Plastic and nonmetallic article shaping or treating: processes – Direct application of electrical or wave energy to work – Using laser sintering of particulate material to build...
Reexamination Certificate
1999-08-13
2001-05-29
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Direct application of electrical or wave energy to work
Using laser sintering of particulate material to build...
C419S010000, C419S031000, C419S062000
Reexamination Certificate
active
06238614
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rapid prototyping method using selective infiltration manufacturing process. More particularly, the present invention relates to a rapid prototyping method, which infiltrates molten material between preheated powder particles and manufactures prototypes and molds.
2. Description of the Conventional Art
Conventional rapid prototyping methods fall into two big categories. One method is the curing method, in which liquid state material is scanned by laser beam. The other method is to put solid powder materials or sheet materials together for desired shapes.
One of curing methods is stereolithography (3D systems Co.), in which liquid state photo-polymer is selectively scanned by laser beam and solidified layers are accumulated. Two implementations of the stereolithography are available. One implementation is to scan the laser beam locally (3D systems Co., Quadrax Co., and Sony Co.) and the other is to scan the whole layer using ultra-violet light lamps (Cubital company and Light Scuipting Co.).
However, solidified photo-polymers are shrunk and therefore distortions are caused. In addition, if products have overhangs, the supports are required in order to keep photo-polymers from falling down. Because polymers are used as materials, the degree of strength of final products is decreased and therefore utility of the products is restricted.
Selective Laser Sintering method (DTM Co.) and three dimension printing methods (MIT, Soligen Co., ProMetal Co. and Z Corp.) employ powder materials. The Selective laser sintering method spreads plastic powder materials and then scans laser beam to combine the powders. The Selective laser sintering method is used to manufacture metal products and molds with the help of metal powder coated on plastics. However, for manufacturing metal products and molds, plastics already coated on the metal powders must be removed and then sintering process is required to combine metal powders. Also, a process like copper infiltration must be done at the end of the whole process to fill the gaps between metal powders. This process usually causes heat deformation of final products and therefore accuracy gets severely deteriorated.
In three dimension printing method, liquid state binders are applied to the surface of the spread powder. Using the three dimension printing method, ceramic shells for investment casting can be directly manufactured. Powders whose basic component is starch can be used in the method. However, post-processing is necessary to increase the density and intensity of final products and therefore shrinkage of the final products due to heat deformation is caused.
In Laminated Object Manufacturing method (Helisys Co.), heated rollers glue thin sheet-type papers and lasers cut them. This process is repeated. This laminated object manufacturing method has advantages in that papers are used as a main material and therefore overall costs are relatively low. But it takes long time to decube the desired part from the paper box. Let's suppose that a product with spherical shape needs to be manufactured by the laminated object manufacturing method. In the middle of the process, papers are to be cut and accumulated. Finally, it is going to take long time to pull out the final product because of remaining of papers, which surround the final product of spherical shape. Now, thanks to recently developed plastic thin material, there are ways to manufacture products of plastics by the laminated object manufacturing method. However, it has same drawbacks as the case of products of papers.
In Fused Deposition Modeling method (Stratasys Co.), filament shape plastic materials are passed through nozzles, which have similar shape of extrusion molds. However, the surface of the final product manufactured by this method is rough because filament shape materials are used.
In recently commercialized Laser Engineered Net Shaping (Sandia National Lab., Optomec Co.) method, metal substrate is locally heated and small melt pool is made. Then, metal powders are dropped into the small melt pool. While the final product is being solidified at the final stage, shape distortion may occur because metal material is completely melted in the process. Also, products with overhangs and cantilevers cannot be manufactured by the LENS method by the same reason.
In Shape Deposition Manufacturing (Stanford University and Carnegie Mellon University) method, metal deposition and CNC machine processing are employed. After metal material is deposited, it is processed to have desired thickness and boundary shape by multi-axis CNC milling machine. Then, the remaining portion of the same layer is filled with other metal materials and CNC milling process is applied again to deposit another layer. After the processes of one layer are finished, shot peening operation is performed to eliminate residual stress. The main drawback of the SDM method is that it takes relatively long time to manufacture products.
REFERENCES
1. European Patent Documents
EP-431924 A, Jun. 24, 1991, Three Dimensional Printing process to fabricate moulds and prototypes involving selectivity applying binder to successively deposited powder layers
2. U.S. Patent Documents
U.S. Pat. No. 4,938,816, Jul. 3, 1990, Selective laser sintering with assisted powder handling
2. Other Publications
Proceeding of Solid Freeform Fabrication Symposium, pp125~132, M. L. Griffith et al., “Free Form Fabrication of Metallic Components Using Laser Engineered Net Shaping Lens”.
Proceeding of Solid Freeform Fabrication Symposium, pp117~124, J. R. Fessler et al., “Laser Deposition of Metals for Shape Deposition Manufacturing”.
SUMMARY OF THE INVENTION
A rapid prototyping method in accordance with the present invention comprises the following steps. First step is to spread out powders on the surface of platform uniformly and the powders are the main material of desired products. Second step is to preheat the powders by laser beam within the melting point of the powders. Third step is to infiltrate super-heated materials selectively. The super-heated materials are dissolved and filled the space among the powders. The three steps above are repeated until the desired products are manufactured.
A rapid prototyping apparatus in accordance with the present invention comprises powder material spreading means, dispensing infiltration material means, laser beam scanning means, and control means. The powder material spreading means spread out powders on the surface of platform uniformly while moving along the X axis. The powders are the main material of desired products. The dispensing infiltration material means dispenses infiltration materials while moving along three axes and the infiltration materials are infiltrated between the powders selectively. The laser beam scanning means preheat the powders by laser beam within the melting point of the powders and melt the infiltration material by laser beam. The control means control the powder material spreading means, the dispensing infiltration material means, and the laser beam scanning means on the basis of modeling data of the desired products.
A rapid prototyping apparatus in accordance with the present invention comprises powder material spreading means, dispensing infiltration material means, laser beam scanning means, and control means. The powder material spreading means spread out powders on the surface of platform uniformly while moving along the X axis. The powders are the main material of desired products. The dispensing infiltration material means dispense infiltration materials while moving along three axes and the infiltration materials are infiltrated between the powders selectively. The laser beam scanning means preheat the powders by laser beam within the melting point of the powders. The control means control the powder material spreading mean, the dispensing infiltration material means, and the laser beam scanning means on the basis of modeling data of the desired products.
REFERENCES:
patent: 4938816
Sohn Hyon Kee
Yang Dong Yol
Graybeal Jackson Haley LLP
Korea Advanced Institute Science and Technology
Tentoni Leo B.
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