SIST EN 12957:2002

SLOVENSKI STANDARD
SIST EN 12957:2002
01-januar-2002
Machine tools - Safety - Electro discharge machines
Machine tools - Safety - Electro Discharge Machines
Werkzeugmaschinen - Sicherheit - Funkenerodiermaschinen
Machines-outils - Sécurité - Machines d'électro-érosion
Ta slovenski standard je istoveten z: EN 12957:2001
ICS:
25.120.40 Elektrokemijski stroji Electrochemical machines
SIST EN 12957:2002 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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EUROPEAN STANDARD
EN 12957
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2001
ICS 25.120.40
English version
Machine tools - Safety - Electro Discharge Machines
Machines-outils - Sécurité - Machines d'électro-érosion Werkzeugmaschinen - Sicherheit -
Funkenerodiermaschinen
This European Standard was approved by CEN on 9 May 2001.
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 Management Centre 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2001 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12957:2001 E
worldwide for CEN national Members.

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EN 12957:2001 (E)
Contents page
Foreword.2
0 Introduction .3
1 Scope.3
2 Normative references .3
3 Terms and definitions .5
4 List of hazards.7
5 Safety requirements and/or measures.10
5.1 General requirements .10
5.2 Operating modes .10
5.3 Stop functions .11
5.4 Safety related parts of control systems for EDM equipment or EDM systems .12
5.5 Specific requirements .12
6 Verification of safety requirements and/or measures .21
7 Information for use.21
7.1 General .21
7.2 Markings, signs, written warnings.21
7.3 Instruction handbook .21
Annex A (informative) Examples and schematic pictures .24
Annex B (normative) Noise emission measurements.33
Annex ZA (informative) Clauses of this European Standard addressing essential requirements or other
provisions of EU Directives.34
Foreword
This European Standard has been prepared by Technical Committee CEN/TC 143 "Machine tools - Safety",
the secretariat of which is held by SNV.
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 January 2002, and conflicting national standards shall be withdrawn
at the latest by January 2002.
This European Standard has been prepared under a mandate given to CEN by the European Commission
and the European Free Trade Association, and supports essential requirements of EU Directive(s).
Annexes A and ZA of this standard are informative, Annex B is normative.
For relationship with EC Directives, see informative Annex ZA, which is an integral part of this standard.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark,
Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal,
Spain, Sweden, Switzerland and the United Kingdom.
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EN 12957:2001 (E)
0 Introduction
This standard applies to equipment using the process of Electro Discharge Machining (EDM) as defined in
clause 3. This European Standard is a type C Standard as stated in EN 1070.
The machinery concerned and the extent to which hazards, hazardous situations and events are covered are
indicated in the scope of this standard.
Complementary guidance is given in type A and B Standards to which reference is made in the text.
When provisions of this type C Standard are different from those which are stated in type A or B Standards,
the provisions of this type C Standard take precedence over the provisions of the other standards, for
machines that have been designed and built according to the provisions of this type C Standard. It provides
one means of conforming with the Essential Health and Safety Requirements (EHSR’s) of the "Machinery
Directive" (98/37/EC).
1 Scope
1.1 This standard specifies technical safety requirements and measures, applicable to EDM equipment
and EDM system (e.g. for spark erosion-sinking, spark erosion-wire cutting), to be adopted by persons
undertaking the design, construction, installation and/or supply of such equipment. This standard also
includes information to be provided by the manufacturer to the user.
1.2 The design requirements of this standard shall not apply to arc eroding and electro chemical
machining equipment.
1.3 This standard takes account of the intended use in normal workshop environment and non
explosive atmospheres including installation, setting, maintenance, repair and dismantling for removal or
disposal of EDM equipment.
1.4 This standard also applies to auxiliary devices essential for EDM processing.
1.5 This standard deals with specific hazards defined in clause 4, Table 1, and the measures of
prevention in clause 5, Table 2.
1.6 This standard applies to machines built after its date of issue.
NOTE Directive 94/9/EC concerning equipment and protective systems intended for use in potentially
explosive atmospheres can be applicable to the type of machine or equipment covered by this European
Standard. The present standard is not intended to provide means of complying with the essential health and
safety requirements of Directive 94/9/EC.
2 Normative references
This European Standard contains dated or not dated references on provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed hereafter.
For dated references, subsequent amendments to or revisions of any of these publications apply to this
European Standard only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to applies (including amendments).
