New Adhesive Dispensing Method Simplifies Fiber Optic Assembly Processes Growing demand and increasing competition have fiber optic component manufacturers looking for new ways to increase productivity and control costs. Wherever possible, existing procedures are being re-evaluated and replaced with more efficient processes and equipment designed to boost yields and improve component reliability. Many companies that use epoxies and other adhesives during their assembly processes are discovering that changing the way these materials are applied can be an extremely effective way to help them increase their output and profitability. Fiber-to-Ferrule Bonding One of the most common applications for adhesives in fiber optic assembly is the use of epoxy to bond fibers inside connector ferrules. Typically, the epoxy is applied to the tiny opening at the back end of the ferrule until it begins to ooze out the other end. The fiber is then pushed through the back of the ferrule until it emerges at the ferrule face. Another method is to place a small amount of epoxy at the back of the ferrule and use the sliding action as the fiber is inserted to spread it through the ferrule. Some manufacturers insert the fiber first and then apply epoxy. Regardless of the method used, several problems can result if epoxy application is not consistent. For example, if too much epoxy is applied, extra time will be needed to clean off the excess and polishing time may be extended. If too little is applied and the fiber is not properly coated, the fiber-to-ferrule bond may be weakened. Underapplication can also weaken the pull strength of the connector so that the fiber breaks or fractures during routine handling and installation. A Productive Alternative to Hand Syringes Regardless of the method used, several problems can result if epoxy application is not consistent. The medical-type hand syringes that are often used for this application have several drawbacks. Because the amount of epoxy applied depends upon how hard the syringe's plunger is pressed, the size of the deposit will vary from part to part, regardless of an operator's experience. Hand fatigue is common, and productivity suffers because extra time must be spent on cleaning and rework. Parts might also be rejected for poor cosmetic appearance or failing the pull test. These problems can be eliminated with microprocessor-controlled dispensers that apply an identical amount of epoxy to every ferrule, every time. "Timed-pulse dispensers," as they are often called, simplify epoxy application by taking the guesswork and hand fatigue out of the dispensing process. They do this by using controlled air pressure and a programmable timer to regulate the amount of epoxy applied. Setup and operation of these devices is straightforward. The compact dispenser console is placed on the benchtop and plugged into a power outlet and connected to a source of compressed air. The epoxy or other adhesive is loaded into a disposable barrel reservoir, which is then connected to the dispenser by a lightweight, flexible air line. A precision dispense tip attached to the other end of the barrel completes the assembly. (Tips are available in a variety of gauges, lengths and styles to meet specific application needs.) To the operator, the overall effect is similar to the familiar hand syringe, but with an air line instead of a plunger at the back end. With the barrel loaded with epoxy and linked to the dispenser console, the air pressure regulator and digital timer are used to set the amount of the deposit. The microprocessor-based 1500XL dispenser from EFD (East Providence, RI) simplifies this process by incorporating a convenient "teach" function that makes it easy to quickly determine the optimal amount of adhesive. In teach mode, the dispenser's electric foot pedal is pressed to allow air pressure to move the epoxy through the barrel and out the tip. As soon as adhesive emerges from the face of the ferrule or the desired amount is reached, the pedal is released and the time that pressure was applied is automatically stored in memory. (Dispense time can also be set manually or fine-tuned in .1, .01, or .001 second increments.) To begin production the operator simply holds the barrel like a pen, places the tip in position on the ferrule, and taps the foot pedal to actuate the timer and dispense the adhesive. Tapping the pedal again will place an identical amount of epoxy on the next part. Higher Yields Without Hand Fatigue Benefits of timed-pulse dispensing over manual application with hand syringes include higher yields with less rework and hand fatigue, fewer rejects, and more consistent component reliability and appearance. Another advantage is that very little time is required to train an operator to apply the correct amount of epoxy -- a feature that is particularly useful for contract shops and other facilities where multiple workers must be quickly trained to meet periods of peak demand. Conclusion Companies willing to take a second look at their adhesive bonding processes will often realize significant benefits. In the words of one connector manufacturer, "Switching from hand syringes to timed-pulse dispensers has helped us reduce our assembly time by almost 40%. We're also seeing improved connector performance, particularly in severe environments, because we're able to put a better coating of epoxy on every fiber." -------------------------------------------------------------------------------- To learn how EFD equipment can help you improve your dispensing processes, please e-mail info@efd-inc.com, or in the USA call our Fluid Application Specialists at 800-556-3484.