By: Hans Greimel
January 7, 2013
Automakers are increasingly considering carbon fiber — particularly for hoods, roofs, trunk lids and aerodynamic parts such as spoilers — as an option as they seek to cut weight from vehicles to boost fuel economy. The material is stronger and lighter than steel. The LFA’s carbon-fiber body weighs just 193 kilograms, or 425 pounds.
But it is also extremely expensive. Cost relegates it mostly to the league of exotic sports cars. If more manufacturers used carbon fiber, the cost would come down. But until the price comes down, they won’t widely use it.
Toyota approached carbon-fiber production as it has other manufacturing technologies: It brought the process in-house to see whether the famed Toyota production system could eke out efficiencies.
Behind the doors
A peek behind the doors of the LFA Works when it was still in operation showed why the LFA and its carbon-fiber components are so pricey.
From start to finish, it took three weeks for a single LFA to wind through assembly. Two of those weeks were spent mostly laminating and molding carbon sheets made of carbon fibers. Only one car was completed in an eight-hour day.
About 170 people toiled in the LFA Works, around 100 of them in the carbon-fiber unit, where much of the work was done behind glass in immaculately clean rooms reminiscent of those in a computer chip factory.
There are three ways to make carbon-fiber composite, properly known as carbon-fiber-reinforced polymer. Toyota does two in-house.
The first, called pre-preg, consists of using sheets of woven carbon-fiber fabric pre-impregnated with sticky resin. It is the most expensive and strongest type of carbon-fiber composite.
The second is resin transfer molding. RTM is the next-strongest type and is slightly cheaper.
The third approach, which Toyota outsources, is carbon sheet molding compound. It is the weakest and cheapest carbon-fiber composite, though still much stronger and lighter than steel. It bonds chopped-up shreds of carbon fiber in an epoxy soup.
Hair dryers, spatulas
Pre-preg and RTM are labor- and time-intensive processes. Toyota won’t say how many people worked on those processes. But the pre-preg room teemed with people laying down precision-cut pieces of carbon fiber into a pattern that would be the LFA’s instrument panel.
Workers used hair dryers to heat and soften the resin-infused carbon-sheet cutouts, then conformed them to nooks and crannies with a spatula.
The laid-out panel was then put into a giant autoclave pressure cooker for eight hours. What came out was a single piece.
The RTM process was just as tedious.
Workers wrestled giant sheets of dry carbon-fiber fabric so it would adhere to a mold for what would be the tunnel for the LFA’s transmission and propeller shaft. It was like trying to wrap a newspaper smoothly around a football. The sheets constantly slipped out of place. And once wasn’t enough. Each tunnel needed eight layers.
“We have problems all the time with misalignment. And if you pull too hard on the sheets, you can rip holes in the fiber,” said a person involved with LFA development. Still, RTM was less labor-intensive than pre-preg.
Under both processes, a single component required eight hours for layering and then another eight hours for curing.
Looms to cars
Toyota also spins its own carbon fiber. In this regard, Toyota has come full circle: Before the Toyota Group began making cars in 1936, it made its fortune in automated looms for Japan’s textile industry.
Now it is putting looms to work again. A giant circular loom weaves together 144 carbon-fiber threads, each a tight bundle of 24,000 strands of carbon fiber, each thinner than a human hair. Another loom weaves those threads into a flowing, graphite cloth that shimmers with carbon fiber’s trademark crosscheck texture.
When all the subcomponents were cured and ready, they were glued together like a kid’s plastic model to form the LFA body. Then, that too went into a giant oven. Once the adhesives were cured, the carbon body was complete.
After the last LFA was delivered in December, roughly two-thirds of the workshop’s employees returned to their previous divisions. The rest stayed, churning out carbon-fiber parts.
Japanese carbon-fiber makers, led by Toray Industries Inc., account for 70 percent of the world’s supply of carbon fiber. Japan’s government promotes the industry as one that will have benefits for other sectors, especially autos, if Japan’s manufacturers can rapidly reduce costs.
While the LFA undertaking has now thrown Toyota into the mix, it is unclear how competitive the carmaker’s technology is.
Lamborghini, Ferrari, Bentley and McLaren all use carbon fiber in their cars and are likewise pioneering manufacturing techniques and composites. Some say they have cut the time for certain stages of production down to minutes, compared with hours at Toyota.
Bentley, for instance, has added cobalt to its carbon fiber to make it magnetic. This allows the company to use magnets to automate manufacturing, which cuts costs and speeds production time.
The LFA’s outer panels, by contrast, are all carbon fiber and no more magnetic than other forms of plastic. But the electrostatic painting commonly used in vehicle mass assembly won’t work on plastic. So certain parts had to be painted by hand.
Lamborghini uses a system called “forged composite,” which it said is faster than pre-preg and autoclave processing.
BMW AG has created a joint venture with SGL Carbon SE in Moses Lake, Wash., to mass produce carbon fiber and develop in-house processing. The venture’s site was chosen to take advantage of less-expensive hydroelectric power, yet another sign of how the industry is seeking any advantage in lowering costs.
Yet it may simply be more cost effective to turn over the manufacturing of carbon fiber and carbon-fiber products to the established makers that already have achieved mass scale.
Last year, General Motors Co. partnered with Japan’s Teijin Ltd. to develop carbon-fiber car parts that might be used in GM vehicles. At the time, GM said Teijin had the potential to produce them using a thermoplastic material that can be molded in less than one minute.
As part of that project, Teijin opened a technical center in Auburn Hills, Mich., in March 2012, to spearhead research into automotive applications of carbon fiber.
Toyota said it is evolving its technology as well, seeking to improve productivity and cut costs. In the future, it sees itself shifting more toward RTM and away from pre-preg. Its RTM process uses lower pressures than older techniques, vacuum assist and injection presses, which allow it to be more flexible and faster than traditional methods.
At the very least, Toyota’s experiment with carbon fiber gives it an insight into the costs and manufacturing technologies involved.
Toyota has a history of gauging its suppliers’ prices and quality by making similar parts in-house as a benchmark. It then uses that expertise in negotiating prices with suppliers and working with them to find efficiencies.
The carbon-fiber factory means Toyota will know the ropes for those parts, too.
“This is a success because we have nurtured an expertise in developing the technologies and techniques needed to make the carbon fiber,” Toyota spokesman Keisuke Kirimoto said. “When advancements are made in speeding up the curing time of the resin, this accumulated knowledge will be used in the future.”