Product Craft
1. CLAMPING
The molten metal, which is maintained at a constant temperature in the furnace, is next transferred into a chamber from where it can be injected into the die. The method of transferring the molten metal is dependent upon the type of die casting machine, whether a hot chamber or cold chamber machine is being used. Once transferred, the molten metal is injected into the die at high pressures. Typical injection pressure ranges from 1,000 to 20,000 psi. This pressure holds the molten metal in the dies during its solidification. The amount of metal that is injected into the die is referred to as the shot. The injection time, is the time that is required for the molten metal to fill all of the channels and cavities in the die. This time is very short (typically less than 0.1 seconds) to prevent the premature solidification of any one part of the metal. The proper injection time can be determined by the thermodynamic properties of the material, as well as the wall thickness of the casting. A greater wall thickness will require a longer injection time. In cases where a cold chamber die casting machine is being used, the injection time must also include the time to manually ladle the molten metal into the shot chamber.
2. INJECTION
Extruded aluminium with several hollow cavities; T slots allow bars to be joined with special connectors.
Hollow cavities within extruded material cannot be produced using a simple flat extrusion die, because there would be no way to support the center barrier of the die. Instead, the die assumes the shape of a block with depth, beginning first with a shape profile that supports the center section. The die shape then internally changes along its length into the final shape, with the suspended center pieces supported from the back of the die. The material flows around the supports and fuses together to create the desired closed shape. The extrusion process in metals may also increase the strength of the material.
3. COOLING
The molten metal that is injected into the die will begin to cool and solidify once it enters the die cavity. When the entire cavity is filled and the molten metal solidifies, the final shape of the casting is formed. The die cannot be opened until the cooling time has elapsed and the casting is solidified. The cooling time can be estimated from several thermodynamic properties of the metal, the maximum wall thickness of the casting, and the complexity of the die. A greater wall thickness will require a longer cooling time. The geometric complexity of the die also requires a longer cooling time because the additional resistance to the flow of heat.
4. EJECTION
After the predetermined cooling time has passed, the die halves can be opened and an ejection mechanism can push the casting out of the die cavity. The time to open the die can be estimated from the dry cycle time of the machine and the ejection time is determined by the size of the casting's envelope and should include time for the casting to fall free of the die. The ejection mechanism must apply some force to eject the part because during cooling the part shrinks and adheres to the die. Once the casting is ejected, the die can be clamped shut for the next injection.
5. TRIMMING
During cooling, the material in the channels of the die will solidify attached to the casting. This excess material, along with any flash that has occurred, must be trimmed from the casting either manually via cutting or sawing, or using a trimming press. The time required to trim the excess material can be estimated from the size of the casting's envelope. The scrap material that results from this trimming is either discarded or can be reused in the die casting process. Recycled material may need to be reconditioned to the proper chemical composition before it can be combined with non-recycled metal and reused in the die casting process.
Capabilities
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Typical |
Feasible |
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Shapes: |
Thin-walled: Complex |
Flat |
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Part Size: |
Weight: 0.5g-200KG |
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Material: |
Metal
Carbon Steel
Stainless Steel
Aluminum
Copper
Nickel |
Cast Iron
Lead
Magnesium
Tin
Titanium
Zinc |
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Surface finish -Ra: |
3.2 - 12.5 μmm |
6.3 - 12.5 μmm |
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Tolerance: |
± 0.1 mm |
± 0.05 mm |
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Max wall thickness: |
1.5 - 20 mm |
0.6 - 127 mm |
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Advantages: |
Can form complex shapes and fine details
Many material options
High strengh parts
Very good surface and accuracy
Little need for secondary machining |
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Disadvantages: |
Time-consuming process
High labor cost
High tooling cost
Long lead time possible |
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Applications: |
Turbine blades, armament parts, pipe fittings,
lock parts, hand tools, jewelry |
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