Patent US 6,103,176

A rapid prototyping and manufacturing (e.g. stereolithography) method and apparatus for making three-dimensional objects with enhanced control of coating parameters used when forming layers of liquid or other fluid-like material in preparation for forming laminae of the object. The each lamina of the object is treated as either a primary laminae or secondary laminae. Only minority portions of the secondary layers are solidified when their associated layers are formed. Primary laminae are solidified in majority portions, along with previously unsolidified portions of secondary lamina, when their associated layers are formed. Recoating parameters are supplied for groups of primary layers and secondary layers such that coating formation may be controlled differently for primary layers and for secondary layers. Coating control for secondary layers may be based on the position of individual secondary layers, or sets of secondary layers, relative to the primary layers. The enhanced control leads to (1) more accurate layer formation, and/or (2) faster layer formation times for groups of successive layers.