Patent Description:
In recent years, a three-dimensional PBF-AM apparatus has been known that irradiates metal powder (powder layer) spread in layers on a build plate with an electron beam to melt and solidify the metal powder, and sequentially stacks the solidified layers by moving the build plate to form a three-dimensional build object (see, for example, Patent Literature <NUM>).

In this type of three-dimensional PBF-AM apparatus, a phenomenon may occur in which individual powder particles are charged by irradiation with an electron beam, and powder is scattered in a smoke form by Coulomb repulsive force. This phenomenon is called smoke, and when smoke occurs, it becomes difficult to continue the building work. Therefore, in the three-dimensional PBF-AM apparatus, the generation of smoke is suppressed by preheating the powder layer.

<CIT> discloses a method and apparatus for producing three-dimensional objects from a powder material which is capable of solidification by irradiation with a high-energy beam. The method comprises homogeneously pre-heating the powder material by scanning with the high-energy beam along predetermined paths over a pre-heating area so that consecutive paths are separated by a minimum security distance which is adapted to prevent undesirable summation effects in the pre-heating area, and then solidifying the powder material by fusing together the powder material.

<CIT> discloses a method for producing three-dimensional objects layer by layer using a powdery material which can be solidified by irradiating it with at least two electron beams, said method comprises a pre-heating step, wherein the pre-heating step comprises the sub-step of scanning a pre-heating powder layer area by scanning a first electron beam in a first region and by scanning a second electron beam in a second region distributed over the pre-heating powder layer area, wherein consecutively scanned paths are separated by, at least, a security distance, said sub-step further comprising the step of synchronising the preheating of said first and second electron beams when simultaneously preheating said powder material within said first and second regions respectively, so that said first and second electron beams are always separated to each other with at least a minimum security distance.

<CIT> discloses an apparatus and a method for manufacturing a three-dimensional object by successive consolidation, layer by layer, of selected zones of a layer of powder, the consolidated zones corresponding to successive sections of the three-dimensional object, said method comprising the following steps taken in order: a - depositing a layer of powder on a support; b - at least partially preheating said powder layer by means of a first electron beam energy source; c - heating said powder layer using a second laser beam energy source capable of fusing the powder particles; d - carrying out the relative displacement of the laser beam of the said second source with respect to the object according to a predetermined trajectory so as to merge the powder and form a section of the said object; e - repeating at least steps a, c and d so as to form several layers of superimposed fused material constituting said object.

<CIT> discloses an electron beam selective preheating scanning method comprising the steps that, a base plate is divided into a plurality of grid areas; a three-dimensional CAD model of a part is subjected to layered slicing so as to obtain a contour of each layer, and grids where the contours of all the layers are located and grids contained in the contours of all the layers are selected to serve as preheating scanning grid areas which each comprise the first grid, the second grid. the N grid which are sequentially adjacent from the outer edges of the contours to the interiors; the outer edge end points of the first grid, the second grid. the N grid in the preheating scanning grid area of the contour of the first layer are sequentially selected to serve as starting points, and electron beam preheating scanning is conducted in the X and Y directions simultaneously; and preheating scanning of the contour of the second layer is continued till preheating scanning of the contour of each layer is completed.

However, in a conventional three-dimensional PBF-AM apparatus, a preheating pattern in which lines of an electron beam with which a powder layer is irradiated overlap each other is adopted, and the powder layer is preheated by irradiating the powder layer with the electron beam according to the preheating pattern. For this reason, electric charges are likely to be accumulated in the powder particles at the time of preheating, and the risk of occurrence of smoke is high. In addition, if a preheating pattern is adopted in which the lines of the electron beam do not overlap each other, the metal powder is locally heated, and thus the temperature of the powder layer becomes uneven.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a technique capable of reducing a risk of occurrence of smoke and making a temperature distribution of a powder layer uniform.

A three-dimensional PBF-AM apparatus according to the present invention includes a build plate, a powder application apparatus that applies metal powder onto the build plate to form a powder layer, a beam irradiation apparatus that irradiates the powder layer with an electron beam, and a control unit that controls the powder application apparatus and the beam irradiation apparatus. When the powder layer is preheated by irradiation with the electron beam, the control unit sets a beam size and an irradiation position of the electron beam such that lines of the electron beam do not overlap each other at least at a start of preheating, and controls the beam irradiation apparatus to gradually increase the beam size of the electron beam from the start of preheating to an end of preheating.

A three-dimensional PBF-AM method according to the present invention includes, when a powder layer formed by applying metal powder onto a build plate is preheated by irradiation with an electron beam, setting a beam size and an irradiation position of the electron beam such that lines of the electron beam do not overlap each other at least at a start of preheating, and controlling the electron beam to gradually increase the beam size of the electron beam from the start of preheating to an end of preheating.

According to the present invention, the risk of occurrence of smoke can be reduced, and the temperature distribution of the powder layer can be made uniform.

Embodiments of the present invention will be hereinafter described in detail with reference to the drawings. In the present specification and the drawings, elements having substantially the same function or configuration are denoted by the same reference numerals, and redundant description is omitted.

<FIG> is a side view schematically illustrating a configuration of a three-dimensional PBF-AM apparatus according to a first embodiment of the present invention. In the following description, in order to clarify the shape, positional relationship, and the like of each part of the three-dimensional PBF-AM apparatus, the horizontal direction in <FIG> is referred to as an X direction, the depth direction in <FIG> is referred to as a Y direction, and the vertical direction in <FIG> is referred to as a Z direction. The X direction, the Y direction, and the Z direction are directions orthogonal to one another. The X direction and the Y direction are parallel to the horizontal direction, and the Z direction is parallel to the vertical direction.

As illustrated in <FIG>, a three-dimensional PBF-AM apparatus <NUM> includes a vacuum chamber <NUM>, a beam irradiation apparatus <NUM>, a powder application apparatus <NUM>, a build table <NUM>, a build box <NUM>, a recovery box <NUM>, a build plate <NUM>, an inner base <NUM>, and a plate moving apparatus <NUM>.

The vacuum chamber <NUM> is a chamber for creating a vacuum state by evacuating air from the chamber by a vacuum pump (not illustrated).

The beam irradiation apparatus <NUM> is an apparatus that emits an electron beam <NUM> which is one of charged particle beams. The beam irradiation apparatus <NUM> includes an electron gun <NUM> that is a generation source of the electron beam <NUM>, a focusing lens <NUM> that focuses the electron beam <NUM> generated by the electron gun <NUM>, and a deflection lens <NUM> that deflects the electron beam <NUM> focused by the focusing lens <NUM>.

The focusing lens <NUM> is configured using a focusing coil, and focuses the electron beam <NUM> by a magnetic field generated by the focusing coil. In addition, the deflection lens <NUM> is configured using a deflection coil, and deflects the electron beam <NUM> by a magnetic field generated by the deflection coil.

The powder application apparatus <NUM> is an apparatus that applies metal powder <NUM>, which is a raw material of a build object <NUM>, onto the build plate <NUM> to form a powder layer 32a. The powder application apparatus <NUM> includes a hopper 16a, a powder dropping device 16b, and a squeegee 16c. The hopper 16a is a chamber for storing metal powder. The powder dropping device 16b is a device that drops the metal powder stored in the hopper 16a onto the build table <NUM>. The squeegee 16c moves in the horizontal direction on the build plate <NUM> to spread the metal powder <NUM>. The squeegee 16c is an elongated member elongated in the Y direction. The squeegee 16c is provided to be movable in the X direction in order to spread the metal powder <NUM> over the entire surface of the build table <NUM>.

