Build region limitation unit and additive manufacturing apparatus having the same

A build region limitation unit for an additive manufacturing apparatus includes a movable unit fixed to a build table and a non-movable unit placed on a base frame. The movable unit includes a first anti-scattering frame provided to protrude upward. The non-movable unit includes a flat plate that covers a first build region with a portion other than an opening and forms a second build region, and a second anti-scattering frame that is provided to protrude downward at an outer periphery of the opening. The first anti-scattering frame surrounds the second anti-scattering frame with a gap therebetween.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefits of Japanese application No. 2022-073304, filed on Apr. 27, 2022. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The disclosure relates to a build region limitation unit and an additive manufacturing apparatus having the same.

Description of Related Art

An additive manufacturing apparatus that performs powder bed fusion forms a material layer by spreading material powder in a build region which is a region where a desired three-dimensional object can be formed. The additive manufacturing apparatus irradiates the material layer with a laser beam or an electron beam to sinter or melt the material powder and form a solidified layer. The additive manufacturing apparatus repeats formation of a material powder layer and formation of a solidified layer to manufacture a desired three-dimensional object.

There are many types of material powders for use in additive manufacturing. A single additive manufacturing apparatus may use multiple types of materials, and when different materials are used, work related to material replacement is performed. In replacing the material, it is necessary to clean the additive manufacturing apparatus and remove the existing material inside.

The additive manufacturing apparatus disclosed in U.S. Pat. No. 10,569,331 is configured to recover excess material generated during manufacturing, remove impurities, and then supply the material to the additive manufacturing apparatus main body again. A device for recovering and re-supplying the excess material is hereinafter referred to as a material reuse unit. When replacing the material, it is necessary to clean not only the additive manufacturing apparatus main body but also the material reuse unit.

The additive manufacturing apparatus disclosed in U.S. Patent Publication No. US 2022/0118524 is configured such that the material reuse unit can be separated from the additive manufacturing apparatus main body. By preparing a material reuse unit for each material powder, it is unnecessary to clean the material reuse unit in replacing the material, which reduces the time and effort for material replacement.

SUMMARY

Problems to be Solved

Small three-dimensional objects are sometimes manufactured experimentally using material powder that is different from usual. For example, when considering use of new material powder, a test piece may be manufactured using the material powder to measure the physical properties of the test piece and collect the irradiation conditions of the laser beam or electron beam.

The conventional additive manufacturing apparatus is designed corresponding to the maximum manufacturing size, so a relatively large amount of material powder is used. For example, in forming the material layer, the material powder is spread over a range that is actually required. Therefore, it is necessary to prepare a certain amount of material powder even when manufacturing a small three-dimensional object.

In addition, as described above, cleaning is required in replacing the material. As disclosed in U.S. Pat. No. 10,569,331, it is known to prepare a material reuse unit for each material in order to reduce the time and effort for material replacement. However, preparing a dedicated material reuse unit for the material powder used for experiment increases costs.

In view of such circumstances, the disclosure provides a build region limitation unit suitable for additive manufacturing a small three-dimensional object such as a test piece simply using a small amount of material powder, and an additive manufacturing apparatus having the same.

Means for Solving the Problems

According to an embodiment of the disclosure, a build region limitation unit is provided for an additive manufacturing apparatus including a base frame which has a first build region that is a region capable of forming a three-dimensional object, and a build table which is provided in the first build region and configured to be movable in a vertical direction and in which a base plate is arranged, and the additive manufacturing apparatus alternately repeats formation of a material layer composed of material powder and formation of a solidified layer. The build region limitation unit includes: a movable unit fixed to the build table; and a non-movable unit placed on the base frame. The movable unit includes: a first anti-scattering frame that is a hollow frame provided to protrude upward. The non-movable unit includes: a flat plate which is a plate having an opening and placed on the base frame, covers the first build region with a portion other than the opening, and forms a second build region smaller than the first build region; and a second anti-scattering frame which is a hollow frame provided to protrude downward at an outer periphery of the opening. The first anti-scattering frame surrounds the second anti-scattering frame with a gap therebetween.

Effects

The build region limitation unit according to the disclosure makes it easy to manufacture a small three-dimensional object using material powder different from usual. The build region limitation unit also reduces the burden related to cleaning work at the time of material replacement.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the disclosure will be described hereinafter with reference to the drawings. Various features shown in the embodiments shown hereinafter may be combined with each other.FIG.1toFIG.15illustrate an additive manufacturing apparatus or parts thereof when additive manufacturing is performed using a build region limitation unit8.FIG.16toFIG.18illustrate an additive manufacturing apparatus or parts thereof when additive manufacturing is performed without using the build region limitation unit8.

The additive manufacturing apparatus100according to this embodiment repeats formation of a material layer6composed of material powder M and formation of a solidified layer to manufacture a desired three-dimensional object K. As shown inFIG.1,FIG.2, andFIG.16, the additive manufacturing apparatus100includes a chamber1, an irradiator13, an inert gas supply device15, a fume collector19, a build table drive mechanism52, a first build region recoater head31, a base frame4, a material recovery unit40, a build table5, a recoater head drive mechanism51, a material supply unit60, and the build region limitation unit8. Some components may be removed or not used, as described later. The base frame4has a first build region R and a second build region Rs, which are regions for forming the three-dimensional object K. The first build region R contains the second build region Rs. That is, the second build region Rs is a portion in the first build region R and exists within the first build region R. The material recovery unit40and the material supply unit60constitute a material reuse unit in this embodiment.

