Patent Description:
In recent years, there is growing need for 3D printers as production means, and researches and developments have been made in the field of airplanes, etc. in order to practically apply 3D printers to, in particular, metallic materials. For example, a 3D printer employing a metallic material melts the metal powder or metal wire using a heat source such as a laser or an arc, and deposits the molten metal, thereby producing a built-up object.

As a technique for producing such a built-up object, there is a common technique including a torch scanning step in which a torch is moved in a scanning manner along a horizontal plane or an inclined plane to perform overlay welding, thereby producing a three-dimensional shaped object (see, for example, Patent Literature <NUM>).

Patent Literature <NUM>: <CIT>
<CIT> (disclosing the preamble of claims <NUM> and <NUM>) describes a method and apparatus for building up lines or layers of metal by fusion arc welding and particularly by submerged-arc welding.

Meanwhile, in a case of forming a weld bead on a base surface of either a substrate or lower-layer weld beads and the base surface being inclined, there is a possibility that dripping might occur due to the influence of gravity. In a case where the travelling speed of the welding torch is heightened in order to avoid the dripping of the weld bead, there is a possibility that humping in which the weld bead breaks might occur. There is hence a desire for a technique for producing a built-up object by smoothly forming weld beads without being influenced by the state of the base surface on which the weld beads are being formed and without arousing any trouble such as dripping or humping.

An object of the present invention is to provide a method and an apparatus for producing a built-up object which are capable of producing a built-up object by efficiently forming weld beads without arousing any trouble such as dripping or humping.

The subject matter of the present invention is defined in the appended set of claims.

In the present invention, a built-up object can be produced by efficiently forming weld beads without arousing any trouble such as dripping or humping.

Embodiments of the present invention are described below in detail by reference to the drawings.

<FIG> is a schematic view illustrating the configuration of a production system for producing a built-up object in accordance with the present invention.

The production system <NUM> having this configuration includes: an additively manufacturing device <NUM>; and a controller <NUM> configured to control the whole additively manufacturing device <NUM>.

The additively manufacturing device <NUM> includes: a welding robot <NUM> having a torch <NUM> provided to an end shaft thereof; and a filler-metal feed part <NUM> configured to feed a filler metal (welding wire) M to the torch <NUM>.

The controller <NUM> includes: a CAD/CAM unit <NUM>; a track computing unit <NUM>; a memory unit <NUM>; and a control unit <NUM> to which these units have been connected.

The welding robot <NUM> is an articulated robot, and the filler metal M is supported by the torch <NUM> provided to the end shaft, such that the filler metal M can be continuously fed thereto. The position and posture of the torch <NUM> can be arbitrarily set three-dimensionally within the range over which the robot arm is movable.

The torch <NUM> includes a shield nozzle (not shown), and a shielding gas is supplied from the shield nozzle. Arc welding to be used in this configuration may be either a consumable-electrode method, such as shielded-metal arc welding or carbon dioxide gas arc welding, or a non-consumable-electrode method, such as TIG welding or plasma arc welding. An appropriate arc welding method is selected depending on the built-up object W to be produced.

For example, in the case of a consumable-electrode method, a contact tip is disposed inside the shield nozzle, and a filler metal M to which a melting current is supplied is held by the contact tip. The torch <NUM>, while holding the filler metal M, generates an arc from the end of the filler metal M in a shielding gas atmosphere. The filler metal M is fed from the filler-metal feed part <NUM> to the torch <NUM> by a feeding mechanism (not shown) attached to the robot arm, or the like. The continuously fed filler metal M is melted and solidified while the torch <NUM> is moved, thereby forming a linear weld bead <NUM>, which is a solid formed by melting and solidifying the filler metal M, on a base plate <NUM>.

Heat sources for melting the filler metal M are not limited to the arc. For example, a method employing other heat source(s), such as a heating method in which an arc and a laser are used in combination, a heating method in which a plasma is used, or a heating method in which an electron beam or a laser is used, may be employed. In the case of heating with an electron beam or a laser, the quantity of applied heat can be more finely controlled to more properly maintain the state of the weld bead, thereby contributing to a further improvement in the quality of the additively-manufactured object.

