Abstract
Manufacturing sectors are shifting their interest toward additive manufacturing technologies, where components are fabricated directly from CAD models layer by layer. Laser engineered net shaping most known to produce a near net shape of functionally graded materials. In this paper, process parameters that affect mechanical properties, surface topology and physical properties are reviewed. Powder feed rate, hatch distance and layer thickness more related to porosity of the parts that are being produced. Mechanical properties are get affected by laser power and scan speed. Hardness is sensitive to focal distance of the optimal convergence of the maximal laser intensity and the localized spatial concentration of the powder beam. To get homogeneous microstructure shorter focal distance is preferable. However, working distance has no such impact on density.
Keywords: Additive manufacturing, laser power, scanning speed, focal distance.
Introduction
A three-dimensional object is primarily created utilizing the highly developed fabrication technique known as additive manufacturing (AM), which builds an object layer by layer. Charles Hull’s invention of stereo lithography, later known as AM technology, received the first acknowledged patent. In addition, he is credited with creating the STL model format for standardized interface, which bears the same name as this manufacturing method. Because AM has so many advantages over traditional manufacturing processes like casting and machining, it is becoming more and more popular. There can be significant savings in raw material use and waste when designs are created additively rather than subtractively. The use of additive manufacturing engineers increased utilization of design freedom, manufacturing time and cost part inspection reduced and counts radically reduced. Furthermore, components produced on demand, reduce responsive time and storage needs.
Over the last four decades, scientific and industrial research has enabled significant advances in additive manufacturing, allowing the production of a variety of products made of polymers, metals, ceramics, and composites with unviable or even impossible geometries by other processes. The LENS machine is a ”real” direct-metal Rapid Prototyping technique, producing items made of full strength metals. Based on the Cooperative Research and Development Agreement, Sandia National Laboratories and various other organizations produce it (CRADA). Direct Energy Deposition (DED), Direct Light Fabrication, Direct Laser Deposition, Direct Laser Fabrication, Laser Rapid Forming, and Laser Solid Forming are some of its synonyms. The geometric data in a Computer-Aided Design (CAD) solid model is used by LENS 3D printers to autonomously control the LENS process as it builds a component layer by layer. Powdered metals are fused together by the systems into completely dense three-dimensional structures using high-power lasers. In order to prevent impurities from picking up during deposition, the LENS process is contained in a chamber that is purged with argon so that the oxygen level stays below 10 parts per million. The Optomec patented powder-feed mechanism, which can flow small volumes of powder very accurately, feeds the process with the metal powder. Once finished, the component is removed and can be machined, heat-treated, or polished in any other way.
LENS is a highly focused metal deposition technology that creates an extremely small weld bead, exposing the component to far less heat than traditional techniques. Stainless steel alloys, nickel-based alloys, tool steel alloys, titanium alloys, and other speciality materials have all been used to produce parts, in addition to composites and functionally graded material deposition. The LENS components are fully dense and exhibit no compositional degradation, according to microscopy studies. Outstanding as-fabricated mechanical qualities are revealed through mechanical testing.
Laser engineered net shaping has the following benefits:
Excellent material qualities: Fully dense metal components can be created using the LENS technique. Produced metal parts may also include embedded features and improved material characteristics. The microstructure created is likewise generally of good quality.
Complex components: The LENS system excels in functional metal components with intricate details.
Less post-processing is needed: Cycle time is shortened by decreasing post-processing.
The limitation of LENS technique are:
Limited resources: Currently, the method is exclusively utilized to create metal components.
Size of a large physical unit : To house the unit, a sizable space is needed.
Heavy electricity usage : The watts needed by the laser system is very high.
There are a number of applications for LENS technology.