Whenever people think of aircraft assembly, they usually imagine lots of rivets. But, electrical wiring also plays a crucial role in aerospace manufacturing.
When Boeing was founded 100 years ago, engineers were concerned about how to use wiring to brace wings. Steel wire-braced structures were essential to biplane designs. They allowed wood- and fabric-covered wings to easily bend and twist.
As aircraft became more complex, engineers turned their attention to solving numerous wire harness assembly challenges. Many of their innovative solutions have been chronicled in the pages of ASSEMBLY.
The January 1960 issue of the magazine explained how Boeing engineers in Wichita, KS, could approach a mass of complex wiring in the B-52G bomber and identify individual wires in a matter of seconds. They used a portable current-path verifier that was developed in-house. The device fit in an aluminum case smaller than a shoe box.
“The five-pound sensing device has a hinged iron element that opens and closes like a pair of pliers,” said ASSEMBLY. “This is wound with a multi-turn coil. When the iron is closed around a ‘hot’ wire, a voltage is induced into the coil.
“Through the use of a miniature thyatron tube, a small neon lamp is made to glow,” added the article. “The low-powered tube allows the device to operate on two small batteries.”
Boeing engineers used the device to check 651 wire bundles in the bomber. “In many cases, multiple-strand cables of wires have pinned connectors at each end,” ASSEMBLY pointed out. “Each connector may have as many as 51 terminal pins, and after these are soldered to the cable wire, the bases are embedded in potting compound.”
The February 1960 issue of ASSEMBLY described how Boeing engineers developed a cable-winding machine that was used for “producing flexible electric cables for Bomarc ground-launching equipment at a significant saving in time and cost over handwinding or outside purchase. The machine was designed, built and in production in just 30 days.”
The Bomarc missile was a long-range supersonic weapon developed during the height of the Cold War by Boeing and the University of Michigan Aeronautical Research Center. Between 1957 and 1964, Boeing built 570 Bomarc missiles. They were housed in launch shelters located throughout the United States.
The cable winder consisted of four aluminum disks that each carried gimbaled wire spools. The disks were mounted on varying sizes of steel tubing and driven in opposite directions by geared line shafts through chains and sprockets.
“Threading of the machine is facilitated by quarter-inch tubes running from each wire-spool disk to the front of the machine,” explained ASSEMBLY. “A 14-inch diameter pulley at the front of the machine pulls the cable forward at the proper speed ratio to the rotating disks.
“The machine manipulates up to 84 strands of wire in a complex contra-helical layer—each layer spiraled in the opposite direction to its neighboring layer beneath—to produce cable automatically tapered as it emerges from the forming die,” added ASSEMBLY. “Four-layer cables of 16 AWG or smaller wire can be formed to a diameter of 1.25-inch at about 15-feet a minute.”
An article in the January 1976 issue of ASSEMBLY described how engineers at McDonnell Douglas Corp. (Boeing merged with the company in 1997) built a force amplifier in-house to improve productivity and address ergonomic issues. The device was developed by MD’s Actron division to manually process AWG 12-10 insulated wire used in the DC-10 jetliner.
“Butt splicing times have been reduced by almost 50 percent and unacceptable crimps virtually eliminated,” said ASSEMBLY. “Developed primarily to relieve the fatigue experienced by operators working with the larger wire sizes of wire harnesses for military and commercial aircraft, the force amplifier consists of an air cylinder with connecting levers arranged to exert force on the moving or pivoting arm or handle of a manual crimping tool.
“The handle is returned to the open position automatically,” the article pointed out. “The method of applying the pneumatic force is similar to the application of manual force, so tool performance conforms to the military standards for ratchet action crimping tools. The device is designed to accommodate a number of standard commercial and military hand crimping tools. Being light in weight, [it] can be moved from one location to another on a jig board or bench.”
Boeing engineers also experimented with innovative ways to automate wire harness assembly. Automation efforts began in the late 1960s when production of the new 747 jumbo jet was ramping up. A first-generation wire harness forming machine, built by Hughes Industrial Products, was delivered in 1970. It could form 50 wire bundles per aircraft.
“Although the machine was an improvement compared to manual operations, it was limited in speed and table size, and lacked programming flexibility,” claimed an article in the December 1977 issue of ASSEMBLY.
A second-generation machine dubbed the computer-controlled harness maker (CCHM) was deployed at Boeing’s Everett, WA, assembly plant in 1975. The machine featured three minicomputers and could produce wiring harnesses 16 times faster than manual methods. It could form a 747 harness in less than 45 minutes with no errors vs. 14 hours for a human.
“In addition to rapid speed, we are also able to reduce wire waste by building the wire bundles to more accurate dimensions,” quipped a Boeing engineer working on the CCHM project. “Forming electrical cables and harnesses no longer need be a tedious, inconsistent and expensive manual assembly operation.”
Today, Boeing is harnessing a variety of new technologies, such as wearable electronics, to improve the wiring harness assembly process. Engineers recently tested Google Glass to see if could help operators reduce work flow time and improve ergonomics. They also developed a voice-activated application to replace paper.
During the test, assemblers seamlessly saw work instructions appear in a view-finder. They could glide through multiple prompts by using gestures, such as voice control; the touchpad on the side of the glasses; and the head-tracking interface.
To learn more about Boeing’s unique manufacturing heritage, check out ASSEMBLY’s special section: A Century of New Frontiers