ISO/TR 17529:2014

TECHNICAL ISO/TR
REPORT 17529
First edition
2014-11-15
Machine tools — Practical guidance
and example of risk assessment on
electro-discharge machines
Machines-outils — Lignes directrices et appréciation du risque pour
les machines d’électro-érosion
Reference number
ISO/TR 17529:2014(E)
©
ISO 2014

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ISO/TR 17529:2014(E)

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ISO/TR 17529:2014(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Information for the risk assessment . 1
2.1 General . 1
2.2 Hazard identification on EDM equipment and EDM systems during the life phases . 4
3 Hazard identification . 8
4 Risk estimation, evaluation, and reduction. 9
4.1 Safety requirements and/or protective measures . 9
4.2 Protective measures and their verification procedures . 9
4.3 Information for use . 9
5 Risk estimation methods .10
5.1 General .10
5.2 Risk estimation according to ISO/TR 14121-2 .10
5.3 Risk estimation according to ISO 13849-1 .10
5.4 Risk estimation according to ISO 28881 .11
5.5 Risk parameter .14
6 Example of risk assessment .16
Bibliography .23
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ISO/TR 17529:2014(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword — Supplementary information.
The committee responsible for this document is ISO/TC 39, Machine tools, Subcommittee SC 10, Safety.
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ISO/TR 17529:2014(E)

Introduction
This Technical Report gives additional guidance to the manufacturer to use ISO 28881 by showing a
process of the risk assessment based on type A and B standards.
Some documents (e.g. technical reports, guidelines) have already been published but they usually
describe about the risk assessment only for machines or for control systems. Manufacturers need
guidance that covers both aspects of machines and control systems.
This Technical Report deals with risk assessment for machine and control jointly, i.e. the result of the risk
assessment carried out for significant hazards listed in ISO 28881:2013, Table 1, including the results of
risk reduction by the protective measures described in ISO 28881:2013, Clauses 5 and 6 and the process
of the selection of PL as described in ISO 28881:2013, 5.2, are shown.
r
This Technical Report, based on the following International Standards, is worked out in cooperation
with JMTBA (Japanese Machine Tool Builder Association) and ISO/TC 39/SC 10.
— ISO 28881;
— ISO 12100;
— ISO 13849-1;
— ISO/TR 14121-2.
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TECHNICAL REPORT ISO/TR 17529:2014(E)
Machine tools — Practical guidance and example of risk
assessment on electro-discharge machines
1 Scope
This Technical Report gives practical guidance on conducting risk assessment for machinery in
accordance with ISO 12100, ISO 13849-1, and ISO/TR 14121-2. It describes the method, tools, and
examples used to generate ISO 28881, to reduce the risk of potential harm on EDM equipment and EDM
systems by persons involved in the design, installation, or modification of machinery (e.g. designers,
technicians, safety specialists).
2 Information for the risk assessment
2.1 General
The following points should be considered:
— specifications of the EDM equipment and EDM systems (For example of limits of the machinery, see
Table 1.);
— type of machinery (For examples, see Figures 1 and 2.);
— hazards and associated hazardous situations;
— estimated risk for each identified hazard and hazardous situations including intended use and any
reasonably foreseeable misuse;
— evaluation of the risk and making decisions about the need for risk reduction.
Eliminate or reduce the risk by means of the three-step method in accordance with ISO 12100:2010, 6.1.
— step 1: inherently safe design measures;
— step 2: safeguarding and/or complementary protective measures;
— step 3: information for use.
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ISO/TR 17529:2014(E)

