08-16-2017, 09:59 PM
Abstract
Laser assisted direct metal deposition refers to the additive layered manufacturing technology for building components from a
computer-aided design CAD. model. A motion control program, developed from the CAD model of a desired metal component,
is used to control the motion of a laser focal spot to trace all areas of the part, typically a planar layer at a time. Metal powders,
injected into the laser focal zone, are melted and then re-solidify into fully dense metal in the wake of the moving molten pool
created by the laser beam. Successive layers are then stacked to produce the entire component volume of fused metal
representing the desired CAD model. Development of this technology has been pursued at both Los Alamos and Sandia National
Laboratories and has resulted in the Directed Light Fabrication DLF. and Laser Engineered Net Shaping LENSTM. processes.
These processes have been proven feasible for fabricating components from nearly any metal system to near-net shape accuracy
with mechanical properties approaching and in some cases exceeding the properties found in conventionally processed wrought
structures. Single step processing by LENS and DLF produce cost savings realized by elimination of conventional multi-step
thermo-mechanical processing. Design features such as internal cavities or over-hanging features can be made without joined
assemblies. Hard to process materials such as intermetallics, refractory metals, and high temperature alloys can be processed in a
single step. Functionally graded compositions can be created within three-dimensional components to vary the properties to
match localized requirements due to the service environment. The technology offers the designer a rapid prototyping capability at
the push of a button, without the need to fabricate dyes or use forming equipment or extensive machining and joining processes
to produce a part. Future development is still required for these processes to be commercially accepted and used in industry.
Parts are deposited with a surface roughness of 10 mm, arithmetic average, making a secondary finishing operation necessary for
some applications to achieve high accuracy and polished surface texture. Residual stress measurement and control is also
required to avoid distortion of deposited components. Motion path and control code needs to be optimized to reduce overall
process time from the CAD model to the finished part. Q Published by Elsevier Science Ltd. All rights reserved.
Keywords: Laser; Deposition; Fabrication; Layered deposition; Rapid prototyping; Solid free-form fabrication
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