LENS (laser near net forming) technology can realize gradient material and complex surface restoration, and is playing an important role in the repair of large devices. It is the bridge between traditional manufacturing and 3D printing. LENS technology is mainly used in aerospace, automotive, ship and other fields, can realize the metal parts of non mold manufacturing, saving costs and shorten production cycle.
Since the advent of LENS (near net forming) technology, it has been favored by industry for its functions of gradient material and complex surface restoration. With these advantages, LENS technology in the repair of large devices are constantly play a role, have become a bridge linking traditional manufacturing and 3D printing.
LENS technology principle
Near net forming technology refers to the forming technology after the parts are formed with only a small amount of processing or no longer processing. Laser near net forming (LaserEngineeredNetShaping, LENS) generates a three-dimensional object by depositing the molten pool in the deposition region by laser and depositing the powder or filamentary material continuously. LENS technology was developed by Sandy laboratories in America (SandiaNationalLaboratory) in 90s of last century, and then the American Optomec company developed LENS technology for commercial development and promotion.
Because LENS technology is independently researched by many universities and institutions, the name of this technology is various. LENS technology is also called laser melting deposition (LaserMetalDeposition, LMD), the University of Michigan is called direct metal deposition (DirectMetalDeposition, DMD), the University of Birmingham is known as direct laser forming (DirectedLaserFabrication, DLF), China Northwestern Polytechnical University professor Huang Weidong called laser rapid forming (LaserRapidForming, LRF). The United States society for materials and testing (ASTM) standards unify the technology as part of the metal direct deposition (DirectedEnergyDepositioin, DED) technology.
In the process of LENS, the computer firstly slices the 3D CAD model according to a certain thickness, and then divides the two-dimensional data of each layer into the track of the NC platform of the printing equipment. The high energy laser beam will generate a pool on the floor, while the metal powder into synchronous melting and rapid solidification, make it a point to a line, from line to plane in order to complete solidification, a layer of printing work section. Thus layers are superimposed to form near net shaped parts and components.
LENS technology is mainly used to print more mature commercial metal alloy powder materials, including stainless steel, titanium alloy, nickel based alloy and so on.
LENS advantages and technical limitations
LENS technology can realize the non mould manufacturing of metal parts, save the cost and shorten the production cycle. At the same time, the technology has solved a series of problems in the traditional manufacturing process, such as the difficult machining, the large amount of material removal and the serious wear of the tool. LENS technology is a direct metal forming method without post-processing. The formed parts are compact and have high mechanical properties, and can be used for the manufacture of heterogeneous and graded material parts.
LENS technology has encountered some bottlenecks, including low utilization of powder materials, large thermal stress in forming process, easy forming of forming parts, low precision of forming parts, and may affect the quality and mechanical properties of parts. Due to factors of laser spot size and worktable movement accuracy limit, the direct fabrication of functional parts size precision and surface roughness is poor, often require subsequent machining in order to meet the use requirements.
LENS technology is mainly used in aerospace, automotive, ship and other fields, for the manufacture or repair of aircraft engines and heavy gas turbine impeller blades, and lightweight automotive parts. LENS technology can realize the repair and remanufacturing of worn or damaged blades, thereby greatly reducing the manufacturing cost of blades and improving the production efficiency.
O.R.Laser, Germany, uses LENS technology to create a hard alloy coating on the surface of sensors to provide reliable protection for sensor components in the oil and gas industry and significantly prolong sensor life. The method can make the material accurately deposited and low thermal permeability, and finally, the sensor is coated with a coating without distortion or crack.