EN 1011-6:2005

SLOVENSKI STANDARD
01-marec-2006
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Welding - Recommendation for welding of metallic materials - Part 6: Laser beam
welding
Schweißen - Empfehlungen zum Schweißen metallischer Werkstoffen - Teil 6:
Laserstrahlschweißen
Soudage - Recommandations pour le soudage des matériaux métalliques - Partie 6:
Soudage par faisceau laser
Ta slovenski standard je istoveten z: EN 1011-6:2005
ICS:
25.160.10 Varilni postopki in varjenje Welding processes
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 1011-6
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2005
ICS 25.160.10
English Version
Welding - Recommendation for welding of metallic materials -
Part 6: Laser beam welding
Soudage - Recommandations pour le soudage des Schweißen - Empfehlungen zum Schweißen metallischer
matériaux métalliques - Partie 6: Soudage par faisceau Werkstoffen - Teil 6: Laserstrahlschweißen
laser
This European Standard was approved by CEN on 28 November 2005.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
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Slovenia, Spain, Sweden, Switzerland and United Kingdom.
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© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 1011-6:2005: E
worldwide for CEN national Members.

Contents Page
1 Scope .6
2 Normative references .6
3 Terms and definitions.6
4 Health and safety and protection of the environment.6
5 Quality requirements .6
6 Equipment .7
6.1 General .7
6.2 Provisions for acceptance testing.7
6.3 Provisions for maintenance and calibration.7
7 Qualification of welding personnel.7
8 Welding procedure specification.8
9 Welding procedure test .8
10 Consumables .8
10.1 Filler metals.8
10.2 Gases .8
11 Design.9
11.1 Overall design of structure or product.9
11.2 Joint design.9
11.3 Joint preparation.9
12 Laser beam welding.10
12.1 Characteristics .10
12.2 Advantages and limitations.12
12.3 Assembling and fixtures .13
12.4 Process control.13
12.5 Inspection and testing .13
12.6 Imperfections .13
Annex A (informative) Equipment .14
A.1 Description of laser process.14
A.2 Laser beam sources .15
A.3 Guiding, shaping and focusing the beam .17
A.4 Devices used to create a relative movement between the laser beam and the work piece .21
A.5 Fixtures used to hold the work piece .22
A.6 Cooling systems .22
A.7 Control systems.22
Annex B (informative) Laser beam properties.23
Annex C (informative) Information about weldability of metallic materials .25
C.1 General .25

C.2 Steels and iron alloys .25
C.3 Nickel alloys .26
C.4 Aluminium and magnesium alloys .27
C.5 Copper and its alloys.27
C.6 Refractory and reactive metals .27
C.7 Titanium and its alloys .27
C.8 Dissimilar metals.28
C.9 Non-metals .28
Annex D (informative) Information about causes of weld imperfections and prevention.29
Annex E (informative) Beam control and monitoring .31
E.1 General .31
E.2 Focus point.31
E.3 Beam alignment and pilot beam coincidence.31

E.4 Beam power.32
E.5 Beam power distribution .32
E.6 Nozzle alignment.32
E.7 Pulsed beam power data .33
E.8 Manipulators, guides etc. .33
Annex F (informative) Laser beam processing .34
F.1 Laser beam cutting .34
F.2 Laser beam drilling .35
F.3 Laser beam surface treatment .36

F.4 Laser beam cladding characteristics .37
F.5 Laser beam marking and engraving.37

Foreword
This European Standard (EN 1011-6:2005) has been prepared by Technical Committee CEN/TC 121
“Welding”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by June 2006, and conflicting national standards shall be withdrawn at
the latest by June 2006.
This standard is composed of the following parts:
 Part 1: General guidance for arc welding;
 Part 2: Arc welding of ferritic steels;
 Part 3: Arc welding of stainless steels;
 Part 4: Arc welding of aluminium and aluminium alloys;
 Part 5: Welding of clad steel;
 Part 6: Laser beam welding;
 Part 7: Electron beam welding;
 Part 8: Welding of cast irons (prepared by CEN/TC 190).
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland
and United Kingdom.
Introduction
This standard is being issued in several parts in order that it can be extended to cover the different types of
metallic materials that will be produced to all European Standards for weldable metallic materials.
