JP2018021238A - Powder bed fusion unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder bed fusion bonding device capable of continuing modeling for a long time even when irradiated with a high-power laser beam. SOLUTION: A laser beam emitting part 201 for emitting a laser beam, a decompressible chamber 11 provided with a laser beam transmitting window 12, and a chamber 11 provided in the chamber 11 to form a thin layer of powder material. A powder bed fusion bonding apparatus 10 including a thin layer forming unit 202 and a reflecting mirror 13 arranged between the transmission window 12 and the thin layer forming unit 202 and directing an optical path of laser light to the thin layer forming unit 202. Provided. [Selection diagram] Figure 1

Description

  The present invention relates to a powder bed fusion bonding apparatus that forms a three-dimensional shaped object by selectively heating and solidifying with a laser beam while depositing a powder material in layers.

  The powder bed fusion bonding apparatus repeats the steps of forming a thin layer of powder material and sintering or melting and solidifying the specific region by heating with a laser beam several hundred to several thousand times. Create a three-dimensional model.

  The following patent document describes such a powder bed melt bonding apparatus.

JP 2008-155538 A

  By the way, in the powder bed fusion bonding apparatus, a technique of using a resin powder as a powder material is generally used, but in recent years, a technique of producing a prototype or a product using a metal powder has been proposed.

  When metal powder is used, modeling may be performed in a high vacuum chamber in order to prevent oxidation of the metal powder.

  However, in the conventional powder bed fusion bonding apparatus, there is a problem that when a high-power laser beam is irradiated, the metal material is deposited on the transmission window and modeling can be performed only for a short time.

  Accordingly, an object of the present invention is to provide a powder bed fusion bonding apparatus capable of continuing modeling for a long time even when irradiated with a high-power laser beam.

  According to one aspect, a laser beam emitting portion that emits laser beam, a depressurizable chamber provided with a transmission window for the laser beam, and a thin film that is provided in the chamber and in which a thin layer of powder material is formed. There is provided a powder bed fusion bonding apparatus comprising: a layer forming part; and a reflecting mirror disposed between the transmission window and the thin layer forming part and directing an optical path of the laser beam toward the thin layer forming part.

  According to the powder bed fusion bonding apparatus of the above aspect, the thin layer forming unit is irradiated with the laser light reflected by the reflecting mirror. Even if a metal component is deposited on the reflecting mirror, the optical characteristics hardly change, so that long-time modeling can be performed using a high-power laser beam.

It is a figure which shows the powder bed fusion | bonding apparatus which concerns on 1st Embodiment of this invention. (A) is a top view of the thin layer formation part of the powder bed fusion | bonding apparatus of FIG. 1, (b) is sectional drawing which follows the II line | wire of (a). It is a block diagram of the laser emission part of the powder bed fusion | bonding apparatus of FIG. It is a figure which shows the locus | trajectory of the evaporation particle | grains in the chamber of the powder bed fusion | bonding apparatus of FIG. It is a figure which shows the powder bed fusion | bonding apparatus which concerns on the modification 1 of 1st Embodiment. It is a figure which shows the powder bed fusion | bonding apparatus which concerns on the modification 2 of 1st Embodiment. It is a figure which shows the powder bed fusion | bonding apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows the cooling structure of the reflective mirror of the powder bed fusion | bonding apparatus of FIG. It is a figure which shows the powder bed fusion | bonding apparatus which concerns on 3rd Embodiment of this invention. It is sectional drawing of the reflective mirror of the powder bed fusion | bonding apparatus of FIG.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
(1) About a powder bed melt-bonding apparatus FIG. 1: is a figure which shows the structure of the powder bed melt-bonding apparatus 10 which concerns on 1st Embodiment of this invention.
As shown in FIG. 1, the powder bed fusion bonding apparatus 10 according to the present embodiment includes a laser beam emitting unit 201, a thin layer forming unit 202 in which modeling is performed, a reflecting mirror 31, and a control unit 203 that controls modeling. And.

  The thin layer forming unit 202 is installed in a chamber (container) 11 that can be depressurized in order to prevent moisture from adhering to the metal powder and oxidation / nitridation of the metal powder.

  An exhaust pump 204 is attached to the chamber 11. The exhaust pump 204 exhausts the gas in the chamber 11 and keeps it in a vacuum state during modeling.

  The laser light emitting unit 201 is provided outside the chamber 11 and can emit laser light into the chamber 11 via a transmission window (transmission window) 12.

