Aluminum Gravity Die Casting

Aluminum Gravity Die Casting In Dolin

In 2000, we built up our gravity die casting line to enhance our aluminum casting capablity. By now, we have 6 sets of tilted gravity die casting machines, which enable us produce 3 tons castings each day. The weight ranges from less than 1kg to 100kg/pcs. Our products span automotive parts, medical devices parts, electrical enclosures/housings, hardware tool parts, etc.

As a leading aluminum foundry, we design and manufacture the molds by ourselves. We have the ability of mold designing, machining and assembly, which makes us more flexible and efficient when serving our customers. For some castings with complex geometries, we also have the ability of numerical computer simulation to help us achieve the most optimized designs. Better designs before mass production helps reduce cost in trial and error through experimentation, and bring designs to production much more quickly.

-Our Material Scope

ASMT Standard: A319, A356, A357, A413
GB Standard: ZL101, ZL101A, ZL102, ZL107
BS Standard: LM6, LM20, LM25
EN Standard: EN AC-42100, EN AC-42200, EN AC-43000, EN AC-43200, EN AC-43300, EN AC-43400, EN AC-44200, EN AC-44300, EN AC-46000, EN AC-46200

What Is Gravity Die Casting Process?

Gravity die casting is a typical permanent mold casting process, in which the molten metal is poured into the pre-heated die cavity and fill up the cavity by the force that comes from earth gravity. This process is suitable for small and medium-sized castings with big quantity, or with less quantity but high quality.

The most popular technology used in this process is tilt pour casting. The whole prosess likes this. The metal is poured into a pouring basin while the mold is in its horizontal position. Then, with a preset cycle time, the casting machine raises to a vertical position, during which allowing the metal to enter the die cavity at a slow, continuous and stable pouring rate. The tilt-pour method is a good choice for general casting purposes because of its feed/gate flexibility which allows for a wide variety of casting shapes.

-Preparation before Pouring

Mold Manufacturing
Gravity die casting process is often referred to as ‘permanent mold casting’. Unlike sand casting process, this process allows a single set of dies can be reused to produce the same castings. That requires the mold must be made of heat-resistant metal which can withstand repeat thermal shock from molten aluminum alloy.
Making Sand Cores
Like sand casting but unlike pressure die casting, gravity die casting allows inserting sand cores in the die to form the inside structure of a casting. Sand core is fabricated by utilizing manual labor or machine to fill the resin sand into the sand core box. After sand core is solidified, open the core box and get the sand core.
Metal Smelting
Metal smelting is carried out by utilizing smelting furnace to smelt metal alloy. The aim of smelting process is to get pure molten metal alloy with qualified chemical property and right pouring temperature.

-3 Steps to Accomplish A Typical Gravity Die Casting Process

Step 1: Assembling The Die

The die is heated up, inserted with sand core (if has), sprayed with mold release agent, and closed. Then, fill the pouring basin with molten metal alloy and get ready for pouring. After all of these done, the die is tilted to its pouring side. (Sand core is used to form the inside structure of a casting. The mold release agent both helps control the die temperature when pouring and it helps remove the casting after solidification.)

Step 2: Tilting & Pouring

After the pouring basin is filled, the die is controlled by the casting machine tilting towards its normal position moderately and steadily. During this process, the molten metal in the pouring basin is flowing into the die cavity through the runner and the gate in a low and steady feeding speed. Tilting gravity die casting can help reduce and avoid flow turbulence effectively when pouring. No turbulence means no air inclusions in the casting structure.

Step 3: Cooling & Demolding

At the end of the pouring, the air in the die cavity is driven out through the feeders, and the hottest molten metal will occupy the highest positions of the die as feeders. The casting start cooling and solidify gradually, during which the molten metal in the feeders will continuously feed the shrinkage of the casting. When the casting is solidified thoroughly, open the die, get the casting, clean up the die and get ready for next pouring.

-The Advantages of Gravity Die Casting Process

Compared with sand casting, gravity die casting parts have better accuracy in dimensions, better surface finish, higher production efficiency, and higher strength with the condition pouring the same metal. Besides, the performance in air-tight test is outstanding. Take aluminum alloy for example, the airtightness of the castings can reach 50kg/cm2 after T6 heat treatment.

Compared with high pressure die casting, gravity die casting is use to produce parts that are heavier in weight, larger in size, more complex in structure. Besides, molds for gravity die casting are much cheaper, however the quality of parts made by this process is approaching the quality of parts made by high pressure die casting.

-The Disadvantages of Gravity Die Casting Process

The mold, made of heat-resistance steel, can be repeatedly used and has a long usage life. The mold cost of gravity die casting is much higher than sand casting mold, that means this process is only suitable for medium-production and large-production runs of products. The mold material is heat resistance, but still with a limit, which makes this process mostly applied for nonferrous metal (such as aluminum alloy, zinc alloy, magnesium alloy etc.) with low-melting-point.