When this European Standard is referenced for contractual purposes the ordering authority or contracting
parties should state the need for compliance with the relevant parts of this standard and such other annexes
as are appropriate.
This European Standard gives general guidance for the satisfactory production and control of welding and
associated processes and details of some of the possible detrimental phenomena that can occur, with advice
on methods by which they can be avoided. It is generally applicable to laser beam processing of metallic
materials and also to some extent for non-metallic materials. It is appropriate regardless of the type of
fabrication involved, although the relevant product standard, structural code or the design specification can
have additional requirements. Permissible design stresses, methods of testing and inspection levels are not
included because they depend on the service conditions of the fabrication. These details should be obtained
from the relevant application standard or by agreement between the contracting parties.
It has been assumed in the drafting of the standard that the execution of its provisions is entrusted to
appropriately qualified, experienced and trained personnel.
1 Scope
This European Standard gives general guidance for laser beam welding and associated processes of metallic
materials in all forms of product (e.g. cast, wrought, extruded, forged).
NOTE Some guidance on laser beam cutting, drilling, surface treatment and cladding is given in Annex F.
2 Normative references
The following referenced documents are indispensable for the application of this European Standard. For
dated references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN ISO 3834-2, Quality requirements for fusion welding of metallic materials — Part 2: Comprehensive quality
requirements (ISO 3834-2:2005)
EN ISO 3834-5, Quality requirements for fusion welding of metallic materials - Part 5: Documents with which it
is necessary to confirm to claim conformity to the quality requirements of ISO 3834-2, ISO 3834-3 or ISO
3834-4 (ISO 3834-5:2005)
EN ISO 11145:2001, Optics and optical instruments — Lasers and laser-related equipment — Vocabulary and
symbols (ISO 11145:2001)
EN ISO 15609-4, Specification and qualification of welding procedures for metallic materials — Welding
procedure specification — Part 4: Laser beam welding (ISO 15609-4:2004)
3 Terms and definitions
For the purposes of this European Standard, the terms and definitions given in EN ISO 11145:2001 apply.
4 Health and safety and protection of the environment
A general checklist on protection of the environment in welding and allied processes is in preparation by
CEN/TC 121. It will cover laser applications.
Laser beam processing introduces additional hazards over and above those normally experienced in arc
welding. Specialist advice should be sought, see e.g. EN 60825-1 and EN ISO 11553-1.
Guidance for safety aspects related to the application of industrial robots for manipulation of the focussing
devices and/or the components to be welded can be found in EN 775.
5 Quality requirements
Laser beam welding is a complex process needing detailed process control. All processing is performed under
numerical control necessitating programming of each single operation. The application has to be controlled at
a level compatible with EN ISO 3834-2 and EN ISO 3834-5.
NOTE This does not entail a requirement for certification but the process control should operate in accordance with
EN ISO 3834-2 and EN ISO 3834-5.
It is a condition for efficient process control that quality requirements for joint geometry and other relevant
requirements have been specified prior to start of fabrication. A number of European Standards specify joint
geometry and relevant quality criteria and can be used for reference, as appropriate:
Table 1 — Quality criteria
Requirements and tolerances Standard no.
Quality requirements to beam welded joints EN ISO 13919-1
EN ISO 13919-2
Quality requirements for cut surfaces EN ISO 9013
General tolerances EN ISO 13920
General requirements EN ISO 3834-2 and EN ISO 3834-5 specify provisions for information
and items to be agreed and specified prior to the start of fabrication.
EN 1011-1:1998, Annex A can be used as a guide in case
EN ISO 3834-2 and EN ISO 3834-5 are not called for.

6 Equipment
6.1 General
Information about particular equipment for laser beam processing has to be found in information from the
supplier. A number of textbooks and a large number of articles provide background information. Annex A
provides some very general information on principles and techniques. Annex B provides general information
on the properties of laser beams.
6.2 Provisions for acceptance testing
Provisions for acceptance of laser beam equipment are found in the following standards, see Table 2.
Table 2 — Provisions for acceptance testing
Type of equipment Standard no.
