May 3, 2010
Drilling hundreds of small diameter holes in cured composite skins laminates is a processing challenge which makes fabrication of acoustic panels for engine nacelles a difficult and expensive task.
Commercial aircraft engine nacelles have used composite acoustic panels for noise abatement since the 1970’s. Nacelles typically have acoustic panels at several locations in the bypass air duct. Noise abatement technology requires the use of a honeycomb sandwich design with hundreds of small holes on the air passage surface of the panel. Fabrication of the composite sandwich panel is not a major problem. However, producing the close tolerance hole pattern on the air passage surface of the panel is a manufacturing challenge and typically an expensive process step in producing an acoustic panel.
Two (2) processes are commonly used to produce the close tolerance hole pattern in nacelle acoustic panels ….molding of the holes in the uncured inner facesheet of the acoustic panel …. and secondary drilling of the hole pattern in the cured facesheet of the acoustic panel.
Royal’s engineering team found that while tool geometry, chip load, and programming are important factors; CVD coating and adhesion, spindle power, and tool handling are critical factors to reduce production time and increase hole quality. Tweaks in programming alone resulted in a 50% reduction in run time.