Three dimensional printer

A lamination molding apparatus capable of supplying a material powder steadily to a recoater head, is provided. A lamination molding apparatus including a chamber covering a desired molding region and being filled with an inert gas having a desired concentration; a recoater head moving in the chamber to supply a material powder on the molding region to form a material powder layer; and a material supplying unit to supply the material powder to the recoater head; wherein the recoater head includes a material holding section to hold the material powder; and a material discharging opening to discharge the material powder in the material holding section.

FIELD

Embodiments of the present invention relate to a lamination molding apparatus.

BACKGROUND

In a lamination molding method of metal using laser beam, a molding table capable of vertical movement is arranged in a molding room filled with nitrogen gas. Then, a very thin material powder layer is formed on the molding table. Subsequently, predetermined portions of this material powder layer are irradiated with the laser beam to sinter the material powder at the position of irradiation. These procedures are repeated to form a desired molded product.

In Patent Literature 1, a constitution for supplying a material powder in a region between a pair of blades while moving the supplying opening of the powder supplying apparatus along the longitudinal direction of the pair of blades, is disclosed.

PATENT LITERATURE

SUMMARY

The constitution of Patent Literature 1 is superior in that material powder can be easily supplied uniformly or so as to conform with the width of the predetermined molding region in the longitudinal direction between the pair of blades. However, since the material powder is directly supplied onto the region between the pair of blades while moving the supplying opening along the longitudinal direction of the pair of blades, a flexible member such as a hose need be provided in between the supplying opening and the material retaining section fixed above the supplying opening in order to introduce the material powder onto the afore-mentioned region. Here, when the inner diameter of the flexible member is too large, the material powder would be filled in the flexible member, and thus the flexible member cannot be bent. Accordingly, the supplying opening cannot be moved smoothly. Therefore, the inner diameter of the flexible member and the inner diameter of the supplying opening need be made sufficiently small. When the inner diameters are as such, the amount of the material powder being supplied per unit time would be small, and thus the supplying opening need be moved slowly. This would also require the feed rate of the blade be slow. Accordingly, extra time is required to level the material powder. In addition, since the inner diameter of the flexible member is small, the material powder tends to get clogged in the flexible member or in the supplying opening, resulting in cases where the supply of the material is terminated. Further, since the material powder is sent to the supplying opening by free fall, the amount of the material powder being supplied would alter depending on the amount of remaining material powder in the material retaining section, and thus it is difficult to maintain the amount of the material powder being supplied constant. Therefore, the moving speed of the supplying opening need be adjusted in accordance with the amount of the material powder being supplied. However, in reality, it is difficult to control the movement of the supplying opening in such way. Accordingly, the supplying opening is moved in a condition where the amount of the material powder being supplied is not stable. This would result in uneven supply of the material powder within the region, and the material powder would not be supplied evenly with accuracy. Further, there may be a case where the material powder is spilled outside of the region.

The present invention has been made by taking these circumstances into consideration. An object of the present invention is to provide a lamination molding apparatus which can supply the material powder steadily to the recoater head.

According to the exemplary embodiments of the present invention, a lamination molding apparatus comprising: a chamber covering a desired molding region and being filled with an inert gas having a desired concentration; a recoater head moving in the chamber to supply a material powder on the molding region to form a material powder layer; and a material supplying unit to supply the material powder to the recoater head; wherein the recoater head comprises: a material holding section to hold the material powder; and a material discharging opening to discharge the material powder in the material holding section; the material supplying unit comprises: an intermediate duct to supply the material powder to the material holding section; and a main duct to supply the intermediate duct with the material powder; the intermediate duct is configured so as to be capable to discharge the material powder from an intermediate duct outlet capable of vertical movement and having an elongated shape; and the material supplying unit is controlled so as to discharge the material powder from the intermediate duct outlet in a condition where the intermediate duct is moved so that the intermediate duct outlet is located at a position lower than the upper end of the material holding section.

