Metal shapes on demand

A professor at Lehigh University has put a new spin on rapid prototyping by creating device that turns a computer aided drawing into a 3D object constructed from metal powders.

John DuPont, assistant professor of materials science and engineering at Lehigh University is studying ways that complex metal objects and parts are made to materialise almost by the flick of a switch.

DuPont calls his project Laser Engineered Net Shaping (LENS), in which computer-aided drawings of objects are transferred from the computer to a specialised laser machine. The object is then constructed from metal powders laid down on a substrate.

The heart of the process is the laser machine that has four nozzles positioned around a laser beam. The beam melts the surface of the substrate and the nozzles deposit powdered metallic material that goes down layer by layer into a molten ‘liquid.’ As the material solidifies the object slowly takes shape. The laser remains stationary while the substrate turns on a special table.

The process is said to have advantages because the object can be made from almost any kind of metallic powder and its composition and properties can be changed during fabrication. The process also allows for the creation of objects in nearly unlimited shapes because the laser follows the instructions of the computer.

DuPont said LENS will fill a substantial niche in the manufacturing sector and can be used to create a vast number of products. He cites, for example, the production of prototype dies, or moulds, used in the manufacture of plastics.

Currently, a prototype die is machined and welded in a multi-step process. It must then be ground and polished and dipped in anti-corrosive coatings. The process can take up to six months and incurs high financial costs.

With the LENS process, however, the die is made in one step and the laser has the capacity to create a myriad of possible shapes, said DuPont. And because LENS can deposit different metals, the coating is laid down as the object is fabricated.

DuPont notes that dies used in the fabrication of plastic objects come with drilled channels through which water passes to cool the mould during the manufacturing process. However, the machining process allows only for straight channels. Yet curved channels of many shapes and sizes are desired because they provide more surface area in which to dissipate heat. LENS is said to allow intricately curved channels to be fabricated while an object is being made.

DuPont said products made with LENS would be relatively small and the process is useful primarily for limited production runs of high-performance parts.

DuPont cites jet engine restoration as a potential application for LENS as the tips of the blades wear as they rub against a shroud. Tips are currently restored by conventional welding and then machined back into shape. With LENS, the restoration would be completed in one process and the amount of machining would be greatly reduced.

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