IEC 60825-4:2006+AMD1:2008 CSV

IEC 60825-4
®
Edition 2.1 2009-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Safety of laser products –
Part 4: Laser guards

Sécurité des appareils à laser –
Partie 4: Protecteurs pour lasers
IEC 60825-4:2006+A1:2008

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IEC 60825-4
®
Edition 2.1 2009-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Safety of laser products –
Part 4: Laser guards

Sécurité des appareils à laser –
Partie 4: Protecteurs pour lasers

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CR
CODE PRIX
ICS 31.260 ISBN 978-2-88910-305-8
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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– 2 – 60825-4 © IEC:2006+A1:2008
CONTENTS
FOREWORD.4
INTRODUCTION.6

1 Scope.7
2 Normative references .7
3 Definitions .7
4 Laser processing machines .9
4.1 Design requirements .9
4.2 Performance requirements .10
4.3 Validation .10
4.4 User information.11
5 Proprietary laser guards.11
5.1 Design requirements .11
5.2 Performance requirements .11
5.3 Specification requirements .11
5.4 Test requirements .12
5.5 Labelling requirements .12
5.6 User information.13

Annex A (informative) General guidance on the design and selection of laser guards.14
Annex B (informative) Assessment of foreseeable exposure limit (FEL) .16
Annex C (informative) Elaboration of defined terms .23
Annex D (normative) Proprietary laser guard testing .25
Annex E (informative) Guidelines on the arrangement and installation of laser guards.27
Annex F (informative) Guideline for assessing the suitability of laser guards .37
Annex G (normative) Beam delivery systems .64

Bibliography .73

Figure B.1 – Calculation of diffuse reflections .17
Figure B.2 – Calculation of specular reflections .17
Figure B.3 – Some examples of a foreseeable fault condition .18
Figure B.4 – Four examples of errant laser beams that might have to be contained by a
temporary guard under service conditions.19
Figure B.5 – Illustration of laser guard exposure during repetitive machine operation .20
Figure B.6 – Two examples of assessed duration of exposure .21
Figure B.7 – Assessed duration of exposure for a machine with no safety monitoring.22
Figure C.1 – Illustration of guarding around a laser processing machine .23
Figure C.2 – Illustration of active laser guard parameters .24
Figure D.1 – Simplified diagram of the test arrangement.26
Figure F.1 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW CO laser .53
2
Figure F.2 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser .53
2

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60825-4 © IEC:2006+A1:2008 – 3 –
Figure F.3 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW CO laser .54
2
Figure F.4 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser .54
2
Figure F.5 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW CO laser .55
2
Figure F.6 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser .55
2
Figure F.7 – Damage resistance of 2 mm thick aluminium sheet derived from 10 s
exposure to a defocused beam during experiments using a CW CO laser.56
2
Figure F.8 – Damage resistance of 2 mm thick aluminium sheet derived from 100 s
exposure to a defocused beam during experiments using a CW CO laser.56
2
Figure F.9 – Damage resistance of 1 mm thick stainless steel sheet derived from 10 s
exposure to a defocused beam during experiments using a CW CO laser.57
2
Figure F.10 – Damage resistance of 1 mm thick stainless steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser .57
2
Figure F.11 – Damage resistance of 6 mm thick polycarbonate sheet derived from 10 s
exposure to a defocused beam during experiments using a CW CO laser.58
2
Figure F.12 – Damage resistance of 6 mm thick polycarbonate sheet derived from
100 s exposure to a defocused beam during experiments using a CW CO laser .58
2
Figure F.13 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser .59
Figure F.14 – Damage resistance of 1 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser .59
Figure F.15 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser .60
Figure F.16 – Damage resistance of 2 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser .60
Figure F.17 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
10 s exposure to a defocused beam during experiments using a CW Nd:YAG laser .61
Figure F.18 – Damage resistance of 3 mm thick zinc coated steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser .61
Figure F.19 – Damage resistance of 2 mm thick aluminium sheet derived from 10 s
exposure to a defocused beam during experiments using a CW Nd:YAG laser.62
Figure F.20 – Damage resistance of 2 mm thick aluminium sheet derived from 100 s

exposure to a defocused beam during experiments using a CW Nd:YAG laser.62
Figure F.21 – Damage resistance of 1 mm thick stainless steel sheet derived from 10 s
exposure to a defocused beam during experiments using a CW Nd:YAG laser.63
Figure F.22 – Damage resistance of 1 mm thick stainless steel sheet derived from
100 s exposure to a defocused beam during experiments using a CW Nd:YAG laser .63

Table D.1 – Laser guard classification .26
Table F.1 – Application of ALARP.40
Table G.1 – Beam delivery systems using free space beam delivery systems.69
Table G.2 – Beam delivery systems using fibre optic cables .71

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INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________

SAFETY OF LASER PRODUCTS –

Part 4: Laser guards



FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60825-4 has been prepared by IEC technical committee 76: Optical
radiation safety and laser equipment.
This consolidated version of IEC 60825-4 consists of the second edition (2006) [documents
76/342/FDIS and 76/351/RVD] and its amendment 1 (2008) [documents 76/383/FDIS and
76/385/RVD].
The technical content is therefore identical to the base edition and its amendment and has
been prepared for user convenience.
It bears the edition number 2.1.
A vertical line in the margin shows where the base publication has been modified by
amendment 1.

