ISO/IEC TR 24720:2008

TECHNICAL ISO/IEC
REPORT TR
First edition
2008-06-01
Information technology — Automatic
identification and data capture
techniques — Guidelines for direct part
marking (DPM)
Technologies de l'information — Techniques automatiques
d'identification et de capture des données — Lignes directrices pour
DPM («direct part marking»)
Reference number
©
ISO/IEC 2008
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.

©  ISO/IEC 2008
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO/IEC 2008 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 Abbreviated terms . 2
5 Overview of DPM. 2
5.1 DPM methods. 2
5.2 Reasons for utilizing DPM . 3
6 Marking method selection . 3
7 Marking methods . 6
8 Cleaning. 6
9 Marking surface preparation . 6
9.1 Assessment. 6
9.2 Protective coatings. 7
10 Human readable marking. 8
11 Symbol quality . 8
12 Reading and grading DPM symbols . 9
13 Verification . 9
13.1 General. 9
13.2 Configuration . 9
13.3 Possible equipment setup . 10
14 Imagers for direct part marking applications . 11
14.1 General description . 11
14.2 Fixed-mount imagers. 11
14.3 Presentation imager . 12
14.4 Hand-held imager. 12
Annex A (informative) Intrusive marking methods . 14
A.1 Intrusive marking. 14
A.2 Re-marking requirements using intrusive marking methods . 15
A.3 Laser marking . 15
A.4 Dot peen marking. 18
A.5 Other Intrusive marking methods . 20
Annex B (informative) Non-intrusive marking methods. 22
B.1 Non-intrusive marking methods. 22
B.2 Ink jet marking. 22
B.3 Fabric embroidery/weaving . 25
B.4 Forge, cast. 26
B.5 Laser bonding . 27
B.6 Laser engineered net shaping (LENS). 27
B.7 Screen printing. 28
B.8 Stencil . 29
Annex C (informative) Rockwell Hardness . 30
Bibliography . 32
© ISO/IEC 2008 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
In exceptional circumstances, the joint technical committee may propose the publication of a Technical Report
of one of the following types:
— type 1, when the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts;
— type 2, when the subject is still under technical development or where for any other reason there is the
future but not immediate possibility of an agreement on an International Standard;
— type 3, when the joint technical committee has collected data of a different kind from that which is
normally published as an International Standard (“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether
they can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to
be reviewed until the data they provide are considered to be no longer valid or useful.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC TR 24720, which is a Technical Report of type 3, was prepared by Joint Technical Committee
ISO/IEC JTC 1, Information technology, Subcommittee SC 31, Automatic identification and data capture
techniques.
iv © ISO/IEC 2008 – All rights reserved

Introduction
Identification technologies have become an essential part of managing the life cycle of manufactured goods,
from their "birth" to the scrap recovery process. The need to identify parts easily and correctly is critical for
controlling and error proofing the assembly process, tracking work in process and building traceability. Fast
and accurate identification methods are also important after the product leaves the plant.
Industries worldwide rely heavily on the use of various marking methods. Because many of these methods
were originally designed to apply human-readable marks, they frequently are not appropriate for applying
high-density machine-readable symbols.
With the widespread implementation of machine-readable marking, the parts identification industry began to
refine existing marking methods. Dot peen machines replaced manual metal stamping and embossing
techniques. Desktop publishing systems were developed for the production of stencils. Ink jet machines were
built to replace rubber stamps. Laser marking systems were designed to replace electric-arc etching and hot
stamping processes.
One of the most popular methods of identifying a part is with a two-dimensional (2D) symbol applied directly
onto the surface of parts. Compared with printing and applying labels, marking directly on parts is more secure,
more cost-effective and easier to automate. When direct marked, two-dimensional symbols are able to
withstand harsh manufacturing processes and abuse in the field.
Several direct part marking (DPM) technologies are addressed in this Technical Report, such as ink jet
printing, laser etch, chemical etch and dot peen marking. Ink jet printing is one of the least expensive of the
marking methods. Laser etch is popular because of its ability to produce small, precise marks, and the ability
of lasers to mark symbols on many materials, from hardened steel to soft plastic. Lasers can also access
small, tight locations. Dot peen marking is usually reserved for marking metal. This marking method uses a
stylus to indent the surface of the part to create the desired mark. Chemical etch marking is often used to
mark printed circuit boards (PCBs), since it is already part of the normal manufacturing process.
For the purposes of this Technical Report, direct part marking (DPM) is considered a generic term referring to
methods of applying a permanent mark directly onto a surface of an item. There are two generic direct
marking techniques described in this Technical Report: intrusive and non-intrusive.
Intrusive (or subtractive) marking methods alter the surface of a part and are considered controlled defects. Of
the intrusive marking methods, this Technical Report addresses dot peen and direct laser marking, and briefly
describes other technologies.
Non-intrusive marking methods, also known as additive markings, are produced as part of the manufacturing
process or by adding a layer of media to the surface of a part. Of the non-intrusive methods, this Technical
Report addresses ink jet marking and other technologies.

