Patent Application
20240131608
The present disclosure relates to a deposition planning method, a deposition plan making apparatus, and a program for an additively manufactured object formed by depositing weld beads.
Recently, needs for forming using a 3D printer as a production means have increased, and research and development for the practical use of forming using a metallic material has progressed. The 3D printer that forms a metallic material prepares an additively manufactured object by melting a metal powder and a metal wire using a laser, an electron beam, or a heat source such as an arc and depositing the molten metal. For example, Patent Literature 1 discloses a deposition design method in which, when an additively manufactured object is manufactured by depositing weld beads obtained by melting and solidifying a wire-like metallic material (filler metal), a manufacturing process of the additively manufactured object is evaluated by a simulation, welding paths and welding conditions are adjusted to be optimal, and a welding apparatus is controlled for forming under the adjusted conditions.
Patent Literature 1: JP2010-201474A
Patent Literature 2: JP2019-111582A
Incidentally, when an additively manufactured object is formed by depositing a plurality of weld beads by arc welding, an intersection portion where the weld beads are overlap each other depending on the shape of the additively manufactured object is formed. When the intersection portion is formed, for example, a method of subsequently forming a weld bead B2 with respect to a weld bead B1 in a direction orthogonal to the weld bead B1 as illustrated in
In addition, in a technique of Patent Literature 2, in a manufacturing process including a contour forming step of forming a contour of an additively manufactured object and a filling pattern welding step of filling the inside of the contour, at an intersection point where the filling pattern encounters the contour, welding conditions change to prevent an amount of a metallic material where the contour is distorted from being welded to the intersection point. Even in this case, the setting of the welding conditions is complicated, and enormous effort is required to form the intersection portion without any problems.
Accordingly, an object of the present disclosure is to provide a deposition planning method, a deposition plan making apparatus, and a program for an additively manufactured object, in which the occurrence of an internal defect in an intersection portion where weld beads intersect with each other can be prevented, and the beads can be formed at a uniform deposition height.
The present disclosure has the following configurations.
According to the present disclosure, the occurrence of an internal defect in an intersection portion where weld beads intersect with each other can be prevented, and the beads can be formed at a uniform deposition height.
Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings.
A manufacturing apparatus 100 of an additively manufactured object having this configuration includes an additive manufacturing apparatus 11, a controller 13 that comprehensively controls the additive manufacturing apparatus 11, and a power supply device 15. The additive manufacturing apparatus 11 includes a welding robot 19 where a torch 17 is provided at a tip axis, and a filler metal supply unit 21 configured to supply a filler metal (welding wire) M to the torch 17. The additive manufacturing apparatus 11 melts and solidifies the filler metal M by arc welding to form weld beads B on a base plate 23, and sequentially deposits the weld beads B to form an additively manufactured object 25. The manufacturing apparatus 100 of an additively manufactured object described herein has one configuration example and may have another configuration.
The welding robot 19 is an articulated robot, and is supported in the torch 17 attached to a tip axis of a robot arm so that the filler metal M can be continuously supplied. Any position and any posture of the torch 17 can be three-dimensionally set in a range of degree of freedom of the robot arm.
The torch 17 includes a shield nozzle (not illustrated) and is supplied with shielding gas from the shield nozzle. An arc welding method used herein may be any of a consumable electrode type such as shielded metal arc welding and CO2 arc welding or a non-consumable electrode type such as TIG welding and plasma arc welding, and is appropriately selected depending on the additively manufactured object to be prepared.
For example, in the consumable electrode type, a contact tip is disposed in the shield nozzle, and the tiller metal M to which a melting current is supplied is held in the contact tip. The torch 17 generates an arc from a tip of the tiller 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 21 to the torch 17 by a feeding function (not illustrated) attached to the robot arm or the like. When the filler metal M that is continuously fed is melted and solidified while moving the torch 17, the linear weld beads B that is a melt-solidified product of the filler metal M are formed on the base plate 23.
As the filler metal M, various commercially available welding wires can be used. For example, wires defined by solid wires (JIS Z 3312) for MAG and MIG welding of mild steel, high strength steel, and low temperature service steel or flux cored wires (JIS Z 3313) for arc welding. of mild steel, high strength steel, and low temperature service steel can be used.