Table 1 — Example of specifications of the EDM equipment and EDM systems
Items Wire EDM Sinker EDM
EDM machine figure See Figure 1 See Figure 2
Power supply
   Input voltage 200 V a.c., three-phase 200 V a.c., three-phase
   Electrical supply capacity 13,5 kVA 13,0 kVA
   Compressed air 0,5 MPa to 0,7 MPa 0,6 MPa
Equal to or more than 75 l/min
Machine weight 2 000 kg 5 000 kg
Generator
   Type of circuits Transistor pulse Transistor pulse
(energy retrieval type)
   Output voltage 300 V 200 V
   Output current 50 A 60 A
Linear axis (X, Y, Z)
   Stroke (mm) X350 × Y250 × Z220 X300 × Y200 × Z200
   Output power a.c. 0,6 kW a.c. 1,0 kW
   Feeding speed 1 300 mm/min 5 000 mm/min
   Z-axis With brake With brake
Without balancer Without balancer
Rotary axis Not applicable C-axis
   Output power a.c. 0,5 kW
Electrode
   Size Wire diameter: 0,1 to 0,3 [mm] Not specified
   Max. weight 10 kg 50 kg
Automatic tool changer Not applicable Applicable
   Number of electrodes 1 spool 30 electrodes
   Max. weight per electrode 10 kg 10 kg
Workpiece 650 × 450 × 195 mm
   Max. size 800 × 600 × 215 mm 650 × 450 mm
   Max. weight 500 kg 800 kg
Dielectric fluid
   Material Water Oil with flash point more than 60 °C
   Container capacity 440 l 350 l
Installation environment
   Temperature 10 °C to 35 °C 10 °C to 35 °C
   Relative humidity 35 % to 75 % (no condensation) 35 % to 75 % (no condensation)
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ISO/TR 17529:2014(E)

Key
1 shielded enclosure with door(s) 6 workpiece
2 wire supply spool 7 lower wire guide
3 wire electrode 8 upper wire guide
4 wire evacuation 9 interlocking guard
5 electrical cabinet (generator) 10 fix guards
Figure 1 — Example of wire cutting machine
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ISO/TR 17529:2014(E)

Key
1 local fire alarm
2 fire detection device
3 electrical cabinet (generator)
4 interlocking shielded guard
5 linear electrode changer
Figure 2 — Example of die sinking machine with linear electrode changer
2.2 Hazard identification on EDM equipment and EDM systems during the life phases
2.2.1 Whole life cycle of the EDM equipment and EDM systems
The phases of the life cycle of the EDM equipment and EDM systems considered to be significant in this
example are the following:
— transportation (including in-house transport and movement);
— assembly, installation, and commissioning;
— setting and operation;
— cleaning and maintenance;
— fault finding and troubleshooting;
— removal, dismantling, and disposal.
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ISO/TR 17529:2014(E)

2.2.2 Space limits
EDM equipment and EDM systems are assumed to be used in the industrial environment of the factory.
EDM equipment and EDM systems are assumed to be used in the environment without direct sunshine,
dust, and water splash.
EDM equipment and EDM systems are not assumed to be used in the atmosphere having fire or explosion
hazard.
Necessary area for all phases of the life cycle of the EDM equipment and EDM systems (i.e. installation,
operation, maintenance, etc.) is assumed to be secured. However, concrete size is not specified here
because it does not seem to be reasonable from the objective of this example.
2.2.3 Time limits
This example describes only the aspects of time limits which should be generally determined because it
is not reasonable to specify concrete values here from the objective of this example.
— life of the machine;
— interval of inspection;
— interval of parts replacement;
— interval of cleaning and maintenance.
2.2.4 Use limits (intended use and reasonably foreseeable misuse)
Intended use and reasonably foreseeable misuse of the EDM equipment and EDM systems should be
considered in each phase of the life cycle.
The EDM is assumed to be used by a person
— who is a trained operator,
— without visual or hearing impairment,
— without restrictions on physical ability of upper or lower limbs, or
— without usage of medical implants liable to be affected by electromagnetic radiation (e.g. pacemaker).
See Table 2 for example of lifecycle and task in automatic, setting, and discharge alignment operation on
EDM equipment and EDM systems.
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ISO/TR 17529:2014(E)

