JP2023020403A - Heat transfer calculation method for molded object, heat transfer calculation device for molded object, molded object manufacturing method, molded object manufacturing device and program - Google Patents

Abstract

To execute a heat transfer calculation at a high speed by maintaining required calculation accuracy while suppressing an increase in a calculation load.SOLUTION: A heat transfer calculation method for a molded object includes the steps of: acquiring an analysis shape model obtained by dividing the shape of a molded object into a plurality of elements; acquiring a molding condition including information of a heat input from a heat source, a bead formation trajectory and a bead physical property from a molding plan; selecting an element included in a temperature calculation area centering on the position of the heat source in which a weld bead is formed among a plurality of elements of the analysis shape model as a calculation object element of a heat transfer calculation; calculating a temperature distribution of the temperature calculation area due to heat balance at which heat from the heat source is transferred to the calculation object element on the basis of the molding condition; and moving the position of the heat source in the analysis shape model along the bead formation trajectory, repeating the selection of the calculation object element included in the temperature calculation area centering on a movement destination position of the heat source and the calculation of the temperature distribution of the temperature calculation area, and acquiring a temperature history in the middle of molding the molded object.SELECTED DRAWING: Figure 5

Description

The present invention relates to a modeled article heat transfer calculation method, a modeled article heat transfer calculation apparatus, a modeled article manufacturing method, a modeled article manufacturing apparatus, and a program.

2. Description of the Related Art There is known a layered manufacturing method for manufacturing a modeled object having a desired shape by stacking weld beads formed by a welding technique such as arc welding (for example, Patent Document 1).
Patent Literature 1 describes setting appropriate forming conditions by thermal fluid analysis of temperature and shape changes during the welding process. This thermofluid analysis seeks the change in temperature over time when a weld bead is formed on a substrate while a heat source (arc) is moved. In addition, in this analysis, instead of the coordinate system in Lagrange notation, in which the heat source is moved on a fixed substrate to form a welding bead, the Eulerian notation, in which the heat source is fixed and the substrates are moved relatively to form the welding bead, is used. coordinate system is used. Then, the spatial change in temperature in the stationary solution of the Euler coordinate system is converted into the temporal change in temperature when the heat source is moved on the fixed substrate to form a molten bead.

In addition, in the thermal fluid analysis in Patent Document 1, both A region of intermediate element size is provided between .

JP 2020-44541 A

In the heat transfer calculation for calculating the heat balance using a computer as described above, the geometric model used for the calculation is divided into a plurality of elements and matrix calculation is performed. However, as the shape of the object to be layered and manufactured becomes more complicated and larger, the number of elements into which the shape model is divided increases. Further, in order to improve the calculation accuracy, it is required to divide the elements more finely. Such an increase in the number of elements causes problems such as an increase in calculation load, a longer calculation time, and a need for a computer with high arithmetic performance.

Accordingly, the present invention provides a heat transfer calculation method for a shaped object, a heat transfer calculation apparatus for a shaped object, a shaped object heat transfer calculation apparatus, and a shaped object heat transfer calculation method that can perform heat transfer calculation at high speed while suppressing an increase in computational load while maintaining necessary calculation accuracy. An object of the present invention is to provide a manufacturing method, a model manufacturing apparatus, and a program.

