ISO 21919-2:2021

INTERNATIONAL ISO
STANDARD 21919-2
First edition
2021-06
Physical device control — Interfaces
for automated machine tending —
Part 2:
Safety and control interface
Ensemble de commande pour les équipements — Interfaces pour le
chargement automatisé des machines —
Partie 2: Interface de sécurité et de commande
Reference number
ISO 21919-2:2021(E)
©
ISO 2021

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ISO 21919-2:2021(E)

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ISO 21919-2:2021(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Description of the interfaces . 2
4.1 General . 2
4.2 Characteristics of the interface . 3
4.2.1 General. 3
4.2.2 Conformance class . 3
4.2.3 Conformance options . 8
4.3 Safety interface .13
4.3.1 General.13
4.3.2 Principle approach and concept .13
4.3.3 Matrix for safety-related functional relationships .13
4.3.4 Distribution of performance levels and PFHD value .15
4.4 Control interface .16
5 Extension of the interfaces .16
5.1 General .16
5.2 Examples of project-specific extensions .16
5.2.1 General.16
5.2.2 Additional signals .16
5.2.3 More than one interference area .16
Annex A (normative) List of signals .17
Annex B (informative) Examples for safety matrices .18
Annex C (normative) Flow charts .31
Bibliography .44
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ISO 21919-2:2021(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 of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 184, Automation systems and integration,
Subcommittee SC 1, Physical device control.
A list of all parts in the ISO 21919 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 21919-2:2021(E)