© ISO/IEC 2008 – All rights reserved v

TECHNICAL REPORT ISO/IEC TR 24720:2008(E)

Information technology — Automatic identification and data
capture techniques — Guidelines for direct part marking (DPM)
1 Scope
This Technical Report describes several methods for applying permanent machine-readable symbols to
items – including components, parts and products – using the direct part marking (DPM) methods outlined
herein. This Technical Report describes marking methods, marking surface preparation, marking location,
protective coatings and other parameters that contribute to the production of quality symbols, but does not
specify the information to be encoded.
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.
ISO/IEC 19762-1, Information technology — Automatic identification and data capture (AIDC) techniques —
Harmonized vocabulary — Part 1: General terms relating to AIDC
ISO/IEC 19762-2, Information technology — Automatic identification and data capture (AIDC) techniques —
Harmonized vocabulary — Part 2: Optically readable media (ORM)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 19762-1, ISO/IEC 19762-2 and
the following apply.
3.1
intrusive marking
marking method designed to alter a surface to form a human- or machine-readable symbol
NOTE This marking category includes, but is not limited to, methods that abrade, burn, corrode, cut, deform, dissolve,
etch, melt, oxidize or vaporize a surface. Intrusive marking methods include stamping, laser etching, chemical etching, dot
peen and micro-sandblast.
3.2
non-intrusive marking
marking method designed to add material to a surface to form a human- or machine-readable symbol
NOTE Non-intrusive marking methods include ink jet, some forms of laser bonding, liquid metal jet, screen process,
stencil and thin film deposition.
3.3
permanent marking
intrusive or non-intrusive markings designed to remain legible for at least the normal service life of an item,
subject to operating or usage conditions
© ISO/IEC 2008 – All rights reserved 1

4 Abbreviated terms
EDM Electrical Discharge Machine or Machining
LISI Laser Induced Surface Improvement
5 Overview of DPM
5.1 DPM methods
For the purposes of this Technical Report, direct part marking (DPM) is considered a generic term referring to
methods of applying a mark directly onto the surface of an item. There are two techniques for applying a mark,
intrusive and non-intrusive.
5.1.1 Intrusive
Intrusive (also known as “subtractive”) marking methods physically alter the surface or structure of a part
(abrade, cut, burn, vaporize, bond etc.) and the marks are considered controlled defects. It is highly
recommended that all item identification manufacturing methods should be controlled by appropriate
manufacturing instructions, approved by Engineering Design and that testing of materials should be
conducted before an intrusive mark is applied to an item. Typical intrusive marking methods include:
• Abrasive blast
• Direct laser marking
• Dot peen
• Electro-chemical marking
• Engraving/milling
• Fabric embroidery/weaving
• Stamping
Of these intrusive methods, this report addresses some forms of direct laser and dot peen marking, and briefly
refers to other marking technologies.
5.1.2 Non-intrusive
Non-intrusive (also known as “additive”) markings are produced as part of the manufacturing process or by
adding a layer of marking media to the surface using methods that have no adverse effect on material
properties. These methods include:
• Automated adhesive dispensing
• Cast, forge, and mold
• Ink jet
• Laser bonding (limited forms)
• Laser engineered net shaping (LENS)
• Liquid metal jet
• Screen printing
• Stencil (not when used by Electro Chemical Etch marking methods)
Of the non-intrusive marking methods, this report addresses ink jet marking in depth and other technologies
only briefly.
2 © ISO/IEC 2008 – All rights reserved

