In order to position “endless” unidirectional prepreg layers on large tools, the automatic tape laying (ATL) technology is used. The technology became relevant for airframe series production during the 1980s, starting with planar lay ups for smaller parts, and has step by step been improved until today also for large and more complex shaped parts, below Table . This is also due the fact that the pure size of the component, for example a wing skin, requires the use of automated equipment. The tape laying head can be mounted on a portal, allowing for controlled movements in x and y as well as in z-direction, plus the necessary axis rotations to position the head vertically to the surface. The laying head carries the prepreg material. It is clamped and pulled by rollers, and laid down onto the tool in 0 , + and 45 and 90 direction, according to the laminate stacking sequence defined by design. A roll applies a defined pressure in z-direction in order to achieve the necessary adhesion of the tape on the layer underneath and to provide a pre-compaction of the laminate.
Modern ATL machines typically work with 300 mm tape width at maximum processing speeds of up to 300 m/h (equivalent to a deposition rate of approx. 15–20 kg/h, depending on the prepreg areal weight) and can handle typical curvatures and surface geometries needed for aerofoils (wing skins). However, deposition rates are reduced in case doublers (local thickenings) are necessary. The ramping of plies in order to cope with local thickness changes is possible in certain limits. As the length of the tapes on one roll is limited (to approx. 300 m) but several km of tape can be needed for a wing skin or a tail plane skin, the process has to be interrupted for material change.