Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-01-17
2002-04-23
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C156S273100, C425S17480E
Reexamination Certificate
active
06376148
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to a computer-controlled method and apparatus for fabricating a three-dimensional (3-D) object and, in particular, to an improved method and apparatus for building a 3-D object directly from a computer-aided design of the object in a layer-by-layer, but not point-by-point fashion. The presently invented method is referred to as a Full-Area Sintering Technique (FAST).
BACKGROUND OF THE INVENTION
Solid freeform fabrication (SFF) or layer manufacturing (LM) is a new fabrication technology that builds an object of any complex shape layer by layer or point by point without using a pre-shaped tool such as a die or mold. This process begins with creating a Computer Aided Design (CAD) file to represent the geometry or drawing of a desired object. This CAD file is converted to a proper solid interface format such as the stereo lithography (.STL) format.
In .STL, the exterior and interior surfaces of an object is approximated by a large number of triangular facets that are connected in a vertex-to-vertex manner. A triangular facet is represented by three vertex points each having three coordinate points: (x
1
,y
1
,z
1
), (x
2
,y
2
,z
2
), and (x
3
,y
3
,z
3
). A perpendicular unit vector (i,j,k) is also attached to each triangular facet to represent its normal for helping to differentiate between an exterior and an interior surface. This object geometry file is further sliced into a large number of thin cross-sectional layers with each layer being comprised of coordinate point data. In a commonly used layer-wise data format called Common Layer Interface (CLI), the contours (shape and dimensions) of each layer are defined by a plurality of line segments connected to form polylines on an X-Y plane of a X-Y-Z orthogonal coordinate system. The layer data are converted to tool path data normally in terms of computer numerical control (CNC) codes such as G-codes and M-codes. These codes are then utilized to drive a fabrication tool for defining the desired areas of individual layers and stacking up the object layer by layer along the Z-direction.
The SFF technology enables direct translation of the CAD image data into a three-dimensional (3-D) physical object. The technology has enjoyed a broad array of applications such as verifying CAD database, evaluating engineering design feasibility, testing part functionality, assessing aesthetics, checking ergonomics of design, aiding in tool and fixture design, creating conceptual models and marketing tools, producing medical or dental models, generating patterns for investment casting, reducing or eliminating engineering changes in production, and providing small production runs.
The SFF techniques may be divided into three categories: layer-additive, layer-subtractive, and hybrid (combined layer-additive and subtractive). A layer additive process involves adding or depositing a material to form predetermined areas of a layer essentially point by point; but a multiplicity of points may be deposited at the same time in some techniques, such as of the multiple-nozzle inkjet-printing type. These predetermined areas together constitute a thin cross-section of a 3-D object as defined by a CAD geometry. Successive layers are then deposited in a predetermined sequence with a layer being affixed to its adjacent layers for forming an integral multi-layer object. A 3-D object, when sliced into a plurality of constituent layers or thin sections, may contain features that are not self-supporting and in need of a support structure during the object-building procedure. These features include isolated islands in a layer and overhangs. In these situations, additional steps of building the support structure, also on a layer-by-layer basis, will be required of a layer-additive technique. An example of a layer-additive technique that normally requires building a support structure is the fused deposition modeling (FDM) process as specified in U.S. Pat. No. 5,121,329; issued on Jun. 9, 1992 to S. S. Crump.
A layer-subtractive process involves feeding a complete solid layer of a material to the surface of a support platform and using a cutting tool (normally a laser) to cut off or somehow degrade the integrity of the un-wanted areas of this solid layer. The solid material in these un-wanted areas of a layer becomes a part of the support structure for subsequent layers. These un-wanted areas are hereinafter referred to as the “negative region” while the remaining areas that constitute a cross-section of a 3-D object are referred to as the “positive region”. A second solid layer of material is then fed onto the first layer and bonded thereto. The same cutting tool is then used to cut off or degrade the material in the negative region of this second layer. These procedures are repeated successively until multiple layers are laminated to form a unitary object. After all layers have been completed, the unitary body (or part block) is removed from the platform, and the excess material (in the negative region) is removed to reveal the 3-D object. This “decubing” procedure is known to be tedious and difficult to accomplish without damaging the object. An example of a layer-subtractive technique is the well-known laminated object manufacturing (LOM), disclosed in, for instance, U.S. Pat. No. 4,752,352 (Jun. 21, 1988 to M. Feygin).
A hybrid process involves both layer-additive and subtractive procedures. An example can be found with the Shape Deposition Manufacturing (SDM) process disclosed in U.S. Pat. No. 5,301,863 issued on Apr. 12, 1994 to Prinz and Weiss. Such a process is complicated and difficult to operate. It also requires the operation of heavy and expensive equipment.
Another good example of the layer-additive technique is the 3-D powder printing technique (3D-P) developed at MIT; e.g., U.S. Pat. No. 5,204,055 (April 1993 to Sachs, et al.), U.S. Pat. No. 5,340,656 (Aug. 23, 1994 to Sachs, et al.), U.S. Pat. 5,387,380 (Feb. 7, 1995 to Cima, et al.), and U.S. Pat. No. 6,007,318 (Dec. 28, 1999 to Russell, et al.). This 3-D powder printing technique involves dispensing a layer of loose powders onto a support platform and using an ink jet to spray a computer-defined pattern of liquid binder onto a layer of uniform-composition powder in a point-by-point fashion. The binder serves to bond together the powder particles on those areas (positive region) defined by this pattern. Those powder particles in the un-wanted areas (negative region) remain loose or separated from one another and are removed at the end of the build process. Another layer of powder is spread over the preceding one, and the process is repeated. The “green” part made up of those bonded powder particles is separated from the loose powders when the process is completed. This procedure is followed by binder removal and impregnation of the green part with a liquid material such as epoxy resin and metal melt. Although several nozzle orifices may be employed to dispense several droplet streams at the same time, this 3D-P process remains to be essentially a point-by-point process, being characterized by a slow build speed.
This same drawback is true of the traditional selected laser sintering (SLS) technique (e.g., U.S. Pat. No. 4,863,538, Sept. 5, 1989 to C. Deckard; U.S. Pat. No. 4,938,816, Jul. 3, 1990 to J. Beaman, et al.; U.S. Pat. No. 4,944,817, Jul. 31, 1990 to D. Bourell, et al.; U.S. Pat. No. 5,155,324, Oct. 13, 1992 to C. Deckard, et al.; U.S. Pat. No. 5,156,697, Oct. 20, 1992 to D. Bourell; U.S. Pat. 5,316,580, May 31, 1994 to C. Deckard; U.S. Pat. No. 5,352,405, Oct. 4, 1994 to J. Beaman, et al.; U.S. Pat. No. 5,393,613, Feb. 28, 1995 to C. MacKay; U.S. Pat. No. 5,314,003, May 24, 1994 to MacKay; U.S. Pat. No. 5,431,967, Jul. 11, 1995 to A. Manthiram, et al; U.S. Pat. No. 5,732,323, Mar. 24, 1998, to O. Nyrhilä). The traditional SLS technique involves spreading a full-layer of loose powder particles and uses a computer-controlled, high-power laser to partially melt these particles within predetermined areas (positive region) in a point-by-point fa
Jang Bor Zeng
Liu Jun Hai
Goodrow John
Nanotek Instruments, Inc.
LandOfFree
Layer manufacturing using electrostatic imaging and lamination does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Layer manufacturing using electrostatic imaging and lamination, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Layer manufacturing using electrostatic imaging and lamination will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2845557