Table 2 — The phases of lifecycle and tasks in automatic, setting, and discharge alignment
operation
Task, operator, and reasonably foreseeable misuse
Automatic Description Wire EDM Sinker EDM
operation
(1) Automatic workpiece preparation
(machining)
— measuring workpieces (vertical, parallel, edge, etc.) X X
— measuring workpieces (with high voltage) X X
— measuring workpieces (with low voltage) X X
(2) Automatic electrode preparation
— connection of wire electrode X
— vertical wire alignment (adjusting by U-axis and V-axis) X
— clamping electrode (with automatic tool changer) X
— measuring electrodes (edge, centre, etc.) X
(3) Making and verifying machining program
— programmed operation without electric discharge power X X
(4) Tasks during processing
— starting process X X
— intervention during processing X X
— adjusting flushing pressure X
— adjusting flushing pressure (injection, suction) X
— monitoring process condition X X
— adjusting machining conditions X X
— wire reconnection at break point X
(5) Tasks after processing
— measuring workpieces (with high voltage) X X
— measuring workpieces (with low voltage) X X
— cutting wire electrode X
(6) Automatic removal of core part
— preparation for cutting core part X
— cutting core part X
— removing core part X
Automatic operation is intended to be carried out by
— operators with appropriate knowledge and/or experience on the usage of machine and with full understand-
ing of the instructions described in the information for use, and
— persons under the supervision of such operators.
Reasonably foreseeable misuses in the automatic operation are
— opening guards during programmed operation,
— starting programmed operation with guard open, and
— processing with inappropriate fluid level in work tank.
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ISO/TR 17529:2014(E)

Table 2 (continued)
Task, operator, and reasonably foreseeable misuse
Setting operation Description Wire EDM Sinker EDM
(1) Confirmation of workpiece X X
(2) Setting of workpiece
— workpiece setting (manual) X X
— axis feeding (manual) X X
— measuring workpieces (vertical, parallel, edge, etc.) X X
— measuring workpieces (with low voltage) X X
(3) Setting of electrode
— attaching wire electrode (spool) X
— installing wire electrode to rollers and connecting it X
— clamping electrode X
— transporting wire electrode X
— adjusting location of metal parts for power supply (energizing X
parts, in other words)
— wire tension setting X
— vertical wire alignment (adjusting by U-axis and V-axis) X
— adjusting inclination of electrode X
— measuring electrode X
(in case of EDM drilling, measuring residual electrode length)
— correcting straightness of small tubular electrode (with spindle X
−1
rotation of 1 000 min )
(4) Other setting
— nozzle distance, clearance X
— direction of flushing nozzle X
— setting of flushing pressure X X
— program, machining conditions X X
— filling fluid, adjusting fluid level X X
— opening and closing or vertical movement of work tank X X
(5) Making and verifying machining program
— programmed operation without electric discharge power X X
(6) Tasks during intervention or after processing
— wire reconnection at break point X
— opening and closing, or vertical movement of work tank X X
— axis feeding X X
— measuring workpiece (with low voltage) X
— measuring workpiece (with low voltage) X
(in case of EDM drilling, confirming piercing through workpiece)
— cutting wire electrode (by scissors, etc.) X
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ISO/TR 17529:2014(E)

Table 2 (continued)
Task, operator, and reasonably foreseeable misuse
Setting operation Description Wire EDM Sinker EDM
(continued)
— cleaning workpiece and work tank after processing (by fluid X X
ejection)
(7) Handling of core part
— preparation for cutting core part X
— removing core part X
— measuring workpiece (with low voltage) X
— taking out workpiece X X
(8) Electrode change
— removing wire spool X
— removing electrode X
Setting operation is intended to be carried out by
— trained and/or qualified operators with appropriate knowledge and/or experience on the usage of machine
and with full understanding of the instructions described in the information for use.
Reasonably foreseeable misuses in the setting operation are
— processing flammable materials,
— starting programmed operation with guard open, and
— switching on electric machining power with guard open.
Discharge Description Wire EDM Sinker EDM
alignment
(1) Exhaust air extraction adjustment X X
operation
(2) Dielectric fluid flushing adjustment X X
(3) Visual machining inspection X X
(4) Electrode alignment X X
Discharge alignment operation is intended to be carried out by
— trained and/or qualified operators with appropriate knowledge and/or experience on the usage of machine
and with full understanding of the instructions described in the information for use.
Reasonably foreseeable misuses in the discharge alignment operation are
— processing flammable materials,
— starting programmed operation with guard open, and
— forgetting to switch off electric machining power after discharge alignment operation.
3 Hazard identification
Particular attention is paid to hazards dealing with (see ISO 28881:2013, Clause 4)
— electrical hazards (electrode voltage),
— flammable dielectric fluid (level, temperature, and fire detection),
— hazardous substances (waste disposal, filters, used dielectric fluid, electrodes, and sludge), and
— electromagnetic emissions (radiated and conducted), see IEC 61000-6-2:2005 for EMC for immunity
and IEC 61000-6-4:2011 for EMC for emission.
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ISO/TR 17529:2014(E)

