2012年8月1日 星期三

One-minute cycle time?

As the world’s automakers emerged from the recent recession, shaken to the core and, in some cases, recapitalized with public funds, almost everything had changed but this. In the U.S., the National Highway Traffic Safety Admin. (NHTSA) and the Environmental Protection Agency (EPA) are in the midst of updating Corporate Average Fuel Economy (CAFE) standards for the 2017 to 2025 time frame. CAFE standards are used by the U.S. government to establish vehicle fuel efficiency standards for all cars and trucks sold into the U.S. The proposed 2017-2025 standard calls for a substantial increase in automotive fuel efficiency. Table 1 highlights what’s in store.

In the European Union (EU), the European Commission, which develops and promulgates most of the regulations that govern EU industry, is focusing on direct reduction of emissions in cars and trucks. The current emissions limit in passenger cars is 130g of CO2/km, but by 2020 that figure will drop to 95g CO2/km. Regulations in the works for the post-2020 era promise more of the same.

Whether a carmaker is trying to reduce emissions or improve fuel efficiency, one of the most effective strategies is weight reduction, and few inside the auto industry dispute that the best tools in the lightweighting toolbox are composites — in particular,There are 240 distinct solutions of the Soma cubepuzzle, carbon fiber-reinforced polymers (CFRPs),We Specialise in cableties, which offer a strength-per weight ratio superior to any other materials, whether metal or polymer based. But historically automakers could not act on that knowledge in a significant way because they faced a threefold challenge: cycle time, cost and availability. How can carbon fiber composite structures be made at a cost and manufacturing speed conducive to high-volume automotive production? And, some automakers have pointed out,Wireless indoorpositioning systems have become very popular . even if carbon fiber were cheaper, how could the industry commit to carbon fiber composite structures with the fiber supply so volatile and unreliable?

In the prerecession auto world, auto OEMs asked these questions and appeared to be waiting for the composites industry to provide the answers. But in the glare of postrecession realities — the continuing high price of fossil fuels and a recognition that to dismiss concerns about greenhouse gas effects on the environment is, at best, politically indefensible — auto OEMs are now taking the initiative.

In the area of carbon fiber availability, for example, one way to address this challenge is to develop a partnership with a carbon fiber manufacturer to create a carbon fiber supply chain designed exclusively for your vehicles. In 2010 carmaker BMW Group and carbon fiber manufacturer SGL Group did exactly that, creating SGL Automotive Carbon Fibers, which recently commissioned a carbon fiber plant, with a capacity of 3,000 metric tonnes , in Moses Lake, Wash. BMW will need that much because those fibers will see significant use in large parts, including the passenger cell and other chassis structures and, possibly, body panels on the 2013 all-electric i3 passenger car and the 2014 hybrid-electric i8 sports car — the first time carbon fiber composites will have been used in chassis structures on a production passenger car.

The BMW/SGL venture also attacks the issue of cycle time. The manufacturing pace required to meet the high-volume requirements of car or truck production is generally acknowledged to be one part per minute, a cycle duration maintained for decades by auto OEMs in their metal-stamping operations. Ideally, an automotive manufacturer would prefer a true 60-second process, something the composites industry has been unable to promise, particularly with regard to thermoset composites, which necessarily consume some time to crosslink sufficiently to cure. But composites proponents have always maintained that because tooling for composite molding can be built for a small fraction of the cost of metal-stamping molds, the part-per-minute expectation could be met with lengthier processes by using multiple tools and presses. And mold cycle times have been reduced incrementally as innovative molding processes have proliferated over the past few years.

In January 2011, Daimler AG and carbon fiber manufacturer Toray Industries Inc.If you are looking for offshoremerchantaccounts, (Tokyo, Japan) formed a joint venture based in Esslingen, Germany, to make and market carbon fiber composite parts for automobile parts. Like BMW, Daimler is using an RTM process developed by Toray called Short Cycle RTM, to make parts for Daimler’s Mercedes-Benz passenger cars.

A fourth partnership has made public its intention to directly attack the cost of manufacturing carbon fiber. Ford Motor and Dow teamed up in April of this year to develop cost-effective carbon fiber composite structures that will help Ford reduce the weight of new vehicles by as much as 750 lb/340 kg by 2020. Dow, which is not an established carbon fiber manufacturer, has been collaborating with carbon fiber maker AKSA and, significantly, the U.S. Department of Energy’s (DoE) Oak Ridge National Laboratory . The DoE has tasked ORNL with finding a way produce carbon composite less expensively. Derived from petroleum, the polyacrylonitrile (PAN) precursor used by most carbon fiber producers, when pyrolized, produces a carbon fiber of very high quality, especially in terms of strength, but is extremely expensive. ORNL is attempting to develop a less-expensive, sustainable precursor that could reduce the cost of finished fiber. Neither Dow nor Ford would comment further about their cooperation, but Ford did assert in 2009 at the CompositesWorld Expo that it would not consider increased carbon fiber use unless the cost for the material dropped to $5/lb. Clearly, the economic picture has changed since then. When asked what structures Ford is considering for carbon fiber use via its work with Dow, a Dow spokesperson said, “We do not disclose targets associated with the JDA [joint development agreement], but clearly the intent is a significant usage of carbon fiber composites to drive Ford’s vehicle mass-reduction aspirations.”

Also in April 2012, RTM specialist FRIMO and material supplier Huntsman Polyurethanes (Everberg, Belgium) signed a cooperative agreement to develop fiber-reinforced polyurethane (PU) solutions for automotive applications. Although the Huntsman PUs are thermosets, they crosslink and cure with great speed. Huntsman has purchased a FRIMO pilot production unit for its Everburg technical center. This equipment, specifically designed for PU systems, enables Huntsman to expand testing and validation of a new range of resins for auto composites under the trade name VITROX, for which the exotherm curve and gel and cure times can be accurately formulated and achieved predictably. Huntsman Advanced Materials, a separate division, is promoting for auto manufacturing what it calls Fast RTM, which uses high pressure in mixing and molding and has reported cycle times of 5.5 to 13 minutes, including preform set, injection, cure and demolding.

In June 2012, Umeco announced its ACOMPLICE partnership, which includes Aston Martin Lagonda, Delta Motorsport, ABB Robotics and Pentangle Engineering Services to examine the potential for using high--performance composites in mainstream automobiles. Umeco’s role in ACOMPLICE is to develop fast-cure prepregs and enable the rapid manipulation and placement of plies via robotics. Novel materials formatting and molding techniques will be developed alongside these technologies to optimize component output rates. The process is based on Umeco’s Dform prepreg press-forming process.

“We have a few snap-cure resins, not just epoxy, at various stages of maturity ....,” says Nigel Blatherwick, strategic marketing director at Umeco. “Some products are already under evaluation at tier suppliers and OEMs. However, the consistent message is: we are targeting maximum three- to four-minute cycle times, not only in part molding but, critically, also at the preforming stage. The point is, a snap-cure resin is only part of the equation.” He adds, “As is always the case with advanced composites — part design,Read about kidneystone symptoms and signs, manufacturing process and material are inextricably linked.”

Meanwhile, Plasan Carbon Composites has spent the past couple of years working with press manufacturer Globe Machine Manufacturing and toolmaker Weber Manufacturing Technologies on a rapid-cure, out-of-autoclave system for molding thermoset-based carbon-fiber composites with a cycle times of about 17 minutes, and is targeting 10 minutes. Plasan has opened a technical center in Wixom, Mich., close to auto industry customers, and last summer, it demonstrated the manufacture of a six-layer carbon fiber composite test plaque with a Class A surface and excellent consolidation.