Die casting design guide and tips
If you want to make better die casting products, you can refer to these principles provided by this article.
Consistent wall thickness is required for a better design
In fact, the wall thickness of the die casting also has a great influence on the quality. Taking aluminum alloys as an example, thin walls have higher strength and good compactness than thick walls.
Therefore, when the die-casting parts have sufficient strength, the wall thickness should be reduced as much as possible, and the wall thickness should be kept uniform.
If the wall of the casting is too thin, it will lead to poor metal welding, which will affect the strength of the casting, and it is not easy to form.
Cracks may occur if the wall thickness is too large, or if it is severely uneven. As the wall thickness increases, the defects such as pores and shrinkage inside the casting will also increase, which also reduces the strength of the casting.
- Zinc alloy 0.3mm (minimum); aluminum alloy 0.5mm (minimum)
- Minimum hole 0.7mm
- The minimum thread distance is 0.75mm
- Maximum wall thickness and minimum wall thickness should not exceed 3:1
It will be clearer according to the table:
| area at wall thickness | Zinc alloy | Aluminum alloy | magnesium alloy | copper alloy | ||||
|---|---|---|---|---|---|---|---|---|
| wall thickness h（mm） | ||||||||
| minimum | normal | minimum | normal | minimum | normal | minimum | normal | |
| ≤25 | 0.5 | 1.5 | 0.8 | 2 | 0.8 | 2 | 0.8 | 1.5 |
| ＞25~100 | 1 | 1.8 | 1.2 | 2.5 | 1.2 | 2.5 | 1.5 | 2 |
| ＞100~500 | 1.5 | 2.2 | 1.8 | 3 | 1.8 | 3 | 2 | 2.5 |
| ＞500 | 2 | 2.5 | 2.5 | 4 | 2.5 | 4 | 2.5 | 3 |
Larger fillets are used at the intersection of sidewalls, ribs, and protrusions.
In order to enhance the strength of the parts, prolong the life of the mold and improve the fluidity of the metal, larger rounded corners will be used in the intersection of the side walls, ribs and protrusions.
Ribs
Reinforcing ribs can increase the strength and rigidity of parts, and can also improve the manufacturability of die casting. requires attention:
- The distribution should be evenly distributed;
- The root of the eider connected to the casting should have rounded corners;
- Avoid multi-rib crossing;
- The width of the ribs should not exceed the thickness of the connected walls. When the wall thickness is less than 1.5mm, reinforcing ribs should not be used
- The drafting slope of the reinforcing ribs should be greater than the casting slope allowed by the inner cavity of the casting
Rounded corners
The intersection of each part of the die-casting part should have rounded corners (except at the parting surface), so that the metal can flow smoothly when it is filled, the gas can be easily discharged, and cracks caused by sharp corners can be avoided.
For die castings that require electroplating and finishing, rounded corners can be uniformly coated to prevent paint build-up at sharp corners.
The fillet radius R of die-casting parts should generally not be less than 1mm, and the minimum fillet radius is 0.5mm.
| Die casting alloy | Corner radius R | Die casting alloy | Corner radius R |
|---|---|---|---|
| Zinc alloy | 0.5 | Aluminum-magnesium alloy | 1 |
| Aluminum tin alloy | 0.5 | copper alloy | 1.5 |
Draft angle
Under normal circumstances, after the die-casting is formed, during the parting, the die-casting part is left on the side of the movable mold, and the movable mold refers to the rear film. In order to prevent the die-casting from being damaged and deformed and to be demolded smoothly, it is necessary to select the correct and reasonable demoulding method according to the structural characteristics of the die-casting, and determine the position and size of the exit part and the reset rod.
For some more complex die-casting parts, there is no way to completely demould after one push, and it is necessary to use multiple demoulding to determine the structural form and action sequence.
The side concave and convex parts of the die-casting parts should adopt the side core pulling mechanism. The side core pulling mechanism should be selected on the basis of economy and practicality.
If the batch of products is not large, a simple side core-pulling form can be used; if a manual core-pulling mechanism and an out-of-mold core-pulling mechanism with a movable core are used, manual core-pulling can be used after the mold is opened.
When the side core-pulling mechanism driven by the mold opening force or external force must be used, after calculating the core-pulling force, an appropriate side-pulling mechanism can be selected and the dimensions of the main structural parts are determined.
Cast hole and minimum distance from hole to edge
The hole diameter and hole depth of die castings can be directly pressed out for holes with low requirements.
| Minimum aperture d（mm） | Maximum hole depth（mm） | Minimum slope of the hole | |||||
|---|---|---|---|---|---|---|---|
| common | special | Blind hole | through hole | ||||
| d＞5 | d＜5 | d＞5 | d＜5 | ||||
| Zinc alloy | 1.5 | 0.8 | 6d | 4d | 12d | 8d | 0~0.3% |
| Aluminum alloy | 2.5 | 2 | 4d | 3d | 8d | 6d | 0.5%~1% |
| magnesium alloy | 2 | 1.5 | 5d | 4d | 10d | 8d | 0~0.3% |
| copper alloy | 4 | 2.5 | 3d | 2d | 5d | 3d | 2%~4% |
Minimum distance from hole to edge
In order to ensure that the casting has good forming conditions, a certain thickness should be maintained from the casting hole to the edge of the casting.
| Alloy class | Lead-tin alloy | Zinc alloy | Aluminum alloy | magnesium alloy | copper alloy |
|---|---|---|---|---|---|
| Maximum depth H | ≈10 | ≈12 | ≈10 | ≈12 | ≈10 |
| thickness h | ≈10 | ≈12 | ≈10 | ≈12 | ≈8 |
Inserts in die castings
Has the following purposes:
- Improve and improve local process performance on castings, such as strength, hardness, wear resistance, etc.;
- Some parts of the casting are too complicated, such as the depth of the hole, the inner concave, etc., which cannot come out of the core and use inserts;
- Several parts can be cast into one.
Sandblasting and Shot Peening
Sandblasting can improve the aesthetics of the die-casting surface. If there are requirements for the appearance of die-casting parts, sandblasting can be done first and then oil injection.
Shot peening has the function of sandblasting and can also increase the strength of the casting.
Surface oxidation
Oxidation is generally used on the surface of aluminum alloys, which can improve the anti-corrosion ability. For those with high requirements for anti-corrosion ability, the surface is generally chromed first, and then painted. There are two kinds of surface chroming: colorless and yellow chromating, mainly to form a thin chromating layer on the surface, and the colorless chromating can withstand 24 hours of conventional salt spray test.
Surface plating or electroless plating
In order to have a better appearance, chrome or nickel plating will be chosen. The requirements of electroplating on die-casting parts are actually very high, and the surface finish must reach 1.6. Therefore, when designing the structure, it must be considered that the wall thickness should be uniform, and should not be too thick, generally no more than 4mm, and try to use a large rounded transition. At the same time, the mold requires a reasonable runner, overflow, and exhaust design.
Surface spray
The surface spraying is generally oil spraying and powder spraying. The main purpose is for appearance or anti-corrosion. The main performance testing indicators of the coating are coating thickness test, adhesion test and salt spray test.
This article was re-edited on May 29, 2023