FIG.16shows a mode of the additive manufacturing apparatus100when additive manufacturing is performed using the first build region R. Typically, the first build region R is used when additive manufacturing a product sequentially. At this time, the material reuse unit, that is, the material recovery unit40and the material supply unit60, and the first build region recoater head31are used. Specifically, first, the first build region recoater head31is moved in the first horizontal direction (the direction of the arrow B) by the recoater head drive mechanism51, and a material layer6is formed on a base plate33placed on the build table5. Then, the irradiator13irradiates the material layer6with a laser beam L to form a solidified layer. The build table5is lowered by one layer, a material layer6is formed on the solidified layer in the same procedure, and the material layer6is irradiated with the laser beam L to form a solidified layer. In this way, the formation of the material layer6and the formation of the solidified layer are alternately repeated to manufacture the three-dimensional object K.

An excess material, which is unsolidified material powder M, is generated during the additive manufacturing. Spatters scattered during the formation of the solidified layer may be mixed with the excess material as impurities. When the solidified layer is cut, cutting chips may also be mixed as impurities. The excess material is extruded by the moving first build region recoater head31and discharged from a material recovery port27bwhich is an opening formed in the base frame4. Further, a material recovery port27awhich is an opening is formed in the lower portion of material holding walls26surrounding the build table5. After manufacturing the three-dimensional object K, the excess material is discharged from the material recovery port27aby lowering the build table5. Alternatively, after the build table5is raised, the excess material may be dropped into the material recovery port27bwith a brush or the like. The excess material may be discharged by other means such as a suction nozzle. The discharged excess material is guided to a chute29and contained in a bucket30. The impurities are then removed by the material recovery unit40, and the remaining material is sent to the material supply unit60. The material supply unit60supplies unused material powder M or material powder M with impurities removed by the material recovery unit40to a material case311of the first build region recoater head31. The above processes are repeated so as to additive manufacture the three-dimensional object K continuously.

FIG.1andFIG.2show a mode of the additive manufacturing apparatus100when additive manufacturing is performed using only the second build region Rs. Typically, the second build region Rs is used when a small three-dimensional object K such as a test piece is additive manufactured experimentally using material powder M different from usual. At this time, while the build region limitation unit8is used, the material powder M is not supplied from the material supply unit60and excess material is not recovered from the material recovery ports27aand27b. As the recovery system and the supply system for the material powder M, including the material recovery unit40and the material supply unit60which are the material reuse unit, are not used, different types of materials, typically, the material powder M for mass production and the material powder M for experiment are prevented from being mixed. Thus, the work load such as cleaning when switching between the two material powders M is reduced. If the material reuse unit is configured to be separable from the chamber1, the material reuse unit may be removed when the build region limitation unit8is used.

The chamber1covers the first build region R and the second build region Rs which are regions in which the three-dimensional object K is formed. The chamber1includes a plurality of side plates and an upper plate, and one of the side plates is provided with a door that can be opened and closed. The door may be provided with a glove box. The chamber1is filled with inert gas of a predetermined concentration. In this specification, the inert gas is gas that does not substantially react with the material powder M, such as nitrogen gas, argon gas, and helium gas. The material powder M is, for example, powder of metal.

The irradiator13is provided above the chamber1. The irradiator13irradiates a predetermined portion of the material layer6formed on the first build region R or the second build region Rs with the laser beam L to melt or sinter the material powder M at the irradiated position and form a solidified layer. More specifically, the irradiator13of this embodiment includes a beam source that outputs the laser beam L and a scanner that scans the laser beam L. The scanner is, for example, a galvanometer scanner having an X-axis galvanometer mirror and a Y-axis galvanometer mirror. The laser beam L is, for example, a CO2laser, a fiber laser, or a YAG laser. The laser beam L emitted from the irradiator13passes through a window provided on the upper plate of the chamber1and is irradiated on the material layer6. The irradiator13may be a device that irradiates the material layer6with an electron beam to form a solidified layer. For example, the irradiator13may include a cathode electrode that emits electrons, an anode electrode that converges and accelerates electrons, a solenoid that forms a magnetic field and converges the direction of the electron beam in one direction, and a collector electrode that is electrically connected to the material layer to be irradiated and applies a voltage between the material layer and the cathode electrode.

A cutting device may be provided in the chamber1. The cutting device cuts the surface or unnecessary portions of the solidified layer. The cutting device includes, for example, a machining head that is configured to be movable within the chamber1, and a spindle that is provided on the machining head and grips and rotates a cutting tool.

