MANUFACTURING
Marking and Vision Technologies:
Forming a More Perfect Union
Regulators and end users alike demand product traceability. The right combination of marking techniques
and machine vision systems can help to achieve that.
L. Jordan, Cognex UK Ltd, Milton Keynes, UK
The rise of traceability
As consumer demands continue to spiral
upwards and stringent legislation and
regulations blanket all aspects of manufacturing, the importance of tracing products from “cradle to grave” is paramount.
Traceability not only appeases regulators,
but satisfies end users who receive products
to the agreed specifications and are able to
track any part’s history, should issues arise
in the future.
With this in mind, both marking and
vision technologies have continued to
evolve at a considerable pace and the use
of 1D and 2D codes is now commonplace. A substantial increase in 2D usage
has been seen within the medical device
sector, where the benefits of code marking, reading and traceability are being
realised.
It starts with the code
To ensure traceability, the first essential
ingredient is a code. Typically, 1D bar
codes encode only numerics, whereas 2D
can encrypt alpha-numerics (up to 150
alpha-numerics are standard in a 48 ×
48 cell, 10 × 10 mm) for a printed label.
Usually 1D bar codes operate against a
“look-up” table, or database: a unique
serial number is encrypted within the
code and referenced against a database.
By comparison, all 2D code data can
be encrypted within it, allowing for full
traceability with or without access to the
database.
Handheld code readers provide a high degree of
flexibility.
The Data Matrix star
The 2D Data Matrix code ECC200
emerged as the industry standard, as it
allowed essential information to be included
on a product, thus ensuring full traceability, whilst dealing successfully with space
issues. Significantly smaller than a standard
bar code, the versatile nature of the Data
Matrix code propelled it to the forefront of
product traceability.
This code uniquely identifies each
product or part manufactured. A digital
imprint marked directly on a part surface
ensures internal traceability on the production line and external traceability during the entire life cycle of the product.
Primary tasks of the Data Matrix code
are to ensure error-proofing, part trace-
ability, part authenticity, and supply-chain
management. The technology is used
across a range of medical devices includ-
ing surgical instruments, pacemakers
and medicine bottles.
Marking options
The primary methods used to produce Data
Matrix codes for direct part mark identification include dot peening, laser marking,
electrochemical etching, ink-jet printing and
key dot marking. Important factors influencing the marking process decision include
part life expectancy, material composition,
environmental wear and tear, and production volume. Other considerations include
surface texture, the amount of data to be
encoded on each part, as well as the available space and the location of the mark on
the part.
Dot peening is achieved by pneumatically or electromechanically striking a carbide or diamond tipped stylus against the
surface of the material being marked. The
technique is widely used in the automotive
and aerospace industries because of the
demanding life-cycle requirements.
Laser marking applies heat to the
surface of a part, causing the surface of
the part to melt, vaporise or change in
some way in order to produce a mark. The
resulting quality depends upon the interaction of the laser with the material it is
marking. A laser can produce both round
and square modules and offers high speed,
consistency and a high level of precision.
Laser marking is widely used in the semiconductor, electronics and medical device
industries.