The build table <NUM> is horizontally arranged inside the vacuum chamber <NUM>. The build table <NUM> is arranged below the powder application apparatus <NUM>. A central portion of the build table <NUM> is opened. The opening shape of the build table <NUM> is a circular shape in plan view or a square shape in plan view (for example, a quadrangle in plan view).

The build box <NUM> is a box that forms a space for building. An upper end portion of the build box <NUM> is connected to an opening edge of the build table <NUM>. A lower end portion of the build box <NUM> is connected to a bottom wall of the vacuum chamber <NUM>.

The recovery box <NUM> is a box that recovers the metal powder <NUM> supplied more than necessary from the metal powder <NUM> supplied onto the build table <NUM> by the powder application apparatus <NUM>. One recovery box <NUM> is provided on each of one side and the other side in the X direction.

The build plate <NUM> is a plate for forming the build object <NUM> using the metal powder <NUM>. The build object <NUM> is layered and formed on the build plate <NUM>. The build plate <NUM> is formed in a circular shape in plan view or a square shape in plan view in accordance with the opening shape of the build table <NUM>. The build plate <NUM> is connected (grounded) to the inner base <NUM> via a ground wire <NUM> so as not to be in an electrically floating state. The inner base <NUM> is held at a ground (GND) potential. The metal powder <NUM> is spread over the build plate <NUM> and the inner base <NUM>.

The inner base <NUM> is provided to be movable in the vertical direction (Z direction). The build plate <NUM> moves in the vertical direction integrally with the inner base <NUM>. The inner base <NUM> has a larger outer dimension than that of the build plate <NUM>. The inner base <NUM> slides in the vertical direction along an inner surface of the build box <NUM>. A seal member <NUM> is attached to an outer peripheral portion of the inner base <NUM>. The seal member <NUM> is a member that maintains slidability and sealability between the outer peripheral portion of the inner base <NUM> and the inner surface of the build box <NUM>. The seal member <NUM> is made of a material having heat resistance and elasticity.

The plate moving apparatus <NUM> is an apparatus that moves the build plate <NUM> and the inner base <NUM> in the vertical direction. The plate moving apparatus <NUM> includes a shaft 26a and a drive mechanism unit 26b. The shaft 26a is connected to a lower surface of the inner base <NUM>. The drive mechanism unit 26b includes a motor and a power transmission mechanism (not illustrated), and drives the power transmission mechanism using the motor as a drive source to move the build plate <NUM> and the inner base <NUM> integrally with the shaft 26a in the vertical direction. The power transmission mechanism includes, for example, a rack and pinion mechanism, a ball screw mechanism, or the like.

A radiation shield cover <NUM> is arranged between the build plate <NUM> and the beam irradiation apparatus <NUM> in the Z direction. The radiation shield cover <NUM> is made of metal such as stainless steel or the like. The radiation shield cover <NUM> contains radiation heat generated when the metal powder <NUM> is irradiated with the electron beam <NUM> by the beam irradiation apparatus <NUM>.

In addition, the radiation shield cover <NUM> serves a function of suppressing adhesion (vapor deposition) of an evaporated substance generated when the metal powder <NUM> is irradiated with the electron beam <NUM> to an inner wall of the vacuum chamber <NUM>. When the metal powder <NUM> is irradiated with the electron beam <NUM>, a part of the melted metal becomes an atomized evaporated substance and rises from a build surface 32b. The radiation shield cover <NUM> is arranged so as to cover a space above the build surface 32b so that the evaporated substance does not diffuse into the vacuum chamber <NUM>.

An electron shield <NUM> has an opening 30a and a shield portion 30b. In forming the build object <NUM>, the electron shield <NUM> is arranged to cover an upper surface of the metal powder <NUM>, that is, the build surface 32b. At this time, the opening 30a exposes the metal powder <NUM> spread on the build plate <NUM>, and the shield portion 30b shields the metal powder <NUM> located outside the opening 30a. The shape of the opening 30a is set in accordance with the shape of the build plate <NUM>. For example, if the build plate <NUM> is circular in plan view, the shape in plan view of the opening 30a is set to be circular accordingly, and if the build plate <NUM> is angular in plan view, the shape in plan view of the opening 30a is set to be angular accordingly. In the present embodiment, as an example, it is assumed that the opening 30a has a quadrangular shape in plan view.

The electron shield <NUM> is arranged below the radiation shield cover <NUM>. The opening 30a and the shield portion 30b of the electron shield <NUM> are arranged between the build plate <NUM> and the radiation shield cover <NUM> in the Z direction. The electron shield <NUM> includes an enclosure portion 30c. The enclosure portion 30c is arranged so as to surround the space above the opening 30a. A part (upper portion) of the enclosure portion 30c overlaps the radiation shield cover <NUM> in the Z direction. The enclosure portion 30c has a function of containing radiant heat generated from the build surface 32b and a function of suppressing diffusion of the evaporated substance generated from the build surface 32b. That is, the enclosure portion 30c has the same function as that of the radiation shield cover <NUM>.

<FIG> is a block diagram illustrating a configuration example of a control system of the three-dimensional PBF-AM apparatus according to the first embodiment of the present invention.

In <FIG>, a control unit <NUM> includes, for example, a central processing unit (CPU) 50a, a read only memory (ROM) 50b, and a random access memory (RAM) 50c, and the CPU 50a reads a program written in the ROM 50b into the RAM 50c and executes predetermined control processing, thereby integrally controlling the operation of the three-dimensional PBF-AM apparatus <NUM>. In addition to the beam irradiation apparatus <NUM>, the powder application apparatus <NUM>, and the plate moving apparatus <NUM> described above, an electron shield lifting apparatus <NUM> is connected to the control unit <NUM>.

The beam irradiation apparatus <NUM> emits the electron beam <NUM> on the basis of a control command given from the control unit <NUM>. At that time, the control unit <NUM> controls the electron beam <NUM> via the electron gun <NUM>, the focusing lens <NUM>, and the deflection lens <NUM>. For example, the control unit <NUM> controls the beam current of the electron beam <NUM> via the electron gun <NUM>. In addition, the control unit <NUM> controls the focus state of the electron beam <NUM> via the focusing lens <NUM>. In addition, the control unit <NUM> controls the deflection angle and the deflection speed of the electron beam <NUM> via the deflection lens <NUM>.

Note that the spot diameter of the electron beam <NUM> on a horizontal plane (XY plane) changes according to the focus state of the electron beam <NUM>. Therefore, controlling the focus state of the electron beam <NUM> means controlling the spot diameter of the electron beam <NUM> with which an object is irradiated. In addition, an irradiation position of the electron beam <NUM> on the horizontal plane changes according to the deflection angle of the electron beam <NUM>. Therefore, controlling the deflection angle of the electron beam <NUM> means controlling the irradiation position of the electron beam <NUM>.