The list of significant hazards and major sources of these hazards associated with electro-discharge
machines are given in ISO 28881:2013, Table 1.
4 Risk estimation, evaluation, and reduction
4.1 Safety requirements and/or protective measures
EDM equipment and EDM systems should all comply with the safety requirements and/or protective
measures and be verified in accordance with ISO 28881:2013, Clause 5. In addition, the equipment
and systems should be designed in accordance with the principles of ISO 12100 for relevant, but not
significant, hazards, which are not dealt with by the above mentioned International Standards. Analysis
of failure of machine components, including failure in the control system(s), is part of the risk assessment
and guidance on this subject is given in ISO 13849-1.
Safety functions of control systems should be implemented using safety-related parts designed,
constructed and applied in accordance with ISO 13849-1. Safety-related parts of control systems
implementing the safety functions should meet the requirements for the performance level and category
of ISO 13849-1, as listed in ISO 28881:2013, Table 2.
General safety requirements and/or protective measures for EDM equipment and EDM systems are
given in ISO 28881:2013, Table 2 and ISO 28881:2013, Table 3.
4.2 Protective measures and their verification procedures
Safety requirements and/or protective measures as needed for EDM equipment and EDM systems to
prevent hazards identified in hazard identification, should be taken and verified using the procedures
indicated in the verification column (see ISO 28881:2013, Table 3), with the following abbreviated
phrases:
— by testing (e.g. functional or practical check);
— by measurement;
— by calculation;
— by visual inspection, if testing and calculation are not adequate;
— by analysis of documentation (e.g. circuit or functional diagram, information for use).
4.3 Information for use
Information for use refers to communication links, such as texts, words, signs, signals, symbols, or
diagrams, which are used separately or in combination, to convey information to the user and which
should be in accordance with ISO 12100:2010, 6.4.
The information for use should document hazards which can occur during the life of the machine to
both the operator and other persons who have access to the danger zone(s) for conditions of intended
use, including reasonably foreseeable misuse of the machine (see ISO 12100:2010, 3.24) for both spark
erosion with automatic mode and operations requiring intervention (e.g. setting, maintenance, and
repair).
The instruction handbook should provide all necessary information regarding transport, installation,
operation, setting, maintenance, cleaning, and disposal of the EDM equipment and EDM system, in
accordance with ISO 12100:2010, 6.4.5.
Information for use, such as
— marking, signs, and written warnings, and
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ISO/TR 17529:2014(E)

— instruction handbook (special recommendation, general safety information, power specifications,
compressed air specifications, flammable dielectric fluid, hazardous substances, electromagnetic
emissions, special recommendations for EDM operation and noise) are given in ISO 28881:2013,
Clause 6.
5 Risk estimation methods
5.1 General
Some kinds of risk graph methods are used in this technical report. Sub-clauses shown in this clause
explain how to use the risk graph methods. 5.5 explains the risk parameters used in 5.2, 5.3, and 5.4.
5.2 Risk estimation according to ISO/TR 14121-2
This risk graph method (see Figure 3) is derived from ISO/TR 14121-2:2012, 6.3.2. This risk graph
method shows how to estimate both initial risk and residual risk of the hazards on machine. The result
of this estimation is used to evaluate if the residual risk is permissible or not. If the residual risk is not
permissible, risk assessment cycle has to be implemented again until the residual risk is permitted.
This risk graph method uses risk parameters S, F, O, and A, then this classify the risk to six levels. See
ISO/TR 14121-2 for more information.
This method should be used for general risk assessment.
Figure 3 — Example of risk graph for risk estimation(ISO/TR 14121-2:2012, Figure 3)
5.3 Risk estimation according to ISO 13849-1
This risk graph method (see Figure 4) is derived from ISO 13849-1:2006, Annex A. This risk graph
method shows how to estimate risk to determine required performance level according to ISO 13849-1.
The result of this risk estimation is not used to evaluate residual risk, but it is used only to determine
required performance level for safety related parts of control system. This risk graph method uses
risk parameters S, F, and P and classifies PL to five levels. See ISO 13849-1:2006, Annex A for more
r
information.
This method should be used for risk assessments which involve control systems.
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ISO/TR 17529:2014(E)