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60825-4 © IEC:2006+A1:2008 – 5 –
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of the base publication and its amendments will
remain unchanged until the maintenance result date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date,
the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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INTRODUCTION
At low levels of irradiance or radiant exposure, the selection of material and thickness for
shielding against laser radiation is determined primarily by a need to provide sufficient optical
attenuation. However, at higher levels, an additional consideration is the ability of the laser
radiation to remove guard material – typically by melting, oxidation or ablation; processes that
could lead to laser radiation penetrating a normally opaque material.
IEC 60825-1 deals with basic issues concerning laser guards, including human access,
interlocking and labelling, and gives general guidance on the design of protective housings and
enclosures for high-power lasers.
This part of IEC 60825 deals with protection against laser radiation only. Hazards from
secondary radiation that may arise during material processing are not addressed.
Laser guards may also comply with standards for laser protective eyewear, but such
compliance is not necessarily sufficient to satisfy the requirements of this standard.
Where the term “irradiance” is used, the expression “irradiance or radiant exposure, as
appropriate” is implied.

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60825-4 © IEC:2006+A1:2008 – 7 –
SAFETY OF LASER PRODUCTS –

Part 4: Laser guards



1 Scope
This part of IEC 60825 specifies the requirements for laser guards, permanent and temporary
(for example for service), that enclose the process zone of a laser processing machine, and
specifications for proprietary laser guards.
This standard applies to all component parts of a guard including clear (visibly transmitting)
screens and viewing windows, panels, laser curtains and walls. Requirements for beam path
components, beam stops and those other parts of a protective housing of a laser product which
do not enclose the process zone are contained in IEC 60825-1.
In addition this part of IEC 60825 indicates:
a) how to assess and specify the protective properties of a laser guard; and
b) how to select a laser guard.
2 Normative references
The following referenced documents are indispensable for the application of this document. For
dated references, only the edition cited applies. For undated references, the latest edition of
the referenced document (including any amendments) applies.
IEC 60825-1:2007, Safety of laser products – Part 1: Equipment classification and
requirements
ISO 11553-1:2005, Safety of machinery – Laser processing machines – Safety requirements
ISO 12100-1:2003, Safety of machinery – Basic concepts, general principles for design –
Part 1: Basic terminology, methodology
ISO 12100-2:2003, Safety of machinery – Basic concepts, general principles for design – Part 2:
Technical principles and specifications
ISO 13849-1:2006, Safety of machinery – Safety-related parts of control systems – Part 1:
General principles for design
ISO 14121-1:2007, Safety of machinery – Risk assessment – Part 1: Principles
3 Definitions
For the purpose of this part of IEC 60825, the following definitions apply in addition to the
definitions given in IEC 60825-1.

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3.1
active guard protection time
for a given laser exposure of the front surface of an active laser guard, the minimum time,
measured from the issue of an active guard termination signal, for which the active laser guard can
safely prevent laser radiation accessible at its rear surface from exceeding the class 1 AEL
3.2
active guard termination signal
the signal issued by an active guard in response to an excess exposure of its front surface to
laser radiation and which is intended to lead to automatic termination of the laser radiation
NOTE The action of a safety interlock becoming open circuit is considered a "signal" in this context.
3.3
active laser guard
a laser guard which is part of a safety-related control system. The control system generates an
active guard termination signal in response to the effect of laser radiation on the front surface
of the laser guard
3.4
foreseeable exposure limit
FEL
the maximum laser exposure on the front surface of the laser guard, within the maintenance
inspection interval, assessed under normal and reasonably foreseeable fault conditions
3.5
front surface
the face of the laser guard intended for exposure to laser radiation
3.6
laser guard
a physical barrier which limits the extent of a danger zone by preventing laser radiation
accessible at its rear surface from exceeding the class 1 AEL
3.7
laser processing machine
a machine which uses a laser to process materials and is within the scope of ISO 11553-1
3.8
laser termination time
the maximum time taken, from generation of an active guard termination signal, for the laser
radiation to be terminated
NOTE Laser termination time does not refer to the response of an active laser guard but to the response of the
laser processing machine, in particular the laser safety shutter.
3.9
maintenance inspection interval
the time between successive safety maintenance inspections of a laser guard
3.10
passive laser guard
a laser guard which relies for its operation on its physical properties only