As shown inFIG.1,FIG.2, andFIG.16, the inert gas supply device15and the fume collector19are connected to the chamber1. The inert gas supply device15is, for example, an inert gas generator that generates inert gas from air, or a gas cylinder that stores inert gas. The inert gas supply device15supplies inert gas of a predetermined concentration to the chamber1. The fume collector19is an electrostatic precipitator or filter that removes fumes from the inert gas. Fumes are generated when the solidified layer is formed. The inert gas containing fumes which is discharged from the chamber1is sent to the fume collector19. The inert gas from which fumes have been removed by the fume collector19is returned to the chamber1. With such a configuration, the inert gas is reused.

The positions and number of inlets and outlets for the inert gas are not limited. For example, the side plate or upper plate of the chamber1or components arranged within the chamber1may be formed with inlets and outlets. The drawings do not show the actual positions and number of inlets and outlets.

A contamination prevention member17is provided in the chamber1so as to surround the window. The contamination prevention member17has a cylindrical shape, stores the inert gas supplied from the inert gas supply device15inside, and discharges downward, which prevents fumes from adhering to the window.

The material supply unit60and the material recovery unit40are provided as the material reuse unit that automatically supplies the material powder M into the chamber1, specifically, to the first build region recoater head31, and recovers the excess material. The material supply unit60and the material recovery unit40are not used when only the second build region Rs is used, that is, when the build region limitation unit8is used. An example of the material reuse unit will be described below, but the material reuse unit is not limited to the following configuration. The material reuse unit includes at least a sieve that removes impurities from the material powder M discharged from the chamber1, and a material carrier that conveys the material powder M.

The material supply unit60includes a main duct71, an intermediate duct69, and an intermediate duct shutter70. The main duct71is provided on the upper plate of the chamber1. The intermediate duct69is provided below the main duct71. An intermediate duct outlet69a, which is an outlet of the intermediate duct69, is opened and closed by one or more intermediate duct shutters70. When the build region limitation unit8is used, the intermediate duct outlet69ais constantly closed by the intermediate duct shutter70. The material powder M contained in a material tank46is supplied to the main duct71, passes through the intermediate duct69, and is supplied from the intermediate duct outlet69ato the first build region recoater head31.

The material recovery unit40includes a recovery carrier41, an impurity removal device43, the material tank46, a drying device47, a supply carrier48, and a vacuum pump49. The recovery carrier41and the supply carrier48are so-called hopper loaders, and are connected to the vacuum pump49via a three-way valve. In this embodiment, the vacuum pump49is shared by the recovery carrier41and the supply carrier48, but the vacuum pump49may be provided separately. By operating the vacuum pump49, a negative pressure is generated in the recovery carrier41or the supply carrier48to convey the material powder M. The impurity removal device43includes, for example, a sieve. The impurity removal device43removes impurities from the excess material sent from the bucket30by the recovery carrier41and sends the material to the material tank46. The material tank46contains unused material powder M and used material powder M with impurities removed. The material tank46is provided with the drying device47such as a heater to dry the material powder M. The material powder M contained in the material tank46is conveyed by the supply carrier48and supplied to the main duct71of the material supply unit60. During the manufacture of the three-dimensional object K, the material recovery unit40and the material supply unit60may automatically recover and re-supply the material powder M. After manufacturing the three-dimensional object K, the material recovery unit40recovers the material powder M. At this time, the material recovery unit40may store the material powder M in the material tank46after removing impurities from the material powder M recovered via a suction nozzle or the like by the impurity removal device43. As described above, the recovery of excess material from the material recovery ports27aand27bor the suction nozzle and the operations of the material recovery unit40and the material supply unit60are not performed when the build region limitation unit8is used.

The base frame4is a frame provided inside the chamber1and has the first build region R and the second build region Rs. The base frame4incorporates the build table5, the material holding wall26, and the bucket30. The first build region R is typically used when additive manufacturing a product continuously. The second build region Rs is typically used when additive manufacturing a test piece for the purpose of evaluating new material powder M or the like. The second build region Rs is a part of the first build region R and is formed within the first build region R.

The build table5is provided in the first build region R and the second build region Rs. The build table5is movable in the vertical direction (the direction of the arrow A) by the build table drive mechanism52. The build table drive mechanism52includes any actuator, and includes, for example, a motor and a ball screw. When additive manufacturing is performed in the second build region Rs, the movable unit84and a base plate83are arranged on the build table5, and the first material layer6is formed on the base plate83. When additive manufacturing is performed in the first build region R, the base plate33is arranged on the build table5, and the first material layer6is formed on the base plate33.

The recoater head drive mechanism51moves the second build region recoater head81or the first build region recoater head31. The recoater head drive mechanism51includes a motor51g, a ball screw51a, and a slide member51b, as shown inFIG.3. The motor51grotates the ball screw51a. The slide member51bhas a nut that is screwed onto the ball screw51a. As will be described later, the second build region recoater head81and the first build region recoater head31share a movable body32. The movable body32is fixed to the slide member51b. The second build region recoater head81or the first build region recoater head31is configured by attaching other components to the movable body32. In other words, the second build region recoater head81and the first build region recoater head31can be changed with each other by exchanging the components. When the slide member51bmoves with the rotation of the ball screw51a, the second build region recoater head81or the first build region recoater head31moves in the direction of the arrow B together with the slide member51b. The ball screw51ais rotatably supported and rotated by the motor51g. The recoater head drive mechanism51is not limited to the above configuration including the motor51gand the ball screw51a. The recoater head drive mechanism51may be configured by including any actuator, and may be, for example, a linear motor.

