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Patient safety through direct product identification
High quality standards always apply to the production and use of items in the medical sector for good reason. Unique identification for traceability is already widely implemented throughout production. Direct Part Marking (DPM) utilising the different technologies described below with optical inspection equipment is also used for this purpose.
To identify products without labels, Direct Part Marking (DPM) is commonly used. This means the data is permanently marked into the product itself. Depending on the material, surfaces and the items final usage, different marking methods are used.
Electrolytic marking is based on an electrochemical etching process. The exact copy of a template is applied to an electrically conductive product, in which current and electrolyte react with each other. Latest developments also allow 2D codes to be serialized. This method is commonly used in medical technology and perfect for stainless steel and surgical instruments. The products can be sterilized without any detrimental effects to the marking.
Dot Peen Marking
With Dot Pin marking (Needle embossing), materials are marked using a carbide tipped tool (needle) that oscillates by the application of compressed air moving in X and Y directions during its upward and downward movements. This results in a dense sequence of individual dots (writing) being punched into the material. Depending upon the needle frequency, a complete line can be achieved. Characters, digits, logos and 2D codes (DataMatrix) can be imprinted in the field as desired.
Dot Peen Marking is safe, resilient and flexible. Especially for direct marking of inventory in hospitals where it can replace expensive tags. Another advantage is the possiblity of painting after marking as the code can remain visible. Due to the physical properties and the mechanical load there are some limitation to the marking size, Datamatrix codes should not be less than 5 x 5 mm and the writing should be at least 2 mm in height. Many types of plastic and virtually all metals can be marked with this method. 1D barcodes cannot be marked.
Marking with a laser is the most flexible method for marking a very wide range of materials and is also non-contact, also, unlike Dot Peen and the electrolytic marking, mechanical fixtures are not usually required.
Laser systems are available with different wavelengths.
For marking metals and plastics lasers with 1064 nm are most commonly used. When using additives in the materials, nearly all type of plastics can be marked. As an alternative, lasers with 532 nm are available, which can mark a wider range of plastics without requiring additives.
Depending upon the optics, modern laser marking systems have a beam diameter of between 40 and 80 μm. This allows very small encoding with high data content. Using Ostling vanadate laser system combined with the XS Designer software the marking process can be very finely tuned. Users can easily switch between a wide range of marking methods:
- Engraving: A groove is etched in the component with a laser beam. The material vaporizes or melts in this process. The marking depth can be up to 50 µm.
- Material abrasion: This is a special form of engraving. In the case of anodised aluminium, for example, the surface can be removed in order to reveal a different coloured layer beneath it.
- Annealing colours: Here the heat of the laser beam and the atmospheric oxygen change the colour of the metal. There is no significant material abrasion. The laser beam penetrates max. 5 µm into the metal.
- Colour changes: Changing of material colour can be performed with most plastics and some lacquers. Special additives ensure a high contrast colour change at the place where the laser beam makes contact.
- Foaming: Due to the heat of the laser beam, the plastic is thermally disintegrated at the laser beam’s point of impact. This results in gaseous decomposition products, causing the plastic to foam.
Standardisation of codes According to UDI
To ensure World-wide unique identifications organisations and association have standardised the code content. AIM as the head organisation, GS1 covers many different market sectors and HIBC within medical technology.
Most commonly used 2d code is the Datamatrix Code. It allows small markings with simultaneous data redundancy. This is controlled by an error correction (ECC200)
UDI allows the use of Barcodes as well as Datamatrix codes. The data content is dependent on the Standard (GS1 or HIBC) ISO 15459-2 and ISO / IEC 15418. ISO 28219 describes the hierarchies of the content. Packaging is typically marked according to ISO 22742. A possible data structure according to HIBC is shown in figure 1.
Worldwide unique content data structures allow 100% product traceability and counterfeit protection at the same time. For this reason is It is imperative in manufacturing, to verify Codes immediately after marking using a Camera system, Modern camera systems check the physical properties of the codes and write content to a database in order To avoid duplication.
To check the quality of the codes, Standards have been established (ISO, 15415, ISO 15416, AIM DPM). Physical cell size, contrast, error correction, axial distortion and other parameters are monitored. When using DPM marking procedures, errors can be caused in the code.
For example, in the case of the electrolytic marking, codes can be over- marked due to the current flow and the duration of marking. Distortion is not expected, since the stencils are of very high Quality.
Good contrast codes are generally produced with laser marking on most surfaces. Using foaming on plastics can however cause the black cells to be too large due to expansion.
Dot Peen is a special case for DPM. The marking process does not produce direct contrast. The needle will generate a round dot by displacing material which will cause some distortion. To read codes created with Dot Peen equipment requires oblique illumination.
This Procedure is precisely defined in the above-mentioned standards. In the manufacture of surgical instruments stationary scanners are mostly used. Surgical instruments are usually directly marked by the manufacturer with at least their logo and a part number. This is essential for possible re-orders, repairs and inventories. For the daily use in hospitals this is not sufficient however as there is not an unique assignment to the individual instruments being used. To ensure this, instruments are uniquely marked by service providers.
Depending on the countries of use HIBC or GS1 standards are used. Most of the marking is done with Laser Marking but can also be done using electrolytic etching. The assignment to the individual operating rooms for the patient can then be established with the use the existing Clinic software.
Ostling works closely with well-known manufacturers of hand scanners. These can be used to decode the smallest of data matrix codes. Modern algorithms and optimised illumination guarantee a fast and safe read. The integration into existing database systems is relatively easy, as the scanner itself connects itself via a USB interface as an additional "keyboard" and will connect to almost all operating systems automatically.
Please visit us at Med-Tech, Coventry, UK from 26 to 27 April 2017, stand 27a.