Registration of duplex printed sheets in a sheet stacking device

A method of printing and stacking sheets comprising the steps of:

• registering a sheet on a first pass of the sheet past a skew angle correction system;
• moving the registered sheet on the first pass past a printhead assembly for printing a front image on a first side of the sheet;
• detecting a skew angle between a first edge and a second edge of the sheet;
• registering the sheet on a second pass of the sheet past the skew angle correction system;
• moving the registered sheet on the second pass past the printhead assembly for printing a back image on a second side of the sheet, wherein in the first and second passes the respective front and back images have been aligned with respect to the first edge of the sheet by and applying the skew angle;
• and
• after the second pass, stacking the sheet, wherein the first edge of the sheet is registered to a registration element of a sheet stacking device having a predetermined stacking reference direction.