CO laser beam equipment EN ISO 15616-1, EN ISO 15616-2 and/or EN ISO 15616-3
Nd:YAG laser equipment EN ISO 22827-1, EN ISO 22827-2

6.3 Provisions for maintenance and calibration
Provisions for maintenance are not standardised. The supplier's manuals have to be consulted. Principles for
calibration, verification and validation and minimum requirements are specified in EN ISO 17662.
7 Qualification of welding personnel
The requirements for the qualification of personnel for fully mechanised and automatic welding and allied
processes are laid down in EN 1418. Among the different procedures specified in this European Standard, the
functional test is particularly suitable as a basis for qualification of personnel responsible for the operation and
set-up of laser beam processing. In a functional test, the operator or setter demonstrates his/her knowledge of
working with a procedure specification and of setting, supervising and checking the laser beam processing
machine.
8 Welding procedure specification
All details for the laser beam welding of components are to be recorded in a welding procedure specification
(WPS) according to EN ISO 15609-4. Procedure specification for cutting, drilling, surface treatment and
cladding are not standardised. EN ISO 15609-4 can, however, give some guidance.
9 Welding procedure test
Formal qualification of all procedures for laser processing is recommended for all applications and required for
many applications. Qualification of procedures for laser beam welding (when required) can be performed by
procedure testing, see EN ISO 15614-11. Qualification by pre-production testing can also be relevant,
however, see EN ISO 15613. Qualification by pre-production testing is common practice for cutting, drilling
and surface treatment. EN ISO 15613 can give some guidance.
Qualification of procedures for laser beam welding for cladding (when required) can be performed by
procedure testing, see prEN ISO 15614-7. Qualification by pre-production testing can also be relevant,
however, see EN ISO 15613.
10 Consumables
10.1 Filler metals
Filler metals are used for laser beam cladding and sometimes for laser beam welding. The main problem in
regard to filler metals for laser applications is that the market for such filler metals is rather small and that
dedicated standards for filler metals for laser applications do not exist. The usual form of delivery is solid
cylindrical wires but powders can also be used, in particular for cladding. What is commercially available is:
 wires marketed as consumables for gas shielded metal arc welding and tungsten inert gas welding.
However, it should be noted that metal cored tubular wires might also be suitable. Small-scale
(experimental) production of tubular wires can even be feasible for special applications. Relevant
standards are EN 440, EN 758, EN 1668, EN 12070, EN 12071, EN 12072, EN 12073, EN 12534,
EN 12535, EN 14640, EN ISO 18273, EN ISO 18274;
 wires marketed as consumables for thermal spraying. The usual form of delivery is solid cylindrical wires
which are standardised in EN ISO 14919;
 powders for thermal spraying are standardised in EN 1274;
 powders for powder metallurgy.
10.2 Gases
Gases are used for shielding and plasma suppressing in laser beam welding, as cutting assists gas in laser
beam cutting, for shielding in laser beam cladding, drilling and marking. Further, CO lasers may need a
continuous supply of laser gas.
The only relevant standard is EN 439. This standard is, however, not adequate for all gases used for laser
beam processing. Careful specification of composition, tolerances etc. is necessary for all non-standardised
gases, when ordering.
11 Design
11.1 Overall design of structure or product
The main consideration is to ensure that all joints are accessible. It can be an advantage that the focussing
head can be some distance from the surface of the joint. However, when shielding gas or plasma suppression
jets are used, these nozzles have to be placed close to the surface. Application of sensors augment the
requirements for accessibility.
11.2 Joint design
Joint design is, of course, relevant for laser beam welding. The default joint is a normal square butt weld in a
butt joint. T joints are welded similarly but full penetration may not be necessary. Overlap joints are used for
spot welding.
Laser beam welding can accomplish welding of components to tight tolerances. It is a condition, however, that
either the fixtures hold the parts very accurately or that the joints are "self-positioning".
Laser beam welding with root backing can be employed if spatter and undercut are to be avoided.
For axial circular welds on components with narrow dimensional tolerances, a press fit like H7/r6 to H7/n6
(EN 20286-2) is recommended. For circular welds with a clearance fit tacking is essential.