EN 2:1992 Classification of fires
EN 54-1:1996 Fire detection and fire alarm systems - Part 1: Introduction
EN 292-1:1991 Safety of machinery - Basic concepts, general principles for design - Part 1:
Basic terminology, methodology
EN 292-2:1991 Safety of machinery - Basic concepts, general principles for design - Part 2:
Technical principles and specifications
EN 292-2:1991/A1:1995 Safety of machinery - Basic concepts, general principles for design - Part 2:
Technical principles and specifications, (Amendment A.1)
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EN 12957:2001 (E)
EN 294:1992 Safety of machinery - Safety distances to prevent danger zones being
reached by the upper limbs
EN 349:1993 Safety of machinery - Minimum gaps to avoid crushing of parts of the human
body
EN 418:1992 Safety of machinery - Emergency stop equipment, functional aspects -
Principles for design
EN 626-1:1994 Safety of machinery - Reduction of risks to health from hazardous
substances emitted by machinery - Part 1: Principles and specifications for
machinery manufacturers
EN 775:1992 Manipulating industrial robots - Safety (ISO 10218:1992 modified)
EN 811:1996 Safety of machinery - Safety distances to prevent danger zones being
reached by the lower limbs
EN 953:1997 Safety of machinery - Guards - General requirements for the design and
construction of fixed and movable guards
EN 954-1:1996 Safety of machinery - Safety related parts of control systems - Part 1:
General principles for design
EN 982:1996 Safety of machinery - Safety requirements for fluid power systems and their
components - Hydraulics
EN 983:1996 Safety of machinery - Safety requirements for fluid power systems and their
components - Pneumatics
EN 999:1998 Safety of machinery - The positioning of protective equipment in respect of
approach speeds of parts of the human body
EN 1037:1995 Safety of machinery - Prevention of unexpected start-up
EN 1050:1996 Safety of machinery - Principles for risk assessment
EN 1070:1998 Safety of machinery - Terminology
EN 1088:1995 Safety of machinery - Interlocking devices associated with guards - Principles
for design and selection
prEN 12437-1:1996 Safety of machinery - Permanent means of access to machines and
industrial plants - Part 1: Choice of a fixed means of access between two
levels
prEN 12437-2:1996 Safety of machinery - Permanent means of access to machines and
industrial plants - Part 2: Working platforms and gangways
prEN 12437-3:1996 Safety of machinery - Permanent means of access to machines and
industrial plants - Part 3: Stairways, stepladders and guard-rails
prEN 12437-4:1996 Safety of machinery - Permanent means of access to machines and
industrial plants - Part 4: Fixed ladders
EN 55011:1998 Industrial, scientific and medical (ISM) radio frequency equipment - Radio
disturbance characteristics - Limits and methods of measurement (CISPR
11:1997, modified)
EN 60204-1:1997 Safety of machinery - Electrical equipment of machines - Part 1: General
requirements (IEC 60204-1:1997)
EN 60529:1991 Degrees of protection provided by enclosures (IP code) (IEC 60529:1989)
EN 60742:1995 Isolating transformers and safety isolating transformers - Requirements (IEC
60742:1983 + A1:1992, modified)
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EN 12957:2001 (E)
EN 61000-6-2:1999 Electromagnetic compatibility (EMC) Part 6-2:Generic standards - Immunity
for industrial environments (IEC 61000-6-2:1999)
EN 61310-1:1995 Safety of machinery - Indication, marking and actuation - Part 1:
Requirements for visual, auditory and tactile signals (IEC 61310-1:1995)
EN 61310-2:1995 Safety of machinery - Indication, marking and actuation - Part 2:
Requirements for marking (IEC 61310-2:1995)
EN ISO 3746: 1995 Acoustics – Determination of sound power levels of noise sources using
sound pressure - Survey method using an enveloping measurement surface
over a reflecting plane (ISO 3746:1995)
EN ISO 4871: 1996 Acoustics – Declaration and verification of noise emission values of
machinery and equipment
EN ISO 11202:1995 Acoustics - Noise emitted by machinery and equipment - Measurement
method of emission sound pressure levels at the workstation and at other
specified positions - Survey method in situ
EN ISO 11688-1:1998 Acoustics – Recommended practice for the design of low noise machinery
and equipment – Part 1 Planning
3 Terms and definitions
For the purposes of this standard, the definitions given in EN 1070:1998 apply together with definitions listed
below.
Other general definitions (e.g. hazard, risk, safeguarding) are mentioned in corresponding type A and type B
Standards and in the annex A of EN 292-2:1991.
