Patent Description:
In recent years, there is a growing need for building using a 3D printer as a production means. Researches and developments have been made toward practical applications of building using a metal material. A 3D printer for building using a metal material produces an additively-manufactured object by melting a metal powder or a metal wire by use of a heat source such as a laser or an electron beam or another heat source such as an arc, and depositing the molten metal.

For example, in the case of using an arc, a filler metal is melted and solidified by the arc to form a weld bead, and the weld bead is deposited into a plurality of layers to produce an additively-manufactured object. As for a technique for forming such a weld bead, Patent Literature <NUM> describes a technique in which an impeller rotatably attached to a housing and having a plurality of blades is formed by laser cladding.

In the method for manufacturing an impeller according to Patent Literature <NUM>, each blade is formed by depositing a plurality of metal layers along the shape of the blade. However, Patent Literature <NUM> has no disclosure about a procedure for depositing and building a work having a desired shape but describes only a process of manufacturing an impeller having a specific shape.

When an additively-manufactured object is deposited and built by a weld bead, a length with which the weld bead can be continuously formed may vary depending on a direction in which the bead is formed. In the case where the continuously formed length is short, operations having no contribution to the formation of a weld bead, such as frequently turning on/off heating of the filler material and moving a torch serving as a heat source to a next bead formation position. As a result, takt time for laminating and building increases, which lowers the building efficiency.

In order to build an additively-manufactured object with a high efficiency, it is necessary to select an optimal direction to form a bead such that the bead can be formed as continuously as possible. However, how to select the direction to form the bead depends on the experience and intuition of a worker. Such work requires a great deal of skill.

On the other hand, there has been known a metal shaping technique using a powder head system for melting a powder to produce a built-up object. In this shaping method, it is not necessary to select a bead formation direction as described above, but a thermal head must scan a horizontal section two-dimensionally uniformly. Therefore, for example, the scanning time becomes long for some shapes of the built-up object. Thus, the method cannot be always regarded as an efficient shaping method.

The present invention has been developed in consideration of the aforementioned situation. An object of the invention is to provide a versatile designing method, a manufacturing method and a manufacturing apparatus for additively-manufactured object, capable of building an additively-manufactured object with a high efficiency and in a reduced takt time when the additively-manufactured object having a shape extending in a specific direction is built by depositing a weld bead in a plurality of layers, and a program for making a computer execute a procedure for designing the additively-manufactured object.

According to a first aspect of the present invention, a method for designing an additively-manufactured object to be built by depositing a plurality of weld bead layers formed of a weld bead formed by melting and solidifying a filler metal is defined in claim <NUM>.

(<NUM>) According to a second aspect of the present invention, a method for manufacturing an additively-manufactured object built by depositing a plurality of weld bead layers formed of a weld bead formed by melting and solidifying a filler metal is defined in claim <NUM>.

(<NUM>) According to a third aspect of the present invention, a program for making a computer execute a procedure for designing an additively-manufactured object to be built by depositing a plurality of weld bead layers formed of a weld bead formed by melting and solidifying a filler metal is defined in claim <NUM>.

(<NUM>) According to a fourth aspect of the present invention, an apparatus for manufacturing an additively-manufactured object to be built by depositing a plurality of weld bead layers formed of a weld bead formed by melting and solidifying a filler metal is defined in claim <NUM>.

Further embodiments of the present invention are defined in the dependent claims.

In the present invention, it is possible to build an additively-manufactured object with a high efficiency and in a reduced takt time when the additively-manufactured object having a shape extending in a specific direction is built by depositing weld beads in a plurality of layers.

Embodiments of the present invention will be described in detail below by referring to the drawings.

<FIG> is a schematic configuration view of a manufacturing apparatus for manufacturing an additively-manufactured object in the present invention.

A manufacturing apparatus <NUM> for the laminate-built objet having the configuration includes a building unit <NUM>, a building controller <NUM> for collectively controlling the building unit <NUM>, and a power supply unit <NUM>.

