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Different methods for laser marking are systematized and discussed in the paper. Today in the practice there are many different methods that could be used to realise high quality on the workpiece of various materials with various shapes. Some materials could be marked only by marking or engraving without special requirements and difficulty, while for other materials one can choose the concrete method about the kind of material, marking type, and the specific needs of the production process and the geometry of detail. This makes it necessary to know, to summarise and systematize in a database all methods for particular lasers and materials, in order to quickly and flexibly respond to the specific needs of each customer by the manufacturies on marking systems. The report studies the specific opportunities and fields of applications of different methods for marking with laser.
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Environment. Technology. Resources, Rezekne, Latvia
Proceedings of the 10th International Scientific and Practical Conference. Volume I, 108-115
ISSN 1691-5402
© Rezekne Higher Education Institution (Rēzeknes Augstskola), Rezekne 2015
DOI: http://dx.doi.org/10.17770/etr2015vol1.221
Laser Marking Methods
Lyubomir Lazov, Hristina Deneva, Pavels Narica
Rezeknes Augstskola, Faculty of Engineering, Institute of Regional Studies (REGI).
Address: Atbrivosanas aleja 90, Rezekne, LV-4601, Latvia.
Abstract. Different methods for laser marking are systematized and discussed in the paper. Today in the practice
there are many different methods that could be used to realise high quality on the workpiece of various materials with
various shapes. Some materials could be marked only by marking or engraving without special requirements and
difficulty, while for other materials one can choose the concrete method about the kind of material, marking type, and
the specific needs of the production process and the geometry of detail. This makes it necessary to know, to summarise
and systematize in a database all methods for particular lasers and materials, in order to quickly and flexibly respond
to the specific needs of each customer by the manufacturies on marking systems. The report studies the specific
opportunities and fields of applications of different methods for marking with laser.
Keywords: laser marking, methods.
I INTRODUCTION
In recent years the process of laser marking is used
to perform automated reading of information plotted
on a given part and written as alphanumeric or coded
as bar and matrix codes of individual components or
products [1, 2, 3, 4]. The marked parts and details
containing coded information which can be read
automatically enable them to be monitored during the
manufactoring process and throughout the supply
chain (fig. 1). It is ideal when looking for service parts
and repairs or putting in a claim, as well as being able
to contribute to accountability and ensuring guarantee.
In many branches of industry the method of „Direct
Marking on the Product” (DPM) is used to allow
identification of the final industrial product.
Ordinarily, the usage of DPM is preferred over other
methods such as labeling of products. However, the
physical characteristics and makeup of the part can
also result in marking issues for manufacturers.
Fig. 1. Laser marking of parts with different codes
Today in automotive and aerospace industries,
mechanical engineering, etc., the most common
technologies used for DPM are laser marking,
continuous ink jet printing, dot peening and
electrochemical etching [5, 6]. When selecting one of
these marking technologies it is necessary to focus on
the type of material, the flexibility of the process, the
financial cost, the process speed, the productivity and
ability to automate the process of marking. In making
a decision on the marking of some product except the
choosing type of code and its content, it is also
important to evaluate and select the best marking
method – view table 1 and table 2.
TABLE 1
A COMPARISON BETWEEN THE DIFFERENT TECHNOLOGIES AND
MATERIALS SUITABLE FOR MARKING
TABLE 2
A COMPARATIVE ANALYSIS BETWEEN MARKING TECHNOLOGIES
BASED ON SEVERAL FACTORS
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109
II LASER MARKING
The process of laser marking is one of the most
widespread industrial applications of lasers. It can be
implemented through different physical processes by
interaction of laser beam with the substrate – fig. 2.
Different types of lasers and optical delivery systems
for transportations, focus locked, and deviation of the
beam are used by laser marking systems to mark
metals, ceramics, glass, plastics, leather, wood and
other different kinds of materials. Laser marking is
mostly in the form of an alphanumeric and 2D Data
Matrix code affixed on the surface of the product,
containing some information about the date of
manufacture, serial number etc. [7, 8, 9, 10].
Fig. 2. Physical processes in laser marking on metals
Laser marking compared with traditional techniques
for marking has not only a higher quality and
flexibility of the process, but also it allows the
introduction of automation and integration within
production process. The main advantages of various
types of laser techniques for marking are [2, 11]:
- durable process;
- non-contact technology;
- precise beam focusing;
- high speed machining;
- high contrast and quality of the treatment;
- high productivity and low operation cost;
- good accessibility, even if the surface is
irregularly shaped;
- easy automation and integration in the
manufacturing process;
- prompt localization of laser energy to the
workpiece;
- high reproducibility;
- environmental technology.
Depending on the absorbed energy and the reaction
time thermal processing is distinguished from cold
treatment (UV).
