Simplified stereolithographic object formation methods of overcoming minimum recoating depth limitations

Abstract

A rapid prototyping and manufacturing (e.g. stereolithography) method and apparatus for making high resolution objects utilizing low resolution materials which are limited by their inability to reliably form coatings of a desired thickness. The formation of coatings of such materials is limited to a Minimum Recoating Depth (MRD), when formed over entirely solidified laminae, which is thicker than the desired layer thickness or object resolution. Data manipulation techniques result in layers of material (and laminae) of the object being categorized as non-consecutive primary layers (laminae) and secondary layers (laminae) positioned intermediate to the primary layers (laminae). Substantially, all portions of primary laminae are exposed in association with primary layers and portions of the secondary laminae are formed in association with their respective secondary layers while other portions of the secondary laminae are formed in association with primary layers so as to form the object with a higher resolution than that dictated by the spacing between the primary layers. Recoating techniques are described which can be used when the thickness between consecutive layers is less than a leading edge bulge phenomena that results from the use of a particular recoating device such that direction of sweeping and/or order of sweeping of the recoating device is varied between consecutive primary layers.