3.1
arc erosion; arc eroding; arc machining
the removal of material by constant (non pulsed) electro discharges, performed in a dielectric medium. The
discharges are initiated by periodical contact of the electrode with the work piece interrupted by axial
movement of the electrode
3.2
arc erosion equipment
all the necessary units for the process of arc machining
3.3
automatic mode
use of the machine under numerical control to achieve programmed sequential operation. This term is
equivalent with machining mode
3.4
control circuit
circuit used for the operational control of the machine and for protection of the power circuits
3.5
control system for EDM equipment or EDM system
the system from the initial actuator or sensor to the point of input to the final actuator or element (e.g. motor,
cylinders)
3.6
dielectric fluid (for EDM processes)
non-conductive medium to improve the discharge effect, evacuate debris and to cool the work
piece/electrode
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EN 12957:2001 (E)
3.7
dielectric fluid container
unit and/or systems used to keep the dielectric fluid in a condition suitable for EDM (e.g. filter unit/dielectric
system)
3.8
EDM equipment
all the necessary units for the process of electro discharge machining which includes the machine tool, the
generator, control circuits, the dielectric fluid container and integral devices
3.9
EDM system
an assembly of EDM equipment and other machines or devices which are arranged, linked and controlled to
function as an integral whole
3.10
electro chemical equipment
all the necessary units for the process of electro chemical machining
3.11
electro chemical machining; ECM
any machining process based on electrolysis
3.12
electro discharge machining; EDM
any machining process based on spark erosion
3.13
electromagnetic compatibility; EMC
the ability of the EDM equipment/system to function satisfactorily in its electromagnetic environment without
introducing intolerable electromagnetic disturbances to anything in that environment
3.14
flammable dielectric fluid
dielectric fluid used in EDM, characterised by its relative ease of ignition and relative ability to sustain
combustion
3.15
flash point
minimum temperature at which, under specified test conditions, a liquid gives off sufficient combustible gas or
vapour to ignite momentarily on application of an effective ignition source
3.16
generator (for EDM equipment)
device to convert electrical power supplied to the machine for the purpose of being used for spark erosion
processing
3.17
operator of an EDM equipment and/or system
person or persons given the task of programming, setting, adjusting, operating, maintaining and cleaning the
machinery
3.18
setting/manual mode
use of the machine for unprogrammed operations under the control of the operator
3.19
setting mode (simulation mode)
use of the machine under numerical control, without machining power, to check/optimise the NC-programme
and allowing manual interventions
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EN 12957:2001 (E)
3.20
shielding of EDM equipment
mechanical barrier or enclosure of conductive material intended to attenuate the emission/penetration of a
varying electromagnetic field into an assigned region
3.21
spark erosion; spark eroding; spark machining; EDM process
removal of material in a dielectric fluid by electro discharges, which are separated in time and randomly
distributed in space, between two electrically conductive electrodes (the tool electrode and the work piece
electrode), and where the energy in the discharge is controlled
3.22
spark erosion-sinking
removal of material by spark erosion to produce various shapes in the work piece e.g. concave, convex and
prismatic holes
3.23
spark erosion-wire cutting
removal of material by spark erosion with a wire electrode to produce prismatic shapes in the work piece
3.24
tool changer (for EDM equipment); electrode changing device
mechanism integrated with the machine to supply a previously loaded electrode in exchange for another
electrode. The electrode changing device is expected to enable an operator to load/unload electrodes from
outside the work area.
3.25
work area (on EDM equipment)
space within the envelope of the machine where the EDM process can take place
3.26
work piece changing device (for EDM equipment)
mechanism integrated with the machine to supply a previously loaded work piece in exchange for another
work piece. The work piece changing device is designed to enable an operator to load/unload work pieces
from outside the work area.
3.27
work tank (for EDM equipment)
unit surrounding the work area to contain the dielectric fluid for EDM processes
4 List of hazards
The list of hazards contained in Table 1 is the result of a risk assessment, carried out as described by EN
1050:1996 for all EDM equipment covered by the scope of this standard. The technical measures and
information for use contained in clause 5 and 7 are based on the risk assessment and deal with the identified
hazards by either eliminating them or reducing the effects of the risks they generate.
The significant hazards covered by this standard are listed in Table 1.
Particular attention is given to hazards dealing with:
Electrical hazards (electrode voltage).
Flammable dielectric fluid (level, temperature, fire detection).
Hazardous substances (waste disposal, filters, used dielectric fluid, fume extraction, electrodes and
sludges).
Electromagnetic emissions (radiated and conducted).
