Patent Description:
In recent years, needs for 3D printers as a means of production have been increasing, and especially as for application to metal materials, research and development have been carried out for practical use in the aircraft industry and the like. A 3D printer using a metal material is configured to melt a metal powder or a metal wire by using a heat source such as a laser or an arc, and deposit the molten metal to manufacture an additively-manufactured object.

As a technique for manufacturing such an additively-manufactured object by welding, Patent Literature <NUM> discloses that a contour portion and a fill portion surrounded by the contour portion are built under different welding conditions.

Patent Literature <NUM> describes a method of adjusting a target position of a welding torch, a welding current, a welding voltage, and the like by measuring a shape of a weld bead that is already welded with a laser sensor in real time, and selecting a welding condition from a database according to the measured bead shape when an iron column for construction is welded.

Further, Non-Patent Literature <NUM> describes a method of adjusting a height and width of a weld bead to be formed, by controlling a welding voltage and a travel speed according to a bead shape measured by a laser sensor in additive manufacturing using a welding wire.

<CIT> (describing the preamble of claim <NUM>) shows methods and systems for hybrid deposition rate near net shape additive manufacturing. <CIT> describes a method and an apparatus for manufacturing a layered product. <NPL>, describe a layers-overlapping strategy for robotic wire and arc additive manufacturing of multi-layer multi-bead components with homogeneous layers. <CIT> describes a manufacturing method of layered objects. <CIT> describes printing a layer in response to a substrate contour.

In a building method of building in advance an outer frame constituted by a contour portion and filling an inner side of the outer frame as in Patent Literature <NUM>, it is conceivable to perform feedback control of a bead formation position, a welding condition, or the like in a next step while measuring a shape of a formed weld bead by a shape sensor as in Patent Literature <NUM> and Non-Patent Literature <NUM>.

However, in this case, when a shape in the vicinity of the outer frame constituted by the contour portion is measured by the shape sensor, a shape of a region in which the weld bead is deposited in the area surrounded by the outer frame may not be measured by the shape sensor due to the outer frame becoming an obstacle. Thus, it may be difficult to form the weld bead while performing correction in real time by the feedback control, and a depositing accuracy of the weld bead may be reduced.

Accordingly, an object of the present invention is to provide a method for manufacturing an additively-manufactured object, by which a high-quality additively-manufactured object can be manufactured by depositing weld beads with a high accuracy based on a measurement result obtained by a shape sensor.

The present invention provides a method as defined in appended independent claim <NUM>. Specific embodiments thereof are defined in the appended dependent claims.

In the present invention, it is possible to manufacture a high-quality additively-manufactured object by depositing weld beads with a high accuracy based on a measurement result obtained by a shape sensor.

<FIG> is a configuration diagram of a manufacturing system used for manufacturing an additively-manufactured object in the present invention.

A manufacturing system <NUM> for the additively-manufactured object in this configuration includes an additive manufacturing device <NUM>, a controller <NUM> that integrally controls the additive manufacturing device <NUM>, and a power supply device <NUM>.

The additive manufacturing device <NUM> includes a welding robot <NUM> in which a torch <NUM> is provided on a tip shaft thereof, and a filler metal supply unit <NUM> that supplies a filler metal (a welding wire) M to the torch <NUM>. A shape sensor <NUM> is provided together with the torch <NUM> on the tip shaft of the welding robot <NUM>.

The welding robot <NUM> is a multi-joint robot, and the filler metal M is supported by the torch <NUM> attached to the tip shaft of a robot arm so as to be continuously suppliable. A position and posture of the torch <NUM> can be set three-dimensionally desirably within a movable range of the robot arm.

The torch <NUM> includes a shield nozzle (not shown), and a shielding gas is supplied from the shield nozzle. An arc welding method may be either a consumable electrode-based method such as shielded metal arc welding method or carbon dioxide gas arc welding method, or a non-consumable electrode-based method such as TIG welding method or plasma arc welding method, and is appropriately selected depending on an additively-manufactured object to be manufactured.