Photons with high energy (UV) can realize the so-
called "cold treatment", as well as they may cause
some cuts in the material by breaking the chemical
bonds within the organic material, or separate a given
material in some parts, without having a thermal
process in the treatment zone. Laser marking by “cold
processing” is a specific process that implements
material removal without causing any thermal effect
of the areas around cuts, i.e., no thermal damage or
heat deformation, etc. effect. For example, in the
industrial electronics using an excimer laser a material
may be removed by a thin layer deposited on a
backing of semiconductor matter.
The thermal method is based on the absorption of
electromagnetic energy of the laser radiation from the
sample surface and its transformation into thermal
energy. The temperature in the treatment zone is
increased and it is possible to realize physical
processes such as heating, melting, vaporization, etc.
in the area of the marking. As a result of the
interaction marking can be achieved by layers
deposited on the base material as well as the surface.
The thermal laser processing for marking is divided
into two groups - laser marking and laser engraving:
Laser marking?
"Laser marking" means a marking or labeling of
details and materials with a laser beam. In this respect,
there are various processes of implementation, such as
removing of substance, coloring, annealing, foaming,
etc. Depending on the material and requirement for
the quality, each of these procedures has its own
advantages and disadvantages.
Laser engraving?
During laser engraving, the surface of the
workpiece is melted and evaporated. Therefore, the
laser beam removes the material. So the result
obtained on the surface is the "engraving".
III TYPES OF LASER MARKING
There are several ways of the realization of laser
marking on the surface of products: Raster Marking,
Vector Marking and Marking using a Mask.
A. Raster Marking
The principle is similar to a dot matrix printer, with
the particularity that here the working tool is the laser
beam (fig. 3). The raster marking is primarily used in
cases where it is necessary to affix mainly textual
information at high speed. Rarely, it is used for
drawing images (photos/logos), i.e., where there is no
need for high quality and high volume of information.
Fig. 3. Raster marking
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B. Vector Marking
This is the most widespread method of laser
marking. This is the most flexible method for marking
with which various applications almost anywhere in
the industry that require making of numerical codes,
bar codes, 2D codes, logos and almost any other kind
of a desirable marking can be realized. The beam is
focused onto the workpiece via an optical system
(lenses and mirrors), whose management is controlled
by a sophisticated computer program. Using special
software, a computer controls mirrors of the
galvanometer. The marking is made by directing the
beam in directions x and y onto the working area (fig.
4). The beam deflection method can transmit a high
density of information. The position of the laser beam
and its focus can be changed in order to implement
exactly the preset image without distortions or
deviations. In accordance to the needs of the user, the
new image is started easily by the software and the
passing to marking can take away only some seconds.
The most commonly used lasers for this method are in
continuous mode.
Fig. 4 Vector marking
Methods a) and b) can be implemented successfully
as well as systems of plotter and such incorporating
scanner fig. 5.
Fig.5. a) plotter system b) scanner system
A. Projection Marking Using a Mask
A laser beam passes through a mask (template). The
beam is designed by an optical system on the working
area – fig. 6. The method allows the mask to be used
repeatedly, thereby the processing parameters are not
changed. Receiving time of the image is very short
because it works in pulsed mode of the laser.
Disadvantage of the projection method is that for each
new task a new mask has to be prepared, i.e., lacking
flexibility; more time and resources to make new
mask are necessary; time lost on another selection of
appropriate technological parameters.
Fig. 6. Projection marking
Comparing the three marking types, it is concluded
that:
marking speed: the projection method for marking
using mask is the highest-speed – per second up to
several tens of marks. This is due to the fact that
marking is made in pulse mode as the duration of laser
pulses is within the range of microsecond μs to
nanosecond ns. During the marking it is not necessary
to stop the movement of the specimen.
working area: A) and B) methods provide
significantly bigger working area of the marking. By
mask marking the marking area is very small because
the diameter of beam spot is with limited sizes, as well
as the energy per pulse on the mask is restricted, too.
flexibility: for the projection method to produce each
new mark a new mask is required. The production of a
mask requires a lot of time. Therefore, the projection
method is more suitable for manufacturing of large
series without any change in the patterns. In beam
deflected marking, the patterns are produced by
software. Thus, it is highly flexible to change patterns.
investment cost: investments for the realization of
the methods A) and B) are higher, as the system for
scanning and deflection of the beam is more
expensive.
IV MARKING METHODS IN LASER MARKING
TECHNOLOGIES
The marking processes include one or a
combination of the following:
• forming a channel with a smallish depth into the
material by evaporation;
• a modification of the surface by melting and a
subsequent solidification;
• changing the colors in the material;
• physical modification of the layers piled on the
material surface;
• etc.
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111
REMOVING THE SURFACE LAYER
During the impact, the laser beam removes the
coatings previously insisted onto the substrate (fig. 7).
