Liquid droplet jetting apparatus

A liquid droplet jetting apparatus comprising:

• a jetting head having a nozzle surface on which nozzles are aligned in a first direction, the jetting head configured to jet liquid droplets from the nozzles, the nozzles forming nozzle groups including two nozzle groups which are adjacent in the first direction;
• a conveyer configured to convey a recording medium in the first direction;
• and
• a controller;
• and
• a memory storing computer readable instructions that, when executed, cause the controller to:
• receive a printing data from an image scanner or an external device;
• determine a jetting timing for each of the nozzle groups based on the printing data;
• and
• execute a target printing to form a first image along the first direction in a first area on the recording medium, when the jetting head is at a first position in a second direction relative to the recording medium, the second direction being along the nozzle surface an intersecting the first direction;
• execute a preceding printing to form a second image along the first direction in a second area on the recording medium when the jetting head is at a second position in the second direction relative to the recording medium, the preceding printing performed immediately before the target printing, the second image being formed before the first image on the recording medium, the second area being in the same position as the first area of the recording medium in the second direction;
• and
• execute a succeeding printing to form a third image along the first direction in a third area on the recording medium when the jetting head is at a third position in the second direction relative to the recording medium, the succeeding printing performed immediately after the target printing, the third image being formed after the first image on the recording medium, the third area being in the same position as the first area and the second area of the recording medium in the second direction;
• wherein in a case of determining the jetting timing, the controller is configured to:
• determine a first spacing distance and a second spacing distance based on the printing data, the first spacing distance being a distance between a first target position located on the closest side to the second area of the recording medium in the first direction among landing target positions of the liquid droplets in the target printing and a second target position located on the closest side to the first area of the recording medium in the first direction among landing target positions of the liquid droplets in the preceding printing, the second spacing distance being a distance between a third target position located on the closest side to the third area of the recording medium in the first direction among the landing target positions of the liquid droplets in the target printing and a fourth target position located on the closest side to the first area of the recording medium in the first direction among landing target positions of the liquid droplets in the succeeding printing;
• in a case that both the first spacing distance and the second spacing distance are not more than a first threshold value, determine that a first condition is satisfied;
• in a case that at least one of the first spacing distance and the second spacing distance is greater than the first threshold value, determine that a second condition is satisfied;
• in a case that the first condition is satisfied, determine the jetting timing such that a target value of a shift amount in the second direction, between landing target positions of liquid droplets jetted from one nozzle group of the two nozzle groups and landing target positions of liquid droplets jetted from the other nozzle group of the two nozzle groups, is not less than a second threshold value;
• and
• in a case that the second condition is satisfied, determine the jetting timing such that the target value of the shift amount is less than the second threshold value.