The building unit <NUM> includes a welding robot <NUM> having a torch <NUM> provided on the tip shaft and serving as a torch moving mechanism, and a filler metal feeding unit <NUM> for feeding a filler metal (weld wire) M to the torch <NUM>.

The welding robot <NUM> is an articulated robot which has, for example, degrees of freedom on <NUM> axes, and in the torch <NUM> attached to the tip shaft of a robot arm, the filler metal M is supported such that it can be continuously fed. The position or posture of the torch <NUM> can be set three-dimensionally desirably within the range of the degree of freedom of the robot arm.

The torch <NUM> includes a not-shown shield nozzle, and a shielding gas is supplied from the shield nozzle. The arc welding method may be either a consumable electrode type such as shielded metal arc welding or carbon dioxide gas arc welding, or a non-consumable electrode type such as TIG welding or plasma arc welding. The arc welding method is appropriately selected depending on the additively-manufactured object to be manufactured. For example, in the case of the consumable electrode type, a contact tip is disposed inside the shield nozzle, and the filler metal M to which a melting current is to be supplied is held on the contact tip.

The torch <NUM> generates an arc from the tip of the filler metal M in a shielding gas atmosphere while holding the filler metal M. The filler metal M is fed from the filler metal feeding unit <NUM> to the torch <NUM> by a not-shown delivery mechanism attached to the robot arm, etc. Then, the filler metal M fed continuously is melted and solidified while the torch <NUM> is moved by the welding robot <NUM>. Thus, linear weld beads <NUM> which are melt-solidified bodies of the filler metal M are formed on a base material <NUM> as described in detail later.

The heat source for melting the filler metal M is not limited to the aforementioned arc. A heat source using another system such as a heating system using an arc and a laser together, a heating system using a plasma or a heating system using an electron beam or a laser may be used. In the case of heating by an electron beam or a laser, a heating amount can be controlled more finely to keep each weld bead in a more proper state, thereby contributing to further improvement of the quality of the additively-manufactured object.

The building controller <NUM> includes a program generating unit <NUM>, a storage unit <NUM>, and a control unit <NUM> to which the program generating unit <NUM> and the storage unit <NUM> are connected.

The program generating unit <NUM> sets a procedure for driving the building unit <NUM> to build the additively-manufactured object, based on shape data (such as CAD data) of the additively-manufactured object to be manufactured. The shape data is input from an input unit <NUM>. The program generating unit <NUM> generates a program for making a computer execute the procedure set thus. The generated program is stored in the storage unit <NUM>. In addition, various kinds of specification information such as various drivers or movable ranges for the building unit <NUM> are stored in the storage unit <NUM>. The specification information is referred to appropriately when a program is generated by the program generating unit <NUM> or when the program is executed. The storage unit <NUM> includes a storage medium such as a memory or a hard disk, to and from which various kinds of information can be input and output.

The control unit <NUM> is a computer unit having a CPU, a memory, an I/O interface and so on. The control unit <NUM> has a function of reading a program stored in the storage unit <NUM> and executing the program, and a function of driving and controlling each portion of the building unit <NUM>. The control unit <NUM> executes driving control or a program in accordance with an instruction issued by operation on the input unit <NUM>, communication, and so on. The program will be described in detail later.

The program generating unit <NUM> does not have to be provided on the building controller <NUM> side, but may be, for example, provided separately from the apparatus <NUM> for manufacturing the additively-manufactured object and in the computer PC such as a server or a terminal disposed separately through a communication system such as a network or through a storage medium. In the case where a program generating unit <NUM> is connected to the computer PC, a program can be generated without requiring the apparatus <NUM> for manufacturing the additively-manufactured object such that the work of generating the program does not become complicated. In addition, by transmitting the generated program to the storage unit <NUM> of the building controller <NUM>, the program can be executed in the same manner as a program generated in the building controller <NUM>.

