A research team is developing what the partners claim will be the world’s largest binder-jet printer for sand molds, aiming to streamline production of castings for the nacelles of offshore wind turbines. Those molds may weigh over 60 metric tons and measure up to 9.5 meters in diameter, according to GE Renewable Energy, voxeljet AG, and the Fraunhofer Institute for Casting, Composite and Processing Technology.
The development program is already underway, and printer trials will start in 1Q 2022.
GE’s involvement supports its Haliade-X series of wind turbines, described as the most powerful offshore turbine now available, rated for a generating capacity of 14-, 13-, or 12 MW. As the turbines are designed with a 220-meter rotor and three 107-meter blades, the Haliade-X nacelle – or housing unit that sits atop the tower – is designed for structural and mechanical reliability, as well as environmental durability in offshore installations.
GE Renewable Energy forecasts rising demand for its offshore turbine product line, with offshore generating capacity projected to increase 15X by 2040, becoming a $1 trillion market.
“The 3D-printed molds will bring many benefits including improved casting quality through improved surface finish, part accuracy, and consistency,“ explained GE’s Juan Pablo Cilia, a senior additive design engineer. “Furthermore, sand binder-jet molds or additive molds provide cost savings by reducing machining time and other material costs due to optimized design. This unprecedented production technology will be a game changer for production efficiency allowing localized manufacturing in high cost countries, a key benefit for our customers looking to maximize the local economic development benefits of offshore wind.”
The additive manufacturing (3D printing) technology will be provided by voxeljet AG, a principle developer of binder-jet processes using molding sand: A sand binder is deposited by a printing head onto a bed of sand, building a mold in horizontal layers according to a pattern set by a CAD model of the finished product.
The project will develop the Advance Casting Cell 3D printer, with financial support from Germany‘s Federal Ministry for Economic Affairs and Energy, cutting production time for the sand pattern and mold from 10 weeks to two weeks – with further benefits in carbon-emissions reduction due to the shorter production sequence and the possibility of on-site production that will reduce transport requirements.
“The test mold we printed for GE in 2019 consisted of dozens of individual parts,” voxeljet’s Christian Traeger reported. “With the ACC, we aim to print a significantly reduced number of parts for the full set. Added to that, the mold can be optimized in terms of functionality and material consumption. This optimization makes completely new casting designs possible that can further enhance the efficiency of the turbines.”
Fraunhofer IGCV is an industrial research institute dedicated to material science and manufacturing processes, as well as factory and enterprise networks. “We are taking a close look at thermal management during casting, and we will evaluate the ideal proportions of the printing materials,” explained Dr. Daniel Günther, of Fraunhofer IGCV. “Also, we will develop and test new approaches to process monitoring as part of the project.”
His Fraunhofer colleague Dr. Wolfram Volk added that the development will significantly improve the environmental footprint of processes involved in producing large-scale wind-turbine parts “We aim to optimize the mold printing to avoid extremely costly misprints or even miscasts, to save on binder and activator, and to improve mechanical and thermal behavior during casting.
Volk continued: “By developing a process that conserves resources as much as possible, we want to help to improve the environmental and cost balance in the manufacturing of wind turbines.”