5.2 Reasons for utilizing DPM
• If traceability is required after the product is separated from its temporary identification.
• When the part cannot be marked with labels or tags.
• If the part will be subjected to environmental conditions that preclude the use of add-on identification
methods.
• When the use of DPM methods is more cost efficient than applying individual item labels.
• When identification is required for the anticipated life cycle of the part, as defined by the manufacturer.
6 Marking method selection
The overall quality of any form of part identification depends on several characteristics. These characteristics
can include the material being marked, the shape or geometry of the marking surface and any surface
coatings or discoloration that affects decode or readability of the mark.
It is, therefore, important to review all of these factors before selecting a marking method. If a component
definition instructs a specific marking method for that component, that method should always be selected.
Table 1 below provides a cross-reference of marking methods and commonly marked materials and provides
guidance for selecting marking methods appropriate for the listed materials.
© ISO/IEC 2008 – All rights reserved 3

Table 1 — Marking Method Selection

METALLICS NON-METALLICS
MATERIAL TO BE
MARKED
MARKING
PROCESS
Abrasive Blast • • • • • • • • • • •
Adhesive Dispensing • • • • • • • • • • 1 • • • •
Cast, Forge Or Mold • • • • • • • • •  • •
Dot Peen •  1 • • •  1 1
Electro-Chemical Coloring • • • • • • • •
Electro-Chemical Etching
• • • • • • • •
Embroidery
•
Engraving/Milling
• • • • •   1 •  •
Ink Jet 1
• • • • • • • • • • • • •  •
Laser Bonding • • • • • • • •  •
Laser - Short Wave Lengths • 1 • • • • • • • 1 • • • • •
Laser Visible Wave Lengths 1 1 • 1 •   1 •  •
Laser – Long Wave Lengths 1    • • 1  • •
LENS • 1 • • • • • •
LISI
2  2 2
• • •
Silk Screen • • • • • • • • • • • • • • •
Stencil • • • • • • • • • • • • • •
Thin Film Deposition • • • • • • • • • •  • •

• = Acceptable marking process for this material if marking location and marking parameters are agreed
1 = Additional technical input required from design authority and equipment / material suppliers
2 = Marking method under development for this material
Blank space = Marking method not recommended for this material0

The physical size of the item to be marked is also a factor in DPM. When available marking space falls below
an accepted size, it may be necessary to review the data string and/or select a different marking method that
is acceptable to the component definition and/or operating condition. Table 2 below provides additional
guidance in the selection of an appropriate marking process.

4 © ISO/IEC 2008 – All rights reserved

Aluminum
Anodized
Beryllium
Carbon Steel
Copper
Brass
Magnesium
Titanium
Ceramics
Glass
Cloth
Painted
Plastics
Rubber
Teflon
Wood
Epoxy-glass
© ISO/IEC 2008 – All rights reserved 5
Table 2 — Symbol sizes by marking process