For example, in the case of the consumable electrode-based method, a contact tip is disposed inside the shield nozzle, and the contact tip holds the filler metal M to which a melting current is supplied. The torch <NUM> generates an arc from a 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 supply unit <NUM> to the torch <NUM> by a delivery mechanism (not shown) attached to the robot arm or the like. Then, when the filler metal M fed continuously is melted and solidified while the torch <NUM> is moved, a linear weld bead B, which is a melt-solidified body of the filler metal M, is formed on a base plate <NUM>, and an additively-manufactured object W composed of the weld bead B is manufactured.

As shown in <FIG>, the shape sensor <NUM> is arranged in parallel with the torch <NUM>, and is configured to be moved together with the torch <NUM>. The shape sensor <NUM> is a sensor that measures a shape of a portion serving as a base when the weld bead B is formed. As the shape sensor <NUM>, for example, a laser sensor that acquires reflected light of emitted laser light as height data is used. As the shape sensor <NUM>, a three-dimensional shape measuring camera may be used.

The controller <NUM> includes a CAD/CAM unit <NUM>, a trajectory calculation unit <NUM>, a storage unit <NUM>, a deviation amount calculation unit <NUM>, a correction unit <NUM>, and a control unit <NUM> to which these units are connected.

The CAD/CAM unit <NUM> receives or creates shape data (CAD data and the like) of the additively-manufactured object W to be manufactured.

The trajectory calculation unit <NUM> divides a shape model of three-dimensional shape data into a plurality of weld bead layers according to a height of the weld bead B. Then, for each layer of the divided shape model, a depositing plan which defines a trajectory of the torch <NUM> for forming the weld bead B, and heating conditions (including welding conditions and the like for obtaining a bead width, a bead depositing height, and the like) for forming the weld bead B is created.

The deviation amount calculation unit <NUM> compares the depositing plan created by the trajectory calculation unit <NUM> with a measured value obtained by the shape sensor <NUM>. Then, the deviation amount calculation unit <NUM> calculates a deviation amount between a shape based on the depositing plan and a shape based on the measured value in the portion serving as the base when the weld bead B is formed.

The correction unit <NUM> corrects, based on the deviation amount calculated by the deviation amount calculation unit <NUM>, a welding condition based on the depositing plan for forming the weld bead B.

The control unit <NUM> drives the welding robot <NUM>, the power supply device <NUM>, and the like by executing a drive program stored in the storage unit <NUM>. That is, the welding robot <NUM> moves the torch <NUM> in response to a command from the controller <NUM> and melts the filler metal M with an arc to form the weld bead B on the base plate <NUM>.

The base plate <NUM> is made of a metal plate such as a steel plate, and is basically larger than a bottom surface (a surface of a lowermost layer) of the additively-manufactured object W. The base plate <NUM> is not limited to a plate shape, and may be a base of another shape such as a block body or a rod body.

Any commercially available welding wire can be used as the filler metal M. For example, a wire specified by solid wires for MAG and MIG welding of mild steel, high tensile strength steel, and low temperature service steel (JISZ <NUM>), flux-cored wires for arc welding of mild steel, high tensile strength steel, and low temperature service steel (JISZ <NUM>), or the like can be used.

Next, an example of an additively-manufactured object manufactured by the manufacturing method in the present embodiment is described.

<FIG> is a schematic cross-sectional view of the additively-manufactured object W as an example of the additively-manufactured objects W.

As shown in <FIG>, the additively-manufactured object W includes a frame portion <NUM> built by depositing weld beads B1 on the base plate <NUM>. Further, the additively-manufactured object W includes an internal building portion <NUM> built by weld beads B2 in the area surrounded by the frame portion <NUM>. The internal building portion <NUM> is formed by depositing weld bead layers BL each constituted by the weld beads B2.

Next, a case of manufacturing the additively-manufactured object W is described.