The plate moving apparatus <NUM> moves the build plate <NUM> on the basis of a control command given from the control unit <NUM>. The powder application apparatus <NUM> applies the metal powder <NUM> onto the build plate <NUM> on the basis of a control command given from the control unit <NUM>. The operations of the hopper 16a, the powder dropping device 16b, and the squeegee 16c included in the powder application apparatus <NUM> are controlled by the control unit <NUM>. The electron shield lifting apparatus <NUM> moves up and down the electron shield <NUM> on the basis of a control command given from the control unit <NUM>.

<FIG> is a flowchart illustrating a procedure of a processing operation of the three-dimensional PBF-AM apparatus according to the first embodiment of the present invention. The processing operation illustrated in this flowchart is performed under the control of the control unit <NUM>.

First, in a state before starting the building, three sides of the build plate <NUM> are covered with the metal powder <NUM> except for an upper surface of the build plate <NUM>. Furthermore, the upper surface of the build plate <NUM> is arranged at substantially the same height as the upper surface of the metal powder <NUM> spread on the build table <NUM>. On the other hand, the electron shield <NUM> is lowered to the upper surface of the build plate <NUM>. In this case, the metal powder <NUM> present around the build plate <NUM> is in a state of being covered by the shield portion 30b of the electron shield <NUM>. The shield portion 30b is in a state of contacting the metal powder <NUM>. The building is started under the state described above.

First, the beam irradiation apparatus <NUM> heats the build plate <NUM> by operating on the basis of a control command given from the control unit <NUM> (step S1).

In step S1, the beam irradiation apparatus <NUM> irradiates the build plate <NUM> with the electron beam <NUM> through the opening 30a of the electron shield <NUM>. Thus, the build plate <NUM> is heated to a temperature at which the metal powder <NUM> is temporarily sintered.

Next, the plate moving apparatus <NUM> lowers the build plate <NUM> by a predetermined amount by operating on the basis of a control command given from the control unit <NUM> (step S2).

In step S2, the plate moving apparatus <NUM> lowers the inner base <NUM> by a predetermined amount so that the upper surface of the build plate <NUM> is slightly lower than the upper surface of the metal powder <NUM> spread on the build table <NUM>. At this time, the build plate <NUM> descends by a predetermined amount together with the inner base <NUM>. The predetermined amount (hereinafter also referred to as "ΔZ") described here corresponds to the thickness of one layer when the build object <NUM> is built by layering.

Next, the electron shield lifting apparatus <NUM> raises the electron shield <NUM> by operating on the basis of a control command given from the control unit <NUM> (step S3).

In step S3, the electron shield lifting apparatus <NUM> raises the electron shield <NUM> to a position higher than the squeegee 16c so that the squeegee 16c does not come into contact with the electron shield <NUM> in the next step S4.

Next, the powder application apparatus <NUM> applies the metal powder <NUM> onto the build plate <NUM> to form the powder layer 32a by operating on the basis of a control command given from the control unit <NUM> (step S4).

In step S4, the powder application apparatus <NUM> drops the metal powder <NUM> supplied from the hopper 16a to the powder dropping device 16b onto the build table <NUM> by the powder dropping device 16b, and then moves the squeegee 16c in the X direction to spread the metal powder <NUM> on the build plate <NUM>. At this time, the metal powder <NUM> is spread on the build plate <NUM> with a thickness corresponding to ΔZ. Thus, the powder layer 32a is formed on the build plate <NUM>. The excess metal powder <NUM> is recovered in the recovery box <NUM>.

Next, the electron shield lifting apparatus <NUM> lowers the electron shield <NUM> by operating on the basis of a control command given from the control unit <NUM> (step S5).

In step S5, the electron shield lifting apparatus <NUM> lowers the electron shield <NUM> so as to come into contact with the build surface 32b of the metal powder <NUM>. Thus, the metal powder <NUM> on the build plate <NUM> is exposed to the outside through the opening 30a of the electron shield <NUM>. In addition, the metal powder <NUM> present around the build plate <NUM> is in the state of being covered by the shield portion 30b of the electron shield <NUM>.

Next, the beam irradiation apparatus <NUM> preheats the powder layer 32a on the build plate <NUM> by operating on the basis of a control command given from the control unit <NUM> (step S6). In the preheating step S6, the powder layer 32a is preheated in order to temporarily sinter the metal powder <NUM>. The preheating performed before a sintering step is also called powder-heat.

In step S6, the beam irradiation apparatus <NUM> irradiates the metal powder <NUM> (powder layer 32a) on the build plate <NUM> with the electron beam <NUM>. Furthermore, the beam irradiation apparatus <NUM> irradiates a region wider than a region for forming the build object <NUM> (hereinafter also referred to as a "build region") with the electron beam <NUM>. Thus, the metal powder <NUM> present in the build region and the metal powder <NUM> present around the build region are both temporarily sintered.

In <FIG>, reference numeral E1 denotes an unsintered region where the unsintered metal powder <NUM> is present, and reference numeral E2 denotes a temporarily sintered region where the temporarily sintered metal powder <NUM> is present.

Next, the beam irradiation apparatus <NUM> sinters the metal powder <NUM> by melting and solidifying, by operating on the basis of a control command given from the control unit <NUM> (step S7).

In step S7, the metal powder <NUM> as a temporarily sintered body is sintered by melting and solidifying the metal powder <NUM> temporarily sintered as described above by irradiation with the electron beam <NUM>. In step S7, the control unit <NUM> specifies a build region on the basis of two-dimensional data obtained by slicing three-dimensional computer-aided design (CAD) data of the target build object <NUM> to a certain thickness (thickness corresponding to ΔZ), and the beam irradiation apparatus <NUM> selectively melts the metal powder <NUM> on the build plate <NUM> by irradiating the build region specified by the control unit <NUM> with the electron beam <NUM>. The metal powder <NUM> melted by the irradiation with the electron beam <NUM> is solidified after the electron beam <NUM> passes. Thus, a first layer of the build object is formed.

Next, the plate moving apparatus <NUM> lowers the build plate <NUM> by a predetermined amount (ΔZ) by operating on the basis of a control command given from the control unit <NUM> (step S8).

In step S8, the plate moving apparatus <NUM> lowers the build plate <NUM> and the inner base <NUM> by ΔZ.

Subsequently, the beam irradiation apparatus <NUM> preheats the powder layer 32a on the build plate <NUM> by operating on the basis of a control command given from the control unit <NUM> (step S9). In the first preheating step S9, as a preparation for spreading the metal powder <NUM> in the next layer, the powder layer 32a that has been subjected to the sintering step in the previous layer is preheated. The preheating performed after the sintering step is also called after-heat.

In step S9, the beam irradiation apparatus <NUM> irradiates the powder layer 32a with the electron beam <NUM> through the opening 30a of the electron shield <NUM>. Thus, the powder layer 32a exposed to the opening 30a is heated to a temperature at which the metal powder <NUM> is temporarily sintered.

Next, the electron shield lifting apparatus <NUM> raises the electron shield <NUM> by operating on the basis of a control command given from the control unit <NUM> (step S10).

In step S10, the electron shield lifting apparatus <NUM> raises the electron shield <NUM> to a position higher than the squeegee 16c so that the squeegee 16c does not come into contact with the electron shield <NUM> in the next step S11.

