Near Net Shape Rapid Manufacture & Repair by LENS

Components and systems manufactured from advanced materials such as titanium alloys, superalloys or special steels are critical to the performance of the armed forces. However, utilising performance materials presents several challenges. By their very nature, they are difficult, costly and time consuming to process. The main manufacturing routes of casting, forging and machining typically exhibit long lead times, extreme Buy-to-Use ratios and, being tool based, inherently inflexible. This seriously impacts on systems affordability and development times. Defence manufacturing is low volume with production runs being typically limited to a maximum of several thousand parts. In some cases, a series of prototype parts, constantly evolving in design need to be manufactured. Production runs of many components may be less than ten or twenty units before they are updated. In the case of re-manufacturing legacy parts single components may be required. Consequently, high set up and tooling costs are therefore only amortised over a small number of components, driving up procurement cost. During operation components produced from advanced materials operate in severe environments and suffer from rapid wear and damage. Quite often, existing repair procedures cannot cope with these difficult to work materials. The only alternative replacement at high cost, driving up total life cycle costs and draining military budgets and natural resources. As an example of the scale of this problem, the US Military’s maintenance operations support more than 500 ships, 16,000 aircraft, 50,000 ground vehicles, and other military assets at a cost of greater than $40 billion annually. The high cost of maintenance puts a severe drain on military budgets. With defence departments now looking to extend systems lifetimes beyond the original designed lifetime, the need for effective repair techniques is becoming increasingly important. Over the last 10 years, CAD driven, additive manufacturing technologies have been developed. The leading technology for defence applications is Laser Engineered Net Shaping (LENS).Since its conception at Sandia National Laboratory and during it’s commercial development by Optomec Inc., it has been focussed on Near Net Shape (NNS) rapid manufacture, modification and repair of components in advanced materials. The process creates/repairs fully functional parts, in a wide array of alloys including titanium, nickel, cobalt, steel and novel materials such as Metal Matrix Composites and Functionally Gradient Materials. This paper will review the State of the Art for the technology and present application case studies where LENS is being applied to vehicle technology in the defence industry. In addition, case studies from other industries will be shown, from which benefits could be applied to the defence field. Particular focus of the Hedges, M.; Calder, N. (2006) Near Net Shape Rapid Manufacture & Repair by LENS. In Cost Effective Manufacture via Net-Shape Processing (pp. 13-1 – 13-14). Meeting Proceedings RTO-MP-AVT-139, Paper 13. Neuilly-sur-Seine, France: RTO. Available from: http://www.rto.nato.int/abstracts.asp. Near Net Shape Rapid Manufacture & Repair by LENS 13 2 RTO-MP-AVT-139 UNCLASSIFIED/UNLIMITED UNCLASSIFIED/UNLIMITED paper will be on material quality and the time, cost and quality benefits obtained in current and future applications. The paper will also discuss the future direction of technology developments to further establish this technology as a fully approved manufacturing and repair technique. 1.0 LENS PROCESS AND MATERIALS PROPERTIES. Figure 1 shows the stages involved in the LENS process. First the engineer designs the part using CAD. The resulting STL file is then processed using the proprietary PartPrep software which turns the CAD data into a digital tool path. This tool path drives the laser, at the heart of the process. The Work Station Control software controls the manufacturing process with the ability to adjust processing parameters in real time. A schematic representation of the process is depicted in Figure 2. The process, uses a high power laser (Nd:YAG or Fibre laser) focused onto a metal substrate to create a molten melt pool. Powder is then injected into the melt pool to increase the material volume. The deposition head is then scanned relative to the component to write lines of the metal with a finite width and thickness. Rastering of the head back and forth creates a pattern and fill to complete the layer of material to be deposited. Finally, this procedure is repeated many times until the entire object represented in the threedimensional CAD model is produced. In this fashion, a part is essentially built up from powders to form a solid object. The finished part is Near Net Shape and requires only final surface finishing. The build process is conducted in an inert Ar atmosphere which maintains combined Oxygen and moisture levels to under 10ppm. One area where this process differs for other additive techniques are in the ability to produce a wide range of materials to exacting specifications required by the defence industry, Table 1. The properties obtained by the process in different alloys are comparable [1 & 2] to forged materials, and in some cases exceed them. LENS Work Station Control Software PartPrep Software Fabricated Part Engineering CAD Drawing Deposition Figure 1: Process Steps in LENS Rapid Manufacture. Figure 2: Schematic diagram of the LENS process Near Net Shape Rapid Manufacture & Repair by LENS RTO-MP-AVT-139 13 3 UNCLASSIFIED/UNLIMITED UNCLASSIFIED/UNLIMITED Table 1. Range of Materials Processed. LENS Preferred Alloys Alloy Class Alloy Alloy Class Alloy