GS1 DataMatrix Printing with Videojet Technology

GS1 DataMatrix Printing with Videojet Technology
The information contained in this document is proprietary and confidential to Videojet Technologies, Inc. and should be used solely for its benefit, and
not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 1
Most people are familiar with traditional barcodes
such as the UPC (Universal Product Code) from the
supermarket checkout counter, or the Code 128 that
is commonly used on shipping labels.
These symbologies have generally been robust
enough for their applications, but they are not
without limitations.
UPC codes, for example, must contain only 12
numeric digits. Code 128, while supporting a large
number of alphanumeric characters, can only grow
in one direction, so it can very quickly become too
long for its intended print area.
What this means is that linear barcodes are
impractical for the item level unique barcoding now
required in many sectors of the pharmaceutical and
food industries.
The ability to embed a lot of data in a small code is
necessary, and DataMatrix is the symbology that
best meets that requirement.
A DataMatrix code is composed of a grid of light and
dark cells. The code size grows both horizontally
and vertically, depending on the amount of data
encoded. Each cell, or module, represents a bit with
a binary value of either 1 (dark cell) or 0 (white cell).
A single DataMatrix symbol can contain up to 3,116
numeric characters.
Error correction is built into DataMatrix, which
means that some portion of the printed code can be
rendered incorrectly without invalidating the data.
ECC-200 with Reed Solomon error correction is the
most forgiving version of DataMatrix, and is the
standard across most industries. GS1 (Global
Standards One), the worldwide governing body for
barcode applications, only supports ECC-200.
This error correction, which uses a complex
mathematical algorithm, allows for up to 60% of the
code to be damaged while the overall code can still
be read.
Under the GS1 implementation of DataMatrix,
multiple fields are concatenated to yield a single
string of characters that produce the final code.
Trading partners throughout the supply chain are
then able to use barcode readers to break apart the
code into component data such as part number,
expiration date, serial number, or any one of over a
hundred other available designated fields.
Videojet printers are designed to support the GS1
standards. Our laser coding, thermal transfer, CIJ
(Continuous Inkjet), DOD (Drop on Demand – such
as thermal inkjet), binary array printers and thermal
transfer overprinters all support GS1 DataMatrix
standards.
Lincoln’s Gettysburg Address as a DataMatrix
The information contained in this document is proprietary and confidential to Videojet Technologies, Inc. and should be used solely for its benefit, and
not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 2
Introduction
This document provides a technical overview of DataMatrix symbology, with a focus on the
GS1 implementation. Alternate variations of the word DataMatrix include “Data Matrix” (space
between Data and Matrix), “Datamatrix” (lower case m), but for this document DataMatrix has
been chosen in order to be consistent with the GS1 General Specifications documentation.
A DataMatrix code is a two-dimensional matrix barcode consisting of black and white modules
arranged in either a square or rectangular pattern. A single symbol can store up to 3,116
numeric or 2,335 alphanumeric characters. DataMatrix has been used in the public domain
since 1994.
GSI (Global Standards One) is the worldwide body responsible for creating standards for
barcode applications. Formerly known as the UCC (Uniform Code Council) in the United
States and EAN (European Article Numbering) International in other countries, GS1 was
established in 2005 as the single body responsible for issuing and maintaining company
prefixes and establishing rules for barcoding applications. When a company needs to
barcode its products, the first step is get a unique GS1 company prefix, which will then be
used as the starting data for all GTINs (Global Trade Item Number). The GS1 System has
adopted DataMatrix because it can encode GS1 System data structures (described in detail
later in this document) and because its compact design accommodates placing the symbology
onto a greater variety of substrates than other symbologies.
ISO (International Organization for Standardization) specifies the requirements for bar code
symbologies, including symbology characteristics, dimensions, tolerances, decoding
algorithms and parameters to be defined by applications
Data content and the rules governing the use of barcode symbologies are outside the scope
of ISO; they are defined in the GS1 General Specifications.
ISO’s membership includes technical experts from all over the world. The United States is
represented in ISO by ANSI (American National Standards Institute)
Production processes that are using GS1 DataMatrix Symbols include:
•
Direct part marking, such as pharmaceutical, automotive, aircraft metal parts, medical
instruments, and surgical implants
•
Laser or chemically etched parts with low contrast or light marked elements on a dark
background (e.g., circuit boards and electronic components, medical instruments,
surgical implants).
