Aluminum Rapid Prototyping

Aluminum Rapid Prototyping is a process used to build a prototype or a finished product much quicker than the conventional methods using moulds or dies, which takes weeks. Using this method, where prototypes are manufactured using computer inputs directly, has become very popular in the fabrication of precision parts.

Aluminum rapid prototyping is a layer-based approach. It first creates point-by-point patterns in layers of Aluminum or an Aluminum alloy powder. These layers are then solidified by heat by directing a computer-controlled jet of binder onto selective areas of the layer the pattern of which is dictated by the same computer.

Another layer of the metal powder is then spread on top of the previous layer and the process is repeated until the article is formed and resides in a matrix of unbounded particles. The article is then hardened so that the particles can bind together after which the unbounded particles are separated. At this stage the bonded particles are welded together metal to metal to form the metal core.

Generally a powdered mixture of Aluminum, Magnesium and Nylon is used at the start of the process. The computer guided jet forms the pattern in the layer and the process is repeated until the prototype is formed. At this stage Aluminum is just half of the part by volume.

Aluminum rapidly forms an oxide layer in air that prevents the metal particles form binding together. To prevent the oxidation the part is heated at 540 degrees Celsius in flowing Nitrogen Atmosphere, which helps the magnesium in the powder to absorb the oxygen and prevent the oxidation.

This results in an Aluminum Nitride layer that lets the Aluminum parts to meld together into a skeleton. This is more stable unlike the pure Aluminum prototype and does not distort when infiltrated with the liquid metal to form the solid part thus can be used to fabricate high precision and complex parts.

After the initial heating, it is further heated for six more hours at the same temperature, and during this time the liquid metal is introduced to form the solid part. For Aluminum Rapid Prototyping to work effectively the liquid metal should have its melting point above the temperature at which the skeleton is formed but below the skeleton’s melting point. An alloy of Silicon, Magnesium and Aluminum has been detected with this property.

The Aluminum Rapid Prototyping process can fabricate parts of any size and delicacy, even up to 500 µm across. The ductility and the tensile strength of these parts are about 80% of those produced by the conventional casting methods.

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