Data Format
P/N, EI and EI and S/N -
S/N Only -
S/N - Typically 13 Characters
Marking Process
Typical Data Cell Size Typically 7 Characters
Symbol Size Categories
Typically 29 Characters (18x18 Matrix)
(12x12 Matrix)
(Assenting Order)
(24x24 matrix)
Micro - <0.008-inch Laser Marking – Short 0.004 inch (0,102 mm)
0.0002 inch (0,005 mm) 0.003 inch (0,076 mm) 0.002 inch (0,051 mm)
Wave Length (Excimer)
(0,203 mm) data cells
Typical - 0.08 inch LaserShot Peening 0.009 inch (0,238 mm) 0.216 inch (5,486 mm) 0.162 inch (4,115 mm) 0.108 inch (2,743 mm)
(2,032 mm) to 0.034 Stencil(Photo-Process)
0.010 inch (0,254 mm) 0.240 inch (6,096 mm) 0.180 inch (4,572 mm) 0.120 inch (3,048 mm)
(0,864 mm) data cells
Laser Bonding
0.010 inch (0,254 mm) 0.240 inch (6,096 mm) 0.180 inch (4,572 mm) 0.120 inch (3,048 mm)
Laser Marking 0.010 inch (0,254 mm) 0.240 inch (6,096 mm) 0.180 inch (4,572 mm) 0.120 inch (3,048 mm)
Stencil(Mechanical Cut)
*0.020 inch (0,508 mm) 0.480 inch (12,192 mm) 0.360 inch (9,144 mm) 0.240 inch (6,096 mm)
Adhesive Dispensing 0.020 inch (0,508 mm) 0.480 inch (12,192 mm) 0.360 inch (9,144 mm) 0.240 inch (6,096 mm)
Dot Peen*
*0.022 inch (0,558 mm) 0.528 Inch (13,411 mm) 0.396 inch (10,058 mm) 0.264 inch (6,706 mm)
LISI
0.024 inch (0,610 mm) 0.576 inch (14,630 mm) 0.432 inch (10,973 mm) 0.288 inch (7,315 mm)
Stencil (Laser Cut) *0.024 inch (0,610 mm) 0.580 inch (14,732 mm) 0.440 inch (11,176 mm) 0.288 inch (7,315 mm)
Abrasive Blast
0.025 inch (0,635 mm) 0.600 inch (15,240 mm) 0.450 inch (11,430 mm) 0.300 inch (7,620 mm)
Ink Jet 0.030 inch (0,762 mm) 0.720 inch (18,288 mm) 0.540 inch (13,716 mm) 0.360 inch (9,144 mm)
Engraving/Milling
Macro – ≥0.035 inch *0.040 inch (1,016 mm) 0.960 inch (24,384 mm) 0.720 inch (18,288 mm) 0.480 inch (12,192 mm)
(0,889 mm)
Fabric Weaving
0.040 inch (1,016 mm) 0.960 inch (24,384 mm) 0.720 inch (18,288 mm) 0.480 inch (12,192 mm)
LENS 0.040 inch (1,016 mm) 0.960 inch (24,384 mm) 0.720 inch (18,288 mm) 0.480 inch (12,192 mm)
Fabric Embroidery
0.045 inch (1,143 mm) 1.080 inch (27,432 mm) 0.810 inch (20,574 mm) 0.540 inch (13,716 mm)
Cast, Mold & Forge 0.060 inch (1,524 mm) 1.440 inch (36,576 mm) 1.080 inch (27,432 mm) 0.720 inch (18,288 mm)
Note: Table courtesy NASA-STD-6002B and is reproduced here verbatim.
* Includes spacing between data cells
Note: See Annex A and Annex B for descriptions of marking methods.
Note: Technology developments in the marking processes are continuously improving the resolution that is achievable using that process. It should be noted, however, that some equipment might
achieve better or worse results than those indicated in Table 2.

7 Marking methods
For most two-dimensional symbols to be read successfully, the decoding software requires a quiet zone (a
clear space of a specified minimum width) around the entire periphery of the symbol. In addition to this
requirement, manufacturers often impose additional marking location restrictions within their drawings and/or
specifications. This report recommends that care be exercised when marking in the following locations:
• Highly polished curved surfaces
• In direct air streams (e.g., leading edge of wings, helicopter rotors, exposed portions of turbine blades,
etc.)
• Near high heat sources
• Sealing surfaces
• Wearing surfaces
In addition, the effects of adjacent structures on the imager’s illumination source must be considered. Fixed
station imagers with movable light sources can usually be configured to illuminate symbols placed in recesses
or adjacent to protruding structures. These structures, however, can pose a challenge for hand-held imagers
with fixed positioned light sources. It is therefore advisable to read marked parts in places that provide
maximum access to lighting.
8 Cleaning
Cleaning processes used for removing soil and contamination from parts to be marked are varied, and their
effectiveness depends on the requirements of the specific application. The appropriate cleaning method
should be selected according to the needs of the specific application. In selecting a cleaning process, many
factors must be considered, including:
• The nature of the soil to be removed
• Substrate to be cleaned (e.g. ferrous, non-ferrous, etc.)
• Importance of the condition of the surface to the end use of the part
• Degree of cleanliness required
• Capabilities of the available facilities
• Environmental impact of the cleaning process
• Cost
• Total surface area to be cleaned
• Effects of previous processes
• Rust inhibition requirements
• Material handling factors
• Surface requirements of subsequent operations, such as phosphate conversion coating, painting, or
plating
9 Marking surface preparation
9.1 Assessment
Prior to marking, operators are required to determine if additional surface preparation is required. This
assessment should address:
• Surface finishes that cause excessive amounts of shadow and/or specular reflection
• Surfaces that do not provide the necessary contrast for decoding
• Safety critical parts that cannot be marked using intrusive marking methods
• Materials that are not suitable for marking with the user’s preferred marking method
The most common methods utilized to prepare surfaces for marking are additives and coatings.
6 © ISO/IEC 2008 – All rights reserved

