This paper deals with the monitoring of the protective glass in a laser cladding head specifically designed for high power active fiber laser beams. The available high power density that can be focused on the workpiece surface is not only one of the most well known positive features of the fiber laser sources but becomes a very critical thermal load acting on the optical elements of the cladding head, in particular in dirty processes such as the laser cladding. The cladding powder indeed coming from the powder cone is likely to interact with the optical elements of the cladding head. As a result the optical elements become locally opaque and absorb the laser beam, with consequent thermal deformation, coating damage and lens breakage. The protective glass, that divides the focusing and collimation lenses from the dirty work area, has the fundamental role to protect the entire optical chains and represents the element whose life has to be continuously monitored in order to avoid unexpected and unpleasant lens damages. The paper presents the study of a monitoring device aimed at monitoring the life of the protective glass making use of the scattered light from the protective glass. The developed monitoring device is able to recognize both small (i.e. cracks) and big defects (i.e. diffuse opacity) on the surface of the protective glass. In order to test the developed monitoring system a real industrial case is investigated making use of a new prototypal laser head assisted by the monitoring device.

Date Published: 11 May 2012
PDF: 8 pages
Proc. SPIE 8433, Laser Sources and Applications, 84330S (11 May 2012); doi: 10.1117/12.924555

Published in SPIE Proceedings Vol. 8433:
Laser Sources and Applications
Thomas Graf; Jacob I. Mackenzie; Helena Jelínková; John Powell, Editor(s)