Traceability & Marking - Component Marking trends for Medical device manufacturers

Component identification and traceability is becoming increasingly important in the medical device manufacturing sector. The following provides a guide to component marking trends and the various technologies employed.

Make a Mark
For many OEMs and their first tier suppliers, product and component identification throughout a manufacturing process has become an indispensable part of quality control. To meet customer demands, suppliers are introducing part-marking systems to document component history throughout the manufacturing process. En-route, information is recorded on the part in the form of a discreet mark, which can be scanned manually or read by automated vision systems.

What's in a mark?
Thanks to the development of coding techniques, the amount of information that can be stored in a mark has, in recent years, increased dramatically. Today, technology exists to record information about machine type, operator, shift, date, time, supplier, measurement and test results, plus serial and batch numbers, all helping to guarantee the reliability and quality of parts. Nowhere is this more critical than in the medical device sector.

Most of the recent advances in marking technology are owed to the advent of Data Matrix, a two-dimensional matrix code containing 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 two-dimensional imaging device such as a CCD camera is necessary to scan the code. The more elements in the array, the more information the code can store. It is fast becoming the mark of choice for many in the medical sector.

Applying a mark
A major advantage of Data Matrix codes is that they can be applied directly to the surface of a component. In comparison with printing and applying labels they are far more secure, cost effective and easier to automate, as well as being extremely resistant to harsh operating conditions like instrument sterilization.

The method of applying a Data Matrix code depends on the parts to be marked, the material and the manufacturing environment. Inkjet, presses and electrochemical processes all have their particular attributes and ideal applications, but for applying Data Matrix marks to metal components, pneumatic (micro percussion) and laser marking are the most suitable methods.

Micro percussion marking deploys an oscillating hardened carbide stylus to indent component surfaces at a rate of up to 7 characters per second. As a process it 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 8 mm without adjustment.

Thin or fragile components can easily be marked using this technique. In the medical industry, typical applications for this marking technology include artificial knee and hip (acetabular cup) joints made from high density ultra high molecular weight polyethylene.

The laser age
Laser marking is rapidly becoming the process of choice for many wishing to apply Data Matrix codes to their components. The advantage of laser systems is the small beam width, allowing manufacturers to mark particularly small parts, an issue of increasing concern as the quest for increased 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, producing a high quality mark in a quiet manner. 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-micron resolution, a two-dimensional code can be produced measuring just 0.5 mm in width, making it particularly suited to medical or pharmaceutical industry components such as implants, prostheses, surgical tools and bio-fluid 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 bio-fluid storage containers, despite the fact that space was very limited.

After manual loading and precise indexing of the container, the laser provided marks in just one second, including: 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 mm square 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 provide a long system life expectancy.

Many users can anticipate greater than 10,000 hours use, representing 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 that can lead to restricted performance. Beam shape with 3-micron resolution and 50-micron spot size can be achieved.

A typical 10-character, 12 by 12 Data Matrix code on metal can be produced in less than one second. The small footprint of these units makes for easy integration into a production line or use as a simple dedicated permanent marking system in low or high volume applications, such as medical and surgical instrument manufacture. Take-up of these systems is accelerating for titanium implants/artificial joints, or wherever indents left by micro-percussion techniques are not desirable.

Vision to succeed
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 non-conforming 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.

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