The present invention consists of the following configurations.
(1) Heat transfer calculation of a modeled object for calculating the heat transfer from the heat source forming the weld bead to the modeled object when the modeled object is modeled by laminating welding beads based on a preset modeling plan. a method,
obtaining an analytical shape model in which the shape of the object is divided into a plurality of elements;
a step of obtaining molding conditions including information on heat input from a heat source for forming the welding bead, bead formation trajectory of the welding bead, and bead physical properties from the molding plan;
a step of selecting, from among the plurality of elements of the analytical shape model, elements included in a temperature calculation region centered on the position of the heat source where the welding bead is formed, as calculation target elements for heat transfer calculation;
obtaining a temperature distribution in the temperature calculation area based on a heat balance in which heat from the heat source is transferred to the calculation target element based on the modeling conditions;
Move the position of the heat source in the analytical shape model along the bead formation trajectory, select the calculation target element included in the temperature calculation area centered on the movement destination position of the heat source, and select the temperature calculation area a step of repeating the calculation of the temperature distribution to obtain a temperature history during the modeling of the modeled object;
having
Heat transfer calculation method for molded objects.
(2) A method for manufacturing a shaped article, wherein the shaped article is manufactured based on the shaping plan determined by using the heat transfer calculation method for the shaped article according to (1).
(3) Calculation of heat transfer of a modeled object to calculate the heat transfer from the heat source forming the weld bead to the modeled object when the modeled object is modeled by laminating the welding beads based on a preset modeling plan. a device,
a model generation unit that obtains an analysis shape model in which the shape of the object is divided into a plurality of elements;
a molding condition acquisition unit that acquires molding conditions including heat input from a heat source for forming the welding bead, bead formation trajectory of the welding bead, and bead physical properties from the molding plan;
a target element selection unit that selects, from among the plurality of elements of the analytical shape model, elements included in a temperature calculation region centering on the position of the heat source where the welding bead is formed, as calculation target elements for heat transfer calculation; ,
a temperature distribution calculation unit that obtains a temperature distribution in the temperature calculation area based on a heat balance in which heat from the heat source is transferred to the calculation target element based on the modeling conditions;
Move the position of the heat source in the analytical shape model along the bead formation trajectory, select the calculation target element included in the temperature calculation area centered on the movement destination position of the heat source, and select the temperature calculation area a temperature history calculation unit that repeats the calculation of the temperature distribution to obtain a temperature history during the molding of the modeled object;
comprising
Heat transfer calculation device for molded objects.
(4) A model manufacturing apparatus for manufacturing the model based on the model plan determined using the model heat transfer calculation device according to (3).
(5) Calculating the heat transfer of a modeled object for calculating the heat transfer from the heat source forming the weld bead to the modeled object when the modeled object is modeled by laminating welding beads based on a preset modeling plan. A program that causes a computer to perform the steps of the method,
to the computer,
A function to obtain an analysis shape model in which the shape of the object is divided into a plurality of elements;
A function of acquiring molding conditions including heat input from a heat source for forming the welding bead, bead formation trajectory of the welding bead, and bead physical properties from the molding plan;
A function of selecting, from among the plurality of elements of the analytical shape model, elements included in a temperature calculation region centered on the position of the heat source where the welding bead is formed, as calculation target elements for heat transfer calculation;
a function of determining the temperature distribution in the temperature calculation area based on the heat balance in which the heat from the heat source is transferred to the calculation target element based on the modeling conditions;
Move the position of the heat source in the analytical shape model along the bead formation trajectory, select the calculation target element included in the temperature calculation area centered on the movement destination position of the heat source, and select the temperature calculation area a function of repeating the calculation of the temperature distribution to obtain a temperature history during the molding of the modeled object;
program to make it happen.

According to the present invention, the heat transfer calculation can be performed at high speed while suppressing an increase in computational load and maintaining necessary calculation accuracy.

