Automatic dispensers are at work on thousands of assembly lines placing lubricants and adhesives. Some units are run by robots and some by line workers. Robots only do what they are told, but people have variability to their performance. To minimize the variation in their work, Dan Andrei, vice president and application engineer at I&J Fisnar Inc., Fair Lawn, N.J. (ijfisnar.com) suggests a few guidelines to ensure the right amount of material gets to the right place.

“For instance, before applying a material, experiment with dot size by applying different air pressure, time settings, and tip sizes,” he says. “You'll see that increasing either the air pressure, time duration, or tip size increases the dot size. Conversely, decreasing any of the three characteristics produces smaller dots.”

Thicker, more viscous liquids, such as pastes or greases, require either more pressure, longer time, or a larger size tip. “For thinner, less viscous liquids, such as cyanoacrylates or thinners, lower the pressure, shorten the time, or try a smaller tip,” he says.

To increase the dispensing speed, as would be needed for higher throughput, try adjusting the pressure higher, or shortening the time cycle, or both. To improve accuracy in deposit size, lower the pressure, or lengthen the cycle time, or both.

For consistent deposits, hold the barrel between 45 and 80°. Then touch the tip to the work surface. “Press the foot pedal to start the shot and keep the barrel in position until the cycle completes. Remove the tip from the deposit by lifting the barrel straight up. With the air pressure and time set, each successive deposit will be identical,” he says.

How you refill the barrel, of course, depends on the material. “For low-viscosity fluids, simply pour them in, but leave an air space at the top. A best practice here is to fill the barrel to 2/3rd full and refill at 1/3rd full,” says Andrei.

Filling high-viscosity materials is easier with a barrel loader. “Using a prefilled 12-oz cartridge, insert it in a metal container, and connect the air hose to a dispenser,” says Andrei. “Luer-lock barrels are loaded by operating the dispenser, either for a timed period or manually, until the barrel fills. Here too leave space at the top for air compression when fitting the adapter assembly, and use a barrel piston when filling barrels,” he says.