TWI Industrial Member Report Summary 518/1995
M A O'Key and M R Osborne, AEA Technology
For consistent quality in laser processing - whether in welding, cutting, surface treatment etc, it is essential to minimise variations in the size and shape of the focused laser spot, within which the processing power of the laser is contained. It is also necessary to maintain the position of a focus with respect to the work surface within a well defined range related to the depth of focus. These aspects are not controlled by the laser power alone, but also by the 'quality' of the laser beam. With the extensive choice of industrial lasers now commercially available, and the increasing diversity of applications in materials processing, the need for on-line monitoring of beams for characterisation and QA has never been more important. Thus the overall aim of this project was to determine the most suitable technique(s) to characterise adequately an on-line laser beam for given processes, using the minimum of data storage capacity. The three major industrial lasers evaluated were CO2
This report presents data on application-specific beam parameters; a survey of laser-user opinions on beam monitoring; and commercially available beam monitoring systems. Experiments have been performed to assess the suitability of three devices for on-line sampling of intensity profiles, and phase profile measurements using two different interferometers have been carried out. On-line monitoring of excimer, YAG and CO2 lasers has been undertaken, together with an investigation into an alternative novel monitoring technique applicable to the three laser types.
The objectives of the work summarised in this report were:-
- To survey the beam monitoring requirements and attitudes of a range of industrial laser users.
- To assess and compare beam monitoring techniques.
- To identify and produce recommendations on on-line beam sampling, monitoring and measurement techniques appropriate to both pulsed and CW high power lasers.