Fusing three-dimensional (3d) object layers

A method of fusing a 3D object layer comprising:

• spreading a layer of build material onto a work area with two passes of a spreading roller, a first pass moving the roller from a first side to a second side of the work area, and a second pass moving the roller back to the second side;
• dispensing a liquid fusing agent onto the layer from a dispenser in a third pass that moves the roller and the dispenser together from the first side to the second side;
• returning the roller and dispenser to the first side in a fourth pass;
• and,
• continually irradiating the whole work area simultaneously and uniformly with fusing light except when the roller or dispenser pass over the work area and block the fusing light from reaching the work area.

A method of fusing with a stationary lighting assembly, comprising:

• spreading a first layer of powdered build material onto a platform in a first pass of a roller over the platform from a first side to a second side of the platform;
• spreading the first layer a second time in a second pass that moves the roller and a dispenser over the platform from the second side to the first side;
• parking the roller adjacent to the first side, and selectively dispensing a liquid fusing agent onto the first layer in a third pass that moves the dispenser from the first side to the second side;
• parking the dispenser adjacent to the second side, and spreading a next layer of powdered build material over the first layer;
• and,
• simultaneously and continuously irradiating the entire platform with fusing energy from a stationary lighting assembly such that the entire first layer receives a uniform amount of fusing energy.