FIG. 1 is an overall configuration diagram of a layered manufacturing apparatus that manufactures a modeled object. FIG. 2 is a functional block diagram of a control section having a function of analyzing the temperature of a welding bead during molding. FIG. 3 is an explanatory view schematically showing how a welding bead is formed. FIG. 4 is a partial cross-sectional view of a molded article schematically showing how a base plate and a molded article formed by laminating welding beads are divided into a large number of elements. FIG. 5 is an explanatory diagram showing the relationship between the welding bead and the calculation area of the analytical shape model. FIG. 6 is an explanatory view showing calculation target elements set in the temperature calculation region among a plurality of elements of the analytical shape model, and (A) is a schematic partial front view of the analytical shape model viewed from the welding direction. It is a figure and (B) is a typical partial side view seen from the direction orthogonal to a welding direction. FIG. 7 is a schematic diagram showing temperature distribution due to heat transfer of each element for setting the temperature calculation region. 8A to 8C are explanatory diagrams schematically showing the shape of the temperature calculation area. FIG. 9 is a flow chart showing the procedure of heat transfer calculation step by step. FIG. 10 is a schematic explanatory view of part of the elements of the analytical shape model near the heat input position, viewed from a direction perpendicular to the welding direction. 11A and 11B are explanatory diagrams showing how the heat source position is moved. FIG. 12 is a schematic diagram of part of the elements of the analytical shape model near the heat input position viewed from a direction orthogonal to the welding direction, and shows the boundary between the calculation target element and the element outside the temperature calculation region. is applied to heat transfer conditions that cause heat transfer. 13 is an explanatory diagram schematically showing the heat balance for the temperature calculation region of the analytical shape model shown in FIG. 12. FIG. FIG. 14 is a graph schematically showing the results of obtaining the cooling time required for reaching the reference temperature by heat transfer calculations performed under various conditions for each bead forming pass for forming a modeled object. FIG. 15 is an explanatory diagram showing the result of heat transfer calculation, in which the temperature distribution during the calculation of the analytical shape model is shown in shading. FIG. 16 is a perspective view showing the result of heat transfer calculation, in which the temperature distribution of each calculation target element within the temperature calculation region is indicated by shading.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the present embodiment, the amount of heat received by the modeled object when the modeled object is modeled by laminating welding beads based on a preset modeling plan is calculated. This amount of heat is due to heat transfer from the heat source forming the welding bead to the model, which will be described in detail below.

First, a layered modeling apparatus that laminates welding beads to form a modeled object will be described.
(Configuration of additive manufacturing apparatus)
FIG. 1 is an overall configuration diagram of a layered manufacturing apparatus that manufactures a modeled object.
The layered manufacturing apparatus 100 includes a modeling unit 11 and a control unit 13 that controls the modeling unit 11 .
The modeling unit 11 includes a welding robot 17 having a welding torch 15 on its tip axis, a robot driving unit 21 that drives the welding robot 17, and a filler material supply unit that supplies a filler material (welding wire) M to the welding torch 15. 23 and a welding power source 25 that supplies welding current and welding voltage.

(modeling department)
Welding robot 17 is an articulated robot, and filler material M is supported at the tip of welding torch 15 attached to the tip shaft of the robot arm. The position and posture of the welding torch 15 can be arbitrarily three-dimensionally set within the range of degrees of freedom of the robot arm according to commands from the robot driving section 21 . Although not shown, a weaving mechanism for weaving the welding torch 15 may be provided on the tip shaft of the robot arm.

The welding torch 15 is a gas metal arc welding torch that has a shield nozzle (not shown) and is supplied with a shield gas from the shield nozzle. The arc welding method may be a consumable electrode type such as coated arc welding or carbon dioxide gas arc welding, or a non-consumable electrode type such as TIG welding or plasma arc welding. be.

For example, in the case of the consumable electrode type, a contact tip is arranged inside the shield nozzle, and the contact tip holds the filler material M to which the welding current is supplied. The welding torch 15 holds the filler material M and generates an arc from the tip of the filler material M in a shield gas atmosphere.

The filler material supply unit 23 includes a reel 27 around which the filler material M is wound. The filler material M is sent from the filler material supply unit 23 to a feeding mechanism (not shown) attached to a robot arm or the like, and fed to the welding torch 15 while being forwarded and reversed by the feeding mechanism as necessary. be.

As filler material M, any commercially available welding wire can be used. For example, MAG welding and MIG welding solid wires for mild steel, high-strength steel and low-temperature steel (JIS Z 3312), arc welding flux-cored wires for mild steel, high-strength steel and low-temperature steel (JIS Z 3313), etc. welding wire is available. Additionally, filler metals M such as aluminum, aluminum alloys, nickel, nickel-based alloys, etc. can be used depending on the desired properties.

