RAPID PROTOTYPING AND TOOLING SYSTEM

A solid freeform fabrication process and apparatus for making a three-dimensional object. The process comprises the steps of (1) operating a material deposition sub-system for dispensing droplets of solidifiable liquid compositions on demand onto selected spots of an object work surface, for using a focused heat source to maintain a heat-affected zone on the work surface, and for creating a weld pool of molten materials on this work surface by injecting selected powder particles into this heat-affected zone and (2) during the material deposition process, moving the deposition sub-system and the work surface relative to each other in an X-Y plane defined by first and second directions and in a Z direction orthogonal to the X-Y plane so that the materials are deposited to form a first layer of the object. The material in the weld pool solidifies after the heat-affected zone moves away to build portions of a layer. These steps are repeated to deposit multiple layers for forming a three-dimensional shape. Preferably, the peripheral areas and the staircase step zones between layers are built with fine droplets for improved part accuracy while the bulk of the object is built with solidification of weld pool materials. These steps are preferably executed under the control of a computer system. Preferably, the system is also operated to generate a support structure for any un-supported feature of the object.