Head unit, printing system and printing method

A head unit comprising:

• a head having a nozzle surface spreading in a first direction and a second direction crossing the first direction, the nozzle surface having a nozzle row formed along the first direction;
• a tank fluidly connected to the head;
• a substrate electrically connected to the head;
• a casing containing the head, the tank and the substrate;
• and
• an edge member defining an opening through which a tube and a wiring pass, the tube being fluidly connectable to the tank, the wiring being electrically connectable to the substrate, the edge member being configured to be detachably attachable with respect to the casing,
• wherein the edge member is configured to be attachable with respect to the casing selectively in a first state and a second state, the first state being a state in which the opening faces in a third direction crossing the first direction and the second direction, the second state being a state in which the opening faces in the first direction.