Abstract: A melt stream flow path is formed in the fixed part (20) of an injection moulding tool (12). A sonotrode (38) is arranged for direct contact with moulding material passing through the flow path in use, for directly vibrating the material and thus improving the melt flow characteristics of the moulding material as material is being injected into the tool (12). The sonotrode 38 extends directly into the flow path, or forms part of the wall of the flow path. An extrusion apparatus (50, 80) is also provided with a sonotrode (38) extending directly into a flow path, or forming part of the wall of a flow path formed in a modified die block.