As a result, contrast is obtained between the substrate
and the colors of the coating. Most often used
materials to be plotted onto the surface are: special
foils, films, laminates, anodized aluminum or coating
of other metals.
Fig. 7. A schema of removing the surface layer
LASER ENGRAVING
For implementation of laser engraving it is
necessary for material to absorb a larger amount of
energy in the zone of the processing than when
implementing laser marking. Removal of material by
evaporation occurs in the process. With this method,
engraved channel is obtained in the specimen (fig. 8)
similar to that which arises as a marking in the method
of the electrochemical etching. The main advantage of
this laser marking method is that it can be done at high
speed. Although this method appears to be the most
vigorous laser marking technique, it can not be seen
coloring the treatment zone as a result of the
interaction. Like laser etching, direct laser engraving
can be easily determined by touch or low power
microscope (10X) magnification. Laser engraving is
not recommended for use on parts with thickness less
than 2,5 mm.
Fig. 8. A scheme of formation of a channel in the material under the
action of laser radiation
LASER THERMAL BONDING
Laser thermal bonding is a process realized by an
additional material which under the heat influence
generated from laser impact is coupled with the base
material (fig. 9). Fine glass powder or crushed metal
oxides mixed with inorganic pigments or a liquid
carrier (typically water) are primarily used as additive
materials. The pigment can be applied by brush or
sprayed directly onto the surface.
When using laser bonding, it is possible to transfer
the coating to be implemented with a pad printer, a
screen printer or a roller. For this process adhesive
tape with plotting on the additional material is often
used.
Fig.9. Material fused on a surface using the laser thermal bonding
process
LASER SURFACE MODIFICATION
Laser surface modification by melting and diffusion
is done by some material preliminarily deposited onto
the surface (fig. 10). As a result of the impact a new
alloy with other physical and mechanical properties
(e.g. corrosion-resistant and rubbing (wear)) is
generated. The coating materials can be applied with a
brush or sprayed with an atomizer onto the surface, as
the process is realized after the drying of the layer.
Unmarked areas of the coating subsequently are
washed with water or a special cleaning agent. The
marking symbol may be located directly in the
untreated surface or on the laser treatment area. The
process is well done on the surfaces of carbon steel
and aluminum alloys.
Fig. 10. A scheme of laser modifying the material
LASER INDUCED VAPOR DEPOSITION (LIVD)
Laser induced vapor deposition is a patent pending
process that is used to apply for identification
markings, heating and defrosting strips, antennas,
circuitry, and sun shields of gauzy materials. This is
achieved by vaporizing material from a marking zone
under a transparent part using the heat generated from
a laser. The gaseous vapors and droplets resulting
from the heat make condense on the cooler surface to
form a hard uniform coating that is applied in a
prescribed pattern. The process is carried out under
normal conditions without a need for high heat or seal
gas. The marking materials (most metals) used to
produce machine-readable symbols can be formulated
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to be read using optical readers and sensing devices
like X-ray, thermal imaging, ultrasound, magneto-
optic, radar, capacitance, or other similar sensing
means.
The LIVD processes will provide another sure way
to apply machine-readable marking to aerospace parts.
Details of these advanced processes will be reported in
updates to the future.
ANNEALING MARKING / LASER COLORING
Color laser marking is a special kind of laser
etching for metals. The energy absorbed in the impact
zone of the laser beam leads to a process of oxidation
on the material surface.
Fig.11. Marking of a surface using the laser coloration process
The process is used to change the color of metallic
substrate material without burning, melting, or
vaporizing the irradiated material. This is done using a
laser beam with low power that moves slowly across
the surface at a given speed as a result of which the
marking area is changed (fig. 11). In this laser
marking method a high-quality, high-contrast marking
is obtained that does not destroy the surface of the
specimen. A colored laser marking penetrates in deep
surface roughness and allows the process to be
implemented at levels of unevenness to 12,7 μm.
Laser color marking causes less damage to the surface
in comparison with other methods and does not lead to
corrosion of the surface and therefore it can be used
for the marking of some stainless steel. These effects
can be minimized or eliminated by careful selection of
the parameters of the laser marking. This method of
marking cannot be removed by rubbing the surface
with fingers and can be successfully seen at a
magnification less than ten (10X).
LASER ETCHING
The method of laser etching is similar to that of the
laser coloring excluding that energy absorbed by the
surface is sufficient here to implement the process of
melting in the work area. The advantage of using this
technique is that the marking process can be
implemented at high speed since it is not realized to a
great depth in the preparation of the colored image.
Excellent results can be obtained at the depths of
penetration less than 25 μm. This technique, however,
should not be used in some cases for metals because
the cracks resulting from the cooling of the melt may
be disseminated on surface of the basic material that
can prove critical for a safe exploitation of certain
details. These cracks can be extended into the
material, by subjecting it to repeated cycles of
heating/cooling. In such modes of operation of this
method, the details to the marking are not preferable.