  The reflecting mirror 31 is disposed above the thin layer forming unit 202. The reflecting mirror 31 changes the optical path of the laser beam emitted from the laser beam emitting unit 201 toward the lower thin layer forming unit 202.

  The control unit 203 is connected to the laser beam emitting unit 201, the thin layer forming unit 202, and the exhaust pump 204, and exchanges electrical signals with the units 201, 202, and 204 to control modeling. Thereby, it is possible to control modeling automatically.

  Below, the detail of each part 201,202 of the powder bed fusion bonding apparatus 10 and the reflective mirror 31 is demonstrated.

(2) Configuration of Thin Layer Forming Unit 202 FIGS. 2A and 2B are diagrams showing the configuration of the thin layer forming unit 202. FIG. 2A is a top view, and FIG. 2B is a cross-sectional view taken along the line II of FIG. 2A. In FIG. 2A, the reflecting mirror 31 and the laser beam emitting unit 201 are omitted.

  As shown in FIGS. 2A and 2B, the thin layer forming unit 202 includes a thin layer forming container 21 in which modeling is performed, and a first powder material storage container 22a and a second powder material installed on both sides thereof. A storage container 22b and a recoater 13 for carrying the powder material 20 and forming a thin layer 20a of the powder material are provided.

  In addition, a left flange 23a is provided between the thin layer forming container 21 and the first powder material storage container 22a, and a right flange 23b is provided between the thin layer forming container 21 and the first powder material storage container 22b.

  The 1st powder material storage container 22a, the left side flange 23a, the thin layer formation container 21, the right side flange 23b, and the 2nd powder material storage container 22b are joined so that the upper surface may become flush. Thereby, the recoater 13 can move smoothly over all the regions on all the containers 22a, 21 and 22b.

  In the thin layer forming container 21, as shown in FIG. 2B, a thin layer 20a of a powder material is formed on a part table 24 that also serves as the bottom of the container 21, and the thin layer 20a of the powder material is irradiated with laser light. Thus, the solidified layer 20b is formed.

  Then, the part table 24 is sequentially moved downward, the solidified layer 20b is stacked, and a three-dimensional structure is formed.

  Here, the example in which the thin layer 20a of the powder material is melted and solidified to form the solidified layer 20b has been described. However, the thin layer 20b of the powder material is sintered without being melted and sintered. A layer may be formed. The same applies to the following description.

  In the first powder material storage container 22a, the powder material 20 is stored on the first feed table 25a that also serves as the bottom of the container 22a, and in the second powder material storage container 22b, the second feed that also serves as the bottom of the container 22b. The powder material 20 is stored on the table 25b.

  When one of the first powder material storage container 22a and the second powder material storage container 22b is the supply side of the powder material 20, the other of the powder material 20 remaining after the thin layer 20a of the powder material is formed. The storage side.

  Support shafts 26, 27a, and 27b are attached to the lower surfaces of the part table 24, the first feed table 25a, and the second feed table 25b, respectively. The support shafts 26, 27a and 27b are connected to a driving device (not shown).

  The drive device is controlled by a control signal from the control unit 203 to raise the supply-side feed table 25a or 25b to supply the powder material 20, and to lower the storage-side feed table 25b or 25a to remain. Contains powdered material.

  The recoater 13 is controlled by a control signal from the control unit 203 and moves over the entire area on the upper surfaces of the first powder material storage container 22a, the thin layer forming container 21 and the second powder material storage container 22b.

  While moving, the recoater 13 pushes the powder material 20 on the powder material storage container 22a or 22b on the supply side, leveles the surface while carrying the powder material 20 into the thin layer forming container 21, and above the part table 24. A thin layer 20a is formed. Further, the surplus powder material 20 is conveyed to the powder material storage container 22a or 22b on the storage side and stored on the feed table 25b or 25a.

  Further, in order to heat and raise the temperature of the powder material 20 accommodated in the containers 22a and 22b and the thin layer 20a of the powder material in the container 21, other heating means such as a heater (not shown) and a heating light source are provided. The heating means may be built in each container 21, 22a and 22b, or may be provided around each container 21, 22a and 22b.

(3) Powder material Examples of the powder material 20 that can be used in the powder bed fusion bonding apparatus 10 of the present embodiment include metal powders such as aluminum, titanium, other metal elements, and alloys thereof.

  In some cases, a powder of a compound that deposits a metal by irradiation with laser light in vacuum may be used.

(4) Configuration of Laser Light Emitting Unit 201 FIG. 3 is a block diagram showing the laser light emitting unit 201 of the powder bed fusion bonding apparatus 10.

