Coming clean
03/01/2008
By Bruce Flickinger
Cleanliness and critical environment controls are essential for the manufacture of modern automobiles. A new standard could help harmonize disparate testing practices in the EU
Quality management systems, embodied in recognized standards such as ISO and in the meticulous specifications used by individual manufacturers, have been integral to the resurgence and success of the automotive industry since the 1980s. Today, automobile manufacturing is among the most stringently controlled industrial sectors, driven by ever-rising demands for performance, safety, and efficiency.
Cleanliness and environmental controls clearly are paramount to meeting these goals. This is true not only for sensitive electronic components, but also for precision mechanical parts, such as those found in transmissions, fuel injection, oil circulation, and braking systems, as well as painting and finishing technologies. Across the spectrum of automobile assembly, there is a direct correlation between cleanliness and product defect rates. The term “cleanliness” has progressed to become a quality feature and is now often specified on component drawings or in quality agreements in the same way as size accuracy or surface roughness.
“Clean technology always trickles down, and car companies and OEMs [original equipment manufacturers] are finding they need to have controls that they didn’t need before,” says Duane McKinnon, president of Simplex Isolation Systems (Fontana, CA). “Twenty years ago, cleaning basically meant degreasing, and the engines being assembled in the plants could be assembled in your garage. Engine and transmission tolerances are so much tighter now that you need at least a Class 100,000 room to do the work.”
Metal cleaning and degreasing has become more complicated and demanding. With restrictions on the use of halogenated hydrocarbons as solvents, “resulting cleaning systems have become much more complex in order to achieve the same degreasing performance as before,” says Markus Rochowicz, PhD, with the Department of Cleanroom Manufacturing at the Fraunhofer Institute for Manufacturing Engineering and Automation (Stuttgart, Germany).
Furthermore, “chemical degreasing as a cleaning process has become insufficient to meet demands for the thorough removal of tiny amounts of residual particles of a few hundred microns. This has led to the development of cleaning systems equipped with more effective mechanical cleaning components,” Rochowicz says. These include ultrasound, intensive flooding of components, and lances that are “introduced into single borings and clean them by pressure-rinsing them with jets of water under pressures of several hundred bars.”
Tightening tolerances
Precision mechanical components must be cleaned and handled in the broader automotive assembly environment, where oil mist and metal particulates from robotics and other fabrication equipment pervade the air. “The focus is on setting up white rooms, or protection zones, to isolate paint and finishing, and critical manufacturing areas to prevent cross-contamination,” McKinnon says. “The airborne contaminants tend to settle and need to be kept out of areas such as engine and transmission assembly.”
In additional to supplying modular cleanrooms and industrial enclosures to automobile manufacturers, Simplex works with companies that make dash pods, air bag sensors, and door lock electronics, including new systems that incorporate fingerprint readers. “Dust and airborne particulates are the primary contributors to defects in these products,” McKinnon says.
A contaminating particle located in the wrong place on a component can potentially impair its function or cause it to fail. One example is diesel injection technology. “The rapid increase in performance since the second half of the 90s has led to constantly rising injection pressures as well as injection nozzles with smaller and smaller nozzles,” Rochowicz says. “The high-pressure pumps used are capable of pressures up to more than 2,000 bar and dispense fuel into the combustion chamber via apertures just 100 µm in diameter. Ensuring a high degree of cleanliness of the various parts, when manufacturing such systems, is no longer sufficient. Even the assembly processes need to be carried out under highly clean conditions.”
Injection systems speak to the fact that, while many automotive components must have a highly clean surface, these critical areas are often located in the part’s interior. Many parts are complex metal structures that are machined into their final shape after molding and contain media-conducting borings or inner surfaces that require a high level of cleanliness. The only way to check the degree of cleanliness of such parts is to extract any particulate contamination that might be present via a cleaning process and then analyze the cleaning fluid. To do so, particulate contamination is usually deposited on a filter membrane for microscopic or gravimetric analysis.
Learning from electronics
Particles of concern in the manufacturing environment typically are large enough that they tend not to be aerosolized, but rather drop onto surfaces, presenting a different air management scenario than that found in a semiconductor cleanroom. Still, the window of concern is getting smaller, and contaminants such as metal, fibers, skin flakes, and spittle–ranging from 80 to 120 µm on the large end, to smaller particles from 40 to 60 µm in size–need to be controlled. Users have the same goal as conventional cleanroom users: preventing visual and functional defects in the product.
It is not surprising, then, that some companies are expanding into automotive from a base in more traditional cleanroom sectors. One example is Fabrinet (Patumthanee, Thailand), a global engineering and manufacturing services provider of optical and electromechanical components, which has been able to parlay its success in DEL semiconductor and high-density drive fabrication into a burgeoning business supplying components to auto manufacturers worldwide.
