Zieve, P., Rudberg, T., Vogeli, P., Smith, A. et al., "A Two Tower Riveting Machine with a True Z Axis," SAE Technical Paper 2004-01-2807, 2004, doi:10.4271/2004-01-2807.
The A380 aircraft is the largest passenger aircraft ever built and an appropriate machine was required to accomplish the fastening of the wing plank to stringer and buttstrap joints. The lower wing panels are curved along the length and move 1.42m out of plane. All previous E4000 machines had clampup heads that would extend and retract whatever distance was required to contact the wing panel. To improve toolpoint alignment, Electroimpact added a Z-axis that moves the yoke in order to reduce the necessary travel envelope of the clamp table axes and to cause them to clamp in the same plane regardless of panel position along the Z-axis.