24. The galvanometer scanner moves the laser beam 24 by rotating the mirror within the range of a specific scan angle. Alternatively, the beam drive unit 20 includes a condenser lens for condensing the laser beam 24, and moves the laser beam 24 by moving the condenser lens in the X axis direction and the Y axis direction. The beam drive unit 20 may have any configuration not limited to the above configuration.

The additive manufacturing apparatus 100 includes a controller 1 that performs overall control on the additive manufacturing apparatus 100. The controller 1 controls the additive manufacturing apparatus 100 according to a machining program. The controller 1 is, for example, a numerical control (NC) device. In the first embodiment, the machining program is an NC program.

The NC program specifies the machining path. The controller 1 analyzes the machining path on the basis of the NC program. The controller 1 generates various commands according to the machining path and machining conditions set for machining. The controller 1 generates a position command that is an interpolation point group for each unit time on the machining path. The controller 1 outputs the position command to the head drive unit 14, thereby controlling the head drive unit 14.

The controller 1 generates a beam output command that is a command based on a condition of beam intensity. The controller 1 outputs the beam output command to the laser oscillator 2, thereby controlling the laser oscillator 2. The controller 1 generates a material feed command that is a command based on a condition of a feed of the wire 5. The controller 1 outputs the material feed command to the rotary motor 4, thereby controlling the rotary motor 4. The material feed command may be a command based on a condition of a feed rate of the wire 5. The feed rate is a rate at which the wire 5 is fed from the wire spool 6 toward the machining point. The feed rate represents the feed of the material per hour.

The controller 1 generates a gas supply command that is a command based on a condition of a supply of the gas. The controller 1 outputs the gas supply command to the gas supply device 7, thereby controlling the amount of the inert gas 25 supplied from the gas supply device 7 to the gas nozzle 13. The controller 1 generates a rotation command that causes the workpiece to be in the posture suitable for machining. The controller 1 outputs the rotation command to the rotation mechanism 16, thereby controlling the rotation mechanism 16.

The controller 1 generates a beam move command that is a command for moving the laser beam 24. The controller 1 outputs the beam move command to the beam drive unit 20, thereby controlling the beam drive unit 20. The controller 1 generates a current command for heating the wire 5 to a desired temperature. The controller 1 outputs the current command to the hot wire power supply 21, thereby controlling the hot wire power supply 21.

The controller 1 determines, on the basis of a direction of travel of the tip portion of the wire 5, a direction in which the laser beam 24 is moved, and controls the head drive unit 14, i.e., the first drive unit and the beam drive unit 20, i.e., the second drive unit such that the laser beam 24 can be moved is movable in a manner different from the movement of the tip portion of the wire 5 relative to the workpiece. The direction of travel, which is included in the reference plane, is a direction in which the tip portion of the wire 5 travels relative to the workpiece. The movement of the laser beam 24 in the manner different from the movement of the tip portion of the wire 5 means that, aside from the movement of the laser beam 24 with the tip portion of the wire 5 by the movement of the machining head 10, the laser beam 24 moves with respect to the tip portion of the wire 5.

As described above, since the wire nozzle 12 is integrated with the machining head 10, the direction of travel of the tip portion of the wire 5 is also the direction in which the machining head 10 travels with respect to the workpiece. The controller 1 controls the head drive unit 14 by regarding the direction of travel of the machining head 10 as the direction of travel of the tip portion of the wire 5. That is, it can also be said that the controller 1 determines the direction in which the laser beam 24 is moved on the basis of the direction of travel of the machining head 10.

Next, the operation of the additive manufacturing apparatus 100 will be described. FIG. 2 is a flowchart illustrating an example of an operation procedure of the additive manufacturing apparatus 100 according to the first embodiment.

In step S1, the controller 1 of the additive manufacturing apparatus 100 reads the direction of travel of the machining head 10 from the NC program. The controller 1 analyzes the machining path on the basis of the NC program. The controller 1 obtains the direction of travel of the machining head 10 for each machining point that is a position corresponding to each control cycle in the machining path.

In step S2, the controller 1 determines the irradiation position of the laser beam 24 on the basis of the direction of travel read in step S1. A method of determining the irradiation position will be described later.

In step S3, the additive manufacturing apparatus 100 sets the position of the laser beam 24 at the irradiation position determined in step S2 and starts the formation of a bead. In step S4, the controller 1 of the additive manufacturing apparatus 100 reads the direction of travel of the machining head 10 from the NC program.

In step S5, the controller 1 determines whether or not the direction of travel of the machining head 10 has changed. The controller 1 determines whether or not the direction of travel read in step S4 has changed from the direction of travel read in step S1. If determining in step S5 that the direction of travel has not changed (No in step S5), the additive manufacturing apparatus 100 proceeds to step S7 of the procedure.

On the other hand, if determining in step S5 that the direction of travel has changed (Yes in step S5), in step S6, the controller 1 determines the irradiation position of the laser beam 24 on the basis of the direction of travel read in step S4. The additive manufacturing apparatus 100 sets the position of the laser beam 24 at the irradiation position determined in step S6 and continues the formation of the bead. After completing step S6, the additive manufacturing apparatus 100 returns to step S4 of the procedure.

In step S7, the controller 1 determines whether or not the formation of the bead started in step S3 has been completed. If the formation of the bead has not been completed (No in step S7), the additive manufacturing apparatus 100 returns to step S4 of the procedure. On the other hand, if the formation of the bead has been completed (Yes in step S7), the additive manufacturing apparatus 100 ends the operation according to the procedure illustrated in FIG. 2. The additive manufacturing apparatus 100 forms each of the beads making up an object by the operation according to the procedure illustrated in FIG. 2.