Note  The designer’s attention is focused on hazards which can occur during the life of the machine to both
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 EN 292-1:1991, 3.12) for both spark erosion with
automatic mode and operations requiring intervention (e.g. setting, maintenance, repair).Although acoustic
noise is not considered to be a significant hazard for EDM equipment, the manufacturer of the equipment is
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EN 12957:2001 (E)
not absolved from reducing noise and making noise declaration.The designer is cautioned to verify whether
the list of hazards in Table 1 is exhaustive and applicable and, if there are other hazardous situations, not
listed in Table 1, which are related to the specific equipment in question.
Table 1 - List of significant hazards and major sources of these hazards associated with Electro
Discharge Machines
* Description Hazardous situation Activity Danger zone Reference
action to Table 2
1 Mechanical hazards due to:
1d Mass and velocity movements of machine setting, at and near the A3 - A5
(kinetic energy of elements machining and machine
elements in maintenance
controlled or
uncontrolled
motion)
1.1 Crushing and work piece clamping loading/unloading, between clamps A1, A2, A3
reorienting
+ shearing and work piece
1.2
power operated,
automatic work envelope of work A1, A2, A3
piece/electrode work piece/ piece/electrode
changing electrode change motion
moving parts (e.g. axes, manual between work A1, A2, A3
operation/work
rolling elements) piece/electrode and
piece/electrode machine parts
change
1.4 Entanglement manual or automatic manual or power between work A1, A2, A3
work piece/electrode operated work piece/electrode and
changing, spindle piece/electrode machine parts
rotation and wire rollers changing and
spindle rotation
1.9 High pressure hydraulic/pneumatic setting, at and near the A4
fluid injection or systems ejection, machining and machine
ejection leakage and flushing maintenance
(continued)
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EN 12957:2001 (E)
Table 1 (continued)
* Description Hazardous situation Activity Danger zone Reference
action to Table 2
2 Electrical hazards due to:
2.1 Contact of contact with work process control, work piece, B1, B2
persons with live piece/electrode, setting and electrode, tooling
parts (direct wire/wire-path and maintenance fixture, generator
contact) contact with unprotected and electrical
circuits enclosure
2.2 Contact of per- contact with parts of the maintenance and at and near the B1, B3
sons with parts machine which are not service of the machine, insulation
which have be- live during normal machine of electrical cables
come live under operation and equipment
faulty conditions
(indirect contact)
7 Hazards generated by materials and substances (and their constituent elements) processed or
used by the machinery
7.1 Contact with or conditions near the during the EDM at and near the D1 - D5
inhalation of machine caused by process, setting, machine
harmful fluids, ejection of dielectric maintenance and
gases, mists, fluid, droplets or disposal of the
fumes, and dust evaporation, mists, machine
fumes, etc.
7.2 Fire or explosion fire hazard originated by during the EDM near the machine D5 - D12
flammable mist process and the work tank
generation, long lasting
arcing condition, loss of
dielectric fluid, fault of
electrical or hydraulic
power supply, etc.
10 Unexpected start-up, unexpected overrun/overspeed (or any similar malfunction) from:
10.2 Restoration of the malfunction of the ma- after energy at the machine E3
energy supply chine itself and/or elec- restoration
after an trical/pneumatic equip-
interruption ment due to restoration
of the energy supply
10.3 External malfunction of the machine in at and in the vicinity C1
influences on machine itself or operation, setting of the machine
electrical electrical equipment and maintenance
equipment due to electromagnetic
disturbances
13 Failure of the malfunction resulting all activities at the at all moving E1, E2
power supply from power loss, machine elements of the
powered clamping machine
failures and machine
elements moving under
residual forces (e.g.
inertia, gravity)
(continued)
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EN 12957:2001 (E)
Table 1 (concluded)
* Description Hazardous situation Activity Danger zone Reference
action to Table 2
14 Failure of the mechanical hazards during operation, at the machine F1
control circuit associated with ma- setting, cleaning,
chine movements, elec- maintenance and
trical hazard and/or fire repair activities
Other hazards
19 Slip, trip and fall ejection or spillage of during and after large work tanks, G1
of persons fluids and lubricants; machining and slippery floor and
(related to trailing floor-mounted or maintenance high working
machinery) loose connection cables positions; area
surrounding the
machine
20 Hearing loss or emission of hazardous during operation, at and in the vicinity H1
other noise from the EDM setting, cleaning, of the machine or
physiological equipment or its maintenance and the auxiliary
disturbances auxiliary devices repair activities devices
* This list is derived from EN 1050:1996, annex A
5 Safety requirements and/or measures
5.1 General requirements
Machinery shall comply with the safety requirements and/or protective measures as indicated in Table 2 of
this clause. In addition the equipment shall be designed according to the principles of EN 292 for hazards
relevant, but not significant, which are not dealt with by this standard (e.g. sharp edges).