11.3 Joint preparation
The quality of laser beam welding relies on accuracy and cleanliness of the joint preparation. Joints can be
prepared by machining or cutting. Attention should be paid to the resulting surface condition. Cleaning of weld
joint surfaces should be carried out if they are contaminated by oxides, oil, grease, coolant and paint.
The specific cleaning method used will be dependent on the material type, component size and the quality
requirements as well as the operational circumstances. The following treatments can be used:
 manual degreasing with a solvent;
 cleaning in a closed solvent vapour unit or in an ultrasonic bath;
 pre-treatment by steam cleaning with a slightly alkaline additive, following by drying;
 acid pickling neutralisation, washing in distilled water, drying, short-term storage;
 mechanical cleaning by grinding, brushing etc.;
 primers and similar layers on steel plates can be burnt away by de-focussing the laser beam and move it
along the joint prior to welding. Very high speeds of in excess of 100 mm/sec can be used during this
treatment.
Where components have surface layers produced by carburising, anodising, cadmium plating, nitriding,
phosphating, galvanising etc. these layers usually have to be removed, preferentially by machining of the
surface in the weld joint region.
If the component cannot be machined in the weld start and finish regions to remove the end crater, run-on or
run-off plates should be used (see Figure 1). These run-on/ run-off plates also suppress heat accumulation at
the work piece ends. The run-on/run-off plates should be attached to the work piece by clamping or welding to
achieve good thermal contact and will be removed subsequently.
Key
1 Run-on plate
2 Work piece
3 Run-off plate
4 Start of weld
5 End of weld
Figure 1 — Work piece with run-on and run-off plate for separating the weld start and weld end
12 Laser beam welding
12.1 Characteristics
12.1.1 Modes
Laser beam welding is a fusion welding process and the joint is characterised by heat affected zones in the
parts, joined by weld metal.
Laser beam welding is often performed as keyhole mode welding. Keyhole mode welding requires a beam
with a high power density, able to vaporise the material at the point of interaction. The beam then is able to
create (by the vapour pressure) a deep cavity, roughly cylindrical in shape. The walls of the cavity are covered
by molten material. When the process is under control, the cavity is propagated with the beam along the joint.
Heat and material propagation is essentially two-dimensional. The material melts at the front of the cavity and
moves to the trailing edge, where it solidifies, creating the weld metal. A small proportion of the material
evaporates or is ejected as spatter and this part of the material is transported in the direction along the axis of
the beam. Keyhole mode welding is the usual mode for full and partial penetration butt welds in thick materials.
Another mode is conduction mode welding. In this mode, the intensity of the beam is insufficient to create a
keyhole and the heat distribution becomes similar to the heat distribution in arc welding. Conduction mode
welding occurs when the beam (of low intensity) is de-focussed or oscillated. Conduction mode welding can
result in a three-dimensional heat distribution and the weld cross section is then approximately circular with a
width at the surface approximately 2 times the depth of penetration. However, the heat input can be spread
over a wider area resulting in a weld with a width larger that 2 times the depth of penetration. A similar
technique is used for laser beam cladding where penetration usually is minimised.
In spot welding, the focussing head is kept stationary in relation to the parent material during welding. Welding
time for each spot can be measured in milliseconds. Pulsed lasers are commonly used for this purpose. The
resulting weld profile is usually intermediate between conduction and keyhole welds.
12.1.2 Energy transfer
The energy is transferred from the laser beam into the base material where it melts the material and creates
the keyhole (in the keyhole mode). Energy transfer is influenced primarily by two factors:
 reflection of (a part of) the beam energy from the surface of the base material and liquid weld material;
 creation of a plume of vaporised elements and/or of a plasma cloud (CO laser).
Laser beams are reflected from the surface of materials. The proportion of the energy reflected depends on
the surface condition (at the microscopic level), e.g. the surface roughness and also the surface temperature.
The proportion reflected can be very high, close to 90 % for polished materials and wavelength above 1 µm at
room temperature. The proportion is much lower, below 50 % for shorter wavelength and less reflective
surfaces. However, if the beam has enough power to establish a keyhole, reflection becomes of minor
importance. Consideration of the reflectivity of the material has become less important with the general
availability of high power and high beam quality lasers. When reflectivity causes problems this can result in
the process becoming unstable and the keyhole not established locally where for some reason a higher
percentage of the beam energy is reflected.
