Additive manufacturing (AM), aka 3D printing, has emerged as the first manufacturing revolution of the 21st century. Unlike subtractive manufacturing methods that remove material from a billet, metals AM builds up functional end products or product features layer by layer. This building-up process can provide many advantages over subtractive methods, including increased design flexibility, improved end-product performance, reduced time to market, lower manufacturing cost, and extended product life. These advantages are driving interest in AM technology for applications throughout the product lifecycle, from new product development, to low-volume manufacturing, to product repair.
Using powder metals AM, new products can be developed and manufactured with material properties and geometries that are difficult or impossible to achieve with subtractive methods. Novel materials can be created by blending two or more powders to form new alloys and composites to meet specific design challenges. The combination of the powders even can be changed gradually during the build process to create functionally graded materials tailored to avoid corrosion, fatigue, fracture, and stress cracking.
In addition, AM technology can be used to 3D-print metal parts with internal cavities, such as cooling channels, or shrouded features that are lighter in weight and have improved integrity over joined structures. The AM process also can produce parts with excellent mechanical properties. The European Aeronautic Defence and Space Corporation (EADS) conducted a High-Cycle-Fatigue test program to evaluate properties of titanium samples produced using an Optomec LENS 3D printer. EADS found that the samples' mechanical properties were usually equivalent to wrought metal and that their fatigue properties met aerospace standards. Tests have also been conducted by a variety of sources on other LENS-printed metals, including stainless steel and super-alloys such as Inconel.
Traditional subtractive manufacturing processes often involve numerous fragmented steps, as well as associated capital equipment and logistics requirements. By contrast, AM effectively produces the bulk of a desired component or product feature in a single continuous step, thereby reducing the overall number of operations and saving cycle time and cost. Also, since the AM process is driven directly from a 3D CAD model, no hard tooling is required for prototyping or production, which further reduces cost and time to market for new designs and design revisions. In addition, AM processes deposit material only where required, thereby reducing wastage. This is especially important in the use of higher-value materials such as titanium and super alloys, where there's a strong drive to use materials efficiently.
The aerospace industry defines material efficiency as the "buy-to-fly" ratio, which is a measure of the original billet weight to the weight of the finished part. Using traditional subtractive manufacturing methods, aircraft engine manufacturers have reported up to 85% material wastage for simple parts and up to 95% wastage for complex parts. Hence, aircraft engine manufacturers are especially motivated to use material-efficient AM methods for these high-value components. Some companies even combine the use of AM and subtractive methods into a hybrid manufacturing process to take advantage of what each process does best. For example, the amount of time needed to build a stainless-steel electronic housing was reduced from 52 weeks for an entirely cast part to 3 weeks. This was achieved by machining the base housing and building up the vertical details directly on the housing using AM methods.