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The NSX body designers were amazed at the amount of design freedom they could get from ablation casting as well as the mechanical properties. Ablation casting allows the shape freedom of sand casting while getting the material properties of a premium die casting.”—PHILIP VAIS

Vais, Principal Engineer-Materials Research for Honda R&D America. Honda was able to achieve the

necessary properties and additional design requirements with ablation casting by partnering with Alotech Limited, Cleveland. Ablation cast- ing is a new technology invented by Alotech that combines the complete flexibility of traditional sand casting techniques with rapid cooling of the molten alloy through the use of a water-soluble binder. Te lower front body, upper front body and rear body nodes, cur- rently cast at the Honda of America Anna Engine Plant in Ohio, show- cases Honda’s ability to take external technlogy and work collaboratively with Alotech to integrate ablation casting into existing manufacturing requirements (a real-world technology transfer). For this reason, Honda and Alotech have earned the 2015 AFS/ Metal Casting Design & Purchasing Casting of the Year Award for the Acura NSX space-frame nodes. The materials group at Honda

R&D America was aware of the ablation casting process for several years. It first heard about the process by word of mouth and a conference paper and was working with Alotech on developing the ablation process for potential use on future cars. “Te properties of ablation cast

parts would match the properties of the surrounding extrusion members of the space-frame structure, allowing them to be located in the crash zone,” Vais said.

As the NSX designers started their

second round of design work, they successfully increased the nodes’ size

to consolidate several surrounding stampings and extrusions from the first-round design. To be located within the crash

zone, the castings must meet several important requirements: 1. Te mechanical properties of the node castings must match the properties of the surrounding extrusions.

2. To crush in the proper mode, certain areas of the node castings must match the wall thickness of the extrusions (3-4mm). At the same time, the nodes must incorporate thick section bosses to rigidly mount to the front suspension arms.

3. Te nodes must be hollow in order to allow the extrusions to be slotted inside and welded and to optimize weight reduction.

4. Te nodes must keep a low dimensional tolerance to reduce problems within space-frame construction.

5. Te nodes must have minimal porosity in order to achieve good welding quality.

6. Te rear node casting must with- stand 210 kN without breakage. “No other process could provide the

combination of hollow shapes, small wall thickness, welding performance and material properties to meet the design requirements,” Vais said. “Te NSX body designers were amazed at the amount of design freedom they could get from ablation casting as well as the mechanical properties. Ablation casting allows the shape freedom of sand casting while getting the material properties of a premium die casting.” Te high solidification rates of the


ablation process enables the forma- tion of a fine microstructure (specifi- cally, the size of the eutectic silicon phase). In the crush-critical areas of the nodes, the castings achieve an American Foundry Society (AFS) modification level between 5 and 6, indicating the aluminum’s micro- structure has been fully modified for highest ductility and fracture strength. Te fineness of the silicon phase largely benefited the ductility of the casting. By consolidating additional

components with the redesigned nodes, Honda realized cost savings due to the reduction of tooling investment. Ad- ditionally, the application of a casting in the space frame eliminated the need for MIG (metal inert gas) weld length on each side of the vehicle, thereby minimizing thermal distortion of the space frame during construction. “Trough the ablation casting

process, Honda was able to achieve the mechanical property requirements for application in the crash zone, produce weldable and hollow node components with both thick and thin wall sections, and maintain an acceptable dimensional tolerance,” Vais said. “Tis new technol- ogy was a key element to achieving the final performance targets of the new NSX supercar body structure.” With the January launch of the

production version of the NSX, the nodes are one of the first public real- world applications of ablation casting and a solid example of the cutting-edge advantages ablation gives designers to make lightweight structural parts. “The original Acura NSX debuted in America 25 years ago. NSX stood for ‘New Sports Ex- perimental.’ But when it proved to be no experiment, the name stuck. And NSX redefined what it meant to be a supercar,” said Mike Ac- cavitti, Senior Vice President and General Manager, Acura Division, at the North American International Auto Show in January. “Supercar performance, delivered in a unique and challenging way, powered by new technologies and utilizing new materials, that is the heritage of NSX.” ■

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