Next, the powder application apparatus <NUM> applies the metal powder <NUM> onto the build plate <NUM> to form the powder layer 32a by operating on the basis of a control command given from the control unit <NUM> (step S11).

In step S11, the powder application apparatus <NUM> operates similarly as in step S4 described above. Thus, on the build plate <NUM>, a second layer of the metal powder <NUM> is spread over the sintered body formed by a first layer of the metal powder <NUM>.

Next, the electron shield lifting apparatus <NUM> lowers the electron shield <NUM> by operating on the basis of a control command given from the control unit <NUM> (step S12).

In step S12, the electron shield lifting apparatus <NUM> operates similarly as in step S5 described above.

Next, the beam irradiation apparatus <NUM> preheats the metal powder <NUM> forming a second layer of the powder layer 32a by operating on the basis of a control command given from the control unit <NUM> (step S13).

In step S13, the beam irradiation apparatus <NUM> operates similarly as in step S6 described above. Thus, the metal powder <NUM> forming the second layer of the powder layer 32a is temporarily sintered.

Next, the beam irradiation apparatus <NUM> sinters the metal powder <NUM> forming the second layer of the powder layer 32a by melting and solidifying, by operating on the basis of a control command given from the control unit <NUM> (step S14).

In step S14, the beam irradiation apparatus <NUM> operates similarly as in step S7 described above. Thus, a second layer of the build object is formed.

Next, the control unit <NUM> confirms whether or not the building of the target build object <NUM> is completed (step S15). When the control unit <NUM> determines that the building of the build object <NUM> is not completed, the process returns to Step S8 described above. In this way, the control unit <NUM> repeats the processes of steps S8 to S14 for each of the third and subsequent layers. When it is determined that the building of the build object <NUM> is completed, the series of processing is ended at that time.

By the three-dimensional PBF-AM process described above, the target build object <NUM> is obtained.

In steps S6 and S13 in the three-dimensional PBF-AM process described above, the powder layer 32a is preheated by irradiation with the electron beam <NUM> in order to temporarily sinter the metal powder <NUM>. At that time, the control unit <NUM> sets a beam diameter and irradiation positions of the electron beam <NUM> such that spots of the electron beam <NUM> do not overlap at least at a start of preheating. In addition, the control unit <NUM> controls the beam irradiation apparatus <NUM> to gradually increase the beam diameter of the electron beam <NUM> from the start of preheating to an end of preheating.

A method of preheating a powder layer according to the first embodiment of the present invention will be hereinafter described with reference to the drawings.

When the powder layer 32a for one layer is preheated by irradiation with the electron beam <NUM>, the control unit <NUM> preheats the powder layer 32a in a plurality of stages having different irradiation conditions with the electron beam <NUM>. The number of stages for preheating the powder layer 32a can be optionally set, and other embodiments described later can also be optionally set as such. In the present embodiment, as an example, the powder layer 32a is preheated in four stages.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a first stage according to the first embodiment of the present invention. A start of the first stage corresponds to the start of preheating.

In <FIG>, the powder layer 32a of the metal powder <NUM> exposed to the outside through the opening 30a of the electron shield <NUM> is irradiated with the electron beam <NUM>. When the powder layer 32a is irradiated with the electron beam <NUM>, a spot (hereinafter also referred to as a "beam spot") 15a of the electron beam <NUM> is formed at an irradiation position of the electron beam <NUM>. Therefore, the position of the beam spot 15a indicates the irradiation position of the electron beam <NUM>. The control unit <NUM> moves the irradiation position of the electron beam <NUM> according to a predetermined preheating pattern. The preheating pattern is a dotted (stepping stone) pattern illustrated in <FIG>.

Specifically, the control unit <NUM> divides irradiation positions of the electron beam <NUM> into a plurality of lines Li in the Y direction (second direction), and moves the irradiation position of the electron beam <NUM> from one end to the other end in the X direction (first direction) for each line Li. In addition, the control unit <NUM> intermittently moves the irradiation position of the electron beam <NUM> in the X direction by repeating movement and stop of the electron beam <NUM> in each line Li. At this time, a position where the electron beam <NUM> stops is an irradiation position of the electron beam <NUM>, that is, a position where the beam spot 15a is formed. In the first stage illustrated in <FIG>, the control unit <NUM> sets the beam diameter and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> do not overlap each other. More specifically, an interval Px between the beam spots 15a in the X direction and an interval Py between the beam spots 15a in the Y direction are both set to be equal to or larger than the beam diameter (φ1 illustrated in <FIG>) of the electron beam <NUM> so that the beam spots 15a do not overlap each other in the X direction or the Y direction. As a result, the interval Py necessary for avoiding overlapping of the lines Li is secured between the two lines Li adjacent to each other in the Y direction. Each line Li of the electron beam <NUM> is a line formed by moving the irradiation position of the electron beam <NUM> in the X direction, and a width of one line Li has the same dimension as the beam diameter of the electron beam <NUM>. The beam diameter of the electron beam <NUM> corresponds to the beam size of the electron beam <NUM>, and means the diameter of the spot of the electron beam <NUM> with which the powder layer 32a is irradiated.

The control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position of the electron beam <NUM> from a start point Ps to an end point Pe according to the preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. As a result, in a case where a prescribed value of the number of repetitions of the moving operation is set to, for example, K times (K is an integer of <NUM> or larger), the first stage ends when the number of repetitions of the moving operation reaches K times. Therefore, in the first stage, each irradiation position of the electron beam <NUM> is irradiated K times with the electron beam <NUM> with a size of the beam diameter φ1. In the present embodiment, an irradiation region of the electron beam <NUM> is a quadrangular region, but the present invention is not limited thereto, and the irradiation region of the electron beam <NUM> may be a circular region. In the embodiment described later, the region may be a circular region as described above.

<FIG> is a view schematically illustrating irradiation positions of an electron beam in a second stage according to the first embodiment of the present invention. The second stage is a stage subsequent to the first stage.

In the second stage, the control unit <NUM> sets the beam diameter of the electron beam <NUM> to φ2 larger than φ1 described above in comparison with the first stage. Then, under the setting of the beam diameter = φ2, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. The number of repetitions of the moving operation may be the same as or different from that in the first stage. In the second stage illustrated in <FIG>, the control unit <NUM> sets the beam diameter and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> do not overlap each other. More specifically, the interval Px between the beam spots 15a in the X direction and the interval Py between the beam spots 15a in the Y direction are both set to be equal to or larger than the beam diameter φ2 of the electron beam <NUM> so that the beam spots 15a do not overlap each other in the X direction or the Y direction. Furthermore, the intervals Px and Py between the beam spots 15a are set to be the same as those in the case of the first stage.

<FIG> is a view schematically illustrating irradiation positions of an electron beam in a third stage according to the first embodiment of the present invention. The third stage is a stage subsequent to the second stage.

In the third stage, the control unit <NUM> sets the beam diameter of the electron beam <NUM> to φ3 larger than φ2 described above in comparison with the second stage. Then, under the setting of the beam diameter = φ3, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. The number of repetitions of the moving operation may be the same as or different from that in the first stage. In the third stage illustrated in <FIG>, the control unit <NUM> sets the beam diameter and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> do not overlap each other. More specifically, the interval Px between the beam spots 15a in the X direction and the interval Py between the beam spots 15a in the Y direction are both set to be equal to or larger than the beam diameter φ3 of the electron beam <NUM> so that the beam spots 15a do not overlap each other in the X direction or the Y direction. Furthermore, the intervals Px and Py between the beam spots 15a are set to be the same as those in the case of the first stage.