As shown inFIG.17andFIG.18, the first build region recoater head31includes a material case311, the movable body32, a pair of blades312, a sensor313, a powder guide314, and a material case support frame315.

The material case311contains the material powder M supplied from the material supply unit60. The sensor313detects whether there is material powder M inside the material case311.

The movable body32is a base that fixes and supports the material case311or the material case811. The movable body21is configured to be reciprocatively movable along the direction of the arrow B on the base frame4. By moving the movable body32by the recoater head drive mechanism51, the first build region recoater head31and the second build region recoater head81move in the direction of the arrow B. The movable body32is commonly used by the first build region recoater head31and the second build region recoater head81. The movable body32has a substantially rectangular parallelepiped shape extending in the direction of the arrow C, which is the second horizontal direction orthogonal to the direction of the arrow B. The length of the movable body32in the longitudinal direction is configured to be wider than the width of the base frame4in the direction of the arrow C.

The guide members321are a pair of support bases provided at both ends of the movable body32in the direction of the arrow C. The guide members321are attached to a pair of guide rails provided on the base frame4, respectively. The first build region recoater head31and the second build region recoater head81that are moved by the recoater head drive mechanism51reciprocatively move on the base frame4along the guide rails.

A pair of grooves322are provided on the lower surface of the movable body32. When the second build region recoater head81moves on the base frame4, a partition plate821relatively moves inside the groove322. In other words, the upper portions of a pair of partition plates821are respectively inserted into the pair of grooves322. The groove322extends from one end to the other end of the movable body32in the direction of the arrow B and is formed in a straight line.

A pair of blades312are provided on both side surfaces of the movable body32in the direction of the arrow B, respectively. The blade312is an elongated member extending along the direction of the arrow C. The blade312flattens the material powder M discharged from the material outlet314aformed in the powder guide314to form the material layer6. The length of the blade312in the direction of the arrow C, which is the longitudinal direction, is substantially the same as the width of the first build region R in the direction of the arrow C.

The powder guide314is provided directly below a case outlet, which is a discharge opening of the material case311. The powder guide314is formed with the material outlet314awhich is an opening. The powder guide314guides the flow of the material powder M dropping from the material case311. Thus, the material powder M is freely dropped onto the first build region R and supplied.

The material case support frame315is a frame that fixes and supports the material case311to the movable body32. The material case support frame315has a substantially rectangular parallelepiped shape that is hollow and extends in the direction of the arrow C. The material case support frame315is attached to the upper portion of the movable body32and accommodates the material case311inside.

While discharging the material powder M stored in the material case311from the material outlet314aof the powder guide314, the first build region recoater head31moves in the direction of the arrow B on the first build region R. Then, the first build region recoater head31levels the material powder M discharged to the first build region R by the blade312to form the material layer6.

The blades312, the material case311, the sensor313, the powder guide314, and the material case support frame315are detachably attached to the movable body32. When the first build region recoater head31is replaced with the second build region recoater head81, the blades312, the material case311, the sensor313, the powder guide314, and the material case support frame315that constitute the first build region recoater head31are removed from the movable body32. Then, the blades812, the material case811, the sensor813, and the powder guide814that constitute the second build region recoater head81are attached to the movable body32instead.

The build region limitation unit8is a device for manufacturing the three-dimensional object K within the second build region Rs. The build region limitation unit8is detachably attached inside the chamber1. The build region limitation unit8includes the second build region recoater head81, the non-movable unit82, and the movable unit84.

As shown inFIG.3, the second build region recoater head81is arranged on the base frame4and configured to be reciprocatively movable in the direction of the arrow B by the recoater head drive mechanism51. The second build region recoater head81supplies the material powder M onto the second build region Rs while moving within the chamber1and flattens the material powder M to form the material layer6. That is, the second build region recoater head81forms the material layer6in the second build region Rs. As shown inFIG.4toFIG.7, the second build region recoater head81includes the material case811, the movable body32, the sensor813, a pair of blades812, and the powder guide814.

The material case811is a container that contains the material powder M inside. The material case811is supported by the movable body32. The material case811has a shape extending in the direction of the arrow C orthogonal to the direction of the arrow B, which is the moving direction of the second build region recoater head81. The volume of the material case811is designed to be as large as possible so that the three-dimensional object K can be manufactured by introducing the material powder M only once. Specifically, the maximum length of the material case811in the direction of the arrow C, which is the longitudinal direction, is configured to be substantially the same as the width of the base frame4in the direction of the arrow C. In addition, the upper surface of the material case811is fixed to protrude upward from the upper surface of the movable body32. However, the size of the material case811is determined in consideration of mechanical constraints such as that the material powder M drops appropriately within the material case811, that the flow of the inert gas is not blocked, and that an excessive load is not applied to the movement of the second build region recoater head81. The material case811has a material inlet811a, a case outlet811b, a first inclined surface811c, a second inclined surface811d, a third inclined surface811e, and a fourth inclined surface811f.

