Plastic article or earthenware shaping or treating: apparatus – Means applying electrical or wave energy directly to work – Radiated energy
Reexamination Certificate
1999-05-10
2001-01-30
Tentoni, Leo B. (Department: 1732)
Plastic article or earthenware shaping or treating: apparatus
Means applying electrical or wave energy directly to work
Radiated energy
C425S375000, C700S120000
Reexamination Certificate
active
06179601
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the formation of three-dimensional objects on substantially a layer-by-layer basis with enhanced resolution. The invention more particularly relates to the formation of three-dimensional objects by stereolithography utilizing techniques to overcome difficulties in recoating while maintaining acceptable or even enhanced layer resolution.
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. 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. Liquid-based stereolithography is disclosed in various patents, applications, and publications of which a number are briefly described in the Related Applications section hereinafter. 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). The present invention presents techniques for building high resolution objects by overcoming recoating problems that can exist when using such a 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 and/or reducing distortion.
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 and U.S. patent application Ser. No. 08/722,335,filed Sep. 27, 1996, now abandoned (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 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.
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 and/or to reduce object distortion. It is further believed that the techniques may have application in the LOM technologies to enhance object resolution when a minimum cutting depth is greater than the thickness of the individual sheets being used to form the object.
Various techniques for enhancing the resolution of three-dimensional objects formed using stereolithography have been described previously. In particular various techniques have been described in (1) U.S. Pat. No. 5,597,520 and its CIP, U.S. Pat. No. 5,999,184, both to Smalley, et. al ; (2) EP Laid Open Patent Application Publication No. 388 129 to Yamamoto; (3) U.S. Pat. No. 5,209,878 to Smalley, et.al; (4) Japanese Laid Open Patent Application Publication No. 2-95830A to Nakamura et. al; and (5) Japanese Laid Open Patent Application Publication No. 2-95831A to Kuribayashi, et. al.
The ′520 patent and ′951 application describe the use of Simultaneous Multiple Layer Curing Techniques in Stereolithography. These techniques address issues related to the formation of objects with resolution which is finer than a Minimum Solidification Depth (hereafter “MSD”) possessed by the building material. These techniques further address the formation of objects with finer resolution than a Minimum Recoating Depth (hereafter “MRD”) associated with the building material. MRD may be defined as the minimum thickness of coatings that can be reliably formed over previously solidified laminae. In strict layer-by-layer object formation, the MRD sets the minimum layer thickness that can be reliably used in forming the object. To obtain a desired resolution which is finer than the MRD (i.e. layer thickness thinner than the MRD), the techniques described in this application require complex data manipulations. There is a desire in the art for simpler techniques that can enhance resolution, while relying on less complex algorithms and building techniques (e.g. ones that use simpler data handling techniques).
Yamamoto, the ′129 publication, discloses the use of boundary exposures in association with alternating layers (i.e. layers N, N+2, N+4, etc.) and the use of raster exposures to solidify internal portions of laminae in association with the opposite alternating layers (i.e., N+1, N+3, N+5, etc.). According to the teachings of this reference, each pair of consecutive layers is exposed with the same shape, one exposing boundaries and the other exposing internal regions. The resolution increment for an object produced according to the teachings of this reference is equal to two layer thicknesses. The exposure of boundaries solidifies the material associated with the layer of the boundary only; while the exposure of internal regions solidifies material associated with not only the layer of exposure, but the previous layer as well. This publication does not achieve enhanced object resolution. Achieved object resolution is not based on the thickness of a single layer (i.e. thickness between consecutively applied coatings). This publication does not address the need for enhanced resolution, let alone the need for enhanced resolution in view of an MRD which is larger than desired. Furthermore, this reference fails to address any techniques for handling formation of outward facing regions that may be associated with any given lamina.
Smalley, et al., in the ′878 patent, discloses the use of thick structural laminae in combinati
Kruger Theodore R.
Manners Chris R.
Nguyen Hop D.
3-D Systems, Inc.
D'Alessandro Ralph
Tentoni Leo B.
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