In this paper the authors have investigated the use of high average power Q-switched diode pumped solid-state lasers at the fundamental IR wavelength for engraving metals. It has been demonstrated that it is possible to rapidly laser engrave both aluminum and stainless steel achieving material removal rates of >90mm3/min and >25mm3/min respectively. It is also demonstrated that material removal rate is a function of irradiance on the work piece. Furthermore the material removal rate must be balanced against the desired quality of the engraved feature - it is shown that high material removal rate can result in poor quality, quantified in this case in terms of roughness. Having qualified this laser engraving technique the authors then seek to apply it in an attempt to modify the surface qualities of uncoated aluminum in order to be able to create scanner readable barcodes. To develop this process further the same technique is applied to two other commonly used automotive metals, galvanized steel and stainless steel. In both case the result is the reverse for aluminum. The laser engraved regions absorb more strongly than the virgin material. Contrast is also greatest at a low angle of incidence. Therefore high quality scanner readable barcodes can be made on these materials using the same type of laser, but they are made using conventional barcoding logic, i.e. the laser engraved region reads 'black' and the virgin region reads 'white', and that best contrast is close to the normal angle of incidence. Optimal settings are found to be a 5 deg read-angle and the laser engraving at 30kHz with a 75% pulse overlap. Samples are created for all three materials and tested with an industrial scanner manufactured by SICK GmbH. All are found to read easily and with a high degree of tolerance, corroborating this analysis.
Laser engraving scanner readable barcodes on automotive materials for traceability and security applications
Laserstrahlgravierte, Scanner-lesbare Strichcodes auf Kraftfahrzeugwerkstoffen für Zwecke der Rückverfolgung und Sicherheit
2006
10 Seiten, 18 Bilder, 1 Tabelle, 9 Quellen
Aufsatz (Konferenz)
Englisch
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