“We felt we offered a compelling solution to our base of automotive customers: a real differential advantage in manufacturing,” says Mike Alarid, senior vice president, materials and overseer of Fabrinet’s automotive business. “We offered a more stringent, disciplined approach to manufacturing, along with a global delivery mechanism that the car companies were looking for from their contract suppliers.”
Fabrinet primarily operates Class 1000 and Class 100 cleanrooms throughout its operations, and uses a unique system of manufacturing bays in which individual conditions can be controlled and configured for different customers and their requirements. “The automotive components we were initially making didn’t need this level of control, but it’s more efficient to maintain a level of control than it is to rebuild down,” Alarid says.
He continues, “The industry has really transformed itself throughout the supply chain. Car makers look at every aspect of their contractors’ quality systems and their ability to manage that system.” Suppliers in Fabrinet’s space ‘need to manage to 0 dpm [defects per million] for the Tier 1 companies,” he says.
Testing standard evolves
Complex systems are, by their nature, more sensitive to particulate contamination, so while achieving lower defect rates becomes a greater challenge, it is the key business metric for any company along the automotive supply chain. ISO assurances, including ISO 16232 Cleanliness of Components, are just an entry point; manufacturers have much more stringent individual auditing systems and operate auditing groups attuned to their specific needs and standards.
“Just as with all other quality values, there is also a need to measure and document a component’s degree of cleanliness,” says Fraunhofer’s Rochowicz. Currently, however, there is no industry standard for testing cleanliness; the testing systems and standards used by different companies are convoluted with varying parameters, such as “the high number of possible cleaning methods and cleaning media which are implemented, and which give different cleaning results,” he says. “It is impossible to obtain comparable, reproducible residual contamination results in this way.”
VDA Volume 19 is an effort to bring some standardization to this complicated mix. The standard is the product of an industrial alliance formed in 2001 under the coordination of Fraunhofer IPA. Called TecSa (Technische Sauberkeit), this consortium comprises 25 companies, encompassing not only German automobile manufacturers and supplier companies but also manufacturers of cleaning systems and cleaning media. Volume 19 is now available through the Quality Management Center of the German Automotive Industry Association (VDA-QMC).
This standard, which is compatible with ISO 16232, establishes fixed procedures for each type of cleanliness test, specifies the analytical equipment to be used, gives recommendations for selecting a suitable test procedure, and states precisely how the procedure is validated. The overarching goal is to “detach all removable particulate contamination from the component in a single extraction process without damaging the part or the surfaces,” Rochowicz says. Depending upon the geometry of the test components, the user may choose one of four different extraction methods: pres-sure rinsing, internal rinsing, ultrasound, or agitation.
Another aim is “to avoid having to send parts to a few select laboratories for cleanliness analysis,” Rochowicz says. It stipulates the use of blank values adapted to components that compensate for the influence of external sources of contamination on the actual test, such as surrounding air, test set-up, test media, or staff. In this way, “the laboratory and test equipment are only as clean as the level required by the component itself. This allows most of the tests to be carried out in industrial laboratories.”
Rochowicz stresses that, in its current form, VDA Volume 19 is only concerned with testing the cleanliness of components and does not state how clean certain parts need to be in order to function correctly.
Educating an industry
Another point of emphasis is that “cleaning technology cannot be expected to straighten out mistakes made in preceding process steps,” Rochowicz says. The manufacture of technically clean products requires an integrated approach to development, construction, manufacturing planning, logistics, and quality assurance stakeholders. This, in turn, calls for concerted on-the-job and vocational training to better infuse the tenets of cleaning and quality throughout the manufacturing enterprise.
“In Germany, there is no specific training available in industrial component cleaning. Most of this knowledge is held by the manufacturers and users of cleaning technology in industry, along with a number of institutes focused on cleaning technology,” Rochowicz says. “Many of the problems that are currently being discussed have not yet been systematically investigated or solved, so there is demand for both knowledge transfer and increased research and development activities.”
Resources
Fabrinet
Patumthanee, Thailand
www.fabrinet.com
Simplex Isolation Systems
Fontana, CA
www.simplexisolationsystem.com
European Automobile Manufacturers Association (ACEA)
Brussels, Belgium
www.acea.be
Fraunhofer Institute for Manufacturing Engineering and Automation (IPA)
Stuttgart, Germany
www.ipa.fraunhofer.de
TecSa
www.technische-sauberkeit.de
German Automotive Industry Quality Management Center (VDA-QMC)
Oberursel, Germany
www.vdaqmc.de