Epoxy Dispensing Machines are needed to apply the epoxy precisely and uniformly to fiber optic connectors prior to inserting the fiber. The Fiber Optic Center Technical Team provides consultation on the exact type of dispensing equipment best suited for specific applications and the viscosity of the epoxy being used.
In most single-fiber connector terminations, epoxy is injected into the rear of the connector to accomplish two main objectives:
- Optimum Bonding of the fiber to the ferrule: Epoxy is injected through the fiber hole, until a small bead exits the tip. This ensures that the fiber hole is completely filled before inserting the fiber, resulting in optimum bonding. The epoxy bead serves as a visual indicator to the operator that the hole has been filled, but also serves as some level of protection against fiber sub-surface cracking if the protruding fiber tip is inadvertently broken prior to cleaving. While the bead size may not be “critical”, it is helpful to have a repeatable bead size, as this helps the “epoxy removal” stage of polishing. Too small a bead increases the risk of sub-surface cracking, and too large a bead increases time needed during the “epoxy removal” stage of polishing.
- Protect the fiber from breakage within the connector. Deposit sufficient epoxy at the base of the ferrule (within the connector) to fully encapsulate the fiber strip point, which, if not protected, is very prone to breakage. It is important that neither too little nor too much epoxy is dispensed inside the connector. Too little epoxy increases the risk of fiber breakage after termination, and too much epoxy can overflow the ferrule holder and lock up the internal ferrule spring---both cases which render the connector useless.
Epoxy dispensing-equipment options range from fully manual, to semi-automated, to fully automated systems.
Manual Process
Epoxy is typically injected (dispensed) using a syringe. This can surely be done manually by filling a typical syringe barrel with epoxy, inserting the syringe needle into the rear of the connector and manually applying pressure to the plunger to dispense the desired quantity. Manual epoxy injection can be a great choice if you have occasional need to terminate small quantities of connectors, or for field-terminations or emergency repairs. However, automated dispensing equipment can help give more repeatable results, particularly in factory settings, reducing operator training and skill needs and reducing scrap and failure modes.
Pneumatic Dispensers
Pneumatic dispensers are widely used, simple, reliable, and can be an excellent semi-automated option. With pneumatic dispensers, the manual thumb-plunger is replaced by connecting the syringe barrel to a compressed-air source. The operator inserts the needle into the syringe as normal, but then presses a footswitch to apply a preset amount of air pressure for a preset amount of time to dispense a desired quantity epoxy. This allows for much simpler, more repeatable dispense quantity compared to manual dispensing. Because the epoxy viscosity will increase over its working life, the pressure and time setting needed to maintain consistent dispense quantity will also need to increase over the working life of the epoxy. Some pneumatic dispensers have a programming capability to automatically increase the time and pressure combination automatically over the working life of the epoxy, to ensure consistent dispense quantity. Most pneumatic dispensers have a “suck-back” feature to help prevent excess epoxy pushing out the syringe between dispense shots, which can be very helpful in reducing accidental epoxy dripping or cross-contamination areas of the connector which should not have epoxy.
Volumetric Dispensers
Another semi-automated dispensing system is the Volumetric dispenser. As the name suggests, these are designed to physically / mechanically push a specific volume of epoxy from the syringe. As with pneumatic systems, the syringe body is attached to the dispenser mechanism, which serves to replace the operator’s thumb with, commonly, an “auger” type of mechanism. While these types of systems are typically more expense and complicated, they are designed specifically to dispense the most repeatable and consistent quantity of epoxy over the working life of that epoxy. Most of these system also include a “draw-back” feature to help prevent epoxy from oozing out the syringe between dispense shots.
Robotic Systems
Robotic systems can fully automate the epoxy injection process, by attaching the syringe to a 3-axis setup similar to a home CNC-router: Connectors are arranged on the “bed”, and the syringe is programmed to move above, and then down into each connector. Most such robotic systems incorporate volumetric-style dispensers. While these systems can be very useful in high-volume applications, they do require precise fixturing to ensure connectors are held in precise position and are generally most suitable for high-volume connector production lines.
The Fiber Optic Center Technical Team provides consultation on the exact type of dispensing equipment best suited for specific applications and the viscosity of the epoxy being used. Epoxy Dispensing Machines are needed to apply the epoxy precisely and uniformly. Choosing the correct dispensing equipment will ensure the epoxy is applied accurately and consistently, and impact the quality and reliability of the finished fiber optic product.
