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The paper describes the development and implementation of two control subsystems for aircraft panel riveters. They were installed on two production CNC riveters to provide improved edge tracing of longerons and drill/countersink control. The optical tracer uses video techniques to maintain a constant edge distance for fastener locations. The guidance system, which employs a standard TV camera, offers increased reliability, convenience, and versatility over mechanical type tracers. The programmable spindle/quill feed system is based on a commercially available microprocessor-controlled hydraulic servo control. Installation of the control, servo valve, and feedback transducer is described. Enhanced capabilities, such as multiple feed rates and remote control of drill/countersink depths have resulted.

Investigations were made of the effects of high-frequency, d-c, straight polarity current pulsations in the range of 2,000-25,000 pulses/s on the quality and mechanical properties of gas tungsten arc (GTA) welds in 2219 aluminum. Pulsed-current and conventional GTA welds were made on 0.125, 0.250, and 0.350 in 2219 aluminum, using free fall, single-pass butt welds. Results of this investigation show that pulsed-current welds are superior in x-ray integrity to conventional GTA welds made under similar conditions, with discontinuity levels 80% lower for relatively long weldments. High-frequency pulsation is also very effective in avoiding the typical cast structure of weld metal. Such welds exhibit fracture toughness values 10-15% higher than conventional GTA weldments. Potential manufacturing advantages include higher weld quality (fewer rejects and lower rework costs) and thinner weld lands, which result in lower structural weights.