<FIG> is a view schematically illustrating irradiation positions of an electron beam in a fourth stage according to the first embodiment of the present invention. The fourth stage is a stage subsequent to the third stage. The end of the fourth stage corresponds to the end of preheating.

In the fourth stage, the control unit <NUM> sets the beam diameter of the electron beam <NUM> to φ4 larger than φ3 described above in comparison with the third stage. Then, under the setting of the beam diameter = φ4, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. The number of repetitions of the moving operation may be the same as or different from that in the first stage. In the fourth stage illustrated in <FIG>, the control unit <NUM> sets the beam diameter and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> overlap each other. More specifically, the interval Px between the beam spots 15a in the X direction and the interval Py between the beam spots 15a in the Y direction are both set to be smaller than the beam diameter φ4 of the electron beam <NUM> so that the beam spots 15a overlap each other in the X direction and the Y direction. As a result, the two lines Li adjacent to each other in the Y direction partially overlap each other. Furthermore, the intervals Px and Py between the beam spots 15a are set to be the same as those in the case of the first stage. That is, the intervals Px and Py between the beam spots 15a are constant from the start of preheating to the end of preheating.

When the beam diameter is gradually increased, the area of the beam spots 15a spreading out of the opening 30a is increased. However, since the outside of the opening 30a is covered with the shield portion 30b (see <FIG>), even if the beam spots 15a spread out of the opening 30a, smoke does not occur.

As described above, in the first embodiment of the present invention, the control unit <NUM> sets the beam diameter and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> do not overlap each other in the first stage including the start of preheating and the subsequent second and third stages. This makes it possible to increase the temperature of the powder layer 32a while suppressing the occurrence of smoke. In addition, the control unit <NUM> controls the beam irradiation apparatus <NUM> to gradually increase the beam diameter of the electron beam <NUM> from the start of preheating in the first stage to the end of preheating in the fourth stage. As a result, the preheating in the fourth stage can be performed in a state where the temporary sintering of the powder layer 32a has progressed to some extent by the preheating from the first stage to the third stage. Therefore, even if the electron beam <NUM> is emitted such that the lines Li of the electron beam <NUM> overlap each other in the fourth stage, the occurrence of smoke can be suppressed. In addition, by setting the beam diameter of the electron beam <NUM> to be large as φ4 in the final fourth stage, the powder layer 32a can be heated to a uniform temperature. As a result, the risk of occurrence of smoke can be reduced, and the temperature distribution of the powder layer 32a can be made uniform.

The second embodiment of the present invention is different from the first embodiment described above in a method of preheating the powder layer 32a under the control of the control unit <NUM>. Specifically, in each of the first stage, the second stage, the third stage, and the fourth stage described above, the control unit <NUM> controls the beam irradiation apparatus <NUM> to gradually increase the beam current of the electron beam <NUM>.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a first stage according to the second embodiment of the present invention.

In the first stage illustrated in <FIG>, the setting of the beam diameter φ1 and the irradiation positions of the electron beam <NUM> and the setting of the intervals Px and Py between the beam spots 15a are the same as those in the case of the first embodiment (see <FIG>).

In this first stage, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position (beam spot 15a) of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. In addition, in a case where the moving operation in the first stage is repeated, for example, <NUM> times in total, the control unit <NUM> sets the beam current of the electron beam <NUM> to <NUM> mA in the first to 25th moving operations, sets the beam current to <NUM> mA in the 26th to 50th moving operations, sets the beam current to <NUM> mA in the 51st to 75th moving operations, and sets the beam current to <NUM> mA in the 75th to 100th moving operations. That is, the control unit <NUM> gradually increases the beam current from the start to the end of the first stage.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a second stage according to the second embodiment of the present invention.

In the second stage illustrated in <FIG>, the setting of the beam diameter φ2 and the irradiation positions of the electron beam <NUM> and the setting of the intervals Px and Py between the beam spots 15a are the same as those in the case of the first embodiment (see <FIG>).

In this second stage, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position (beam spot 15a) of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. In addition, in a case where the moving operation in the second stage is repeated, for example, <NUM> times in total, the control unit <NUM> sets the beam current of the electron beam <NUM> to <NUM> mA in the first to 25th moving operations, sets the beam current to <NUM> mA in the 26th to 50th moving operations, sets the beam current to <NUM> mA in the 51st to 75th moving operations, and sets the beam current to <NUM> mA in the 75th to 100th moving operations. That is, the control unit <NUM> gradually increases the beam current from the start to the end of the second stage.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a third stage according to the second embodiment of the present invention.

In the third stage illustrated in <FIG>, the setting of the beam diameter φ3 and the irradiation positions of the electron beam <NUM> and the setting of the intervals Px and Py between the beam spots 15a are the same as those in the case of the first embodiment (see <FIG>).

In this third stage, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position (beam spot 15a) of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. In addition, in a case where the moving operation in the third stage is repeated, for example, <NUM> times in total, the control unit <NUM> sets the beam current of the electron beam <NUM> to <NUM> mA in the first to 25th moving operations, sets the beam current to <NUM> mA in the 26th to 50th moving operations, sets the beam current to <NUM> mA in the 51st to 75th moving operations, and sets the beam current to <NUM> mA in the 75th to 100th moving operations. That is, the control unit <NUM> gradually increases the beam current from the start to the end of the third stage.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a fourth stage according to the second embodiment of the present invention.

In the fourth stage illustrated in <FIG>, the setting of the beam diameter φ4 and the irradiation positions of the electron beam <NUM> and the setting of the intervals Px and Py between the beam spots 15a are the same as those in the case of the first embodiment (see <FIG>).

In this fourth stage, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position (beam spot 15a) of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. In addition, in a case where the moving operation in the fourth stage is repeated, for example, <NUM> times in total, the control unit <NUM> sets the beam current of the electron beam <NUM> to <NUM> mA in the first to 25th moving operations, sets the beam current to <NUM> mA in the 26th to 50th moving operations, sets the beam current to <NUM> mA in the 51st to 75th moving operations, and sets the beam current to <NUM> mA in the 75th to 100th moving operations. That is, the control unit <NUM> gradually increases the beam current from the start to the end of the fourth stage.

In each of the first stage to the fourth stage, the number of repetitions of the moving operation can be optionally changed. In addition, the condition for proceeding to the next stage is not limited to the number of repetitions of the moving operation, and may be determined by time, for example, such that the process proceeds to the second stage after the first stage is performed for a predetermined time. In other embodiments to be described later, it may be determined by time as described above. In addition, the value of the beam current applied to each stage is merely an example, and is not limited to this example.

In the second embodiment of the present invention, in addition to the same effects as those of the first embodiment described above, the following effects can be obtained.

The control unit <NUM> controls the beam irradiation apparatus <NUM> to gradually increase not only the beam diameter of the electron beam <NUM> but also the beam current of the electron beam <NUM> in each stage from the start of preheating in the first stage to the end of preheating in the fourth stage. As a result, the risk of smoke generation in each stage can be reduced as compared with a case where the beam current of the electron beam <NUM> is controlled to be constant from the start of preheating to the end of preheating.