The additive manufacturing apparatus 100 determines the irradiation position of the laser beam 24 before the direction of travel of the machining head 10 changes, and changes the irradiation position of the laser beam 24 to coincide with the timing at which the direction of travel of the machining head 10 changes. Therefore, the controller 1 always performs read-ahead on the NC program to determine the irradiation position of the laser beam 24. In the analysis of the NC program, read-ahead refers to performing analysis on processing that is to be executed after processing currently executed.

The speed of the machining head 10 at the time of forming the bead is, for example, about 300 mm/min to 3000 mm/min. In a case where the irradiation position of the laser beam 24 is changed every 1 mm in the machining path, the controller 1 performs control to change the irradiation position of the laser beam 24 at intervals of approximately 20 msec.

Note that the controller 1 may set the irradiation position of the laser beam 24 in advance with respect to the machining path generated by a computer aided manufacturing (CAM) device, and change the irradiation position on the basis of the setting. For example, in a case where it is difficult to control the irradiation position of the laser beam 24 at intervals of approximately 20 msec while reading the direction of travel of the machining head 10 from the NC program, the controller 1 can properly change the irradiation position by setting the irradiation position in advance.

FIG. 3 is a diagram illustrating how an object is formed by the additive manufacturing apparatus 100 according to the first embodiment. FIG. 3 schematically illustrates how a bead 35 is formed on the substrate 17 that is the workpiece. The machining area 34 is an area where machining is performed, and is an area centered on the machining point. In FIG. 3, the machining point is a position on a surface 32 of the substrate 17, and is an intersection of a central axis CL of the beam nozzle 11 and a central axis CW of the wire 5 fed from the wire nozzle 12. FIG. 3 omits the illustration of the beam nozzle 11. The irradiation with the laser beam 24 occurs within the machining area 34. The wire 5 is fed to the machining point.

By the irradiation with the laser beam 24, a molten pool 33 is formed in a part of the surface 32 within the machining area 34. A melt 31 of the wire 5 is placed on the molten pool 33. The melt 31 and the molten pool 33 are integrated together and solidified to form the bead 35 joined to the substrate 17.

An arrow 36 indicates the direction of travel of the machining head 10. When the bead 35 is formed as the machining head 10 is moved in the direction of the arrow 36, the bead 35 having a linear shape whose longitudinal direction coincides with the direction of the arrow 36 is formed on the substrate 17. An arrow 37 indicates a direction in which the laser beam 24 is moved. In the example illustrated in FIG. 3, the direction in which the laser beam 24 is moved is a direction perpendicular to the direction of travel of the machining head 10. In FIG. 3, the irradiation position of the laser beam 24 is a position shifted from the machining point in the direction of the arrow 37.

Next, the movement of the laser beam 24 by the beam drive unit 20 will be described in detail. FIG. 4 is a diagram for explaining the movement of the laser beam 24 in the additive manufacturing apparatus 100 according to the first embodiment.

In FIG. 4, angles such as 0°, 45°, . . . , and 315° indicate the direction of travel of the machining head 10. The angle indicating the direction of travel of the machining head 10 is relative to the positive X direction. A spot 38 is a cross section of the laser beam 24 in the reference plane. An arrow 39 indicates the direction in which the laser beam 24 is moved. FIG. 4 illustrates how the irradiation position of the laser beam 24 is changed according to the direction of travel of the machining head 10.

When the direction of travel is 0° and when the direction of travel is 180°, the center of the spot 38 coincides with the position of the tip portion of the wire 5. When the direction of travel is other than 0° or 180°, the center of the spot 38 shifts forward in the direction of travel. During a gradual change in the direction of travel from 0° to 90° via 45°, the direction of the arrow 39, that is, the direction in which the spot 38 is shifted gradually changes from the positive X direction to the positive Y direction. Moreover, the amount of shift of the center of the spot 38 from the tip portion of the wire 5 gradually increases from zero. When the direction of travel is 90°, the amount of shift is maximized.

During a gradual change in the direction of travel from 90° to 180° via 135°, the direction in which the spot 38 is shifted changes from the positive Y direction to the negative X direction. Moreover, the amount of shift gradually decreases from the maximum value of the amount of shift. When the direction of travel is 180°, the amount of shift is zero.

During a gradual change in the direction of travel from 180° to 270° via 225°, the direction in which the spot 38 is shifted changes from the negative X direction to the negative Y direction. Moreover, the amount of shift gradually increases from zero. When the direction of travel is 270°, the amount of shift is maximized. During a gradual change in the direction of travel from 2700 to 360°, that is, 0° via 315°, the direction in which the spot 38 is shifted changes from the negative Y direction to the positive X direction. Moreover, the amount of shift gradually decreases from the maximum value of the amount of shift. When the direction of travel is 0°, the amount of shift is zero.

In the controller 1, as described above, the relationship between the direction of travel of the machining head 10 and the direction in which the laser beam 24 is moved is set in advance. On the basis of such a relationship, the controller 1 obtains, from the direction of travel of the machining head 10, the direction in which the laser beam 24 is moved by the beam drive unit 20.

In the first embodiment, the controller 1 sets the direction in which the laser beam 24 is moved by the beam drive unit 20 to be the same direction as the direction of travel of the machining head 10. Therefore, the beam drive unit 20 moves the laser beam 24 forward in the direction of travel of the machining head 10.

Also in the controller 1, as described above, the relationship between the direction of travel of the machining head 10 and the amount of shift by which the laser beam 24 is moved is set in advance. On the basis of such a relationship, the controller 1 obtains, from the direction of travel of the machining head 10, the amount of shift of the laser beam 24 by the beam drive unit 20. The controller 1 thus adjusts the amount of shift of the laser beam 24 from the tip portion of the wire 5 in accordance with the direction of travel of the machining head 10.

FIG. 5 is a diagram illustrating how the laser beam 24 is moved by the additive manufacturing apparatus 100 according to the first embodiment. FIG. 5 illustrates an example in which the direction of travel of the machining head 10 is 90°.