•
Very small items that require a compact code with a square aspect ratio and/or
cannot be marked using other symbologies within the allocated packaging space
•
GS1 DataMatrix Symbols are read by two-dimensional imaging scanners or vision
systems. Most other scanners that are not two-dimensional imagers cannot read GS1
DataMatrix. GS1 DataMatrix Symbols are typically restricted for use with applications
that will involve imaging scanners throughout the supply chain.
The information contained in this document is proprietary and confidential to Videojet Technologies, Inc. and should be used solely for its
benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 3
GS1 DataMatrix Basics
Figure 1
Figure1 represents a GS1 DataMatrix Symbol with 22 rows and 22 columns. Also displayed
is the same code with the Finder Pattern separated from the data region. Note that the top
right cell of a GS1 DataMatrix code is always white.
GS1 DataMatrix solid "L" shaped finder or alignment pattern is one module wide. (A module
is an individual cell within a code.) It is primarily used to determine the size, orientation and
distortion of the symbol. The other two sides of the finder pattern are alternating light and
dark elements, known as the “Clock Track”. This defines the basic structure of the symbol
and can also help determine its size and distortion.
GS1 DataMatrix Quiet Zone is one module wide on all four sides. As with other bar code
Quiet Zones, do not print in this area.
For square GS1 DataMatrix symbols, only an even number of rows and columns exist.
Depending on data requirements, symbols can range from 10 rows by 10 columns (10 x10)
to 144 x 144 (including finder pattern but not the Quiet Zone).
For normal printing, a module is one X by one X in dimension. A dark module is a binary (1)
and a light module is a binary zero (or a light module is a binary (1) and a dark module is a
binary zero for a symbol with reflectance reversal).
ECC 200 (ECC = Error Checking and Correction) includes Reed-Solomon error correction,
which uses a complicated algorithm to build redundancy into the code so that less-than
perfectly rendered codes can still be decoded. Table 1 shows the fixed amounts of error
correction associated for each allowable DataMatrix Symbol size.
FNC1 is encoded at the beginning of the data string and as a group separator. When a
FNC1 is used as a group separator, it should be represented in the transmitted message by
the ASCII character <GS> (ASCII value 29). FNC1 is not part of the data for the code being
printed, but is a codeword that is added by the software that is rendering the 2D symbol. The
resulting code will then be identified by the vision equipment as GS1 compatible.
Encodable character set
According to version 9.0 of the General Specifications, this includes:
•
Values 0 - 127 in accordance with ISO/IEC 646 International Reference Version (All
128 ASCII characters)
•
Values 128 - 255 in accordance with ISO/IEC 8859-1; Latin alphabet No. 1. (The
Extended ASCII character set)
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benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 4
While these are the characters that can be encoded by standard DataMatrix, GS1 has in a
separate document specified that the GS1 DataMatrix character set be limited to a specific
subset of ISO/IEC 646. These characters include:
abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789
!"%&'()*+,-./_:;<=>?
Furthermore, although these are the allowable characters, the current application identifiers
only support a-z, A-Z and 0-9.
Additional features inherent or optional in GS1 DataMatrix:
•
•
•
Reflectance reversal: (Inherent) Symbols can be read when marked so
that the image is on light or light on dark.
Rectangular symbols: Six symbol formats are specified in a rectangular form.
Extended Channel Interpretation (ECI) capability allows GS1 DataMatrix
to encode data from other alphabets.
Square and Rectangular Formats
GS1 DataMatrix may be printed in a square or rectangular format. The square format is
usually used as it has a larger range of sizes and is the only format available for symbols
encoding a large amount of data. The largest rectangular symbol can encode 98 digits, while
the largest square symbol can encode 3,116 digits. An enlarged rectangular symbol and an
equivalent square symbol are shown in Figure 2 below.
Figure 2
GS1 DataMatrix Symbol Sizes
GS1 DataMatrix Symbology has multiple sizes to match various data content (see Figure 3).
GS1 DataMatrix Symbols have 24 sizes of the square format ranging from 10 by 10 modules
up to 144 by 144 modules, not including the 1-X surrounding Quiet Zone. The rectangular
format has 6 sizes, ranging from 8 by 18 modules up to 16 by 48 modules, not including the
1-X surrounding Quiet Zone.