9.1.1 Additives
To assist readability of the mark, specialized additives can be mixed with metal alloys and thermoplastic
formulations to enhance and optimize marking contrast. These additives increase the ability of the material to
absorb or reflect specific wavelengths of light, but do not generally affect overall material performance.
9.1.2 Coatings
In a limited number of applications, it is possible for coatings to be used to modify the surface of a part to
improve readability and/or to provide corrosion protection. Coatings can be utilized to aid part marking by:
• Smoothing rough surfaces to reduce the effects of shadowing
• Providing increased contrast for surfaces of parts that inherently provide insufficient contrast
• Dulling highly polished surfaces to reduce specular reflection
• Providing a surface that can be removed with intrusive markings to expose a substrate of contrasting
color
• Serving as a medium for marking using a stencil as a mask
Following are the processes most commonly used to coat surfaces prior to marking:
9.1.3 Dip, Barrier and Conversion Coating
“Dip, barrier, and chemical conversion coating” is a term that encompasses an entire family of processes used
to prevent corrosion. The appropriate method should be selected according to the needs of the application.
9.1.4 Laser induced surface improvement (LISI)
LISI is a laser process utilized to impart stainless properties to carbon steel. The process can also be used to
improve the wear characteristics of aluminum surfaces. LISI treated surfaces can be discolored or removed to
create a symbol.
9.1.5 Plating and electroplating
Plating and electroplating processes are divided into two categories: Electro-deposition and Non-electrolytic
deposition processes. These techniques should be selected according to the needs of the application.
9.1.6 Vacuum controlled-atmosphere coating and surface modification processes
“Vacuum and controlled-atmosphere coatings” is a general term that encompasses thermal spray, chemical
vapor deposition, physical deposition, diffusion, and pulsed-laser deposition processes. This family of
processes is used to modify surfaces by depositing material onto a surface that is subsequently marked.
Vacuum controlled-atmosphere coatings and surface modification processes are frequently used in
conjunction with stencil marking.
9.1.7 Machining
Because extremely rough surfaces can produce shadows that adversely affect reader performance,
machining is often performed to smooth the surface roughness of parts to be marked. A number of machining
methods are commonly used for surface smoothing, and the appropriate method should be selected
according to the needs of the application.
9.2 Protective coatings
Metals are often unstable and susceptible to degradation by corrosion from hostile environments. Protective
coatings are often applied to marked surfaces to protect the marking and prevent corrosion. It should be noted,
however, that surface coatings might adversely affect the performance of some types of mark.
© ISO/IEC 2008 – All rights reserved 7

Intrusive markings applied to a surface that has been previously coated should be re-coated to prevent
corrosion in or around the area of the marking.
Note that a protective coating may alter the specular characteristics of the part and the optical quality should
be measured in its final configuration. Typical coatings include, but are not limited to, the following:
9.2.1 Clear anodize
Anodizing is an electrolytic oxidation process in which the surface of the metal is converted to a coating
having desirable protective, decorative, or functional properties.
9.2.2 Lacquer
Lacquer is a coating formulation based on thermoplastic film-forming material dissolved in an organic solvent.
The coating dries primarily by evaporation of the solvent.
9.2.3 Thin film deposition
Thin film deposition is a technique for depositing a thin film of material onto a substrate or onto previously
deposited layers of material. This process may be used to aid in adhesion or substrate cleaning or to smooth
surface roughness prior to marking.
10 Human readable marking
Whenever possible, the data encoded in the symbol should be marked in human readable form for use when
code-reading devices are not available or when a symbol is unreadable. Human readable characters can be
applied using the marking methods defined in this Technical Report, so whenever practical, the human
readable and symbol marking should be applied simultaneously and by the same method. Human readable
markings, when used, should be applied in close proximity to the two-dimensional symbols, as demonstrated
in Figure 1 below.
Figure 1 — Human readable marking in close proximity to two-dimensional symbol
11 Symbol quality
The quality of direct marking is affected several factors, including the material to be marked, the selected
marking method and component operating conditions.
See Table 1 of this report for guidance in matching the marking method and selected materials appropriately.
Methodologies for measuring the print quality of machine-readable marks using DPM procedures are not
available.
8 © ISO/IEC 2008 – All rights reserved