As described above, when the direction of travel of the machining head 10 is 90°, the amount of shift of the spot 38 is maximized. As illustrated in FIG. 5, when an edge of the wire 5 opposite to the direction of travel of the machining head 10 is aligned with an edge of the spot 38 opposite to the direction of travel of the machining head 10, the amount of shift of the spot 38 is maximized.

Note that when the direction of travel of the machining head 10 is 270° as well, the edge of the wire 5 opposite to the direction of travel of the machining head 10 is aligned with the edge of the spot 38 opposite to the direction of travel of the machining head 10. In such a state, the amount of shift of the spot 38 is maximized.

In FIG. 5, the wire 5 has a diameter of 1.2 mm, and the laser beam 24 has a diameter of 3.0 mm. The distance between the central axis CW of the wire 5 and the center of the spot 38 is 0.9 mm. That is, in the state illustrated in FIG. 5, the laser beam 24 is moved 0.9 mm forward from the tip portion of the wire 5.

When the direction of travel of the machining head 10 gradually changes from 0° to 90°, the amount of shift is increased by 0.01 mm each time the direction of travel of the machining head 10 changes by 1°. Thus, when the direction of travel of the machining head 10 gradually changes from 0° to 90°, the controller 1 gradually increases the amount of shift of the laser beam 24. When the direction of travel of the machining head 10 gradually changes from 90° to 180°, the amount of shift is decreased by 0.01 mm each time the direction of travel of the machining head 10 changes by 1°. Thus, when the direction of travel of the machining head 10 gradually changes from 90° to 180°, the controller 1 gradually decreases the amount of shift of the laser beam 24.

When the direction of travel of the machining head 10 gradually changes from 180° to 270°, as in the case of 0° to 90°, the controller 1 gradually increases the amount of shift of the laser beam 24. When the direction of travel of the machining head 10 gradually changes from 270° to 360°, as in the case of 90° to 180°, the controller 1 gradually decreases the amount of shift of the laser beam 24.

In the additive manufacturing apparatus 100, when the tip portion of the wire 5 comes into contact with an insufficiently melted portion of the workpiece, the wire 5 may be bent or may break. Alternatively, the insufficiently melted portion may become an obstacle and hinder the movement of the tip portion in the direction of the reference plane. The likelihood of occurrence of such a defect due to the presence of the insufficiently melted portion changes depending on the direction in which the tip portion of the wire 5 is moved. As the direction of travel of the tip portion of the wire 5 is closer to perpendicular to the central axis CW of the wire 5, such a defect is more likely to occur.

In the first embodiment, the additive manufacturing apparatus 100 moves the laser beam 24 by the beam drive unit 20 to adjust the irradiation position of the laser beam 24 with respect to the change in the direction in which the tip portion of the wire 5 is moved. The additive manufacturing apparatus 100 moves the laser beam 24 forward in the direction of travel of the machining head 10 to accelerate melting of the workpiece ahead of where the tip portion of the wire 5 is moved. The additive manufacturing apparatus 100 accelerates melting of the workpiece ahead of where the tip portion of the wire 5 is moved, thereby reducing the defect as described above. The additive manufacturing apparatus 100 can thus perform stable machining.

The additive manufacturing apparatus 100 increases the amount of shift of the laser beam 24 as the direction of travel of the tip portion of the wire 5 is closer to perpendicular to the central axis CW of the wire 5, thereby accelerating melting of the workpiece when the defect is more likely to occur. As a result, the additive manufacturing apparatus 100 can more effectively reduce the defect. The additive manufacturing apparatus 100 can also perform stable machining regardless of the direction of travel of the tip portion of the wire 5.

The additive manufacturing apparatus 100 accelerates melting of the workpiece ahead to thereby prevent the bead width from becoming narrower than expected due to the flow of the melted metal being hindered by the wire 5. The additive manufacturing apparatus 100 can thus form the bead 35 having a desired bead width.

According to the first embodiment, the additive manufacturing apparatus 100 determines, on the basis of the direction of travel of the tip portion of the wire 5, the direction in which the laser beam 24 is moved by the second drive unit. The additive manufacturing apparatus 100 controls the first drive unit and the second drive unit such that the laser beam 24 can be moved in the manner different from the movement of the tip portion of the wire 5 relative to the workpiece. The additive manufacturing apparatus 100 can reduce the defect caused by the wire 5 coming into contact with the insufficiently melted portion, and can achieve stable machining. The additive manufacturing apparatus 100 thus has an effect of achieving stable machining.

Second Embodiment

A second embodiment will describe an example in which the irradiation area of the laser beam 24 is expanded by moving the laser beam 24 at a high speed. The configuration of the additive manufacturing apparatus 100 according to the second embodiment is similar to the configuration of the additive manufacturing apparatus 100 according to the first embodiment. In the second embodiment, the same components as those in the above first embodiment are denoted by the same reference numerals as those assigned to such components in the first embodiment, and the operation different from that of the first embodiment will be mainly described.

FIG. 6 is a diagram illustrating how the laser beam 24 is moved by the beam drive unit 20 of the additive manufacturing apparatus 100 according to the second embodiment. FIG. 6 illustrates an example in which the laser beam 24 is moved in an irradiation area 40 larger than the spot of the laser beam 24 on the substrate 17 that is the workpiece. FIG. 6 schematically illustrates how the laser beam 24 is moved in the irradiation area 40.

In the second embodiment, the beam drive unit 20 makes the irradiation area 40 of the laser beam 24 on the workpiece larger than the spot of the laser beam 24 by moving the laser beam 24 faster than the speed at which the tip portion of the wire 5 is moved. In FIG. 6, an arrow 41 indicates an example of a path in which the laser beam 24 is moved in the irradiation area 40.

