- 2014-12-01 (x)
- 2000-02-15 (x)
- Cawley, James D. (x)
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Show moreBackground of the invention: This invention generally relates to solid freeform fabrication (SFF) apparatus and methods, as well as products manufactured thereby. More particularly, the present invention relates to a method and apparatus for manufacturing an integral three dimensional object which is formed from individually contoured laminations of gradually varying shape. There has been much recent discussion concerning the feasibility of building a flexible system for automatically manufacturing three dimensional prototypes and products. Prototyping was originally conceived as a method for automated model making from computer-aided design descriptions of complex parts. Such prototyping is now included under the more general term "solid freeform fabrication (SFF)." SSF includes automatic fabrication of functional prototypes and actual production of small numbers of engineering components. Most of the current approaches, however, involve simultaneous materials processing and shape generation. This results in a compromise between geometrical accuracy and the structural behavior of the parts produced. It has been determined that a three dimensional object can be produced more accurately by utilizing thin plane cross-sections of a solid body as its building blocks with each of the cross-sections being cut or formed separately. Each cross-section can be cut by a laser located above a positioning or platter-like table. The several cross-sections are then attached to each other using suitable bonding techniques. This technology would appear to be available to any class of engineering materials available in sheet form and for which monolithic components are desired. Such materials include metals and alloys, engineering polymers and plastics, composites, ceramics and the like. Moreover, laminated composites of dissimilar materials (such as metals and ceramics, tough components with wear-resistant surfaces, etc.) could also be produced. This technology has been used with wax paper, thin metal ribbons and with a variety of thin thermoplastic sheets. However, this technology has not been widely used with ceramic tapes. Ceramics are a class of materials from which the formation of a three dimensional object from laminations appears to be particularly well suited. Ceramic materials offer a wide range of attractive engineering properties. For example, their thermal conductivity can be very low (e.g. vitreous SiO.sub.2) or very high (e.g., AlN). Some are excellent electrical insulators (e.g. Al.sub.2 O.sub.3) while others are semiconductors (e.g. SiC) or show metallic conductivity (e.g. TiB.sub.2). Structurally, many show good corrosion resistance. Increasingly, ceramics are being developed with high fracture toughness and strength (e.g. partially stabilized ZrO.sub.2 and Si.sub.2 N.sub.4). Advances in ceramic science achieved during the last decade, have yielded materials with markedly improved properties.
http://www.google.com/patents?vid=USPAT5779833
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Show moreBackground of the invention: The present invention pertains to the art of metallurgy and materials science, and more particularly to a process for producing powder metallurgy or ceramic or glass objects of simple or complex geometries. The invention is particularly applicable to a process for joining powder metallurgy objects in the green or brown state to form larger or more complex parts. The invention may be advantageously employed in other environments and applications. Although quite complex metallic shapes can be fabricated via a number of primary processes such as casting, forging, machining, and various powder-processing methods such as powder injection molding (PIM), all of these processes suffer some limitations in permissible part geometry. The limitations of the various forming methods, be they economic or technological, often dictate that a secondary joining operation is preferable or required. A number of different techniques are currently known and used to join dense monolithic parts. These include: welding, brazing, soldering, reaction bonding, adhesive joining, and use of mechanical fasteners. However, such methods generally create non-uniform structures. For example, in the case of a weld, even though its composition may be nominally the same as the base metal, the joint material and/or "heat affected zone" of the base metal has a microstructure and concomitant properties that differ from the base metal, often substantially. In the case of soldering, brazing, and adhesive joining, a foreign material is left in the joint. Mechanical fasteners require holes that can serve as stress concentrators, and often the design must be constrained to allow access during assembly. These techniques, developed for dense monolithic materials, are also used currently for powder processed components after they are densified. The three most prevalent methods for shaping parts are casting, deformation processing, and machining. In casting, the material is melted and poured into a mold. The liquid takes the shape of the mold cavity under some combination of gravity and pressure, and subsequent solidification results in the permanent storage of the shape information. In deformation processing, the material is typically heated to lower the effective yield stress and a shaped tool is brought to bear against the plastic mass under external pressure sufficient that permanent deformation occurs. The part typically retains its shape when the stress is removed. The familiar process of machining involves selective removal of material from the surface of a solid object by the action of a machine tool. In all of these processes, the metal is a dense solid monolith at the end of the shaping process. Powder processing, however, is different. In powder processing, shaping is often mediated through the presence of a carrier fluid, which can be a water-based solution, mixture of organic liquids, or molten polymers.
http://www.google.com/patents?vid=USPAT6033788
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Show moreBackground of the invention: This invention generally relates to material handling apparatus and methods. More particularly, the present invention relates to a transfer mechanism and a method for moving a laminate material from a first location to a second location. This application is related to U.S. patent application Ser. No. 08/511,604 filed on Aug. 4, 1995 by the same applicants as the application herein and assigned to the same assignee. The subject matter of the earlier filed patent application Ser. No. 511,604 is incorporated hereinto by reference in its entirety. Solid free form fabrication (SFF) includes automatic fabrication of functional prototypes and actual production of small numbers of engineering components. It has been determined that a three-dimensional object can be produced quite accurately by utilizing thin plane cross sections of a solid body as its building blocks with each of the cross sections being cut or formed separately. Each cross section can be cut by, for example, a laser located above a positioning or platter-like cutting table. The cut cross section is then picked up by a transfer mechanism and placed on a stack of other cross sections. Thereafter, the cross sections are attached to each other using suitable bonding techniques to arrive at a final three-dimensional product. Cutting desired regions from individual sheets offers prospective advantages over techniques which cut, deposit or fuse material directly on top of a subassembly. These techniques include stereo lithography, selective laser sintering, three-dimensional printing and laminated object manufacturing. By cutting laminae individually, the geometric formation process is fully decoupled from the material processing steps, thus obviating the compromises which are inherent in either operation. The instant process is perhaps most similar to the so-called "Helisys" process of laminated object manufacturing in which laminated objects are formed from stacks of laser cut sheet material. The primary difference between the Helisys system and the instant invention is that the Helisys system stacks sheets first, then cuts outlines in the stacks of sheets. In contrast, the instant invention cuts each sheet individually and then stacks the sheets. Due to this difference, the instant invention more readily accommodates internal voids in multiple materials. However, this is at the expense of a more demanding material handling technique. In particular, the instant material handling technique introduces the additional complexity of extracting desired cross sectional regions from a larger sheet of laminate material after the desired cross section is cut from a sheet and the transfer of the desired cross section laminate onto a stack of other cut laminates. The present invention contemplates a new and improved method and apparatus for material handling which overcomes the foregoing difficulties and others while providing better and more advantageous overall results.
http://www.google.com/patents?vid=USPAT5883357
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