In the second embodiment, the beam current of the electron beam <NUM> is controlled to gradually increase in each stage from the first stage to the fourth stage, but the present invention is not limited thereto. For example, the beam current may be controlled to be constant in each stage, and the beam current may be controlled to increase at the timing when the stage of preheating is switched. In the second embodiment, the beam current of the electron beam <NUM> is controlled to gradually increase in all stages from the first stage to the fourth stage, but the present invention is not limited thereto, and the beam current of the electron beam <NUM> may be controlled to gradually increase in at least one of the stages. That is, the method of controlling the beam current of the electron beam <NUM> to increase can be variously modified.

Next, a third embodiment outside of the scope of the claims will be described.

The third embodiment outside of the scope of the claims is different from the first embodiment and the second embodiment described above in that the beam current of the electron beam <NUM> is gradually increased without changing the beam diameter of the electron beam <NUM>. In the first embodiment and the second embodiment described above, the preheating of the powder layer 32a is performed in four stages, but the third embodiment of the present invention is different in that the preheating of the powder layer 32a is performed in two stages.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a first stage according to the third embodiment outside of the scope of the claims.

In the first stage illustrated in <FIG>, the setting of the beam diameter φ3 and the irradiation positions of the electron beam <NUM> and the setting of the intervals Px and Py between the beam spots 15a are the same as those in the third stage of the first embodiment (see <FIG>) and the third stage of the second embodiment (see <FIG>).

In this first stage, while maintaining the beam diameter φ3 of the electron beam <NUM> constant, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position (beam spot 15a) of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. In addition, in a case where the moving operation is repeated, for example, <NUM> times in total, the control unit <NUM> sets the beam current of the electron beam <NUM> to <NUM> mA in the first to 20th moving operations, sets the beam current to <NUM> mA in the 21st to 40th moving operations, sets the beam current to <NUM> mA in the 41st to 60th moving operations, sets the beam current to <NUM> mA in the 61st to 80th moving operations, and sets the beam current to <NUM> mA in the 81st to 100th moving operations. That is, the control unit <NUM> gradually increases the beam current from the start to the end of the first stage.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a second stage according to the third embodiment outside of the scope of the claims.

In the second stage illustrated in <FIG>, the control unit <NUM> sets the interval between the beam spots 15a to be narrow without changing the beam diameter φ3 of the electron beam <NUM> as compared with the first stage illustrated in <FIG> so that the lines Li of the electron beam <NUM> overlap each other. Specifically, the control unit <NUM> sets intervals Px1 and Py1 between the beam spots 15a to be smaller than the beam diameter φ3 so that the beam spots 15a overlap each other in both the X direction and the Y direction.

In this second stage, while maintaining the beam diameter φ3 of the electron beam <NUM> constant, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position (beam spot 15a) of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. In addition, the control unit <NUM> gradually increases the beam current from the start to the end of the second stage in the same control mode as that in the first stage.

In the second stage, since the intervals Px1 and Py1 between the beam spots 15a are set narrower than those in the first stage, movement and stop of the electron beam <NUM> are repeated more times until the irradiation position of the electron beam <NUM> is moved from the start point Ps to the end point Pe. Therefore, the interval between the two lines Li adjacent to each other in the Y direction is narrowed, and the number of lines Li is increased. In addition, the arrangement of the beam spots 15a indicating the irradiation positions of the electron beam <NUM> is denser than that in the first stage.

As described above, in the third embodiment outside of the scope of the claims, in the first stage and the second stage, since the beam current of the electron beam <NUM> is gradually increased without changing the beam diameter of the electron beam <NUM>, the temperature of the powder layer 32a can be increased while suppressing the occurrence of smoke. In addition, in the second stage, since the interval Py1 between the beam spots 15a is set to be narrow so that the lines Li of the electron beam <NUM> overlap each other, the powder layer 32a can be heated to a uniform temperature. Furthermore, in the second stage, since the intervals Px1 and Py1 between the beam spots 15a are set to be narrow so that the beam spots 15a overlap each other in both the X direction and the Y direction, the powder layer 32a can be heated to a more uniform temperature.

In the third embodiment, by setting the intervals Px1 and Py1 between the beam spots 15a applied in the second stage narrower than the intervals Px and Py between the beam spots 15a applied in the first stage, in the second stage, the lines Li of the electron beam <NUM> overlap each other and the beam spots 15a overlap each other with the same beam diameter φ3 as that in the first stage. Such a method is also applicable to the first embodiment and the second embodiment. For example, in the second embodiment, the beam diameter φ4 of the electron beam <NUM> is set to be large in order to overlap the lines Li of the electron beam <NUM> each other and the beam spots 15a each other in the fourth stage. However, in addition to this, in the fourth stage, as illustrated in <FIG>, the beam diameter φ3 of the electron beam <NUM> is set to be the same as that in the third stage, and the intervals Px1 and Py1 between the beam spots 15a are set to be narrower than those in the third stage, so that the lines Li of the electron beam <NUM> can overlap each other and the beam spots 15a can overlap each other. The same applies to the first embodiment.

Next, a fourth embodiment of the present invention will be described.

In the fourth embodiment of the present invention, with respect to a first powder layer 32a and a second powder layer 32a layered at different positions in a layering direction, the control unit <NUM> sets an irradiation position of the electron beam <NUM> applied when the first powder layer 32a is preheated and an irradiation position of the electron beam <NUM> applied when the second powder layer 32a is preheated, to be shifted in a direction orthogonal to the layering direction. The layering direction is a direction in which the powder layers 32a are layered for building the three-dimensional build object <NUM>, that is, the Z direction. The direction orthogonal to the layering direction is a direction parallel to the upper surface of the build plate <NUM>, that is, the horizontal direction.

In the fourth embodiment of the present invention, a case where the first powder layer 32a is an Mth layer (M is a natural number) of the powder layer 32a and the second powder layer 32a is an M+1th layer of the powder layer 32a will be described as an example. However, the first powder layer 32a and the second powder layer 32a do not have to be adjacent to each other in the layering direction, and one or more powder layers 32a may be interposed between the first powder layer 32a and the second powder layer 32a. That is, the irradiation position of the electron beam <NUM> may be shifted for each layer or for each unit of multiple layers.

When the irradiation position of the electron beam <NUM> is shifted for each unit of multiple layers, the number of layers of the powder layer 32a interposed between the first powder layer 32a and the second powder layer 32a may be set to the number of layers suitable for dispersing a mass of temporarily sintered bodies. The mass of temporarily sintered bodies is a mass formed of hard temporarily sintered bodies each formed at the irradiation position of the electron beam <NUM> when the powder layer 32a is preheated by irradiation with the electron beam <NUM>, the temporarily sintered bodies being layered long in the layering direction. When the mass of the temporarily sintered bodies is formed, the processing time to remove the temporarily sintered bodies from the target build object <NUM> by blasting treatment becomes long.

