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 material adjacent to previously formed layers of material 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. solidified layers). One specific stereolithography technology is known simply as stereolithography and uses a liquid material that is selectively solidified by exposing it to prescribed stimulation. The liquid material is typically a photopolymer and the prescribed stimulation is typically visible or ultraviolet electromagnetic radiation. The radiation is typically produced by a laser though other sources of radiation are possible such as arc lamps, resistive lamps, and the like. Exposure may occur by scanning a beam or by controlling a flood exposure by use of a light valve that selectively transmits or reflects the radiation. 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 material by exposing the layers to infrared electromagnetic radiation to sinter or fuse the powder particles. SLS 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). 3DP is based on the selective solidification of layers of a powdered material which are solidified by the selective deposition of a binder thereon. 3DP is described in U.S. Pat. No. 5,204,055, issued Apr. 20, 1993, 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.
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. The material being dispensed may be solidified upon cooling, by heating, exposing to radiation, or upon application of a second physical material. A single material may be dispensed or multiple materials dispensed with each having different properties. 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, 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. BPM is described in PCT publication numbers WO 96-12607, published May 2, 1996, by Brown; WO 96-12608, published May 2, 1996, by Brown; WO 96-12609, published May 2, 1996, by Menhennett; and WO 96-12610, published May 2, 1996, by Menhennett. 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, filed Sep. 27, 1996, and issued Aug. 24, 1999 to Earl et al. and in U.S. Application Ser. No. 08/722,335, filed Sep. 27, 1996, by Leyden et al. 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. No. 4,752,352, issued Jun. 21, 1988, to Feygin, U.S. Pat. No. 5,015,312, issued May 14, 1991, to Kinzie, and U.S. Pat. No. 5,192,559, issued Mar. 9, 1993, to Hull et al.; and in PCT Publication No. WO 95-18009, published Jul. 6, 1995, by Morita.
Though, as noted above, the techniques of the instant invention are directed primarily to liquid-based stereolithography object formation, it is believed that some of the techniques may have application in the LOM and/or SDM technologies where application of a beam or other laminae forming element must be precisely controlled.
Needs exist in the stereolithographic arts for improved beam generation techniques and positioning techniques. A first need exists for enhanced effective life of solid state ultraviolet producing lasers in a stereolithographic system. A second need exists for maintaining substantially uniform exposure over the length of each vector while simultaneously scanning as fast as possible, maintaining adequate positional control and minimizing the overall exposure time. A third need exists for improved control of the laser power that is produced and applied to the building material in a stereolithographic system. A fourth need exists for improved efficiency in exposing the building material in a stereolithographic system when exposure is controlled by a plurality of different vector types. A fifth need exists for simplified techniques for determining the maximum useful laser power for exposing a given set of vectors.
2. Other Related Patents and Applications
The patents, applications, and publications mentioned above and hereafter are all incorporated by reference herein as if set forth in full. Table 1 provides a listing of patents and applications co-owned by the assignee of the instant application. A brief description of subject matter found in each patent and application is included in the table to aid the reader in finding specific types of teachings. It is not intended that the incorporation of subject matter be limited to those topics specifically indicated, but instead the incorporation is to include all subject matter found in these applications and patents. The teachings in these incorporated references can be combined with the teachings of the instant application in many ways. For example, the references directed to various data manipulation techniques may be combined with the teachings herein to derive even more useful, modified object data that can be used to more accurately and/or efficiently form objects. As another example, the various apparatus configurations disclosed in these references may be used in conjunction with the novel features of the instant invention.