The information contained in this document is proprietary and confidential to Videojet Technologies, Inc. and should be used solely for its
benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 5
DataMatrix sizes of 52 x 52 or larger have 2 to 10 interleaved blocks of Reed-Solomon error
correction codewords. The term "codeword" is used often to describe attributes concerning
the encodation of data into GS1 DataMatrix Symbols. ISO 16022 defines codeword as "A
symbol character value. An intermediate level of coding between source data and the
graphical encodation in the symbol." Codewords are typically eight bits of data. FNC1, two
numerics, and one alpha all take up one codeword each. Note that symbol sizes of 32 and
larger are divided into multiple data regions. These regions are clearly delineated by their
accompanying solid alignment patterns.
The table below provides the capacity of each DataMatrix symbol along with the
corresponding percentage used for error correction. It provides the user with a guide for
selecting the most efficient symbol size for a specific application.
Table 1
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benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 6
With the above table, the proper matrix size can be matched with the amount of data needed
for a specific application. The actual physical measurement of the printed code will depend
on the capabilities of the print system. The width of an individual module in a DataMatrix
code, known as either the x-dimension or mil size, is commonly used to express the size of a
code. To arrive at the overall symbol size, simply multiply the x-dimension by the matrix size.
In the table below, approximate code sizes are illustrated.
Symbol Size
Data Capacity
Row x Column Numeric Alphanumeric
5 mil Examples
7.5 mil Examples
10 mil Examples
15 mil Examples
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benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 7
Data capacity information for additional DataMatrix symbol sizes
Square
Symbol Size
Row x Column
44 x 44
48 x 48
52 x 52
64 x 64
72 x 72
80 x 80
88 x 88
96 x 96
104 x 104
120 x 120
132 x 132
144 x 144
Rectangular
Data Capacity
Numeric Alphanumeric
288
214
348
259
408
304
560
418
736
550
912
682
1152
862
1392
1042
1632
1222
2100
1573
2608
1954
3116
2335
Symbol Size
Row x Column
8 x 18
8 x 32
12 x 26
12 x 36
16 x 36
16 x 48
Data Capacity
Numeric Alphanumeric
10
6
20
13
32
22
44
31
64
46
98
72
As seen above, a 10 x 10 DataMatrix code with a mil size of ten will produce a code of .1” or
2.54mm.
Application Identifiers
When using GS1 DataMatrix the data must be structured according to the rules of the GS1
System. Element strings begin with an Application Identifier which is then followed by the
data that the AI denotes. The system can be characterized by:
• A standard format for encoding data and bar coding specifications.
• A symbol architecture that allows multiple data elements (item identification,
expiration date, batch number, etc.) within a single barcode.
These features enable trading partner information systems to be developed in a way that
enables communication via encoding and decoding the information in the GS1 DataMatrix
symbol.
GS1 Application Identifiers (AIs) are 2, 3 or 4 digit numbers which define the meaning and the
format of the data that follows. Each AI and its associated data can be encoded into a GS1
DataMatrix symbol in the same way – and using the same logical rules - as encoding data in
the linear bar code symbol GS1-128. Application Identifiers should be clearly recognizable.
This is achieved by putting parentheses around Application Identifiers in the Human Readable
Interpretation under the symbol. The parentheses are not part of the data and must not be
encoded in the bar code.
The information contained in this document is proprietary and confidential to Videojet Technologies, Inc. and should be used solely for its
benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 8
Table 2 is a complete listing of the GS1 element strings along with their associated formatting
guidelines:
Abbreviations used:
n
= Numeric digit
an
= Alphanumeric characters
n2
= Fixed length of 2 numeric digits
an…20 = Variable length with a maximum of 20 alphanumeric characters
The information contained in this document is proprietary and confidential to Videojet Technologies, Inc. and should be used solely for its
benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 9
The information contained in this document is proprietary and confidential to Videojet Technologies, Inc. and should be used solely for its
benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 10
Table 2
Notes:
(1) The first position indicates the length (number of digits) of the GS1 Application Identifier. The
following value refers to the format of the data content.
(2) If only year and month are available, DD must be filled with two zeroes.
(3) The fourth digit of this GS1 Application Identifier indicates the implied decimal point position.
Example:
- 3100 Net weight in kg without a decimal point
- 3102 Net weight in kg with two decimal points
Using GS1 DataMatrix, it is possible to concatenate (chain together) discrete Application
Identifier (AIs) and their data into a single symbol. The FNC1 character acts as the field
separator. In general, when the AI data is of pre-defined length, no field separator is required
between that field and the one that follows.* Where the AI data is not of pre-defined length
(is variable), and is less than the maximum length for that AI, it must be followed by a field
separator when concatenating more AIs. The FNC1 character acts as field separator. In this
position, the value returned for FNC1 by vision systems should be the ASCII value 29 (or
group separator <GS>). A FNC1 separator is not required after the last AI and last data
encoded in the symbol independent of whether the field is of pre-defined length or not.