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60825-4 © IEC:2006+A1:2008 – 9 –
3.11
process zone
the zone where the laser beam interacts with the material to be processed
3.12
proprietary laser guard
a passive or active laser guard, offered by its manufacturer as a guard with a specified
protective exposure limit
3.13
protective exposure limit
PEL
the maximum laser exposure of the front surface of a laser guard which is specified to prevent
laser radiation accessible at its rear surface from exceeding the class 1 AEL
NOTE 1 In practice, there may be more than one maximum exposure.
NOTE 2 Different PELs may be assigned to different regions of a laser guard if these regions are clearly
identifiable (for example a viewing window forming an integral part of a laser guard).
3.14
rear surface
any surface of a laser guard that is remote from the associated laser radiation and usually
accessible to the user
3.15
reasonably foreseeable
an event (or condition) when it is credible and its likelihood of occurrence (or existence) cannot
be disregarded
3.16
safety maintenance inspection
documented inspection performed in accordance with manufacturer’s instructions
3.17
temporary laser guard
a substitute or supplementary active or passive laser guard intended to limit the extent of the
danger zone during some service operations of the laser processing machine
4 Laser processing machines
This clause specifies the requirements for laser guards that enclose the process zone and are
supplied by the laser processing machine manufacturer.
4.1 Design requirements
A laser guard shall satisfy ISO 12100-2 with respect to the general requirements for guards
and also the more specific requirements with regard to its location and method of fixture. In
addition, the following specific laser requirements shall be met.
4.1.1 General requirements
A laser guard, in its intended location, shall not give rise to any associated hazard at or beyond
its rear surface when exposed to laser radiation up to the foreseeable exposure limit.

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NOTE 1 Examples of associated hazards include: high temperature, the release of toxic materials, fire, explosion,
electricity.
NOTE 2 See Annex B for assessment of foreseeable exposure limit.
4.1.2 Consumable parts of laser guards
Provision shall be made for the replacement of parts of a laser guard prone to damage by laser
radiation.
NOTE An example of such a part would be a sacrificial or interchangeable screen.
4.2 Performance requirements
4.2.1 General
When the front surface of a laser guard is subjected to exposure to laser radiation at the
foreseeable exposure limit, the laser guard shall prevent laser radiation accessible at its rear
surface from exceeding the class 1 AEL at any time over the period of the maintenance
inspection interval. For automated laser processing machines, the minimum value of the
maintenance inspection interval shall be 8 h.
This requirement shall be satisfied over the intended lifetime of the laser guard under expected
conditions of operation.
NOTE 1 This requirement implies both low transmission of laser radiation and resistance to laser-induced
damage.
NOTE 2 Some materials may lose their protective properties due to ageing, exposure to ultraviolet radiation,
certain gases, temperature, humidity and other environmental conditions. Additionally, some materials will transmit
laser radiation under high-intensity laser exposure, even though there may be no visible damage (i.e. reversible
bleaching).
4.2.2 Active laser guards
a) The active guard protection time shall exceed the laser termination time up to the
foreseeable exposure limits.
b) The generation of an active guard termination signal shall give rise to a visible or audible
warning. A manual reset is required before laser emission can recommence.
NOTE See Annex C.2 for an elaboration of terms.
4.3 Validation
If the laser processing machine manufacturer chooses to make a laser guard, the manufacturer
shall confirm that the guard complies with the design requirements of 4.1 and can satisfy the
performance requirements set out in 4.2.
NOTE See Annex A for guidance on the design and selection of laser guards.
4.3.1 Validation of performance
4.3.1.1 The complete laser guard, or an appropriate sample of the material of construction of
the laser guard, shall be tested at each FEL identified.
NOTE 1 A table of predetermined PELs for common combinations of lasers and guarding materials, together with
suitable testing procedures shall be issued as an informative annex in a future amendment to this standard. This
could provide a simple alternative to direct testing for the majority of cases.
NOTE 2 See Annex B for the assessment of FEL.

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60825-4 © IEC:2006+A1:2008 – 11 –
4.3.1.2 For testing purposes, the FEL exposure shall be achieved either:
a) by calculating or measuring the exposure and reproducing the conditions; or
b) without quantifying the FEL, by creating the machine conditions under which the FEL is
produced.
The condition of the laser guard or sample shall be such as to replicate those physical
conditions of the front surface permitted within the scope of the routine inspection instructions
and within the service life of the guard, which minimize the laser radiation protective properties
of the laser guard (for example wear and tear and surface contamination) (see 4.4.2).
4.4 User information
4.4.1 The manufacturer shall document and provide to the user the maintenance inspection
interval for the laser guard, and details of inspection and test procedures, cleaning,
replacement or repair of da
...