick or too thin is not suitable.

10) Avoid corner chamfering (less energy can be less).

11) Consider the difficulty of post-processing.

12) Minimize voids in the product.

13) Avoid peninsula-like local shapes that are too weak.

14) Too long forming holes or too long forming posts are not suitable

Oem Compressor Casting Part

Oem Compressor Casting Part

2. OEM Compressor casting part design

2.1 The shape and structure of die castings

a. Eliminate the internal undercut; simplify the mold structure, the temperature of the die-casting mold is relatively high, the internal structural parts are easy to expand and cause jamming;

b. Avoid or reduce core pulling parts;

c. Avoid cross cores; a reasonable die-casting structure can not only simplify the structure of die casting mold, reduce manufacturing cost, but also improve the quality of castings.

2. 2 wall thickness

The wall thickness of the die casting has a great influence on the quality of the casting. When the wall of the casting is too thin, the metal will not be welded well, which will affect the strength of the casting, and at the same time bring difficulties to the molding; if the wall thickness is too large or severely uneven, it is easy to shrink and crack. As the wall thickness increases, defects such as pores and shrinkage porosity inside the casting also increase, which also reduces the strength of the casting. Therefore, under the condition of ensuring that the casting has sufficient strength and rigidity, the wall thickness should be reduced as much as possible, and the wall thickness should be kept uniform. The wall thickness of the die casting is generally 2.5-4mm, and the parts with a wall thickness of more than 6mm should not be used. Die casting.

2. 3 casting fillet

The intersection of each part of the die casting should have rounded corners (except at the parting surface), so that the metal flows smoothly when filling, and the gas is easily discharged, and it can avoid cracks due to acute angles. For die-casting parts that need to be electroplated and painted, the rounded corners can be evenly coated to prevent the accumulation of paint at the sharp corners.

2. 4 draft angle

When designing die castings, there should be a structural slope in the structure. When there is no structural slope, there must be a process slope for demolding where necessary. The direction of the slope must be consistent with the demolding direction of the casting.

2. 5 stiffener

The function of the stiffener is to increase the strength and rigidity of the part after the wall thickness is thinner, reduce the shrinkage deformation of the casting, and avoid the deformation of the workpiece when it is ejected from the mold. It is used to act as an auxiliary circuit (metal flow path) during filling. ;

The thickness of the die-casting ribs should be less than the thickness of the wall where it is located, generally taking 2/3~3/4 of the thickness of the place. The setting of the ribs can increase the strength and rigidity of the parts and improve the processability of die-casting. But pay attention to the following points:

① The distribution should be even and symmetrical;

② The root connected with the casting must have rounded corners;

③ Avoid multi-rib crossing;

④ The width of the rib should not exceed the thickness of the wall to which it is connected. When the wall thickness is less than 1.5mm, reinforcing ribs should not be used;

⑤ The demoulding slope of the ribs should be greater than the allowable casting slope of the casting cavity.

The size of the generally used reinforcement ribs is selected as follows:

The ratio of the maximum wall thickness to the minimum wall thickness should not be greater than 3:1 (the wall thickness should be designed to be uniform to ensure sufficient strength and rigidity).

2. 6 Die-casting holes and the minimum distance from the hole to the edge

1) Cast hole

The minimum size and depth of the hole that can be cast by a die-casting part is restricted by the distribution position of the core-forming the hole in the cavity. The thin core is easy to bend or break when pulled out, so the minimum size and depth of the hole are subject to certain restrictions. The depth should have a certain slope to facilitate core pulling.

The diameter and depth of the die casting can be directly pressed out for the less demanding holes.

2) The minimum distance from the hole to the edge

In order to ensure that the casting has good molding conditions, certain wall thickness should be maintained from the casting hole to the edge of the casting.

2. 7 texts, logo, pattern

1) It is cast by die-casting and should be embossed. The height of the relief is greater than 0.3m to suit the characteristics of mold manufacturing.

2) 2) Adopting a new technology that has become popular at present: "Transfer Color Film", which can transfer colored words, logos, and patterns to the surface of die castings.

3) After die-casting the casting, use laser to print text, logo and pattern on the surface of the casting, which can print very fine text.