FIG. 7 is a first diagram for explaining the irradiation area 40 in which the laser beam 24 is moved by the beam drive unit 20 of the additive manufacturing apparatus 100 according to the second embodiment. FIG. 8 is a second diagram for explaining the irradiation area 40 in which the laser beam 24 is moved by the beam drive unit 20 of the additive manufacturing apparatus 100 according to the second embodiment. The irradiation area 40 illustrated in FIGS. 7 and 8 has a shape close to a rectangle in which each of four corners is deformed to be rounded.

FIG. 7 illustrates an example in which the orientation of the irradiation area 40 is changed in accordance with the change in the direction of travel of the machining head 10. In the example illustrated in FIG. 7, the orientation of the irradiation area 40 is changed such that the long side of the rectangle is perpendicular to the direction of travel of the tip portion of the wire 5. In the second embodiment, the controller 1 changes the orientation of the irradiation area 40 in accordance with the direction of travel of the tip portion of the wire 5 by determining the direction in which the laser beam 24 is moved on the basis of the direction of travel of the tip portion of the wire 5.

The controller 1 controls the head drive unit 14, i.e., the first drive unit and the beam drive unit 20, i.e., the second drive unit such that the laser beam 24 can be moved in a manner different from the movement of the tip portion of the wire 5 relative to the workpiece. The controller 1 thus moves the laser beam 24 faster than the speed at which the tip portion of the wire 5 is moved. In addition, the controller 1 controls to move the laser beam 24 in the direction determined in accordance with the direction of travel of the tip portion of the wire 5.

In FIG. 8, the arrow 41 indicates an example of the path in which the laser beam 24 is moved in the irradiation area 40. A spot 42 of the laser beam 24 has a circular shape smaller than the irradiation area 40. In the case of the example illustrated in FIG. 8, the beam drive unit 20 moves the spot 42 back and forth multiple times along the long side of the rectangle, thereby moving the spot 42 across the irradiation area 40. The additive manufacturing apparatus 100 moves the machining head 10 to move the irradiation area 40 on the workpiece.

The additive manufacturing apparatus 100 moves the spot 42 faster than the movement of the machining head 10, thereby achieving pseudo expansion of the spot 42 and performing irradiation with the laser beam 24. The bead 35 is formed in the irradiation area 40. The additive manufacturing apparatus 100 can form the bead 35 in the irradiation area 40 larger than the spot 42. The additive manufacturing apparatus 100 moves the laser beam 24 by the beam drive unit 20 to thereby perform machining similar to that when the spot 42 is expanded to the irradiation area 40. Note that the laser beam 24 in the irradiation area 40 can take any path not limited to the path indicated by the arrow 41 in FIG. 8.

For example, moving the laser beam 24 at a frequency of 1 kHz or higher can obtain the irradiation area 40 formed by pseudo expansion of the spot 42. In a case where the irradiation area 40 in the longitudinal direction thereof has a length of 6 mm, when the laser beam 24 is moved back and forth at an amplitude of 3 mm and a frequency of 1 kHz, the speed of movement of the laser beam 24 is approximately 20 m/sec. However, even in a case where the speed of movement of the laser beam 24 is lower than 20 m/sec, the irradiation area 40 formed by pseudo expansion of the spot 42 can be obtained. In this example, even when the speed of movement of the laser beam 24 is lower than 20 m/sec, the irradiation area 40 can be obtained as long as the speed of movement of the laser beam 24 is sufficiently higher than the speed of movement of the machining head 10. The speed of movement of the laser beam 24 being sufficiently higher than the speed of movement of the machining head 10 means that energy capable of forming the molten pool 33 can be applied to the irradiation area 40 by moving the laser beam 24. The additive manufacturing apparatus 100 sets the speed of movement of the laser beam 24 to a speed that is approximately 10 times to 20 times or more the speed of movement of the machining head 10, thereby obtaining the irradiation area 40 formed by pseudo expansion of the spot 42.

The additive manufacturing apparatus 100 forms the irradiation area 40 obtained by pseudo expansion of the spot 42, thereby forming the bead 35 having a width that is about five times to 10 times the diameter of the wire 5. The additive manufacturing apparatus 100 forms the irradiation area 40 by the movement of the laser beam 24, thereby increasing the energy density of the laser beam 24 as compared with a case where the diameter of the laser beam 24 is increased. Therefore, when forming the bead 35 having the width larger than the diameter of the wire 5, the additive manufacturing apparatus 100 can improve the machining speed as compared with the case where the diameter of the laser beam 24 is increased.

For example, when the irradiation area 40 being a rectangle of 2 mm by 8 mm is compared with a circular beam having a diameter of 8 mm, the energy density is 3.14 times higher in the case of the rectangle. The circular beam is the laser beam 24 having a circular cross section perpendicular to the central axis of the laser beam 24. The irradiation area 40 being the rectangle has anisotropy, so that if the orientation of the irradiation area 40 in the reference plane is fixed regardless of the direction of travel of the machining head 10, a change in the direction of travel of the machining head 10 causes a change in the width of the bead 35 as well. In the second embodiment, as described above, the orientation of the irradiation area 40 can be changed in accordance with the direction of travel, whereby the additive manufacturing apparatus 100 can form the bead 35 having a constant width while changing the direction of travel of the machining head 10.

The irradiation area 40 formed by pseudo expansion of the spot 42 is not limited to the rectangle described above, and may have a shape other than the rectangle. The additive manufacturing apparatus 100 can form the irradiation area 40 in any shape by the movement of the laser beam 24.

FIG. 9 is a diagram illustrating a first modification of the irradiation area 40 in which the laser beam 24 is moved by the beam drive unit 20 of the additive manufacturing apparatus 100 according to the second embodiment. An irradiation area 43 as the first modification of the irradiation area 40 has a shape in which one long side of the rectangle is changed to a curve, resulting in a shape similar to a cross section of a convex lens. FIG. 9 illustrates an example in which the orientation of the irradiation area 43 is changed in accordance with a change in the direction of travel of the machining head 10. In the example illustrated in FIG. 9, the orientation of the irradiation area 43 is changed such that the longitudinal direction of the shape of the irradiation area 43 is perpendicular to the direction of travel of the tip portion of the wire 5.