The control unit <NUM> executes a program stored in the storage unit <NUM> to drive the welding robot <NUM>, the power supply unit <NUM>, etc. in accordance with a predetermined procedure. That is, in response to an instruction from the building controller <NUM>, the welding robot <NUM> moves the torch <NUM> along a track or a locus programmed in advance, and melts the filler metal M by an arc at a predetermined timing and forms weld beads <NUM>. <FIG> shows a state in which the weld beads <NUM> are formed on a plate-shaped base material <NUM> to build an additively-manufactured object. The additively-manufactured object may have a desired shape.

The base material <NUM> is made of a metal plate such as a steel plate. Basically a metal plate larger than a bottom surface (surface of a lowermost layer) of the additively-manufactured object is used as the base material <NUM>. In addition, the base material <NUM> is not limited to such a plate-shaped one, but may be a base having another shape such as a block or a rod shape.

Any commercially available weld wire can be used as the filler metal M. For example, wires provided as MAG welding and MIG welding solid wires (JIS Z <NUM>) for mild steel, high tensile steel and cryogenic steel, and arc welding flux cored wires (JIS Z <NUM>) for mild steel, high tensile steel and cryogenic steel can be used as the filler metal M.

First, the apparatus <NUM> configured thus for manufacturing the additively-manufactured object forms a plurality of linear weld beads <NUM> adjoining one another on the base material <NUM> and forms a weld bead layer.

<FIG> is a schematic perspective view of the weld beads <NUM> formed on the base material <NUM>.

A weld bead layer H1 formed on the upper surface of the base material <NUM> is composed of a plurality of rows of the linear weld beads <NUM>, which are formed such that each weld bead <NUM> has a predetermined bead width W and is adjacent to one another without any gap. By depositing a next weld bead layer on the weld bead layer H1 repeatedly, an additively-manufactured object having a desired shape is built up.

Next, a program generated by the program generating unit <NUM> will be described in detail.

<FIG> is an explanatory view schematically showing a shape of an additively-manufactured object <NUM> to be manufactured, and directions in which weld beads are formed.

Here, it is assumed that the additively-manufactured object <NUM> has a rectangular shape as shown in (A) to (C) of <FIG>, and the rectangular shape is covered with weld beads <NUM> each having a bead width W so as to form a single weld bead layer.

In the case where a continuous formation direction Vb in which each weld bead <NUM> is formed continuously is set at a direction along the short sides of the rectangular shape as shown in (A), it is necessary to form a large number of short weld beads <NUM> along the short sides. In the case where the continuous formation direction Vb is set at a direction inclined with respect to the short sides and the long sides of the rectangular shape as shown in (B), the continuous formation length of each weld bead <NUM> can be increased and the number of weld beads <NUM> in comparison with the case of (A) can be reduced. Further, in the case where the continuous formation direction Vb for each weld bead <NUM> is set at a direction along the long sides of the rectangular shape as shown in (C), the continuous formation length of each weld bead <NUM> is further increased and the number of weld beads <NUM> is smaller than in any other case.

As the length (continuous formation length) from a start point to an end point for continuously forming each weld bead <NUM> is longer, the takt time for forming the bead can be shortened to enhance the building efficiency. That is, when the torch reaches the end point in the formation of the weld bead <NUM>, generation of the arc is stopped, and the robot arm moves the torch to a start point where a next weld bead will be formed. After the torch is moved to the start point, an arc is generated again, and the torch is moved toward a next end point. The lower the number of times of repeating the aforementioned step, the more preferable because the weld bead can be formed more continuously.

Therefore, in this configuration, a direction in which each weld bead <NUM> can be formed as continuously as possible is extracted depending on the shape of the additively-manufactured object <NUM>, and the extracted direction is set as the continuous formation direction (reference direction) for the weld bead. In this manner, the continuous formation length of each weld bead <NUM> is increased to reduce the number of times of turning the arc on/off, such that the frequency of torch movement having no contribution to the formation of the weld bead <NUM> can be reduced. Thus, the building efficiency of the additively-manufactured object can be improved.