The material inlet811ais an opening for introducing the material powder M. The material inlet811ais formed on the upper surface of the material case811and has a substantially rectangular shape extending in the direction of the arrow C. The length of the material inlet811ain the direction of the arrow C is configured to be the same as the width of the base frame4in the direction of the arrow C. The case outlet811bis a substantially rectangular opening through which the material powder M is discharged from the material case811. The case outlet811bis formed on the lower surface of the material case811and extends in substantially the same direction as the material outlet814aof the powder guide814.

The first inclined surface811cand the second inclined surface811dare trapezoidal flat plates arranged along the direction of the arrow C across the case outlet811b. The first inclined surface811cand the second inclined surface811dare inclined toward the case outlet811b. The inclination angle of the first inclined surface811c, that is, the angle formed by the first inclined surface811cand the horizontal plane, and the inclination angle of the second inclined surface811d, that is, the angle formed by the second inclined surface811dand the horizontal plane, may be different from each other or may be the same. Practically, the inclination angle of the first inclined surface811cand the inclination angle of the second inclined surface811dare angles that allow the material powder M to slide down.

The third inclined surface811eand the fourth inclined surface811fare trapezoidal flat plates arranged along the direction of the arrow B across the case outlet811b. The third inclined surface811eand the fourth inclined surface811fare inclined toward the case outlet811b. The inclination angle of the third inclined surface811e, that is, the angle formed by the third inclined surface811eand the horizontal plane, and the inclination angle of the fourth inclined surface811f, that is, the angle formed by the fourth inclined surface811fand the horizontal plane, may be different from each other or may be the same. Practically, the inclination angle of the third inclined surface811eand the inclination angle of the fourth inclined surface811fare angles that allow the material powder M to slide down.

The first inclined surface811c, the third inclined surface811e, and the fourth inclined surface811fare arranged adjacent to each other, and the second inclined surface811d, the third inclined surface811e, and the fourth inclined surface811fare arranged adjacent to each other. Therefore, the lower portion of the material case811has an inverted truncated pyramid shape. As the lower portion of the material case811has an inverted truncated pyramid shape, the material powder M stored inside the material case811flows along the inclined surfaces811c,811d,811e, and811ftoward the case outlet811b. Thus, the amount of the material powder M discharged from the case outlet811bis stabilized, and the amount of the material powder M discharged from the powder guide814is thus stabilized.

The sensor813for detecting whether there is material powder M in the material case811is fixed to the case outlet811bof the material case811. When the sensor813determines that the material case811needs to be replenished with the material powder M, the second build region recoater head81is temporarily stopped. A bottle in which the material powder M is stored may be provided at a place in the chamber1that does not interfere with the additive manufacturing. By doing so, the operator can replenish the material powder M from the bottle to the material case811through the glove box on the door. In this way, even when the material powder M needs to be replenished, the additive manufacturing can be restarted without opening the door during additive manufacturing.

The pair of blades812are provided on both side surfaces of the movable body32in the direction of the arrow B, respectively. The installation position of the blade812is substantially the center position of the movable body32in the direction of the arrow C. The blade812has a substantially rectangular shape extending along the direction of the arrow C, and the length of the blade812is shorter than the length of the blade312. The blade812levels the material powder M discharged from the material outlet814aformed in the powder guide814to form the material layer6. The length of the blade812in the direction of the arrow C, which is the longitudinal direction, is substantially the same as the width of the second build region Rs in the direction of the arrow C. When the blade812is attached to the movable body32, the blade812is arranged inside the pair of partition plates821of the non-movable unit82.

The powder guide814is provided directly below the case outlet811bof the material case811. The powder guide814guides the flow of the material powder M dropping from the case outlet811bof the material case811. Thus, the material powder M is freely dropped onto the second build region Rs and supplied. The powder guide814has a through hole through which the material powder M drops. The inlet of the through hole communicates with the case outlet811bof the material case811. The outlet of the through hole is the material outlet814a. The material powder M contained in the material case811is discharged from the material outlet814a. The material outlet814aextends in the direction of the arrow C, and the length in the direction of the arrow C is substantially the same as the width of the second build region Rs in the direction of the arrow C. When the powder guide814is attached to the movable body32, the material outlet814aof the powder guide814is arranged inside the pair of partition plates821of the non-movable unit82.

The pair of blades812, the material case811, the sensor813, and the powder guide814are detachably attached to the movable body32.

In order to prevent clogging of the material powder M in the material case811and expedite the discharge, the second build region recoater head81may be vibrated. For example, by repeatedly switching the motor51gof the recoater head drive mechanism51between forward rotation and reverse rotation, the second build region recoater head81moves back and forth along the direction of the arrow B. Thus, the second build region recoater head81is vibrated. The means for applying vibration to the second build region recoater head81is not limited to the motor51g. For example, an ultrasonic vibrator may be provided outside the side surface of the material case811to vibrate the second build region recoater head81. The vibrating means such as the motor51gand the ultrasonic vibrator may be controlled by a controller (not shown). In addition, clogging of the material powder M may be prevented by optimizing the inclination angles of the inclined surfaces811c,811d,811e, and811for the area of the case outlet811b. For example, the inclination angle of the first inclined surface811cand the inclination angle of the second inclined surface811dare made different, or the inclination angle of the third inclined surface811eand the inclination angle of the fourth inclined surface811fare made different so as to generate eccentricity in the inverted truncated pyramid shape and make it more difficult for the material powder M to clog.

