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  Method and apparatus for manufacturing three-dimensional objectsUSPTO Application #: 20060165546Title: Method and apparatus for manufacturing three-dimensional objects Abstract: The present invention teaches a method and an apparatus for manufacturing a three-dimensional object having a smooth outer surface, without any step of removing a surface layer each time a sintered layer is formed so as to manufacture a three-dimensional object consisting of integrally built-up sintered layers. The method may include the steps of: (i) supplying powder particles (10) onto a moving area while heating the powder particles (10) with heat (20) from a high-density energy heat source so as to form a sintered layer (16); and (ii) supplying powder particles 10 onto a moving area on the sintered layer while heating the powder particles (10) with heat (20) from the high-density energy heat source so as to form another sintered layer (18) integrally on the sintered layer (16), wherein the step (ii) is repeated a predetermined number of times. (end of abstract) Agent: Dennison, Schultz, Dougherty & Macdonald - Alexandria, VA, US Inventors: Shigeki Yamada, Hiroyuki Hara USPTO Applicaton #: 20060165546 - Class: 419006000 (USPTO) Related Patent Categories: Powder Metallurgy Processes, Powder Metallurgy Processes With Heating Or Sintering, Making Composite Or Hollow Article, Powder Next To Powder The Patent Description & Claims data below is from USPTO Patent Application 20060165546. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] This application claims priority to Japanese patent application serial number 2005-15483, the contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Technical Field [0003] The present invention relates to a method and an apparatus for manufacturing three-dimensional objects consisting of integrally built-up sintered layers. [0004] 2. Description of the Related Art [0005] In order to manufacture three-dimensional objects consisting of integrally built-up sintered layers, Japanese Laid-Open Publication Nos. 2002-115004 and 2003-159755 disclose a rapid prototyping method including the steps of: forming a powder layer of inorganic or organic material on a sintering table; sintering a predetermined portion of the powder layer by irradiating with an optical beam to form a sintered layer; covering the sintered layer with a new powder layer; and repeating the aforementioned steps to form a plurality of sintered layers united together. [0006] According to the aforementioned rapid prototyping method, in which a powder layer is formed and then an optical beam is irradiated on a predetermined portion of the powder layer, unnecessary powder adheres to the sintered and hardened portions because of the heat transferred from the circumference thereof. In this case, the adhered powder forms a low-density surface layer so that the resulting three-dimensional object may not have a smooth and accurate outer surface. [0007] In this respect, Japanese Laid-Open Publication No. 2003-159755 discloses a method including a step of removing the low-density surface layer by a cutting tool or the like each time a predetermined portion of the powder layer is sintered by irradiating with an optical beam to form another sintered layer. However, according to this method, it will be necessary to remove the surface layer each time a sintered layer is formed. This requires additional processing time and costs for the removal step as compared to a method without such a removal step. SUMMARY OF THE INVENTION [0008] It is one object of the present invention to teach a method and an apparatus for manufacturing a three-dimensional object having a smooth outer surface, without any additional steps of removing a surface layer each time a sintered layer is formed so as to manufacture a three-dimensional object consisting of integrally built-up sintered layers. [0009] According to one aspect of the present teachings, a method for manufacturing a three-dimensional object consisting of a plurality of integrally built-up sintered layers is taught that may include the steps of: (i) supplying powder particles onto a moving area while heating the powder particles with heat irradiated from a high-density energy heat source so as to form a sintered layer;. and (ii) supplying powder particles onto a moving area on the sintered layer while heating the powder particles with heat irradiated from the high-density energy heat source so as to integrally form another sintered layer on the previous sintered layer, wherein the step (ii) is repeated a predetermined number of times. This method makes it possible to manufacture a three-dimensional object having a complex and precise shape in a short time and with reduced costs. The three-dimensional object manufactured by the method of the present invention is applicable, for example, to a mold for injection molding having a complex internal structure, or to a part or its prototype having a complex three-dimensional shape. [0010] The method may include further features: that the powder particles are operably supplied onto the moving area so that the surface region of the three-dimensional object has a higher density than the inside region thereof; that the powder particles for forming the inside region of the three-dimensional object have a larger particle diameter than the powder particles for forming the surface region thereof; that the powder particles for forming the inside region of the three-dimensional object are obtained by granulating the powder particles for forming the surface region thereof; that the powder particles for forming the inside region of the three-dimensional object are metal particles while the powder particles for forming the surface region thereof