Print merging is when the FieldPrinter prints several nearby lines at the same time — in a single pass, with one cartridge — instead of printing each line on its own pass. It isn't limited to two lines: the robot prints as many lines as fit within one 1" print lane together. This article explains what decides whether lines merge, so you can predict the result when you review a layout.

What print merging is

The FieldPrinter lays down ink inside a print lane that is 1" wide — the band one cartridge covers in a single pass. Every line in your file whose printed ink fits inside that 1" lane is printed together in one pass. That can be two lines, three, or more — whatever fits.

Merging happens automatically while the robot prints. There is no setting to turn on or off — it is governed entirely by how wide your lines are and how far apart they sit.

How a line's width and position work

Two facts about how the robot prints a line determine whether it can share a lane with its neighbors:

• A line is printed centered on its location in the file. The printed ink straddles the line's centerline — the exact position you drew.
• Half of the line's width falls on each side of that centerline. For a 1/8" wide line, the ink reaches 1/16" past the centerline on each side.

So the outer edge of any line sits half its width beyond the centerline you drew.

The rule: everything must fit within the 1" lane

A group of lines merges into one pass when the whole group fits inside a single 1" lane — measured from the outer edge of the outermost line on one side to the outer edge of the outermost line on the other side. Because each outer edge sits half a line's width past its centerline:

(spread between the two outermost centerlines)
  + (half the width of one outer line)
  + (half the width of the other outer line)
  ≤ 1"

Any additional lines that sit between those two outer lines are merged into the same pass automatically — there's no separate limit on how many.

Simplest case: two lines of equal width

For just two lines of the same width, the rule reduces to a maximum spacing between their centerlines of 1" minus the line width:

Example: two 1/8" lines each reach 1/16" past their centerline → max spread = 1" − 1/16" − 1/16" = 7/8".

For two lines of different widths, subtract half of each. Example: a 1/8" line next to a 1/4" line → 1" − 1/16" − 1/8" = 13/16".

What happens when lines don't fit in one lane

If the lines spread wider than a single 1" lane, they can't all print in one pass. The robot prints them across separate passes instead — the lines still come out correctly, they just aren't combined.