The industrial application of metal 3D printing technology is accelerating. Recently, there have been large orders for metal 3D printing of tens of millions or even nearly 100 million yuan in China. If you have some unique technologies that can solve the core pain points of certain industrial applications (for example, under the premise of ensuring strength performance, high thin-walled, extremely complex and undesirable supporting structures, high aspect ratios, etc.), you can develop new Market business applications, create demand!
Below, we will take the XB-1, the world's first commercial supersonic aircraft (which has received hundreds of millions of dollars in financing), as an example, to explain in detail how unsupported metal 3D printing technology can help realize ultra-complex titanium alloy structures.
In 2019, the Boom Supersonic team established a cooperative relationship with VELO3D for some test parts, and then used the next generation laser powder bed fusion (LPBF) technology to produce some printed titanium alloy parts for XB-1 aircraft testing. These components include:
●The manifold of the variable bypass valve (VBV) system is mainly used to transport the air released by the engine compressor to the outer mold line (OML) of the aircraft;
●The exit louvers of the environmental control system (ECS) cool the cockpit and system compartment; the louvers guide the secondary airflow from the central air inlet to the OML;
●As well as NACA pipes and two shunt flange components, NACA pipes are often used in high-speed aircraft to capture external air and lead it into the aircraft to cool the engine compartment.
The Boom Supersonic supersonic aircraft XB-1 cooperates with VELO3D unsupported metal 3D printing technology to manufacture highly complex titanium alloy parts to achieve the requirements of highly thin-walled, extremely complex undesirable support structure, high aspect ratio and other requirements.
All parts are printed on the VELO3D sapphire system.
The only option for complex parts: 3D printing
Many of Boom's 3D printed parts are related to guiding air and contain complex blades, ducts and louvers. Some of the air passing through these components exceeds 500 degrees Fahrenheit. The geometric complexity of these components requires the use of surface-based design methods. Boom engineer Byron Young said: "Fast-moving air that touches the surface will greatly affect efficiency and performance. Therefore, when designing these parts, you usually start with aerodynamic contours, then trim, cut corners and thicken the surface. , Step-by-step modeling. The resulting parts are very complex, which means they definitely need to be manufactured by 3D printing."
In the fall of 2020, Boom Supersonic’s XB-1 supersonic demonstrator was unveiled in the Denver hangar, bringing the dream of supersonic air travel closer to reality. XB-1 demonstrated a more advanced design and manufacturing than the Concorde. The aero engine of Rolls-Royce is used.
In fact, the Boom Supersonic design and engineering team has long known that 3D printed parts have been installed and used on many existing aircraft. At that time, they have begun to consider using additive manufacturing to produce some of the most complex parts.
Young confirmed: "There are many reasons to choose 3D printing technology over other technologies. There is a lot of design flexibility in using 3D printing. Previously, you might manufacture multiple parts and weld or bolt them together, or A similar effect is achieved by using complex carbon fiber tools. But this requires a lot of engineering time and often more manufacturing time."
"Engineers always try to save time at work. Most of the time and energy in aircraft design is spent on the interface between joints and parts. By directly designing for additive manufacturing, we can reduce the number of parts and joints. This also reduces time and workload. And the integration of parts can reduce a lot of weight, which is also the top priority of aircraft design."
VELO3D is a developer of direct metal laser sintering (DMLS) additive manufacturing systems and print preparation software. It invented SupportFree Geometries unsupported metal 3D printing technology and has raised nearly US$200 million.
In almost every case, VELO3D's unsupported metal 3D printer can print Boom's CAD design parts very well without too many defects. Gene Miller, an application engineer at VELO3D, said: "We did use the system's Flow pre-printing software, adding some structural ribs to the thinner wall of the NACA pipe, but there are restrictions. But in most cases, the printed parts The drawing design is restored very highly."
Young said: "The sapphire system allows us to print walls as thin as 20thou (0.02 inches, or 750μ). In most cases, surface treatment is not necessary."
Miller works closely with Boom Supersonic's design engineers and Duncan Machine Products (DMP), which is a supply chain partner that handles printing and post-processing. "Boom has designed all these parts specifically for their new aircraft. The unique geometry types they created to guide the flow are focused on reducing weight. They cannot be done with metal plates or casting or any other means. To get complex at the same time The only option for design and weight reduction is to use metal additive manufacturing."
The high aspect ratio (height to width) brought by VELO3D's non-contact powder spreading system is another advantage. In order to reduce weight, the blades on the vent louver of the central air inlet are hollow printed, and the parts are designed with a high aspect ratio (the walls along the long span are very thin). Miller said: "Because our technology provides the ability to print such a very high aspect ratio in this design, we don't need extra materials to ensure the internal strength of the structure, and we can grow these air duct blades. Very high without interference from the powder spreader."