  As shown in FIG. 3, the laser light emitting unit 201 includes a laser light source 223 that emits laser light, an optical scanning element 221, and a focus optical system 222. The light emitting unit 201 is installed outside the chamber 11.

  As the laser light source 223, for example, a YAG laser light source that emits near-infrared laser light having a wavelength of about 1000 nm, a fiber laser light source, or the like can be used.

Note that the wavelength used may be appropriately changed in consideration of the wavelength absorptivity, cost performance, etc. of the powder material. For example, a high-power CO ₂ laser light source that emits laser light in the far-infrared region having a wavelength of about 10,000 nm is used. Also good.

  The optical scanning element 221 includes a galvanometer mirror (X mirror) 221a that changes the angle with respect to the laser light and scans the laser light in the X direction, and a galvanometer mirror (Y that changes the angle with respect to the laser light and scans the laser light in the Y direction. Mirror) 221b.

  The laser beam is scanned on the thin layer forming container 21 in the X direction and the Y direction by the optical scanning element 221.

  The focus optical system 222 has a function of adjusting the focal length of the laser light. The focus optical system 222 operates so that the focal length that changes according to the scanning position of the laser light matches the surface of the thin layer 20a of the powder material.

  The optical axis of the optical scanning element 221 is an axis along the center of the scanning range of the optical scanning element 221, and the optical axis extends in the horizontal direction and reaches the reflecting mirror 31 as shown in FIG.

  The laser light incident along the optical axis is reflected downward by 90 degrees by the reflecting mirror 31 and is applied to the center of the thin layer forming container 21. Thereby, the relationship between the scanning position and the focal length is an object around the optical axis, the control of the focus optical system 222 is facilitated, and irradiation can be performed with high accuracy.

  The X mirror 221a, the Y mirror 221b, and the focus optical system 222 of the optical scanning element 221 operate according to control signals from the XYZ driver 224.

  The XYZ driver 224 is controlled by a controller (control device) 225, and the controller 225 also controls ON (lighting) and OFF (lighting off) of the laser light source 223. As the controller 225, for example, a computer including a CPU (Central Processing Unit) and a memory storing a control program can be used.

  The laser light emitted from the laser light source 223 is sequentially irradiated to the thin layer 20a of the material on the part table 24 of the thin layer forming unit 202 through the path of the focus optical system 21c, the X mirror 221a, and the Y mirror 221b.

  The laser light is selectively irradiated to the sintered or melted region by being operated by controlling the optical scanning element 221 by the controller 225.

  Furthermore, while the laser beam is being scanned, the focal length is adjusted by constantly moving the lens of the optical system 222 so that the laser beam is focused on just the surface of the thin layer 20a of the powder material.

  The optical scanning element 221 is controlled based on slice data (drawing pattern) of a three-dimensional structure to be produced.

(5) Configuration of Chamber 11 As shown in FIG. 1, the chamber 11 has a main body 11a for accommodating the thin layer forming portion 202 and a lens barrel portion 11b. The lens barrel portion 11b is integrally formed on the main body 11a, and the reflecting mirror 31 is accommodated in the lens barrel portion 11b.

  A branch part 11c that branches out and extends outward is provided on the side of the lens barrel part 11b, and a transmission window 12 is attached to the tip of the branch part 11c. A laser beam emitting portion 201 is attached to a portion facing the transmission window 12.

  As described above, the transmission window 12 is provided in the back of the branching portion 11 c that branches and extends, and the transmission window 12 is disposed at a position where the thin layer forming portion 202 cannot be directly visually recognized. Thereby, the transmittance | permeability fall of the permeation | transmission window 12 by vapor deposition of the evaporation particle which scatters linearly from the surface of the thin layer 20a can be prevented.

  An exhaust pump 204 is connected to the chamber 11 composed of the main body 11a and the lens barrel portion 11b, and the inside thereof can be decompressed.

  When performing modeling, the inside of the interior is kept at a high vacuum by the exhaust pump 204 in order to prevent deterioration of the powder material 20 made of metal.

  When the inside of the chamber 11 is maintained at a high vacuum in this way, the partial pressure of oxygen and water vapor can be easily reduced as compared with the case where an inert gas atmosphere is used, and the quality of the model can be improved.

  Furthermore, in the modeling process in vacuum, the thermal conductivity is low and the heat retaining property is kept high as compared with that in atmospheric pressure. For this reason, in modeling in high vacuum, rapid cooling of the modeled object in the thin layer forming unit 202 hardly occurs, and as a result, a highly accurate modeled object with less thermal strain can be obtained.

