Reliability, safety, and traceability are winning characteristics of laser marking
Editor’s Note: Laser marking/engraving is the largest industrial laser application in terms of units sold. Globally, laser marking has experienced a 20 percent per year growth rate as security, traceability, and warranty regulations are causing product suppliers to turn to this versatile marking process. At Laser 2007, World of Photonics in Munich in June ILS met with more than 40 companies that exhibited industrial laser marking technology/equipment. Here we offer a sampling of applications from our discussions with one manufacturer. -LJB
F1 teams typically strip down and rebuild three cars (two racecars and one spare) after every race/test event. Each car is assembled from some 3500 components-all of which are subject to continuous improvement, resulting in perhaps 10,000 components being associated with each car at any one time.
As part of an ongoing effort to continuously improve reliability and safety, F1 (and other motor sport) teams take component identification seriously. Although historically many of the larger assemblies have been marked with human readable information, it is the ability to effectively track not only the large components but virtually every component on the car that is interesting. An appropriate Enterprise Resource Planning (ERP) system is required, allowing production and revision control along with stock, financial, and part life control.
Direct Part Marking (DPM) makes it possible to track a product from time of production to when it is scrapped. To achieve this, a high-quality permanent mark able to withstand extreme conditions (heat, abrasion, caustic fluids, etc.) is required. It is possible for the ERP system, via a relational database, to maintain an accurate history of individual components, when and how it was made, where it has been, how it has been used, and for how long.
Developed in the late 1980s in the U.S., the data matrix code is now globally accepted within the automotive, aerospace, and electronics industries. As the code is in the public domain, its use is free from any licensing or royalties.
Due to their small size and large data capacity, the data matrix codes make it possible to identify nearly every component on the car from wishbones and steering racks, to pistons and fuel injectors, to nuts and bolts. The data matrix has a high degree of redundancy and is resistant to marking defects, providing high reliability. It has built-in error correction and a minimum print contrast requirement of 20 percent when reading with an industrial-quality camera.
Data matrix codes can be made by methods other than laser marking, including ink jet, electro-chemical etch, and dot peen. For the F1 application, the variety of materials and surface finishes is wide. Exotic materials/alloys, including titanium and magnesium, are employed. The laser is preferred as it is able to produce good permanent ‘readable’ codes on virtually all materials without compromising the structural integrity of the component. The laser is flexible and able to produce either round or square matrix elements although for dense information, squares are often preferred. In addition, laser is able to mark small codes (down to 1mm x 1mm), which is not possible using other techniques.
F1 teams have used lasers for many years for part marking. Recently the trend has been to not only diminish the marking area requirement but also automate the reading process allowing faster and more reliable identification. The existing lasers have been unable to meet the challenge of marking small IDM codes (due to the relatively large focused spot-like painting with a broad brush). As a result, Rofin has installed several of its PowerLine E - 10 (end-pumped Vanadate) laser sources at a number of F1 facilities; its high beam quality (small focused spot) and short pulse lengths allow high quality IDM codes to be produced on almost all materials, including steel, titanium, aluminum, and more, with overall mark dimensions approaching just 1mm2. These lasers could actually produce much smaller codes but both the mechanic and the code reader would struggle to actually find and read the code. Such a small code means that nearly all components used in car build can now be permanently marked and subsequently identified.
The motor sport industry is constantly developing new components, products, and services for worldwide applications, with spin-offs into the wider automotive and aerospace industries. Quality control and traceability are essential requirements for many businesses today. Mistakes cost time and money, and for motor sport companies, may well cost lives.
In addition to the protection of lives, a laser mark can also protect livelihood. Product innovations, in the motor sport industry and elsewhere, are considered to be strategically important as a relevant competitive differentiator in saturated markets. The competitive edge from innovations is often jeopardized when, despite trademark rights, plagiarism encroaches on a company’s sales. Using a laser, information carriers can be visibly or invisibly transferred directly onto the component or onto another carrier material (direct or indirect marking).
Serial numbers can be applied to the component, foil, or sign. In deep marking, the material is ablated without contact through melt displacement or vaporization. However, standard serial numbers have the disadvantage that they offer only limited copy protection. In contrast, barcodes are based on serial numbers with definable algorithms, a property that heightens copy protection. This technology is used by manufacturers of high-quality writing instruments, for example. Barcodes require readers and cannot be used for identification purposes without additional accessories.
In the case of indirect marking, the information carrier is not the product itself but, for example, a foil with special properties. The foil is marked using a laser and attached to the component in such a way that is cannot be removed without destroying it. The form and content of the foil (which can be cut out with the laser after marking) can be programmed as needed. This type of product protection is frequently used in the automotive industry and enables just-in-time production with great flexibility.
Direct or indirect, visible and invisible marking with a laser can also be accomplished using 2D coding technology from MicroGlyph Systems (www.microglyph.com). With this procedure, user data are coded using a specially developed software and can be transferred to the workpiece using a laser. Data can be decoded with standard decoders. This procedure features high information density (up to 400 bytes in approximately 1 cm2) and excellent readability even if codes are damaged.
FIGURE 2. Changeable Laser Image and Multiple Laser Image marking procedures are used for multilayer security cards such as passports.
In the case of invisible laser marking, the external appearance of the product does not change even though it carries important product information (see Figure 1).
Examples of patented procedures for visible laser marking for protection purposes are Changeable Laser Image (CLI) and Multiple Laser Image (MLI). These procedures are used with multilayer security cards (see Figure 2). First, the top (transparent) card layer is structured. Then a laser is used to burn in as many as three partial images at varying angles of incidence of the laser beam. The resulting image has an optical tilt effect. The disadvantage of this technology lies in the relatively expensive process.
This article was contributed by Rofin-Sinar Laser GmbH, Bergkirchen, Germany, and Rofin-Baasel, Daventry, UK, (www.rofin.com).