In addition, a heat source that melts the filler metal M is not limited to the above-described arc, For example, a heat source using another method such as a heating method using an arc and a laser in combination, a heating method using a plasma, or a heating method using an electron beam or a laser may be adopted. When the filler metal M is heated by the electron beam or the laser, the amount of heat can be controlled more finely, and the state of the weld beads can be more accurately maintained, which can contribute to further improvement of the quality of the additively manufactured object.
The controller 13 includes a deposition planning unit 27, a storage unit 29, and a control unit 31 to which these units are connected. The controller 13 is configured by a computer device including a CPU, a memory, and a storage.
The deposition planning unit 27 generates a shape model as a target shape based on three-dimensional shape data (for example, CAD data) of the additively manufactured object to be prepared, and slices the obtained shape model into a plurality of weld bead layers corresponding to the heights of the weld beads B. Regarding each of the sliced layers of the shape model, a deposition plan for determining bead formation paths (trajectories of the torch 17 for forming the weld beads B) and welding conditions for forming the weld beads B (including heating conditions or welding conditions such as a welding current or a welding voltage for obtaining a bead width, a bead deposition height, and the like) is made.
That is, the shape model as the target shape is sliced into a plurality of bead models having shapes corresponding to the weld beads, and the bead formation path and the welding conditions in each of the sliced layers are determined. The made deposition plan is stored in the storage unit 29 as a driving program that drives each of the units of the additive manufacturing apparatus 11.
In the manufacturing apparatus 100 of an additively manufactured object having the above-described configuration, the control unit 31 executes the driving program stored in the storage unit 29 to drive the welding robot 19 and the power supply device 15. That is, the controller 13 drives the welding robot 19 according to a procedure set by the driving program, moves the torch 17 along the bead formation path, heats the filler metal M by an arc at the torch tip, and deposits the molten filler metal M on the base plate 23. As a result, the additively manufactured object 25 where the plurality of weld beads B are formed on the base plate 23 is obtained.
The deposition plan and the driving program may be generated by another computer device different from the controller 13 by inputting required information to the other computer device. In this case, the deposition planning unit 27 is configured by a computer device including a CPU, a memory, and a storage, and the information and the driving program about the made deposition plan are input to the storage unit 29 of the controller 13 through an appropriate communication means such as a LAN.
For example, the additively manufactured object 25 is formed by depositing plural rows (three rows) of weld beads B1 adjacent to each other that are firmed along one direction (X direction) and plural rows (three rows) of weld beads B2 adjacent to each other that are formed along a direction (Y direction) orthogonal to the one direction to form a plurality of layers (three layers) in a height direction (Z direction). A portion (portion surrounded by dotted lines on a bead uppermost layer) where the weld beads B1 and B2 intersect with each other will be referred to as an intersection portion CR, and portions other than the intersection portion CR will be referred to as constant portions RE. An actual additively manufactured object is likely to have a more complicated shape than the above-described shape. Here, the description will be made using the intersection portion CR having a simple shape.
When the deposition plan of the additively manufactured object 25 including the above-described intersection portion CR is made, after forming the weld beads B1 and B2, the deposition height of the intersection portion CR and the deposition height of the constant portion RE match with each other, and the welding conditions of the weld beads are set to suppress the occurrence of an internal defect.
The deposition planning unit 27 includes a data acquisition unit 33, a welding path determination unit 35, a welding path classification unit 37, an upper and lower layer division unit 39, and a welding condition determination unit 41.
The data acquisition unit 33 acquires shape data of the additively manufactured object 25 as a forming target, the welding path determination unit 35 determines a movement trajectory of the torch 17 illustrated in
Hereinafter, a basic deposition plan made by a deposition planning method will be described.
Here, the deposition plan of the additively manufactured object 25 including the intersection portion CR illustrated in
Each of the welding paths L1 to L6 can be classified into an intersection portion CR where the weld beads intersect with each other and constant portions RE other than the intersection portion CR, welding paths in the regions of the constant portions RE will be referred to as constant region paths LR1 and LR2, and a welding path in the region of the intersection portion CR will be referred to as intersection region paths LC.