For example, in the case where the additively-manufactured object <NUM> has at least one protrusion portion which is continuous in a specific direction, when each weld bead is formed in the specific continuous direction, the additively-manufactured object can be built efficiently, which reduces the complication of the depositing-building step. Therefore, first, a specific direction in which the additively-manufactured object is continuous is obtained from shape data of the additively-manufactured object to be manufactured. The specific direction may be determined by arithmetic operation of a computer analyzing the shape data along an appropriate algorithm, or may be determined artificially, for example by a judge of a worker.

Then, the obtained specific direction is used as a reference direction to determine a layout of weld beads in a section perpendicular to the reference direction. A program for making a computer execute the aforementioned step of setting the reference direction from the shape data and determining the layout of the weld beads is generated by the aforementioned program generating unit <NUM> (see <FIG>). The program mentioned here includes instruction codes for making the building unit <NUM> execute a procedure designed for formation of weld beads by predetermined arithmetic operation from input shape data. Accordingly, a program prepared in advance is specified by the control unit <NUM>, and the control unit <NUM> executes the specified program. Thus, the building unit <NUM> manufactures the additively-manufactured object <NUM>.

Next, along a specific example of the additively-manufactured object <NUM>, a procedure for depositing the additively-manufactured object will be described in detail.

<FIG> is a perspective view of the additively-manufactured object 41A illustrated as an example.

The additively-manufactured object 41A has a columnar shaft body <NUM>, and a plurality (six in the illustrated example) of spiral blades <NUM> protruding radially outward in the outer circumference of the shaft body <NUM>. The blades <NUM> have a screw shape in which the blades <NUM> are provided circumferentially at a same interval in an axially intermediate portion of the shaft body <NUM>.

<FIG> is a flow chart showing the procedure of the program for designing, depositing and building the additively-manufactured object 41A. Based on the figure, steps until building up the additively-manufactured object 41A will be described in order.

First, shape data such as CAD data of the additively-manufactured object 41A is input to the program generating unit <NUM> shown in <FIG> (S11). The shape data includes information about coordinates of the outer surface of the additively-manufactured object 41A, dimensional information such as the diameter, shaft length, etc. of the shaft body <NUM>, and if necessary, information about kinds of materials to be referred, final finishing, and so on. The following steps until a program is generated is performed by the program generating unit <NUM>.

<FIG> is an explanatory view showing a state in which a blank region is determined in a sectional shape of an additively-manufactured object 41A.

The additively-manufactured object 41A has a cylindrical shaft body <NUM> and a plurality of blades <NUM> provided to stand from the shaft body <NUM> as shown in <FIG>. Therefore, when the additively-manufactured object 41A is built, the whole shape thereof is not formed by an additive manufacturing method, but the shaft body <NUM> is formed using a blank such as a bar, and the blades <NUM> are formed by the additive manufacturing method. Thus, the man-hours in building the additively-manufactured object 41A can be largely reduced.

First, using input shape data, the outer shape of the additively-manufactured object 41A is divided into a blank region serving as a base body of the additively-manufactured object 41A, and an additive manufacturing region serving as the outer shape of the additively-manufactured object <NUM> to be formed on the base body.

The blank region and the additive manufacturing region are determined by the shape data and kinds of blanks which can be prepared.

In the case of the additively-manufactured object 41A shown in <FIG>, among blanks (round bars) 47A, 47B and 47C illustrated by way of example, the blank 47C having a diameter which can minimize the cutting amount for following the shape of the additively-manufactured object 41A is selected.

<FIG> is an explanatory view showing a result of dividing the outer shape of the additively-manufactured object 41A into a blank region <NUM> and an additive manufacturing region <NUM>.

In this example, the blank 47C serves as the blank region <NUM>, and each of the blades <NUM> in a region located radially outside the blank 47C serves as an additive manufacturing region <NUM> (S12).