  In the conventional modeling in an inert gas atmosphere, in order to prevent deformation due to thermal strain, it is necessary to model the foundation and the scaffolding connected to the platform prior to modeling the modeled object, and perform modeling in a form connected to them, Furthermore, it is necessary to perform annealing after shaping. For this reason, it is necessary to increase the number of man-hours for removing the laser, the waste of electric power for annealing, and the scaffold required to form the foundation and the scaffold.

  On the other hand, in modeling in a high vacuum, processes such as foundation and scaffold modeling and annealing are unnecessary, and the productivity is excellent.

(6) Movement of Evaporated Particles in Chamber 11 FIG. 4 is a diagram showing the movement of evaporated particles in the chamber 11 of the powder bed fusion bonding apparatus 10.

  As shown in FIG. 4, the surface of the thin layer forming unit 202 is irradiated with laser light through the reflecting mirror 31. As a result, the thin layer 20a of the powder material is heated and melted or sintered to solidify, and a part of the powder material 20 evaporates.

  The molecules (or atoms) of the evaporated powder material are emitted radially from the position Q of the laser beam being examined. Since the inside of the chamber 11 is kept at a high vacuum and the mean free path is long, the molecules of the evaporated powder material reach the inner wall of the chamber 11 and the reflecting mirror 31 in a linear locus without being scattered, and are deposited. Is done.

  Thus, the vapor deposition film which consists of a metal component of the powder material vapor-deposited on the surface of the reflective mirror 31 forms a smooth vapor deposition film on the reflective film 31, and does not impair the function of the reflective mirror 31. Therefore, the function of the reflecting mirror 31 is maintained even when long-time modeling is performed.

  On the other hand, in the chamber 11 of the present embodiment, the transmission window 12 is disposed at the back of the branching portion 11c further branched from the lens barrel portion 11b.

  The alternate long and short dash line in the figure indicates that the vapor particle trajectory reaches the portion closest to the laser window 12.

  As shown in the figure, the vaporized particles cannot reach the transmission window 12 by being blocked by the inner wall of the chamber 11 regardless of the angle at which the vaporized particles fly off from the thin layer forming unit 202.

  Therefore, according to this embodiment, vapor deposition of the material component on the transmission window 12 can be prevented, and opaqueness of the transmission window 12 due to vapor deposition can be prevented.

  In the conventional powder bed fusion bonding apparatus, when forming a powder material having a high melting point such as a metal, it is difficult to obtain a molded article having a filling rate of 100% because a slight amount of bubbles are formed. For example, the filling rate remained at about 97% to 98%.

  According to the investigations by the inventors of the present application, it has been found that in order to make the filling rate of the molded article closer to 100%, it is sufficient to increase the intensity of the laser beam and perform overexposure.

  However, when the intensity of the laser beam is increased in the conventional powder bed fusion bonding apparatus, the deposition amount of the metal film on the transmission window also increases, so it is difficult to set the filling rate to 100%.

  On the other hand, in the powder bed fusion bonding apparatus 10 of the present embodiment, there is no problem even if the amount of deposition on the reflecting mirror 31 is increased, and thus modeling using a high-power laser beam is possible.

  Therefore, according to the powder bed fusion bonding apparatus 10, a shaped article with a higher filling rate can be produced.

(Modification 1 of the first embodiment)
Hereinafter, modified examples of the first embodiment will be described.

  FIG. 5 is a diagram illustrating a powder bed fusion bonding apparatus 20 according to Modification 1 of the first embodiment. Since the recoater 13, the control unit 203, and the exhaust pump 204 are the same as those of the powder bed fusion bonding apparatus 10, illustration thereof is omitted.

  As shown in FIG. 5, the powder melt bonding apparatus 20 of the present modification is different from the powder bed melt bonding apparatus 10 of FIG. 1 in that the lens barrel portion 11 b is not provided in the chamber 11.

  As shown in the figure, the chamber 11 of the powder bed fusion bonding apparatus 20 is provided with a reflecting mirror 31 on the upper part of the main body 11 a that houses the thin layer forming unit 202. And the transmission window 12 and the laser beam emission part 201 are provided in the side part of the main body 11a.

  Further, a shielding plate 11 d extending from the main body 11 a below the transmission window 12 toward the reflecting mirror 31 is provided. The shielding plate 11d prevents the vapor deposition particles emitted from the thin layer forming unit 202 from entering the transmission window 12 and prevents the transmission window 12 from becoming opaque.