The CAD/CAM unit <NUM> produces profile data on the built-up object W to be produced and then divides the profile data into data for each of a plurality of layers to produce layer profile data representing the profile of each layer. The track computing unit <NUM> determines a movement track for the torch <NUM> based on the produced layer profile data. The data, including the produced layer profile data and the movement track for the torch <NUM>, are stored in the memory unit <NUM>.

The control unit <NUM> executes a driving program based on the layer profile data and the movement track for the torch <NUM>, which are stored in the memory unit <NUM>, to operate the welding robot <NUM>.

The control unit <NUM> executes a driving program based on the layer profile data and the movement track for the torch <NUM>, which are stored in the memory unit <NUM>, to operate the welding robot <NUM>. That is, the welding robot <NUM>, in accordance with a command from the controller <NUM>, moves the torch <NUM> while melting the filler metal M with an arc, based on the movement track for the torch <NUM> produced by the track computing unit <NUM>. <FIG> shows how a built-up object W is produced by obliquely disposing a plurality of weld beads <NUM> on a base plate <NUM> constituted of a steel plate inclined with respect to the vertical plane.

The production system <NUM> having the configuration described above melts the filler metal M while moving the torch <NUM> by the welding robot <NUM> along the movement track for the torch <NUM> produced from the set layer profile data and feeds the molten filler metal M to the surface of the base plate <NUM>. Thus, for example as illustrated in <FIG> and <FIG>, a plurality of linear weld beads <NUM> are formed and obliquely arranged on the base plate <NUM> inclined with respect to the vertical plane, thereby producing a built-up object W including a plurality of layers of the thus deposited weld beads.

Meanwhile, in a case where a torch <NUM> is moved obliquely to the vertical direction to form a weld bead <NUM> on a base plate <NUM> inclined with respect to the vertical plane as illustrated in (a) and (b) of <FIG>, there is a possibility that the weld bead <NUM> being formed might drip due to the influence of gravity. This gravitational influence is greater as the angle (base-surface inclination angle) θ formed by the base surface, which is the surface of the base plate <NUM>, and the vertical direction becomes smaller, and is greater as the angle (track inclination angle) ϕ formed by the track direction of the torch <NUM> and the vertical direction over the base plate 41becomes larger. In a case where the weld bead <NUM> being formed thus undergoes a considerable gravitational influence, although the dripping can be inhibited by increasing the travelling speed V of the torch <NUM>, humping in which the weld bead <NUM> breaks might occur.

Because of this, in this embodiment, a built-up object W is produced while dripping and humping in weld beads <NUM> are prevented in the manner described below. Here, the explanation is made for a case in which a base plate <NUM> inclined with respect to the vertical plane such that the base-surface inclination angle θ is less than <NUM>° is used and weld beads <NUM> are formed on the base plate <NUM> along a track direction inclined with respect to the vertical direction at a track inclination angle ϕ, thereby producing a built-up object W including two deposited layers of weld beads <NUM>. The built-up object W in this case has a bead formation portion where a gravitational influence is maximum.

In a case of forming a plurality of weld beads <NUM> to produce a first layer of a built-up object W, a portion where a gravitational influence is maximum, in the portion where the plurality of weld beads <NUM> are to be formed, is determined first. In determining the portion where a gravitational influence is maximum, the base-surface inclination angle θ, which is the angle between the base plate <NUM> on which weld beads <NUM> are to be formed and the vertical plane, and the track inclination angle ϕ, which is the angle between the track direction of the torch <NUM> for forming weld beads <NUM> and the vertical direction on the base plate <NUM>, are used as indexes of gravitational influence to determine that portion. In particular, cosθsinϕ is used for the determination.

