Laser Texturing Slashes Cylinder Wear
Susanna Contini Hennink
Laser texturing of engine cylinder walls may reduce oil consumption by 40 percent compared with traditional cylinder machining techniques, according to a manufacturer of engine honing equipment.
Machine honing of engine cylinder walls gives them their final dimensions, shape and finish. In the final stage of honing, the cylinder wall receives a surface texture that is designed to allow a friction-reducing oil film to form. This protects the cylinder surfaces from wear and reduces engine oil consumption.
Laser honing can produce engines that burn less oil and produce fewer hydrocarbon emissions than mechanically honed engines.
Officials at Maschinenfabrik Gehring said that optimizing the cylinder wall surface structure reduces wear at the piston rings and on the cylinder walls by about 50 percent. One way of doing this is to use a laser. Laser texturing creates pits surrounded by hardened areas on the surface of the casting. Subsequent final honing grinds off any protruding peaks on the surface but leaves the pits. Both the pits and the slightly rough-surfaced grooves created by laser pulsing help retain motor oil.
According to the company's research, this "bumpy" surface reduces oil consumption (up to 40 percent), particle emissions (10 to 30 percent) and hydrocarbon emissions (about 20 percent), compared with mechanically honed engines.
The surfacing can be more tightly controlled as well. Whereas conventional honing applies the textured surface over the entire depth of the cylinder wall, manufacturers can apply the laser texturing just to the part of the wall where the piston rings rub when the pistons are at top dead center. This allows a more accurately controlled, finer patterned textured surface.
Gehring has incorporated the laser into its standard honing machine by replacing one of the spindles with a laser station. The system can accommodate bore diameter variations up to 40 mm. This means that users need not replace entire honing assemblies to fit bores with different diameters, as is the case with conventional honing systems.
The company said the cost of a laser machining head, drive spindle and laser source is comparable to that of a conventional honing head and drive spindle.
Customers have been testing prototype laser honing systems since 1995. The company has applied the process to parts made of many materials including cast iron, compacted graphite iron, aluminum alloys, ceramics, nicasil coatings and several steel alloys.
Gehring affirms that the technology is suitable for use on all parts where reduction or optimization of oil consumption is desired.
Although the technology has been ready for series production since early 1997, hot engine testing at several sites has required nine to 12 months per test, the company said.
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