An additive manufacturing system operates an extruder to extrude a swath of thermoplastic material through at least two nozzles of the extruder to form a swath of thermoplastic material along a path of relative movement between the extruder and a platform. The speed of the extruder along the path corresponds to a predetermined speed selected with reference to an orientation of the extruder and the angle for the path of relative movement between the extruder and the platform. A controller in the system operates at least one actuator operatively connected to at least one of the extruder and the platform to move the at least one of the extruder and the platform relative to the other of the extruder and the platform along the path of relative movement at the predetermined speed to make the swath of the thermoplastic material contiguous in a cross-process direction.