The non-movable unit82shown inFIG.8toFIG.10andFIG.13is a frame detachably placed on the base frame4. The non-movable unit82is placed on the base frame4inside the chamber1so as to cover the first build region R other than the second build region Rs.

The non-movable unit82includes a flat plate822, a pair of partition plates821, and a second anti-scattering frame823. An outer edge825of the flat plate822has a substantially rectangular shape. A substantially rectangular opening826is formed at the center position of the flat plate822. The flat plate822is a plate that covers the first build region R with a portion other than the opening826. The flat plate822having the opening826forms the second build region Rs that is smaller than the first build region R. The base plate83is arranged inside the opening826, and a relatively small three-dimensional object K such as a test piece is manufactured in the opening826. In other words, the region inside the opening826constitutes the second build region Rs.

The partition plates821are a pair of flat plates arranged along the direction of the arrow B across the opening826. The partition plate821is erected on the upper surface of the flat plate822. The partition plate821prevents the material powder M supplied from the material outlet814aof the second build region recoater head81from scattering outside the region sandwiched by the partition plates821. The partition plate821extends from one end to the other end of the non-movable unit82in the direction of the arrow B, protrudes upward, and is erected on the flat plate822. The positions of the partition plates821in the direction of the arrow C match the positions of the grooves322of the movable body32, respectively. The height of the partition plate821is set so that the upper surface of the partition plate821does not interfere with the second build region recoater head81when the second build region recoater head81moves in the direction of the arrow B.

The second anti-scattering frame823is provided to cover the outer periphery of the opening826. The second anti-scattering frame823is a hollow rectangular frame and is provided so as to cover the outer periphery of the opening826. The second anti-scattering frame823protrudes downward and is vertically fixed to the flat plate822. Here, the length of the outer edge of the second anti-scattering frame823in the direction of the arrow C is defined as the width D1, and the length of the outer edge in the direction of the arrow B is defined as the width W1.

The movable unit84shown inFIG.11toFIG.13is detachably fixed onto the build table5. The movable unit84includes a pedestal841and a first anti-scattering frame842.

The pedestal841is fixed onto the build table5. The pedestal841includes a lower plate841bhaving a rectangular cross section and an upper plate841ahaving a rectangular cross section. The area of the upper surface of the upper plate841ais smaller than the area of the upper surface of the lower plate841b. The upper plate841ais integrally fixed to the center of the upper surface of the lower plate841b. The base plate83is directly fixed to the upper plate841a. The first anti-scattering frame842is attached to the lower plate841b. The lower plate841bis fixed to the build table5.

The first anti-scattering frame842prevents the material powder M supplied to the second build region Rs from scattering onto the build table5. The first anti-scattering frame842is provided at the outer peripheries of the base plate83and the upper plate841a, and surrounds the side surface of the upper plate841a. A gap W22is formed between the first anti-scattering frame842and the side surface of the upper plate841a. The first anti-scattering frame842is a hollow rectangular frame and is erected on the upper surface of the lower plate841b. The first anti-scattering frame842is provided to protrude upward. Here, the length of the opening of the first anti-scattering frame842in the direction of the arrow C is defined as the width D2, and the length of the opening in the direction of the arrow B is defined as the width W21. The opening of the first anti-scattering frame842is formed larger than the outer edge of the second anti-scattering frame823. That is, in comparison with the size of the outer edge of the second anti-scattering frame823, the relationships of D2>D1and W21>W1are established. The first anti-scattering frame842surrounds the second anti-scattering frame823with a gap therebetween.

The base plate83is a plate used when manufacturing a relatively small three-dimensional object K such as a test piece. The material powder M is spread on the upper surface of the base plate83to form the first material layer6. The base plate83has, for example, a rectangular cross section. The size of the upper surface of the base plate83and the size of the upper plate841aof the pedestal841are smaller than the size of the opening of the second anti-scattering frame823. In this way, the outer surfaces of the base plate83and the upper plate841aare prevented from coming into contact with the inner surface of the second anti-scattering frame823when the build table5moves in the vertical direction.

The lower plate841bof the movable unit84is fixed to the build table5via bolts or the like. The base plate83is fixed to the upper surface of the upper plate841aof the movable unit84via bolts or the like. The base plate83is positioned inside the opening826of the non-movable unit82in top view. Therefore, when the build table5moves in the vertical direction, the base plate83moves in the vertical direction inside the opening826, that is, in the second build region Rs. In this embodiment, the pedestal841and the base plate83have substantially square flat surfaces, but not limited thereto.