Therefore, when the Mth layer of the powder layer 32a is preheated, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position (beam spot 15a) of the electron beam <NUM> from a start point Ps1 to an end point Pe1 according to a preheating pattern illustrated in <FIG> and to repeat this moving operation. Then, when the M+1th layer of the powder layer 32a is preheated, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position (beam spot 15a) of the electron beam <NUM> from a start point Ps2 to an end point Pe2 according to a preheating pattern illustrated in <FIG> and to repeat this moving operation.

As can be seen from a comparison between the preheating pattern illustrated in <FIG> and the preheating pattern illustrated in <FIG>, the beam irradiation positions when the M+1th layer of the powder layer 32a is preheated are shifted by a predetermined distance L in the X direction from the respective beam irradiation positions when the Mth layer of the powder layer 32a is preheated. By shifting the beam irradiation position in this manner, the position of the temporarily sintered body formed at the beam irradiation position of the Mth layer of the powder layer 32a and the position of the temporarily sintered body formed at the beam irradiation position of the M+1th layer of the powder layer 32a are shifted in the horizontal direction, so that these temporarily sintered bodies can be divided in the layering direction. As a result, it is possible to suppress formation of the mass of the temporarily sintered bodies layered long in the layering direction. Therefore, the operation of removing the temporarily sintered bodies from the target build object <NUM> by blasting treatment can be completed in a short time.

The direction in which the beam irradiation position is shifted is not limited to the X direction.

The fourth embodiment of the present invention is applied to the first embodiment and the second embodiment, described above.

Next, a fifth embodiment of the present invention will be described.

In the fifth embodiment of the present invention, when the powder layer 32a is preheated by irradiation with the electron beam <NUM>, the control unit <NUM> controls the beam irradiation apparatus <NUM> to irradiate a wider area than the opening 30a of the electron shield <NUM> with the electron beam <NUM>.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam according to the fifth embodiment of the present invention.

First, for comparison with the fifth embodiment of the present invention, the preheating pattern in the first stage of the first embodiment (see <FIG>) will be described.

In the first embodiment, the center of each beam spot 15a on the outer side as viewed from the center of the opening 30a of the electron shield <NUM> is located at the edge of the opening 30a.

On the other hand, in the fifth embodiment of the present invention, as illustrated in <FIG>, the center of each beam spot 15a on the outer side as viewed from the center of the opening 30a of the electron shield <NUM> is located outside the edge of the opening 30a, that is, in the region of the shield portion 30b (see <FIG>).

When the irradiation area of the electron beam <NUM> is enlarged in this manner, the time required for moving the irradiation position (beam spot 15a) of the electron beam <NUM> from a start point Ps3 to an end point Pe3 according to a preheating pattern illustrated in <FIG> becomes long. Therefore, when the irradiation position of the electron beam <NUM> is moved from the start point Ps3 to the end point Pe3 and this moving operation is repeated a plurality of times, the time from when the irradiation position of the electron beam <NUM> starts to move from the start point Ps3 to when it returns to the start point Ps3 again, that is, the repetition period becomes long. Therefore, when the beam irradiation position is moved from the start point Ps, which is the start point of substantial preheating, to the end point Pe, which is the end point of the substantial preheating, it is possible to secure a long time for dissipating electric charges accumulated in the powder particles at each beam irradiation position. As a result, the risk of occurrence of smoke due to accumulation of electric charges can be reduced.

In the fifth embodiment, the preheating pattern in the first stage of the first embodiment has been described as a comparative example. However, the irradiation area of the electron beam <NUM> may be enlarged similarly to the fifth embodiment even in the second and subsequent stages of the first embodiment. The fifth embodiment is applied to the second embodiment and the fourth embodiment.

Next, a sixth embodiment of the present invention will be described.

The sixth embodiment of the present invention is different from the above-described embodiments in a system of moving the electron beam <NUM> in the X direction. Specifically, in the above-described embodiments, a system is adopted in which the control unit <NUM> intermittently moves the irradiation position of the electron beam <NUM> in the X direction by repeating movement and stop of the electron beam <NUM> in each line Li. On the other hand, in the sixth embodiment, a system is adopted in which the electron beam <NUM> is moved at a constant speed without being stopped in each line Li, that is, the irradiation position of the electron beam <NUM> is continuously moved in the X direction. Details will be described below.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a first stage according to the sixth embodiment of the present invention.

In the first stage illustrated in <FIG>, the control unit <NUM> divides the irradiation positions of the electron beam <NUM> into the plurality of lines Li in the Y direction, and moves the irradiation position of the electron beam <NUM> from one end to the other end in the X direction for each line Li. In addition, the control unit <NUM> continuously moves the beam spot 15a of the electron beam <NUM> in the X direction in each line Li. Furthermore, the control unit <NUM> sets a beam width and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> do not overlap each other. More specifically, the interval Py between the beam spots 15a in the Y direction is set to be equal to or larger than the beam width (w1 illustrated in <FIG>) of each electron beam <NUM> so that the two lines Li adjacent to each other in the Y direction do not overlap each other. The beam width of the electron beam <NUM> corresponds to the beam size of the electron beam <NUM>, and is determined by the diameter of a spot (beam spot 15a illustrated in <FIG>) of the electron beam <NUM> with which the powder layer 32a is irradiated. In addition, in the first stage, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a second stage according to the sixth embodiment of the present invention.

In the second stage, the control unit <NUM> sets the beam width of the electron beam <NUM> to w2 larger than w1 described above in comparison with the first stage. Then, under the setting of the beam width = w2, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. In the second stage illustrated in <FIG>, the control unit <NUM> sets the beam width and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> do not overlap each other. More specifically, the interval Py of the beam spots 15a in the Y direction is set to be equal to or larger than the beam width (w2 illustrated in <FIG>) of each electron beam <NUM> so that the two lines Li adjacent to each other in the Y direction do not overlap each other. Furthermore, the interval Py between the beam spots 15a is set to be the same as that in the case of the first stage.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a third stage according to the sixth embodiment of the present invention.

In the third stage, the control unit <NUM> sets the beam width of the electron beam <NUM> to w3 larger than w2 described above in comparison with the second stage. Then, under the setting of the beam width = w3, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. In the third stage illustrated in <FIG>, the control unit <NUM> sets the beam width and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> do not overlap each other. More specifically, the interval Py of the beam spots 15a in the Y direction is set to be equal to or larger than the beam width (w3 illustrated in <FIG>) of each electron beam <NUM> so that the two lines Li adjacent to each other in the Y direction do not overlap each other. Furthermore, the interval Py between the beam spots 15a is set to be the same as that in the case of the first stage.

<FIG> is a plan view schematically illustrating irradiation positions of an electron beam in a fourth stage according to the sixth embodiment of the present invention.

In the fourth stage, the control unit <NUM> sets the beam width of the electron beam <NUM> to w4 larger than w3 described above in comparison with the third stage. Then, under the setting of the beam width = w4, the control unit <NUM> controls the beam irradiation apparatus <NUM> to move the irradiation position of the electron beam <NUM> from the start point Ps to the end point Pe according to a preheating pattern illustrated in <FIG> and to repeat this moving operation a predetermined number of times. In the fourth stage illustrated in <FIG>, the control unit <NUM> sets the beam width and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> overlap each other. More specifically, the interval Py of the beam spots 15a in the Y direction is set to be smaller than the beam width (w4 illustrated in <FIG>) of each electron beam <NUM>. As a result, the two lines Li adjacent to each other in the Y direction partially overlap each other. Furthermore, the interval Py between the beam spots 15a is set to be the same as that in the case of the first stage. That is, the interval Py between the beam spots 15a are constant from the start of preheating to the end of preheating.