Laser beam welding is usually accompanied by vaporisation of part of the base material. This results in a
plume of vapour above the keyhole. High power CO lasers induce such high temperatures that at least a part
of the plume is ionised and a cloud of plasma is created in and above the joint (the keyhole). The plasma
cloud can attenuate the beam and the usual precaution is to apply a jet of helium, blowing the plasma away.
Helium is the preferred gas for plasma suppression. However, other gases such as N or Ar have been used
on an experimental basis. The plasma cannot be entirely suppressed, but welding appears to be feasible none
the less.
Vaporisation affects the various chemical constituents of the base material selectively. Components with a
high vapour pressure will vaporise more readily. The weld metal will consequently be depleted in such
components compared to the base material.
12.1.3 Pulsed beam welding
Pulsed beam welding can be used for spot welding. The high peak power in pulsed lasers can for certain
applications be used for establishment of keyhole mode welds in comparatively thick materials. However, the
welding speed is less than for a powerful laser having a continuous output.
12.1.4 Beam oscillation
Oscillation of the beam can be used to establish a wider weld profile and can be beneficial where gaps have
to be bridged. The augmented welded cross section is accompanied by diminished cooling rates.
12.1.5 Ramping
The numerical control of laser beam power sources usually permits ramping (slope-up and slope-down) which
– together with focus control – can be used to obtain satisfactory welds in the start and stop positions. This is
of course very important for welding of circumferential and planetary welds.
12.1.6 Beam focussing
The laser beam is usually focussed at or near the surface of the base material.
12.1.7 Gas shielding
Some gas shielding is needed for most applications. The weld pool, the hot part of the weld immediately
behind the weld pool and the underside (for full penetration welding) may have to be protected. Gas nozzles
of a suitable design should be used. The need for shielding and the type of shielding gas to be used depends
on the material welded. Sufficient shielding of all hot parts is of key importance e.g. when welding stainless
steels in order to maintain good resistance to corrosion. Full penetration welds in mild steel can, however,
often be welded without any gas shielding at the weld root. High speed welding of thin materials can also be
carried out without a gas shield.
12.1.8 Use of consumables
Consumables may be needed e.g. when welding with a gap, in order to avoid underfill. Consumables may
also be needed for metallurgical reasons. However, very accurate positioning of the wire is necessary. A
hybrid arc process can be a better solution.
12.1.9 Hybrid processes
Hybrid processes involve a combination of laser beam welding with an arc welding process, plasma arc
welding, TIG welding, MAG welding etc. This can be a good solution when addition of a filler material is
needed. High welding speed and low heat input can still be achieved. Combined butt/fillet weld is another
option when a hybrid process is used. EN 1011-1 can be consulted as regards recommendations for arc
welding.
12.2 Advantages and limitations
Laser beam welding using keyhole mode has a number of advantages compared to other fusion welding
processes:
 joining is established by creation of a minimum of weld metal. This is associated by a minimum of heat
input, narrow heat affected zones and minimal shrinkage and distortion;
 high welding speeds are possible and most joints are established by one or at most two runs, one from
each side;
 welds can be established in materials down to a few hundreds of millimetres thickness. The upper limit is
presently of the order 25 mm for full penetration butt welds in steels welded from one side only.
Compared to electron beam welding, laser beam welding has the advantage of being performed under normal
atmospheric conditions and there is no generation of x-rays.
The limitations are mainly:
 high cooling rates that call for special attention in some materials in order to avoid unacceptable materials
properties;
 cracking and/or porosity can occur in certain materials;
 materials with highly reflective surfaces can be difficult to weld because the beam energy is reflected and
not absorbed;
 present laser beam sources are characterised by a low efficiency. The total energy consumption can be
of the order 10 to 30 times the beam energy;
 manual welding is not very practical. In practice, mechanised equipment has to be used and all
operations pre-programmed;
 weld metal can be depleted in components with a high vapour pressure due to evaporation;
 strict requirements for the quality of joint preparation and accurate positioning of the weld or seam
tracking;
 surface coatings can result in imperfections.
