Like the original Acura NSX, which was the world’s first all-aluminum exotic car, the 2017 NSX has a cutting-edge structure. Its multi-material space frame and body panels utilize new materials and construction methods. They deliver next-generation structural rigidity, outstanding outward visibility, world-class collision performance and superior surface and paint quality, befitting a next-generation Acura supercar.
The aluminum-intensive space frame and multi-material body panels also minimize weight with superior packaging flexibility for the NSX Sport Hybrid SH-AWD power unit. The high level of dynamic rigidity reduces noise, vibration and harshness (NVH) and ensures that driver inputs are directly translated to the car’s actions with incredible speed and fidelity.
Some key features of the NSX multi-material space frame and body are:
- Unmatched dynamic torsional rigidity – The NSX directly responds to the driver’s cornering demands, instantly transmitting those inputs to the chassis while maintaining perfect connection between front and rear axles, communicating both the driver’s action and any changes in the road surface with the utmost fidelity.
- Ultra-high local chassis rigidity – Each chassis component is mounted to a rigid casting supported by extruded aluminum frame members that act like “truss structures” such that high local attachment-area stiffness is ensured in all directions, helping maintain the precisely-designed chassis geometry at all times.
- World’s first automotive application of ablation casting technology – Used both at front and rear, these ablation cast aluminum frame nodes serve as ultra-rigid mounting points for the suspension. Applied in key crush zones, these nodes link frame sections together and uniquely deform in a manner similar to a forged component but with lower weight, enabling shorter front and rear overhang, reduced vehicle mass and world-class collision performance.
- A-pillars: Super strong, yet slender – In another world’s first, a new three-dimensional bent and quenched (3DQ) frame member was employed to create thin yet sturdy A-pillars. The resulting ultra-high-strength material allows a slender cross section to maximize forward visibility while meeting structural demands, including roof-crush requirements.
Multi-Material Space Frame
The NSX space frame construction consists of highly-rigid aluminum extrusions, aluminum, high-strength steel stampings and ablation cast aluminum frame nodes, which serve as critical components in the absorption and dispersion of energy in both front and rear impacts.
Highly rigid and reinforced extruded aluminum beams comprise the majority of the space frame. They are utilized for the front and rear frame rails and cross members, front and rear bulkhead frame members, floor cross members and side rails. To further attenuate noise, 38 aluminum extrusions are filled with acoustic spray foam and used in different locations.
Aluminum stampings are utilized as lightweight closure panels for the rear floor, rear bulkhead (firewall) and B-pillars.
Space Frame Development
To unlock the full potential of the all-new Acura NSX Sport Hybrid SH-AWD power unit and its total dynamic performance, the engineering team took a bold and challenging new direction: a completely clean-sheet, multi-material approach that breaks new ground in the automotive realm. By starting from scratch, the NSX development team was able to choose the optimal material and construction technology for each area of the space frame. This process targets both low mass and ultimate rigidity, while also satisfying other critical design objectives.
“The challenge for the body design team was to create a body with a high level of rigidity to be able to transmit the full feeling of this unique power unit directly to the driver without delay,” said Acura NSX Space Frame and Body Design Project Leader Shawn Tarr. “While the all aluminum unibody of the original NSX was ahead of its time, we would need to look to world-first technology in order to achieve this new level of rigidity.”
Space Frame Construction
A number of advanced technologies and techniques are used in the construction of the NSX space frame, which is built entirely in-house at the company’s new Performance Manufacturing Center in Marysville, Ohio. The NSX development and manufacturing teams were determined to maintain in-house control of the complete construction process to ensure the highest levels of quality and performance for Acura customers.
Through strict manufacturing build processes and quality controls, the precise dimensional accuracy of the multi-material body is maintained throughout the construction process. This eliminates the need for post-process machining. This unique manufacturing system is a great point of pride for Acura, allowing the team to achieve quality and accuracy levels superior to its competitors.
Robotic Metal Inert Gas Welding
Metal inert gas (MIG) welding is utilized for the majority of the aluminum space frame construction. The NSX space frame contains more than 860 MIG weld points, where more than 112 ft (34 m) of MIG wire is applied. Most welding is done by fully automated robotic weld arms, which offer exceptional precision and control for superior quality. All welds and body components undergo a detailed inspection by highly skilled Performance Manufacturing Center (PMC) weld technicians.
Underbody section of the space frame are fabricated in a series of four stations, where highly skilled weld technicians work in tandem with automated robotic weld machines to ensure the highest quality parts. Specialized picture frame-style fixtures, developed in-house, hold the component pieces, allowing for more precise control of the weld process and dimensional accuracy of the part. Four of these fixtures are able to rotate 360° to improve the access of robotic weld arms to the part and to allow for full datum referencing (highly accurate measurements between lines on a three-dimensional X, Y and Z axis) of the part.
