Tech Briefs Magazine - March 2021 - PIT-7

Figure 4. The Coherent LME-RM is a compact, turnkey marking system that can be configured with a
variety of different laser sources and options.

to the material. These lasers are available with infrared, green or ultraviolet
(UV) output to match them to specific
material absorption characteristics. This
same advantage (minimal heat affected
area) also makes the solid-state laser the
best choice for day & night marking,
even though it is actually an ablation
process, rather than one in which a
color or texture change is induced in
the bulk material (like with foaming).
In practice, producing a day & night
mark typically involves making several
passes with the laser, where each pass
hatches out the mark shape and removes
a small amount of material (total paint
layer thickness is typically 0.0025 " ). And,
there may even be " cleanup " passes at

the end of the process to polish up the
underlying layer that has been revealed
to give it the desired smooth texture and
appearance.
The exact process recipe (number of
passes, laser power, laser pulse repetition
rate) varies depending on the materials
being ablated and the layer thicknesses.
In order to speed development of new
process recipes, the Coherent LME-RM
laser marking system can automatically
run through several different sets of laser
parameters to enable rapid identification
of the optimum settings. Specifically, the
system will automatically produce a grid
of marks, where the laser power varies
between each column, and the laser repetition rate varies between each row, so

Photonics & Imaging Technology, March 2021

that a large number of unique combinations are explored. Then, the operator
examines the grid of marks and picks the
settings that produced the best results.
Plus, the Coherent applications development engineers have established a large
database of existing process recipes that
they can supply to users in order to provide a good starting point for this kind of
optimization.
" Mark quality is our single biggest priority, " notes Keith James, Director,
Strategic Supply Chain and Manufacturing Operations, at Crestron Electronics.
" We wanted to offer customers the
option of marking bitmapped images on
our user interface products, but we had
to first clear a technical hurdle to mark
bitmaps with the same high level of clarity we achieve with text. One way the
Coherent system solves this problem is by
doing an outline around the bitmapped
image after it has hatched out the mark
fill. That eliminates any aliasing or
ragged edges on the mark, and consistently delivers a sharp edge.
" The Coherent Visual Laser Marker
(VLM) software also facilitates the whole
process of producing custom marks, " he
adds. Using it, our dealers can bring up
a keypad layout on their computer
screen, define whatever symbols or
nomenclature their customer requests,
and then simply e-mail all that to our
production order processing plant. Our
internal production personnel can then
produce that mark on the part, and the
VLM software handles all the background tasks necessary to make that
happen with almost no operator intervention. It's an extremely user friendly
environment, which an operator can
learn to use in minutes, so our productivity is very high. "

Conclusion
Day & night marking is widely
employed with many consumer products,
most notably automobiles and computer
keyboards, because it delivers both attractive and functional marks. Advances in
laser-based day & night marking systems
now reduce job setup time and facilitate
the process of translating custom artwork
into an actual mark. This makes the technique readily accessible for even small
volume manufacturers.
This article was written by Robert Boyes,
Market Development Manager, Coherent Inc.
(Santa Clara, CA). For more information,
contact Mr. Boyes at robert.boyes@coherent.com,
or visit http://info.hotims.com/79411-220.
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ToC

http://info.hotims.com/79411-220

Tech Briefs Magazine - March 2021

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