Plastics have advanced a range of industries since being employed for widespread use. Auto makers especially have used plastics in an effort to engineer high-performance, low-cost parts and systems. For example, about half of the fuel tanks installed in today’s passenger cars, SUVs, vans and light trucks are made of plastic instead of steel.”A lot of people don’t know about plastic fuel tanks and make the assumption they’re steel,” says Greg Fuller, vice president of operations. “The reality is there’s now a good mix of both steel and plastic fuel tanks out there and that goes for domestic and imported vehicles.”
Kautex Textron is a leading full-service supplier of advanced fuel systems, plastic fuel tanks and blow-molded functional components and other industrial products. In 1997, Kautex was acquired by parent Textron Automotive Company, a global supplier of automotive and aerospace systems and components, recognized for breakthrough proprietary technologies and quality.
Kautex Textron has more than 5,250 employees in 31 locations around the globe. In the U.S., manufacturing operations are concentrated in Avilla, Ind. where 450 employees in 180,000 square feet of production space put out roughly 10 percent of domestic gas tanks, about two million parts annually.
Plastic is not exactly the new kid on the block. Blow molding of plastic for this application is a European technology developed and refined for many decades.
“Customers are comfortable with plastic, it’s a proven technology, not something that just grew up a few years ago,” Fuller says.
Plastic continues to compete with steel, which has the advantage of its impermeability. However, today’s high-tech plastic compounds are designed to prevent leaching of fuel. Plastic even enjoys an edge over steel in many respects. For instance plastic is corrosion resistant compared to steel and stands up to hazardous road conditions.
“Blow molding of plastic fuel tanks makes the shape easier to achieve. The plastic will ‘give’ in a car accident where steel won’t,” Fuller explains. “Plastic fuel tanks perform well during an impact because of the ability to flex and return back to their original shapes.”
Fuel For Thought
The fuel tank is just one component in a system designed to deliver not only fuel but safety.
“A gas tank has a dual purpose. Obviously, one is to deliver fuel for the vehicle. The other is to perform in a crash,” Fuller says. “It’s very similar to a seat belt or an air bag because it’s part of the vehicle but it also has a specific function in case of an accident and that’s not to leak fuel.”
Kautex Textron product engineers work with OEMs for several years on fuel tank design and prototyping before the tank goes into mass production. The company utilizes an integrated design, production and extensive testing protocol to ensure that the tank and the fuel system adhere to specifications.
The process begins with a system concept incorporating the fuel supply itself, measurement, filling, ventilation and aeration. In addition to the fuel container, a number of parts and modules contribute to the fuel delivery system. These include pipes, connections, locks, pumps, valves, filters and sensors, among other parts. The production process of these critical components is carefully orchestrated working with the OEM customer to fulfill the design parameters while meeting ever more stringent government regulations. These are not parts that can be standardized or offered through a catalog or dusty warehouse. Each vehicle model has its own fuel system profile.
“Different vehicles have different tank shapes and placements, but the majority of fuel tanks are inside the frame rail and behind the driver in an area not susceptible to full-blown impact,” Fuller assures us. “Fuel tank design and placement has come a long way and the OEMs are very concerned about where fuel tanks are placed as well as the rigidity and safety of the fuel tanks they place in their vehicles.”
Process and system simulation are important phases of production to refine development of new fuel systems. Computer simulations of blow molds, filling, pressure/vacuum effects, and crash tests all help reduce development cycles and add design flexibility to new fuel tank systems. Validation testing is conducted on manufactured systems to analyze regulatory and customer requirements such as operational safety in all driving conditions.
“Extensive testing goes on before a program is launched as well as afterward to ensure the quality of the tank and adherence to specifications,” Fuller says.
While the fuel system integrates with many other automotive systems throughout the vehicle, the tank itself is the major focus for Kautex Textron.
The blow-molding process allows ultimate control of the production of the gas tank in shapes ranging from the traditional elongated cigar tank used in most pickup trucks to concepts such as saddle bags and other designs that automotive engineers divine.
“Plastic is easier to mold into more difficult shapes versus steel, which has its limits,” Fuller says. “You can do some things with plastic you can’t do with steel.”
The blow-molding process capitalizes on the advantages of the material. In blow molding, plastic is pushed through an extrusion head to create the shot known as a parison. That parison is then extruded down into the mold cavity. When the raw material is the proper length, the mold closes on it. Compressed air is pumped into the mold cavity to force the plastic into the shape of the tool. Kautex Textron uses suppliers for the mold die and raw material.
To optimize impermeability, the tank has a barrier layer of high-tech plastic.
“Before the barrier layer was introduced in the current process, they used to fluorinate tanks,” Fuller remembers. “Tanks were exposed to fluorine gas to prevent fuel from evaporating through the skin. So technology continues to evolve and we no longer use a hazardous substance to seal the tank.”
Since the acquisition by Textron, the Avilla plant has transformed itself into a world-class operation befitting its global corporate lineage. Operational efficiency has vastly improved with a one-piece flow approach replacing cumbersome batch operations. Benchmarking and training, along with computer production controls, have resulted in quality awards from customers including Honda and Daimler Chrysler. The plant already meets the new, tough TS 16949 international automotive quality certification.
Although a highly specialized field, competition remains intense in fuel tank manufacturing. “This industry typically sees a reinvention of itself every seven years,” Fuller notes. “It’s driven by competition and government standards for emissions and safety. These all drive our capital investment in plant and production upgrades to meet the customer’s expectations for a better product at a competitive price.”