Page 73 - Welding of Aluminium and its Alloys

Preparation for welding 63

4.8 Laser welding and cutting work cell. Courtesy of TWI Ltd.

Visible radiation is also emitted during laser cutting,this light being similar
to that produced from a welding arc containing both ultra-violet and infra-
red light.To filter this out requires tinted filter glasses,the density of the shade
being sufficient that no discomfort is felt when viewing the bright plume asso-
ciated with the beam. This radiation may also cause skin reddening. It goes
without saying that all personnel involved in laser processing operations
should be fully trained in the use of eye and skin protection equipment.

4.5 Water jet cutting

Water jet cutting uses an abrasive powder introduced into a very high-
pressure and velocity water jet and is capable of cutting both metallic and
non-metallic materials essentially by a process of erosion. Water velocity is
in the region of 2500km/h (1600mph) and water pressure between 2000
bar (30000psi) and 4000 bar (60000psi). One of the most important uses
of water jet cutting is the roughing out of parts prior to finish machining.
The great advantage that water jet cutting has over the laser or plasma-arc
is that no heat is used in the process. There are therefore no heat affected
zones and no thermal distortion.Parts can be cut very accurately and closely
nested, resulting in material savings. Cut part tolerances are very small,
simplifying the task of fitting up for welding.
Although aluminium up to 450mm in thickness can be cut using the
process, the limitations with water jet cutting are the cutting speed, which