The filler metal M is melted while the torch <NUM> of the additive manufacturing device <NUM> is moved by the driving of the welding robot <NUM>. Then, the weld beads B1 made of the molten filler metal M are supplied and deposited on the base plate <NUM>, and the frame portion <NUM> which has a substantially rectangular shape in a plan view and is constituted by the weld beads B1 deposited on the base plate <NUM> is built.

The weld beads B2 are formed in the area surrounded by the frame portion <NUM>. Then, the weld beads B2 are formed in a width direction in the area surrounded by the frame portion <NUM>. Accordingly, the weld bead layers BL each constituted by a plurality of weld beads B2 formed in parallel are formed in the area surrounded by the frame portion <NUM>. Then, the weld bead layers BL are deposited in the area surrounded by the frame portion <NUM> to build the internal building portion <NUM>.

In this manufacturing method, the internal building portion <NUM> is built in the area surrounded by the frame portion <NUM> after the building of the frame portion <NUM>, and thus the internal building portion <NUM> can be efficiently built by the weld bead B2 having a large cross-sectional area.

However, as shown in <FIG>, when the weld bead layers BL each constituted by the weld beads B2 are deposited in order to build the internal building portion <NUM> in the area surrounded by the frame portion <NUM>, for example, valley-like recesses may be formed in a boundary portion between the weld beads B2 each constituting a first weld bead layer BL, and an upper surface of the first weld bead layer BL may have an uneven shape. That is, when a second weld bead layer BL that is an upper layer is built, a shape of the upper surface of the first weld bead layer BL that is a base of the weld bead layer BL may deviate from the shape based on the depositing plan. Thus, even if the second weld bead layer BL is built on the first weld bead layer BL in accordance with the depositing plan, the additively-manufactured object W having a target shape may not be manufactured.

In this case, when the weld beads B2 constituting the internal building portion <NUM> are formed, a shape of the base may be measured in real time, and a measurement result may be fed back to correct the welding condition of the weld beads B2. However, as shown in <FIG>, when the shape of the base is measured by the shape sensor <NUM> in the vicinity of the frame portion <NUM>, the frame portion <NUM> is an obstacle, the shape cannot be measured by the shape sensor <NUM>, and it is difficult to perform feedback control in real time.

Therefore, in the present embodiment, when the weld bead layer BL is built in order to manufacture the additively-manufactured object W having the target shape, a shape pre-measurement process, a deviation amount calculation process, and a pre-correction process, which are described below, are performed. Here, a case where the second weld bead layer BL is built is described as an example.

<FIG> is a schematic perspective view of the additively-manufactured object W in the middle of manufacturing and shows the shape pre-measurement process. <FIG> is a schematic perspective view of the additively-manufactured object W in the middle of manufacturing and shows an application example of the shape pre-measurement process. <FIG> illustrate diagrams showing the additively-manufactured object W in the middle of building based on the measured value, and <FIG> is a schematic cross-sectional view of the additively-manufactured object W and <FIG> is a schematic diagram showing a measured profile RP. <FIG> illustrate diagrams showing the additively-manufactured object W in the middle of building based on the depositing plan, and <FIG> is a schematic cross-sectional view of the additively-manufactured object W and <FIG> is a schematic diagram showing a planned profile PP. <FIG> illustrates diagrams showing the pre-correction process, and <FIG> is a schematic diagram showing a result of combining the measured profile RP and the planned profile PP, and <FIG> is a schematic diagram showing cross sectional shapes of the weld beads B2 constituting the second weld bead layer BL corrected in consideration of a deviation amount. <FIG> is a schematic cross-sectional view of the additively-manufactured object W manufactured through the pre-correction process.

