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Laser Marking And Machine Vision Codes for Product Security Traceability - UID


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Direct part marking of UID machine vision codes (barcode/data matrix) adds value for both manufacturers and end-users. Track-and-trace strategies are used throughout manufacturing to and thwart product tampering and counterfeiting. MIL-STD-130M is the standard practice on military prop-erty. For 3-D plastic products, lasers are preferred because the process yields indelible high resolution data cells, small imprint size and does not require expensive consumables.

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Laser Marking And Machine Vision Codes for Product Security Traceability - UID

  1. 1. TECHNOLOGY FEATURE by Scott R. Sabreen, The Sabreen Group, Inc.Industrial manufacturing requirements for indelible direct electronic, aerospace, automotive, pharmaceutical, etc., inpart marking containing machine vision codes are growing which significantly more advanced machine vision codesexponentially. Direct part marking enables tracking a product are required. The continuing drive to encode more informa-from the time of manufacturing until the end of its useful tion in combination with smaller space requirements haslife. This demand is driven by the increasing requirements led to the development of two-dimensional “Data Matrix”for component traceability and product unique identification codes. Data Matrix codes cannot be read by a laser (used(UID). Post 9/11, manufacturers are implementing strategies in Barcodes) as typically, there is no sweep pattern that canto establish traceability and thwart product tampering and encompass the entire symbol. They must be scanned by acounterfeiting. The U.S. Department of Defense (DoD) has camera capture device. 2D Data Matrix is the revolutionaryMIL-STD-130M as the standard practice on military prop- machine-readable code specifically designed to address theerty. Beyond DoD military requirements, manufacturers of limitations of barcodes. Figure 1 demonstrates the differ-commercial industrial products ranging from automotive, ences between 2D Data Matrix v. Barcode.packaging, pharmaceutical, electronic, and consumer goodsare aggressively adopting similar standards. 2D Code Bar CodeDirect part marking containing unique identification informa-tion necessitates digital process technology such as inkjet, dot Contains datapeen, and laser marking. For many three-dimensional plasticproducts, lasers are the preferred method because the processyields high-contrast indelible markings and does not require Contains dataexpensive consumable ink costs/solvents or post-curing.Further, lasers can mark the smallest-size machine vision AND /ORcodes. This is important for micro-marking, or when thereis limited surface area on a part or component to be markedwith alphanumerics, logos, or schematic diagrams. Robustsix-sigma manufacturing operations require all products tobe 100 percent human or machine vision readable regardlessof the size and detail complexity of the actual marking.What are Machine Vision Codes?Machine-readable (vision) codes are coded information Figure 1that can be interpreted through the use of optical scannersor cameras. A familiar example is one-dimensional “Bar- Comparison between 2D Code and Barcodecode” which is a representation of information, typically 2D Data Matrix codes are ideal for small parts marking anddark contrast on a light background, to create high and are designed to survive harsh industrial environments. Thelow reflectance that is converted to 1s and 0s. The most size of Data Matrix codes is only 1/10 to 1/100 of Barcodecommon formats of barcodes store data in the widths and given equal encoded data. Thus, very little space on a part isspacings of printed parallel lines (black and white stripes). needed which can contain significant manufacturing data forHowever, newer patterns of dots, concentric circles, and product traceability. Every code is about half black and halftext codes hidden within images also are used. Within the white, resulting in a 50/50 chance that cell damage will notUnited States, the UPC (Universal Product Code) is the harm readability. Data Matrix’s high degree of redundancybest-known and most widespread use of barcodes in retail (data is scattered throughout the symbol) and resistance toand consumer products. printing defects makes it highly reliable. Error correction schemes built into the algorithm optimize the ability to re-Although modern barcode schemes can contain the ASCII cover from symbol damage. Figure 2 compares Data Matrixcharacter set, there are needs in the manufacturing sectors, Code v. Barcode.28
  2. 2. 2D Data Matrix Code Barcode Information capacity About 4,000 characters About 20 characters Kind of information Alphanumeric figure, Kanji Alphanumeric figure Information density 160 1 The hardware and software com- Error correction function Contained Uncontained ponents that a laser manufacturer incorporates into its systems makes Contrast As low as 20 percent Usually 80 percent a significant difference in marking (relative to substrate) and up quality and speed. A primary at- Readability 360 degrees (any angle) Fixed position tribute is the power density (watts/ Cycle time to apply code Milliseconds Seconds cm2) at the mark surface (which is (by laser) different than the raw output power Figure 2 of the laser). Beam-steered Nd:YAG laser markers (arc lamp and diodeLaser Marking light sources) utilize mirrors that are mounted on high-speedThis segment focuses on using 2D Data Matrix codes on computer-controlled galvanometers to direct the laser beamthree-dimensional plastic-manufactured component parts and across the surface to be marked, much like writing withassemblies (including Acetals, Nylons, Polyolefins, Polycar- pencil and paper. Each galvanometer, one on the Y-axisbonates, Polyesters, Styrenics, etc.). These types of plastics and one on the X-axis, provides the beam motion withinare chemically inert, non-polar with low surface energies. the marking field. A flat-field lens assembly focuses theFor direct part marking, Nd:YAG lasers offer advantages over laser light to achieve high power density on the substrateink-based processes such as inkjet, which require surface pre- surface. Figure 3 shows optical beam delivery system usingtreatment and curing. Beam-steered Nd:YAG