Additive metal manufacturing is a “disruptive technology,” that will change a lot of the manufacturing landscape, according to Mark Meyer, leader of GE Additive. Just as taxi service often improves when Uber and Lyft move into town, metal casting is being enhanced as additive competes with casting. And Meyer believes additive will soon compete with metal forging, so forging processes may be similarly enhanced in response.
The present focus on additive metal manufacturing has been on new builds. But the same or similar techniques can be used in the replacement market for parts. Indeed, additive techniques are now being used to make plastic replacement parts faster and more efficiently than traditional methods. The same pattern should eventually follow in metal additive.
In any case, GE is going all in for additive. It has acquired Arcam EBM, which does electron beam melting, Concept Laser, which does laser melting, and additive material provider AP&C. Meyer stresses the advantages of additive for aerospace uses and the special advantages of the electron beam process.
GE has been doing a kind of additive manufacturing for years, when it repaired tips of turbine blades by welding bead on top of bead. But the new additive manufacturing methods start with 3D computer models of new parts, slice these models, produce the slices and then join the slices for the whole part. As with traditional manufacturing, substantial processing must then be done to finish the part.
Additive manufacturing can make some parts “better, faster, cheaper,” Meyer says. It is especially useful in designing new parts, because it enables designers to “fail faster,” that is test and modify preliminary designs to optimize design.
And most distinctively, with additive techniques production costs do not go up with part complexity, as they do for traditional manufacturing. So, for example, GE can design a highly complex one-piece turbine frame that previously consisted of 300 separate parts.
The electron beam melting of additive manufacturing has good speed, precision and size capabilities, Meyer says. Speed counts for economy. Precision reduces expensive processing work. And size means larger parts can be made. EBM is also a hot process, which reduces stress in the fabricated part. And EBM penetrates deeper than laser, so thicker parts can be made. Finally, EBM uses coarser powders, which tend to be cheaper.
GE is working on additive techniques for all five categories of engine parts, including the most demanding category, the hot-section parts that must tolerate temperatures in excess of 1,500 degrees Fahrenheit. In principle, additive can be used for any metal that can be turned into powder, but it takes a lot of work to prove and certify both the powder and the additive machine for specific aerospace uses, Meyer notes.
GE has used additive to build the combustor liner for its CT7 engine and a low pressure turbine blade for the GE9X, “the first rotating engine part made by additive,” Meyer says. And for GE’s advanced turboprop engine, additive will make 16 parts, including a heat exchanger that consolidated 80 parts into one.
So additive is coming, both to new engines and other aircraft components, and eventually to the aftermarket as well. Will the larger, more complex parts built with additive be more expensive to replace than a much smaller part might be when failure occurs? Probably. On the other hand, these larger complex additive parts may be repairable by additive techniques as well. In any case, the efficiency gains of additive are so large that some penalties would be well worth paying.