Material processing with a high average power and high beam quality continuous wave Nd:YAG laser

Abstract

The development of high average power continuous wave (CW) Nd: YAG lasers which can generate 4.5kW at the laser source is generating wider industrial interest, particularly from industry sectors such as automotive, aerospace, chemical, defence and power generation. The main attribute of these high power Nd: YAG lasers is the high beam quality (25mm.mrad), which allows transmission of laser energy through a small diameter fibre optic (600μm diameter). Another benefit of using higher average power coupled with a good beam quality is the possibility of increasing working distance (distance between the workpiece and the focusing lens) up to 200mm, whilst maintaining the power density required for processing. This reduces the likelihood of damage to the optics from the spatter generated during welding, and hence extends the life of the coverglass slide, which protects the focusing optic. This is of particular benefit when welding zinc coated steels, which tend to produce significant spatter. Additionally, a longer focal length of focusing lens increases the depth of focus, allowing greater tolerance to variations in workpiece or motion system positioning.This paper describes a number of materials processing applications with Lumonics new MultiWave-Auto™ laser, which is capable of delivering 3.5kW at the workpiece at end of lamp life. Examples of performance of this laser include: welding of tailored blanks at 11m/min; T-joint welding in 6mm structural steel at speeds over 1m/min; cutting of 2mm aluminium alloy sheet over 20m/min. This paper also highlights results achieved with an experimental laser capable of producing 5kW at the workpiece and results obtained at TWI with a laser power of 7kW. The latter was achieved by combining two Lumonics MultiWave Auto™ lasers giving two individual spots at the workpiece.The development of high average power continuous wave (CW) Nd: YAG lasers which can generate 4.5kW at the laser source is generating wider industrial interest, particularly from industry sectors such as automotive, aerospace, chemical, defence and power generation. The main attribute of these high power Nd: YAG lasers is the high beam quality (25mm.mrad), which allows transmission of laser energy through a small diameter fibre optic (600μm diameter). Another benefit of using higher average power coupled with a good beam quality is the possibility of increasing working distance (distance between the workpiece and the focusing lens) up to 200mm, whilst maintaining the power density required for processing. This reduces the likelihood of damage to the optics from the spatter generated during welding, and hence extends the life of the coverglass slide, which protects the focusing optic. This is of particular benefit when welding zinc coated steels, which tend to produce significant spatter. Additionally, a lo...