Bridging internal channels in 3d-printed objects

A printing system for three-dimensional objects, comprising:

• a reservoir configured to receive and melt a print material;
• an ejector having a nozzle that is fluidly connected to the reservoir to receive melted print material from the reservoir;
• a platform positioned opposite the ejector;
• at least one actuator operatively connected to at least one of the platform and the ejector, the at least one actuator being configured to move the at least one of the platform and the ejector relative to one another;
• and
• a controller operatively connected to the reservoir, the ejector, and the at least one actuator, the controller being configured to:
• deposit a plurality of drops of a printing material in a first direction to form a supported stepout onto an edge of a bridging layer;
• deposit a plurality of drops of the printing material to form an anchor layer adjacent to and in contact with the supported stepout;
• and
• deposit a plurality of drops of the printing material to form an unsupported stepout adjacent to an in contact with the supported stepout;
• and wherein
• the anchor layer is formed with a first drop spacing
• the unsupported stepout is formed with a second drop spacing;
• the first drop spacing is from about 1.75 times to about 2.50 times that of the second drop spacing;
• and
• an internal bridge formed by the unsupported stepout and the anchor layer are disposed at an angle relative to the edge of the bridging layer of 0 degrees to about 30 degrees.

A method of printing an internal bridge in a three-dimensional object, comprising:

• calculating a number of unsupported stepout layers, n, in the internal bridge based on a lateral dimension of an overhang of the internal bridge divided by a line width;
• depositing an anchor layer in a first direction at a first drop spacing;
• and
• depositing an unsupported stepout in a second direction at a second drop spacing;
• wherein:
• the second direction is opposite of the first direction.