In a case where a built-up object W is produced by forming weld beads <NUM> on a base plate <NUM> inclined at a base-surface inclination angle θ along a track direction inclined with respect to the vertical direction at a track inclination angle ϕ, a lower-end portion is the portion where a gravitational influence is maximum in the first layer.

After the portion where a gravitational influence is maximum in the portion where weld beads <NUM> are to be formed has been determined, a supporting bead 25A is formed as a weld bead <NUM> in this portion. This supporting bead 25A is a low-heat-input bead formed with a reduced heat input for melting the filler metal. Since this supporting bead 25A is a low-heat-input bead, the supporting bead 25A has higher molten-state viscosity during bead formation and is less affected by gravity than weld beads <NUM> to be deposited thereafter. That is, even when this supporting bead 25A is formed in the portion where a gravitational influence is maximum, dripping due to gravity is prevented.

In this example, in forming the supporting bead 25A, a travelling speed V and a current value I for arc generation of the torch <NUM> are determined, for example, from a process window PW, which indicates a set region, having been produced beforehand and stored in the memory unit <NUM>.

(a) and (b) of <FIG> illustrate process windows PWs indicating the travelling speed V and the current value I for arc generation of the torch <NUM> in a case where a base plate <NUM> is disposed vertically such that a base-surface inclination angle θ is <NUM>°. As illustrated in (a) and (b) of <FIG>, the process windows PWs regarding travelling speed V and current value I gradually become narrower as the track inclination angle ϕ increases, because the gravitational influence becomes greater. The control unit <NUM> determines a travelling steed V and a current value I for forming the supporting bead 25A, based on the process window PW stored in the memory unit <NUM>.

After determining the travelling speed V and the current value I, the control unit <NUM> operates the welding robot <NUM> to form the supporting bead 25A at the determined travelling speed V and current value I in the lower-end portion, where a gravitational influence is maximum, along a movement track which has been produced, as illustrated in (a) and (b) of <FIG>. This supporting bead 25A, which is a low-heat-input bead, is high in viscosity during bead formation and can be less affected by gravity. Consequently, the supporting bead 25A, which is a low-heat-input bead, can be formed on the base plate <NUM> without dripping due to gravity even in the portion where the gravitational influence is maximum.

Thereafter, other weld beads <NUM> in the first layer are successively formed on the upper side of the already formed supporting bead 25A on the surface of the base plate <NUM>. In forming these other weld beads <NUM>, a weld bead <NUM> is first formed on the upper side of the already formed supporting bead 25A in a portion of the surface of the base plate <NUM> which adjoins the supporting bead 25A, as illustrated in (a) and (b) of <FIG>. As a result, the weld bead <NUM> formed so as to adjoin the already formed supporting bead 25A is supported by the already formed supporting bead 25A. Consequently, even when this weld bead <NUM> is a high-heat-input bead which has low viscosity during bead formation and can hence drip due to a gravitational influence, this weld bead <NUM> is supported by the supporting bead 25A and formed. Thus, dripping is inhibited in forming this weld bead <NUM>. Furthermore, as illustrated in (a) and (b) of <FIG>, other weld beads <NUM> are successively formed on the upper side of the formed weld bead <NUM> so as to adjoin the formed weld bead <NUM>. In this operation, since the weld beads <NUM> being formed are supported by the underlying weld bead <NUM> which has been formed, dripping is inhibited in forming these weld beads <NUM>.

In a case where a plurality of weld beads <NUM> are formed on the first layer to form a second layer of the built-up object W, a portion where a gravitational influence is maximum in the second layer is determined. Since weld beads <NUM> are to be formed on the base plate <NUM> inclined at the base-surface inclination angle θ along the track direction inclined with respect to the vertical direction at the track inclination angle ϕ to produce the built-up object W, a lower-end portion is the portion where a gravitational influence is maximum also in the second layer.

After the portion where a gravitational influence is maximum has been determined, a supporting bead 25A having a higher viscosity during bead formation than other weld beads to be deposited thereafter is formed as a weld bead <NUM> in the portion.

