A modular inkjet printhead assembly including a plurality of jetting modules for printing on a print medium traveling along a media path from upstream to downstream, comprising:
- a rail assembly spanning the print medium in a cross-track direction, the rail assembly having an upstream side and a downstream side, the rail assembly including:
- a beam;
- and
- a rod attached to a side of the beam that faces the print medium;
- a plurality of printhead modules, each printhead module including a corresponding jetting module, wherein each jetting module includes:
- an array of nozzles extending in a cross-track direction,
- wherein the nozzles are adapted to eject drops of fluid in a drop ejection direction;
- a first alignment tab having a first alignment datum and a second alignment datum;
- a second alignment tab having a third alignment datum and a fourth alignment datum, the second alignment tab being spaced apart from the first alignment tab in the cross-track direction;
- a rotational alignment feature including a fifth alignment datum;
- and
- a cross-track alignment feature including a sixth alignment datum;
- a jetting module clamping mechanism for each jetting module for applying a force to the associated jetting module that causes the first alignment datum, the second alignment datum, the third alignment datum and the fourth alignment datum of the associated jetting module to engage with the rod and causes the fifth alignment datum of the associated jetting module to engage with a corresponding rotational alignment feature associated with the beam;
- and
- a jetting module cross-track force mechanism for each jetting module for applying a cross-track force to the associated jetting module that causes the sixth alignment datum of the associated jetting module to engage with a corresponding cross-track alignment feature associated with the beam;
- wherein each jetting module is adapted to engage with the rail assembly at a different cross-track position, with at least one of the jetting modules is an upstream jetting module engaging with the rail assembly on the upstream side of the rail assembly and at least one of the jetting modules is a downstream jetting module engaging with the rail assembly on the downstream side of the rail assembly;
- and
- wherein portions of the first and second alignment tabs of each jetting module are adapted to fit within corresponding notches in the beam;
- and
- wherein the rail assembly is located at a position along the media path where the print medium is wrapping around a roller or a curved platen, and wherein the rotational alignment features associated with the beam and the jetting modules are adapted to tilt the upstream jetting modules or the downstream jetting modules or both the upstream and downstream jetting modules away from the beam such that the drop ejection direction for the tilted jetting modules is tilted toward a surface normal of the print medium on the corresponding side of the rail assembly such that the drop ejection direction for the upstream jetting modules is not parallel to the drop ejection direction for the downstream jetting modules.