In the lamination molding apparatus of exemplary embodiments of the present invention, the material powder is discharged from the intermediate duct outlet having an elongated shape, thereby supplying the material powder to the recoater head. Accordingly, the intermediate duct need not be moved along the longitudinal direction of the recoater head, allowing simple constitution. In addition, the intermediate duct is capable of moving in vertical direction, and thus the material powder is discharged from the intermediate duct outlet in a condition where the intermediate duct outlet is positioned at a position lower than the upper end of the material holding section of the recoater head. Accordingly, the material powder would not overflow from the material holding section.

Hereinafter, various embodiments of the present invention will be provided. The embodiments provided below can be combined with each other.

Preferably, the material discharging opening has an elongated shape; and the intermediate duct outlet elongates in a direction substantially the same as the material discharging opening.

Preferably, the lamination molding apparatus further comprises: an intermediate duct shutter to open and shut the intermediate duct outlet; wherein: the intermediate duct shutter is controlled so that the intermediate duct outlet is opened in a condition where the intermediate duct outlet is located at a position lower than an upper end of the material holding section.

Preferably, the intermediate duct shutter is structured with at least two shutters capable of being controlled independently from each other.

Preferably, the intermediate duct comprises: a channel section elongating for a predetermined length from the intermediate duct outlet and having a constant cross-sectional area; and a widened section provided at an upper side of the channel section and having a wider cross-sectional area than the channel section.

Preferably, the main duct comprises: a main duct lower section and a main duct upper section provided above the main duct lower section; the material powder supplied to the main duct upper section is supplied to the intermediate duct via the main duct lower section; and a main duct shutter to open and shut a passage in between the main duct lower section and the main duct upper section is provided.

Preferably, the main duct lower section comprises an expanding section, length of the expanding section in a longitudinal direction of the intermediate duct becoming longer as the expanding section comes closer to the intermediate duct.

Preferably, the main duct is configured to be capable of moving vertically in accordance with a weight of the material powder maintained in the main duct.

DETAILED DESCRIPTION

Hereinafter, the embodiments of the present invention will be described with reference to the drawings. Here, the characteristic matters shown in the embodiments can be combined with each other.

As shown inFIG. 1, the lamination molding apparatus according to one embodiment of the present invention comprises a chamber1covering the desired molding region R and being filled with an inert gas having a desired concentration; a recoater head11moving in the chamber1and forming a material powder layer8by supplying the material powder on the molding region R; a laser beam emitter13which irradiates predetermined portions of the material powder layer8with a laser beam L to sinter the material powder at the position of irradiation; and a material supplying unit55to supply the material powder to the recoater head11.

Inside the chamber1, a powder layer forming apparatus3is provided. The powder layer forming apparatus3comprises a base stage4having the molding region R; a recoater head11provided on the base stage4and structured so as to be capable of moving in a horizontal uniaxial direction (direction shown by arrow B); and elongated members9r,9lprovided on both sides of the molding region R along the moving direction of the recoater head11. The molding region R is further provided with a molding table5capable of moving in a vertical direction (direction shown by arrow A inFIG. 1). Here, the molding table5is driven by a driving mechanism31. When the lamination molding apparatus is used, a molding plate7is placed on the molding table5, and the material powder layer8is formed on the molding table5.

The powder retaining wall26is provided so as to surround the molding table5, and the non-sintered material powder is retained in the powder retaining space surrounded by the powder retaining wall26and the molding table5. In the lower side of the powder retaining wall26, the powder discharging section27capable of discharging the material powder in the powder retaining space is provided. After completion of the lamination molding, the molding table5is descended so as to discharge the non-sintered material powder from the powder discharging section27. The material powder discharged is guided to the chute (not shown) by the chute guide28, and then the material powder is retained in the bucket (not shown) via the chute.

As shown inFIGS. 2 to 4, the recoater head11comprises a material holding section11a, an upper surface opening section11bprovided at the upper surface of the material holding section11a, and a material discharging opening11cprovided at the bottom surface of the material holding section11a, the material discharging opening11cdischarging the material powder in the material holding section11a. The material discharging opening11chas an elongated slit shape which elongates in the horizontal uniaxial direction (direction shown by arrow C) crossing orthogonally with the moving direction (direction shown by arrow B) of the recoater head11. On both sides of the recoater head11, squeegee blades11fband11rbfor forming a material powder layer8by planarizing the material powder discharged from the material discharging section11care provided. In addition, on both sides of the recoater head11, fume suction sections11fsand11rsfor suctioning the fume generated during sintering of the material powder are provided. The fume suction sections11fsand11rsare provided along the horizontal uniaxial direction (direction shown by arrow C) crossing orthogonally with the moving direction (direction shown by arrow B) of the recoater head11. The material powder is, for example, metal powder (iron powder for example) having a sphere shape with an average particle diameter of 20 μm.

