Simulation, 3D Printing, and Casting: The Perfect Symbiosis for Large Aerospace Structures
Additive manufacturing, commonly known as 3D printing, is increasingly raising interest, especially in the aerospace industry where reducing mass and hence fuel consumption is a major goal. Additive manufacturing offers huge potential since it enables the creation of load-specific organic shapes. Weight reduction as a result of mass removal and integration of multiple parts and functions within a structure lead to time reduction and much more. However, as a relatively new method in aeronautics, additive manufacturing suffers from certification and qualification issues where a lot remains to be done. Manufacturing capabilities are still restrained by the size of 3D printing machines, which makes the technology unsuitable for larger components within a plane, such as an engine pylon or an access door. The dimension issue is an obvious hurdle for 3D printing. An airplane door is, while being rather large – due to its complexity and function integration – a very promising part when it comes to potential cost reduction via a one-shot production method.
In a study, engineers from Sogeclair aerospace explored solutions for this problem by creating a development process combining the two methods of additive manufacturing and casting - their advantage to developing and manufacturing this airplane door. While casting is a five-thousand-yearold, well-validated process, additive manufacturing provides design freedom not currently offered by any other manufacturing method. To leverage the full potential of these combined methods, design and optimization of the door were handled using Altair’s HyperWorks™ software suite.
Simulation at Sogeclair
Sogeclair has been using Altair solutions for many years and relies heavily on the Altair HyperWorks software suite for simulation and development tasks. About 20 people regularly work with Altair tools, some of them in the innovation department at Sogeclair, which was responsible for the airplane door development.
The engineers use various Altair HyperWorks tools and rely heavily on Altair OptiStruct, an FEA solver and optimization tool, as well as Altair HyperMesh and Altair HyperView, which are applied for pre- and post-processing. OptiStruct is very much appreciated as an FEA solver and optimization software as it offers a series of interesting features to set up the optimization for the convergence of a satisfying solution. In addition to that, SOGECLAIR aerospace designers are working with Altair Inspire, the generative design/ topology optimization and rapid simulation solution, because it is easy to use and very valuable especially in the first design phase. SOGECLAIR aerospace uses all of the Altair tools via Altair’s flexible unit-based licensing system.
Challenging the God of Winds – Making “One Shot” Possible with Simulation, 3D Printing and Casting
The example chosen in this study is an Ebay access door located at the nose fuselage which is used by operators for airplane inspection and maintenance. The Ebay access door turned out to be an interesting case study in many ways as the team faced some tricky engineering challenges: The door is too big to be feasible using DMLS (about 800 mm x 500 mm x 250 mm), it is made of AS7G06 aluminum which is not yet qualified in aeronautics using DMLS, and it possesses a very thin skin with very tight dimensional and geometrical tolerances.
Named EOLE after the Greek god of winds, the study describes the investment casting applied on an aircraft access door. The manufacturing process is based on investment casting from a 3D printed resin pattern. The EOLE study was led by SOGECLAIR aerospace and was done in collaboration with CTIF, Ventana, and voxeljet. voxeljet is a leading manufacturer of 3D printing systems for industrial applications that specializes in Powder-Binder-Jetting of plastic and sand.
The major technical problem addressed in this project was casting an aircraft access door (class 2F part) in “one shot” and nearly net shape integrating a thin skin with organic stiffeners. With the aim to demonstrate that this is possible, the engineers involved in this study followed a systematic roadmap ensuring that all project requirements are met. The optimization study lasted about two months, involving eight topology optimization runs and four mechanical stress checks to achieve a satisfying design.
Among the many challenges the engineers faced in this project, two were of utmost importance. For casting, the skin thickness had to be set at the minimum feasible wall thickness. This is important because the outer surface of the door, considered a part of the fuselage, has to fulfill very tight dimensional and geometrical tolerances. Another tricky point on the access door was the connection between the skin and the stiffeners. In order to handle this, SOGECLAIR aerospace sketched some ideas which were used for a CAD model and the subsequent process simulation.