Abstract: A printhead for three-dimensional printing features a mixing cavity and a mixing rotor with a mixing portion disposed within the mixing cavity. The mixing rotor is operated by a motor to mix at least one polymeric stream received in the mixing cavity. The system further includes a control valve having a seat and a valve stem. The valve stem is mounted such that at least a portion thereof traverses through a void made along the mixing rotor. A pressure-generating mechanism advances the polymeric stream in a downstream direction into the mixing cavity and further through the flow passage of the control valve toward the outlet of the printhead. Linear movement or rotation of the valve stem is used to control the form of the flow passage and, therefore, the flow of the polymeric stream through the printhead.

Abstract: Methods for additive manufacturing of objects comprising a polymeric foam are disclosed and comprise extruding a mixture of a base polymer and a foaming agent that are provided in the form of at least one feedstock material, the mixture produced by admixing the base polymer and the foaming agent within a polymer processing space of an extruder by an independent mixing rotor, and further comprise sequentially depositing multiple layers of the mixture to form a three-dimensional object. Heating of the mixture to cause activation of the foaming agent and formation of the polymeric foam may be done during the extrusion process or afterward by a separate heating step.