The robot drive unit 21 drives the welding robot 17 to move the welding torch 15 . As the welding torch 15 moves, the continuously supplied filler material M is melted by the welding current and welding voltage from the welding power source 25 .

That is, the welding robot 17 holds the welding torch 15 for melting and solidifying the wire-like filler material M while generating an arc at the tip of the arm, and continuously feeds the welding torch 15 while moving the welding torch 15 . The filler material M is melted and solidified by an arc, and a weld bead B, which is a melted and solidified body of the filler material M, is formed on the base plate 29 which is a base material.

(control part)
Although not shown, the control unit 13 is a computer device including an input/output unit, a storage unit, and a calculation unit.
The input/output unit is connected to the welding robot 17, the welding power supply unit 25, the filler material supply unit 23, and the like. The storage unit stores various information including a driving program, which will be described later. The storage unit consists of memories such as ROM and RAM, drive devices such as hard disks and SSDs (Solid State Drives), and storage exemplified by storage media such as CDs, DVDs, and various memory cards, and is capable of inputting and outputting various types of information. It has become. A modeling program corresponding to a modeled object to be manufactured is input to the control unit 13 via a communication line such as a network or various storage media. This modeling program is created based on a modeling plan that defines a bead forming trajectory for forming the welding bead B and welding conditions, and is composed of a large number of instruction codes.

The control unit 13 executes the modeling program stored in the storage unit, drives the welding robot 17, the filler material supply unit 23, the welding power supply unit 25, etc., and forms the welding bead B according to the modeling program. That is, the control unit 13 drives the welding robot 17 by the robot driving unit 21 to move the welding torch 15 along the trajectory (welding trajectory) of the welding torch 15 set in the modeling program, and to move the set welding trajectory. The filler material supply unit 23 and the welding power supply unit 25 are driven according to the conditions, and the filler material M at the tip of the welding torch 15 is melted and solidified by the arc. In this way, by sequentially laminating the welding beads B based on the modeling program, the desired three-dimensional modeled object W is modeled.

A modeling program is created by the control unit 13 or another computer device. Specifically, the control unit 13 determines a modeled shape according to the acquired three-dimensional shape data, and creates a stacking plan for forming the modeled shape with the welding beads B. FIG. The conditions for forming the welding bead B include creating a molding plan that determines the welding path (trajectory of the torch) for moving the welding torch 15, welding current when forming the welding bead B using an arc as a heat source, Setting welding conditions such as arc voltage, welding speed, feed rate of filler metal, torch angle, cooling time, composition and flow rate of shielding gas.

More specifically, the control unit 13 determines the modeled shape of the modeled object W from the three-dimensional shape data, vertically divides the modeled shape into a plurality of bead layers, A trajectory containing the bead forming path along which the welding torch 15 is moved is determined. The bead forming path and trajectory are determined by computation based on a predetermined algorithm. The bead forming path information includes, for example, path information such as the spatial coordinates of the path along which the welding torch 15 is moved, path radius, and path length, and bead information such as the bead width and bead height of the welding bead B to be formed. etc. are included. The height of the bead layer is determined according to the height of the weld bead B set according to the welding conditions.

In addition to the function of executing the above-described modeling program to model the object W and the function of generating the modeling program, the control unit 13 simulates the modeling process based on the created modeling program. It may also have a function of analyzing the temperature history, temperature distribution, etc. of the modeled object during the modelling. This temperature analysis function may be possessed by the control unit 13, but may be provided by a control unit (not shown) included in another computer device connected to the control unit 13 via a network, a communication line, or the like. There may be.