Next, a procedure for forming weld beads in an additive manufacturing region <NUM> disposed in the outer circumference of the blank 47C determined in the aforementioned S12 will be considered.

The additive manufacturing region <NUM> is built by depositing a plurality of weld beads sequentially. Bead size including bead width, bead height, etc. in each of the weld beads constituting the additive manufacturing region <NUM> is controlled by changing welding conditions such as a moving speed of the torch <NUM> (see <FIG>), that is, a continuous formation speed of the weld bead, a heat input to a filler metal or a welding portion, that is, a welding current, a welding voltage, an applied pulse, etc. from the power supply unit <NUM>, and so on. The bead size is preferably managed on a section perpendicular to the moving direction of the torch for forming the weld beads.

<FIG> is a front view of the lamination-built object 41A, and <FIG> is an explanatory view showing a plan view of a weld bead <NUM> formed in a region A1 shown in <FIG>, and cross-sectional views of the weld bead <NUM> on line IXA-IXA and on line IXB-IXB. CL in <FIG> and <FIG> designates a central axis of the additively-manufactured object 41A.

In the additively-manufactured object 41A configured thus, the continuous formation length of each weld bead can be increased when the direction in which the spiral blade <NUM> is provided to extend is made to correspond to the continuous formation direction Vb of the weld bead. On that occasion, the bead size of the weld bead is controlled with reference to the shape of a bead section <NUM> shown in the section on the line IXB-IXB perpendicular to the continuous formation direction of the weld bead in <FIG>. The bead section <NUM> shows a section formed at the same timing in weld beads <NUM>. The bead section <NUM> is a section in a direction where a variation in speed is the minimum with respect to the moving direction of the torch <NUM> (the moving direction of a welding bar) when the weld beads <NUM> are formed. Accordingly, the shape of the bead section <NUM> directly reflects the change of the welding conditions such that a correlation between the welding conditions and the shape of the bead section <NUM> can be clearly grasped. On the other hand, in the cross-sectional view taken along line IXA-IXAperpendicular to the central axis CL direction shown in <FIG>, the shape of the bead section <NUM> corresponds to the shape of the weld beads formed at different timings in times series. Accordingly, the shape of the bead section <NUM> is hardly controlled by changing the welding conditions. In addition, in such a case that the continuous formation direction Vb of a weld bead is changed, the speed in which the bead is formed actually depends on a place on the bead section <NUM>.

Therefore, the bead size of each weld bead <NUM> is controlled in association between a change in various welding conditions and a shape of a section perpendicular to the continuous formation direction Vb of the weld bead.

Next, description will be made about the continuous formation direction Vb of weld beads in each weld bead layer when the additively-manufactured object 41A is sliced into a plurality of weld bead layers.

<FIG> is a schematic explanatory view for illustrating the continuous formation method for weld beads depending on the shape of the additively-manufactured object 41A.

The explanatory view shows circumferential faces PL1, PL2 and PL3 at different radial positions (three places in the illustrated example) from the aforementioned central axis CL in the additively-manufactured object 41A, and a direction Va in which one blade <NUM> is extended.

The circumferential face PL1 is an outer circumference face of the shaft body <NUM> of the additively-manufactured object 41A shown in <FIG>, the circumferential face PL3 includes the outermost edge of in the radial direction of blade <NUM>, and the circumferential face PL2 is a circumferential face to be disposed at a radially central position between the circumferential face PL1 and the circumferential face PL3. Here, the circumferential face PL1 corresponds to a layer where weld beads <NUM> are formed for the first time, and the circumferential face PL3 corresponds to a layer where the weld beads <NUM> are formed finally, in the additive manufacturing region <NUM> (see <FIG>).

