Operating Instructions Dplmagic Marker Dplgenesis ... - ACI Laser

Detailed Advanced Information
13.5.2 Marking Methods
Heating Low pulse power densities are used to heat the material surface
without melting or vaporising it. The molecular structures on the
surface are destroyed in this process, which can lead to the material
changing colour.
If the temperatures are high enough, oxidation processes can cause
a colour change and thus create contrasts.
Melting The material melts at higher pulse power densities. After
processing, the molten mass re-solidifies and this may change the
surface structure, e.g. swelling. A contrast is thus created at the
treated places.
Vaporisation If the peak pulse power density is increased still further, vaporisation
processes will occur locally on the material and thus form holes and/
or trenches (depending upon the overlapping parameters). The
trenches thus formed throw shadows which creates a contrast.
Heaping up generally occurs at the edges of the trenches in this
form of marking.
Removal The removal of surface coatings is a special form of laser engraving.
Examples of this are colour removal and the removal of an anodising
layer.
In these cases, the lower-lying layers are exposed. Colour markings
can be created in this way which have very good contrast.
13.5.3 Materials
Metals Metals can be laser marked by all three types of marking described.
Magnetism is a fundamentally different option to the marking results
which can be achieved. Non-magnetic metals such as aluminium,
copper and brass can be engraved by laser. The contrast arises
solely from the shadow formation. A colour change is not possible
with these metals.
Magnetic materials such as steel can of course also be engraved.
Depending upon the carbon content, a
colour reaction is possible, which is produced by an annealing
colour. In practice, inscriptions on steel are often a mixture of laser
engraving and annealing marking.
Surface contamination can affect the marking result. For example,
an oil film leads to an improved annealing marking on steel.
The surface structure has an equally great effect on the marking
result. The absorption on high reflecting surfaces (polished special
steel) is very low. The possible processing speed is correspondingly
reduced.
48 Operating Instructions DPLMagic/Genesis/Nexus Marker - 08/2006