Laser Powder Forming

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Laser powder forming (LPF) technologies such as Laser Engineered Net Shaping^TM (LENS ®)* and several others are gaining in importance and are 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 technology 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. However, laser powder forming methods have fewer material limitations than SLS, don't require secondary firing operations as some of those processes do, and can also be used to repair parts as well as fabricate them.

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