The goal at Amerex Corp. (Trussville, AL), a manufacturer of commercial and industrial fire extinguishers, was to automate the assembly of fire extinguisher valves.

"Amerex started several years ago to automate parts of our production line because of an increasingly tight labor market," says Jeff Layfield, production manager. An automated assembly system from Jewett Automation (Richmond, VA) produces one completed valve every 4 seconds using only two operators and one technician per shift. Previously, this assembly required approximately 13 people on each shift.

The major challenge was installing, orienting and inspecting the pressure gauge, which is located on the valve assembly and indicates whether the fire extinguisher is charged correctly. The gauge has a green, pie-shaped area to indicate acceptable pressure. This area must be correctly oriented at twelve o’clock. An automated approach that mimics the combination of vision, torque and intuitive feel applied by operators replaces the manual assembly for this part.

To create the control feedback loop, a vision camera inspects each incoming gauge to determine initial orientation of the pie indicator. The image is interpreted and fed to a custom gauge-insertion driver to define a target ending position. Continuous monitoring of the torque required to drive the gauge and an adaptive algorithm that interprets the specific driving characteristics for each gauge allow consistent installation within target orientation and torque parameters. A second vision system then confirms the gauge is oriented correctly.

Other key features of the automated assembly system include on-line functional leak testing, confirmation of thread sealant via an ultraviolet vision inspection and detailed part status tracing information during the manufacturing process.

Amerex’s manufacturing engineering department and Jewett Automation modified one of the parts to ease the assembly process. This resulted in a higher acceptance rate of final assemblies. The addition of a fluorescent tracer in the thread sealant also made inspection easier.

For more information on automated assembly, call 804-233-9861 or visit