Direct part marking of UID machine vision codes (barcode/data matrix) adds value for both manufacturers and end-users. Track-and-trace strategies are used throughout manufacturing to and thwart product tampering and counterfeiting. MIL-STD-130M is the standard practice on military prop-erty. For 3-D plastic products, lasers are preferred because the process yields indelible high resolution data cells, small imprint size and does not require expensive consumables.

1. TECHNOLOGY FEATURE
by Scott R. Sabreen, The Sabreen Group, Inc.
Industrial manufacturing requirements for indelible direct electronic, aerospace, automotive, pharmaceutical, etc., in
part marking containing machine vision codes are growing which significantly more advanced machine vision codes
exponentially. Direct part marking enables tracking a product are required. The continuing drive to encode more informa-
from the time of manufacturing until the end of its useful tion in combination with smaller space requirements has
life. This demand is driven by the increasing requirements led to the development of two-dimensional “Data Matrix”
for component traceability and product unique identification codes. Data Matrix codes cannot be read by a laser (used
(UID). Post 9/11, manufacturers are implementing strategies in Barcodes) as typically, there is no sweep pattern that can
to establish traceability and thwart product tampering and encompass the entire symbol. They must be scanned by a
counterfeiting. The U.S. Department of Defense (DoD) has camera capture device. 2D Data Matrix is the revolutionary
MIL-STD-130M as the standard practice on military prop- machine-readable code specifically designed to address the
erty. Beyond DoD military requirements, manufacturers of limitations of barcodes. Figure 1 demonstrates the differ-
commercial industrial products ranging from automotive, ences between 2D Data Matrix v. Barcode.
packaging, pharmaceutical, electronic, and consumer goods
are aggressively adopting similar standards.
2D Code Bar Code
Direct part marking containing unique identification informa-
tion necessitates digital process technology such as inkjet, dot Contains data
peen, and laser marking. For many three-dimensional plastic
products, lasers are the preferred method because the process
yields high-contrast indelible markings and does not require Contains data
expensive consumable ink costs/solvents or post-curing.
Further, lasers can mark the smallest-size machine vision AND /OR
codes. This is important for micro-marking, or when there
is limited surface area on a part or component to be marked
with alphanumerics, logos, or schematic diagrams. Robust
six-sigma manufacturing operations require all products to
be 100 percent human or machine vision readable regardless
of the size and detail complexity of the actual marking.
What are Machine Vision Codes?
Machine-readable (vision) codes are coded information Figure 1
that can be interpreted through the use of optical scanners
or cameras. A familiar example is one-dimensional “Bar- Comparison between 2D Code and Barcode
code” which is a representation of information, typically 2D Data Matrix codes are ideal for small parts marking and
dark contrast on a light background, to create high and are designed to survive harsh industrial environments. The
low reflectance that is converted to 1s and 0s. The most size of Data Matrix codes is only 1/10 to 1/100 of Barcode
common formats of barcodes store data in the widths and given equal encoded data. Thus, very little space on a part is
spacings of printed parallel lines (black and white stripes). needed which can contain significant manufacturing data for
However, newer patterns of dots, concentric circles, and product traceability. Every code is about half black and half
text codes hidden within images also are used. Within the white, resulting in a 50/50 chance that cell damage will not
United States, the UPC (Universal Product Code) is the harm readability. Data Matrix’s high degree of redundancy
best-known and most widespread use of barcodes in retail (data is scattered throughout the symbol) and resistance to
and consumer products. printing defects makes it highly reliable. Error correction
schemes built into the algorithm optimize the ability to re-
Although modern barcode schemes can contain the ASCII cover from symbol damage. Figure 2 compares Data Matrix
character set, there are needs in the manufacturing sectors, Code v. Barcode.
28