Strategic sequencing of the numerous weld processes reduces the potential for parts deformation from heat buildup, a common challenge in the welding of aluminum components. The quality of welds and dimensional accuracy of the part are confirmed at each station by technicians through visual inspection.
The floor and upper components of the space frame are then joined by large, fully robotic general welders, which also utilize rotating trunnion-type fixtures with 360° movement. Twin robotic weld arms are able to conduct welding processes simultaneously to aid in both manufacturing efficiency and in the uniform distribution of heat.
Aluminum Cast Nodes
Aluminum cast nodes serve as joining points for the extruded aluminum frame members and as ultra-rigid mounting points for the vehicle’s front and rear suspension systems and its rear Sport Hybrid SH-AWD power unit. These nodes are either gravity die cast or, in front and rear crush zones, formed using advanced new ablation casting technology.
Ablation Cast Nodes
A most difficult design challenge in the development of the new NSX was to minimize the front and rear overhangs of the vehicle while managing collision energy absorption in key areas for crash performance and maintaining optimal structural rigidity. Acura engineers developed an innovative new technology called ablation casting to solve these complex and competing design imperatives. This process is an all-new material application and a world’s-first application in the automobile industry. Ablation casting was matured from a fundamental research theme to a production vehicle application within the development cycle of the new NSX—a major design, engineering and manufacturing achievement.
The ultra-rigid space frame uses aluminum castings (shown in yellow) for all suspension mounting points
Ablation casting combines traditional casting methods with rapid cooling techniques to offer the design flexibility and rigidity of casting with the ductility and energy absorption characteristics of extruded material. Traditional castings provide the ultimate rigidity in space frame and other body designs, but experience a major drawback in that they are brittle and not suitable for the crush zones of this no-compromise supercar. Their ductility and energy absorption characteristics make the ultra-rigid ablation castings ideal for the crush zones.
Ablation casting involves the rapid cooling of a sand-cast aluminum component via the precise application of water jets that ablate the sand mold while cooling the part. This process fine tunes both the cast part’s shape and its material properties while minimizing weight with hollow forms and optimized wall thicknesses. The technology was developed with Alotech and is performed in-house at Acura’s Anna, Ohio, engine plant.
Ablation cast aluminum nodes within the NSX space frame shown in yellow
Ablation casting is utilized in the creation of six joining members, or nodes, of the NSX space frame: two upper and two lower nodes in the front frame and two nodes in the rear frame. These ablation cast nodes also serve as ultra-rigid mounting points for both the front and rear suspensions. The front nodes are designed to absorb and dissipate energy in a frontal collision by progressively crushing at 155 kN of load. The two large ablation cast nodes located at the rear of the space frame are designed for high strength, able to withstand 210kN of load without breaking to help mitigate forward movement of the power unit in the event of a rear collision.
Advanced Joining Technology
Acura uses advanced joining technologies throughout the construction of the multi-material space frame to ensure water-tight joints, reduce weight and part complexity and create strong and tight joints with clean and finished edges:
- Self-piercing rivets (SPR) allow for the joining of two or more layers of material without having to pre-drill or punch a hole while providing an exceptionally watertight joint. The NSX space frame contains more than 345 SPRs.
- Flow-drill screws (FDS) are used in the place of nuts and bolts in numerous areas of the space frame, reducing both weight and parts complexity. FDS are particularly well suited for use where one side of the part is inaccessible by conventional tools, such as in an extruded component. More than 245 FDS are applied to the NSX space frame.
- Roller Hemming joins two pieces of sheet metal by creating a sharp-angle bend, allowing the metal to be folded back over itself, creating a strong and tight joint with a clean and finished edge. There are nearly 60 ft (18 m) of roller hemming edge on the NSX space frame closure panels.
Space Frame Advanced Conversion Coating
Prior to final assembly, the fully-constructed space frame undergoes an advanced conversion coating process using a zirconium pre-treatment material and an e-coat process as an additional barrier to galvanic corrosion while maintaining a low environmental impact.
The use of zirconium, an Acura first, eliminates more than 90 percent of the heavy metal waste byproduct that results from the use of more conventional zinc-phosphate material. The use of a zirconium conversion coating is part of the effort to create a manufacturing process with a low environmental impact, consistent with the ideal of a next-generation hybrid supercar.
Repair and Serviceability
To assist in the ease and cost of collision repair, as well as to protect the precise dimensional accuracy and functional integrity of the NSX space frame during a collision repair, the NSX development team worked closely with the Acura service engineering team to implement a modular construction concept: Space frame components can be purchased and replaced individually or as pre-assembled modular sections. For example, there are “light-collision” and “medium-collision” replacement sections for both the front and rear of the vehicle, which minimize the amount of welding required during repair.
For extensive servicing of the rear power unit (V6 engine, Direct Drive Motor, 9DCT and transaxle), the team designed a modular rear section. The entire trunk section can be removed as a single unit to permit easy access to the mid-mounted V6 engine.