TABLE 1 ______________________________________ Related Patents and Applications Pat. No. Issue Date Application No. Filing Date Inventor Subject ______________________________________ 4,575,330 Hull Discloses fundamental elements of Mar 11, 1986 stereolithography. 06/638,905 Aug 8, 1984 4,999,143 Hull, et al. Discloses various removable support Mar 12, 1991 structures applicable to 07/182,801 stereolithography. Apr 18, 1988 5,058,988 Spence Discloses the application of beam Oct 22, 1991 profiling techniques useful 07/268,816 in stereolithography for determining Nov 8, 1988 cure depth and scanning velocity, etc. 5,059,021 Spence, et al. Discloses the utilization of drift Oct 22, 1991 correction techniques for eliminating 07/268,907 errors in beam positioning resulting Nov 8, 1988 from instabilities in the beam scanning system 5,076,974 Modrek, et al. Discloses techniques for post processing Dec 31, 1991 objects formed by stereolithography. 07/268,429 In particular exposure techniques are Nov 8, 1988 described that complete the solidifi- cation of the building material. Other post processing steps are also disclosed such as steps of filling in or sanding off surface discontinuities. 5,104,592 Hull Discloses various techniques for reduc- Apr 14, 1992 ing distortion, and particularly curl type 07/339,246 distortion, in objects being formed by Apr 17, 1989 stereolithography. 5,123,734 Spence, et al. Discloses techniques for calibrating a Jun 23, 1992 scanning system. In particular 07/268,837 techniques for mapping from rotational Nov 8, 1988 mirror coordinates to planar target surface coordinates are disclosed 5,133,987 Spence, et al. Discloses the use of a stationary mirror Jul 28, 1992 located on an optical path between the 07/427,885 scanning mirrors and the target surface Oct 27, 1989 to fold the optical path in a stereolithography system. 5,141,680 Almquist, et al. Discloses various techniques for Aug 25, 1992 selectively dispensing a material to 07/592,559 build up three-dimensional objects. Oct 4, 1990 5,143,663 Leyden, et al. Discloses a combined stereolithography Sep 1, 1992 system for building and cleaning 07/365,444 objects. Jun 12, 1989 5,174,931 Almquist, et al. Discloses various doctor blade Dec 29, 1992 configurations for use in forming 07/515,479 coatings of medium adjacent to Apr 27, 1990 previously solidified laminae. 5,182,056 Spence, et al. Discloses the use of multiple wave- Jan 26, 1993 lengths in the exposure of a 07/429,911 stereolithographic medium. Oct 27, 1989 5,182,715 Vorgitch, et al. Discloses various elements of a large Jan 26, 1993 stereolithographic system. 07/824,819 Jan 22, 1992 5,184,307 Hull, et al. Discloses a program called Slice and Feb 2, 1993 various techniques for converting 07/331,644 three-dimensional object data into data Mar 31, 1989 descriptive of cross-sections. Disclosed techniques include line width compensation techniques (erosion routines), and object sizing techniques. The application giving rise to this patent included a number of appendices that provide further details regarding stereolithography methods and systems. 5,192,469 Hull, et al. Discloses various techniques for Mar 9, 1993 forming three-dimensional object from 07/606,802 sheet material by selectively cutting Oct 30, 1990 out and adhering laminae. 5,209,878 Smalley, et al. Discloses various techniques for reduc- May 11, 1993 ing surface discontinuities between 07/605,979 successive cross-sections resulting Oct 30, 1990 from a layer-by-layer building technique. Disclosed techniques include use of fill layers and meniscus smoothing. 5,234,636 Hull, et al. Discloses techniques for reducing Aug 10, 1993 surface discontinuities by coating a 07/929,463 formed object with a material, heating Aug 13, 1992 the material to cause it to become flowable, and allowing surface tension to smooth the coating over the object surface. 5,238,639 Vinson, et al. Discloses a technique for minimizing Aug 24, 1993 curl distortion by balancing upward 07/939,549 curl to downward curl. Mar 31, 1992 5,256,340 Allison, et al. Discloses various build/exposure styles Oct 26, 1993 for forming objects including various 07/906,207 techniques for reducing object Jun 25, 1992 distortion. Disclosed techniques include: And (1) building hollow, partially hollow, 5,965,079 and solid objects, (2) achieving more Oct 12, 1999 uniform cure depth, (3) exposing layers 08/766,956 as a series of separated tiles or bullets, Dec 16, 1996 (4) using alternate sequencing exposure patterns from layer to layer, (5) using staggered or offset vectors from layer to layer, and (6) using one or more overlapping exposure patterns per layer. 5,321,622 Snead, et al. Discloses a computer program known as Jun 14, 1994 CSlice which is used to convert 07/606,191 three-dimensional object data into Oct 30, 1990 cross-sectional data. Disclosed techniques include the use of various Boolean operations in stereolithography. 5,597,520 Smalley, et al. Discloses various exposure techniques Jan 28, 1997 for enhancing object formation 08/233,027 accuracy. Disclosed techniques address Apr 25, 1994 formation of high resolution objects And from building materials that have a 5,999,184 Minimum Solidification Depth greater Dec 7, 1999 than one layer thickness and/or a 08/428,951 Minimum Recoating Depth greater than Apr 25, 1995 the desired object resolution. 08/722,335 Thayer, et al. Discloses build and support styles for Sep 27, 1996 use in a Multi-Jet Modeling selective Now deposition modeling system. abandoned 5,943,235 Earl, et al. Discloses data manipulation and system Aug 24, 1999 control techniques for use in a 08/722,326 Multi-Jet Modeling selective deposition Sep 27, 1996 modeling system. 