2. 2D Data Matrix Code Barcode
Information capacity About 4,000 characters About 20 characters
Kind of information Alphanumeric figure, Kanji Alphanumeric figure
Information density 160 1 The hardware and software com-
Error correction function Contained Uncontained ponents that a laser manufacturer
incorporates into its systems makes
Contrast As low as 20 percent Usually 80 percent a significant difference in marking
(relative to substrate) and up
quality and speed. A primary at-
Readability 360 degrees (any angle) Fixed position tribute is the power density (watts/
Cycle time to apply code Milliseconds Seconds cm2) at the mark surface (which is
(by laser) different than the raw output power
Figure 2 of the laser). Beam-steered Nd:YAG
laser markers (arc lamp and diode
Laser Marking light sources) utilize mirrors that are mounted on high-speed
This segment focuses on using 2D Data Matrix codes on computer-controlled galvanometers to direct the laser beam
three-dimensional plastic-manufactured component parts and across the surface to be marked, much like writing with
assemblies (including Acetals, Nylons, Polyolefins, Polycar- pencil and paper. Each galvanometer, one on the Y-axis
bonates, Polyesters, Styrenics, etc.). These types of plastics and one on the X-axis, provides the beam motion within
are chemically inert, non-polar with low surface energies. the marking field. A flat-field lens assembly focuses the
For direct part marking, Nd:YAG lasers offer advantages over laser light to achieve high power density on the substrate
ink-based processes such as inkjet, which require surface pre- surface. Figure 3 shows optical beam delivery system using
treatment and curing. Beam-steered Nd:YAG lasers (“YAG”) computer-controlled galvanometers.
at 1064nm wavelength (near infrared spectrum) are popular in
the laser marking industry due to their emission wavelength, continued on next page
power performance, and versatility. This results in faster
marking speeds, higher quality, and greater production.
beauty is in the eye
of the beholder
As reference, the continuous wave (CW) CO2 lasers operate at
a wavelength of 10.6 µm (far infrared spectrum). CO2 lasers
generate comparatively much lower peak power than YAG
lasers and thus, they cannot produce high contrast markings
on most plastics. Note, CO2 lasers are commonly used for
marking barcodes and matrix codes on labels, paper-stock, There’s more to decorating than aesthetics.
and ink ablation. Barcodes, instructions, and warnings
are functional graphics that
The mechanism of laser marking is to irradiate the poly-
can be in molded and
mer with a localized high-energy radiation source (laser).
protected for years.
The radiant energy is then absorbed by the material and
converted to thermal energy. The thermal energy induces Decals that are pretty useful.
reactions to occur in the material. All beam-steered YAG
Enhance your product perform-
lasers are not created equal.
ance, manufacturing process,
YAG Laser Source and product appearance with
Romo Durable Graphics.
X-Galvanometer
Y-Galvanometer
Computer-controlled
mirrors
Flat field lens
DURABLE•GRAPHICS
Workpiece (920) 712 -4090 www.romoinc.com
Y
X
Figure 3 In-mold Graphic Solutions is a division of Romo Durable Graphics.
29

3. TECHNOLOGY FEATURE continued from page 29
The output mode of the laser beam is critical to the marking power produces minimal vaporization but conducts more
performance. Lasers can be supplied by manufacturers as heat. Beam velocity (speed) also is a critical factor.
multi-mode, TEM00 (transverse electromagnetic mode) or
anything in between, including low-order mode. These output The use of laser additives will enhance and optimize the
modes relate to factors including the beam divergence and machine vision code contrast and decrease marking cycle
power distribution across the diameter of the laser beam. Low- times. These factors ultimately save money and increase
order and TEM00-mode lasers are particularly well-suited manufacturing production. Material science solutions are
for high-speed vector marking of Data Matrix and Barcodes, cost effective, easy-to-use, and possess no deleterious effects
single-stroke alphanumerics, filled true-type fonts, and com- on the polymer products’ physical and chemical properties
plex graphics because of their ability to achieve a small focused given the proper formulation.
spot resulting in a very narrow line with well-defined edges.
Applications
Power density is a function of focused laser spot size. Fo- An excellent application example is 2D Data Matrix codes
cused laser spot size for any given focal length lens and laser applied via laser to harsh environment underhood automotive
wavelength is a function of laser beam divergence, which is fuel components and assemblies (typically Acetals, Nylons,
controlled by laser configuration, mode selecting aperture and Polyesters). As shown in Example A, page 32, the ⅛" size
size, and upcollimator (beam expander) magnification. Pulse code is marked in about 200 milliseconds. Data contained in
repetition rate (via acousto-optic Q-switch) and peak power the code includes full traceability of the component part (from
density are critical parameters in forming the mark and resin batch, mold-machine, date-shift-time, and assembly
achieving the optimal contrast and speed. High peak power leak test). New technology advancements for laser marking
at low frequency increases the surface temperature rapidly, of Acetals further expands the realms of product serialization
vaporizing the material while conducting minimal heat into and traceability. Example B: As explained by one automotive
the substrate. As the pulse repetition increases, a lower peak executive, “Many of the underhood Acetal fuel components we
continued on page 32
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4. TECHNOLOGY FEATURE continued from page 30
design are compact. Indelible micro-marking
of critical information and Data Matrix
codes near the end of automated assembly
operations, subsequent to in-line leak testing,
has great value in the industry. Unique part
⅛"
1/8”
identification also benefits in-house inventory
management for work in-process (W.I.P.).”
Modern machine-vision systems are not just
stand-alone inspection devices. Rather, they
are integrated into six sigma total manufac- Example Data Matrix Matrix for
Example A. 2D A: 2D Data for product
turing operations including statistical quality product traceability and security
traceability and security
control metrics programs. Advanced systems
contain artificial intelligence which further
expands the realm of lasers and machine- Example B. Black Laser Marking on White POM Acetal.
vision codes. The powerful combination of Patent Pending VectorJet™ Laser Marking Technology enables indelible robust
laser marking is seen as critical to success by machine vision codes; alphanumeric text; micro-marking 0.020” (0.5mm) and
providing process feedback and error preven- smaller; graphics; logos; and schematic diagrams.
tion for products with nearly zero defects. n
Scott R. Sabreen is founder and president of
The Sabreen Group, Inc. (TSG). TSG is a global engineering finishing, laser marking, and product security. For more
company specializing in secondary plastics manufacturing information, call toll-free (888) SABREEN or visit www.
processes – surface pretreatments, bonding, decorating and sabreen.com and www.plasticslasermarking.com.
Webtech, Inc. www.webtech-
hts.com
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