Pritz, K., Etzel, B., and Wei, Z., "Automatic Temporary Fastener Installation System for Wingbox Assembly," SAE Int. J. Aerosp. 9(1):181-184, 2016, doi:10.4271/2016-01-2085.
The automation cycle time of wing assembly can be shortened by the automated installation of single-sided temporary fasteners to provide temporary part clamping and doweling during panel drilling. Feeding these fasteners poses problems due to their complexity in design and overall heavy weight. In the past, Electroimpact has remotely fed these fasteners by blowing them through pneumatic tubing. This technique has resulted in occasional damage to fasteners during delivery and a complex feed system that requires frequent maintenance.Due to these issues, Electroimpact has developed a new fully automated single-sided temporary fastening system for installation of the LISI Clampberry fasteners in wing panels for the C919 wing factory in Yanliang, China. The feed system stores fasteners in gravity-fed cartridges on the end effector near the point of installation. The cartridge placement at the end effector eliminates the need for pneumatic feed tubes in addition to limiting input sensors to cartridge identification only. By reducing pneumatics, sensors, and controls, less maintenance is expected for the fastener storage system. When a fastener is requested by the machine, a pick and place mechanism grabs the correct fastener from the cartridge and loads the fastener into the fastener inserter. The fastener inserter then installs the fastener into the wing panel using a servo nut-runner to wind the fastener until the grippers pull the stack together with a specified preload. Diameter, grip length, and fastener integrity are all checked during the feed process.Extensive prototyping yielded results of 99.9% reliability across the spectrum of fasteners. Production hardware for this system has also passed Preliminary Acceptance Testing with Xi’an Aircraft Industry (Group) Company (XAC) and is currently installed and ready to start production.