The number of large composite surfaces that require sanding before bonding or painting is increasing rapidly as the Boeing 787 Dreamliner, Airbus A350 XWB and next-generation single-aisle jetliners enter rate production. So is the risk of pain and injury that surface preparation and finish personnel too often endure.
Sanding composite surfaces isn’t easy under any circumstances and is particularly difficult when the surface is vertical (e.g., a nacelle side), or overhead (e.g., a wing’s underside). The weight of the sander, the force required to abrade the surface and the time that sanding requires all contribute to the risk, not to mention worker fatigue and resulting poor finish quality. Hand/arm vibration syndrome (HAVS), which occurs when capillaries in the fingers close down after hours of operating a handheld sander or grinder, affects tens of thousands of workers and also can damage nerves, muscles and joints in the hand, wrist and arm. Its effects are cumulative and, with continued exposure, become permanent.
The U.S. Occupational Safety and Health Admin. (OSHA) does not yet limit worker vibration exposure, but watchdog agencies in Europe do. U.K. workers, for example, cannot hold a sander beyond defined exposure limits, which, in terms of time, are often less than half a work shift. Lack of regulation notwithstanding, most U.S. manufacturers are interested in reducing finishing-related worker injuries.
Temple Allen Industries (Rockville, Md.) says it has a remedy — one that also increases sanding quality and finishing productivity. Its Easily Manipulated Mechanical Arm (EMMA) is a pneumatically operated device developed during the Boeing 787 program to enable surface prep of composite wings and fuselages.
Notably, EMMA is not a robotic replacement for at-risk workers. Instead, it bears the weight of the sander or grinder, absorbs its vibrations, holds the tool flat on the workpiece surface, and applies downforce while the worker sits or stands nearby, using a joystick to control the sander’s movements.
Today, EMMA is approved for use on most commercial aircraft and is in use not only at Boeing (Renton, Wash.), but also at Airbus (Broughton, U.K.), Northrop Grumman (Palmdale, Calif.), Embraer (São José dos Campos, Brazil), British Airways (Harmondsworth, U.K.), Triumph Aerostructures – Vought Aircraft Div. (Milledgeville, Ga.) and by the U.S. Air Force and Navy. Additionally, a unit is being installed at a large wind blade manufacturing facility.
Watch EMMA in operation at www.templeallen.com/Videos.html.