Adhesive bonding and miscellaneous chemical manufacture – Methods – Contour or profile photography to reproduce...
Reexamination Certificate
2000-11-29
2002-10-29
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Contour or profile photography to reproduce...
C156S155000, C156S305000, C156S307300, C156S390000, C156S538000, C156S578000
Reexamination Certificate
active
06471800
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 fashion.
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 (die or mold). This process begins with creating a Computer Aided Design (CAD) file to represent the geometry or drawing of a desired object. As a common practice, this CAD file is converted to a stereo lithography (.STL) format in which the exterior and interior surfaces of the 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 image file is further sliced into a large number of thin layers with the contours of each layer being 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.
This SFF technology enables direct translation of the CAD image data into a three-dimensional (3-D) object. The technology has enjoyed a broad array of applications such as verifying CAD database, evaluating design feasibility, testing part functionality, assessing aesthetics, checking ergonomics of design, aiding in tool and fixture design, creating conceptual models and sales/marketing tools, 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 major 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 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 3-D, 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 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 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 section of a 3-D object are referred to as the “positive region”. A second solid layer 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 (part block) is removed from the platform, and the excess material (in the negative regions) 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 U.S. Pat. No. 4,752,352 (Jun. 21, 1988 to M. Feygin), U.S. Pat. No. 5,354,414 (Oct. 11, 1994 to M. Feygin) and U.S. Pat. No. 5,637,175 (Jun. 10, 1997 to M. Feygin, et al).
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. The SDM-based fabrication system contains a material deposition station and a plurality of processing stations (for mask making, heat treating, packaging, complementary material deposition, shot peening, cleaning, shaping, sand-blasting, and inspection). The combined deposition-shaping procedures qualify the SDM as a hybrid layer manufacturing technique. In the SDM system, each processing station performs a separate function such that when the functions are performed in series, a layer of an object is produced and is prepared for the deposition of the next layer. This system requires an article transfer apparatus, a robot arm, to repetitively move the object-supporting platform and any layers formed thereon out of the deposition station into one or more of the processing stations before returning to the deposition station for building the next layer. These additional operations in the processing stations tend to shift the relative position of the object with respect to the object platform. Further, the transfer apparatus may not precisely bring the object to its exact previous position. Hence, the subsequent layer may be deposited on an incorrect spot, thereby compromising part accuracy. The more processing stations that the growing object has to go through, the higher the chances are for the part accuracy to be lost. Such a complex and complicated process necessarily makes the over-all fabrication equipment bulky, heavy, expensive, and difficult to maintain. The equipment also requires attended operation.
Another good example of layer-additive techniques is the 3-D printing technique (3D-P) developed at MIT; e.g., U.S. Pat. No. 5,204,055 (April 1993 to Sachs, 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. The binder serves to bond together those powder particles on those areas defined by this pattern. Those powder particles in the un-wanted regions 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 the impregnation of the green part with a liquid material such as epoxy resin and metal melt. The loose powders tend to create a big mess inside the fabrication machine and adjacent areas. Such a machine may not be very suitable for use in an office environment.
This same drawback is true of the selected laser sintering or SLS technique (e.g., U.S. Pat. No. 4,863,538, Sep. 5, 1989 to C. Deckard) that involves spreading a full-la
Jang Bor Z.
Ma Erjian
Ball Michael W.
Haran John T.
Nanotek Instruments, Inc.
LandOfFree
Layer-additive method and apparatus for freeform fabrication... 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-additive method and apparatus for freeform fabrication..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Layer-additive method and apparatus for freeform fabrication... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2937023