GAS ASSISTED LASER ETCH (GALE)
Laser marking that takes place in a normal
environment often has no better contrast, i.e., the
difference between the engraved mark and
background of the substrate is not large. This often
makes it necessary to increase the time for marking
(impact) and also may result in the limitation of the
various materials that can be marked. Laser etching
(GALE) is a technique that uses an auxiliary gas, i.e.,
the marking is carried out in the presence of an
appropriate gas environment, thereby improving the
contrast and increasing readability. The mark is done
at lower values of laser power, i.e., marking on the
material is realized with minimal laser treatment.
GALE method achieves this through the use of an
auxiliary gas that reacts with the material under the
laser impact. A mark is prepared which is a different
color from the background – fig. 12. The auxiliary
gases might be reductive, oxidizing or even inert, such
as their choice being dependent upon the target
material. Contrasting surface results were achieved
through optimization of the parameters of the laser
source, the gas and the material.
Fig. 12. View of gas auxiliary laser etch coating under
magnification (Note that surface protrusions are left intact after
marking) - Tests performed at the University of Tennessee Space
Institute, B. H. Goethert Parkway, Tullahoma, TN 373888
V LASERS FOR THE MARKING PROCESS
Technological schema of a system for laser marking
is shown in fig. 13.
In the process various types of lasers can be used in
systems [12] – see table 3. The most popular laser
sources that are used in the marking technological
systems are: Nd:YAG lamp-pumped lasers, which
produce a light in the near infrared area at a
wavelength of 1064 nm [13], and CO2 lasers - аt the
wavelength 10600 nm.
The wavelength of Nd:YAG lasers – 1064 nm is
absorbed more easily by a vast range of materials.
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CO2 lasers are economically advantageous for
marking on condition that their wavelengths are being
absorbed by the treated materials.
Fig. 13. A general view of the technological system for laser
marking
TABLE 3
SOME LASER SOURCES USED IN THE TECHNOLOGICAL
SYSTEMS FOR MARKING AND ENGRAVING
Type
of laser Wavelength
λ, nm Power P, W
CO2 10600 10÷200 W
6J/pulse when marking
Nd:YAG 1060 25÷10 W, 0.20 J/pulse
when marking
Doubled
Nd:YAG
532 1-3 W
Eximer 175-483 max 2 J/pulse when
marking
Fiber 1062-1064 10 – 20 W
Disc 1062-1064 20-70 W
Excimer lasers also are successfully used in the
laser marking [14,15]. Among all types of lasers, they
shall ensure the highest resolution of the mark. But,
these types of lasers are rarely used due to the low
productivity of the process and the very high cost of
the laser equipment. Recently, diode-pumped fiber
and disc lasers have appeared, which are also
successfully used for the marking process. These
lasers offer high beam quality, excellent stability of
the frequency, and long maintenance intervals
(typically every 12,000 to 15,000 hours without
service).
For any particular application of laser marking
many factors should be taken into account
[16,17,18,19,20,21]:
• power density qS;
• wavelength λ;
• time of impact tproc;
• material properties;
thermal conductivity k
specific heat capacity c
melting temperature Tm
vaporisation temperature Tv
reflectivity R / absorptivity A for the concrete
material, wavelength and temperature.
Power density qS is determined by the amount of
power P generated by the laser divided by the area of
focused beam.
2
4
d
P
qS
, P = Pp τ ν
where: Pp is pulsed power,
τ – duration of time,
ν – pulse frequency,
d – diameter of working spot.
Wavelength, beam divergence and quality of optics
become important factors in determining how small a
focused beam can be on the work surface.
d0 = М2
D
f
4
where: f is the focal length,
D – beam diameter,
М2 – a parameter defining the quality of the
beam
(for fiber laser М2 = 1.1, for disk laser - М2 = 1.2,
i.e., these lasers have almost perfect quality of
radiation, for Nd:YAG laser – М2 = 1.5 ÷ 2 , for CO2-
lasers – М2= 1.5 ÷ 2, for diode lasers – М2 = 10 ÷ 20).
The time of the impact of the laser beam on the
material also has a significant influence on the quality
of marking and the penetration depth (fig. 14).
Fig. 14. Mark-point density vs. pulse rate at various beam velocities
[22].
Sometimes, the pulse duration is a key factor when
choosing a laser which can be used for carrying out a
certain marking.
The reflectivity or absorptivity depends on the kind
of the material, surface state (i.e. smooth or rugged,
polish or oxidized), the wavelength of the laser
radiation and the surface temperature. In general,
metals absorb а larger percentage of the incident laser
power of Nd:YAG lasers (λ = 1064 nm) than that of
CO2 laser (λ = 10600 nm). On the other hand, non-
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metals such as wood, paper, leather, plastics, glass,
etc. absorb the wavelength of the CO2 lasers better.
