With articulated robots and advanced software applications that can simulate every stage of production, one company’s robotic solutions help a luxury automotive maker construct their signature models. Contributed by Comau.
Internationally known for its famous Trident, the Maserati brand is located in Bologna, Italy. Today, it operates in more than 40 countries around the world and continues to play a key role in the history and culture of sports cars. The brand has made its presence as a high end car model around the globe and the processes that have been involved in its construction is an intricate one – something that requires a high amount of precision to achieve.
Within The Production Line
Maserati’s old Bertone plant in Grugliasco (Italy), which has been re-named the Avvocato Giovanni Agnelli Plant, is the place where two of its most popular models, the Quattroporte and the Ghibli, are manufactured. Here, the production process starts at the sheet metal department and the bodyshop assembly lines.
“The Grugliasco plant has a production capacity of 50,000 vehicles per year,” explains the plant manager Alberto Filippini. “We currently make 150 vehicles a day over two working periods. The cycle time of the sheet metal working phase is of around 316 seconds. This means that the line can build nine bodies per hour,” he continued.
The main feature of the line is its flexibility, as Renzo Novara, who is responsible for the sheet metal working department, explains, “Depending on the production needs, it is possible to program the line to automatically determine whether the piece is for the Quattroporte or Ghibli.” According to him, this is important because the bodies of the two models differ substantially in terms of the length of the chassis and the related components. There is a need for a great amount of flexibility of the line – this means that it is able to produce one of the two models, or both, in a continuous flow, according to the requests.
To better understand why this level of flexibility is strategic for a high end automotive company, it is necessary to examine the line configuration in more detail. The first section of the sheet metal working line is where the high-strength steel and die-cast aluminum components, all of which have been fully tested and controlled, are received and hand assembled to build the so-called body.
This element consists of the front framework (upon which the engine and all the related mechanical components are mounted), the central floor (the first row of seats, tunnel, etc.) and the back framework (the second row of seats and trunk).
After the frame is finished, it moves to the second section where the process is fully automated by 86 robots (82 of which are made by Comau). These robots perform a wide range of operations including, welding, part handling, riveting, Tucker stud installation, roller hemming (the process of folding the flanges of the metal sheets), and more. The strength of the line, according to Mr Novara, is largely due to robots such as the ones by Comau which can perform the complex operations of bodyshop line with extreme precision.
Once the automatic cycle is started, each chassis is processed in sequence by the various industrial robots. These robots perform spot welding on one hand while inserting subcomponents (brake hoses, underbody parts, wiring, etc.) as well as the closing elements such as side and top clamp brackets, rivets and Tucker studs.
Once completed, the chassis goes into to the section where the body is added. This operation is performed in ‘double layer’, or better, in ‘parallel’. In a first station, the skeleton, which is the internal part of the side, is fastened, while in the subsequent phase, the so-called ‘outer skin’ is added. This cutting-edge technology improves accessibility and facilitates the operations performed by the robots in the welding stages and in the positioning of the references and clamping elements. In addition, the technology minimises the number of slots, which makes the vehicle quieter and more stable.
The Comau robots have a double function in this section. They weld, and by changing the robot head, they also perform the other activities that are needed to complete the assembly according to predetermined sequences. Such activities include handling and positioning of the different pieces, spreading the semi-structural adhesive on the chassis, and more.
Mr Novara explains the process in more detail. “In the ‘double layer’ stations, where the body is composed, the line can handle both the long chassis of the Quattroporte and the shorter Ghibli chassis. In other words, it is here that the line proves its flexibility, given that it is able to produce both car models according to the requests, in a continuous flow and without interruptions. After the assembly of the outer skin for the sides, each piece continues to the sheet metal working phase for the measurement and verification operations.”
In summary, the whole process involves the assembly of parts and subgroups through the insertion of 4,785 welding spots for each model. Of these, 1,083 are performed in advance and 3,702 are made during the sheet metal working phase (1,025 of which are done by hand and 2,677 are performed automatically). On the line, 190 rivets and 243 arc-welded studs are also applied for each model. Finally, almost 79 metres of semi-structural adhesive are spread, 66 metres of which by means of the robot and 13 meters manually. After the sheet metal working phase, each body is sent to the painting and final assembly sections. “Before being put on the market,” Filippini adds, “every vehicle is carefully controlled and verified using simulation based on specific test benchmarks, and with a complete road test that covers a distance of 40km.”
The Robotic Factor
In the Grugliasco plant, Maserati applied 82 Comau robots of various types, including articulated and multi-axis, specifically designed to ensure a reduced footprint, a larger working area, and high-precision movement and positioning, while covering all payload categories and applications.
More specifically, the robots are available in different ‘wrist’ versions: the ‘standard wrist’ version with external dressing, and the ‘hollow wrist’ version, in which the welding equipment is housed inside the forearm. Hollow wrist robots feature a reduced footprint, as the various cables for the welding guns, air flow, and other the cables run inside the robot arm to reach the head. This is why the robot is called ‘hollow wrist’.
Before the lines were set up, Comau and Maserati collaborated to develop specific software applications to provide accurate, detailed offline simulation of each stage in the production line. Thanks to that, Maserati was able to verify the entire sheet metal working process in a virtual way, before it was actually implemented. This enabled the company to anticipate and correct mistakes and significantly reduce operating times and costs.
Mr Novara said, “The Comau robots are technologically advanced, high-performing, and easy to maintain. They are also reliable, flexible and specifically tailored to suit all our applications.” He went on to mention that these robots can be employed in low and medium frequency lines, such as in the Grugliasco plant where body is produced in slightly more than 5 minutes, as easily as in high-frequency lines, such as the plants in Melfi, Cassino and Pernambuco, in Brazil, where the cycle time of each body is around 50 seconds.