The elongated members9rand9lare provided with openings along the moving direction (direction shown by arrow B) of the recoater head11. One of the openings is used as the inert gas supplying opening, and the other opening is used as the inert gas discharging opening. Accordingly, a flow of inert gas can be made in the direction shown by the arrow C on the molding region R. Therefore, the fume generated in the molding region R can be easily discharged along this flow of the inert gas. Here, in the present specification, “inert gas” is a gas which substantially does not react with the material powder, and nitrogen gas, argon gas, and helium gas can be mentioned for example.

A laser beam emitter13is provided above the chamber1. As shown inFIG. 2, the laser beam emitter13comprises a laser source42to emit the laser beam L, a pair of galvanometer scanners43aand43bto perform two dimensional scanning of the laser beam L emitted from the laser source42, and a condensing lens44to condense the laser beam L. The galvanometer scanner (X-axis scanner)43ascans the laser beam L in the direction shown by arrow B (X-axis direction), and the galvanometer scanner (Y-axis scanner)43bscans the laser beam L in the direction shown by arrow C (Y-axis direction). Each of the scanners43aand43bis controlled of its rotation angle depending on the magnitude of the rotation angle controlling signal. Accordingly, the position irradiated by the laser beam L can be moved to a desired position by altering the magnitude of the rotation angle controlling signal being input to the scanners43aand43b. An example of the condensing lens44is fθ lens.

The laser beam L which passed through the condensing lens44further passes through the window1aprovided to the chamber1. Then, the material powder layer8formed in the molding region R is irradiated with the laser beam L. The type of the laser beam L is not limited so long as it can sinter the material powder. For example, CO2laser, fiber laser, YAG laser and the like can be used. The window1ais formed with a material capable of transmitting the laser beam L. For example, in a case where the laser beam L is fiber laser or YAG laser, the window1acan be structured with a quartz glass.

On the upper surface of the chamber1, the fume adhesion preventing section17is provided so as to cover the window1a. The fume adhesion preventing section17is provided with a cylindrical housing17aand a cylindrical diffusing member17carranged in the housing17a. An inert gas supplying space17dis provided in between the housing17aand the diffusing member17c. Further, on the bottom surface of the housing17a, an opening17bis provided at the inner portion of the diffusing member17c. The diffusing member17cis provided with a plurality of pores17e, and the clean inert gas supplied into the inert gas supplying space17dis filled into a clean space17fthrough the pores17e. Then, the clean inert gas filled in the clean space17fis discharged towards below the fume adhesion preventing section17through the opening17b.

As shown inFIGS. 1 and 2, the material supplying unit55is provided at a position in the vicinity of the wall surfaces1e,1f,1g, and1h. The material supplying unit55comprises an intermediate duct69to supply the material powder to the material holding section11aof the recoater head11; and a main duct82to supply the material powder to the intermediate duct69. The material powder in the main duct82is supplied from the material tank76. The main duct82comprises a main duct lower section73, and a main duct upper section72provided above the main duct lower section73. Here, constitution is made so that the material powder supplied to the main duct upper section72is supplied to the intermediate duct69via the main duct lower section73.

As shown inFIG. 5, the intermediate duct69is structured so that the material powder is discharged from the intermediate duct outlet69awhich is capable of moving in a vertical direction and has an elongated shape (rectangular shape in the present embodiment). The intermediate duct outlet69aelongates in the direction substantially the same as the material discharging opening11cof the recoater head11. With such structure, the material powder being discharged from the intermediate duct outlet69acan be discharged substantially even in the elongation direction of the material discharging opening11c. Accordingly, it is advantageous since the intermediate duct69need not be moved in the longitudinal direction of the recoater head11.