Some materials, such as silicon successfully absorbs
energy from the both lasers. Laser marking is a
complex technological process. For its implementation
it is necessary to select the appropriate laser.
To evaluate the correct choice of a system for
realizing a specific laser marking the following factors
should be taken into account:
• a system for transportation of laser radiation;
• laser specification;
• system control and software;
• ergonomics - ease of operation;
• recommendations for the manufacturer;
• service guarantee and maintenance;
• the cost.
The laser specifications of different types of lasers
are different. For CW lasers, the basic positions that
should be required in a specification are: wavelength,
average laser power, output power stability, quality
factors of the beam and Q-switch mode (maximum
pulse repetition rate, minimum pulse duration, laser
peak power).
For pulsed lasers, the specifications should include:
wavelength, average power of the laser, maximum
peak power, maximum energy per pulse, pulse
repetition rate, pulse duration, frequency stability, and
quality of the beam.
There are many types of optical delivery systems.
For mask marking processes, the systems can include:
beam expander, homogeniser, CCD camera and
monitor or/and microscope, and project lens. The
project lens, together with the beam size entering it,
determines how big a mark can be obtained per pulse.
For beam deflected marking system, the system may
include beam expander, CCD camera and monitor
or/and microscope, scanner, fiber optics, and lens. The
lens is very important in determining focused spot
size, marking field, minimum marked-line width and
power density on the workpiece.
The scanner together with the marking software
determines the scanning speed.
Control systems and software for different laser
marking systems are very different. The control
system can involve feeding of the workpiece, control
for switching the beam on/off, as well as interfaces for
computers, laser source, stage, and protection/alarm
systems. The marking software must be easy to
introduce into the consumer system and provide
convenient and easy interaction.
VI CONCLUSIONS
An increasing number of companies is interested in
industrial applications of laser technology, primarily
in mechanical engineering, automotive and
electronics. More and more new products that were
made using the laser as one of the most important
tools in their production have appeared in the strongly
competitive global market. Industrial laser
applications, mainly for cutting, welding and marking
are well established techniques.
Currently, among the different types of material
processing that use laser, laser marking is one of those
that found the highest prevalence. It provides a high
quality of marking compared to traditional methods.
Nowadays, lasers are effective as tools for marking
and engraving, as well as their application is
predominate in marking of plastics, metals, alloys,
silicon, ceramics. Laser technology meets the
requirements for speed, quality, flexibility and price.
Some of these qualities are impossible to implement
with traditional technologies.
The need to process materials that have special
characteristics as well as the implementation of the
processes of marking in new fields of industry require
the development and the production of new
technological systems that will meet these
requirements. The progress in the laser equipment and
technology provides users with a wide range of new
options for marking at a rapid pace. At present,
several new lasers are under development; their
appearance will result in lower investment and
operating costs and will improve the quality of
product marking. There are new green lasers being
developed for marking special products such as silicon
wafers, without damaging the base material, and lasers
emitting in the blue and violet ranges of the
electromagnetic waves, such that it would be possible
to significantly reduce the amount of marking sign
with their assistance. This leads to a continuous
development in the sector of laser marking.
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Mittweida 2000, ISSN 1437-7624 N 14, Band K Lasertechnik
S. 192-200
[21] Lazov L., N. Angelov, Investigation of the Impact of the
Number of Repetitions and the Defocus on the Contrast of
Laser Markings for Products Made of Tool Steel,
Metallofizika I Noveishie Tekhnologii, 2012, ISSN 10241809
Vol. 34, 7, pp 1003-1011
[22] Laser Marking, High Performance Thermoplastics LATI,
printed by C&I Italy, 2008 S.5
... Eine zunehmend populäre Technologie zur Herstellung einer dauerhaften, direkten UDIProduktkennzeichnung ist das Laser markierungsverfahren, das auch als Laserglühen bezeichnet wird [5,6]. Diese Methode hat sich als Industriestandard für die Kenn zeichnung von Medizinprodukten etabliert. ...
... Bei metallischen Bautei len wird eine ausreichende Farbstärke bzw. ein ausreichender Kontrast im Vergleich zum Substrat in der Regel durch das Wachs tum einer Oxidschicht oder, wenn das Gerät beschichtet ist, durch Abtragung einer dunkleren Oberflächenschicht erreicht [6]. Bei gepulsten Lasern wird das Ergebnis unabhängig davon, ob Oxida tion oder Ablation praktiziert wird, stark von der Spitzenleis tungsdichte P p (W/m 2 ) beeinflusst. ...
... An increasingly popular technology for producing permanent, di rect UDI product marking is the laser marking method, also re ferred to as laser annealing [5,6]. This method is established as the industry standard marking method for medical devices. ...
