Mar., 02 / Northrop Grumman's Marine Systems Division (NGMS) had a defense issue of its own to resolve against wear, tear, and time. Engineers had to make strategic and tactical decisions about the most efficient and cost-effective means to update the division's fleet of aging machine tools and controls used in manufacturing its Main Propulsion, Power Generation, and Launcher product lines. The final battle plan called for retrofitting machines whenever possible with CNCs and servo drives from GE Fanuc Automation.

The first retrofit attack was on a traveling-gantry, NC vertical- spindle machine for drilling and light milling of large components. "This machine had an X-axis mechanical anti-skewing, or X-axis yaw, compensation system that was temperamental and difficult to maintain," says Mark Stallings, principal manufacturing engineer at NGMS. The malfunctioning system led to rework, repair, and production delays, he adds.

GE Fanuc application engineers, Phoenix-based CNC Machinery Sales Inc., and NGMS in-house personnel installed a GE Fanuc Series 15 MB CNC and +/-Series servomotors and amplifiers on the machine's four control axes. They also replaced the original spindle with a GE Fanuc Model 22A, 29.5-hp spindle drive, motor, cables, and encoder.

A control and servo drive retrofit from GE Fanuc Automation brought new life to this traveling-- gantry machine at Northrop Grumman's Marine Systems Division.

After the retrofit and a realignment, machine volumetric accuracy improved about 50%. Error compensation techniques reduced errors in linear-displacement accuracy, repeatability, and reversal. "Compensation tables within the GE Fanuc control are easily accessed, changed, and tested quickly for positive results," says Stallings.