When the circumferential faces PL1, PL2 and PL3 are developed on a plane, the circumferential face PL1 is developed as shown in (A) in <FIG>, the circumferential face PL2 is developed as shown in (B) in <FIG>, and the circumferential face PL3 is developed as shown in (C) in <FIG>. In directions Va1, Va2 and Va3 the blade <NUM> is extended as shown in (A) to (C) of <FIG>, their inclination angles from the central axis vary to θa, θb and θc (θa<θb<θc) depending on a change in circumferential length due to a difference in radial position.

<FIG> is an explanatory view in which the circumferential faces PL1, PL2 and PL3 shown in (A), (B) and (C) of <FIG> are combined on the same plane such that one-side ends of blades (left lower portions in (A), (B) and (C) of <FIG>) are made to correspond to one another.

As described previously, it is preferable that each weld bead <NUM> is formed along the direction in which the blade <NUM> is extended, and the bead size is controlled by the shape of a section perpendicular to the direction in which the blade <NUM> is extended (the continuous formation direction Vb for the weld bead). However, as shown in <FIG>, the directions Va1, Va2 and Va3 the blade is extended are not fixed but have the different inclination angles θa, θb and θc depending on the radial position of the additively-manufactured object. Therefore, when the bead size is controlled in a section perpendicular to the continuous formation direction (reference direction) of the weld bead all over the additively-manufactured object, the bead size has to be controlled individually for each position of the weld bead. In that case, it is not possible to control the bead size in common all over the additively-manufactured object, and the amount of computation for the control becomes enormous.

Therefore, a section parallel to a direction T perpendicular to the direction in which (reference direction) Va2 the blade <NUM> is extended in the circumferential face PL2 located at a radially intermediate position is used as a common control section for controlling the bead size of each weld bead. Thus, the bead size can be controlled to be the common control section at any position of the additively-manufactured object (S13).

After the control section (that is, a section perpendicular to the reference direction) for controlling the bead size of each weld bead is determined as described above, the additive manufacturing region <NUM> of the additively-manufactured object 41A is sliced into layers each having a height corresponding to one weld bead layer, so as to generate a plurality of virtual bead layers (S14).

<FIG> is an explanatory view showing a state in which one blade <NUM> serving as a part of the additive manufacturing region <NUM> of the additively-manufactured object is sliced into layers. The abscissa in <FIG> designates the direction T perpendicular to the direction in which (reference direction) the blade <NUM> is extended.

As for weld beads (illustrated as a virtual bead <NUM>) for forming the blade <NUM>, weld bead layers are deposited n times so as to include the final shape of the blade <NUM> depending on bead height H corresponding to one weld bead layer. The illustrated example shows a case where the virtual bead <NUM> shown by the broken line is deposited sequentially (layers H1, H2,. ) from the surface of the shaft body <NUM> (blank 47C), and a radially outermost edge portion 45a of the blade <NUM> is covered in the seventh layer (layer H7). That is, here is a lamination model including seven virtual bead layers.

In addition, the width of the blade <NUM> in the reference direction in the illustrated example includes a wider part and a narrower part than the bead width W of one weld bead. The narrow width part of the blade <NUM> can be built by one weld bead, but there is a fear that the outer shape of the blade cannot be formed perfectly in some place due to contraction between beads in the deposition direction (in the up/down direction in <FIG>). Therefore, in the layers H1 to H6, a plurality of weld beads (virtual beads <NUM>) are provided side by side in each virtual bead layer. The uppermost layer H7 has a size where the outer shape of the blade can be sufficiently formed by one weld bead. Thus, only one weld bead (virtual bead <NUM>) is disposed.

Here, as for the bead size of each virtual bead <NUM>, the circumferential length is longer in a layer closer to the radial outside in the layers H1 to H7. Therefore, when the moving time of the torch per one round is fixed, the moving speed of the torch is increased in a layer closer to the radial outside and the bead size is reduced. Thus, when each weld bead is formed in each layer H1 to H7, it is preferable that the moving speed is, for example, slowed down in a layer closer to the radial outside, such that the bead size is fixed in all the layers.