The intermediate duct outlet69ais opened and shut by one or more intermediate duct shutter70. In the present embodiment, two intermediate duct shutters70aand70bwhich can be controlled independently from each other, are provided. As shown inFIG. 6, the intermediate shutters70aand70bare each driven by cylinders71aand71b, respectively. The intermediate duct shutters70aand70bare each provided with openings70a1and70b1at a bottom surface of the intermediate duct shutters70aand70b, respectively. Here, the intermediate duct shutters70aand70bare moved so that the position of the openings70a1and70b1match with the position of the intermediate duct outlet69a. Accordingly, the material powder can be discharged from the intermediate duct69. Here, inFIG. 7, the position of the opening70a1of the intermediate duct shutter70ais matched with the position of the intermediate duct outlet69a, and the position of the opening70b1of the intermediate duct shutter70bis not matched with the position of the intermediate duct outlet69a. Accordingly, the material powder is discharged only from the intermediate shutter70aside. As described, by providing a plurality of shutters which can be driven independently from each other, the powder material can be discharged from a partial region of the intermediate duct outlet69a. When the material powder is discharged in such way, the material powder layer8can be formed only on a partial region of the molding region R, allowing to reduce the amount of material powder used when the size of the molded product is relatively small. The intermediate duct outlet69ais usually shut by the intermediate shutter70, and is opened at a position lower than the upper end of the material holding section11awhen the material powder is supplied to the material holding section11aof the recoater head11, from the intermediate duct outlet69a. Here, when two or more of the intermediate shutters70are opened and shut independently from each other, it is preferable to provide a plurality of sensors to detect the amount of the material powder in the material holding section11ain accordance with the position of each of the intermediate duct shutters70, as described later.

As shown inFIGS. 5 to 7, the intermediate duct69comprises a channel section69belongating for a predetermined length from the intermediate duct outlet69aand having a constant cross-sectional area; and a widened section69cprovided at the upper side of the channel section69band having a wider cross-sectional area than the channel section69b. Here, the cross-sectional area is an area of a cross-section parallel with a horizontal plane. The material powder supplied from the main duct82passes through the widened section69cand is then supplied to the channel section69b. The channel section69bis provided in between a pair of wall surfaces arranged with a gap. Since the cross-sectional area of the channel section69bis small, the material powder can easily be filled, while the material powder is also easily clogged in the channel section69b. However, the vibration caused by the vertical movement of the intermediate duct69allows to solve the clogging of the material powder in the channel section69b.

A flange69dis provided at an upper end of the intermediate duct69. Here, one end of the bellows75is fixed with the flange69d, and the other end of the bellows75is fixed with the wall surface1e. When the intermediate duct69moves vertically, the bellows75expands and contracts so as to maintain connection between the intermediate duct69and the wall surface1e. As shown inFIGS. 2, 5, and 6, the intermediate duct69is capable of moving vertically by means of a driving mechanism77provided on a supporting table78fixed on the base stage4forming the molding region R. The driving mechanism77is structured with a coil spring77aand a cylinder77b, and the intermediate duct69moves vertically in accordance with the expansion and contraction of the cylinder77b.

As shown inFIGS. 8 to 9, a cover79is provided on the wall surface1e. Here, the main duct lower section73is inserted in the opening provided on the wall surface1eand the cover79. The outlet at the end of the main duct lower section73is arranged in the intermediate duct69, and thus the material powder from the main duct lower section73is supplied to the intermediate duct69. As shown inFIG. 10, the main duct lower section73is provided with an expanding section73a, of which length in the longitudinal direction of the intermediate duct69becomes longer as the expanding section73acomes closer to the intermediate duct69. Accordingly, the material powder is supplied to the intermediate duct69while expanding in the longitudinal direction of the intermediate duct69, and the material powder is also less likely to get clogged in the main duct lower section73. In addition, in the space69eabove the end of the main duct lower section73within the intermediate duct69, the material powder would not be filled, and tends to form an air entrapment. Therefore, the space69eis less likely to get clogged with the material powder.