After determining a travelling speed V and a current value I for forming the supporting bead 25A, the control unit <NUM> operates the welding robot <NUM> to form the supporting bead 25A at the determined travelling speed V and current value I in the lower-end portion, where a gravitational influence is maximum, along a movement track which has been produced, as illustrated in (a) and (b) of <FIG>.

Thereafter, other weld beads <NUM> in the second layer are successively formed on the upper side of the already formed supporting bead 25A on the surface of the base plate <NUM>. Also in this case, a weld bead <NUM> is formed on the upper side of the already formed supporting bead 25A in a portion of the surface of the base plate <NUM> which adjoins the supporting bead 25A, as illustrated in (a) and (b) of <FIG>. As a result, this weld bead <NUM> is supported by the already formed supporting bead 25A. Consequently, this weld bead <NUM>, even when being a high-heat-input bead which has low viscosity during bead formation and can hence drip due to a gravitational influence, is formed while being supported by the supporting bead 25A. Thus, dripping is inhibited in forming this weld bead <NUM>. Furthermore, as illustrated in (a) and (b) of <FIG>, other weld beads <NUM> are successively formed on the upper side of the formed weld bead <NUM> so as to adjoin the formed weld bead <NUM>. In this operation, since the weld beads <NUM> being formed are supported by the underlying weld bead <NUM> which has been formed, dripping is inhibited in forming these weld beads <NUM>.

As explained above, in this embodiment of the method and apparatus for built-up object production and the built-up object, a supporting bead 25A is formed in a portion where a gravitational influence is maximum and other weld beads <NUM> are formed so as to overlie the supporting bead 25A. Specifically, in a case where the base surface on which weld beads <NUM> are to be formed, which is either the surface of a base plate <NUM> or the upper surface of underlying-layer weld beads <NUM>, is inclined, a supporting bead 25A is formed in a lower-end portion of each bead layer. Thus, other weld beads <NUM> can be formed using the formed supporting bead 25A as a support. Consequently, not only the other weld beads <NUM> can be inhibited from dripping by the gravitational influence but also it is possible to inhibit humping, which may occur if the travelling speed V of the torch <NUM> is increased in order to inhibit the dripping. Thus, a built-up object W of high quality can be produced while a takt time is reduced.

Furthermore, the low-heat-input beads formed with a reduced heat input for melting the filler metal M have a higher viscosity during bead formation and can be less affected by gravity than the other weld beads <NUM> to be deposited thereafter. Consequently, even in portions where the gravitational influence is maximum, supporting beads 25A constituted of such low-heat-input beads can be formed while dripping due to the gravitational influence is prevented.

Moreover, a portion where a gravitational influence is maximum can be determined from the base-surface inclination angle θ, which is the angle between the base surface being either the surface of the base plate <NUM> or the upper surface of underlying-layer weld beads and the vertical plane, and from the track inclination angle ϕ, which is the angle between the track direction of the torch <NUM> and a vertical direction on the base surface, and a supporting bead 25A can be accurately formed in the portion to produce a built-up object.

In particular, since indexes of gravitational influence are determined from cosθsinϕ, a built-up object W can be smoothly formed on the base surface having the base-surface inclination angle of θ and the track inclination angle of ϕ.

Next, a built-up object production example in this embodiment of the production method described above is explained.

<FIG> is a view illustrating an example of producing a built-up object.

As illustrated in <FIG>, a built-up object W is being formed on a base <NUM> placed on a pedestal <NUM>. The base <NUM> has a trapezoidal shape in the cross-section and the side surfaces thereof are inclined so as to face upward. Weld beads <NUM> are formed on a base surface <NUM> which is an inclined side surface of the base <NUM>. A plurality of bead layers 54a, 54b, 54c, 54d,. each composed of weld beads <NUM> have been formed on the base surface <NUM> so as to be stacked in a lateral direction S. Specifically, the plurality of bead layers 54a, 54b, 54c, 54d,. have been deposited on the base <NUM> in the horizontal direction from the base surface <NUM>.

