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Robots Frame New Car with Automotive Lightweighting

Jim Lorincz
By Jim Lorincz Contributing Editor, SME Media

The all-new Alfa Romeo Giulia is sporty, a true testament to the historic racing heritage of the automaker. When a new production line with articulating robots and flexible framing stations was needed, Alfa Romeo called on Comau SpA (Torino, Italy; Royal Oak, MI) to co-engineer a flexible body-in-white (BIW) line to handle advanced lightweight materials used in the Giulia’s framing. The “double-layer” framing process had to ensure that the line would be scalable to add future models and innovative enough to meet an aggressive 35-week “purchase to product roll-out” timeframe. The model range included three trim levels (Giulia, Giulia Super, Giulia Veloce), each with distinct features and performance specifications. These versions, together with the Giulia Quadrifoglio, the most powerful road-legal Alfa Romeo ever made, would share the same lightweight architecture and would be built on the same assembly line. In addition, the line would be installed within the existing Cassino, Italy plant and had to ensure the flexibility to accommodate future product alternatives.

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Alfa Romeo’s Giulia was awarded top prize for Best Body Design at the 18th edition of the EuroCarBody competition.

To address these issues, Alfa Romeo asked Comau to spearhead the manufacturing strategy and become an integral part of a cooperative co-engineering and design team. Its first task was to define the project requirements in terms of production, engineering, and process manufacturing. During the joint engineering phase, the team shared technology specifics, agreed on the manufacturing approach, and ensured that the technology backbone could handle Alfa Romeo’s high-volume applications. Comau developed a complete solution based on the modular, flexible, and expandable OpenGate framing system. The compact and lean architecture features up to 18 overhead-mounted robots and up to six dedicated model gates.

The high-speed and high-density operations facilitated automated assembly of the Giulia while meeting Alfa Romeo’s production targets and ROI for the four different models. The setup also used parts of Comau’s modular ComauFlex system, including the VersaRoll closed loop assembly and joining system. VersaRoll is primarily used for setting the geometry of the body sides and the chassis, assuring fast transfer of material through the line, reducing non-value-added time. In addition, both the OpenGate and VersaRoll systems utilize overhead-mounted robots, allowing the highest possible density of robots and increasing the volume of joining operations within each station.

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The Giulia Quadrifoglio model is fitted with a carbon-fiber roof, which is assembled in a 100% automated workstation. The aluminum roofs of other models are fastened via laser brazing.

Two of the elements that significantly contributed to the success of the project were the use of virtual simulation techniques and, of course, Comau’s manufacturing system. Working closely with the Alfa Romeo team, Comau developed virtual test cells in order to evaluate the behavior of the materials and joining processes that would be used within a large-scale production environment. The team also performed physical testing to verify specific elements, such as the bond quality of different joining techniques like riveting, studs, and welding. Finally, the joint engineering team ran numerous tests to establish which parameters were needed to optimize the manufacturing process, validate the geometry of the different assemblies, and ensure the highest level of performance and vehicle quality.

The use of virtual cells also provided the team with an accurate, detailed simulation of the entire production line. Verifying the different processes in a virtual way allowed the companies to identify potential issues and improve the anticipated results. In addition, virtual simulation was used to establish the estimated cycle times that Alfa Romeo could expect to achieve with the new line. These details were especially important given the need to accurately coordinate the movement and timing of numerous robots and their dressings with the multiple operations being performed.

The final configuration of the assembly line looked like this: The first section of the line is where the chassis is built, which consists of the front framework (where the engine and all the related mechanical components are mounted); the central floor (including the first row of seats); and the back framework (the second row of seats). Once the automatic cycle is started, each chassis is processed in sequence by various industrial robots. Once completed, the chassis goes into the section, where the body is added.

Next, two OpenGate framing stations work sequentially in a unique configuration that allows Alfa Romeo to perform the delicate operation in a “double-layer” construction process. Construction of the body is essentially broken down and assembled in two specific steps. In the first station, the structural or internal part of the chassis and its sides are built; in the subsequent phase, the so-called outer skin is added. This advanced process greatly improves accessibility, helping facilitate the work of the robots as they weld and position the various elements, and perform other activities needed to complete the assembly. Because the robots have complete, unobstructed access to the structural skeleton of the vehicle, welding operations are more effective and more precise than in a traditional process, which leads to better overall manufacturing geometry. At the same time, in a separate station, the external part of the vehicle is prepared, positioned and fastened to the structural skeleton.

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Comau's OpenGate framing system features up to 18 overhead-mounted robots and up to 6 dedicated model gates for high-speed and high-density automated operations. Robots have complete, unobstructed access to the structural skeleton of the vehicle.

The extensive use of lightweight materials such as aluminum, which is inherently more delicate than its traditional steel-based counterparts, requires great precision and accuracy during the joining and finishing processes. Because the Giulia Quadrifoglio model is fitted with a carbon-fiber roof and hood, the process complexity is further increased. Unlike the other Giulia models, where the aluminum roof is fastened via laser brazing, the carbon-fiber roof of the Giulia Quadrifoglio is prepared and assembled within a 100% automated workstation. The patent-pending process consists of multiple robots that are aided by advanced vision and control systems. The entire process is controlled for quality and precision—from the automatic cleaning of the components to the mixing, distributing, and spreading of the bicomponent glue—all the way to its polymerization with an innovative infrared system.

Another innovative aspect of the manufacturing strategy is the use of advanced technologies such as the RHEvo roller hemming system, which combines performance and efficiency with real-time data collection and process monitoring. With speeds of up to 750 mm/s, RHEvo can hem complex elements across multiple manufacturing lines while protecting the geometric uniformity of the assembled parts, reducing time-to-market and lowering overall production costs. For the Giulia models, RHEvo is used to hem the rear wheel arch, helping safeguard the rigid torque that the high-performance sports sedan requires. Here too, advanced vision systems are used to identify and correct any positioning variables introduced when the chassis is placed within the station.

The vision system not only calculates the exact position of the wheel arch, it also sends the data to the robot in order to correctly position the anvil in respect to the wheel arch. Working together, the robot can then recalibrate its position such that it is perfectly centered in respect to the wheel arch. RHEvo, working in a pull mode, then automatically hems the wheel arch, creating a perfectly precise drop hem in three passages using two types of rollers. Once the hemming process is complete, the system automatically reconfigures itself for the next model. The advanced system is flexible enough to manage up to four different models without the need for additional setup or operator intervention.

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