Pain points for aerospace engineers
All project members believe that one of the biggest challenges of this project is 3D printing parts with Boom titanium alloy. DMP additive manufacturing engineer Aaron Miller said: "Compared with aluminum or carbon fiber, titanium alloy loses less strength at high temperatures, and it has a higher strength-to-weight ratio."
However, titanium, which is lightweight and extremely resistant to high temperatures, is widely used in key components in the entire aerospace industry. There is also a disadvantage. No matter how it is manufactured, it is difficult to process and prone to quality defects. If the cooling rate of titanium is too fast, it will become brittle and easy to crack.
Gene admitted: "Boom has designed a series of brand new metal parts, which really promotes the development of lightweight and thin-walled geometric shapes. We have a lot to learn about 3D printing these titanium alloy parts. How will it move? Where can it be When printing without support, where do I need support?"
This is the key to process control. VELO3D attaches great importance to quality control. The team developed a unique additive manufacturing process that optimized printing parameters and sequences to produce robust titanium parts. Gene explained: "This reduces the internal stress in the substrate because the material is built in the Z build direction. It reduces the possibility of cracking by relieving the internal stress formed during the cooling process."
High-complexity titanium components of XB-1 supersonic aircraft
Quality control runs through the entire manufacturing process, starting with Flow pre-printing software, executed by the sapphire system, and verified by Assure's quality assurance. With just one click, you can perform machine calibration before manufacturing, automatically checking key variables such as laser alignment, beam stability, powder bed quality, etc. In the process, various key indicators are measured and monitored, and these abnormalities are marked. Comprehensive construction reports for all parts will be compiled and saved for future reference.
Aaron said: "After separating from the build plate, apart from the removal of the smallest support, the metal parts we printed have almost nothing to do in post-processing, and there is basically no support, because SupportFree technology eliminates these needs. From The parts coming out of the sapphire system are almost finished products. It only requires a little manual work with a screwdriver or grinder. We will also use a milling cutter to ream pilot holes (on larger parts) to ensure the correct size. It depends Parts, but each part only takes about half an hour to process, which is not a big problem."
The finish machining of the newly released parts was tested with a profiler, and the average record was about 250 RA. Aaron said: "If customers want to achieve 125 RA, they only need to use a steam polisher for a few minutes. So far, Boom has not asked us to increase the surface finish of the parts. They are now focusing on the geometry and the strength of the parts. But if a smoother surface is required, it is easy to achieve."
The three companies worked together to successfully produce 3D printed parts for Boom Supersonic's XB-1 supersonic demonstrator. Everyone has learned a lot from the cooperation. The Boom team found that 3D printing is more complicated than they thought, but it can also achieve their original design intent. DMP also greatly expanded their 3D printing expertise and continued to purchase a third sapphire machine. Aaron said: "Due to our capabilities in additive manufacturing, we have received many new business orders."
Unsupported metal 3D printing technology
Metal additive manufacturing or 3D printing is mainly a welding process that quickly solidifies the molten pool. In the process of solidification and cooling, parts will generate thermal stress and residual stress. Support has two functions: one is as a fixed part, fixing parts to prevent thermal deformation and movement; the other is heat conduction. The temporary support structure is necessary for direct energy deposition (DED) and traditional powder bed fusion (PBF) technology, and usually needs to be removed after the printing is completed. Post-processing increases the cost and prolongs the cycle. More importantly, it limits the design freedom of metal 3D printing.
For decades, metal 3D printing companies have relied on supporting structures to fix parts on build plates and manage heat. In general, we have begun to rely on these supports to assist in printing low-angle structures less than 45°. However, these low-angle geometries are also prone to support in the inaccessible internal passages of the assembly during the part integration process. By using supports to fix the parts on the build plate, the 3D printing is fixed on the prototype design to a certain extent.
VELO3D is different from the existing powder bed welding solutions. It has a unique ability to print low-angle and down to 0° (horizontal) overhangs, as well as large diameter and up to 100mm inner tubes without support. This not only saves the trouble of post-processing, but also overcomes the 45° rule-the angle less than 45° needs support. VELO3D allows designers to build freely, releasing a large number of designs that can be 3D printed.
According to VELO3D, its core technology is the patented re-coater process, called a non-contact scraper. Instead of using the traditional contact scraper spreading mechanism, it uses non-contact technology, which has many benefits. Very good at producing aspect ratio, thin-walled parts, large parts, etc. In short, the blade does not contact the metal powder bed during powder spreading. After the powder is spread, a non-contact scraper process is performed on the powder to ensure that the powder is absolutely flat. Similarly, these are not in contact with the actual bed or parts, achieving a high degree of freedom, so as to achieve unsupported metal 3D printing.