Motion, welding, robotics, workstations -- each can play a key role in bringing efficiencies to assembly challenges.
Assembling Oversized Airplane Wings
Electroimpact is the prime contractor for supplying automation tools to the Airbus plant in Broughton, UK, which is assembling the wings of the Airbus A380. The company collaborated with Bosch Rexroth to provide hydraulic and linear-motion solutions. It needed to phase in delivery of machinery as the facility ramped up operations to position, drill, rivet, and bolt the approximately 180,000 holes needed to produce a single Airbus 380 wing box.
Traditionally, panel assemblies were built on manual jigs, requiring many skilled workers to locate and drill holes, pull components apart for deburring and cleaning, apply sealant, and insert two-piece lockbolt fasteners.
"We ended up expanding the system''s performance envelope and accuracy of earlier panel production machinery," says Electroimpact''s Ben Hempstead. "The result is a new generation of wing panel machines. Our design goal was to enable one operator to set up, load NC tapes, verify accuracy, and configure the fixtures."
After the wing panels -- up to 111 ft long -- are produced, they must be moved to wing-structure jigs. Electroimpact created an array of six coordinated servo hydraulic arms to engage the panel. The primary axis of movement is maintained in a closed-loop servo control by a Rexroth HNC 100 servo hydraulic controller integrating an SSI linear scale, load cell, and a Rexroth servo solenoid valve.
Handling a wing panel with multiple support points is very difficult, according to Electroimpact''s Theodore Karagias. "Basically you have a statically indeterminate system. The panels will twist, bend, and kick as they react to the forces introduced by lifting equipment."
Once the wing panels are loaded in the jig, they are fastened to the rib-and-spar structure with Electroimpact''s HAWDE machine and the undercarriage reinforcement is attached through the lower wing skin with Electroimpact''s GRAWDE system. To reach areas of the wing where flooring is normally located, the HAWDE machine''s Y-column extends above its normal position by about one meter, using a Rexroth size 45 roller rail system for guiding and a hydraulic cylinder for lifting the floor. Electroimpact''s GRAWDE mobile automated drilling system uses a Rexroth roller rail for the X, Y, and Z axes; the latter use Rexroth ball screws. (For more, click here.)
Keeping Welding Specs Tight
Storage rack manufacturer Frazier Industrial maintains tight quality control procedures because its products must be able to withstand a rigorous warehousing environment. This emphasis led the company to upgrade its welding wire feed systems with programmable features and controls.
Aaron Evans, quality assurance manager for Frazier, says Miller Electric Mfg Co''s 70 Series wire feeders play a key role in his company''s quality control program. "We run the same welding parameters in every single one of our plants to ensure uniform quality and consistency, no matter where the component is made," explains Evans. "Our procedures are such that we need to control both the width and the penetration of the bead so that we get good tie-in on both plates involved with the weld. The reason we use the Miller wire feeders is because they help us control part of that process."
The weld sequence controls permit setting gas pre-flow and post-flow time, wire feed run-in speed, weld time, crater time, and wire burnback. Adjusting parameters such as run-in speed can improve arc starts, while crater control helps the operator prevent crater cracking at the end of the weld. Four weld programs allow operators to store customized weld parameters, which reduces setup time when operators regularly switch between two different applications.
For Frazier''s purposes, the key wire feeder feature is its weld process control feature that sets and locks in welding parameters to ensure operators consistently weld within specifications, yet still offers them limited freedom to tailor wire feed speed and voltage values to suit their personal tastes. Digital LED displays also simplify setting parameters
"Our tolerances are tighter than American Welding Society standards. We need to ensure that operators stay within our established parameters, and programmable feeders help maintain weld quality from operator to operator and shift to shift," Evans notes. (For more, click here.)
Giving the Robot a Bigger Brain
A large automotive powertrain manufacturer had been producing automotive transmissions the same way for many years. In an effort to use the current robotic system to its full potential, the manufacturer sought help from FANUC Robotics. The robot was already being used to remove parts from the assembly line during backups. The goal was to robotically put the parts back on the line once it was back in motion. To make the new process a success, the robot would be required to accurately locate each part, pick it up, and put it back on the line.
FANUC Robotics reprogrammed its customer''s R-2000iA/125L robot, adding FANUC''s HandlingTool software and V-500iA/3DL three-dimensional vision system. The three-dimensional vision system was mounted on the robot''s end-of-arm-tooling (EOAT), and the HandlingTool software program was installed. Together, these tools enable the robot to determine part location and orientation in the bin so that the parts can be robotically picked up and properly placed back on the line. The software also prevents the robot''s EOAT from colliding with the bin wall. (For more, click here.)
Replacing Wood with Ergonomics
Tolerances have to be consistently tight when you''re assembling wire harnesses for a jet fighter --1/8 of an inch over 32 feet, to be exact. That''s one of the problems faced by a jet aircraft manufacturer when it decided to upgrade its wire harness assembly facility. Another problem was ergonomics -- the facility was using pieces of plywood on wooden A-frames as the takeoff point for the assembly of their 32-ft-long wire harnesses with 150 termination points. This not only affected tolerance levels but also led to potential technician stress, strain, and fatigue.
Pro-Line delivered 32 custom electric wire harness workstations, each retrofitted with a range of accessories. The workstations were each 4 ft deep by 8 ft wide, with a 16 in. range of height adjustability and an 80% tilt range. Pro-Line needed to produce eight stations comprised of four units, linked together end-to-end, in order to properly address the large job. The benches had to move in unison, up and down, so precise tolerances were even more essential.
Each Pro-Line workstation was retrofitted with accessories designed for the needs of assembly technicians. For example, a suspended tool trolley, which was attached to two uprights and strategically placed over the work surface, featured tool balancers for optimal operator comfort. These spring-loaded tool balancers take on most of the weight of the technicians'' hand tools -- the weight is on the balancer and not on the hand. Other retrofitted accessories include overhead lighting that eliminates eye strain while clarifying every task, and power supplies for electric tools designed to keep electrical cords from interfering with work. (For more, click here.)