In between the main duct lower section73and the main duct upper section72, a main duct shutter68to open and shut a passage68ain between the main duct lower section73and the main duct upper section72is provided. The main duct shutter68is supported by a shutter support71. The shutter support71is provided with a cylinder80to open and shut the main duct shutter68, and the main duct shutter68moves in accordance with the expansion and contraction of the cylinder80to open and shut the passage68a.

The shutter support71and the cover79are connected by bellows74. That is, one end of the bellows74is fixed to the shutter support71, and the other end of the bellows74is fixed to the cover79. The main duct82is supported by a coil spring81arranged on a supporting table83, and is structured so as to be capable of moving vertically in accordance with the weight of the material powder maintained in the main duct82. With such constitution, the main duct82is raised as the amount of material powder becomes less, and the timing for supplying the main duct82with the material powder can be detected easily. In addition, when the main duct82moves vertically, the bellows74expands and contracts so as to maintain the connection in between the shutter support71and the cover79.

The inside and outside of the chamber1is separated by the main duct shutter68, the shutter support71, the bellows74, the cover79, and the bellows75. The space surrounded by these members serves as the space inside the chamber1, and is maintained under inert gas atmosphere during the lamination molding. On the other hand, the space outside of the bellows74and the space above the main duct shutter68are maintained under external atmosphere. Regarding the main duct82, the inside of the main duct upper section72serves as the outer space, and the inside of the main duct lower section73serves as the inside the chamber1. These spaces are separated by the main duct shutter68. The passage68ais usually shut by the main duct shutter68, and is opened when the material powder is supplied from the main duct upper section72to the main duct lower section73. With such structure, the amount of outer air entering the chamber1when the material powder1is supplied to the recoater head11during lamination molding can be minimized.

Next, the inert gas supplying system to supply the inert gas to the chamber1and the fume discharging system to discharge the fume from the chamber1are explained.

The inert gas supplying system to supply the inert gas into the chamber1is connected with an inert gas supplying apparatus15and a fume collector19. The inert gas supplying apparatus15has a function to supply the inert gas, and is a gas cylinder of an inert gas for example. The fume collector19comprises duct boxes21and23provided at its upper stream side and its lower stream side, respectively. The gas (inert gas containing fume) discharged from the chamber1is sent to the fume collector19through the duct box21. Then, fume is removed in the fume collector19, and the cleaned inert gas is sent to the chamber1through the duct box23. According to such constitution, the inert gas can be recycled.

As shown inFIG. 1, the inert gas supplying system is connected with the upper supplying opening1bof the chamber1, the inert gas supplying space17dof the fume adhesion preventing section17, and the elongated member91. The inert gas is supplied into the molding space1dof the chamber1through the upper supplying opening1b. The inert gas supplied into the elongated member91is discharged onto the molding region R through the opening.

In the present embodiment, the inert gas from the fume collector19is sent to the upper supplying opening1b, and the inert gas from the inert gas supplying apparatus15is supplied to the inert gas supplying space17dand to the elongated member91. Although there is a possibility that the inert gas from the fume collector19contains residual fume, the constitution of the present embodiment does not permit the inert gas from the fume collector19be supplied into the space which requires especially high cleanliness (clean space17fand the space at the periphery of the molding region R). Accordingly, the effect of the residual fume can be minimized.

As shown inFIG. 1, the fume discharging system to discharge the fume from the chamber1is connected with the upper discharging opening1cof the chamber1, the fume suction sections11fsand11rsof the recoater head11, and the elongated member9r. Since the inert gas containing the fume in the molding space1dof the front chamber1fis discharged through the upper discharging opening1c, a flow of inert gas flowing from the upper supplying opening1btowards the upper discharging opening1cis formed in the molding space1d. The fume suction sections11fsand11rsof the recoater head11can suction the fume generated in the molding region R when the recoater head11passes over the molding region R. Here, the inert gas containing the fume is discharged out of the chamber1through the opening of the elongated member9r. The fume discharging system is connected with the fume collector19through the duct box21, and the inert gas after removal of the fume by the fume collector19is recycled.

Next, the lamination molding method using the afore-mentioned lamination molding apparatus will be explained.

Here, a case where the molded product47having the three-dimensional profile as shown inFIG. 11Ais formed by lamination molding is taken as an example for the explanation.

