Method and apparatus for fabricating three dimensional models

A method for fabricating a three-dimensional model having at least one void region, the method comprising the steps of:

• fabricating a composite model formed of a plurality of successive layers including a model material forming the three-dimensional model and a sacrificial mold material forming a sacrificial mold for the model material, wherein each successive layer formed by the steps of:
• (a) depositing at least one line of the sacrificial mold material to delineate at least one boundary of the model material within the layer by a drop-by-drop deposition, including
• in each layer having the at least one void region, depositing lines of the sacrificial mold material in a grid pattern to delineate a region of the layer included in the at least one void region, whereby the grid patterns in successive layers in the at least one void region form partitions of sacrificial mold material that form filler spaces for receiving the model material to form filler elements of model material separated by the sacrificial mold material partitions occupying the at least one void region so that, concurrently with fabrication of the three-dimensional model, the at least one void region is filled by a plurality of the filler elements, formed of model material and enclosed within the sacrificial mold material partitions, and each filler element is smaller than the at least one void region so as to facilitate removal of the filler elements through an access opening of the at least one void region upon removing the sacrificial mold material;
• (b) depositing the model material onto regions of the layer delineated by the at least one boundary of the model material at a rate faster than a rate at which the sacrificial mold material is deposited;
• (c) removing a thickness of the sacrificial mold material and the model material to reduce the fabricated layer to a selected thickness of the sacrificial mold material and the model material;
• and
• (d) repeating steps (a) through (c) until the composite model is completed, and
• (e) separating the three-dimensional model from the composite model by removing the sacrificial mold material by a process affecting only the sacrificial mold material, including,
• removing the sacrificial mold material from the composite model to release the filler elements from the composite model thereby to form the at least one void in the three-dimensional model.