Introduction
The ISO 21919 series describes interfaces for automated machine tending of at least one computer
numerically controlled (CNC) machine by using a machine tending system. These interfaces are the
link between automated machine tending systems and machines used for production. The automated
machine tending is initiated by either the machine tending system or by the machine.
ISO 21919-1 gives an overview and defines the fundamental principles on how the interfaces are set
up. It defines the necessary vocabulary and sets the syntax for the structure of signals. It distinguishes
between the safety interface, the control interface and project specific extensions.
Automated machine tending refers to the automatic loading or unloading of one or more machines by
using a machine tending system.
EXAMPLE Examples for machines are machine tools, typically computer numerically controlled (CNC),
metrology co-ordinate measuring machines (CMM), 3D structured light scanner (3DSL), and X-ray machines.
Examples for machine tending systems are robots, handling systems, gantrys, autonomous intelligent vehicles
(AIV), and automated guided vehicles (AGV).
Automated machine tending is a substantial element in highly productive industrial environments.
It is a complex endeavour. Necessary devices are complex systems by itself, are oftentimes provided
by different suppliers and encounter each other at the production site first time. For a trouble-free
collaboration of all units a clear definition of the interfaces is indispensable. For manufacturing systems
such standardized interfaces at an international level haven't been defined yet.
Therefore, the definition of the interfaces often is project-specific from the scratch or each supplier
tries to establish its in-house standards. These procedures cause great efforts, are prone to failure and
hence take a lot of time and manpower. As each interface is built individually and testing beforehand is
often not possible, commissioning times exceed the planned ones. Machine builders, system integrators
and production plant operators report these issues being substantial obstacles for such automation
projects.
Standardized interfaces lead to lean coordination processes, give higher planning reliability, shorten
times for commissioning and are less error-prone.
On the other hand, automated machine tending systems can be very complex systems and standards
need to be flexible enough to allow an adaption to the requirements of individual projects.
Applications are ranging from simple parts removal to material flow dedicated complex production
lines. It is noteworthy that the processing technologies of the machines are independent to the interface
and a majority of machine technologies can be integrated with the same standard.
Figure 1 and Figure 2 display the range of complexity of machine tending systems covered by the
ISO 21919 series. Figure 1 shows an example of a simple automated machine tending system, consisting
of a machine tool loaded by a conveyor.
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Figure 1 — Example of a simple automated machine tending system
Figure 2 shows an example of a complex production line with five computer numerically controlled
machine tools tended by a loading gantry.
Figure 2 — Example of a complex production line loaded by a gantry
In general, the interfaces for automated machine tending are composed of:
— mechanical;
— control-related; and
— safety-related connections.
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INTERNATIONAL STANDARD ISO 21919-2:2021(E)
Physical device control — Interfaces for automated
machine tending —
Part 2:
Safety and control interface
1 Scope
This document deals with the safety interface and control interface. It allocates signals to a conformance
class and/or conformance option. It describes the detailed functions of each signal, describes and
displays the timing interactions between signals in flow charts and shows examples for safety matrices
and safety-related functional relationships.
This document defines three conformance classes and dedicated conformance options. Classes and
options consist of a number of signals to:
— allow a flexible adaptation of the interface(s) to a project-specific scope of functions and
simultaneously;
— tie sets of signals tight enough to avoid unnecessary coordination efforts between suppliers of the
machine tending systems and machines.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
ISO 13849-1, Safety of machinery — Safety-related parts of control systems — Part 1: General principles
for design
ISO 21919-1, Automation systems and integration — Interfaces for automated machine tending — Part 1:
Overview and fundamental principles
IEC 62061, Safety of machinery – Functional safety of safety-related electrical, electronic and programmable
electronic control systems
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 21919-1 and the following
apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
emergency stop
function which is intended to
— avert arising or reduce existing hazards to persons, damage to machinery or to work in progress,
and
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— be initiated by a single human action
Note 1 to entry: ISO 13850 gives detailed provisions.
[SOURCE: ISO 12100:2010, 3.40]
3.2
guard
physical barrier, designed as part of a functional unit to provide protection
[SOURCE: ISO 12100:2010, 3.27, modified — In the definition, "the machine" has been changed to "a
functional unit". Notes 1 to 3 to entry have been removed.]
3.3
part family
all parts that a machine accepts for processing without a new set up
Note 1 to entry: A part family consists at least of one part.
4 Description of the interfaces
4.1 General
For an extensive description of the interfaces for automated machine tending, the following interfaces
shall be defined:
— safety interface;
— control interface.
Figure 3 shows the principle setup of the interfaces for automated machine tending.
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Figure 3 — Principle setup of the interface
4.2 Characteristics of the interface
4.2.1 General
The signals are grouped in conformance classes and conformance options for a flexible adaptation of
the interface to the project-specific sets of functions. Grouping allows individual characterization of the
interface while simultaneously meeting the requirements of this document.
For the application of this document, one conformance class shall be selected, all desired conformance
options can be selected, and a project specific extension can be defined.
The signals assigned to the relevant conformance class or the relevant conformance option shall be
made available at the interface if the characteristics on this conformance class/conformance option are
selected.
When realizing the interface, the signals shall correlate in the way shown in the relevant flow charts in
Annex C.
4.2.2 Conformance class
4.2.2.1 General
With the selection of a conformance class a basic set of signals is selected in order to fulfil the task of
automated machine tending.
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The following conformance classes are available. Only one conformance class shall be selected.
— Conformance class 1: Minimum set of signals.
— Conformance class 2: Extended set of signals.
— Conformance class 3: Extended set of signals with process optimization.
4.2.2.2 Conformance class 1: Minimum set of signals
4.2.2.2.1 General
At conformance class 1, the following functions can be realized:
— safety of people;
— simple unloading;
— simple loading;
— simple combined unloading and loading.
The word "simple" indicates that there is no distinction between coherent and non-coherent transfer
and that clamping functions are not handled via the interface.
Conformance class 1 is not applicable for machines that need coherent transfer.
4.2.2.2.2 Simple unloading
The function "simple unloading" serves the requirement to unload one part from the machine.
See the corresponding flow chart in Figure C.1.
4.2.2.2.3 Simple loading
The function "simple loading" serves the requirement to load one part to the machine.
See the corresponding flow chart in Figure C.2.
4.2.2.2.4 Simple combined unloading and loading
The function "simple combined unloading and loading" serves the requirement to unload one part from
the machine and then load another part after that. The time period between unloading and subsequent
loading is not defined.
However, the restriction applies that there shall be no machine movements required in the interference