12 Reading and grading DPM symbols
The ultimate purpose of DPM that produces a machine-readable symbol is for a scanner to be able to read the
symbol. Historically, marks were either scanned in a fixtured environment custom-tailored for each mark or not
scanned at all. Application standards generally specified marks in terms of mechanical and dimensional
properties. "Marks,” meaning dimensionally accurate patterns which change a substrate using methods
described in this document, become "symbols", meaning the light reflecting from the combination of the mark
and the substrate, intended to be read by a scanner in an application. Depending on many factors, sometimes
a great "mark" is not a good "symbol".
As more actual scanning became the norm, many marks that were mechanically correct failed to scan in
application environments. Good marks may not scan if the background has either too much texture or not
enough, if inks are the wrong color or any number of other marking combinations occurs such that the lighting
and scanning configuration of the application do not match the optical properties of the symbol. On the other
hand, in some cases, marks that scanned easily were not deemed acceptable from a dimensional standpoint.
This lack of scanning predictability lead to considerable technological development in the area of camera
based symbol quality evaluation, sometimes called "verification" (see Verification Section 13).
As of the writing of this document, there is a mix of mechanical and optical-based quality measurement
methods that are specified by various industries. It is important for the engineer who specifies the symbol and
for the manufacturer who creates the symbol to make sure that they are designing and marking to the latest
version of the industry application specification that covers the eventual scanning environment of the symbol.
For this reason it is only possible to produce a machine-readable symbol to meet physical geometry
definitions and not to the requirements of any particular imaging device. It is important to stress, given the
correct imaging device, that mark quality is the consideration and readability is the output.
Reading considerations for the marking methods included in this report are outlined in the guidelines provided
in Annex A and Annex B.
13 Verification
13.1 General
In order to assure that the marking equipment applies a machine-readable symbol that will meet the
requirements for achieving the highest read rates, it is highly recommended that a form of acceptance be
carried out for mark quality acceptance. Not only is this an important factor for downstream reading
performance, but it reduces costs associated with rejected parts due to unreadable codes. If a part loses its
identity due to the poor quality of the mark, it cannot be used. A verification system will immediately detect a
problem, which could be due to poor fixing of the part, damage to the machine such as a broken stylus tip on
a dot peen machine or incorrect settings during part changeover.
13.2 Configuration
A symbol verifier is a system that includes lighting, optics, camera, symbol verification software, and
calibration. Due to the various types of materials, surface conditions and marks a verification system for DPM
symbols, based on the scanning requirements, needs to be defined for each application.
Lighting and optics should be configured to ensure an optimal image formation that delivers good contrast with
adequate resolution. In order to have meaningful verification results, it is recommended that the resolution at
the verification station be at least twice that of the reading station resolution. This can be accomplished with
either higher magnification optics or an imaging device in which the resolution is twice that of the reading
devices to be used. Another important step in generating consistent and meaningful results is consistent part
presentation.
© ISO/IEC 2008 – All rights reserved 9

13.3 Possible equipment setup
As an example, the arrangement described here and illustrated in Figure 2 and Figure 3 below may be found
suitable for many open applications. A standard monochrome video camera images the test symbol directly
on axis with its centre and normal to its plane. The lens used is appropriate to frame the entire symbol
(including any required quiet zones) in good focus, and with a sufficiently small field of view to minimize optical
distortions whilst also ensuring that the effective resolution obtained is appropriate to the X dimension of the
symbol. Light illumination uniformly floods the symbol area with a 45° angle of incidence. Test images are
captured with 8-bit grey-scale digitization using standard frame capture equipment, and the grey-scale is
calibrated using targets of known diffuse reflectance.
A
B
ϑ ϑ
1 – Light sensing element
2 – Lens providing 1:1 magnification (measurement A = measurement B)
3 – Inspection area
4 – Light sources
ϑ - Angle of incidence of light relative to plane of symbol (default = 45°, optionally 30° or 90° diffuse)
Figure 2 — Reference optical arrangement, side view
10 © ISO/IEC 2008 – All rights reserved