First, as shown inFIGS. 11B to 11C, a molded product47having the desired three-dimensional profile is molded using a computer, thereby obtaining a model48of the molded product. Then the model48of the molded product is sliced by a horizontal plane with a predetermined unit height, thereby forming sliced layers of49a,49b, . . .49f. Subsequently, as shown inFIGS. 11 to 14, the material powder layer8is irradiated with the laser beam L so as to selectively sinter the material powder, thereby forming the sintered layers of50a,50b, . . .50fhaving the profile corresponding to the sliced layers of49a,49b, . . .49frespectively. The sintered layers are also fused with each other, thereby forming the molded product47. The region surrounded by the outline profile of each of the sliced layers of49a,49b, . . .49fis the region to be irradiated with the laser beam L, f45a,45b, . . .45f(hereinafter referred to as irradiation region). The sliced layers, sintered layers, and irradiation region are also referred to as sliced layers49, sintered layers50, and irradiation region45, respectively.

As described, the molded product47can be formed by repeating selective sintering of the material powder of the material powder layer8in the irradiation region45. This is accomplished by irradiating the irradiation region45with the laser beam L. Here, the irradiation region45is surrounded by the outline profile of each of the sliced layers49of the model48of the molded product.

Next, the method for forming the sintered layers50will be explained in detail.

First, the height of the molding table5is adjusted to an adequate position while the molding plate7is mounted on the molding table5. In such condition, the recoater head11having the material holding section11afilled with the material powder is moved from the left side to the right side of the molding region R (in the direction shown by the arrow B inFIG. 1. Accordingly, the first layer of the material powder layer8is formed on the molding table5.

Subsequently, a prescribed portion of the material powder layer8is irradiated with the laser beam L, thereby sintering the portion of the material powder layer8irradiated with the laser beam. Accordingly, the first sintered layer50ais obtained as shown inFIG. 13.

Next, the height of the molding table5is descended by the thickness of one layer of the material powder layer8, followed by moving of the recoater head11from the right side to the left side of the molding region R. Accordingly, the second material powder layer8is formed so as to cover the sintered layer50a.

Subsequently, in a similar manner as described, the prescribed portion of the material powder layer8is irradiated with the laser beam L, thereby sintering the portion of the material powder layer8irradiated with the laser beam. Accordingly, the second sintered layer50bis obtained as shown inFIG. 14.

By repeating the afore-mentioned procedures, the third sintered layer50c, the fourth sintered layer50d, and the sintered layers thereafter are formed. The neighboring sintered layers are firmly fixed with each other.

After completion of the lamination molding, the non-sintered material powders are discharged via the powder discharging section27, to give the molded product.

A sensor to detect the amount of the material powder in the material holding section11ais provided to the recoater head11. As shown inFIGS. 15 to 16, when it is determined that the material powder need be supplied to the material holding section11a, the recoater head11is moved to directly beneath of the intermediate duct69, and the material powder is supplied.

Specifically, as shown inFIG. 15, the intermediate duct outlet69ais first located at a position higher than the upper end of the material holding section11a, and then the material holding section11ais moved to directly beneath of the intermediate duct outlet69ain a condition where the intermediate shutters70aand70bof the intermediate duct outlet69aare shut.

Subsequently, as shown inFIG. 16, the intermediate duct69is moved so that the position of the intermediate duct outlet69ais lower than the upper end of the material holding section11a. The intermediate duct shutters70aand70bare opened in such condition, allowing discharge of the material powder from the intermediate duct outlet69a. The material powder is discharged by its weight, and then the discharge of the material powder is terminated when the material powder in the material holding section11areaches the intermediate duct outlet69a. Therefore, the material powder would not flow out from the material holding section11a. Here, the material powder discharged from the intermediate duct outlet69acan be the one supplied in the intermediate duct69beforehand, or can be the one supplied into the intermediated duct69by opening the main duct shutter68in the condition as shown inFIG. 16.

After discharging the material powder from the intermediate duct outlet69a, the intermediate shutters70aand70bare shut, and then the intermediate duct69is raised to a position where the intermediate duct69does not interfere with the recoater head11. Accordingly, supply of the material powder is completed.

EXPLANATION OF SYMBOLS