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benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 11
When several GS1 Application Identifiers have to be concatenated and only one of them is of
variable length, it is strongly recommended to position it at the end of the symbol. This
optimizes the size of the symbol by avoiding the use of a separator character.
*Remember that there are instances when FNC1 is required even after a fixed-length field.
Some fixed-length Application Identifiers, for example 426 (3 digit fixed country of origin),
require FNC1 when followed by addition Application Identifiers. It is best to confirm on a case
by case basis.
Human Readable Interpretation of GS1 DataMatrix
Symbols
The Human Readable Interpretation of the primary Application Identifier (AI) Element String
encoded in the GS1 DataMatrix Symbol should be shown with the symbol. How the human
readable data will be shown is determined by the specific application guidelines. Typical
conventions, as used for GS1 DataBar (formerly RSS) and Composite Component Symbols,
place the key information, such as the Global Trade Item Number (GTIN), in the human
readable data underneath the bar code symbol, while secondary information is placed above.
The characters should be clearly legible and must be obviously associated with the symbol.
Als should be clearly recognizable to facilitate key entry. This is achieved by putting the Al
between parentheses in the Human Readable Interpretation.
For GS1 DataMatrix Symbols encoding large amounts of data, it may not be practical to
display all the data in Human Readable Interpretation form. Even if there is space to show it in
this form, it may not be practical to enter that much data. In these instances, some of the data
may be omitted from the Human Readable Interpretation. However, primary identification data
(GS1 System keys), such as the GTIN, must always be shown. Application specifications may
provide additional guidance on Human Readable Interpretation.
Note: The parentheses are not part of the data and are not encoded in the symbol.
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benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 12
GS1 DataMatrix Marking Examples
Technology
Description
Laser
Marking and
Coding
Uses focused
energy light
beam to
inscribe or alter
target material
Thermal
Transfer
Overprinting
High resolution
contact printer
using ribbon
Binary Array
Printing
Continuous 2”
high stream of
drops that are
selectively
charged and
deflected
Thermal
Inkjet
Drop on
demand; tiny
heated drops
fired onto
substrate
Characteristics
Example
Close Up
Low maintenance
No consumables
Permanent
marking
Green technology
Highest print
quality
IP65 rating
Variety of colors
Bi-directional
motor drive
eliminates label
waste
Speeds up 2400
fpm
Fast Drying inks
Variety of colors
2 independent
printheads
Simple to
maintain
Variety of colors
Clean technology
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benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 13
GS1 DataMatrix Verification
GS1 DataMatrix symbols can be verified by use of a GS1-certified barcode verifier. When
selecting verification equipment, it is important to select a product that supports
ISO/IEC15426-2, ISO/IEC15415 and ISO/IEC 16022. In addition the system needs to be able
to verify that GS1 Application Identifiers have been appropriately placed in the barcode data,
and that the printer is encoding the leading control characters and group separator
characters where appropriate.
Below, an Integra 9505 Barcode Quality Station by Label Vision Systems has been used to
verify a DataMatrix code printed by a Videojet BX6500 Binary Array Printer.
The barcode received an overall grade of A.
The human readable data is
01303502421346832112345678901234. Including the non-human readable structure of the
symbol, the verifier extracted the following:
<FNC1> (indicates GS1)
01
30350242134683 21 12345678901234
(AI for GTIN)
(GTIN)
(AI for Serial #) (Serial #)
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benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
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ISO/IEC 15415 specifies the evaluation parameters for all 2D codes, including the GS1
DataMatrix code. Below the parameters are summarized.
ISO Symbol Grade: The overall ISO symbol grade is the most important parameter for
communicating the print quality of a symbol. The scan grade is the lowest grade achieved for
the seven key parameters which are Symbol Contrast, Modulation, Fixed Pattern Damage,
Decode, Axial Nonuniformity, Grid Nonuniformity, and Unused Error Correction. The overall
ISO symbol grade is the average of the individual scan grades for a number of tested images
of the symbol.
Decode: This is the first step in the verification and applies the reference decode algorithm the set of rules/steps for decoding the symbol defined in ISO/IEC 16022 - to the elements
seen by the verifier. If a valid decode results, the decode parameter passes and is given
grade 4, otherwise it fails (grade 0).