Article
Full-text available
The medical device industry demands unique device identification (UDI) tags on metallic components applied via laser marking. A common issue is that the visual appearance of the marking becomes poorly legible over time due to loss of contrast. Nanosecond pulsed laser irradiation was used to grow an oxide layer on two different martensitic stainless steels AISI 420F mod and 420B to compare the influences of the chemical composition of the steel (with and without S), power density, and energy input. The corrosion behavior was found to depend strongly on laser energy input. The presence of sulfur negatively affected the corrosion resistance and narrowed the applicable window for the laser processing parameters significantly. For the sulfur-containing AISI 420F steel, 3‒5 μm wide craters formed on the surface after laser marking, which is interpreted as thermal degradation of protruding MnS inclusions resulting from the laser marking process. Also, substantial cracking in the oxide layer was observed. The marked specimens suffered from corrosion in a thin zone below the formed oxide layer. This behavior is attributed to Cr-depletion in the zone adjacent to the oxide layer, resulting from providing Cr to the growing oxide layer.
... Processing of materials is based on obtaining very high temperatures that can melt or vaporize virtually any material thanks to the great concentration of power and energy in a very small area. A number of laser treatments have been successfully carried out in the textile industry in recent years, such as: marking, 7-10 engraving, [10][11][12][13] cutting, 9,14,15 welding (joining), 16,17 sintering, 15 and other (three-dimensional (3D) scanning, 18,19 laser-based fading, 19 laser ablation, 20,21 conoscopic holography 9 ). ...
... The speed and the power of the laser beam may be higher for engraving than for marking. 22 Laser marking and engraving are applied to various materials: wooden, metal products, leather, textiles, etc. 10 More suitable for organic materials are carbon dioxide (CO 2 ) Laser Marking Systems. Marking is carried out both on stationary products and on the fly in the production line. ...
... 5,54,55 Diameter of minimum focal spot -d f Тhe laser beam focuses on the treated surface in a spot of a certain diameter, called the minimum focal spot diameter d f , with the focal optics (lenses or mirrors) for each laser system. It depends on the wavelengthλ, the diameter of the beam -D, the focal length -f, the beam propagation ratio -M 2 and is calculated from the equation (15) 5,10,40,56 : ...
Article
Full-text available
A number of laser treatments in the textile industry such as: marking, engraving, cutting, welding, sintering, threedimensional scanning, and others, have been successfully applied in recent years. Laser technologies are ones that may be used for decorative or identification marking of products, precise cutting, quality joining by welding both traditional materials and newly developed ones. The use of laser systems for processing of materials, in particular, textile polymers, increases due to the speed, accuracy, and flexibility of this innovative technology. The factors exerting impact over, the laser processing of natural and synthetic textile materials are a lot. They are encountered in certain connections and relationships to each other and affect, to a greater or lesser extent, the quality of the laser processing. The process may be optimized by selecting and managing the most significant factors. Most of them are presented and analyzed in this article aimed at understanding the physical nature of these processes. The factors, which exert the greatest impact on the technological process for laser treatments of textile materials, are indicated.
... The main advantages of various types of laser marking are (Lazov, Narica, Deneva, 2015): ...
... From point of view of marking machine there are 2 types of marking principles. Each type is used in appropriate application (Lazov, Narica & Deneva, 2015). ...
Conference Paper
Full-text available
Today fiber laser is widely used due to their performances and flexibility. They replace old types of lasers in the industrial machines. To develop a family of laser machines it is the need of having standard laser source that could efficiently be used and replaced in the equipment, independently of the laser source or types of lasers. This paper presents the concept and development of a new fiber laser control unit developed to be used for CW, QCW or pulsed regime. Control unit could be used in multiple laser source and satisfy complex requirements. The control unit of the fiber laser source is able to be used in a different type of fiber laser like: Yb doped fiber, Erbium fiber, thulium fiber. Control unit is designed to be used direct or with minimum modifications in different laser processing applications like: marking, engraving, cutting, drilling, welding, etc. Main parameters of control unit are: 3 working regime, frequency-1 KHz (QCW), frequency in pulsed regime : 15KHZ-500 KHz, control seed laser, control pre amplifier and amplifier. Control unit allows commands for machine control: start/stop, interlock, system ready/ fault.
... Marking is part of mass production, and the speed of the product often cannot be followed with the naked eye, and also, sometimes all the products have to be marked with an individual marker. Polymers can be marked with a laser with one of the following mechanisms: ablation, bleaching (thermal bleaching) [1], carbonisation [2], colour change (colour-formation, colouring, colour marking [3,4]), darkening/whitening [5,6], dehydration [7], doping [8,9], engraving [10], foaming [8,[11][12][13], melting, optical breakdown [14], oxidation/reduction on metallized surfaces [15], transfer and unzipping [16,17]. Laser beam can make pits and rims [18], craters [19], but there are papers in which the same interaction between laser beam and material is called once ablation [20], sometimes etching [21]. ...