are metal particles mixed with an organic binder; that a supplying rate for the powder particles for forming the inside region of the three-dimensional object is greater than a supplying rate for the powder particles for forming the surface region thereof; that the high-density energy heat source is a laser; that a supplying rate of the powder particles is adjustable; and that the powder particles are selectable from a group of two or more different types of powder particles. [0011] The term "powder particles" herein refers to powder materials or particles that are sintered by heating. The term "sintering" refers to causing at least a portion of powder particles to be softened or melted by heating so as to integrally adhere to the surrounding powder particles on the softened or melted portion. "Sintering" may be either liquid phase sintering, which causes a portion of powder particles to be melted so as to integrally adhere to the surrounding powder particles, or solid phase sintering, which causes powder particles to integrally adhere by contacting each other without melting. Preferably, the powder particles used in the present invention may integrally adhere to each other through solid phase sintering, which enables a three-dimensional object to be formed having a smoother outer surface and a more accurate shape than through liquid phase sintering. Solid phase sintering also enables a three-dimensional object to be formed in a shorter time, because it requires less heating. [0012] The "powder particles" used in the present invention may include, but are not limited to, metal powder particles of steel or stainless steel such as SUS420 or SUS410L, and ceramic powder particles. It is also possible to use a mixture of the aforementioned powder particles. [0013] A process for preparing such powder particles may include, but is not limited to, an atomization process and a mechanical process such as crushing, grinding, and milling. Preferably, powder particles used in the present invention may be prepared to be spherical and as uniform as possible with respect to particle diameter distribution. For example, powder particles pulverized into fine spherical particles through an atomization process are preferable in the present invention. The average particle diameter may include, but is not limited to, the range generally between 1 .mu.m and 100 .mu.m, and preferably between 10 .mu.m and 50 .mu.m. It should be noted that the "average particle diameter" refers to a representative particle diameter corresponding to a cumulative oversize weight percentage of 50% estimated from a cumulative oversize weight percentage versus particle diameter curve. [0014] The "high-density energy heat source" used in the present invention refers to a heat source for locally heating a supplied powder area. For example, a plasma-transferred arc, a non-transferred plasma arc, a laser, or a mixture of these high-density energy heat sources may be used as the high-density energy heat source. In particular, the laser may include a carbon dioxide laser and a YAG laser. Such a heat source may be appropriately selected according to factors such as the type, the volume, and the particle diameters of the powder particles, and the accuracy requirements for forming the surface of the three-dimensional object. Using such a local heating heat source enables the target powder particles supplied onto a predetermined area to be intensively heated and sintered. Also, it is possible to prevent various defects such as lower forming accuracy and deposition of the powder particles onto the surface portions, otherwise caused by heat transferred to areas other than the desired sintering area. [0015] In particular, the high-density energy heat source may heat powder particles supplied on a predetermined area either concurrently with or immediately subsequent to the supply of the powder particles. Thus, it is possible to intensively heat the target powder particles supplied onto a predetermined area, which results in preventing the heat from transferring to a portion surrounding the target portion to be sintered and hardened. Further, since there exist no extra powder particles surrounding the target portion to be sintered and hardened, it is possible to prevent unnecessary powder particle depositions, which are caused by transferred heat, onto the three-dimensional object to be obtained. As a result, without removing the low-density surface layer by a cutting tool or the like each time a sintered layer is formed, it is possible to manufacture a three-dimensional object having a smooth and accurate outer surface. [0016] According to another aspect of the present invention, an apparatus is taught for manufacturing a three-dimensional object consisting of a plurality of integrally built-up sintered layers that may include: a powder particle supplying device for supplying powder particles at a adjustable supplying rate; a high-density energy heat source for heating the powder particles supplied by the powder particle supplying device; and a driving device for moving an area onto which the powder particles are supplied by the powder particle supplying device. BRIEF DESCRIPTION OF THE DRAWINGS [0017] Additional objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the claims and the accompanying drawings, in which: [0018] FIG. 1 is a schematic view showing one representative embodiment of a sintered layer forming process; [0019] FIG. 2 is a perspective view of a three-dimensional object formed on a work table according to the present invention; and [0020] FIG. 3 is a cross-sectional view of the three-dimensional object taken along the line III-III shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION Continue reading... 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