5,902,537 Almquist, et al. Discloses various recoating techniques May 11, 1999 for use in stereolithography. Disclosed 08/790,005 techniques include 1) an inkjet Jan 28, 1997 dispensing device, 2) a fling recoater, 3) a vacuum applicator, 4) a stream recoater, 5) a counter rotating roller recoater, and 6) a technique for deriving sweep extents. 5,840,239 Partanen, et al. Discloses the application of solid-state Nov 24, 1998 lasers to stereolithography. Discloses 08/792,347 the use of a pulsed radiation source Jan 31, 1997 for solidifying layers of building material and in particular the ability to limit pulse firing locations to only selected target locations on a surface of the medium. 6,001,297 Partanen, et al. Discloses the stereolithographic Dec 14, 1999 formation of objects using a pulsed 08/847,855 radiation source where pulsing occurs Apr 28, 1997 at selected positions on the surface of a building material. 08/855,125 Nguyen, et al. Discloses techniques for interpolating May 13, 1997 originally supplied cross-sectional data descriptive of a three-dimensional object to produce modified data descriptive of the three-dimensional object including data descriptive of intermediate regions between the originally supplied cross-sections of data. 5,945,058 Manners, et al. Discloses techniques for identifying Aug 31, 1999 features of partially formed objects. 08/854,950 Identifiable features include trapped May 13, 1997 volumes, effective trapped volumes, and solid features of a specified size. The identified regions can be used in automatically specifying recoating parameters and or exposure parameters. 5,902,538 Kruger, et al. Discloses simplified techniques for May 11, 1999 making high-resolution objects utilizing 08/920,428 low-resolution materials that are limited Aug 29, 1997 by their inability to reliably form coatings of a desired thickness due to a Minimum Recoating Depth (MRD) limitation. Data manipulation techniques define layers as primary or secondary. Recoating techniques are described which can be used when the thickness between consecutive layers is less than a leading edge bulge phenomena. 09/061,796 Wu, et al. Discloses use of frequency converted Apr 16, 1998 solid state lasers in stereolithography. 09/154,967 Nguyen, et al. Discloses techniques for stereolitho- Sep 17, 1998 graphic recoating using a sweeping recoating device that pause and/or slows down over laminae that are being coated over. 09/484,984 Earl, et al. Entitled "Method and Apparatus for Jan 18, 2000 Forming Three-Dimensional Objects Using Line Width Compensation with Small Feature Retention." Discloses techniques for forming objects while compensating for solidification width induced in a building material by a beam of prescribed stimulation. 09/246,504 Guertin, et al. Entitled "Method and Apparatus for Feb 8, 1999 Stereolithographically Forming Three Dimensional Objects With Reduced Distortion." Discloses techniques for forming objects wherein a delay is made to occur between successive exposures of a selected region of a layer. 09/248,352 Manners, et al. Entitled Stereolithographic Method and Feb 8, 1999 Apparatus for Production of Three Dimensional Object Using Multiple Beams of Different Diameters" Discloses stereolithographic techniques for forming objects using multiple sized beams including data manipulation techniques for determining which portions of lamina may be formed with a larger beam and which should be formed using a smaller beam. 09/248,351 Nguyen, et al. Entitled "Stereolithographic Method Feb 8, 1999 and Apparatus for Production of Three Dimensional Objects Using Recoating Parameters for Groups of Layers." Discloses improved techniques for managing recoating parameters when forming objects using layer thicknesses smaller than a minimum recoating depth (MRD) and treating some non-consecu- tive layers as primary layers and treat- ing intermediate layers there between as secondary layers. 09/246,416 Bishop, et al. Entitled "Rapid Prototyping Apparatus Feb 8, 1999 with Enhanced Thermal and Vibrational Stability for Production of Three Dimensional Objects." Discloses an improved Stereolithographic apparatus structure for isolating vibration and/or extraneous heat producing components from other thermal and vibration sensitive components. 09/247,113 Chari, et al. Entitled "Stereolithographic Method and Feb 8, 1999 Apparatus for production of Three Dimensional Objects with Enhanced thermal Control of the Build environment. Discloses improved stereolithographic techniques for maintaining build chamber temperature at a desired level. The techniques include varying heat production based on the difference between a detected temperature and the desired temperature. 09/247,119 Kulkarni, et al. Entitled "Stereolithographic Method Feb 8, 1999 and Apparatus for Production of Three Dimensional Objects Including Simplified Build Preparation." Discloses techniques for forming objects using a simplified data preparation process. Selection of the various parameter styles needed to form an object is reduced to answering several questions from lists of possible choices. ______________________________________
The following two books are also incorporated by reference herein as if set forth in full: (1) Rapid Prototyping and Manufacturing: Fundamentals of Stereolithography, by Paul F. Jacobs; published by the Society of Manufacturing Engineers, Dearborn Mich.; 1992; and (2) Stereolithography and other RP&M Technologies: from Rapid Prototyping to Rapid Tooling; by Paul F. Jacobs; published by the Society of Manufacturing Engineers, Dearborn Mich.; 1996.