Figure 3 — Example of a quality testing setup. Marking quality verifiers are available
from multiple sources
14 Imagers for direct part marking applications
14.1 General description
There are three types of imager (decoder) products for DPM in general use today: fixed-mount imagers,
presentation imagers, and hand-held imagers. Imaging systems include:
• a means of illuminating the symbol
• optics for focusing an image of the symbol on a detector
• software for processing the image and decoding the symbol
• an output device, either a display or interface to a data processing system
14.2 Fixed-mount imagers
Fixed-mount imagers are used in reading symbols on parts that are handled and moved automatically by
conveyor, indexer, or robot. Typically, fully automated manufacturing lines such as those found in electronics
and automotive manufacturing use fixed-mount imagers.
In operation, this type of imager (Figure 4) is mounted in a fixed position where the symbol can be repeatedly
placed in front of the imager in either continuous or indexed motion. The imager is signaled that the part is
ready for reading by a “trigger”. This trigger event is performed by an external sensor that detects the
presence of the part or by an encoder that knows the position of the part at all times and can signal the imager
to decode.
© ISO/IEC 2008 – All rights reserved 11

Fixed-mount imagers are configured with either an integrated light source or with an external light source as
required by the application. Advantages of a fixed-mount imager without an integrated light source are that it
can be mounted at varied distances from the part and supplemental lighting can be selected to meet the
application needs.
Figure 4 — Example of a fixed-mount imager
14.3 Presentation imager
Similar to a fixed-mount imager, a presentation imager (Figure 5) is mounted in a fixed position; however, it
operates in a continuous reading cycle, automatically performing the decoding task once the operator places
the part bearing the symbol in front of the imager. Presentation imager can provide a very fast way of reading
symbols in areas where parts are handled manually. A presentation imager can be implemented with either a
fixed-mount or a hand-held imager. Using a hand-held imager in presentation mode provides the opportunity
for multi-use, as one can also remove the imager from its stand and bring it to the part.

Figure 5 — Example of a presentation imager
14.4 Hand-held imager
Hand-held imagers (Figure 6 below) are typically used in applications where the symbol size is fixed and the
part is too large or it is difficult to bring the part to the imagers. Variable or multiple lens imagers are used in
applications in which two-dimensional symbols of more than one size are to be read.
Hand-held imagers are preferred in those environments where part handling is not automated or parts vary
greatly in size. Handhelds are used in job shop manufacturing operations, QC test stations, and in logistics
areas. Hand-held imagers come in either tethered (with a cord), or cordless configurations. Tethered hand-
held imagers have the advantage of not being displaced from the application location. Cordless operation is
required in cases where part size or position is a practical limitation to cord length.
12 © ISO/IEC 2008 – All rights reserved

Figure 6 — Example of handheld imager
© ISO/IEC 2008 – All rights reserved 13

Annex A
(informative)
Intrusive marking methods
A.1 Intrusive marking
Intrusive Marking is designed to alter the surface of a material to form a human readable mark or a machine-
readable symbol. This marking category includes, but is not limited to, devices that abrade, burn, corrode, cut,
deform, dissolve, etch, melt, oxidize or vaporize the surface of a material.
Because intrusive markings alter the surface of a part (abrade, cut, burn, vaporize, etc.) they are considered
to be controlled defects. If not done properly, they can degrade material properties beyond a point of
acceptability. Consequently, some intrusive markings, especially direct laser, are generally not used in safety
critical applications without appropriate metallurgical testing. Typical intrusive marking methods include:
• Abrasive blast
• Dot peen
• Electro-chemical marking
• Engraving/milling
• Fabric embroidery/weaving
• Direct laser marking
Figure A.1 below provides cross section views of intrusive markings described in this section.

Discolored Markings –
Etched Markings – Electro-
Textured Marking – Micro-
Chemical Coloring, Electro-
Chemical Etch and Laser
Abrasive Blast and Laser Etch
Chemical Coloring (AC) and
Engraving
Laser Coloring
Recessed Markings – Deep Dot Peen Marking
Recessed Markings – Machine
Laser Engraving
Engraving and Milling
Recessed Marking Coated to
Recessed/Etched Marking
Prevent Accumulation of
Surface Coating Removed
Backfilled to Provide Contrast
Foreign material or Corrosion
to Form Symbol
Figure A.1 — Intrusive marking cross-sections
14 © ISO/IEC 2008 – All rights reserved

A.2 Re-marking requirements using intrusive marking methods
Because the application of a single mark using an intrusive marking method causes material degradation,
additional intrusive markings made to obliterate or change those original markings could reduce material
properties beyond a point of acceptability. Therefore, approval should be secured from the responsible quality
assurance or engineering organizations before additional markings are permitted.
A.3 Laser marking
A.3.1 General
Selecting a system for laser marking involves choosing the proper wavelength for the material to be marked.
Marking ap
...