GSI Group - Laser Division
JK300HP/JK300P/JK125P
Pre-installation and User Manual
Issue 2.0
Page 166 of 172
Part No: 1EA300E01
At very high pressures, e.g. ~15bar, cuts free from dross can be produced which require no
further cleaning. Careful optimisation of gas pressure and cutting speed is required to
achieve this condition. It is essential to ensure that the cutting nozzle and gas system are
adequate to handle such high pressures safely.
10.14 Cutting Different Materials
A wide range of metallic materials can be cut successfully using the JK300HP/JK300P/125P
Series Laser.
For processing guidelines, please refer to GSI Group - Laser Division.
10.15 Process Preparation
10.15.1
Choice of Focused Spot Size
High welding and cutting speed is normally desirable from a productivity viewpoint but, in
some applications, the use of short focal length lenses to achieve high speeds can present
problems.
The following factors need to be considered when choosing focused spot size:
10.15.2 Part/Focus
Position
The process tolerance to variations in Laser focus point is a function of the depth of focus,
i.e. the distance above and below the actual focus position over which the focused spot
diameter is approximately constant. The depth of focus is proportional to lens focal length. If
the position of the part is within the depth of focus, the process will be consistent and
reproducible.
If parts cannot be positioned accurately relative to the focus position of the beam because,
for example, part-to-part dimensional variations are significant or low accuracy work handling
is used, then it may be necessary to use a longer focal length focusing lens. This will
increase process tolerance but will limit maximum processing speed.
10.15.3
Weld Shape, Cut Width and Joint Strength
Processing using small focused spot size at high-speed results in production of narrow
welds or cuts of small cross-sectional area.
When welding, this increases the need to ensure accurate alignment of the joint to be
welded and the focused Laser beam. If this is difficult, for example because of part-to-part
variations or low accuracy work handling, a larger spot size may be necessary resulting in
production of a wider weld. This allows a greater tolerance to alignment of the focused beam
with the joint.
When cutting this produces a narrow cut (or kerf) which increases the need to ensure
accurate focused Laser beam alignment with the desired cut path. A wider cut, produced
using a larger focused spot size, may be more tolerant to part alignment.
Additionally, producing a narrow cut can present problems as scrap material, for example
circular slug resulting from cutting a circular aperture, may not drop cleanly away because of
limited clearance. A wider cut produced using a larger focused spot size, would increase
clearance and improve the chances of scrap parts dropping away cleanly.
With overlap and overlap T-welds, the production of a narrow weld results in limited weld
width at the joint interface. For structural overlap welds, it is normally necessary for weld
width at the interface to be greater than the material thickness. To produce a weld of suitable
width, a larger focused spot size may be required at the expense of welding speed.
Petitioners Canadian Solar Inc. and Canadian Solar (USA) Inc.
Ex. 1025, p. 166
