A. Field of the Invention
The present invention relates generally to the field of solid body construction, and more particularly to the fabrication of three-dimensional objects using particle deposition.
B. Description of the Related Art
In recent years, computer-aided design (CAD) technology has gained widespread acceptance in numerous engineering fields. Typical CAD systems permit the operator to design two- or three-dimensional constructs on a computer screen, then perform real-time rotation, translation and scaling operations with the on-screen image.
Many CAD systems also allow designation of a coordinate system, allowing the operator to relate each point of the two-or three-dimensional design to a corresponding point on the selected coordinate system. This capability facilitates interface to automated manufacturing systems, which construct or assist with construction of the finished design based on its spatial coordinate representation.
One method of automated manufacture is disclosed in U.S. Pat. No. 4,665,492, in which particles are sequentially deposited on a substrate according to the three-dimensional coordinate representation of the solid design. Several particle compositions and methods of deposition are described, including ejection of ceramic material in a heated environment, ejection of plastic material in an ionized atmosphere, and the use of slurry material in a sub-freezing environment. All of these techniques appear limited in their ability to produce constructs that contain oblique surfaces.
This difficulty stems from the need to maintain subjacent support of particles during the deposition process. Without such support, the angle between adjacent oblique layers is limited by the adhesion characteristics of the deposited material, as well as the size of the particles. Because particle mass varies with the cube of the radius while surface area depends on the square of the radius, very small particles may be needed for particular materials to be deposited at a desired angle. Thus, designs containing outwardly displaced features may be impossible to fabricate with presently available techniques, depending on the degree of displacement, fabrication material and particle size.
A second limitation of the method described in U.S. Pat. No. 4,655,492 relates to control of the ultimate spatial position of the deposited particle. The system described in this reference comprises two or more working heads to locate the point of deposition in space. This configuration must accommodate three degrees of freedom, resulting in the need for great control over movement of the working heads and precise monitoring of their positions.