lasers (“YAG”) computer-controlled 1064nm wavelength (near infrared spectrum) are popular inthe laser marking industry due to their emission wavelength, continued on next pagepower performance, and versatility. This results in fastermarking speeds, higher quality, and greater production. beauty is in the eye of the beholderAs reference, the continuous wave (CW) CO2 lasers operate ata wavelength of 10.6 µm (far infrared spectrum). CO2 lasersgenerate comparatively much lower peak power than YAGlasers and thus, they cannot produce high contrast markingson most plastics. Note, CO2 lasers are commonly used formarking barcodes and matrix codes on labels, paper-stock, There’s more to decorating than aesthetics.and ink ablation. Barcodes, instructions, and warnings are functional graphics thatThe mechanism of laser marking is to irradiate the poly- can be in molded andmer with a localized high-energy radiation source (laser). protected for years.The radiant energy is then absorbed by the material andconverted to thermal energy. The thermal energy induces Decals that are pretty useful.reactions to occur in the material. All beam-steered YAG Enhance your product perform-lasers are not created equal. ance, manufacturing process, YAG Laser Source and product appearance with Romo Durable Graphics. X-Galvanometer Y-Galvanometer Computer-controlled mirrors Flat field lens DURABLE•GRAPHICS Workpiece (920) 712 -4090 Y X Figure 3 In-mold Graphic Solutions is a division of Romo Durable Graphics. 29
  3. 3. TECHNOLOGY FEATURE continued from page 29The output mode of the laser beam is critical to the marking power produces minimal vaporization but conducts moreperformance. Lasers can be supplied by manufacturers as heat. Beam velocity (speed) also is a critical factor.multi-mode, TEM00 (transverse electromagnetic mode) oranything in between, including low-order mode. These output The use of laser additives will enhance and optimize themodes relate to factors including the beam divergence and machine vision code contrast and decrease marking cyclepower distribution across the diameter of the laser beam. Low- times. These factors ultimately save money and increaseorder and TEM00-mode lasers are particularly well-suited manufacturing production. Material science solutions arefor high-speed vector marking of Data Matrix and Barcodes, cost effective, easy-to-use, and possess no deleterious effectssingle-stroke alphanumerics, filled true-type fonts, and com- on the polymer products’ physical and chemical propertiesplex graphics because of their ability to achieve a small focused given the proper resulting in a very narrow line with well-defined edges. ApplicationsPower density is a function of focused laser spot size. Fo- An excellent application example is 2D Data Matrix codescused laser spot size for any given focal length lens and laser applied via laser to harsh environment underhood automotivewavelength is a function of laser beam divergence, which is fuel components and assemblies (typically Acetals, Nylons,controlled by laser configuration, mode selecting aperture and Polyesters). As shown in Example A, page 32, the ⅛" sizesize, and upcollimator (beam expander) magnification. Pulse code is marked in about 200 milliseconds. Data contained inrepetition rate (via acousto-optic Q-switch) and peak power the code includes full traceability of the component part (fromdensity are critical parameters in forming the mark and resin batch, mold-machine, date-shift-time, and assemblyachieving the optimal contrast and speed. High peak power leak test). New technology advancements for laser markingat low frequency increases the surface temperature rapidly, of Acetals further expands the realms of product serializationvaporizing the material while conducting minimal heat into and traceability. Example B: As explained by one automotivethe substrate. As the pulse repetition increases, a lower peak executive, “Many of the underhood Acetal fuel components we continued on page 32 Your Source for Decorating and Automation Solutions As your one-stop for state-of-the-art decorating machinery and automation systems, Versadec Corporation com- bines close to 100 years of manufacturing expertise from its companies - Screen Tech and Acromark. Specializing in building machines for screenprinting and hot stamping, we offer comprehensive, in-house capabilities to fulfill your most challenging decorating and assembly projects. To ensure the highest quality products, we maintain close relationships with suppliers of inks, foils, transfers, dies, and tooling used in our decorating equipment. Founded on an industry guarantee of total satisfaction, allow us to be your true turnkey solution for decoration and automation machinery. 1 ton, 2 1/2 ton hot stampers, and semi automatic silk screeners IN STOCK NOW. For details on our equipment visit our new website www.versadec.com30
  4. 4. TECHNOLOGY FEATURE continued from page 30design are compact. Indelible micro-markingof critical information and Data Matrixcodes near the end of automated assemblyoperations, subsequent to in-line leak testing,has great value in the industry. Unique part ⅛" 1/8”identification also benefits in-house inventorymanagement for work in-process (W.I.P.).”Modern machine-vision systems are not juststand-alone inspection devices. Rather, theyare integrated into six sigma total manufac- Example Data Matrix Matrix for Example A. 2D A: 2D Data for productturing operations including statistical quality product traceability and security traceability and securitycontrol metrics programs. Advanced systemscontain artificial intelligence which furtherexpands the realm of lasers and machine- Example B. Black Laser Marking on White POM codes. The powerful combination of Patent Pending VectorJet™ Laser Marking Technology enables indelible robustlaser marking is seen as critical to success by machine vision codes; alphanumeric text; micro-marking 0.020” (0.5mm) andproviding process feedback and error preven- smaller; graphics; logos; and schematic diagrams.tion for products with nearly zero defects. nScott R. Sabreen is founder and president ofThe Sabreen Group, Inc. (TSG). TSG is a global engineering finishing, laser marking, and product security. For morecompany specializing in secondary plastics manufacturing information, call toll-free (888) SABREEN or visit www.processes – surface pretreatments, bonding, decorating and and Webtech, Inc. www.webtech- hts.com32