Forming structures from CAD solid models

Details Forming structures from CAD solid models Forming structures from CAD solid models

2000-05-09

2002-05-21

Jenkins, Daniel J. (Department: 1742)

Powder metallurgy processes

Powder metallurgy processes with heating or sintering

Making composite or hollow article

C425S078000

Reexamination Certificate

active

06391251

ABSTRACT:

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
None.
FIELD OF THE INVENTION
The present invention relates to the field of direct material deposition processes which allow complex structures to be fabricated efficiently in small lots to meet stringent requirements of a rapidly changing manufacturing environment. More particularly, the invention petains to the fabrication of three-dimensional metal parts directly from a computer-aided design (CAD) electronic “solid” model. The invention also provides methods which use existing industry-standard computer file formats to create unique material structures including those having thermal characteristics embedded within them. The invention addresses methods to control direct material deposition processes to achieve a net-shaped or near net-shaped article, and to fabricate metal articles having exceptional material properties and dimensional repeatability.
BACKGROUND OF THE INVENTION
Manufacturing techniques or technologies generally known as “layered manufacturing” have emerged over the last decade. For metals, the usual shaping process forms a part by removing metal from a solid bar or ingot until the final shape is achieved. With the new technique, parts are made by building them up on a layer-by-layer basis. This is essentially the reverse of conventional machining. According to the paper appearing at the Internet site of Helsinki University of Technology, the first commercial process was presented in 1987. The process then was very inaccurate, and the choice of materials was limited. The parts were considered, therefore, prototypes and the process was called rapid prototyping technology (RPT). The prior art has advanced, however, to a point where it has been favorably compared too conventionally numerically controlled (NC) milling techniques. Considerable savings in time, and therefore cost, have been achieved over conventional machining methods. Moreover, there is a potential for making very complex parts of either solid, hollow or latticed construction.
Stereolithography technique (SLT), sometimes known as solid freeform fabrication (SFF), is one example of several techniques used to fabricate three-dimensional objects. This process is described in the Helsinki University of Technology paper. A support platform, capable of moving up and down is located at a distance below the surface of a liquid photo polymer. The distance is equal to the thickness of a first layer of a part to be fabricated. A laser is focused on the surface of the liquid and scanned over the surface following the contours of a slice taken through a model of the part. When exposed to the laser beam, the photo polymer solidifies or is cured. The platform is moved downwards the distance of another slice thickness and a subsequent layer is produced analogously. The steps are repeated until the layers, which bind to each other, form the desired object. A He—Cd laser may be used to cure the liquid polymer. The paper also describes a process of “selective laser sintering.” Instead of a liquid polymer, powders of different materials are spread over a platform by a roller. A laser sinters selected areas causing the particles to melt and solidify. In sintering, there are two phase transitions, unlike the liquid polymer technique in which the material undergoes but one phase transition: from solid to liquid and again to solid. Materials used in this process included plastics, wax metals and coated ceramics. A number of Patents and other disclosures have preceded and followed these processes, including the following:
U.S. Pat. No. 4,323,756, issued on Apr. 6, 1982 to Clyde O. Brown, et al., entitled Method for Fabricating Articles by Sequential Layer Deposition, discloses a method for the production of bulk rapidly solidified metallic objects of near-net shape, by depositing multiple thin layers of feedstock using an energy beam to fuse each layer onto a substrate. The feedstock may be in the form of metal powder or wire. A net shaped or near-net shaped article is one which approximates all of the desired features of its contemplated design so that little or no finishing work is required.
In his U.S. Pat. No.4,724,299, dated Feb. 9, 1988, Albert W. Hammeke describes a laser spray nozzle in which a beam passageway between the end portions permits a laser beam to pass through. A housing surrounds a second end portion and forms an annular passage, coaxial with the beam passageway. A cladding powder supply system is connected with the annular passage so that the powder exits the coaxial opening with the beam. The laser beam melts the powder which is deposited on a target substrate. The powder distribution system is contained within the nozzle assembly.
A laser spray nozzle assembly is a part of the Axial Flow Laser Plasma Spraying apparatus disclosed by Eric J. Whitney et al. in their August 1991 U.S. Pat. No. 5,043,548. The apparatus for depositing a feed material onto a substrate, has a plasma confinement chamber into which a laser beam is focused, the focal point being at a distance sufficiently far from the substrate that the substrate, is not melted. Finely divided feed material in a carrier gas flow is fed axially into the confinement chamber along the direction of the laser beam and melted into the plasma formed in the interaction of the laser beam, the feed material and the gas at the focal point. The feed material is then directed to deposit onto the substrate while the plasma energy is largely confined within the apparatus by the confinement chamber and constriction of the flow path upstream of the chamber.
A Rapid Prototyping System is disclosed by Joshua E. Rabinovich in U.S. Pat. No. 5,578,227, issued Nov. 26, 1996. The system involves a model making method and apparatus which projects a laser beam, circular polarizes the beam and directs the circular polarized beam for fusing a rectangular wire to a substrate or a previously fused wire on a target stage. The disclosure is differentiated by fusing the deposited feedstock to bond to a previously deposited layer without substantially altering the cross-section of the newly deposited material.
Such a deposition process would seem to have substantial problems of warping and distorting the deposited layers because of incomplete melting of feedstock material. Unlike Rabinovich's disclosed process, a powder deposition completely consumes the feedstock material in the three-dimensional net shape. The powder's cross-section and material properties are significantly altered. Rabinovitch does not disclose how the properties of the deposited material are controlled in his invention.
U.S. Pat. No. 5,697,046, dated Dec. 9, 1997 and entitled Composite Cermet Articles and Method of making was issued to Edward V. Conley. It discloses methods for making and using and articles comprising ferromagnetic cermets, preferably carbides and more preferably tungsten carbide having at least two regions exhibiting at least one property that differs. The cermets are manufactured by juxtaposing and densifying at least two powder blends having different properties. The methods described are very specific to cermets and do not employ solid models and automated processes.
U.S. Pat. No. 5,705,117 dated Jan. 6, 1998 discloses a Method of Combining Metal and Ceramic Inserts Into Stereolithography Components. Kurt Francis O'Connor et al. describe a stereolithography process for developing a prototype part in which inserts of non-photo polymer material are included in the resulting part so as to develop a functioning prototype part. In order to allow the inserts to be placed within the developing prototype part, a series of STL files are defined for forming the part in individual sections. The method is very specific to metal-ceramic composite structures for PC boards. It is not a direct fabrication method for three-dimensional objects with graded or multiple material structures.
Direct fabrication of three-dimensional metal parts by irradiating a thin layer of metal powder mixture is described in U.S. Pat. No. 5,393,613, entitled Composi

Affiliated with

Also associated with

Rating

Forming structures from CAD solid models does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Forming structures from CAD solid models, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Forming structures from CAD solid models will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2875900