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Industrial Applications of the Laser
The following three applications
other than engraving are perfect for the high powered laser.
Cutting
High-power lasers can be used not only to engrave, but to cut material.
This is done at power levels that allow the laser beam to go all the way
through the piece rather than just hit the surface. The same basic
techniques are used in the fabrication of cut shapes in wood or stacked
fabric in the manufacture of clothes and even metals (plasma cutting).
The removal of toxic gases is often provided by a forced-air “snout”
aimed directly at the laser-cutting area.
Printing
Due to technological advances and vendor mergers, direct laser engraving
of flexo photopolymer plates or sleeves that fit over a mandrel is
attracting attention. Up until now the process has been largely
restricted to wide-web flexo printing of paper or film packaging.
Although direct laser engraving is being introduced, here it competes
with rotary engraving. Regarding the less expensive flexo process, the
technology is being redesigned for smaller formats to allow engraving
flexo plates or sleeves that are mounted on the printing cylinders
themselves.
Narrow and mid-web flexo presses (from 20 to 24 inches wide) are
included, which could encourage manufacturers in self-adhesive label and
packaging converters to use the digital, or filmless, method. With this
process there is no mask, as with direct laser imaging. Instead, a
high-power carbon dioxide laser head removes material. The goal is to
achieve sharp relief images with steep, smooth edges to provide a high
standard of process color reproduction. Only a short water wash and dry
cycle is then needed. This is much less complicated than the post
processing stages for direct laser imaging or conventional flexo
plate-making using photopolymer plates.
Imaging
Direct imaging is done on a plate setter. This involves digital flexo
plates or sleeves on a quickly rotating drum or cylinder. The plate
setter is integrated into a digital prepress workflow that supports
digital proofing. In this filmless process, one of the variables is
achieving the fine, sharp dots needed for screened effects. This
includes process color printing.
The electronically generated image is scanned to a photopolymer plate
material with a thin black layer, called a mask, on the surface. The
infrared laser head, running parallel to the drum axis, removes the mask
to reveal the polymer beneath it. Ultraviolet exposure allows the image
to form through the mask. The rest of the black layer absorbs the
ultraviolet light, which polymerizes the photopolymer where the black
layer has been removed. The exposed digital plate still has to be
processed like a conventional flexo plate with a solvent, although some
water-soluble digital plates are currently being developed.
This technology, in use since 1995, is only now becoming more widely
used around the world because of the availability of more affordable
equipment. According to trade sources, about 650 digital plate setters
have been installed in label, packaging, and trade plate-making houses.
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