area during the loading and unloading process. In this case, the automated machine tending system can
remain within the interference area.
See the corresponding flow chart in Figure C.3.
4.2.2.3 Conformance class 2: Extended set of signals
4.2.2.3.1 General
At conformance class 2, all functions of conformance class 1 and the following can be realized:
— unloading with non-coherent transfer, with/without clamping function;
— unloading with coherent transfer;
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— loading with non-coherent transfer, with/without clamping function;
— loading with coherent transfer;
— combined unloading and loading with non-coherent transfer, with/without clamping function;
— combined unloading and loading with coherent transfer;
— preparation of a part;
— emptying;
— functions of guard doors;
— further status information.
NOTE Conformance class 2 and conformance class 3 are typically implemented as bus interface as many
signals are handled.
4.2.2.3.2 Unloading with non-coherent transfer, with/without clamping function
Function "Unloading with non-coherent transfer, with/without clamping function" serves the
requirement to unload a part from the machine at non-coherent transfer.
See the corresponding flow chart in Figure C.4.
4.2.2.3.3 Unloading with coherent transfer
Function "Unloading with non-coherent transfer, with clamping function" serves the requirement to
unload a part from the machine at coherent transfer.
See the corresponding flow chart in Figure C.5.
4.2.2.3.4 Loading with non-coherent transfer, with/without clamping function
Function "Loading with non-coherent transfer, with/without clamping function" serves the requirement
to load a part from the machine at non-coherent transfer.
See the corresponding flow chart in Figure C.6.
4.2.2.3.5 Loading with coherent transfer
Function "Loading with coherent transfer" serves the requirement to load a part from the machine at
fixed transfer.
See the corresponding flow chart in Figure C.7.
4.2.2.3.6 Combined unloading and loading with non-coherent transfer, with/without clamping
function
Function "Combined unloading and loading with non-coherent transfer, with/without clamping
function" serves the requirement to unload a part from the machine at not fixed transfer and then load
another part to the machine. The time period between unloading and subsequent loading is not defined.
See the corresponding flow chart in Figure C.8.
4.2.2.3.7 Combined unloading and loading with coherent transfer
Function "Combined unloading and loading with coherent transfer, with/without clamping function"
serves the requirement to unload a part from the machine at coherent transfer and then load another
part to the machine. The time period between unloading and subsequent loading is not defined.
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See the corresponding flow chart in Figure C.9.
4.2.2.3.8 Preparation of a part
Function "Preparation of a part" is used to inform the automated machine tending system at an early
stage that there is no part at the loading space of the machine or that the machine will complete
processing shortly.
4.2.2.3.9 Emptying
Function "Emptying" serves the requirement to unload all parts from the machine.
Emptying can be requested from the automated machine tending system to the machine, e.g. if there
are no new raw parts.
If the machine needs to have all parts unloaded, it shall send a request to the automated machine
tending system. Automated machine tending system decides when the machine can be unloaded and
acknowledges the request by setting its request for emptying. Up to this point, the machine shall
request loading cycles.
See the corresponding flow chart in Figure C.10.
4.2.2.3.10 Function of guard doors
The functions of the guard doors serve the requirement to unlock the guard door(s), if necessary. Here,
distinction shall be made whether the guard door is assigned to the automated machine tending system
or to the machine. It can also be differentiated if a request for unlocking the guard door remains until
the guard door has actually been unlocked or if the request has prematurely been withdrawn.
Figure C.11 differentiates between the two cases and shows the corresponding flow charts.
4.2.2.3.11 Further status functions
Conformance class 2 contains further signals which provide information at the interface.
4.2.2.4 Conformance class 3: Extended set of signals with process optimization
4.2.2.4.1 General
At conformance class 3, all functions of conformance class 2 and the following can be realized:
— process optimizations at the combined unloading and loading with coherent transfer;
— process optimizations at the combined unloading and loading with non-coherent transfer, with/
without clamping function;
— process optimizations, if pre-positioning by the machine;
— process optimizations, if clamping and releasing is executed in more than one step.
4.2.2.4.2 Process optimizations at combined unloading and loading
4.2.2.4.2.1 General
Description of pre-positioning by the automated machine tending system.
Figure 4 displays the principle coherence of different typical areas of machine and automated machine
tending system and its interactions.
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Key
1 range of automated machine tending system
2 range of machine
3 interference area preposition automated machine tending system
4 interference area
5 location of transfer station
6 interference area preposition machine
Figure 4 — Interference area at pre-positioning by automated machine tending system
Involved signals are AM_ENA_InIntfrArea, AM_STA_OutIntfrArea, AM_STA_OutIntfrAreaFixt, MA_
ENA_InIntfrArea, MA_ENA_InIntfrAreaPrePos, and MA_STA_OutIntfrArea. For definition of these
signals, see Annex A.
4.2.2.4.2.2 With coherent transfer
The process optimizations at the combined unloading and loading with coherent transfer function
unloads a part from the machine at coherent transfer and then load another part to the machine. The
time period between unloading and subsequent loading is not defined.
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In addition to conformance class 2, process optimizations (optimization of cycle time) are carried out
concerning:
— pre-positionings;
— preparation of unloading part(s).
See the corresponding flow chart in Figure C.13.
4.2.2.4.2.3 With non-coherent transfer, with/without clamping function
Function "Combined unloading and loading with non-coherent transfer, with/without clamping
function" serves the requirement to unload apart from the machine at non-coherent transfer and then
load another part to the machine. The time period between unloading and subsequent loading is not
defined.
In addition to conformance class 2, process optimizations (optimization of cycle time) are carried out
concerning:
— pre-positionings;
— preparation of unloading part(s).
See the corresponding flow chart in Figure C.12.
4.2.2.4.3 Process optimizations, if pre-positioning by machine
In conformance class 3, signals are provided for process optimizations which require a pre-positioning
of the machine. A process description shall be coordinated specifically to the project and depending on
the mechanical design.
4.2.2.4.4 Process optimizations, if clamping and releasing is executed in more than one step
In conformance class 3, signals are provided for process optimizations which require clamping and
releasing in more than one step. A process description shall be coordinated specifically to the project
and depending on the mechanical design.
4.2.3 Conformance options
4.2.3.1 General
The selection of a conformance option allows adding an additional scope of functions to the selected
conformance class. The set of signals allocated to a conformance option is intended to fulfil a specific
task.
The following conformance options are available. Any desired conformance option can be selected.
— loading access controlled by machine;
— loading access controlled by automated machine tending system;
— enabling device;
— monitoring of communication;
— tool life management;
— central functions;
— control signals for safety-relevant functions;
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— with parts data;
— setup information;
— machine panel;
— part seat control.
Table 1 shows if a conformance option contains safety-relevant and/or control-relevant signals.
Table 1 — Allocation of safety-relevant and control-relevant signals to conformance options
Conformance option Safety-relevant signals Control-relevant signals
 