3D Bent and Quenched Ultra-High Strength A-Pillars
The original NSX was known for its outstanding forward visibility, giving drivers a feeling of being connected to the road while expanding their view. This design attribute was maintained as a core characteristic of the NSX driving experience.
In another world’s first, the upper portion of the A-pillars and roof rails, which comprise one continuous section, are formed using three-dimensionally bent and quenched (3DQ) ultra-high-strength steel tubing.
This new forming process allows for highly accurate forming of complex steel tube shapes with ultra-high tensile strength, allowing for extremely small pillar cross sections that give the NSX superior forward visibility while also providing high roof-crush strength.
The 3DQ component is heated and then shaped in three dimensions by an articulating robotic arm, after which the part is quenched using water jets to achieve an ultra-high tensile strength of 1,500 megapascals (MPa). This process enables the pillar to have a very thin cross-section with precise shape specification and tolerances, while meeting the increased structural rigidity standards for roof-crush performance. It also reduces the width of the A-pillar structure to just 1.65 x 1.42 in. (42 x 36 mm) and the finished A-pillar by 1 in. (25 mm), compared to a conventional construction process. The view is a full 36 percent less obstructed than the next-best supercar evaluated by the Acura team, and even better than the original NSX.
To prevent galvanic corrosion, the 3DQ component receives an electro-deposited coating before being joined to the NSX multi-material space frame.
Multi-Material Body Panels
As with the multi-material space frame, many different lightweight materials were used for the exterior body of the NSX. Each material’s unique characteristics create exterior body panels of the highest finish quality. They were chosen for their abilities to minimize vehicle mass, optimize weight distribution and center of gravity and help ensure longevity and durability. These materials also contribute to panel rigidity, pedestrian safety, styling detail and exceptional surface finish. The NSX multi-material body design concept extends throughout the entire body construction.
- Sheet molding compound (SMC) is used for the fenders and trunk
- Sheet hydroformed aluminum is used for the outer door panels
- Aluminum stampings are used for the hood and roof (a carbon fiber roof is optional)
- High-temperature-resistant plastic is used near high-heat areas
Sheet Molding Compound Panels
Used extensively in the construction of high-end exotic cars in key exterior componentry, sheet molding compound (SMC) is high-grade specialty glass-fiber reinforced polyester, its shape formed while heated under pressure within a compression molding. By utilizing special resins as well as high-strength fiber composite matting, NSX exterior design engineers have developed SMC material for specific applications on the vehicle’s exterior.
Specially engineered SMC material, for light weight and durability with high surface quality, has been created for use in the fender sections at all four corners. Designed to possess high structural rigidity, this unique SMC paneling optimizes the NSX overall center of gravity by minimizing weight at all four corners. The rear trunk skin is also made of lightweight SMC, with structural support provided by a stamped aluminum inner frame structure.
A rigid, structural SMC material has been developed for use for the NSX trunk internal structure. This highly rigid construction allows the trunk structure to serve as a mounting point for the rear fenders and rear bumper for optimal accuracy and precise fit. An added benefit of the trunk compartment design is that it allows for easy removal when the vehicle is brought into an Acura dealer for service. After removing the rear fascia, the entire trunk structure can be removed for easy access to the engine room. This design also allows for easy replacement of the rear section should the NSX be involved in a rear-end collision.
Sheet Hydroformed Aluminum Panels
The door skins and inner panels are made of sheet hydroformed aluminum. Hydroforming is the ideal means to shape the one-piece aluminum panels that make up each door. The process supports the construction of complex shapes that cannot be formed by conventional stamping techniques. Moreover, the aluminum door skins can be relatively thin and light as they are naturally supported by the inner door structure.
Aluminum Stampings
The hood, roof panel and the engine compartment and trunk frame are composed of high-grade stamped aluminum. Like the other composite materials utilized in the exterior, the use of aluminum in these areas offers reduced weight with excellent structural rigidity.
High-Temperature-Resistant Plastic
A special, high temperature-resistant plastic is used in the small body panel sections just below the floating C-pillars (forward of the rear fenders) due to the body panels’ close proximity to the turbo intercoolers.
Carbon Fiber Floor
Carbon fiber serves as the ideal material for the driver and passenger floor section. In addition to its light weight, this material is strong enough to handle the loads occupants place on the floor while entering and exiting the vehicle. Aluminum sheeting would require additional cross-member frame support underneath, which would have added weight.
Body Panel Fitment
As the near-final step in the vehicle assembly process at the Performance Manufacturing Center, the exterior body panels are attached to the vehicle’s space frame, starting with the roof, then the doors and other components, working from the top down. This process, along with the high degree of dimensional accuracy for the underlying space frame, allows for extremely fine adjustment of panels to achieve consistent and symmetrical panel gaps.
Specifications