PATROCINADO POR
VII JORNADA DE ESTAMPACIÓN 7TH STAMPING CONFERENCE
Como visión de futuro, Carlos Borruel apuntó que “los requerimientos para la fabricación de vehículos van a ser más exigentes, lo que va a implicar mayor cantidad de piezas con este tipo de aceros. Por tanto, se va a incrementar el número de instalaciones de estampación en caliente. Por otro lado, queda camino por recorrer en el campo de la simulación, en el que estamos trabajando con las empresas AutoForm y Rovalma; se va a seguir avanzando en nuevos materiales de herramientas y recubrimientos y, por último, hay mucho campo de mejora en la aplicación de corte por laser. Se debe minimizar al máximo el corte por láser de las diferentes piezas, pues una línea de última generación de estampación en caliente puede llegar a necesitar hasta cinco cabinas láser asociadas, y esto es una inversión considerable. En este punto, consideramos que hay un amplio margen de mejora”.
HOT STAMPING AT SEAT In his presentation, Carlos Borruel described several SEAT models released between 2004 and 2012. He opened by stating, “In 2004, we launched the Altea, the last SEAT vehicle not to include a single hot-stamped part. One year later, the León included two — which accounted for 4% of the body’s total weight — which was the B-pillar. ” Mr Borruel underlined that between the Altea in 2004 and the León a year later, the brand managed to cut vehicle weight by 3.9 kg by replacing the two-part (one internal and the other external) B-pillar with a single component. “This also allowed us to eliminate a set of dies and a welding cell. The new Ibiza unveiled in 2008 also included two hot-stamped parts. The big leap forward came in 2012 with the new León, which is fitted with 17 hot-stamped parts, equivalent to 33%. With the León in 2012, not only were the A- and B-pillars hot-stamped on our own internal lines, but we also started using the technology on a much wider range of components, including the crosspieces, sills and tunnel.” To adapt to these changes, between 2005 and 2012 SEAT progressively modified its facilities and started using complete dies. Mr Borruel emphasised, “the complexity involved in adapting the lines and, in the case of the new León, in adapting them to work with multi-sector dies.” Today, SEAT’s facilities in Barcelona include three hot-stamping systems. These are supported by four laser-cutting booths to give the parts the final desired geometry. The SEAT engineer described the equipment as “small, making one part per stroke. We have reduced the cycle time in our lines, in order to increase their productivity. Therefore, the facility’s lay-out has been optimized, the robot claws have become lighter and more agile and more robots have been added. We have also improved cell programming.” To begin with, the die’s closing cycle took 24 seconds; today it takes just 8.” Referring to die change-over times, he said, “We are the benchmark in Volkswagen Group, as we take around four minutes on all of the equipment. Finally, maintenance times have been cut from 13 hours to 8 thanks to improvements to the cooling circuits and, above all, thanks to the new tool steels and coats.”
Forma 0 Gemma Prada then described the impact of the Forma 0 project to research new materials and processes used in high-strengthsteel forming. Rated as one of the best CENIT research projects supported by the Ministry of Industry, it brought together a consortium of companies, research centres and universities, all led by SEAT. “The project addressed 11 lines of research, one of which was on hot-stamping. Participants carried out studies into boron steel, forming and thermal-cycle simulations, die design, cold high-strength-steel cutting operations, and spotwelding cycles. Among the more specific analyses, it is worth highlighting the research into cooling processes.” Ms Prada underlined that the project, “Helped us to gain a much better understanding of the hot-stamping process. That knowledge has been applied in tangible form in our facilities and in the models we have launched. It has been put to use in tool materials and in the types of steel selected for the parts.” Carlos Borruel then took the microphone again to describe several of the issues resolved since the technique’s first application in 2005. “In that year,” he said, “some of the parts we produced did not meet the quality standards required. This was because we had not got the cooling right and were not drawing enough heat out. As a result, we had to do new dies.” The SEAT engineer stated, “We also encountered the common problem of die wear. We overcame this by improving preventive maintenance and meticulously monitoring the areas in which SEAT BARCELONA greatest wear was produced.” INCLUDE THREE Moving forward to 2012, Mr BorHOT-STAMPING ruel then referred to problems with SYSTEMS. THESE leaks and small fissures in some die sectors, which meant that the geomARE SUPPORTED etries established in the die designs BY FOUR LASERdid not match the reality. “This was CUTTING BOOTHS resolved,” he said, “by redoing the sectors affected. Other leaks occurred due to poor execution of the welding protocols, which was corrected during our regular reviews.” Another challenge that SEAT’s engineers had to overcome was the problem of extracting from the die components that included cable orifices. “We dealt with this by using elevations,” explained Mr Borruel. Other problems included contamination in the paint process, which meant the manufacturer had to modify its equipment; transfer times between the oven and the press, corrected by changing the lay-out; integration of different parts on the line; and treatment of waste material.” Looking towards the future, Mr Borruel said, “Vehicle-makers’ requirements are going to become increasingly demanding, which will mean using more parts made from this type of steel. Therefore, the number of hot-stamping facilities is also going to increase. Meanwhile, we still have further to go in the simulation field, in which we are working with AutoForm and Rovalma. We will continue to make advances in new tool materials and coatings and, finally, major new opportunities will arise in laser technology, as a latest-generation hot-stamping line may need support from as many as five laser booths. We see plenty of scope for improvement in this latter field.” AutoRevista • 59