  Also by the powder bed fusion bonding apparatus 20 of this modification, vapor deposition of the material component to the transmission window 12 can be prevented, and modeling for a long time or modeling under high intensity laser light can be performed.

(Modification 2 of the first embodiment)
FIG. 6 is a diagram illustrating a powder bed fusion bonding apparatus 30 according to Modification 2 of the first embodiment. Since the recoater 13, the control unit 203, and the exhaust pump 204 are the same as those of the powder bed fusion bonding apparatus 10, illustration thereof is omitted.

  In the example shown in FIGS. 1 and 5, the laser light from the laser light emitting unit 201 is incident on the chamber 11 in a substantially horizontal direction. However, the present embodiment is not limited to this.

  As in the powder bed fusion bonding apparatus 30 in FIG. 6, the laser beam from the laser beam emitting unit 201 may be incident obliquely upward.

  In this case, it is preferable that the transmission window 12 is tilted so that the evaporated particles emitted from the thin layer forming unit 202 are not easily incident.

(Second Embodiment)
FIG. 7 is a diagram illustrating a configuration of a powder bed fusion bonding apparatus 40 according to the second embodiment. In the powder bed melt bonding apparatus 40 of FIG. 7, the configuration of the chamber 11, the transmission window 12, the laser beam emitting unit 201, the thin layer forming unit 202, the control unit 203, and the exhaust pump 204 is the same as the powder bed melt bonding apparatus of FIG. 10, the same reference numerals are given and detailed description thereof is omitted.

  As already described, the metal component of the material is deposited on the reflecting mirror 31 to form a film along with modeling.

  Depending on the deposited metal component, the reflectance of the reflecting mirror 31 may decrease, and the reflecting mirror 31 may generate heat.

  Therefore, as shown in FIG. 7, the powder bed fusion bonding apparatus 40 of the present embodiment is provided with a cooler 41 for cooling the reflecting mirror 31. The cooler 41 cools the reflecting mirror 31 by supplying a cooling liquid to the reflecting mirror 31.

  FIG. 8 is a partially enlarged view showing a cooling structure of the reflecting mirror 31 of FIG.

  As shown in FIG. 8, a flow path 31 a for flowing a cooling liquid such as water, oil, or chlorofluorocarbon is provided inside the reflecting mirror 31. One end of the coolant channel 31a is connected to the supply pipe 41a, and the other end is connected to the discharge pipe 41b.

  The supply pipe 41a and the discharge pipe 41b are connected to the cooler 41.

  The reflecting mirror 31 heated by the laser beam transmits the heat to the coolant flowing through the flow path 31a. The coolant heated by the reflecting mirror 31 flows into the cooler 41 through the discharge pipe 41b. The cooler 41 cools the coolant heated by the reflecting mirror 31 and then supplies the cooling liquid to the reflecting mirror 31 via the supply pipe 41a. In this way, the reflecting mirror 31 is cooled.

  According to the present embodiment, even when the reflectance is lowered by vapor deposition on the surface of the reflecting mirror 31, the reflecting mirror 31 can be prevented from being distorted or burned by cooling the reflecting mirror 31.

(Third embodiment)
FIG. 9 is a diagram illustrating a configuration of a powder bed fusion bonding apparatus 50 according to the third embodiment. In the present embodiment, the configurations of the transmission window 12, the laser beam emitting unit 201, the thin layer forming unit 202, and the exhaust pump 204 are the same as those of the powder melt bonding apparatus 10 in FIG. Omitted.

  As shown in FIG. 9, the powder bed melting and bonding apparatus 50 according to the present embodiment includes the wiping unit 33 that removes the film deposited on the reflecting mirror 131, and the powder melting shown in FIGS. 1 to 8. Different from the coupling device 60.

  The wiping unit 33 is provided with a spatula such as silicone rubber, and the surface of the reflecting mirror 131 is rubbed under the control of the control unit 203 to remove the deposited film adhering to the surface. Restore functionality.

  In addition, when the vapor deposition film which fell from the reflecting mirror 131 falls to the thin layer formation part 202, there exists a possibility of reducing the quality of a molded article. Therefore, a receiving unit 34 is provided to collect the deposited film that has dropped.

  Under the control of the control unit 203, the receiving unit 34 moves under the reflecting mirror 131 immediately before the wiping unit 33 operates and collects the deposited film powder that has dropped. After the operation of the wiping unit 33 is completed, the wiping unit 33 is retracted to the side to enable laser light irradiation.

