The constant search to create stronger, harder, more resistant and therefore safer alloys in aeronautics has brought great benefits in these aspects, but it has also brought up a new complication that must be faced: how to machine these materials. Aerospace alloys are difficult to machine and have similar material properties to the tools being used to cut them, which can significantly reduce cutting tool life. As the material properties get closer to those of the cutting tool, either the cutting has to be slowed down to preserve the life of the tool and avoid breakage or stronger tools have to be used, all of which increase production costs.
If today’s machining processes are used in next-generation materials, the intensity of heat generated can deform, chip, and break ordinary cutters. These disadvantages are greater than the benefits, and all the effort spent in the development of these materials loses worth.
Therefore, aerospace companies are very interested in investing in the development of new methods to produce parts for the interior of jet engines, gas turbines, and other devices. Here, we present the latest advances in a cutting and machining method called Blue Arc, and we also introduce 3D metal printing technologies. Both technologies offer a novel way to treat and manipulate new super materials for the production of parts used especially in the aeronautical sector.
Blue Arc: A new cutting technology for superalloy metals
In a search to solve these problems and improve the quality and cost of its individual components, in 2011, GE presented for the first time the GE Blue Arc machining process. This development greatly decreases the conventional cutting time. For example, the machining of an aerospace-grade titanium alloy would be reduced from 45 to 3 minutes, saving $200 million dollars after 5 years of use of the technology. The design eliminates the need for high-power spindles, expensive cutters, and other devices. This technology was patented by GE, and for this reason there are not many other companies involved in its commercialization.
Blue Arc uses a high-speed electron beam to erode and remove metal. As there is high amperage, low-voltage electrical energy between the electrode tool and the workpiece, the workpiece parts are melted, and excess material is removed with high-pressure coolant. The electric arc is produced with a copper-tungsten electrode that can have the shape, diameter, or contour desired — making it very similar to the use of a cutting tool for machining. The technology also has sustainability benefits, as the material removed can be recovered and used for other processes.
Due to the low forces of the Blue Arc, the process can be changed from high-power, high-torque machine tools and highly engineered cutting tools to a smaller, less rigid machine and a simple electrode tool. The process is recommended for the deep, hard-to-reach cuts and very fine cuts commonly found in aerospace, power generation, and automotive applications.
In its search for this new technological development, GE joined with the Japanese company Mitsui Seiki, a producer of machine tools, to unite their knowledge in the area and develop a commercial machine that can quickly and efficiently produce superalloy parts using this new cutting technology. They made their first presentation in 2016 at the International Conference on Information Technology for Manufacturing Systems (IMTS), and then on June 6, 2018, they held a second event for the public hosted by TechSolve at its headquarters in Cincinnati.
The machine developed and presented at the latter event was based on the Mitsui Seiki HW63-TD. It has the particularity of being hybrid, which allows it to perform machining with both Blue Arc and conventional machining on the same platform.
Metal 3D printing for the aerospace sector:
Today, 3D printers have gradually reached most sectors that involve the development of high technology, such as space, health, construction, and many others. This method is currently used mainly in the industrial sector to create tooling components or finished parts, for example:
- In the aerospace sectors, it is capable of producing aircraft or rocket engine components
- In the automotive sector, it can produce molds for the mass injection of thousands of components
- In the medical sector when it comes to creating implants, especially in the dental field
- In the marine sector, additive metal fabrication can even be used to design propellers for ships.
This process of building materials differs from the traditional way or the new Blue Arc method of cutting a solid block precisely because it does not perform cuts, drilling, or machining, but instead gives shape to a piece through the addition of different layers of materials, as its general name of additive manufacturing (AM) implies.
Companies offering 3D metal printers:
More and more companies are embarking on 3D metal printing. Among the leading manufacturers of 3D metal printers, we find:
- The American company 3D Systems, which now offers a complete range of machines;
- SLM Solutions, an important supplier of this technology for the automotive and aviation sector;
- Arcam, the company behind electron beam fusion technology since 2000. Arcam manufactures fridge-size 3D printers that use electron beams to weld millions of grains of metal in a state of fine dust, one thin layer at a time, to build things like intricately detailed jet engine parts.
On the other hand, we also find companies like Desktop Metal that offer smaller and cheaper complete systems for a smaller or scale production. This company offers a machine called the Studio System+ that can even be installed at home. They also have machinery for mass production, as well.
The Studio System+. Source: Desktop Metal.
Markforged is another recently established company that also offers various printing systems, with its Metal X machine capable of creating pieces of 250x220x200 mm.
The Israeli company XJet provides nanoparticle jetting, which can reduce costs and time in advanced metal printing. To print, it uses a fluid ink containing metallic nanoparticles that are injected onto the construction tray and accumulated in layers in a conventional way. From this first step, the fluid evaporates due to the high temperatures of the construction chamber, leaving only the solid metal part.
Tennessee’s Oak Ridge National Laboratory (ORLN) recently presented its advances in a new way of producing materials that are exposed to high pressure and heat stress using 3D metal printing. This technology combines the design flexibility of 3D printing with the mechanical properties of metal to produce elements with great precision, controlling the properties of metals by managing temperature gradients and better understanding their microscopic structure, which allows researchers to study their properties of hardness, durability, or weight.
In this constant quest to produce more advanced and safer materials, GE recently announced a 5-year cooperation agreement with ORLN to combine its laboratory expertise with real-world applications. This agreement is an extension of a joint project with Arcam, which was acquired by GE in 2016.
The last commercial launch of this 3D printer company was the Arcam EBM Spectra H, produced at the Arcam plant near Gotemburg, Sweden. Today, electron beam fusion remains the only commercial additive manufacturing method capable of supporting the production requirements of titanium aluminium (TiAl), an alloy that requires high temperatures for its manipulation and is very prone to cracking. Initially, the Arcam EBM Spectra H will support TiAl and Alloy 718, and additional Ni superalloys were slated to be compatible 2019.
Conclusions:
The aerospace and defense sectors can now benefit from novel technologies that offer numerous advantages for the machining of parts. It is evident that in the field of 3D printing, there is greater technological development compared to the Blue Arc technology, due to the large number of organizations working on these problems.
We can conclude that both technologies are presented as great solutions to support and complement the development of super materials, reduce costs, and increase the reliability of finished parts used in the aeronautical sector.