In addition, as described above, the position where a bead is disposed is changed in a common control section or the shape of the bead (various parameters such as bead size) is adjusted to increase or decrease, such that the additively-manufactured object can be controlled in common as a whole. Thus, change, adjustment, etc. in design can be made easily. In addition, the shape of each weld bead in each layer has symmetricity with respect to a distance from the center in the deposition direction due to a reference direction set based on a layer at the center in the deposition direction. By use of the symmetricity, design can be also simplified. For example, the shape of each weld bead located at an equal distance from the center in the deposition direction may be standardized. When the number of layers obtained by slicing is an even number, the reference direction may be determined based on an average of the two layers disposed at the center in the deposition direction or based on one of the two layers.

The aforementioned control to increase or decrease bead shapes of weld beads may be, for example, achieved by control to make all the weld beads have the same shape, control to make each weld bead have a shape depending on its position in the deposition direction (radial direction), control to make the bead shapes of the weld beads different depending on the shape of the additive manufacturing region <NUM>, etc..

Such a lamination model is generated for each of the additive manufacturing regions <NUM> of the additively-manufactured object 41A shown in <FIG>. In each lamination model, the bead size is designed using a common control section. That is, various conditions such as a layout of beads in each virtual bead layer, a bead size, welding conditions, etc. in each additive manufacturing region <NUM> are set (S15). <FIG> shows an example of division into seven virtual bead layers, but the number of divided layers may be set depending on the bead size of each weld bead, the dimensions and shape of the additively-manufactured object, etc..

Next, a program for making a computer execute a procedure for forming weld beads on a blank in accordance with the lamination model designed as described above is generated (S16).

The program is generated by the program generating unit <NUM> or <NUM> shown in <FIG>, and the generated program is stored in the storage unit <NUM>.

The control unit <NUM> of the building controller <NUM> deposits and builds the additively-manufactured object based on a generated program. That is, the control unit <NUM> reads a desired program from the storage unit <NUM> and executes the program to drive the building unit <NUM> (see <FIG>), thereby building the additively-manufactured object.

<FIG> is a step explanatory view schematically showing a state in which weld beads <NUM> are formed.

Weld beads <NUM> (23B and 23C) are placed side by side sequentially to form a weld bead layer of a first layer (layer H1) on the shaft body <NUM> of the additively-manufactured object <NUM> in accordance with the program. Then, weld beads 23A and 23D are placed side by side sequentially as a second layer (layer H2) on the weld bead layer of the first layer (layer H1).

Here, it is assumed that a boundary between the outer surface of the weld bead 23A and the outer surface of the weld bead 23B is Pc (a boundary on the illustrated right side of the weld bead 23A), a tangent to the outer surface of the weld bead 23A in the boundary Pc is L1, and a tangent to the outer surface of the weld bead 23B in the boundary Pc is L2. In addition, it is assumed that an angle between the tangents L1 and L2 is θ, and a bisector of the angle θ is N.

The next weld bead 23D adjacent to the weld bead 23A is formed using the boundary Pc as a target position. When the weld bead 23D is formed, the direction of the torch axis of the torch <NUM> is set to be substantially the same direction as the straight line N. The target position where the weld bead 23D is to be formed is not limited to the boundary Pc but may be set to be a boundary Pca between the weld bead 23B and the weld bead 23C. That is, any one of boundaries among the three weld beads 23A, 23B and 23C which have been already formed may be set as the target position where a new weld bead 23D is to be formed.

As shown in <FIG>, the torch <NUM> is moved to the illustrated deeper side (in a direction perpendicular to the paper) along the program, and the vicinity of the target position is heated by an arc generated in a shielding gas G atmosphere. Then, the filler metal M melted by the heating is solidified at the target position to form a new weld bead 23D.

On this occasion, the weld bead 23D is formed to cover the outer surface of the weld bead 23B and to bridge the outer surface of the weld bead 23A and the outer surface of the weld bead 23C. The bead size of the weld bead 23D is set to be large enough to fill a narrow portion such as the boundary Pc or Pca as described above. Thus, a welding defect such as a blowhole can be prevented from occurring among the weld beads.

