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| Marking: The generic term for making some
kind of readable marking on the surface of a thing. Marks are technically
one of the following kinds of effects: engraving, ablation, annealing,
color change or foaming. |
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| Micromachining: Another generic term used
to describe marking on the surface of a target where the purpose of
the mark is not to make a part number or logo or other readable mark,
but to engrave a pattern for mechanical reasons. These reasons may include
liquid conduits through a metal block, antennae patterns on metal parts,
etc. |
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| The actual processes are called: |
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| Engraving, light: Probably the most common kind of laser
marking is engraving. This is where the laser beam is used to remove
material from the surface of the device being marked, but the material
is homogeneous. The laser acts like a chisel in this case and blows
away pieces of the subject material. Light engraving is where a relatively
shallow trench is created, between .0001” and .005”. The
depth achievable depends on the material, the power of the laser and
the dwell time of the laser. |
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| Ablation: This is where one material is removed by laser
from the top of another, dissimilar material. Common example are “Day/Night” lighted
switches in automobiles. These are commonly translucent white plastic
bodies which are dipped in paint. The paint is then selectively burned
off to expose some pattern or symbol which appears white during the
day and which is illuminated from the rear at night. |
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| Annealing: Annealing is a heating process used on steel
and titanium alloys where the surface of the material is selectively
heated with the laser to near the melting point. This has the effect
of discoloring the material to a black color, which gives excellent
contrast against the surrounding steel. This process when properly done
does not remove material. It is very commonly used for surgical tools
and implants where there is high contrast and permanence and no trenches
or crevices are created for bacteria, etc., to hide. Annealing has the
disadvantage that if the material is exposed to extreme heat the annealed
mark will disappear. Also, annealing only works on steels and titaniums. |
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Polishing: Similar to annealing is polishing.
In polishing, the laser beam is used to selectively melt the very top
few molecules of material, and when it cools, which is usually instantaneously,
the surface finish will appear different from the surrounding finish.
This will then reflect light differently and while there is no real
color change, it will appear different. This is often used in electronics
for nickel and gold packages. |
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| Color
Change: Color change is a process
in plastic where the color of the material changes under the laser light.
Some plastics do this naturally, and others have additives which absorb
specific laser wavelengths in order to achieve this effect. Typically,
no material, or a trivial amount of material, is removed from the surface
of the target. One of the classic examples, photos of which can be found
on nearly every laser website in the world, is marking on ear tags for
cattle. Many consumer electronics products have this kind of marking
on their cases. |
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| Engraving,
deep: Deep engraving is something that only high power lasers can do. Deep engraving is used
for making molds and dies, stamps, etc. The depth that can be achieved
is entirely dependent on how the material absorbs the laser, how much
energy the laser has, and how long the laser can dwell on the target.
Deep engraving is usually a pretty slow process. |
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| Deposition: Commercially-available
ceramic paints and films can be applied to the surface of a material
and then melted in place with a laser beam, leaving behind a raised
and very permanent laser mark. Often used with decorative glass items.
Somewhat labor-intensive process to apply the material and then remove
the excess. Also can be expensive. However, the mark can be very attractive
when done properly. |
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| Welding: Lasers can be used
to create weld joints in many materials, including metals, plastics,
and certain ceramics. Typically, weld lasers are higher power and are
used in systems where the laser beam is stationary and the product moves
underneath the laser, not unlike a milling machine. |
Cutting: Lasers can be used to
cut certain materials. Very thin materials (up to a few thousandths
thick) can be cut by normal marking lasers, although some materials
exhibit unsightly heat-effect zones on the material. Thicker materials
can be cut with higher power lasers, and sheet steel, fabrics, fiberboards,
etc., are all cut in industrial situations with lasers. These lasers
can have powers in the many thousands of watts. |
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