After the building of the frame portion <NUM> performed by the frame portion building step and the first weld bead layer BL is built by the internal building step (see <FIG>), the shape pre-measurement process for measuring a shape of the additively-manufactured object in the middle of the building is performed before the building of the second weld bead layer BL, as shown in <FIG>. In the shape pre-measurement process, the welding robot <NUM> is driven to move the shape sensor <NUM> arranged in parallel with the torch <NUM> along a planned building portion of the second weld bead layer BL. Then, the shape sensor <NUM> measures a shape along a formation direction of the weld beads B2. The shape may be measured by the shape sensor <NUM> in a direction different from a direction along the formation direction of the weld beads B2. At this time, the shape sensor <NUM> interferes with the frame portion <NUM> that is already built, and thus it may be difficult to measure a shape of an inner edge portion of the frame portion <NUM>. In such a case, as shown in <FIG>, the shape sensor <NUM> is inclined inward relative to the frame portion <NUM>, and a measurement range of the shape sensor <NUM> is directed to an inner side of the frame portion <NUM>. Accordingly, it is possible to satisfactorily measure a shape of the inner side of the frame portion <NUM> while the measurement performed by the shape sensor <NUM> is avoided from being blocked by the frame portion <NUM> itself.

<FIG> shows a cross sectional shape of the additively-manufactured object in the middle of the building based on the measured value obtained by the shape sensor <NUM>. In the cross-sectional shape based on the measured value, a region S1 in <FIG> is a cross sectional shape of the second weld bead layer BL to be deposited. Then, as shown in <FIG>, the measured profile RP of the additively-manufactured object in the middle of the building is created based on the cross-sectional shape based on the measured value.

The deviation amount calculation unit <NUM> compares the measured profile of the additively-manufactured object in the middle of the building created based on the measured value obtained by the shape sensor <NUM> with the planned profile of the additively-manufactured object in the middle of the building based on the depositing plan, and calculates a deviation amount of the measured profile with respect to the planned profile.

<FIG> shows a cross sectional shape of the additively-manufactured object in the middle of the building based on the depositing plan.

In the cross-sectional shape based on the depositing plan, a region S2 in <FIG> is a cross sectional shape of the second weld bead layer BL to be deposited. Then, as shown in <FIG>, the planned profile PP of the additively-manufactured object in the middle of the building is created based on the cross-sectional shape in the depositing plan.

As shown in <FIG>, the deviation amount calculation unit <NUM> compares the measured profile RP with the planned profile PP, determines deviation regions S3 (hatched portions in <FIG>) of the measured profile RP with respect to the planned profile PP, and calculates a deviation amount which is a cross sectional area of the deviation region S3. The deviation amount calculation unit <NUM> calculates the deviation amount and determines a deviation position.

Next, based on the deviation amount and the deviation position between the planned profile PP and the measured profile RP, the correction unit <NUM> executes the pre-correction process of correcting the welding condition of the weld beads B2 for building the second weld bead layer BL. Specifically, as shown in <FIG>, the correction unit <NUM> corrects the welding condition of the weld beads B2 such that a surface of the second weld bead layer BL is formed in accordance with the depositing plan, in consideration of the deviation amount and the deviation position between the planned profile PP and the measured profile RP. In the present example, a cross sectional area of the actually built first weld bead layer BL is smaller than that of the planned first weld bead layer BL based on the depositing plan. In this case, the welding condition is corrected so as to increase a cross sectional area of the weld beads B2 constituting the second weld bead layer BL. When the cross-sectional area of the actually built first weld bead layer BL is larger than that of the planned first weld bead layer BL based on the depositing plan, the welding condition is corrected so as to decrease the cross-sectional area of the weld beads B2 constituting the second weld bead layer BL. The correction of the welding condition for increasing or decreasing the cross-sectional area of the weld beads B2 is performed by adjusting a travel speed, a supply amount of the filler metal M, or a welding current during forming the weld beads B2. This correction is preferably performed by, for example, searching a database of welding conditions stored in advance for a welding condition of weld beads having a cross sectional area that covers excess or shortage.