5.2 Operating modes
5.2.1 Operating mode selection
Based on 1.2.5 of EN 292-2:1991/A1:1995 and 9.2.3 of EN 60204-1:1997, the selection of the mode shall be
either a key operated switch, or equally lockable means. Mode selection shall be permitted only from outside
the work area and shall not initiate start-up. The indication of the selected operating mode shall be provided
(e.g. the position of the selector, the provision of an indicating light or visual display indication). Mode
changes shall ensure, that only one mode is active at any one time.
Mode selection shall be category 1 according to EN 954-1:1996.
5.2.2 Protecting measures relating to operating modes
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EN 12957:2001 (E)
5.2.2.1 Automatic mode
Starting the automatic mode shall be possible only if guards are closed and other safety devices are in
protective condition (e.g. guard lock, fire detection device ready when flammable dielectric fluids are used
and fume extraction activated).
5.2.2.2 Setting mode
Suspension of safeguarding under setting mode has to be in accordance with 9.2.4 of EN 60204-1:1997.
Linear movements shall be limited at a maximum rate of 2 m/min under hold-to-run control, or incremental
movements at a maximum increment of 6 mm. The stop resulting from hold-to-run control release or end of
the incremental movement shall be a controlled stop category 2, according to 9.2.2 of EN 60204-1:1997.
-1
Rotating motions shall be limited to a rotation not exceeding 50 min .
Speed limit control shall be category B according to EN 954-1:1996, combined with either:
hold-to-run control together with an enabling device, or
manual data input (MDI) followed by a cycle start together with an enabling device, or
electronic hand-wheel together with an enabling device.
to achieve category 3 according to EN 954-1:1996.
The enabling device shall be in accordance with 9.2.5.8 of EN 60204-1:1997.
5.3 Stop functions
5.3.1 Operational stop
An operational stop-function which is initiated by a stop device shall be provided for each mode of operation.
When the operational stop function is activated, the energy supply to axes drive motors, work piece holding
device and NC equipment, need not be cut off, see A.1.2.4 of EN 292-2:1991/A1:1995 and annex A, Figure
A.5 of this standard.
5.3.2 Emergency stop
The EDM equipment or system shall be provided with one or more emergency stop control devices according
to EN 418:1992 and 6.1.1 of EN 292-2:1991.
The emergency stop function/s shall be category 1 according to 9.2.2 of EN 60204-1:1997.
For EDM equipment or systems without NC controlled axes (e.g. EDM equipment with single working axis
including electromechanical planetary motion devices or Electro Discharge Drilling machines), stop function
category 0 according to 9.2.2 of EN 60204-1:1997, may be applied.
Emergency stop shall be category 3 according to EN 954-1:1996.
Emergency stop device/s shall be provided at each working station but at least at:
the main control panel,
the portable control panel, if quick access to another emergency stop device is not possible,
the work piece/electrode loading and unloading station if separated from the main operator’s
position,
a location quickly accessible from inside of an enclosure and/or work tank where whole body
access is possible.
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EN 12957:2001 (E)
5.4 Safety related parts of control systems for EDM equipment or EDM systems
Safety related parts of control systems comprise parts concerning the following functions and shall fulfil the
requirements of the categories given below according to EN 954-1:1996.
Functions EN 954-1:1996 see ref. Table 2
category
Machining voltage and electrical sensing for positioning of 2B2
electrode/work piece
3 D7, D8, D9Monitoring of level and temperature of flammable dielectric
fluid
Fire detection 2D11
2 D11, D12Fume extraction shutter
BD4Fume extraction air flow sensing
BE3Start, stop and automatic restart of machining
BA3Hold-to-run control
2 A1, A2, A3, B2Interlocking of movable guards
3A3Enabling device
The function of safety related parts as specified above shall be verified by examination of circuit diagrams
and practical checks.
5.5 Specific requirements
Specific safety measures as needed for EDM equipment and/or EDM systems to prevent hazards identified in
clause 4 of this standard, are described in Table 2.
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EN 12957:2001 (E)
Table 2 - List of safety requirements and/or protective measures and their verification procedures
** Hazards Safety requirement and/or Verifi
...