In the welding paths L1, L2, and L3 illustrated in
In addition, in the welding paths L4, L5, and L6 illustrated in
When the welding rate increases, the deposit amount per unit length of the formed weld beads decreases, and thus the height of the weld beads decreases. Using this configuration, the welding rate is adjusted such that the sum of the deposit amounts in the intersection region paths LC of the welding paths L1, L2, and L3 and in the intersection region paths LC of the welding paths L4, L5, and L6 is equal to the deposit amounts in the constant region paths LR1 and LR2. As a result, the total height of the weld beads formed along the intersection region paths LC of the welding paths L1, L2, and L3 and the intersection region paths LC of the welding paths L4, LS, and L6 that vertically overlap each other is equal to the heights of the weld beads formed in the constant portions RE.
As illustrated in
However, as illustrated in
As illustrated in
As illustrated
As illustrated in
Next, the welding conditions will be described in more detail. A deposit amount S of the weld bead is represented by Expression (1).
S: deposit amount (deposit volume per unit length [1 mm])
The welding conditions of the constant portion can be set, for example, as follows.
In the intersection portion CR, it is preferable that the deposit amount of the weld bead formed along the lower layer path is as small as possible. Accordingly, when the welding rate Vweld is set to 300 [cm/min] which is a maximum movement speed of the robot that supports the torch, a deposit amount (lower layer deposit amount) S1 of the weld bead formed along the lower layer path is 1.9 mm3. In addition, in order to adjust the deposit amount of the intersection portion CR to be equal to the deposit amount of the constant portion RE, a deposit amount (upper layer deposit amount) S2 of the weld bead formed along the upper layer path is 7.8-1.9=5.9 mm3 when calculated from Expression (2).
S2=S−S1 (2)
In this case, when the welding conditions of the upper layer path are converted and acquired, assuming that the feeding rate of the filler metal is 5.2 [m/min], the welding rate is 97 [cm/min].
In order to make the surface texture of the weld bead uniform, the bead width of the weld bead formed along the upper layer path needs to be controlled not to change as far as possible. Therefore, it is preferable that a ratio S1/(S1+S2) of the deposit amounts is as low as possible. In order to set a threshold (upper limit value) for the ratio S1 (S1+S2), for example, a value where a defect starts to occur between the weld beads adjacent to each other may be set as the threshold.
Here, it is considered that, in the intersection portion CR of the weld beads, three rows of weld beads that intersect with each other are formed. As illustrated in
In addition, since the distance between weld beads adjacent to each other does not change, the undulation between the beads increases, and the angle θ between the valleys decreases. When the angle θ between the valleys decreases, a thin, deep, and narrow portion is formed, and when the weld bead is continuously deposited on the narrow portion, the narrow portion remains as an internal defect without being melted.
On the other hand, as illustrated in
As described above, by selling limited tuning parameters such as the welding rate based on the condition of the deposit amount, forming where the occurrence of an internal defect is prevented can be performed, and deposition conditions for the intersection portion where there are no problems can be easily set.
When the intersection portion CR of the weld beads is formed along one welding path La and another welding path Lb intersecting with the welding path La, an intersection point Pc between the welding path La and the welding path Lb is acquired from coordinate information of the welding paths. In addition, a bead width W of the weld bead formed along the welding path La is acquired from the above-described information such as the deposit amount.
Here, the intersection portion CR is in a range of a bead width W/2 centering on the intersection point Pc in front of and behind a welding direction along the welding paths La and Lb. In the intersection portion CR, the welding rate in the intersection region paths LC is changed from a welding rate V1 to a welding rate V2 in the constant region path. That is, a timing at which the welding rate starts to change is a timing of reaching the intersection portion CR from the constant portion RE in the welding path Lb, that is, a position PBF moved back from the intersection point Pc by a distance of W/2. In addition, a timing at which the welding rate returns to the welding rate V1 of the constant region path is a position PAF moved forward from the intersection point Pc by a distance of W/2. As in the welding path La, the welding rate is set to the welding rate V in a range from the position moved back from the intersection point Pc along the welding path La by a distance of W/2 to the position moved forward from the intersection point Pc along the welding path La by a distance of W/2.