As described above, in the method for designing an additively-manufactured object, the shape of the additively-manufactured object is sliced into weld bead layers each having a height corresponding to one bead layer by use of data of a shape of the additively-manufactured object to generate a plurality of virtual bead layers. Further, a direction in which the sliced layer of the additively-manufactured object is continuously extended in intermediate layers disposed at a center between, among the plurality of virtual bead layers, a front layer to be formed for the first time and a rear layer to be formed finally, is set as a reference direction. Then, a bead size of each weld bead to be formed in the plurality of virtual bead layers is adjusted depending on a shape of the bead in a section perpendicular to the reference direction.

In accordance with a lamination model designed thus for the additively-manufactured object, weld beads are formed and deposited with adjusted bead sizes sequentially from the front layer to the rear layer of the plurality of virtual bead layers. Thus, the additively-manufactured object is built.

Unnecessary parts are removed from the additively-manufactured object built thus by cutting, grinding and so on to finish the additively-manufactured object into a final product shape.

As described above, a reference direction for determining a control section for controlling each bead size is not limited to the direction in which a blade is extended in the circumferential face PL2 at the center of the radial direction between the circumferential face PL3 having a largest diameter and the circumferential face PL1 having a smallest diameter in the additive manufacturing region shown in <FIG>. For example, the reference direction may be set as the direction in which a blade is extended in a virtual bead layer disposed at the center (center in the radial direction) in the deposition direction of divided virtual bead layers when the additive manufacturing region is divided into the layers. Even in this case, the same direction in which the blade is extended is set as the reference direction consequently. That is, the setting of the reference direction may be established in a stage of Step S15 where conditions for forming each layer are set, as shown in <FIG>. The reference direction may be set in Step S13 or may be set after the division into layers in Step S14.

A layout of weld beads or a design of bead sizes in the additive manufacturing region is not limited to be applied to an additively-manufactured object which is a rotating symmetry body shown in <FIG>. The designing method or the manufacturing method in the present invention can be suitably applied to an additively-manufactured object as long as it has a shape including at least one protrusion portion continuous along a specific direction. Particularly, an additively-manufactured object having a shape having a twisted structure where the specific direction varies along the deposition direction can be built more efficiently.

Claim 1:
A computer-implemented method for designing an additively-manufactured object (<NUM>) to be built by depositing a plurality of weld bead layers (H1-H7) formed of a weld bead (<NUM>) formed by melting and solidifying a filler metal (M), the method comprising in the following order:
an inputting step of inputting a shape data of the additively-manufactured object (<NUM>) to a program generating unit (<NUM>);
a dividing step of dividing the shape of the additively-manufactured object (<NUM>) into a blank region (<NUM>) serving as a base body (<NUM>) of the additively-manufactured object (<NUM>), and an additive manufacturing region (<NUM>) including a protrusion portion to be formed on the base body (<NUM>);
and being characterised by:
a setting step of setting, as a reference direction, a direction (Vb) in which a sliced layer of the additively-manufactured object (<NUM>) is continuously provided and, as a common control section, a section perpendicular to the reference direction (Vb) extended in a circumferential face (PL2) disposed at a radially central position between an outermost edge (45a) of the additively-manufactured object (<NUM>) and an outer circumference face (PL1) of the base body (<NUM>) of the additively-manufactured object (<NUM>);
a slicing step of slicing the shape of the additively-manufactured object (<NUM>) into the weld bead layers (H1-H7) each having a height (H) corresponding to one bead layer (H1-H7) using the data of the shape of the additively-manufactured object (<NUM>), thereby generating the plurality of virtual bead layers (<NUM>); and
a bead controlling step of controlling the bead size of each weld bead (<NUM>) in association between a change in various welding conditions and a shape of a section perpendicular to the continuous formation direction (Vb) of the weld bead (<NUM>).