12.3 Assembling and fixtures
All conventional fixtures, manipulators, X-Y tables etc. can be used for laser beam welding. Laser beam
welding does not, in principle, require fixtures different from those used for other welding processes. However,
if the full potential regarding accuracy and close tolerances of the welded components are to be obtained,
fixtures shall have a compatible accuracy. EN ISO 15616-1 to EN ISO 15616-3 give some guidance.
12.4 Process control
Laser beam welding is performed under numerical control. Adjustments or feedback during welding is rarely
possible, except by the use of sensors, which dynamically adjusts the trajectory of the beam in relation to the
work piece. Sensors monitoring the process by observation of e.g. the spectrum and intensity of the
secondary light from the weld area have, however, been installed on an experimental basis.
12.5 Inspection and testing
EN ISO 15614-11 provides references to standards for destructive testing. EN or ISO standards for non-
destructive examination of laser beam welded joints have not yet been established. Standards for examination
of arc welded joints can be used with suitable modifications.
12.6 Imperfections
The terminology for imperfections is defined in EN ISO 6520-1. Quality levels, suitable for process control are
specified in EN ISO 13919-1 to EN ISO 13919-2.
Annex A
(informative)
Equipment
A.1 Description of laser process
A.1.1 Principles
Laser is an acronym of Light Amplification by Stimulated Emission of Radiation. A laser is essentially a device,
which generates a beam of light, which is sufficiently narrow and powerful to be used for welding, cutting,
surface treatment and drilling purposes. A laser can, from one point of view, be considered a black box. The
mechanism generating the beam and the actual design of a particular laser is of interest only to the extent it is
of significance for the daily maintenance, calibration and those repair operations the user is able to perform.
The users' manual (repair manual) for the particular device should then be consulted. However, this point of
view is not realistic due to the fact that there exists a number of different types of lasers and each has
particular characteristics, which limits its applications. A brief description of the various types is a necessity if
for no other reasons than to provide the necessary terminology for the main parts of this standard. However,
several textbooks, papers and other information are available on lasers and users are referred to these
sources for detailed information.
All laser devices include a resonator where the light is generated and amplified. The resonator is established
by reflective and partial-reflective mirrors and other forms for barriers.
Inside the resonator is some medium able to generate light, continuously or pulsed. A proportion of the light
stored in the resonator is permitted to escape, forming the actual laser beam.
Energy is delivered from an outside source into the medium inside the resonator (energy for „pumping“). The
energy is not converted 100 % into the laser beam and the excess energy has to be removed by a cooling
mechanism.
A.1.2 Components
The laser beam source forms only a part of the entire installation. All laser processing involves mechanised,
automatic or robotic installations. The only exception is the hand-held application of low power lasers for
special purposes (non-industrial).
A typical laser installation (workstation) includes typically the following categories of components:
 laser beam source;
 devices for guiding, shaping and focusing the laser beam onto the work piece;
 devices used to create a relative movement between the laser beam and the work piece;
 fixtures used to hold the work piece;
 cooling systems;
 control systems.
A.2 Laser beam sources
A.2.1 CO lasers
Table A.1 — CO lasers
Key properties Characteristics
Stage of technology Carbon dioxide (CO ) lasers have been commercially available for many years
and they represent a reasonably mature technology.
Laser active material in Resonator Vessel containing CO , N , He and possibly other gases. However, CO is the
2 2 2
laser active gas.
Energy source Electrical discharge in the resonator.
Wavelength
CO lasers emit laser beams in the infrared part of the spectrum (10,6 µm), which
is absorbed by most materials. This makes it suitable for processing of a wide
range of materials.
Beam power The present technological limit is approximately 50 kW for continuous wave
output. Pulsing is possible with frequencies up to 100 kHz. For larger laser
sources the peak power is often roughly the same as maximum power for
continuous wave operation.
Optics The wavelength means that the beam is absorbed also by glass etc. Therefore
special materials should be used for transmissive optical elements like output
windows or lenses. Copper mirrors can be used as reflective optical elements
Fibre optics cannot be used.
Consumables The gases inside the resonator will degenerate with time and consequently they
become consumables, which have to be renewed continuously. The amount of
gas used in service does, however, depend very much on the actual laser design.