In the example illustrated in FIG. 9, when the direction of travel is 0° and 180°, the center of the irradiation area 43 coincides with the position of the tip portion of the wire 5. When the direction of travel is other than 0° or 180°, the center of the irradiation area 43 shifts forward in the direction of travel. When the direction of travel is 90° and 270°, the amount of shift by which the center of the irradiation area 43 is moved from the tip portion of the wire 5 is maximized. When the edge of the wire 5 opposite to the direction of travel of the machining head 10 is aligned with an edge of the irradiation area 43 opposite to the direction of travel of the machining head 10, the amount of shift of the irradiation area 43 is maximized. The beam drive unit 20 thus moves the irradiation area 43 forward in the direction of travel of the tip portion of the wire 5. That is, the beam drive unit 20 moves the laser beam 24 forward in the direction of travel. Moreover, the controller 1 adjusts the amount of shift of the center of the irradiation area 43 from the tip portion of the wire 5 in accordance with the direction of travel of the tip portion of the wire 5.

Moreover, in the example illustrated in FIG. 9, when the direction of travel is 0°, a portion of the outer shape of the irradiation area 43 corresponding to a flat surface opposite to a convex surface of the convex lens is oriented forward in the direction of travel. On the other hand, when the direction of travel is 180°, the said portion of the irradiation area 43 is oriented rearward in the direction of travel. Also, when the direction of travel is 135° and 225°, as with the case where the direction of travel is 180°, the said portion of the irradiation area 43 is oriented rearward in the direction of travel. The additive manufacturing apparatus 100 adjusts the orientation of the irradiation area 43 as described when the direction of travel is between 135° and 180°. By such adjustment, the additive manufacturing apparatus 100 sufficiently melts the workpiece in a portion of the irradiation area 43 where the laser beam 24 is less blocked by the wire 5. The additive manufacturing apparatus 100 sufficiently melts the workpiece by such adjustment of the irradiation area 43, thereby forming the bead 35 having a desired bead width.

The additive manufacturing apparatus 100 accelerates melting of the workpiece ahead of where the tip portion of the wire 5 is moved, thereby reducing a defect such as bending of the wire 5, breakage of the wire 5, or a problem with the movement of the wire 5. The additive manufacturing apparatus 100 can thus perform stable machining. The shape of the irradiation area 43 is obtained by deforming the rectangle, so that a change in the area of a portion of the wire 5 irradiated with the laser beam 24 is reduced. The change in the area according to the change in the direction of travel of the machining head 10 is reduced, whereby melting of the wire 5 is stabilized. The additive manufacturing apparatus 100 stabilizes melting of the wire 5 to thereby accurately form the bead 35 having a desired width.

FIG. 10 is a diagram illustrating a second modification of the irradiation area 40 in which the laser beam 24 is moved by the beam drive unit 20 of the additive manufacturing apparatus 100 according to the second embodiment. An irradiation area 44 as the second modification of the irradiation area 40 has a so-called horseshoe shape. FIG. 10 illustrates an example in which the shape of the irradiation area 44 is changed in accordance with the change in the direction of travel of the machining head 10. In the example illustrated in FIG. 10, the shape of the irradiation area 44 changes such that the area of the portion of the wire 5 irradiated with the laser beam 24 is constant.

When the area of the portion of the wire 5 irradiated with the laser beam 24 is constant regardless of the direction of travel of the machining head 10, melting of the wire 5 is stabilized. The additive manufacturing apparatus 100 changes the shape of the irradiation area 44 as appropriate, thereby sufficiently melting both an edge of the wire 5 on the front side in the direction of travel of the machining head 10 and an edge of the wire 5 on the rear side in the direction of travel of the machining head 10. The additive manufacturing apparatus 100 stabilizes melting of the wire 5 to thereby accurately form the bead 35 having a desired width. The additive manufacturing apparatus 100 changes the shape of the irradiation area 44 as appropriate, thereby setting the area of the portion of the wire 5 irradiated with the laser beam 24 to any area. The additive manufacturing apparatus 100 can set at will the area of the portion of the wire 5 irradiated with the laser beam 24 in accordance with an amount of material desired to be melted.

As exemplified in the second embodiment, the additive manufacturing apparatus 100 sets the path in which the laser beam 24 is moved by the beam drive unit 20 as appropriate, thereby forming the irradiation area 40 in any desired shape. The irradiation area 40 may have, for example, a circular shape with a diameter larger than the diameter of the laser beam 24. The additive manufacturing apparatus 100 sets the shape of the irradiation area 40 as appropriate to thereby easily form the bead 35 having any desired width. The additive manufacturing apparatus 100 can form the bead 35 having any desired width without increasing the diameter of the laser beam 24. That is, the additive manufacturing apparatus 100 can form the bead 35 having any desired width by using the laser beam 24 having a small diameter.

Here, advantages of using the laser beam 24 having a small diameter will be described. A first advantage is that, as described above, the shape of the irradiation area 40 can be set as appropriate, so that the bead 35 having a desired width can be accurately formed. A second advantage is that the energy density of the laser beam 24 can be increased, so that an object can be formed using a highly reflective material such as copper, gold, or silver as the material.

The following Formula (1) is a temperature rise formula at the time of single-pulse machining using a circular heat source. In Formula (1), “6” represents temperature, “A” represents thermal absorptivity, “P” represents average power, “a” represents a radius of the spot, and “K” represents thermal conductivity. Moreover, “J₀” represents a Bessel function of the first kind of order zero, “J₁” represents a Bessel function of the first kind of order one, “r” represents a measurement distance, and “t” represents irradiation time. According to such a temperature rise formula, one can see that, when the surface of gold is melted, for example, beam intensity of about 3 MW/cm²is required. When laser power is 6 kW, the beam diameter needs to be 0.5 mm or smaller.

