What are the types of die casting? Several problems of aluminum alloy die castings?

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  • May 9,2022
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  • What are the types of die casting? Several problems of aluminum alloy die castings? Die casting includes high pressure die casting (HPDC); low pressure die casting (LPDC); gravity squeeze casting (...

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What are the types of die casting? Several problems of aluminum alloy die castings?

Die casting includes high pressure die casting (HPDC); low pressure die casting (LPDC); gravity squeeze casting (GDC); EMP specializes in high pressure die casting;

types-of-die-casting

Die casting machines are generally divided into cold chamber die casting machines and hot chamber die casting machines.

Cold chamber die casting machines are divided into horizontal die casting machines and vertical die casting machines according to their cavity structure and layout.

Die-Cast-Process

The following is the process flow chart of high pressure die casting: raw material melting, die casting, degassing, deburring, trimming, shot peening, CNC machining, leak test, cleaning, full inspection, packaging and delivery.

1. Die casting comparison

(1) Comparison of process characteristics

Casting Process

Process

Tooling Cost

Tooling Life

Porosity

Heat treatment

Allowance

Surface cleaning

Part

Productivity

HPDC

Complex

High

Short

Poor

No

Small

High

Thin-wall

High

Squeeze Casting

Complex

High

Short

Good

Yes

Small

High

thick-wall

High

GDC

Simple

Low

Long

Good

Yes

Large

Low

thick-wall

Low

CPC

Simple

Low

Long

Good

Yes

Large

High

thick-wall

Middle

LPDC

Simple

Low

Long

Good

Yes

Large

Middle

thick-wall

Middle

 

(2) Comparison of mechanical properties

Die-Casting-Comparison

2.Forming principle of aluminum alloy die casting

(1) Advantages of aluminum alloy die castings

Die-Casting

Aluminum alloy die castings have the advantages of high production efficiency, low processing costs, easy mechanical automation of the production process, high dimensional accuracy of castings, good surface quality, and good overall mechanical properties.

(2) Forming principle of aluminum alloy die castings

Aluminum alloy die castings must be formed by molds and combined with die casting machines and aluminum alloys to be comprehensively utilized. The principle of the die casting process is that molten metal is injected into the cavity of a precision metal mold at high speed under high pressure, and then cooled and solidified into a casting under pressure. Cold chamber die casting and hot chamber die casting are two basic methods of die casting process. In cold chamber die casting, liquid metal is injected into the cold chamber by a manual or automatic casting device, and then the injection punch moves forward and presses the liquid metal into the cold chamber. In the process of hot chamber die casting, the pressure chamber is perpendicular to the crucible, and the molten metal automatically flows into the pressure chamber through the feed port on the pressure chamber. The injection punch moves down, pushing the molten metal into the cavity through the gooseneck. After the molten metal solidifies, the die-casting mold is opened, the casting is taken out, and the entire die-casting molding process is completed.

Die-Casting

In the process of manufacturing aluminum alloy die castings, the surface processing quality of the cavity can be effectively improved. There should be no obvious deep processing marks on the surface of the mold cavity to prevent the mold from cracking due to stress concentration during the working process. After the mold is completed, the cavity surface should be effectively polished and ground to keep the cavity surface roughness below 0.8μm.

3. Several key issues in die-casting mold design

Die-casting mold is an important process equipment in die-casting production. The molten metal cools and solidifies in a die casting mold to form a die casting. The shape, size, quality and smoothness of die-casting production are closely related to the die-casting mold, so it's very important to design a correct and reasonable die-casting mold.

Die-Casting

Die casting mold design should pay attention to the following points:

(1) Try to adopt an advanced and simple structure to ensure stable and reliable operation and facilitate daily maintenance and repair.

(2) Considering the modifiability of the gating system, necessary modifications can be made during the commissioning process.

(3) Reasonable selection of tolerances, scales and machining allowances to ensure reliable mold fit and required die casting accuracy.

(4) Select the appropriate mold material and reliable heat treatment process to ensure the service life of the die-casting mold.

(5) It should have sufficient rigidity and strength, and be able to withstand the clamping pressure and expansion force during die casting production without deformation.

(6) Use standardized die casting mold parts as much as possible to improve economy and interchangeability.

4. 6 reasons for the strain of aluminum alloy die castings

Die-Casting

Die castings are widely used in all walks of life, and the market demand is huge. However, in the production process, aluminum alloy die castings are prone to scratches, and in severe cases, scratches may occur.

Reasons for drag marks on aluminum alloy die castings:

(1) The mold temperature is higher than 220 degrees, and the casting is easy to scratch or stick to aluminum.

(2) The iron content of the aluminum alloy is less than 0.6%, and the aluminum material has an affinity with the mold, which causes the casting to be scratched or stuck.

(3) The ejection of the casting is not parallel, causing the casting to be pulled or deformed.

(4) The surface of the mold core is rough, causing the surface of the casting to be deformed or rough.

(5) The draft angle of the core and wall of the casting is too small, which causes the casting to be scratched during parting.

(6) Insufficient spraying of release agent will also cause drag marks.

 

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