This way, by setting the position where the welding rate changes to the position at the distance that is ½ of the bead width W from the intersection point Pc, local excess and deficiency in deposit amount in the vicinity of the rate change point can he resolved. Accordingly, the weld bead can be formed in a smooth shape without local unevenness of the additively manufactured object.
Next, a procedure of making the deposition plan where the bead formation paths and the welding conditions for forming the additively manufactured object are set will be described in detail.
First, the data acquisition unit 33 reads three-dimensional shape data representing a target shape of the additively manufactured object to be prepared (St. 1).
The welding path determination unit 35 generates a three-dimensional shape model based on the acquired shape data, and slices the obtained shape model into layers obtained by forming the weld beads once. That is, the shape model is sliced into a plurality of layers corresponding to the heights of the weld beads B. Regarding each of the obtained plurality of layers, welding paths that are trajectories of the torch 17 (
Next, the welding path classification unit 37 classifies the plurality of welding paths in the same layer of each of the sliced layers into the intersection region paths and the constant region paths corresponding to constant portions other than the intersection portion (St. 3).
Regarding each of the welding paths classified into the constant region paths, the welding condition determination unit 41 sets welding conditions for forming the weld beads (conditions including heating conditions such as a welding current or a welding voltage for obtaining a desired bead width and a desired bead deposition height, a filler metal feeding rate, and the like) (St. 4).
On the other hand, the welding paths classified into the intersection region paths are divided by the upper and lower layer division unit 39 into a lower layer path along which a lower layer of the intersection portion is formed and an upper layer path along which an upper layer of the intersection portion is formed, and the welding conditions are set by the welding condition determination unit 41. Specifically, first, for a ratio between a lower layer deposit amount S1 per unit length of the weld beads formed along the lower layer path and an upper layer deposit amount S2 per unit length of the weld beads formed along the upper layer path, specifically, for a ratio S1/(S1+S2) of the deposit amounts, a threshold R that is a limit value where a defect does not occur is determined by determining whether or not a defect occurs by a simulation or an experimental measurement (St. 5).
When the threshold R is determined, as a specific index, in a cross-section orthogonal to a longitudinal direction of the weld beads, the angle θ of the valley portion formed between the weld beads adjacent to each other due to the undulation of the plurality of weld beads formed along the upper layer path may be used. This formed shape may be experimentally obtained by actual forming. However, the angle θ of the valley portion can also be analytically predicted with a sufficient accuracy by setting the cross-sectional shape of the weld beads to a simple shape such as a trapezoidal model.
In addition, as described above, assuming that the limit value of the angle θ of the valley portion is, for example, 40°, a limit ratio S1/(S1+S2) of limit deposit amounts where the angle θ is 40° or more may be obtained as the threshold R. The threshold R may be determined using, for example, table information regarding the occurrence of a defect that is obtained in advance before additive manufacturing.
The lower layer deposit amount S1 and the upper layer deposit amount S2 may be temporarily set such that the sum of the lower layer deposit amount S1 and the upper layer deposit amount S2 is equal to a deposit amount per unit length of the weld beads formed along the constant region path and the ratio S1/(S1+S2) of the deposit amounts is the predetermined threshold R or less (St. 6). It can be seen that, under welding conditions where the ratio S1/(S1+S2) of the deposit amounts is the threshold R or less, as illustrated in
Next, based on the temporarily set ratio of the deposit amounts, the welding rate V2 (refer to Va2 and Vb2 illustrated in
When the welding rate V2 exceeds the maximum rate Vmax, the lower layer deposit amount S1 is increased (St. 9), and the process restarts from Step St. 7. When the welding rate V2 is the maximum rate Vmax or lower, whether or not the ratio S1/(S1+S2) of the deposit amounts is the threshold R or less is determined (St. 10). When the ratio S1/(S1+S2) of the deposit amounts exceeds the threshold R, the feeding rate Vwire of the filler metal is decreased (St. 11), and the process restarts from Step St. 7. When the ratio S1/(S1+S2) of the deposit amounts is the threshold R less, the lower layer deposit amount S1 and the upper layer deposit amount S2 that are temporarily set are fixed, and welding conditions corresponding to S1 and S2 are determined (St. 12).
