Droplet placement onto surfaces

A method of inkjet printing comprising:

• substantially aligning at least one of a group of inkjet nozzles with a first arcuate line segment on arcuately moving print media;
• ejecting at least one droplet from said one nozzle onto a target on said first segment;
• moving said group of nozzles in a direction having a component orthogonal to said first segment to respectively align second and first nozzles in said group with said first segment and with a second line segment parallel to said first segment;
• ejecting droplets from said nozzles onto targets in said segments, a center to center spacing of adjacent targets in said segments equaling one or a multiple of a center to center spacing of nozzles in a direction orthogonal to said segments.

A method of inkjet printing comprising:

• sequentially positioning an increasing number of a plurality of inkjet nozzles for movement in a helical line relative to an object to eject ink droplets onto targets on circular segments on said object, said plurality of nozzles having a center to center spacing in a direction orthogonal to said segments equal or less than center to center spacing of adjacent targets on said segments;
• arcuately moving said targets relative to said nozzles;
• and
• ejecting droplets from said nozzles onto selected targets on a first of said segments while moving said nozzles in a direction having a component parallel to the axis of said helical line at a speed to provide desired axial spacing between adjacent turns of said line.

An inkjet printing apparatus comprising:

• a rotatable support providing targets on a number of spaced parallel line segments on an arcuate surface of said support;
• means for rotating said support about an axis of said arcuate surface;
• an inkjet printhead having nozzles proximate said surface for ejecting fluid droplets of selected size onto said targets, said nozzles being arranged in at least one pattern containing a number of nozzles equal or greater than said number of targets in one of said segments;
• and
• means for moving said printhead in a direction having a component parallel to said axis in timed relation with the tangential speed of said targets on said support to print on selected targets on said spaced parallel line segments.

An inkjet printing apparatus comprising:

• a rotatable support providing targets on a number of spaced parallel line segments on an arcuate surface of said support, said support being rotatable about an axis defining said arcuate surface;
• an inkjet printhead having nozzles oriented to eject fluid droplets of selected size onto said targets, said nozzles being arranged in at least one pattern containing a number of nozzles equal or greater than said number of targets in one of said segments;
• and
• said printhead being moveable in a direction having a component parallel to said axis in timed relation with the tangential speed of said targets on said support to print on selected targets on said spaced parallel line segments.

A method of inkjet printing on a cylindrical surface, comprising:

• rotating the cylindrical surface about a rotational axis at a rotational velocity;
• scanning an arrangement of nozzles over the cylindrical surface along a scanning axis at a scanning velocity, the scanning axis having a direction substantially parallel to the rotational axis;
• and
• selectively ejecting fluid drops from individual ones of the nozzles during the rotating and scanning so as to print a pattern on the cylindrical surface, where the rotational velocity and the scanning velocity have a predefined relationship to an effective nozzle density in the scanning axis direction and to a print density in a direction orthogonal to said rotational axis.