A plurality of non-movable units82and a plurality of movable units84may be prepared as the build region limitation unit8. That is, the non-movable unit82and the movable unit84with suitable specifications may be used according to the size of the three-dimensional object K to be additive manufactured. Specifically, the non-movable units82may differ in the size of the opening826or the height of the second anti-scattering frame823. The movable unit84that is suitable for each non-movable unit82is prepared. Specifically, the movable units84may differ in the size of the pedestal841in the horizontal direction, the height of the pedestal841, the size of the opening of the first anti-scattering frame842, or the height of the first anti-scattering frame842. The base plate83having a suitable size may be selected according to the size of the three-dimensional object K to be additive manufactured. The longitudinal and lateral sizes of the base plate83need to be smaller than the opening826. Although the thickness of the base plate83may be selected freely, the base plate83is preferably thin within a range that does not cause deformation. The thickness of the base plate83is, for example, approximately 18 mm.

When the build region limitation unit8is used, the maximum height of the three-dimensional object K is determined according to the heights of the first anti-scattering frame842and the second anti-scattering frame823. That is, in order to prevent the material powder M from scattering onto the build table5, during additive manufacturing, the build table5is preferably moved in the vertical direction within a range where the second anti-scattering frame823is inserted through the first anti-scattering frame842. The second anti-scattering frame823is kept to be inserted through the first anti-scattering frame842during additive manufacturing, i.e. during repeating formation of the material layer and formation of the solidified layer. The size of the movable range of the build table5substantially matches the maximum height of the three-dimensional object K. Hence, a high first anti-scattering frame842and a high second anti-scattering frame823are used when additive manufacturing a high three-dimensional object K.

When forming the first material layer6, the upper surface of the base plate83needs to be positioned higher than the upper surface of the flat plate822. That is, the base plate83needs to be arranged so that the upper surface of the base plate83is positioned higher than the upper surface of the flat plate822when the build table5is raised as much as possible within a range where interference between the members does not occur. The pedestal841serves as a spacer that raises the bottom of the base plate83. If the pedestal841alone cannot provide a sufficient height, a connecting member85that is a spacer may be provided between the movable unit84and the base plate83. By using the connecting member85, the pedestal841can be shared even when using a relatively high first anti-scattering frame842and a relatively high second anti-scattering frame823.FIG.19shows a state when a high first anti-scattering frame842and a high second anti-scattering frame823are used and the base plate83is fixed to the pedestal841via the connecting member85.

By exchanging the non-movable unit82and the movable unit84according to the size of the three-dimensional object K to be additive manufactured, it is possible to change the size of the second build region Rs and the maximum height of the three-dimensional object K.

If the upper surface of the base plate83is positioned higher than the upper surface of the flat plate822even without the pedestal841, the pedestal841may not be provided. At this time, the first anti-scattering frame842is attached directly to the build table5. Besides, even when the pedestal841is provided, the first anti-scattering frame842may be attached directly to the build table5.

Next, a method of attaching the build region limitation unit8in the chamber1and a method of manufacturing the three-dimensional object K using the build region limitation unit8will be described. Regarding the method of attaching the build region limitation unit8, a case where the first build region recoater head31is replaced with the second build region recoater head81will be described as an example. In addition, the order of the following procedures may be changed.

First, the base plate83and the movable unit84are installed. The base plate83is fixed to the movable unit84. As shown inFIG.13, the movable unit84to which the base plate83is attached is fixed onto the build table5.

Next, the first build region recoater head31is replaced with the small region recoater81. Specifically, the blades312, the sensor313, the material case311, the material case support frame315, and the powder guide314are removed from the movable body32. Then, the blades812, the powder guide814, the material case811, and the sensor813are attached to the movable body32. In this way, the small region recoater81is arranged on the base frame4.

Then, the non-movable unit82is placed on the base frame4to cover the first build region R except for the second build region Rs. At this time, the base plate83is arranged within the opening826of the non-movable unit82.

In this way, the movable unit84and the base plate83are attached, the first build region recoater head31is replaced with the second build region recoater head81, and the non-movable unit82is placed. Thus, the build region limitation unit8is attached inside the chamber1.

As shown inFIG.14, the opening of the second anti-scattering frame823is formed larger than the outer edges of the base plate83and the upper plate841a. Also, the opening of the first anti-scattering frame842is formed larger than the outer edge of the second anti-scattering frame823. Hence, when the build table5moves in the vertical direction, the outer surfaces of the base plate83and the upper plate841ado not contact the inner surface of the second anti-scattering frame823. Similarly, the outer surface of the second anti-scattering frame823does not contact the inner surface of the first anti-scattering frame842.

After the build region limitation unit8is installed in the chamber1as described above, additive manufacturing is performed by using the build region limitation unit8. First, the operator puts the material powder M to be used into the material inlet811aof the material case811. Then, inert gas is supplied into the chamber1.

Here, the moving direction of the second build region recoater head81will be supplemented. For formation of the solidified layer, it is enough for the second build region recoater head81to move in only one direction across the second build region Rs. When the blades812are provided on both side surfaces of the movable body32as in this embodiment, the moving direction may be different for each material layer6formed. For example, the moving direction of the second build region recoater head81may be set so that the moving direction of the even-numbered layers is from left to right and the moving direction of the odd-numbered layers is from right to left.

