Excerpt from the September 2020 Foundry Management & Technology Article by Robert Brooks.
CAD meets casting simulation, and then 3D printing, as a specialty manufacturer effectively converts another complex assembly to a more efficient, lightweight casting.
One or two technology cycles ago, metal casters were enthusiastically adopting simulation programs to identify the causes of quality defects during casting production. That wave of development, still in progress, was prompted by the emergence of CAD programs that optimized casting design. One trend line in the current metal casting technology cycle is adaptation of CAD files to guide additive manufacturing programs, as in 3D-printing of bonded sand into optimally designed molds and cores.
Now, all these trend lines are converging with still another initiative in metal casting — redesigning castings (or fabrications, or other assemblies) as lighter, more functionally effective cast structural elements of vehicles, machines, etc. In the example of one manufacturer, coordinating these trends also made it possible to expedite the design of a customized machine to maximize the potential of its market niche.
The manufacturer is Amazone H. Dreyer GmbH & Co. KG, a German supplier of agricultural machinery. Like any manufacturer, there is a constant cycle of reevaluation and redesign of its machinery and tools, like harrows — the ground-engaging tool that is dragged by tractors to till the soil in preparation for seeding. In these devices, the producers have a steady effort to make the harrows more stable, more durable, and lighter to comply with the regulated axle loads for road and highway transit.
Amazone, a family business, produces the Catros series of compact disc harrow with a bogey chassis. These devices are linked to a tractor and can be used in different configurations for shallow tilling as well as intensive soil cultivation at a working depth of up to 15 cm.
The bogey chassis connects the harrow device to the axle to enable the device to be transported from the farm to the field. Originally a welded structure weighing 245 kg and with a welding seam running 16.5 m long, it was a very complex and production-intensive design. To reduce manufacturing costs and make the structure lighter and more stable, Amazone decided to replace the bogey chassis. Using Altair's Inspire "topology optimization software," Amazone developers redesigned it as a casting, optimize the structural design for the operational needs of the component and for production efficiency.
Because the distribution of the material in the component can be optimized for the force (i.e., ground engagement) requirements, the cast bogey chassis is more than 45 kg lighter than the welded structure. At the same time, the new design is estimated to achieve 272% longer service life than the previous design because the new casting has more uniform rigidity than the weldment.
As for the casting design process, Altair engineers simulated metal flow to identify and reduce the risk of internal defects cause by gas pockets during mold filling. And on that point, Amazone's Sebastian Kluge noted: "The creation of the sand casting mold using 3D printing makes it possible to quickly source prototype components, and therefore significantly reduce development times."
In general, manufacturing sand molds for such a complex component is time-consuming. Altair opted to print the bonded sand into the complex shape using the voxeljet VX4000 3D printing system, with a build space of 4,000 x 2,000 x 1,000 mm.
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