Racing has been the proving ground for technical developments in the automotive industry since the early days of dirt tracks and race cars with mechanics on board. When a racing team, in any given racing season, suddenly pulls away from the pack, it's usually a sign that they're on to something new.
This happened just a year or so ago when laser honing was "discovered" by racing teams on several of the major racing circuits. Engine performance and race results improved dramatically when the process was used to finish the cylinders of these high-performance engines.
"Laser honing of cylinders produces a superior surface match with piston rings that reduces friction blowby and wear," explains Olaf Tessarzyk, president and CEO, Gehring L.P., Farmington Hills, MI. "The laser honing process gave the racers who adopted it a big competitive edge."
Its potential for engines has not gone unnoticed by the Big Three automakers who are integrating the process into their transfer machining lines in the U.S. and Europe. Initially they have targeted diesel engines because of the ability of laser honing to dramatically reduce emissions.
Introduced in 1997 by Maschinenfabrik Gehring GmbH, Ostfildern, Germany, the laser honing process combines laser structuring with conventional honing to produce a microstructure in the cylinder wall for both high bearing capacity and excellent gliding properties. It also produces an open structure to ensure lubricant retention.
The microstructure comprises pockets (either spiral or cup structures) that are drilled into the cylinder wall by a laser beam. After laser machining, the cylinders are finish honed to remove the buildup of any molten mass on each side of the groove. The new automotive production sequence is rough honing, semi-finish honing, laser structuring and finish honing.
The benefits of laser honing cylinders are dramatic, says Tessarzyk. "They include reduction of oil consumption, improvement of emissions, reduction of wear and a subsequent increase of service life, higher degree of efficiency and reduced friction losses resulting in lower fuel consumption."
The simple explanation is that the lubricant adheres better to a laser-honed surface for optimal tribological conditions for bearing and lubricating qualities. As a result, any stressed component that can benefit from a better design for lubrication offers good potential. Typically, pieces like guide-ways, slide bushings, axial face seals, control...