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Laser Engineered Net Shaping (LENS) is a technology that is gaining in importance and in early stages of commercialization.
A high power laser is used to melt metal powder supplied coaxially to the focus of the laser beam through a deposition head.
The laser beam typically travels through the center of the head and is focused to a small spot by one or more lenses.
The X-Y table is moved in raster fashion to fabricate each layer of the object. The head is moved up vertically as each
layer is completed. Metal powders are delivered and distributed around the circumference of the head either by gravity,
or by using a pressurized carrier gas. An inert shroud gas is often used to shield the melt pool from atmospheric oxygen
for better control of properties, and to promote layer to layer adhesion by providing better surface wetting.
A variety of materials can be used such as stainless steel, Inconel, copper, aluminum etc. Of particular interest are
reactive materials such as titanium. Materials composition can be changed dynamically and continuously, leading to objects
with properties that might be mutually exclusive using classical fabrication methods.
The strength of the process lies in the ability to fabricate fully-dense metal parts with good metallurgical properties at
reasonable speeds. Objects fabricated are near net shape, but generally will require finish machining. They have good grain
structure, and have properties similar to, or even better than the intrinsic materials. Selective laser sintering is at
present the only other commercialized RP process that can produce metal parts directly. LENS has fewer material limitations
than SLS and doesn't require secondary firing operations as some of those processes do, however.
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