Key Risk parameters
1 starting point for evaluation of safety function’s S severity of injury
contribution to risk reduction
L low contribution to risk reduction S1 slight (normally reversible injury)
H high contribution to risk reduction S2 serious (normally irreversible injury or death)
PL required performance level F frequency and/or exposure to hazard
r
F1 seldom-to-less-often and/or exposure time is short
F2 frequent-to-continuous and/or exposure time is
long
P possibility of avoiding hazard or limiting harm
P1 possible under specific conditions
P2 scarcely possible
NOTE The risk parameter of “possibility of avoidance or reduction of harm” is expressed as “P” in
ISO 13849-1:2006, Figure A.1, but “A” is used in ISO/TR 14121-2:2012, Figure A.3. They have the same meaning
essentially; therefore “A” is adopted in this Technical Report.
Figure 4 — Risk graph for determining required PL for safety function(ISO 13849-1:2006,
r
Figure A.1)
5.4 Risk estimation according to ISO 28881
The Figures 5 and 6 show the equivalent method in the risk graph method described in 5.2 and 5.3
respectively. This information may be useful if risk matrix, which is used for risk estimation with
combination severity of harm and probability of occurrence, already exists.
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ISO/TR 17529:2014(E)

5.4.1 Estimate frequency and impact of possible hazards
First step: The manufacturer should check if foreseeable hazards happened in the past with the
earlier produced EDM equipment and EDM system, and identify the frequency (ranging
from unlikely to often) as well as the impact of hazards (from negligible injury to dan-
ger of life). Then, estimate the possible hazards on the equipment to be designed and
complete the file accordingly. If the result of this estimation is located in the dark grey
area, such hazards are not acceptable and a responsible person should be put in charge
to review the technical solution according to ISO 12100. The reviewed solution should
be checked again to verify that the expected risk minimization enters below in the dark
grey area.

Figure 5 — Estimate frequency and impact of possible hazards(ISO 28881:2013, Figure D.1)
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ISO/TR 17529:2014(E)

5.4.2 Identify required performance level (PL ) to prevent possible hazards
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Second step: Make sure that all identified risks are below the dark grey areas; identify the required
performance level from often (i.e. negligible injury) to unlikely (i.e. danger of life) for
each channel, as indicated in the light grey area.

Figure 6 — Identify required performance level (PL ) to prevent possible
r
hazards(ISO 28881:2013, Figure D.2)
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ISO/TR 17529:2014(E)

5.4.3 Define mean time to dangerous failure (MTTF ) and diagnostic coverage (DC )
d avg
Third step: Define the necessary mean time to dangerous failure (MTTF ) of the available com-
d
ponents, as well as the diagnostic coverage (DC ) of the control system, to identify
avg
the required performance level (PL ) and the category, if necessary, as shown in of
r
ISO 13849–1:2006, Figure 5.

Key
PL performance level
1 MTTF of each channel = low
d
2 MTTF of each channel = medium
d
3 MTTF of each channel = high
d
Figure 7 — Define mean time to dangerous failure (MTTF ) and diagnostic coverage (DC )
d avg
(ISO 28881:2013, Figure D.3)
5.5 Risk parameter
Risk parameters used in Table 3 are as follows.
NOTE These abbreviations are based on the risk parameters used in ISO/TR 14121-2:2012, Figure A.3 and in
ISO 13849-1:2006, Figure A.1. Although there are slight differences of explanations between ISO/TR 14121-2 and
ISO 13849-1, it could be considered that the risk parameters are essentially the same in meaning. In this example,
more concrete interpretation is added.
S: Severity of harm
S1: slight injury (usually reversible), for example, scratches, laceration, bruising, light wound requiring
first aid
S2: serious injury (usually irreversible, including fatality), for example, broken or torn-out or crushed
limbs, fractures, serious injuries requiring stitches, major musculoskeletal troubles (MST), fatalities
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F: Frequency and/or duration of exposure to hazard
F1: seldom or short duration, i.e.
— the frequency of access to the hazard zone is less than once per 1 h, or
— time spent in the hazard zone is less than 15 min per one time.
F2: frequent or long duration, i.e.
— the frequency of access to the hazard zone is once or more per 1 h, or
— time spent in the hazard zone is equal to or more than 15 min per one time.
In this regard, taking account of “natu
...