Formula
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In a case where a typical metal wire having a diameter of 1 mm or larger is used, the beam diameter of 0.5 mm is too small. Therefore, machining using such a typical metal wire cannot use a beam having the beam diameter of 0.5 mm. On the other hand, according to the second embodiment, the bead 35 having any desired width can be formed, and thus the laser beam 24 having the beam diameter of about 0.5 mm or 0.5 mm or smaller can be used. Therefore, the additive manufacturing apparatus 100 can form the object using the wire 5 made of the highly reflective material. The additive manufacturing apparatus 100 can perform building with the highly reflective materials using a laser used in conventional additive manufacturing without using a special laser with high power.

According to the second embodiment, the additive manufacturing apparatus 100 makes the irradiation area 40 of the laser beam 24 on the workpiece larger than the spot 42 by moving the laser beam 24 faster than the speed at which the tip portion of the wire 5 is moved. Therefore, the additive manufacturing apparatus 100 can accurately form the bead 35 having a desired width. Moreover, the additive manufacturing apparatus 100 can use the laser beam 24 having the diameter smaller than the diameter of the wire 5, thereby forming the object using the wire 5 made of the highly reflective material.

Third Embodiment

A third embodiment will describe an example in which an object is formed by switching between fine building and rough building. The configuration of the additive manufacturing apparatus 100 according to the third embodiment is similar to the configuration of the additive manufacturing apparatus 100 according to the first embodiment. In the third embodiment, the same components as those in the above first or second embodiment are denoted by the same reference numerals as those assigned to such components in the first or second embodiment, and the operation different from that of the first or second embodiment will be mainly described.

FIG. 11 is a diagram illustrating how an object is formed by the additive manufacturing apparatus 100 according to the third embodiment. The additive manufacturing apparatus 100 adjusts an amount of movement of the laser beam 24 by the beam drive unit 20 for each portion of the workpiece, thereby switching between fine building and rough building for each portion of the workpiece. Fine building is building that focuses on increasing the shape accuracy of the object rather than increasing the machining speed. Rough building is building that focuses on increasing the machining speed rather than increasing the shape accuracy of the object.

An arrow 53 indicates that the laser beam 24 is moved by the beam drive unit 20. An arrow 54 indicates the direction of travel of the machining head 10. A bead 51 is the bead 35 formed by fine building. A bead 52 is the bead 35 formed by rough building. Compared to the bead 52, the bead 51 has a smaller bead width in the direction of travel of the machining head 10. In the third embodiment, the beam drive unit 20 varies the size of the irradiation area 40 at different positions on the reference plane of the workpiece.

In the example illustrated in FIG. 11, the beam drive unit 20 reduces the width of the irradiation area 40 at each of both ends of the workpiece along the direction of travel of the machining head 10 compared to other portions of the workpiece. The beam drive unit 20 adjusts the amount of movement of the laser beam 24 in the direction of travel of the machining head 10, thereby adjusting the width of the irradiation area 40. In the example illustrated in FIG. 11, the beam drive unit 20 adjusts the width of the irradiation area 40 by adjusting the width in which the laser beam 24 is moved back and forth in the direction of travel of the machining head 10. The additive manufacturing apparatus 100 adjusts the width of the irradiation area 40 to adjust the bead width of the bead 35 that is formed. The additive manufacturing apparatus 100 adjusts the bead width according to the position on the workpiece, thereby forming the bead 51 at each of the both ends of the workpiece and forming the bead 52 in the portion other than the both ends of the workpiece.

As described above, the additive manufacturing apparatus 100 adjusts the width of the irradiation area 40 according to the position on the reference plane of the workpiece, thereby varying the size of the irradiation area 40 according to the position on the workpiece. The additive manufacturing apparatus 100 varies the size of the irradiation area 40 according to the position on the workpiece, thereby switching between the formation of the bead 51 and the formation of the bead 52 according to the position on the workpiece.

The additive manufacturing apparatus 100 performs fine building on the both ends of the object to thereby form the object having a highly accurate outer shape. Furthermore, the additive manufacturing apparatus 100 performs rough building on the portion other than the both ends of the object to thereby shorten the machining time of the entire object.

FIG. 12 is a diagram for explaining the shapes of the beads 51 and 52 formed by the additive manufacturing apparatus 100 according to the third embodiment. FIG. 12 illustrates a cross section of the bead 51 and a cross section of the bead 52. These cross sections are cross sections including the direction of travel of the machining head 10 and the central axis CL of the beam nozzle 11.

When a bead width of the bead 51 is represented by “w₁”, a cross-sectional area of the bead 51 is represented by “M₁”, a bead width of the bead 52 is represented by “w₂”, a cross-sectional area of the bead 52 is represented by “M₂”, and heights of the beads 51 and 52 in the direction of the central axis CL are represented by “h”, the following Formulas (2) and (3) are established.

M
1

=

w
1

/
2
×
h
/
2
×
π

(
2
)

M
2

=

w
2

/
2
×
h
/
2
×
π

(
3
)

For example, when h=0.5 mm, w₁=1 mm, and w₂=6 mm, Formulas (2) and (3) give M₁=0.4 mm²and M₂=2.4 mm². The cross-sectional area of the bead 52 is approximately six times the cross-sectional area of the bead 51.

A building speed WFR as the speed at which the bead 51 or the bead 52 is formed by the additive manufacturing apparatus 100 is obtained by the following Formula (4). In Formula (4), “F” represents the speed at which the laser beam 24 is moved by the beam drive unit 20. Moreover, “M_i” (i=1, 2) represents the cross-sectional area M₁of the bead 51 or the cross-sectional area M₂of the bead 52.