In forming a built-up object W on the base surface <NUM> of the base <NUM>, a supporting bead 25A1 is first formed on the base surface <NUM> in a lower-end portion where a gravitational influence is maximum, along the base surface <NUM> in the direction of track inclination angle ϕ (ϕ≠<NUM>°). Other weld beads <NUM> are successively formed on the upper side of the supporting bead 25A1 along the base surface <NUM> so as to be fixed by the supporting bead 25A1. Thus, a first bead layer 54a is formed on the base surface <NUM>.

In a case of forming a second and succeeding bead layer 54b, a supporting bead 25A2 is formed on the first bead layer 54a on the base surface <NUM> in a lower-end portion where a gravitational influence is maximum, along the base surface <NUM> (so as to be bonded to the first bead layer 54a) in the direction of track inclination angle ϕ (ϕ≠<NUM>°). Other weld beads <NUM> are successively formed on the upper side of the supporting bead 25A2 along the base surface <NUM> (so as to be bonded to the first bead layer 54a) so as to be fixed by the supporting bead 25A2.

In this production example, supporting beads 25A1, 25A2,. are formed in lower-end portions of the bead layers 54a, 54b, 54c, 54d,. where a gravitational influence is maximum, and other weld beads <NUM> are formed along the base surface <NUM> so as to be fixed by the supporting beads 25A1, 25A2,. Thus, the weld beads <NUM> are supported by the supporting beads 25A1, 25A2,. even in a case where the weld beads <NUM> are deposited in an oblique direction (direction of track inclination angle ϕ) to which dripping is likely to occur. It is hence possible to prevent bead dripping and humping.

In particular, since the formation of the supporting beads 25A1, 25A2,. makes it possible to stably form the bead layers 54a, 54b, 54c, 54d,. , bead layers <NUM> each composed of weld beads <NUM> can be stacked in a lateral direction S on the side surface of the base <NUM> having an inclined base surface <NUM>. That is, the production method in this embodiment is suitable for deposition on a base <NUM> placed on a pedestal <NUM> and having an inclined side surface being base surface <NUM>, in which bead layers 54a, 54b, 54c, 54d,. composed of supporting beads 25A1, 25A2,. and of other weld beads <NUM> are formed on the base surface <NUM> being the side surface so as to be stacked in a lateral direction S.

Claim 1:
A method for producing a built-up object (W) by melting and solidifying a filler metal (M) to form weld beads (<NUM>) on a base surface (<NUM>) along a track for a torch (<NUM>) and form the built-up object (W) formed by the weld beads (<NUM>),
wherein the built-up object (W) includes a bead formation portion where a gravitational influence is maximum,
wherein the method comprises:
forming a supporting bead (25A) having a higher viscosity during weld-bead formation than other weld beads (<NUM>) in the bead formation portion; and
forming the other weld beads (<NUM>) overlying the supporting bead (25A);
the method being characterised by the following:
the bead formation portion is determined using a base-surface inclination angle (θ) and a track inclination angle (ϕ) as indexes of the gravitational influence, wherein the indexes of the gravitational influence are determined from cosθsinϕ,
wherein the base-surface inclination angle (θ) is an angle between the base surface (<NUM>) on which the weld beads (<NUM>) are to be formed and a vertical direction,
wherein the track inclination angle (ϕ) is an angle between a track direction of the torch (<NUM>) in forming the weld beads (<NUM>) and a vertical direction on the base surface (<NUM>);
wherein the built-up object (W) includes deposited bead layers (54a, 54b, 54c, 54d) each including a plurality of the weld beads (<NUM>) formed on/above the base surface (<NUM>),
wherein in a case where the base surface (<NUM>) is inclined with respect to the vertical direction, the supporting bead (25A) is formed in a lower-end portion of the bead layers (54a, 54b, 54c, 54d).