A new dulling system for the work rolls used to roughen the surface of cold rolled steel sheet has been developed. Such sheets are used in various products, such as outer panels of automobiles, and decorative outer plates of electric appliances. In this process, several pulsed laser beams generated by Q switched Nd:YAG lasers produce small craters with rims around them. This process includes a longitudinal scanning system within the laser processing head and a rotation system for the work roll; consequently, the surface of the dulled roll consists of innumerable small craters. The main features of the system consist of: (1) a special way of controlling RF power applied to the acousto optic modulator for the Q switching to change the peak power, pulse duration, and low level CW power to fit the dulling condition, (2) a method to combine two or more pulse beams to control the profile of dulling craters. Immediate advantages of this process are: (1) timesaving (very high repetition rate of pulses by Q switching), (2) stable operation (without a mechanical chopper which is usually used with a CO2 laser to make pulsed beam), and (3) cost saving. This newly developed system is effectively applied to the production of cold rolled steel sheets.
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