WFR
⁡
(

cc
/
h

)

=

F
⁡
(

mm
/
min

)

×

M
i

(

mm
2

)

×
60
⁢

(
min
)

×
1000

(
4
)

Assuming that the speed of movement of the laser beam 24 in fine building is the same as the speed of movement of the laser beam 24 in rough building, the building speed WFR in rough building can be approximately six times the building speed WFR in fine building. The additive manufacturing apparatus 100 applies fine building to the machining of a portion requiring high shape accuracy and applies rough building to the machining of other portions, thereby performing high-speed building of the object while maintaining the shape accuracy.

In order to achieve a high machining speed for the portion subject to rough building, it is necessary to increase the amount of movement of the laser beam 24 and also increase the feed of the wire 5 and the amount of heat input for melting the wire 5. The additive manufacturing apparatus 100 increases the amount of heat input for melting the wire 5 by increasing at least one of the laser power of the laser oscillator 2 and the amount of current flowing from the hot wire power supply 21 to the wire 5. As a result, the additive manufacturing apparatus 100 can sufficiently melt the wire 5, and can achieve the high machining speed for the portion subject to rough building.

Note that also in the third embodiment, the controller 1 may determine the direction in which the laser beam 24 is moved by the beam drive unit 20 on the basis of the direction of travel of the tip portion of the wire 5.

According to the third embodiment, the additive manufacturing apparatus 100 varies the size of the irradiation area 40 at different positions on the reference plane of the workpiece. The additive manufacturing apparatus 100 can switch between fine building and rough building according to the position on the reference plane of the workpiece. For each portion of the object, the additive manufacturing apparatus 100 can set at will to perform either the machining focusing on the shape accuracy or the machining focusing on the machining speed. As a result, the additive manufacturing apparatus 100 can perform high-speed building of the object while maintaining the shape accuracy.

Fourth Embodiment

A fourth embodiment will describe an example of changing the width in which the laser beam 24 is moved back and forth in the irradiation area 40. The configuration of the additive manufacturing apparatus 100 according to the fourth embodiment is similar to the configuration of the additive manufacturing apparatus 100 according to the first embodiment. In the fourth embodiment, the same components as those in the above first to third embodiments are denoted by the same reference numerals as those assigned to such components in the first to third embodiments, and the operation different from that of the first to third embodiments will be mainly described.

FIG. 13 is a diagram illustrating how the laser beam 24 is moved by the additive manufacturing apparatus 100 according to the fourth embodiment. In the fourth embodiment, the beam drive unit 20 makes an irradiation area 55 of the laser beam 24 on the workpiece larger than the spot of the laser beam 24 by moving the laser beam 24 faster than the speed at which the tip portion of the wire 5 is moved. The irradiation area 55 is an example of the irradiation area 40 in the case of changing the width in which the laser beam 24 is moved back and forth. In FIG. 13, an arrow 56 indicates an example of a path in which the laser beam 24 is moved in the irradiation area 55.

In the fourth embodiment, the beam drive unit 20 moves the laser beam 24 back and forth in the irradiation area 55, and also gradually changes the width in which the laser beam 24 is moved back and forth in the irradiation area 55. In the example illustrated in FIG. 13, the beam drive unit 20 reduces the width in which the laser beam 24 is moved back and forth as the laser beam 24 approaches the tip portion of the wire 5. As a result, the irradiation area 55 has a shape in which the width in the direction of moving the laser beam 24 back and forth continuously changes. The additive manufacturing apparatus 100 thus forms the bead 35 having a shape with the width continuously changing.

FIG. 14 is a diagram illustrating a bead 57 formed in the fourth embodiment. FIG. 15 is a diagram illustrating a bead 58 formed in a comparative example of the fourth embodiment. The bead 57 illustrated in FIG. 14 is an example of the bead 35 that is formed in the fourth embodiment and has the shape with the width continuously changing. The bead 58 illustrated in FIG. 15 is a combination of a plurality of line beads, and is formed by a method different from that of the fourth embodiment. The line bead is a linear bead.

In the case of forming the shape with the width continuously changing, the bead 57 illustrated in FIG. 14 achieves higher shape reproducibility than the bead 58 illustrated in FIG. 15. According to the fourth embodiment, the additive manufacturing apparatus 100 gradually changes the width in which the laser beam 24 is moved back and forth in the irradiation area 55, thereby performing building with high shape reproducibility.

Note that, in the fourth embodiment, the path in which the laser beam 24 is moved by the beam drive unit 20 is set as appropriate, whereby the irradiation area 55 can have any desired shape. Also in the fourth embodiment, the controller 1 may determine the direction in which the laser beam 24 is moved by the beam drive unit 20 on the basis of the direction of travel of the tip portion of the wire 5.

Fifth Embodiment

A fifth embodiment will describe an example in which an object is formed with a ball bead. The ball bead is a dotted bead. The configuration of the additive manufacturing apparatus 100 according to the fifth embodiment is similar to the configuration of the additive manufacturing apparatus 100 according to the first embodiment. In the fifth embodiment, the same components as those in the above first to fourth embodiments are denoted by the same reference numerals as those assigned to such components in the first to fourth embodiments, and the operation different from that of the first to fourth embodiments will be mainly described.

FIG. 16 is a diagram illustrating how the object is formed by the additive manufacturing apparatus 100 according to the fifth embodiment. The additive manufacturing apparatus 100 forms the object with a bead 61 that is the ball bead. An arrow 62 indicates that the laser beam 24 is moved by the beam drive unit 20. An arrow 63 indicates the direction of travel of the machining head 10. The beam drive unit 20 as the second drive unit moves the laser beam 24 in a direction included in the reference plane. When the bead 61 is formed, the controller 1 controls the beam drive unit 20 to move the laser beam 24 in the direction included in the reference plane.