Loading access controlled by machine
Loading access controlled by automat-
 
ed machine tending system
Enabling device  
Monitoring of communication 
Tool life management 

Central functions
Control signals for safety-relevant

functions
With parts data 
Setup information 
Machine panel 
Part seat control 
4.2.3.2 Conformance option: Loading access controlled by machine
The signals assigned to the conformance option "Loading access controlled by machine" in Annex A
shall be provided at the interface.
The conformance option "Loading access controlled by machine" includes signals with the belonging
functions required if a loading access is controlled by the machine.
Handling the signals is analogous to the description and diagrams of the guard doors.
4.2.3.3 Conformance option: Loading access controlled by automated machine tending system
The signals assigned to the conformance option "Loading access controlled by automated machine
tending system" in Annex A shall be provided at the interface.
The conformance option "Loading access controlled by automated machine tending system" includes
signals with the belonging functions which are required if a loading access is controlled by the
automated machine tending system.
Handling the signals is analogous to the description and diagrams of the guard doors.
4.2.3.4 Conformance option: Enabling device
The signals assigned to the conformance option "Enabling device" in Annex A shall be provided at the
interface.
The conformance option "Enabling device" includes signals with the belonging functions which are
necessary for operating the system in enabling mode.
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4.2.3.5 Conformance option: Monitoring of communication
The signals assigned to the conformance option "Monitoring of communication" in Annex A shall be
provided at the interface.
The conformance option "Monitoring of communication" includes signals with the belonging functions
which are necessary for the monitoring of communication. Each functional unit sends a binary signal
to the interface with a pulse of 1 Hz. The other functional unit evaluates this signal and detects if the
communication is disturbed or alright.
See the corresponding flow chart in Figure C.14.
4.2.3.6 Conformance option: Tool life management
The signals assigned to the conformance option "Tool life management" in Annex A shall be provided at
the interface.
The conformance option "Tool life management" includes sign
...