  Note that the wiping operation by the wiping unit 33 may be performed after one modeling is completed, for example. Moreover, after the modeling of one thin layer 20a is completed, the laser beam may be stopped during the period until the next thin layer 20a is modeled.

  In this embodiment, since the vapor deposition film is removed by rubbing the surface of the reflection mirror 131 with the wiping portion 33, it is preferable that the vapor deposition film is easily peeled off from the reflection mirror 131.

  Below, the reflective mirror 131 suitable for the powder bed fusion | bonding apparatus 50 of this embodiment is demonstrated.

  FIG. 10 is a cross-sectional view of a reflecting mirror 131 that can be used in the powder bed fusion bonding apparatus 50 of FIG.

  As shown in FIG. 10, the reflecting mirror 131 includes a substrate 132 whose surface is polished into a mirror surface. On the substrate 132, for example, a reflective layer 133 made of a material having high reflectivity with respect to infrared light, such as gold, is provided. An oil repellent coating layer 134 is formed on the reflective layer 133.

  As the oil repellent coating layer 134, for example, an organic fluorine compound can be used. The organic fluorine compound has high transparency with respect to laser light in the infrared region, and is excellent in releasability from the deposited material component. In addition, the oil-repellent coating layer 134 can be regenerated by simply applying a liquid agent in which an organic fluorine compound is dispersed in an appropriate solvent on the reflective layer 133 during maintenance.

  Note that in the reflecting mirror 131, the reflecting layer 133 may not perform its function after the material components are deposited, and thus the reflecting layer 133 may be omitted in advance.

  As described above, according to the powder bed fusion bond 50 of the present embodiment, the deposited film attached to the reflecting mirror 131 can be removed, so that modeling can be performed using high-power laser light for a long period of time.

10, 20, 30, 40, 50 ... powder bed fusion bonding, 11 ... chamber, 11a ... main body, 11b ... lens barrel, 11c ... branching part, 11d ... shielding plate, 12 ... transmission window, 13 ... recoater, 201 ... Laser light emitting unit, 202 ... thin layer forming unit, 203 ... control unit, 204 ... exhaust pump, 20 ... powder material, 20a ... thin layer, 20b ... solidified layer, 21 ... thin layer forming container, 22a, 22b ... powder material Storage container, 23a, 23b ... Flange, 24 ... Part table, 25a, 25b ... Feed table, 26, 27a, 27b ... Support shaft, 31, 131 ... Reflector, 31a ... Coolant flow path, 33 ... Wiping part, 34 ... tray, 41 ... cooler, 41a ... supply tube, 41b ... discharge tube, 221 ... optical scanning element, 221a, 221b ... galvanometer, 222 ... focus optical system, 223 ... laser light source, 2 4 ... XYZ driver, 225 ... controller.

Claims (9)

A laser beam emitting section for emitting a laser beam;
A depressurizable chamber provided with a laser light transmission window;
A thin layer forming portion provided in the chamber and formed with a thin layer of powder material;
A reflecting mirror disposed between the transmission window and the thin layer forming portion, and directing the optical path of the laser beam toward the thin layer forming portion;
A powder bed fusion bonding apparatus comprising:   2. The powder bed fusion bonding apparatus according to claim 1, wherein the transmission window is provided in a portion where the thin layer forming portion cannot be directly visually recognized.   The powder bed fusion bonding apparatus according to claim 2, wherein the reflecting mirror is disposed above a central axis of the thin layer forming portion.   The powder bed fusion bonding apparatus according to any one of claims 1 to 3, further comprising a cooling mechanism for cooling the reflecting mirror.   The powder bed fusion bonding apparatus according to claim 4, wherein a flow path for flowing a cooling liquid is provided inside the reflecting mirror.   6. The powder bed fusion bonding apparatus according to claim 1, wherein the reflecting mirror is covered with an oil repellent film.   The powder bed fusion bonding apparatus according to claim 6, further comprising a mechanism for removing a film of the powder material deposited on the surface of the reflecting mirror. The chamber includes a lens barrel portion protruding above the thin layer forming portion,
8. The device according to claim 1, wherein the reflecting mirror is housed in the lens barrel portion, and the transmission window is provided at the back of a branch portion branched from the lens barrel portion. A powder bed melt bonding apparatus according to claim 1.   2. An exhaust device capable of reducing pressure to a degree of vacuum indicating a length in which a mean free path of molecules in the chamber exceeds a distance between the thin layer forming portion and the reflecting mirror is provided. The powder bed fusion bonding apparatus according to any one of 8.

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