FIG. 17 is a first diagram illustrating how the laser beam 24 is moved by the beam drive unit 20 of the additive manufacturing apparatus 100 according to the fifth embodiment. FIG. 17 illustrates an example in which the laser beam 24 is moved in an irradiation area 64 larger than the spot of the laser beam 24 on the substrate 17 that is the workpiece. FIG. 17 schematically illustrates how the laser beam 24 is moved in the irradiation area 64. An arrow 65 illustrated in FIG. 17 indicates a path in which the laser beam 24 is moved in the irradiation area 64. The beam drive unit 20 moves the laser beam 24 to make the irradiation area 64 of the laser beam 24 on the workpiece larger than the spot of the laser beam 24.

In FIG. 17, a plurality of the irradiation areas 64 is lined up in the direction of travel of the machining head 10. Each of the irradiation areas 64 is circular. The bead 61 is formed in each of the irradiation areas 64. As a result, the bead 61 having a circular shape on the reference plane is formed on the workpiece. Note that the additive manufacturing apparatus 100 according to the fifth embodiment is not limited to forming the entire object with the ball bead. The additive manufacturing apparatus 100 need only form the ball bead included in the object in at least a part of the object.

FIG. 18 is a second diagram illustrating how the laser beam 24 is moved by the beam drive unit 20 of the additive manufacturing apparatus 100 according to the fifth embodiment. FIG. 18 illustrates an example in which the laser beam 24 is moved in an irradiation area 66 having a shape different from that of the irradiation area 64 illustrated in FIG. 17. FIG. 18 schematically illustrates how the laser beam 24 is moved in the irradiation area 66. An arrow 67 illustrated in FIG. 18 indicates a path in which the laser beam 24 is moved in the irradiation area 66.

In FIG. 18, a plurality of the irradiation areas 66 is lined up in the direction of travel of the machining head 10. Each of the irradiation areas 66 is elliptical. The bead 61 is formed in each of the irradiation areas 66. As a result, the bead 61 having an elliptical shape on the reference plane is formed on the workpiece. As described above, the additive manufacturing apparatus 100 sets the shapes of the irradiation areas 64 and 66 as appropriate to thereby form the bead 61 having any desired shape.

Next, the formation of the ball bead by the additive manufacturing apparatus 100 according to the fifth embodiment will be described. Here, a description of how the ball bead is formed by the additive manufacturing apparatus 100 will be made for each step. Through the steps, the additive manufacturing apparatus 100 forms the ball bead on the substrate 17 as the workpiece.

FIG. 19 is a diagram for explaining a first step of forming the ball bead by the additive manufacturing apparatus 100 according to the fifth embodiment. In the first step, the additive manufacturing apparatus 100 moves the machining head 10 to align the central axis CL of the laser beam 24 with the center of the machining area 34.

FIG. 20 is a diagram for explaining a second step of forming the ball bead by the additive manufacturing apparatus 100 according to the fifth embodiment. In the second step, the additive manufacturing apparatus 100 sends the wire 5 from the wire nozzle 12 to the machining area 34 and brings the tip portion of the wire 5 into contact with the surface 32 of the substrate 17. The central axis CL of the beam nozzle 11 and the central axis CW of the wire 5 intersect at the surface 32.

FIG. 21 is a diagram for explaining a third step of forming the ball bead by the additive manufacturing apparatus 100 according to the fifth embodiment. The additive manufacturing apparatus 100 emits the laser beam 24 toward the machining area 34. The beam drive unit 20 moves the laser beam 24 in the irradiation area 64 or 66.

With the emission of the laser beam 24, the additive manufacturing apparatus 100 starts ejection of the inert gas 25 from the gas nozzle 13 to the machining area 34. The additive manufacturing apparatus 100 may eject the inert gas 25 at a predetermined time before starting the emission of the laser beam 24. This allows the additive manufacturing apparatus 100 to remove active gas such as oxygen remaining in the gas nozzle 13 from the gas nozzle 13, and then start the ejection of the inert gas 25.

FIG. 22 is a diagram for explaining a fourth step of forming the ball bead by the additive manufacturing apparatus 100 according to the fifth embodiment. The additive manufacturing apparatus 100 feeds the wire 5 from the wire nozzle 12 toward the surface 32. Accordingly, the additive manufacturing apparatus 100 starts feeding the wire 5 to the machining area 34.

By the irradiation with the laser beam 24, the molten pool 33 is formed at the portion of the surface 32 in the machining area 34. The melt 31 of the wire 5 is placed on the molten pool 33. The melt 31 and the molten pool 33 are integrated together and solidified to form the bead 61 joined to the substrate 17. The additive manufacturing apparatus 100 continues to feed the wire 5 for a predetermined feed time after starting to feed the wire 5 to the machining area 34. The additive manufacturing apparatus 100 adjusts the feed rate of the wire 5 by adjusting the rotational speed of the rotary motor 4. There is a correlation between the feed rate of the wire 5 and the laser power for achieving proper welding of the melt 31. On the basis of such a correlation, the feed rate of the wire 5 is limited to a certain level by the laser power.

Increasing the laser power of the laser oscillator 2 can shorten the time required for forming the bead 61. Note that when the feed rate of the wire 5 is too fast for the laser power, the wire 5 remains unmelted. Also, when the feed rate of the wire 5 is slow for the laser power, the wire 5 is excessively heated so that a droplet, which is the melt 31, falls from the wire 5. When the droplet falls, the melt 31 may solidify into a shape different from a desired shape of the bead 61. The additive manufacturing apparatus 100 properly adjusts the feed rate of the wire 5 to thereby prevent the situation where the wire 5 remains unmelted or the situation where the droplet falls.

The size of the bead 61 is adjusted by changing at least one of the feed time of the wire 5, the irradiation time for continuing the irradiation with the laser beam 24, and the amount of movement of the laser beam 24. The additive manufacturing apparatus 100 increases the feed time of the wire 5, increases the irradiation time with the laser beam 24, or increases the amount of movement of the laser beam 24, thereby increasing the diameter of the bead