Beam focus control in rapid laser cutting

Abstract

Laser cutting is exploited by manufacturing industries due to the nature of its flexibility. There are a number of factors that dictate the cutting performance of this processing technique. One of such factor is the location of the focused spot on the work piece. No material can be considered to be perfectly flat and also thermal distortion will come into play during the cutting process thereby altering the position of the focused spot on the cutting surface. The main consequence of this is a drop in the cutting speed. Edge cut quality will also be affected by change in focus position. A parameter, the depth of focus, defines a region within which constant cutting performance can be maintained. Depth of focus can be evaluated using a number of definitions and each of these give varying regions. Therefore it had been important to investigate the practical range under which a constant cutting performance would be achieved. These ranges have been determined using different focal length lenses and raw beam sizes that are the main factors of influence. The change in edge quality for the different set-ups has also been evaluated. These investigations provide a ground on which to decide the criticality of the resolution of the height sensing during the high-speed laser cutting process. Based on this an optical height sensing system has been incorporated to provide constant cutting performance.Laser cutting is exploited by manufacturing industries due to the nature of its flexibility. There are a number of factors that dictate the cutting performance of this processing technique. One of such factor is the location of the focused spot on the work piece. No material can be considered to be perfectly flat and also thermal distortion will come into play during the cutting process thereby altering the position of the focused spot on the cutting surface. The main consequence of this is a drop in the cutting speed. Edge cut quality will also be affected by change in focus position. A parameter, the depth of focus, defines a region within which constant cutting performance can be maintained. Depth of focus can be evaluated using a number of definitions and each of these give varying regions. Therefore it had been important to investigate the practical range under which a constant cutting performance would be achieved. These ranges have been determined using different focal length lenses and raw beam si...