GSI Group - Laser Division
JK300HP/JK300P/JK125P
Issue 2.0 Pre-installation and User Manual
Part No: 1EA300E01 Page 167 of 172
10.15.4 Cover Slide Damage
The use of a short focal length lens is not advisable when welding or cutting materials that
generate high levels of fume and spatter. Fume and spatter can impinge on the Cover Slide
below the Focusing Lens and cause a reduction in Laser beam transmission through it.
Eventually this will result in overheating and fracture of the Cover Slide and possible
irreparable damage to the Focusing Lens.
Materials that may generate high levels of fume and spatter are Zinc coated steels and some
high Magnesium content Aluminium alloys.
10.15.5 Processing Access
Processing access is affected by the choice of focusing lens focal length. The Laser beam
diameter after it has passed through the Recollimating Lens in the Focus Head is constant;
however a short focal length Focusing Lens results in greater focused beam cone angle than
a long focal length Focusing Lens
The greater cone angle can limit beam access that could be a problem when, for example,
welding in the bottom of a groove or between closely packed tubes. In such cases, it may be
necessary to use a longer focal length focusing lens that results in a smaller cone angle.
10.15.6 Finding Focus
Nearly all welding and cutting is carried out with the Laser beam focused on the material
surface. Before setting up a new process, it is important to know the accuracy of the focus
beam position.
The focus beam position is a fixed distance from the end of the Focus Head, i.e. the cover
slide position.
Refer to Section 7.2 for details.
10.15.7 Welding
10.15.7.1 Gas Shielding
When preparing a welding process, it is important to establish a gas shield/gas flow rate that
achieves effective shielding and is reliable for production use. Care in setting up gas
shielding at this point can prevent time consuming and costly problems before production
welding starts.
Because of the wide range of materials/components and different End User requirements,
there are few rules that apply to setting up effective gas shielding.
However, the following points should be considered when setting up gas shielding:
• Turn on shielding gas on prior to initiating a weld in order to purge the gas delivery
system and displace air from the weld region.
• A pipe fitted to deliver shielding gas to the weld must be positioned ahead of the
welding point and arranged to direct shielding gas at the point of beam / material
interaction. Pipe to be angled at ~45º to the surface of the part being welded
• The distance from the end of the pipe to the beam material interaction point must be
far enough to prevent the pipe being damaged by heat from the process but close
enough to ensure good coverage of the weld. Normally, a distance of 10-20mm is
suitable.
• Gas flow rate should be adjusted to the minimum value necessary to achieve the
required shielding effect. Normally the requirement is to prevent visible oxidation of the
surface, i.e. to produce a bright, shiny weld topbead. This is achievable with flow rates
Petitioners Canadian Solar Inc. and Canadian Solar (USA) Inc.
Ex. 1025, p. 167
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