revolutionary flexibility

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2 revolutionary flexibility

3 colorless The use of lasers in materials processing is growing rapidly. Speed, accuracy and flexibility are just a few of the benefits of this advanced manufacturing technique. Certain types of materials, particularly plastics, possess inherent properties that have limited the use of lasers in joining applications. However advances in material science are overcoming many of these limitations. There are many established methods for joining thermoplastics, each with its own advantages and disadvantages. Although laser welding is a viable alternative to most of these, its use in manufacturing has been impeded by an important factor color. In laser welding electromagnetic energy is absorbed and converted into thermal energy. Plastics, in their natural state, do not absorb near-infrared (NIR) light. Therefore the high energy of NIR lasers transmits directly through them. To successfully use lasers for joining polymers, their energy must be harnessed and converted into heat. Laser light must be absorbed at the joint interface to generate enough heat to produce a weld. Until now, the most common means of accomplishing this has been to disperse carbon black throughout the bottom substrate. Unfortunately this approach also places limitations on color. How it Works Through years of research Gentex, a privately owned technology company with extensive experience in both commercial and military markets, has developed a series of materials capable of powerful absorption in the NIR spectrum, while remaining virtually colorless. Clearweld incorporates these absorbers in unique material systems, including coatings and polymer resin compounds, designed for use in a variety of production processes. Simply applying a thin layer of the coating at the interface of two pieces of plastic concentrates laser energy. A localized melt of the substrates results in an instant weld, requiring no cure time and with no particulates or visible color. Welding of resin compounds works in much the same way while eliminating the coating application step. However, certain color and cost restrictions may apply. 0 C Substrate 1 Substrate 2 Localized Melt Source: TWI Ltd. The thermal model above shows localized heating of the substrates only at the joint interface. The effect of this precise heating generated from optimized parameters is important because it produces a very small weld line and heat affected zone. This results in superior weld strength. Clearweld is a revolutionary process for laser welding plastics without the use of carbon or the addition of unwanted color. Invented by TWI, a U.K.-based industrial research and development organization that specializes in materials joining, the Clearweld concept has been developed and is made available for real-world applications exclusively by Gentex Corporation. It is now offered as a single, flexible solution for joining transparent or opaque thermoplastics. The effectiveness of the material system depends upon its compatibility with specific process parameters. Coatings are formulated to take into account substrate materials, part design and process requirements. Critical to the success of the Clearweld process is the accurate delivery of the coating to the joint interface. Clearweld coatings are tested and certified for use with specific delivery methods, such as liquid dispensing. Resins are custom-compounded, taking into account substrate materials, color and process requirements.

4 Technical factors The Clearweld process simply requires a laser that will produce sufficient energy and an adequate level of NIR absorption at the interface to allow the flow of material to occur. Understanding the following technical factors is vital to successfully implementing Clearweld in a particular application. Material Application The Clearweld process depends upon accurate and repeatable application of the NIR absorbing layer to the joint interface. Gentex coatings are designed for use with approved delivery methods to assure the success of this process. Similarly, resin compounds are formulated to take into account process and design goals. A certified material supplier must be used in order to ensure process success. Intimate Contact To obtain intimate contact of the substrates at the weld interface, a certain amount of clamping pressure is required. The amount of pressure depends upon the materials being joined and their surface conditions at the weld interface. This allows sufficient melt flow to weld compatible substrates. Heat generation High-power diode lasers provide the electromagnetic energy necessary for generating heat. The typical wavelengths employed range from 940nm to 1064nm. Depending upon specific application requirements, a variety of power levels and configurations may be considered. It is critical, however, that the laser wavelength match the wavelength at which the material system is designed to absorb. Key to ensuring a successful Clearweld implementation are optimization of laser power, weld speed and absorption level of the material system. Fine-tuning these parameters can help produce weld strengths equal to the parent material at processing speeds equal to or greater than alternative joining techniques. advantages CLEARWELD Advantages High weld speeds Clean, optically clear, low-visibility joints 3D joint lines capability Accurate control of weld dimensions and position Rapid changeover to different products Precise control of process parameters Elimination of visible markings and weld flash Controlled localized heating for reduced risk of thermal damage or distortion Ability to weld clear or colored materials, as long as one or both transmit the IR wavelength of the laser No vibration or particulates Ability to apply material systems off-line and weld parts on demand Pre-assembly capability Bond strengths comparable or superior to other joining techniques Applications Medical products Packaging Automotive components Consumer products Electronics Textiles

5 GENTEX Corporation is a materials technology company serving commercial and military markets worldwide. USA P.O. Box 315 Carbondale, Pa P F clearweld@gentexcorp.com EUROPE GARETH McGRATH, EUROPEAN BUSINESS DEVELOPMENT MANAGER COMPASS HOUSE, VISION PARK, CHIVERS WAY, HISTON, CAMBRIDGE CB4 9AD United kingdom P F clearweldeu@gentexcorp.com Clearweld is a registered trademark of TWI Ltd. The (oval) logo is a registered trademark of GENTEX Corporation. Patented.