... There are practical criteria of choosing the appropriate laser, but the most important characteristic is wavelength. There are lasers from UV to the far infrared, and they can be continuous or high-peak power, short-duration pulsed laser beams [11]. The most common lasers for automotive cable marking include the following: - CO 2 gas laser with 10 640 nm wavelength (far-infrared); it is used also for thermosetting polymers [60], - Xenon chloride (XeCl) excimer gas laser with a wavelength of 308 nm (UV), - Nd:YAG solid-state laser with a wavelength of 1064 nm (near-infrared), - Ytterbium fibre laser with a wavelength of 1060 nm (near-infrared), - Frequency-doubled Nd:YVO 4 , 532 nm wavelength (visible, green), - Frequency-tripled Nd:YVO 4 or Nd:YAG solidstate laser with a wavelength of 355 nm (UV). ...
Article
Full-text available
This article describes the test results for laser markability of automotive electrical cables. The insulation is PVC, but the colour and construction of the insulations are different. Two types of laser workstations were used, one with a wavelength of 1064 nm and another with 532 nm. The penetration depth of the laser beam was determined by optical microscopy on cross sections. The 1064 nm laser beam can mark all investigated materials with good contrast, except the yellow insulation. The 532 nm laser beam with fast speed can hardly produce contrast with any of the materials. The laser markability of the yellow insulation was found to be the most problematic. On the two-layer insulation, despite the whitening of the inner material, dark marking is produced because the heat developing on the interface of the two layers will heat up and carbonize the transparent layer.
Article
Full-text available
In this study, we investigated the effect of CO 2 laser energy on the surface of a variety of polyester textiles with thicknesses ranging from 2 to 3mm. To evaluate the laser action on the surface texture of this type of textile, the laser power was changed from 80 W to 120 W. A series of SEM images were taken with various incident laser powers. The rate of engraving operations increases as the incident laser power increases, and it is dependent on the thickness, chemical, and physical features of the irradiated fabric. According to the results of engraving samples. SEM photos demonstrate that laser treatment causes etching in all treated fabrics, even at a low incident laser power of 80W. In the marking, engraving, cutting, and welding processes, the CO 2 laser system is a suitable laser system for surface treating synthetic textile materials.
Conference Paper
The aim of this study was to investigate the microstructure and micromechanical properties of pulsed laser irradiated stainless steel. Laser marking was performed for AISI 304 stainless steel samples using a Nd:YAG fiber laser (1064 nm). AISI 304 steel finds applications in a variety of industries due to its excellent properties: Automotive and aerospace components; Heat exchangers; Kitchen sinks, consumer durables; Chemical containers, including for transport; Food processing equipment, particularly in beer brewing, milk processing, and wine making; Fasteners and flanges manufacturing; Architectural applications such as roofing and cladding, doors and windows. The influence of the process parameters such as pulse repetition frequency and scanning speed at different topology of the surface treatment is considered. The microstructures of the obtained samples were analyzed using confocal optical microscopy (COM). For each square, the roughness of the marking was determined using specialized software and an established methodology. The roughness was measured repeatedly and the mean value for each square was determined together with the root mean square error. Graphs of the dependence of the roughness on the speed and the raster step were obtained. From them, the rate of change of roughness for different intervals of speed and raster step was calculated. Optimal operating intervals of speed and raster beam were determined for the studied steel and this type of laser.
Article
The study is about the process of laser marking by melting products made of carbon structural steel 15Cr2 with wide application in industry. A fibre laser operating in the near-infrared region was used to perform the experiments. A raster marking method was used by varying the power density of the laser radiation and the frequency of pulses repetition. For each marked area, the contrast is determined by measuring the saturation of the marked area and the background by the greyscale. Graphs of the dependence of the contrast on the power density for three marking speeds and on the contrast on the frequency for two marking speeds are analysed. The work intervals for the power density and frequency for this steel and fibre laser, are determined.
Article
Full-text available
The article is devoted to the technological process modeling of marking on the surface of metal products using a pulsed laser. The described mathematical model allows us to select the optimal technological parameters of the laser marking complex in order to form the desired marking symbols on the surface of steel and alloy products with various chemical compositions, taking into account the physical properties of the marked material. The developed technological regimes have been tested and recommended for industrial applications in various industries, such as engineering, automotive, aircraft manufacturing and railway transport, as well as for the widespread usage of marking serial products from metal materials.
