Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
2000-01-18
2003-09-16
Paladini, Albert W. (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S119000, C700S120000, C264S401000
Reexamination Certificate
active
06622062
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the formation of three-dimensional objects using a Rapid Prototyping and Manufacturing (RP&M) technique (e.g. stereolithography). The invention more particularly relates to the formation of three-dimensional objects using data that has been modified to account for the line width induced in the building material (e.g. photopolymer) by a formation tool (e.g. a laser beam).
BACKGROUND OF THE INVENTION
1. Related Art
Rapid Prototyping and Manufacturing (RP&M) is the name given to a field of technologies that can be used to form three-dimensional objects rapidly and automatically from three-dimensional computer data representing the objects. RP&M can be considered to include three classes of technologies: (1) Stereolithography, (2) Selective Deposition Modeling, and (3) Laminated Object Manufacturing.
The stereolithography class of technologies create three-dimensional objects based on the successive formation of layers of a fluid-like medium adjacent to previously formed layers of medium and the selective solidification of those layers according to cross-sectional data representing successive slices of the three-dimensional object in order to form and adhere laminae (i.e. solidifed layers). One specific stereolithography technology is known simply as stereolithography and uses a liquid medium which is selectively solidified by exposing it to prescribed stimulation. The liquid medium is typically a photopolymer and the prescribed stimulation is typically visible or ultraviolet electromagnetic radiation. The radiation is typically produced by a laser. Liquid-based stereolithography is disclosed in various patents, applications, and publications of which a number are briefly described in the Related Applications section hereafter. Another stereolithography technology is known as Selective Laser Sintering (SLS). SLS is based on the selective solidification of layers of a powdered medium by exposing the layers to infrared electromagnetic radiation to sinter or fuse the particles. SLS is described in U.S. Pat. No. 4,863,538 to Deckard. A third technology is known as Three Dimensional Printing (3DP). 3DP is based on the selective solidification of layers of a powdered medium which are solidified by the selective deposition of a binder thereon. 3DP is described in U.S. Pat. No. 5,204,055 to Sachs.
The present invention is primarily directed to stereolithography using liquid-based building materials (i.e. medium). It is believed, however, that the techniques of the present invention may have application in the other stereolithography technologies for the purposes of enhancing resolution while maintaining aesthetic appeal of the objects being formed.
Selective Deposition Modeling, SDM, involves the build-up of three-dimensional objects by selectively depositing solidifiable material on a lamina-by-lamina basis according to cross-sectional data representing slices of the three-dimensional object. One such technique is called Fused Deposition Modeling, FDM, and involves the extrusion of streams of heated, flowable material which solidify as they are dispensed onto the previously formed laminae of the object. FDM is described in U.S. Pat. No. 5,121,329 to Crump. Another technique is called Ballistic Particle Manufacturing, BPM, which uses a 5-axis, ink-jet dispenser to direct particles of a material onto previously solidified layers of the object. BPM is described in PCT publication numbers WO 96-12607; WO 96-12608; WO 96-12609; and WO 96-12610, all assigned to BPM Technology, Inc. A third technique is called Multijet Modeling, MJM, and involves the selective deposition of droplets of material from multiple ink jet orifices to speed the building process. MJM is described in U.S. Pat. No. 5,943,235 to Earl et al. and U.S. patent application Ser. No. 08/722,335 (both assigned to 3D Systems, Inc. as is the instant application).
Though, as noted above, the techniques of the instant invention are directed primarily to liquid-based stereolithography object formation, it is believed that the techniques may have application in the SDM technologies to enhance object resolution for a given droplet or stream size while still maintaining aesthetic appeal of the objects being formed.
Laminated Object Manufacturing, LOM, techniques involve the formation of three-dimensional objects by the stacking, adhering, and selective cutting of sheets of material, in a selected order, according to the cross-sectional data representing the three-dimensional object to be formed. LOM is described in U.S. Pat. Nos. 4,752,352 to Feygin; and 5,015,312 to Kinzie, and in PCT Publication No. WO 95-18009 to Morita. It is believed that the techniques may have application in the LOM technologies to enhance object resolution when using laser beam or mechanical cutting tool to cutout cross-sections while still maintaining aesthetic appeals of the objects being formed.
Various techniques for compensating for the width of solidification induced by a beam when forming objects using stereolithography have been described previously. In particular various techniques have been described in (1) U.S. Pat. No. 5,184,307 to Hull et al., and 2) U.S. Pat. No. 5,321,622 to Snead et al.
The '307 patent describes techniques for transforming three-dimensional object data into cross-sectional data for use in stereolithographic production of the objects. The derived cross-sectional data is typically divided into one or more groups of vectors. These groups of vectors typically include one or more boundary types (vectors that surround a given portion of a cross-section), one or more fill types that fall within selected boundary regions (sets of vectors that are typically parallel and closely spaced so that upon exposure the entire region is solidified), and one or more hatch types that fall within selected boundary regions (sets of vectors that are typically parallel but may be widely spaced so that some unsolidified material remains between the individually exposed lines). Prior to creating the fill and hatch, this reference teaches that selected boundaries should be offset inward (i.e. toward the object region as opposed to toward a non-object region) by an appropriate amount to account for the solidification width induced by the beam that is used to solidify the material. The offset amount is typically equal to about one half the width of solidification induced by the beam of radiation used to induce solidification.
One technique disclosed in the '307 patent compensates boundaries by:
(1) Forming boundary vectors into loops;
(2) Offsetting each vector into the object by the half a line width; and
(3) Recalculating the endpoints and remove vectors that change orientation.
A second technique disclosed in the '307 patent compensates boundaries by:
(1) Forming boundary vectors into loops,
(2) Deriving a displacement vector for each vertex of the boundary loop. The displacement vector should bisect the angle formed by the two boundary vectors that form the vertex. The displacement vector generally has a length equal to D/[(1−cos &thgr;)/2)]
{fraction (1/12)}
, where D=about ½ the line width, and
where &thgr;=angle between the two vectors. This offset amount is used unless the length is greater than a preset maximum amount (e.g. 2*LWC) in which case the length is limited to that preset maximum amount. Furthermore the length of the offset vector was limited to so that it would not extend beyond the midpoint of each of the two boundary vectors giving rise to it as dictated by a perpendicular bisector extending to those each of the two boundary vectors.
A third technique combines benefits of the first two techniques. The boundary vectors are moved inward by the desired amount as in the first technique. If this offset results in a vertex moving in by more than a desired amount an additional vector is added to the compensated boundary. This additional vector extends from (1) the intersection point of the two offset vectors to (2) a point that is a desired dista
Earl Jocelyn M.
Manners Chris R.
3-D Systems, Inc.
D'Alessandro Ralph
Garland Steven R.
Paladini Albert W.
Smalley Dennis
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