Thereafter, as shown in <FIG>, the weld beads B2 are formed on the first weld bead layer BL under the corrected welding condition, and the second weld bead layer BL is built. Thus, the deviation between the planned profile PP and the measured profile RP is compensated, and an upper surface of the second weld bead layer BL constituted by the weld beads B2 formed under the corrected welding condition is approximated to the shape based on the depositing plan.

As described above, according to the method for manufacturing an additively-manufactured object in the present embodiment, the frame portion <NUM> is built, and the internal building portion <NUM> is built in the area surrounded by the frame portion <NUM>, and thus the internal building portion <NUM> can be efficiently built by the weld beads B2 having a large cross sectional area, for example. As described above, in the method for manufacturing the additively-manufactured object W in which the internal building portion <NUM> is built in the area surrounded by the frame portion <NUM>, the shape of the base on which the weld bead layer BL is to be deposited is measured to create the measured profile RP, the planned profile PP of the base is determined based on the depositing plan, and the deviation amount of the measured profile RP with respect to the planned profile PP is calculated. When the weld bead layer BL is deposited on the base in the area surrounded by the frame portion <NUM>, the welding condition for the weld beads B2 constituting the weld bead layer BL in the depositing plan is corrected in order to reduce the deviation amount. Therefore, even if the shape of the base in the area surrounded by the frame portion <NUM> deviates from the planned profile PP determined based on the depositing plan, the weld bead layer BL constituted by the weld beads B2 deposited on the base can be approximated to a shape in the depositing plan. Accordingly, even if it is difficult to form the weld beads B2 while measuring the shape of the base in real time and performing the feedback control because of a presence of the frame portion <NUM>, it is possible to satisfactorily build the internal building portion <NUM> based on the depositing plan.

The shape sensor <NUM> which measures the shape of the base is arranged in parallel with the torch <NUM> that is moved based on the depositing plan, and thus the trajectory of the torch <NUM> based on the depositing plan can be used for a measurement operation performed by the shape sensor <NUM>. Accordingly, it is possible to easily measure the shape of the base by the shape sensor <NUM> without creating a trajectory program for moving the shape sensor <NUM>.

In addition, when the shape sensor <NUM> is arranged in parallel with the torch <NUM>, it is also possible to satisfactorily measure a shape of a portion in the vicinity of the inner side of the frame portion <NUM> while preventing the interference of the shape sensor <NUM> with the frame portion <NUM> by measuring the shape by inclining the shape sensor <NUM> inward relative to the frame portion <NUM>.

In the internal building step of building the internal building portion <NUM>, for example, at a center position away from the frame portion <NUM> where the measurement of the shape is not obstructed by the frame portion <NUM>, the welding condition for the weld bead B2 may be corrected in real time depending on the shape of the base. Specifically, a real-time correction process may be performed by measuring the shape of the base by the shape sensor <NUM> arranged in parallel with the torch <NUM>, and forming the weld beads B2 by the torch <NUM> while correcting the welding condition for the weld beads B2 based on the depositing plan in real time based on a measured shape of the base.

As described above, in the internal building step, the real-time correction process is performed at a position where the measurement of the shape is not obstructed by the frame portion <NUM> together with the pre-correction process, and thus the internal building portion <NUM> in the area surrounded by the frame portion <NUM> can be built satisfactorily and more efficiently.

In a pre-measurement process, the inner side of the frame portion <NUM>, the inner side including the frame portion <NUM>, where it is difficult to measure the shape in real time and perform the feedback control in real time, is measured along the frame portion <NUM> in advance. Therefore, it is possible to efficiently measure a shape of a specific portion of the base and perform the pre-correction process as compared with a case where a shape of an entire range in the area surrounded by the frame portion <NUM> is measured in advance.

In a case where at least three weld bead layers BL are deposited in the area surrounded by the frame portion <NUM>, it is preferable to perform the shape pre-measurement process, the deviation amount calculation process, and the pre-correction process when third and subsequent weld bead layers BL are built. In addition, when the first weld bead layer BL is built, a shape of the base plate <NUM> serving as a base of the first weld bead layer BL may be measured, and the deviation amount calculation process and the pre-correction process may be performed.