Here, regarding samples formed with various ratios S1/(S1+S2), whether forming is good or bad was determined.
The weld beads of the upper layer of each of the samples 1 to 3 illustrated in
It can be determined from the above results that, when the ratio S1/)S1+S2) in the samples 1 to 3 is 0.4 or less, a welding defect does not occur, and it can be determined from the above results that, when the ratio S1/(S1+S2) in the samples 4 and 5 exceeds 0.4, a gap is generated between the weld beads of the upper layer such that an internal defect may occur. This way, when various conditions such as a material or a shape of the manufactured object are determined, a limit value of the ratio where an internal defect may occur is acquired.
Weld beads are formed along one welding path La and another welding path Lb intersecting with the welding path La. At this time, a position moved back from the intersection point Pc between the welding path La and the welding path Lb along the welding path La by a distance that is ½ of the bead width W of the weld bead formed along the welding path La is represented by PBF. The welding rate changes with this position PBF as a center position in a range from a change start point to a change end point of the welding rate.
That is, the welding rate is gradually increased from V1 of the constant region path to V2 of the intersection region path such that the areas of diagonally hatched triangles A1 and A2 haying a width d centering on the position PBF in
In the above-described additive manufacturing procedure, the intersection portion is formed by causing the weld beads of the lower layer and the weld beads of the upper layer to overlap each other. However, the intersection portion may be formed using only the weld beads of the upper layer by stopping the formation of the weld beads of the lower layer while keeping the welding path continuous.
For example, in a period of the intersection region paths LC of the welding paths L1, L2, and L3 illustrated in
At this time, it is preferable that, at the time of restart after temporarily stopping the formation of the weld beads along the lower layer path, the feeding rate of the filler metal is controlled in synchronization with the change in the welding rate.
As illustrated in
The deposit amount may be maintained to be as small as possible while causing the torch to generate a minimum arc without completely stopping the formation of the weld beads along the lower layer path. Even in this case, a state close to a case where the formation of the weld beads of the lower layer is substantially completely stopped is obtained.
The present disclosure is not limited to the above-described embodiment, and combinations of the configurations of the embodiment and changes and applications based on the description of the specification and well-known techniques by those skilled in the art can be expected from the present disclosure and are included in the range for which protection is sought.
As described above, the present specification discloses the following features.
(1) A deposition planning method for an additively manufactured object, in which the additively manufactured object is formed using shape data representing a three-dimensional shape of the additively manufactured object by an additive manufacturing apparatus that deposits weld beads obtained by melting and solidifying a filler metal, the deposition planning method including:
In the deposition planning method of an additively manufactured object, the intersection region paths are divided into the upper layer path and the lower layer path, and the welding conditions are set for each of the paths. The deposition plan can be easily made, in which the occurrence of an internal defect in the intersection portion where the weld beads intersect with each other can be prevented, and the beads can he formed at a uniform deposition height.
(2) The deposition planning method of an additively manufactured object according to (1), in which in the step of determining the welding conditions of the intersection region paths, the deposit amount changes by changing a welding rate of the upper layer path in the intersection region paths to be slower than a welding rate of the lower layer path.
In the deposition planning method of an additively manufactured object, the deposit amount can be appropriately adjusted by changing the welding rate that can be easily adjusted.
(3) The deposition planning method of an additively manufactured object according to (2), in which in the process of forming the weld beads from the constant portion to the intersection portion, the change of the welding rate starts from a position moved back from a center position of the intersection portion by a length that is half of a bead width of the constant portion orthogonal to a bead longitudinal direction.
In the deposition planning method of an additively manufactured object, local excess and deficiency in deposit amount in the portion where the deposit amount changes can be resolved, and a smooth bead shape can be formed. Accordingly, the occurrence of local unevenness of the additively manufactured object can be prevented.
