NASCAR drivers work under extreme conditions – making split-second decisions while traveling at speeds nearing 200 mph and precariously looking to move ahead when the next car is mere feet away. The safety, integrity and performance of the car are crucial to the driver and his team. These factors were also front and center with NASCAR when in January 2006 it announced the launch of a universal car design tagged the ‘‘Car of Tomorrow’‘ (COT) for its Sprint Cup Series.
Sparked in large part by Dale Earnhardt Sr.’s fatal, final-lap crash at the 2001 Daytona 500, NASCAR set out to create a universal design that would improve safety features, provide for more cost-effective maintenance and level the playing field between fiercely competitive teams. The COT design standardizes a number of components, ranging from sections of the frame to crumple zones, across all manufacturers and race teams.
With NASCAR’s rules in hand, Dodge Motorsports initated a COT chassis manufacturing program. The four, factory-supported Dodge race teams use Dodge Motorsports provided chassis as a basis to build their individual race cars.
Similar to every passenger car manufactured, race cars incorporate thousands of welds. Dodge teams were spending many hours manually MIG welding the frame, middle section and front and rear clips that make up each car frame kit. Wanting to reduce man hours, as well as increase weld consistencies for the teams, Chrysler investigated robotic welding options and decided on a Lincoln Electric/Fanuc robotic welding cell.
The result: Chrysler realized a 75-percent decrease in chassis assembly time when compared to hand welding the chassis. The Lincoln Electric/Fanuc robotic welding cell offered other benefits as well, a more consistent chassis for the teams and the cost savings associated with the reduced man hours to weld the chassis by hand.
In the Not-So Old Days
Before installing the Lincoln Electric/Fanuc robotic welding cell, the COT center and rear sections of the frame were constructed by the teams using manual welding and assembly techniques.
‘‘This was extremely time consuming and very inefficient,’‘ says Tom O’Dell, Specialty Vehicle Engineer – Dodge Motorsports Engineering. ‘‘Manual welding also caused variations in the process, making each COT center and rear section slightly different than the one before.’‘
O’Dell explains that the consistency of the weld, including torch angles and travel speeds, was difficult to keep consistent during manual welding, especially if different people welded different sections of the chassis. This translated into variations in weld quality, which could result in lower strength welds. Too often, an inconsistent weld pattern resulted in distortion on the center and rear sections that were unpredictable and resulted in a dimensionally unstable assembly.
The Robot Takes The Driver Seat
The Lincoln Electric/Fanuc system consists of a six-axis robotic arm and controller, powered by a Lincoln Electric Power Wave® 455M. The system includes several subassembly fixtures and one final assembly fixture.
‘‘We saw the benefits of the robotic cell immediately,’‘ O’Dell explains. ‘‘The new process gave us a competitive advantage in the repeatability, weld quality, cost, accuracy and part consistency at the end of assembly. This is why we chose the Lincoln Electric/Fanuc robotic weld cell.’‘
It now takes the robotic cell just 39 minutes to weld the frame. Even when you add in the fixture change out and final assembly, it takes less than two hours to complete the center and rear sections.
When compared to the manual welding, Dodge Motorsports decreased the assembly and weld time by approximately 75 percent.
The car frames have to perform under extreme speeds and conditions, making quality and weld integrity crucial. With the robotic weld cell, welds are made in the same sequence and position every time, resulting in better consistency, travel speeds, torch angles, depth of penetration, bead size, heat input and bead shape. This allows for greater predictability in cage stiffness, bending and twisting standpoint for the cage, eliminates variation and increases weld accuracy.
The fixtures control the geometry of the subassemblies and final assembly, further controlling the accuracy of the overall piece.
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