Robot streamlines finishing of composite antenna covers

Sparks Fiberglass' (Rock Island, Ill.) first order for 50 8-ft/15.2m long fiberglass antenna covers for cellular telephone towers in 1998 kicked off a growth period for the company, in which manufacturing space quickly became scarce. When the company moved to a larger facility, it began looking for alternatives to the dusty and labor-intensive hand-finishing processes required for the covers. Sparks found a solution at systems automation company Genesis Systems Group LLC (Davenport, Iowa).

Genesis worked closely with Sparks to develop a robotic workcell, which could incorporate trimming, drilling and routing functions for the antenna covers and Sparks' other fiberglass parts, as well. The workcell features a Fanuc R2000 six-axis robot arm from Fanuc Robotics (Rochester Hills, Mich.) equipped with a 10-hp spindle motor, an automatic tool changer and six tool holders to accommodate diamond saw blades and carbide router and drill bits — essentially the same tools used in previous for hand-finishing operations. (An automated wear sensor was not necessary, because tool wear is minimal and the company replaces the tools on a regular schedule.) The robot is positioned between two 120-inch/305-cm-long tables, which form separate workstations. This permits a technician to unload and load parts at one station while the robot operates at the other, maximizing cutting time and increasing efficiency. Each table features a series of drilled holes, positioned at 6-inch/152-mm intervals to accommodate a wide variety of different holding fixtures. Fixtures, consisting of metal frames with fiberglass part-contacting details that match the part contours, were designed and manufactured in-house by Sparks. Genesis engineers developed the system control software and user interface, says Whitney Moon, Genesis' market segment manager for automation systems. Part program is selected with the robot's "teach pendent" feature, a remote handheld device linked to the robot.

Installed in January 2002, the workcell first drills required mounting holes and router cutouts with a custom carbide tool, then trims part edges with a diamond-coated saw blade, which takes one to three minutes, enabling production in one day of what used to take three days by hand — a 10 to 1 gain. Moreover, the system improves part surface finish consistency and overall productivity while reducing rework. In 2006, Sparks predicts it will produce about 36,000 antenna covers, a twelve-fold increase from the 3,000 produced annually prior to workcell installation, with the same number of employees.