(4) The deposition planning method of an additively manufactured object according to (2), in which in the process of forming the weld beads from the constant portion to the intersection portion, the welding rate changes such that a position moved back from a center position of the intersection portion by a length that is half of a head width of the constant portion orthogonal to a bead longitudinal direction is a center position in a range from a change start point to a change end point of the welding rate.
In the deposition planning method of an additively manufactured object, by continuously changing the welding rate, local excess and deficiency in deposit amount can be resolved more reliably, and a smooth bead shape can be formed.
(5) The deposition planning method of an additively manufactured object according to any one of (2) to (4), in which not only the welding rate but also a feeding rate of the filler metal changes.
In the deposition planning method of an additively manufactured object, by changing not only the welding rate but also the feeding rate of the filler metal, the adjustment width can be expanded.
(6) The deposition planning method of an additively manufactured object according to (1), in which in the step of determining the welding conditions of the intersection region paths, in the intersection region paths, the formation of the weld beads along the lower layer path is stopped and the weld beads are formed only along the upper layer path.
In the deposition planning method of an additively manufactured object, by forming the intersection portion using only the upper layer path while keeping the welding trajectories of the lower layer paths in the constant portion and the intersection portion continuous, a gap is not likely to be generated at a boundary between the constant portion and the intersection portion, and the occurrence of an internal defect can be suppressed.
(7) The deposition planning method of an additively manufactured object according to (6), in which at time of restart from the stop of the formation of the weld beads, a feeding rate of the filler metal is set to be lower than a feeding rate before the stop of the formation of the weld beads to gradually increase from the low rate to the feeding rate before the stop of the formation.
In the deposition planning method of an additively manufactured object, even at the time of restart from the temporary stop of the bead formation, weld beads can be formed smoothly and continuously.
(8) The deposition planning method of an additively manufactured object according to (7), in which until the feeding rate of the filler metal reaches the feeding rate before the stop of the formation of the weld beads from the restart, a welding rate gradually decreases from a welding rate of the intersection region paths to a welding rate of the constant region paths.
In the deposition planning method of an additively manufactured object, the feeding rate of the filler metal and the welding rate are adjusted in combination. Therefore, the deposit amount can be controlled more accurately, and the weld beads can be formed more smoothly.
(9) The deposition planning method of an additively manufactured object according to any one of (1) to (8), in which in the step of determining the welding conditions of the intersection region paths, when the lower layer deposit amount is represented by S1 and the upper layer deposit amount is represented by S2, a ratio S1/(S1+S2) of the lower layer deposit amount S1 to a total deposit amount (S1+S2) is set depending on a gap between a plurality of the weld beads in the intersection portion.
In the deposition planning method of an additively manufactured object, by managing the lower layer deposit amount and the upper layer deposit amount at the predetermined ratio, the deposit amount in the intersection portion can be determined more accurately.
(10) A deposition plan making apparatus that makes a deposition plan in which an additively manufactured object is formed using shape data representing a three-dimensional shape of the additively manufactured object by an additive manufacturing apparatus that deposits weld beads obtained by melting and solidifying a filler metal, the deposition plan making apparatus including:
In the deposition planning apparatus of an additively manufactured object, the intersection region paths are divided into the upper layer path and the lower layer path, and the welding conditions are set for each of the paths The deposition plan can be easily made, in which the occurrence of an internal defect in the intersection portion where the weld beads intersect with each other can be prevented, and the beads can be formed at a uniform deposition height.
(11) A program causing a computer to execute an additive manufacturing procedure for an additively manufactured object, in which the additively manufactured object is formed using shape data representing a three-dimensional shape of the additively manufactured object by an additive manufacturing apparatus that deposits weld beads obtained by melting and solidifying a filler metal, the additive manufacturing procedure including:
With this program, the deposition plan can be easily made, in which the occurrence of an internal defect in the intersection portion where the weld beads intersect with each other can he prevented, and the beads can be formed at a uniform deposition height,
The present application is based on Japanese patent application No. 2021-25576 filed on Feb. 19, 2021, the content of which is incorporated herein by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-025576 | Feb 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/003449 | 1/28/2022 | WO |