Furthermore, the flow of inert gas may change depending on the position of the second build region recoater head81. For example, the flow of inert gas may change between a case where the second build region recoater head81is on the left side of the second build region Rs and a case where the second build region recoater head81is on the right side of the second build region Rs, which in turn affects the quality of additive manufacturing. In particular, when additive manufacturing is performed by using the build region limitation unit8in order to examine the use of new material powder, sometimes appropriate irradiation conditions have not yet been grasped. At this time, projections are likely to be formed by spatters adhering to the solidified layer, and the blade812may collide with the projections when forming the material layer6. Therefore, when using the material powder M for which the appropriate irradiation conditions have not yet been grasped, it is preferable to emphasize the stability of additive manufacturing, and move the second build region recoater head81reciprocatively in forming one material layer6. By doing so, the position of the second build region recoater head81is constant during formation of the solidified layer, so the stability of additive manufacturing is improved.

First, the first material layer6and the first solidified layer are formed. The build table5is positioned such that the distance between the lower end of the blade812and the upper surface of the base plate83corresponds to the size of one material layer6. Here, the second build region recoater head81moves reciprocatively.FIG.1andFIG.2show the reciprocating movement of the second build region recoater head81when the initial position of the second build region recoater head81is on the left side. The second build region recoater head81moves from the left side to the right side with respect to the second build region Rs, and then moves from the right side to the left side with respect to the second build region Rs. The material powder M is spread from the material outlet814abetween the pair of partition plates821to form the first material layer6on the base plate83. The irradiator13irradiates and solidifies a predetermined portion of the first material layer6with the laser beam L to form the first solidified layer.

After the first solidified layer is formed, the second material layer6and the second solidified layer are formed. The build table5is lowered by one material layer6. The second build region recoater head81moves reciprocatively again. The material powder M is spread from the material outlet814abetween the pair of partition plates821to form the second material layer6on the first solidified layer. The irradiator13irradiates and solidifies a predetermined portion of the second material layer6with the laser beam L to form the second solidified layer.

The above processes are repeated to form the third and subsequent solidified layers. In this manner, a plurality of solidified layers are added to manufacture the three-dimensional object K. Adjacent solidified layers are strongly adhered to each other.

The movement range of the second build region recoater head81may be set within a range that allows the material layer6to be formed on the second build region Rs. A controller (not shown) controls the second build region recoater head81to reciprocatively move between a position on the right side of the opening826and a position on the left side of the opening826. Since the movement range of the second build region recoater head81only needs to cover the second build region Rs, the movement region of the second build region recoater head81may be set to be narrower than the movement range of the first build region recoater head31. However, if the second build region recoater head81is too close to the second build region Rs during formation of the solidified layer, there is a possibility that the flow of inert gas may not be properly formed directly above the second build region Rs. In the case where the stability of additive manufacturing is emphasized, the movement range may be set such that the position of the second build region recoater head81during formation of the solidified layer is distant from the second build region Rs to some extent. Further, in order to prevent the material powder M from falling into the material recovery port27b, the second build region recoater head81may be controlled so as not to reach the material recovery ports27bprovided at the left and right ends of the base frame4, or a cover may be provided to cover the material recovery port27b.

As shown inFIG.15, in manufacturing the three-dimensional object K, part of the material powder M supplied onto the base plate83falls through the gap between the base plate83and the second anti-scattering frame823and accumulates inside the first anti-scattering frame842. Further, the material powder M extruded by the moving second build region recoater head81is accumulated between the pair of partition plates821. The first anti-scattering frame842and the second anti-scattering frame823prevent the material powder M from scattering onto the build table5outside the first anti-scattering frame842. The partition plate821prevents the material powder M from scattering onto the flat plate822outside the partition plate821. In particular, by providing the groove322on the lower surface of the movable body32and inserting the partition plate821into the groove322, scattering of the material powder M is more properly prevented.

The first anti-scattering frame842and the second anti-scattering frame823are not connected. Since the non-movable unit82and the movable unit84are independently provided, the build region limitation unit is easily attached or detached. By using the build region limitation unit8of this embodiment, it is possible to minimize the locations where the material powder M remains. Therefore, the cleaning work required when different material powder M is to be used after additive manufacturing can be performed more easily. Specifically, the inside of the first anti-scattering frame842, the inside of the pair of partition plates821, the upper surface of the base frame4, and the second build region recoater head81may be cleaned. In particular, it is possible to prevent the used material powder M from being mixed into the material recovery unit40and the material supply unit60. Therefore, when additive manufacturing is performed by using the material recovery unit40and the material supply unit60next time, the work therefor becomes simple.

The build region limitation unit8can be suitably used when additive manufacturing a relatively small three-dimensional object K. In the above description, a case of using the build region limitation unit8for manufacturing a test piece when considering the use of new material powder is taken as an example, but the build region limitation unit8is not limited to such an application. For example, the build region limitation unit8can be suitably used even when the material powder M is preheated to a high temperature for additive manufacturing. When the build region limitation unit8is used, the material powder M is not spread over a large portion of the build table5. Therefore, it is possible to prevent heat from being transferred from the material powder M to the build table5and the surrounding members.