Plastic and nonmetallic article shaping or treating: processes – Stereolithographic shaping from liquid precursor
Reexamination Certificate
1999-02-08
2002-06-04
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Stereolithographic shaping from liquid precursor
C264S308000, C264S497000, C425S135000, C425S174400, C425S375000, C700S119000, C700S120000
Reexamination Certificate
active
06399010
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to improved formation of three-dimensional objects from a fluid-like medium on a substantially layer-by-layer basis. The invention more particularly relates to the improved formation of three-dimensional objects by stereolithography utilizing techniques to overcome difficulties in quickly forming objects with minimized distortion.
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. Rapid prototyping and manufacturing 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 creates three-dimensional objects by successively forming layers of a fluid-like medium adjacent to previously formed layers of medium and selectively solidifying these layers to form and adhere laminae (i.e. solidified layers). These laminae are solidified according to cross-sectional data representing successive slices of the three-dimensional object. Typically, adhesion between successive laminae occurs by chemical bond formation between the two laminae (e.g. inter-lamina cross-linking) during polymerization. In alternative embodiments, it is possible that adhesion could occur by application of a separate adhesive or by other mechanical bonding. In summary, adhesion may occur via an adhesive or cohesive phenomenon.
One specific stereolithography technology is known simply as stereolithography, and it uses a liquid medium that is selectively solidified by exposing it to stimulation. The liquid medium is typically a photopolymerizable material (i.e. resin) and the 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 Patents, Applications and Publications section hereinafter. Another stereolithography technology is known as selective laser sintering (SLS). Selective laser sintering 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. Selective laser sintering is described in U.S. Pat. No. 4,863,538 issued Sep. 5, 1989, to Deckard. A third technology is known as three-dimensional printing (3DP). Three-dimensional printing is based on the selective solidification of layers of a powdered medium which are solidified by the selective deposition of a binder thereon. Three-dimensional printing is described in U.S. Pat. No. 5,204,055 issued Apr. 20, 1993, to Sachs, et al.
The present invention is primarily directed to stereolithography using liquid-based building materials (i.e. medium). It is believed, in addition, that the techniques of the present invention may have application in the other stereolithography technologies for the purposes of reducing distortion and/or speeding object formation.
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. Fused deposition modeling is described in U.S. Pat. No. 5,121,329 issued Jun. 9, 1992, 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. Ballistic particle manufacturing is described in PCT Publication Nos. WO 96/12607 published May 2, 1996, by Brown, et al.; WO 96/12608 published May 2, 1996, by Brown et al.; WO 96/12609 published May 2, 1996, by Menhennett et al.; and WO 96/12610 published May 2, 1996, by Menhennett et al. A third technique called multijet modeling (MJM) involves the selective deposition of droplets of material from multiple ink jet orifices to speed the building process. Multijet modeling is described in PCT Publication Nos. WO 97/11835 published Apr. 3, 1997, by Earl et al.; and, WO 97/11837 published Apr. 3, 1997, by Leyden et al. (both assigned to 3D Systems, Inc., as is the instant application).
Laminated object manufacturing (LOM) techniques involve the formation of three-dimensional objects by the stacking, adhering, and selective cutting, in a selected order, of sheets of material, according to the cross-sectional data representing the three-dimensional object to be formed. Laminated object manufacturing is described in U.S. Pat. No. 4,752,352 issued Jun. 21, 1988, to Feygin; and U.S. Pat. No. 5,015,312 issued May 14, 1991, to Kinzie; and in PCT Publication WO 95/18009 published Jul. 6, 1995, by Morita et al.
As noted above, the techniques of the instant invention are directed primarily to liquid-based stereolithography object formation. However, it is believed that the techniques may be applied in the selective deposition modeling technologies to reduce object distortion and/or to decrease object formation time. Some of the selective deposition modeling technologies may use a technique sometimes referred to as “Minimum Layer Seconds”. This technique requires that a minimum amount of time lapse from the beginning of building one layer to the beginning of building the next layer, so that there is sufficient time for heat built up in the layer to dissipate. If a layer takes less than the Minimum Layer Seconds to build, the balance of the Minimum Layer Seconds is counted down before beginning the next layer. If a delay occurs, it occurs after the layer is completely built. This technique does not teach or suggest the partial creation of a lamina, then a delay, then the completion of the lamina.
Various techniques for decreasing distortion, and techniques that utilize multiple exposures of an ultraviolet-curable fluid during creation of three-dimensional objects formed using stereolithography, have been described previously, such as, for example: (1) U.S. Pat. No. 5,104,592 issued Apr. 14, 1992, to Hull et al., (2) Japanese Laid Open Patent Application 63-145015A published Jun. 17, 1988, by Itarni et al., (3) U.S. Pat. No. 4,945,032 issued Jul. 31, 1990, to Murphy et al., (4) Appendix A of U.S. Pat. No. 4,575,330 issued Mar. 11, 1986, to Hull, (5) European Patent 0 250 121 B1 issued Nov. 2, 1994, to Pornerantz et al., and (6) U.S. Pat. No. 5,965,079 to Gigi et al. assigned to 3D Systems, Inc.
U.S. Pat. No. 5,104,592 issued Apr. 14, 1992, to Hull et al., discloses various stereolithography techniques for reducing curl distortion. The first curl reduction technique disclosed is the “dashed line” technique, in which a stereolithography line that is part of a vertical or horizontal formation is drawn with breaks in the line instead of a solid line. Thus, the pulling force normally transmitted along the vector is reduced, and the curl effect is reduced. The second curl reduction technique is the “bent-line” technique, in which a stereolithography line that is part of a vertical or horizontal formation is drawn with bends in the line instead of a straight line. In this way, the pulling force normally transmitted along the vector is reduced, and the curl effect is reduced. The third curl reduction technique is the “secondary structure” technique, in which a stereolithography line which is part of a vertical or horizontal formation is drawn so that it does not adhere directly to the line below or beside it, but is attached, after it is formed, with a secondary structure. As such, the pulling force down the vector is eliminated, the bending moment on adjacent lines is reduced,
Guertin Michelle D.
Hull Charles W.
Nguyen Hop D.
3-D Systems, Inc.
Bishop Laura
D'Alessandro Ralph
Tentoni Leo B.
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