Additive manufacturing

A fusing system for an additive manufacturing machine, comprising:

• a first carriage carrying a layering device to layer build material over a work area and a fusing lamp to irradiate build material in the work area with a fusing light;
• a second carriage carrying an agent dispenser to dispense a fusing agent;
• the first carriage and the second carriage movable back and forth over the work area along the same line of motion so that the first carriage follows the second carriage in a first direction and the second carriage follows the first carriage in a second direction opposite the first direction;
• and
• a controller operatively connected to the first carriage, the fusing lamp, the second carriage, and the agent dispenser, the controller including processor executable instructions to:
• while moving the first carriage over the work area in the first direction in a first pass, layer build material over an object structure to form a layer of build material;
• while moving the first carriage and the second carriage over the work area in the second direction in a second pass, dispense a first fusing agent on to build material in the layer with the agent dispenser;
• while moving the second carriage and the first carriage over the work area in the first direction in a third pass, dispense a second fusing agent the same as or different from the first fusing agent on to build material in the layer with the agent dispenser and then irradiate build material in the layer with the fusing lamp;
• and
• while moving the first carriage over the work area in the second direction in a fourth pass, irradiate build material in the layer with the fusing lamp.

A processor readable medium having instructions thereon that when executed cause a fusing system for an additive manufacturing machine to:

• in a first carriage pass, layer build material over an object structure to form a layer of build material;
• in a second carriage pass, irradiate build material in the layer and then dispense a first fusing agent and/or a first detailing agent on to build material in the layer;
• in a third carriage pass, dispense a second fusing agent the same as or different from the first fusing agent and/or a second detailing agent the same as or different from the first detailing agent on to build material in the layer and then irradiate build material in the layer;
• and
• in a fourth carriage pass, irradiate build material in the layer.

A fusing system for an additive manufacturing machine, comprising:

• a first carriage carrying a layering device to layer build material over a work area, a heating lamp to heat build material in the work area, and a fusing lamp to irradiate build material in the work area with a fusing light, the heating lamp having a first color temperature and the fusing lamp having a second color temperature higher than the first color temperature;
• a second carriage carrying an agent dispenser to dispense a fusing agent;
• and
• the first carriage and the second carriage movable back and forth over the work area along the same line of motion so that the first carriage follows the second carriage in a first direction and the second carriage follows the first carriage in a second direction opposite the first direction.