Symbol Contrast: The Symbol Contrast is the difference between the highest and the lowest
reflectance values in the profile – in other words the difference between the dark and light
areas (including the quiet zones) as seen by the scanner. Symbol contrast is graded on a
scale of 0 to 4.
Modulation: Modulation is related to Symbol Contrast in the sense that it measures the
consistency of the reflectance of dark to light areas throughout the symbol
Axial Nonuniformity: measures and grades (on the 0 to 4 scale) the spacing of the mapping
centers and tests for uneven scaling of the symbol along the X or Y axis.
Grid Nonuniformity: Measures and grades (on the 0 to 4 scale) the largest vector deviation
of the grid intersections, determined by the theoretical position prescribed by the reference
decode algorithm and the actual measured result.
Unused Error Correction: Measures and grades (on the 0 to 4 scale) the reading safety
margin that error correction provides. Unused error correction indicates the amount of
available Error Correction in a symbol. Error Correction is a method of reconstructing data
that is lost via damage or erasure of the symbol. Error correction may have to be used to
decode the symbol and may have been caused by damage to the symbol or poor printing.
100% unused Error Correction is the ideal case.
Fixed Pattern Damage: Measures and grades (on the 0 to 4 scale) any damage to the finder
pattern, quiet zone and clock track in the symbol.
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benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 15
Below, common verification failures are illustrated.
Problem
Symbol
Parameter
Possible Causes for bad grade
Symbol
Contrast
- Dark Substrate
- Poor Illumination
- Indirect access to code (reading code
through laminate)
Symbol
Contrast
- Improper ink choice
-Improper lighting angle
Modulation
- Dark cell spilling over into adjacent
light cell
- Ink missing from some areas
- Transparent substrate
Axial
Nonuniformity
- Product traveling at wrong speed
(encoder required)
- Product slipping on conveyor
Grid
Nonuniformity
Fixed Pattern
Damage
Fixed Pattern
Damage
- Product not square with printhead
- Code too large for curvature of
product
- Printer setup problems
- Irregular substrate consistency
- Product abraded prior to scanner
- Human readable text within quiet
zone of symbol
Reference List
GS1, 2009. GS1 General Specifications, Version 9.0, Issue 1, January 2009
GS1, 2009, Introduction to GS1 DataMatrix , Issue 1.16 (final), March 2009
The information contained in this document is proprietary and confidential to Videojet Technologies, Inc. and should be used solely for its
benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 16
How to produce the highest quality DataMatrix from the
1000 series of printers:
•
Set the pitch/cpi
Note: To set the pitch/cpi: print a 20 character, 5 x 7 message. Measure from the start of any
character to the start of the 11th character and determine if you have a 10 cpi or 60 ppi stroke rate
for an encoder. This is key for setting the width of the Data Matrix correctly.
•
Set the throw distance and character height to get an exact square Data Matrix code (height must
be equal to the width)
Note: This is applicable for a square Data Matrix only
•
Install the printer and the printhead as per the installation guidelines
•
Font height that you select must be equal to, or greater than the Data Matrix density. For example,
to print a Data Matrix with 12 x 26 density, the font height should be 12 or higher.
•
Use a shaft encoder if the line speed varies (not required if the speed is constant, equal to, or less
than the maximum speed for a certain font height)
How to produce the highest quality TIJ DataMatrix code:
•
Always use an encoder, as proper feedback on the speed of the target substrate is
essential to make sure the matrix is properly formed (i.e. not stretched or condensed) and
to increase the crispness of the image.
•
When securing an encoder wheel to a belt-driven conveyor, be sure to mount the encoder
on a flat section of belt as close as possible to the print location. Avoid mounting the wheel
on or near rollers as speed will not be accurately reported.
•
If ghost (shadow) printing occurs and cannot be permanently resolved, print in single
column mode (use only one of the two ink columns in the cartridge)
•
Make sure the cartridge is as close as possible to the substrate without touching.
•
Proper ink choice is critical. While in general TIJ technology requires a porous surface,
there are a growing number of choices, including UV curable inks, which can work for a
wider range of substrates. Utilizing the Videojet sample lab to help determine the optimal
ink choice is always recommended.
•
Do not exceed the specified maximum allowable speed for the specific print resolution.
Besides damaging the print cartridge, overspeeding can result in stretched and distorted
print.
The information contained in this document is proprietary and confidential to Videojet Technologies, Inc. and should be used solely for its
benefit, and not disclosed outside the Company in any form without the prior written consent of Videojet Technologies Inc.
Page 17