Vision cameras

When vision cameras started out on production lines, they were often used in isolation simply to inspect the final product at the end of the line. Whilst this would ensure that only compliant items were delivered to the customer, it allowed a significant amount of resource to be spent on a product through its different stages that effectively could end up as waste.

With ever increasing quality demands and industry legislation requiring product lifecycle accountability, it has been vital for manufacturers to adapt their production processes to comply with these changes. However, it has been a worthwhile transformation due to the distinct advantages offered by industrial ID to manufacturers, including:

•    Regulatory compliance – Many industry bodies recognise 2D coding on products as standard, e.g. FDA regulations such as 21CFR Part 11.
•    Product history - Permanently marking products with 2D codes containing critical information ensures ‘cradle-to-grave’ traceability throughout the entire life of the product.  This is critical both for internal identification during production, but also for identification during maintenance or replacement tasks.
•    Avoiding the use of counterfeit parts - Direct part marking of products at the moment of manufacture eliminates the danger of using counterfeit & non-compliant parts.

In addition, huge cost savings can be obtained through fully automated traceability within the production process, not just in man-hours but also by reducing the amount of errors, by eliminating re-working or even recalling of products. The result is an increase in production efficiency, removal of possible errors and an overall improvement in automation.

To achieve full product traceability, manufacturers have upgraded from 1D to 2D codes. Typically, 1D barcodes, which were commonplace in all industry sectors, encode only numerics, whereas 2D can encrypt alpha-numerics for a printed label. Usually 1D barcodes operate against a ‘look-up’ table or database where a unique serial number is encrypted within the code and referenced against a database. In comparison, all 2D code data can be encrypted within it, allowing for full traceability with or without access to the database.

With essential information required on a product to ensure full traceability is achieved and with space on a product often a key factor, the 2D Data Matrix™ code ECC200 emerged as the industry standard. Significantly smaller than a standard barcode, the versatile nature of the Data Matrix code propelled it to the forefront of product traceability. The codes are used for error-proofing, part traceability, part authenticity, and supply chain management and ensure both internal traceability (on the production line) and external traceability for the entire life cycle of the product (once dispatched to the customer).

Marking Options
The primary methods used to produce Data Matrix codes for direct part mark identification include dot peening, laser marking, electro-chemical 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 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 and is widely used in the automotive and aerospace industries due to the demanding life cycle requirements.

Laser marking applies heat to the surface of a part that causes 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.

Electro-chemical etching (ECE) is a process whereby the mark is produced as a result of the oxidation of metal from the surface being marked through a stencil impression. ECE is recommended for round surfaces and for stress sensitive parts, and is often used to mark medical devices.
Ink-jet printers precisely propel ink drops to the part surface, after which the fluid that makes up the ink dot evaporates, leaving a coloured dye on the surface of the part creating the pattern of modules that make up the mark. Ink-jet marking provides fast marking of moving parts and offers very good contrast.

Key Dots are small sticky labels, in a variety of sizes and materials with a Data Matrix code printed on the surface, which is then affixed to the product.

Code reading
Once the code is marked on the particular part or product, it is of little use unless it can be accurately read. This is where machine vision takes up the reins to ensure that full product traceability is achieved.
For a typical manufacturing application, as the marked part passes in front of a vision sensor, an image of the Data Matrix code is captured and then processed using specialised image pre-processing and identification algorithms. Using this technology, the code reading performance is unaffected by low contrast or poorly formed codes which can result from marking issues or general wear and tear of the product.

In addition to reading the data stored on the code, the sensors can also provide production process feedback on the quality of the specific marking to ensure products are marked with the highest quality of 2D codes. Perfecting the quality of the codes to eliminate any waste will lead to improved overall production efficiency and reduced operating costs.

Code reader options
Most machine vision systems are integrated into the production line in the form of fixed-mount sensors which are used in identifying parts that are handled and moved automatically by conveyor, indexer or robot. In operation, this type of reader is mounted in a fixed position where the mark can repeatedly be placed in front of the reader in either continuous or indexed motion. They can often be configured with either an integrated light source or with an external light source as required by the application.
However, to allow maximum flexibility, advanced ID code readers are also available as hand-held devices, particularly useful for non-production line and large marked products. These also are used for parts in multiple locations, for example, within hospital departments when surgical instruments are required to be scanned pre- and post surgery.

Traceability in Medical Practice
Traceability and transparency for instrument management are critical factors in hospitals and clinics.  A European based company has developed a system using an advanced vision system which has already proven effective in many clinical practices, ensuring traceability of sterile surgical instruments.  Such applications are setting new standards in operating theatre safety, central sterilisation units as well as administrative efficiency for hospital cost centres.

Traceability of each instrument on a piece by piece basis is crucial. Instruments are stored in filters, similar to small sieves, holding around 50 to 100 instruments. Each filter is marked with a barcode and read using the hand-held reader which allows clinic personnel to know that a filter has been correctly packed with the specific instruments for a particular department.
The clinic staff see a picture of the filter on their workstation monitor, showing which registered instruments can be included. This eliminates the possibility of human error as only instruments that are intended for this specific filter can be read. Each correct reading is displayed immediately on the monitor and unintentional duplicate assignment of instruments is ruled out, because the code reader will not register the second identical read operation.

Each surgical instrument is permanently marked with 2D Data Matrix code which is 100% reliable against counterfeit identification codes and ensures full traceability for the lifecycle of each part marked. Implementing such a traceability programme within instrument management has meant that central sterilisation can be sure that their filters contain the correct instruments. These applications are crucial for safety and legal evidence in case of potential claims for damages within the medical industry.

Vision-proof future
As the everyday production challenges facing manufacturers increase, many are looking to utilise technological advances to improve production efficiency and reduce costs. These objectives can be achieved by investing in accurate code marking and reading, resulting in full product traceability.
Cognex UK Ltd
Milton Keynes
Bucks.

Can be contacted on

Tel: 01908 206000
Fax: 01908 392463