Material advances drive extruded automotive seals





The automotive door modules on Chrysler’s 2007 Dodge Nitro and 2008 Jeep Liberty utilize Santoprene TPV bonded to polypropylene as a seal.

Molded by Faurecia, the door module’s seal reduced components and labor for the door assembly.

Weight reduction and simplified assembly are driving automotive OEMs and their suppliers to actively investigate and implement new technologies in areas like seals, eschewing stalwarts like polyurethane and thermoset rubber for thermoplastic elastomers (TPEs).

A recent example is the vehicle door core modules and critical seals for Chrysler’s 2007 Dodge Nitro and 2008 Jeep Liberty. Tier One supplier Faurecia has applied robotic extrusion of Santoprene thermoplastic vulcanizate (TPV) from ExxonMobil Chemical using machine technology from Reis Extrusion to create TPV seals that reduced assembly costs and logistics by consolidating parts, while improving seal performance, with the Santoprene able to adhere to a lower-weight glass-filled polypropylene (PP).

Faurecia says the switch to extruded TPV seals reduced capital expenses by 15%, lowered seal mass by 48%, and produced double-digit cost savings. The success didn’t go unnoticed, with the application recognized in the Chassis/Hardware Category of the 2007 SPE Automotive Division Innovation Awards.

Leaving no subassembly unturned

In a drive to cut vehicle weights, OEMs and their suppliers are taking a holistic view of cars, examining every subassembly and component. Faurecia targeted the door core module, which is a carrier plate on which sub-assemblies like window-lifting systems, electronics, door locks, and audio speakers are mounted and integrated. Because of its contents, the door core seal must offer a water-tight barrier to the elements on the other side of the door, as well as boost the acoustical performance of the door, preventing wind noise, rattles, and squeaks.

Door core seals are traditionally manufactured using an external molder applying thermoset EPDM rubber, which is manually assembled onto the module, or they can use PUR foam seal applied by the system supplier. ExxonMobil Chemical says PUR foam seal has limited profile geometry options, while also occupying floor-space and assembly time while the PUR cures before any further processing.

For more than a decade, ExxonMobil Chemical and Reis Extrusion have been jointly developing a robotic extrusion process utilizing Santoprene TPVs, with the first commercial applications coming in static weatherseals robotically extruded onto vehicle windows and seals on large PP underbody panels.

The companies say the robotic extrusion’s benefits include a reduction in labor costs since adhesives or mechanical attachment mechanisms are eliminated; faster cycle times since no curing is needed; greater design freedom with thin-wall geometry and profile extrusion in X-Y-Z directions; fully automated production set-up with the possibility for integrated injection molding and robotic handling; and the ability to bond to a variety of substrates.

The Faurecia Interior Systems subassembly includes an injection molded door core, made with glass-filled PP from ExxonMobil Chemical. Next, the TPV— Santoprene TPV 121-50E500—which is specifically designed for robotic extrusion, is applied, reportedly allowing the seal profiles to maintain their shape without any further support. The companies conducted relaxation and adhesion tests on the PP substrate to ensure the seal bond was strong, and design studies were undertaken to fine tune the profile geometry. Final testing to prove the effectiveness of the seals was conducted by Faurecia and Chrysler.

Prior to extrusion, Santoprene TPV E500 is melted in a conventional thermoplastic extruder and pumped into a heated, pressure-resistant, flexible hose. This hose is connected to a special extrusion die mounted on an industrial robot. With the door module fixed on a table, the TPV seal is extruded onto the module in the required position via the six-axis robot.

True bond

ExxonMobil chemical calls the TPV seal’s bond with the glass-filled PP substrate a cohesive one, adding that due to the TPV’s shear-sensitive nature, the profile remains in the desired shape without curing or calibration. Ready to go, the parts can be handled and transported almost as soon as the robot has moved away, saving tack/cure time by 90%.

Faurecia has taken workflow a step further so that the robotic extrusion process is set up where the left-hand and the right-hand door modules are injection molded, component sub-assemblies are installed, and both sides’ seals are applied by one robotic extrusion system in one location.

The companies say that this is the first time a TPV has has been extruded onto a door-module carrier, with the 360° coverage acting as a water barrier between the wet and dry sides, an acoustic barrier, and a seal against dirt and dust.

Web-exclusive: Customers, suppliers and you, in the same boat

This year McClarin became the first in its home state to hold a cooperative lean certification session. The session, conducted by Mantec, an industrial resource center for small-to-mid-sized manufacturers in PA, was to help its employees, as well as those from its customers and suppliers, work better together in recognition that ‘a rising tide lifts all ships’. Geiman calls the move “truly a change of culture” as customers and suppliers open up to each other, recognize that all of them need to earn a decent profit, and then work separately-but-together to improve. The session included 16.5 full workdays of training, which the processors spread over a half-year period. McClarin offered use of its facility and filled 22 of the 40 slots. Employees from throughout the company were selected by management to attend to become “lean leaders”.

Although its customer and supply base is international, for this first training session the firm stayed local, inviting employees from three local customers and a handful of local suppliers of parts for the sub-assemblies that McClarin purchases. The class included classroom training, ‘train and do’ sessions and then visits to other companies, including some of those suppliers and customers. He says this proved especially valuable as employees from various companies were mixed in small groups. McClarin purposely chose a few problem areas for the groups to visit, and has benefitted from the ideas sounded by the non-McClarin employees, who saw the business through new eyes. 

Geiman adds that processors need to go thick on leadership to implement lean. “I hear the same thing all the time at other companies where lean didn’t take hold. It takes leadership to say, ‘I’m not going to accept any less,’” he says. Leadership is critical, he says, to ensure all employees recognize that changing their behavior to a ‘lean’ one is for the good of the firm, which trickles down to the good of all of the employees. He notes that McClarin’s Kennedy is a constant presence throughout the company, encouraging and educating employees. McClarin, he says, spent a lot of time with its employees to develop the appropriate measurements/goals for its workforce. “A lean environment will never take hold unless you can measure your results,” he explains.

“We were ferocious in our approach,” Geiman says. “I really feel sorry when I go into places where they say they tried but it wouldn’t work; it just shows a total lack of leadership.” He agrees that it is difficult to change a company’s culture, but the benefits are worth it as a company transforms itself to almost “become indispensable” as a supplier, he says, by ensuring its quality is extremely high, its competence is great and its dependability is unquestioned.

One critical ingredient is also to stay on top of costs, he notes. Foreign or lower-cost competition always is present, he says, but adds, “If you do it (become indispensable) in a way in which you’re on top of your costs, then you should be fine.”

 

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