Article
Full-text available
Special consideration is given to parameters affecting the contrast of laser marking on tool steel products, and relevant experimental results are reported and related to determining the critical density of laser radiation power in melting and evaporation of tool steel Y7 and P6M5. The dependence of contrast from marking speed and power density is also presented. The results refer to fibre lasers operating in pulsed mode with a wavelength in the near infrared region. Dependences of contrast marking of speed and power density are also presented. Optimal intervals for these variables in laser marking by melting are obtained. The results obtained will be a useful aid to the operators of laser technology systems for marking as they contribute to considerable reduction of set up time in real manufacturing settings.
Article
Full-text available
A given paper examines the impact of defocus and number of repetitions in raster laser marking for samples of carbon tool steels. Experimental results are carried out in single and double marking with twice of the speed with fibre laser of X= 1.06 (im. The role of change of the absorption capacity after initial crawl along the selected edge of the mark is reported. The influence of contrast in defocus on its change in +/- directions is investigated. The role of focal distance for mark quality is analyzed too. For this purpose, experiments are provided with two lenses with focal distance of 160 mm and 254 mm.
Article
Full-text available
An investigation has been made of dependence of marking contrast on surface roughness, spacing between hatches (that is the pitch between hatches) and the speed for products made of tool steel. Experiments made concern pulse laser CuBr utilizing МОРА system.
Article
In this paper, the Nd:YAG laser engraving system is studied for the purpose of engraving image, figure, and characters on the surface of metal, ceramic, plastic, leather, etc. First of all, the high repetition and high power Nd:YAG laser is set up; secondly, the 2-mirror 2-axis optic scan system is analyzed and designed; third, the software is developed to control the laser beam in vector mode or in dot matrix mode. The expanded laser beam is directed toward the worksurface through a f-(theta) lens by computer controlled X and Y axis mirror, and moves in a fixed path, a mark is engraved or marked. As a result, the marking field of 100 X 100mm and spot size of 0.088mm are obtained.
Article
In this work, the technical aspects of laser marking using organo-metallic films of different compositions are reported. Orasols of different types and palladium (II) acetate are used, for the first time, to produce permanent markings of various colors on different substrates. Ceramic and plastic substrates were used. The deposition process is a photothermal process and the markings were carried out using an argon ion laser operating at λ = 514 nm. Two laser marking techniques are used with the orasol dyes and palladium (II) acetate. The first of these two techniques is mask marking, where laser light is projected onto a workpiece through a mask replicating the information to be marked. The second technique applied is real-time motion marking. The workpiece was translated under the stationary laser beam using a programmable stage translator. For both techniques, optimum marking parameters (scanning speed/exposure time, power, and deposited line width) are reported along with typical examples.
Article
In this paper, the CIE color difference formula was applied to evaluate four types of material surfaces; anodized aluminium, stainless steel, poly-butylene tetra-phthalate (PBT), and phenol formaldehyde, marked using a Nd:YAG laser, and viewed under three common modes of illumination; tungsten, fluorescent and daylight. The color difference values were based on the spectral reflectance readings obtained from a spectrophotometer. Each material exhibited different color difference trends in relation to marking speed for the different modes of illumination. Nevertheless, general comparisons could be made in terms of operational marking speeds and the maximal color difference values for each material.
Article
A Q-switched Nd:YAG laser was used in the laser marking process of stainless steel. The influence of the pulse frequency of the laser beam on the mark depth, width and mark contrast have been studied in this paper. The mark contrast is the ratio of the apparent brightness between the mark and unmarked areas which shows the clearance degree of the mark. An optical microscope, scanning electron microscope and surface profile instrument were used to measure the effects of pulse frequency on the mark depth and width. An image-analysis system with a frame-grabber card and a charged-couple-device (CCD) was used to measure mark contrast. It has been found that the mark depth, width and mark contrast depend on the interaction process of the laser beam and the material, which was influenced dramatically by the pulse frequency. The pulse frequency of the laser has a significant effect on the mark quality. There is maximum mark depth when the pulse frequency is about 3kHz, while mark width almost keeps constant at different pulse frequency. With the pulse frequency increasing, evaporation of material becomes less, and at the same time oxidization becomes more significant, which leads to the improvement of mark contrast. The highest mark contrast could be obtained when the pulse frequency of laser was about 8kHz.
Article
With the invention of the laser came a new form of industrial energy, optical energy, available for the first time in large and controllable quantities. This article reviews the characteristics of this new form of industrial power and how it is being used in material processing from cutting to cleaning. The article also highlights some of the more exciting recent developments.
Article
Bibliogr. na konci kapitol
Лазерная маркировка материалов, Научнотехнический журнал Фотоника, выпуск № 3
  • А Валиулин
  • С Горный
  • Ю Гречко
  • М Патров
  • К Юдин
  • В Юревич
Валиулин А., С.Горный, Ю.Гречко, М.Патров, К.Юдин, В.Юревич, Лазерная маркировка материалов, Научнотехнический журнал Фотоника, выпуск № 3/2007, с.16-22