MARKET PLACE
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For many companies, product and component identification throughout the manufacturing process have become an indispensable part of quality control. Component history is recorded on the part in the form of a discreet mark that stores a large amount of information. It records information about machine type, operator, shift, date, time, supplier, measurement and test results, as well as serial and batch numbers, data that all help to guarantee the reliability and quality of parts.
The advent of data matrix code led to the recent advances in marking technology. This is a two-dimensional (2D) matrix code that contains dark and light square data modules. It has a finder pattern of two solid lines and two alternating dark and light lines on the perimeter of the symbol. A 2D imaging device such as a charge-coupled device camera is required to scan the code. The more elements in the array, the more information the code can store.
Applying a mark
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A major advantage of data matrix codes is that they can be applied directly to the surface of a component. Compared with printing and applying labels, they are more secure, cost-effective and easier to automate, as well as being resistant to harsh operating conditions.
The method of applying a data matrix code depends on the parts to be marked, the material and the manufacturing environment. Inkjet, and electrochemical processes all have their particular attributes and ideal applications, but for applying data matrix marks to metal components, rapid-indent (micropercussion) and laser marking are the most suitable methods.
Micropercussion marking
This method deploys an oscillating hardened carbide stylus to indent component surfaces at a rate of up to 7 characters/s. This process is well suited to plastics and most metals (with the exception of hardened steel greater than 62 HRc) and can mark curved surfaces up to distances of 6 mm without adjustment. Typical applications for this marking technology include artificial knee and hip (acetabular cup) joints made from high-density ultra high molecular weight polyethylene.
Laser marking
This is rapidly becoming the preferred process. Laser systems offer the advantage of a small beam width, which allows manufacturers to mark particularly small parts; this is an issue of increasing concern as miniaturisation continues in keyhole-surgery applications. Laser marking is clean, reliable, simple to maintain and has greater durability than many other systems.
Nd:YAG laser marking systems are suitable for use on metals, including hardened steel, as well as plastics. The relative robustness and compactness of the laser and the possibility for the light it produces to be transmitted to the workpiece via silica optical fibres are two features that contribute to its success. With 5-µm resolution, a two-dimensional code can be produced that measures 0.5 mm in width, which makes it particularly suitable for components such as implants, prostheses, surgical tools and biofluid storage containers.
For example, to facilitate automated data handling, a European medical laboratory recently decided to laser mark machine-readable codes alongside the human-readable codes on 48 wells of plastic biofluid storage containers, despite the fact that space was limited. After manual loading and precise indexing of the container, the laser provided marks in 1s; these included the eight-digit container code and a two-digit well identification code (all in 0.8-mm high human-readable text), and a 2.7-mm2 machine-readable 2D data matrix code containing the same information as the human-readable text.
One of the latest developments in laser marking technology is the diode-pumped laser system. Using short pulse, high peak power units, these systems are air-cooled and employ low-maintenance fibre-coupled diodes that have a long life expectancy. Many users can anticipate more than 10000 hours of use, which represents a 10-fold increase over lamps used in conventional laser-marking units. The benefit of reduced maintenance also lowers the risk of contaminants gaining access to the optics, which can lead to restricted performance. Beam shape with 3-µm resolution and 50-µm spot size can be achieved. A typical 10-character, 12 3 12 data matrix code on metal can be produced in less than one second. The small footprint of these units (770 mm 3 142 mm 3 237 mm) makes for easy integration into a production line or use as a dedicated permanent marking system in low- or high-volume applications such as medical and surgical instrument manufacture. These systems are increasingly being used for titanium implant/artificial joints or wherever indents left by micropercussion techniques are not desirable.
Improved production
In modern manufacturing facilities, improved productivity is related directly to the quantity and quality of the data collected and to the way data is applied. Production and quality engineers can use the data to monitor the production process. By combining an alarm or emergency stop to automatic parts identification at each stage of manufacture, a nonconforming part can instantly be prevented from moving to the next operation. The database can be sorted and programmed to provide useful indicators for tool test planning and maintenance programmes. Other data may be used for stock management or for production speed analysis. Medical device manufacturers are beginning to see traceability as a means of achieving sustainable competitive advantage.
For more information, contact Peter McCullough, Country Manager, Technifor UK Ltd, tel. +44 1926 884 422, e-mail: sales@ltd.technifor.com, www.technifor.com/uk.