Efficiency 5 % to 15 % of the input energy is available in the laser beam.

A.2.2 Nd:YAG lasers, lamp pumped
Table A.2 — Nd:YAG lasers, lamp pumped
Key properties Characteristics
Stage of technology Nd:YAG lasers have been commercially available for many years and they
represent a reasonably mature technology.
Laser active material in Resonator Neodymium doped yttrium-aluminium garnet single crystal. Nd is the laser active
component.
Energy source Flash lights for pulsed mode, electrical arc lamps for continuous mode.
Wavelength Nd:YAG lasers emit laser beams in the near-infrared part of the spectrum
(1,06 µm). Some materials, e.g. glass are transparent to this wavelength and
cannot be processed. However, most metals absorb light of the wavelength
readily.
Beam power A laser can work in either pulsed mode or continuous wave mode.
The present technological limit for peak power in pulsed mode is in the
Megawatt range. Average power is much less, typically up to 10 kW for both
types.
Optics Glass lenses and fibre optics can be used.
Consumables Lamps used as energy source have a limited lifetime.
Efficiency Below 5 % of the input energy is available in the laser beam.

A.2.3 Nd:YAG lasers, diode pumped
Table A.3 — Nd:YAG lasers, diode pumped
Key properties Characteristics
Stage of technology Nd:YAG lasers using arrays of diode lasers as the energy source is a promising
new technology. The diode lasers represent an offspring of the lasers used for
several years in information and communication technologies.
Laser active material in Resonator Neodymium doped yttrium-aluminium garnet single crystal.
Energy source Arrays of diode lasers, which again are powered by electrical energy.
Wavelength Nd:YAG lasers emit laser beams in the near-infrared part of the spectrum
(1,06 µm). Some materials, e.g. glass are transparent to this wavelength and
cannot be processed. However, most metals absorb light of the wavelength
readily.
Beam power A laser can be controlled to work in pulsed mode or continuous wave mode.
The present technological limit for peak power in pulsed mode is in the
Megawatt range. Average power is much less, typically up to 5 kW.
Optics Glass lenses and fibre optics can be used.
Consumables The diodes have a lifetime in the order of 10 000 h.
Efficiency 10 % or more of the input energy is available in the laser beam.

A.2.4 High power diode array lasers
Table A.4 — High power diode array lasers
Key properties Characteristics
Stage of technology High power diode array lasers use stacks of diode lasers working in unison in
order to generate a combined laser beam. The lasers are a further, specialised
development of the lasers used for several years in information and
communication technologies. This is a new but promising technology.
Laser active material in the Resonator Semiconductor materials inside the diodes.
Energy source Electricity
Wavelength High power diode array lasers can presently be designed to emit laser beams in
the red or near-infrared part of the spectrum (0,8 µm to 1 µm). However, other
wavelengths should be possible in the future. Some materials, e.g. glass are
transparent to this wavelength and cannot be processed. However, most metals
readily absorb light of the wavelength.
Beam power A laser can be controlled to work in pulsed mode or continuous wave mode. The
present technological limit for average power is typically up to 6 kW.
Optics Glass lenses and fibre optics can be used.
Consumables None
Efficiency Up to 50 % of the input energy is available in the laser beam.

A.2.5 Other types of lasers
A few other types of lasers have very limited industrial applications. Nd:glass and ruby lasers are similar to the
Nd:YAG lasers, lamp pumped, except that the medium in the resonator is Nd:glass or ruby, respectively.
Excimer lasers are very similar to CO lasers except that the resonator contains a combination of inert gases
(argon, krypton, xenon) and halogens such as fluorine. Excimer lasers are limited to pulse mode operation at
wavelengths of the order 0,2 µm to 0,4 µm.
A.3 Guiding, shaping and focusing the beam
A.3.1 Guiding the beam
Laser beams are for safety and other reasons normally propagated inside a tube or a fibre. The unprotected
beam thus propagates only a short distance between the focusing optics and the work piece. A CO laser
source based installation usually has a beam guide composed by a number of pieces of straight tubes. The
beam is guided inside the tubes by mirrors and/or lenses. Moving (flying) optics (see below) require at least
one of the tubes to be telescopic.
Fibre optics provides great flexib
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