As described above, in the sixth embodiment of the present invention, the control unit <NUM> sets the beam width and the irradiation positions of the electron beam <NUM> such that the lines Li of the electron beam <NUM> do not overlap each other in the first stage including the start of preheating and the subsequent second and third stages. This makes it possible to increase the temperature of the powder layer 32a while suppressing the occurrence of smoke. In addition, the control unit <NUM> controls the beam irradiation apparatus <NUM> to gradually increase the beam width of the electron beam <NUM> from the start of preheating in the first stage to the end of preheating in the fourth stage. As a result, the preheating in the fourth stage can be performed in a state where the temporary sintering of the powder layer 32a has progressed to some extent by the preheating from the first stage to the third stage. Therefore, even if the electron beam <NUM> is emitted such that the lines Li of the electron beam <NUM> overlap each other in the fourth stage, the occurrence of smoke can be suppressed.

In addition, by setting the beam width of the electron beam <NUM> to be large as w4 in the final fourth stage, the powder layer 32a can be heated to a uniform temperature. As a result, the risk of occurrence of smoke can be reduced, and the temperature distribution of the powder layer 32a can be made uniform.

In the sixth embodiment, the beam current of the electron beam <NUM> may be changed similarly to the second embodiment and the third embodiment described above.

In addition, in the sixth embodiment, as in the above-described fourth embodiment, an irradiation position of the electron beam <NUM> applied when the first powder layer 32a is preheated and an irradiation position of the electron beam <NUM> applied when the second powder layer 32a is preheated, may be set to be shifted in a direction orthogonal to the layering direction. However, in the sixth embodiment, since the irradiation position of the electron beam <NUM> is continuously moved in the X direction, the direction in which the beam irradiation position is shifted is limited to the Y direction.

Furthermore, in the first embodiment and the second embodiment described above, the interval Px between the beam spots 15a in the X direction and the interval Py between the beam spots 15a in the Y direction are both set to be equal to or larger than the beam diameter of the electron beam <NUM> so that the beam spots 15a do not overlap each other in the first stage including the start of preheating and the subsequent second and third stages, but the present invention is not limited thereto. For example, even when the interval Px between the beam spots 15a in the X direction is set to be smaller than the beam diameter and the interval Py between the beam spots 15a in the Y direction is set to be equal to or larger than the beam diameter, overlapping each other of the lines Li of the electron beam <NUM> can be avoided. Even in this case, similarly to the above-described embodiments, the risk of occurrence of smoke can be reduced, and the temperature distribution of the powder layer 32a can be made uniform.

Furthermore, in the first embodiment and the second embodiment described above, the lines Li of the electron beam <NUM> overlap each other in the final stage (fourth stage). However, the lines Li of the electron beam <NUM> may overlap each other in a stage before the final stage, and the overlapping area may be larger in the final stage than in a stage before the final stage. That is, the control unit <NUM> may control the beam irradiation apparatus <NUM> to overlap the lines Li each other in any stage of the second and subsequent stages and to gradually increase the overlapping area of the lines Li in the subsequent stage.

Furthermore, in the above-described embodiments, the case where the control unit <NUM> changes the beam current and the beam size from the start of preheating to the end of preheating has been described. However, in addition to these control parameters, at least one of a scan speed and a scan area may be changed in each stage.

When the irradiation position of the electron beam <NUM> is intermittently moved in the X direction, the scan speed is determined by the time for which the beam spot 15a stays (stops) at each irradiation position of the electron beam <NUM>. Specifically, the longer the stay time of the beam spot 15a, the slower the scan speed, and the shorter the stay time of the beam spot 15a, the faster the scan speed. When the irradiation position of the electron beam <NUM> is continuously moved in the X direction, the moving speed of the electron beam <NUM> is the scan speed. When the scan speed is changed, the time until the irradiation position of the electron beam <NUM> returns to the original position (scan cycle) becomes shorter as the scan speed is faster, and the time until the irradiation position of the electron beam <NUM> returns to the original position becomes longer as the scan speed is slower. In contrast, smoke is likely to occur when the scan speed is too fast or too slow. Therefore, in order to suppress the occurrence of smoke, it is necessary to appropriately set the scan speed. Furthermore, in the three-dimensional PBF-AM, a layer in which smoke is likely to occur and a layer in which smoke is unlikely to occur may be mixed. Therefore, in the layer in which smoke is unlikely to occur, the scan speed is made faster than in the layer in which smoke is likely to occur, so that the time required for preheating the powder layer 32a can be shortened. In addition, even in the same layer, smoke is more likely to occur in the first stage than in the later stages. Therefore, when the moving operation of the electron beam <NUM> is repeated for the same layer a predetermined number of times K (K is an integer of <NUM> or larger), the scan speed is increased in the second and subsequent moving operations as compared with the first moving operation, so that the time required for preheating the powder layer 32a can be shortened.

The scan area is determined by the area where the electron beam <NUM> is moved. For example, when the irradiation position of the electron beam <NUM> is moved from the start point Ps to the end point Pe as illustrated in <FIG>, the scan area is an area surrounded by a broken line in <FIG>. When the scan area is changed, the time until the irradiation position of the electron beam <NUM> returns to the original position becomes longer as the scan area is larger, and the time until the irradiation position of the electron beam <NUM> returns to the original position becomes shorter as the scan area is smaller. Therefore, in the layer where smoke is likely to occur, the occurrence of smoke can be suppressed by increasing the scan area. In the layer in which smoke is unlikely to occur, the time required for preheating the powder layer 32a can be shortened by reducing the scan area. In addition, even in the same layer, smoke is more likely to occur in the first stage than in the later stages. Therefore, when the moving operation of the electron beam <NUM> is repeated for the same layer a predetermined number of times K (K is an integer of <NUM> or larger), the occurrence of smoke is suppressed by increasing the scan area in the first moving operation, and the scan area is reduced as compared with the first movement operation in the second and subsequent moving operations, so that the time required for preheating the powder layer 32a can be shortened.

In the above-described embodiments, the preheating of the powder layer 32a may be ended when the temperature of the powder layer 32a reaches a predetermined temperature.

Claim 1:
A three-dimensional powder bed fusion additive manufacturing (PBF-AM) apparatus comprising:
a build plate (<NUM>);
a powder application apparatus (<NUM>) that applies metal powder (<NUM>) onto the build plate (<NUM>) to form a powder layer (32a);
a beam irradiation apparatus (<NUM>) that irradiates the powder layer (32a) with an electron beam (<NUM>); and
a control unit (<NUM>) that controls the powder application apparatus (<NUM>) and the beam irradiation apparatus (<NUM>), wherein
when the powder layer (32a) is preheated by irradiation with the electron beam (<NUM>), the control unit (<NUM>) sets a beam size and an irradiation position of the electron beam (<NUM>) such that lines (Li) of the electron beam (<NUM>) do not overlap each other at least at a start of preheating, and controls the beam irradiation apparatus (<NUM>) to gradually increase the beam size of the electron beam (<NUM>) from the start of preheating to an end of preheating.