As described above, the present invention is not limited to the above embodiments, and combinations of the respective configurations in the embodiments, and changes and applications made by those skilled in the art based on the description of the specification and the common technology are also intended by the present invention and are included within the scope to be protected.

According to the method for manufacturing the additively-manufactured object as defined in appended claim <NUM>, the frame portion is built, and the internal building portion is built in the area surrounded by the frame portion, and thus the internal building portion can be efficiently built by the weld beads having a large cross-sectional area, for example. As described above, in the method for manufacturing the additively-manufactured object in which the internal building portion is built in the area surrounded by the frame portion, the shape of the base on which the weld bead layer is to be deposited is measured to create the measured profile, the planned profile of the base is determined based on the depositing plan, and the deviation amount of the measured profile with respect to the planned profile is calculated. When the weld bead layer is deposited on the base in the area surrounded by the frame portion, the welding condition for the weld beads constituting the weld bead layer in the depositing plan is corrected in order to reduce the deviation amount. Therefore, even if the shape of the base in the area surrounded by the frame portion deviates from the planned profile determined based on the depositing plan, the weld bead layer constituted by the weld beads deposited on the base can be approximated to a shape in the depositing plan. Accordingly, even if it is difficult to form the weld beads while measuring the shape of the base in real time and performing feedback control in real time because of a presence of the frame portion, it is possible to satisfactorily build the internal building portion based on the depositing plan.

According to the method for manufacturing the additively-manufactured object as defined in appended claim <NUM>, the shape sensor is arranged in parallel with the torch that is moved based on the depositing plan, and thus a trajectory of the torch based on the depositing plan can be used for a measurement operation performed by the shape sensor. Accordingly, it is possible to easily measure the shape of the base by the shape sensor.

According to the method for manufacturing the additively-manufactured object as defined in appended claim <NUM>, the shape is measured while inclining the shape sensor inward relative to the frame portion. Accordingly, it is possible to satisfactorily measure a shape of a portion in the vicinity of an inner side of the frame portion while preventing interference of the shape sensor with the frame portion.

According to the method for manufacturing the additively-manufactured object as defined in appended claims <NUM> and <NUM>, the real-time correction process is performed together with the pre-correction process when the internal building portion is built in the area surrounded by the frame portion. That is, at a position where the measurement of the shape is not obstructed by the frame portion, the welding condition for the weld beads is corrected in real time according to the shape of the base. Accordingly, the internal building portion in the area surrounded by the frame portion can be built satisfactorily and more efficiently.

Claim 1:
A method for manufacturing an additively-manufactured object by depositing weld beads (B, B1, B2) obtained by melting and solidifying a filler metal, the method comprising:
a depositing planning step of creating a depositing plan for depositing the weld beads (B, B1, B2) based on a target shape of the additively-manufactured object; and
a building step of repeatedly depositing the weld beads (B, B1, B2) based on the depositing plan, wherein
the building step comprises:
a frame portion building step of building a frame portion by a first plurality of the weld beads (B1); and
an internal building step of building an internal building portion in which a weld bead layer including a second plurality of the weld beads (B2) formed in parallel in an area surrounded by the frame portion is deposited, and
characterised in that the internal building step comprises:
a pre-measurement process of measuring a shape of a base on which the weld bead layer is to be deposited;
a deviation amount calculation process of creating a measured profile of the base based on the measured shape of the base, determining a planned profile of the base based on the depositing plan, and calculating a deviation amount of the measured profile with respect to the planned profile; and
a pre-correction process of correcting a welding condition of the second plurality of the weld beads (B2) constituting the weld bead layer in the depositing plan in order to reduce the deviation amount when the weld bead layer is deposited on the base; and
wherein in the pre-measurement process, a shape of an inner side of the frame portion, the inner side including the frame portion, is measured along the frame portion.