FIG. 2 is a functional block diagram of the control unit 13 having a function of analyzing the temperature of the welding bead during molding.
The control unit 13 (the same applies to other control units) includes a model generation unit 31, a molding condition acquisition unit 33, a target element selection unit 35, a temperature distribution calculation unit 37, and a temperature history, which will be described later in detail. and a calculator 39 . Each of the above-described components provided in the control unit 13 outputs the analysis result of heat transfer calculation to a monitor (not shown) based on the input information of the modeled object, outputs the analysis data, and performs analysis. Communicate the results to the operator. The operator modifies the modeling program as necessary according to the output analysis result.

FIG. 3 is an explanatory view schematically showing how the welding bead B is formed.
An arc is generated at the tip of the filler material M projecting from the welding torch 15 while moving the welding torch 15 in the welding direction WD. The generated arc melts the filler metal M to form a weld bead B on the base plate 29 along the welding direction WD. Here, an analysis shape model MD for obtaining the heat distribution around the heat input portion due to the arc when forming the welding bead B is set. This analysis shape model MD is set by taking the overall shape of the base plate 29 and the welding bead B, which is a modeled object on the base plate 29, as a model shape and dividing this model shape into a large number of elements.

FIG. 4 is a partial cross-sectional view of the modeled article schematically showing how the base plate 29 and the modeled article W formed by stacking the welding beads B are divided into a number of elements.
The analytic shape model MD is configured by dividing the outer shape of the base plate 29 and the modeled object W into, for example, a large number of rectangular parallelepiped elements Em. That is, an aggregate of a plurality of elements Em becomes a shape model used for heat transfer calculation between the base plate 29 and the modeled object W. FIG.

FIG. 5 is an explanatory diagram showing the relationship between the welding bead B and the calculation area of the analytical geometric model MD.
In this embodiment, instead of using the entire shape of the analytical geometric model MD for calculation, a method of using only a part of the shape for calculation is adopted. In this specification, the area used for calculation in the analytical geometric model MD is called "calculation area".

Here, as shown in FIG. 5, the outer edge of the temperature calculation area CA is located at both axial ends of a cylindrical body having a radius r centered at the heat input position (arc position) _PQ that forms the welding bead B. are connected to each other. The axial length Lm of the temperature calculation area CA is the length obtained by adding twice the radius r to the longitudinal length Lb of the welding bead B to be formed (Lm=Lb+2r). A plurality of elements arranged in the temperature calculation area CA of this virtual solid are the calculation target elements of the heat transfer calculation.

FIG. 6 is an explanatory view showing calculation handling elements set in the temperature calculation area CA among the elements of the analysis shape model MD, and (A) is a schematic view of the analysis shape model MD viewed from the welding direction WD It is a partial front view, and (B) is a schematic partial side view seen from a direction orthogonal to the welding direction WD.

FIG. 6A shows the metal portion including the welding bead B among the elements Em included in the temperature calculation area CA centered on the heat input position _PQ as the calculation target element Emc. Elements other than the calculation target element Emc among the elements in the temperature calculation area CA are hollow (air) portions. In order to simplify the heat transfer calculation, this element in the hollow portion is substantially excluded from the calculation by setting the boundary condition between it and the calculation target element Emc as adiabatic. Alternatively, calculation may be made so that a predetermined heat release exists between the calculation target element Emc.

The calculation target element Emc shown here is arranged in an area close to a semicircle when the analytical geometric model MD is viewed from the front.

Further, the shape of the temperature calculation area CA extends along the welding direction WD as shown in FIG. 6B. A front end portion and a rear end portion of the temperature calculation area CA in the longitudinal direction (welding direction WD) have a hemispherical shape with a radius r.

The radius r and the axial distance Lm of the temperature calculation area CA can be set to predetermined values, but they may also be set according to the range affected by heat input. That is, with respect to the radius r of the temperature calculation area CA, the larger the value of the radius r, the more elements to be calculated, so the temperature calculation accuracy improves, but the calculation time increases. On the other hand, the smaller the value of the radius r, the smaller the number of elements to be calculated, so the calculation time can be shortened, but the calculation accuracy is reduced. The same applies to the axial distance Lm. Therefore, the radius r and the axial distance Lm may be determined according to the temperature distribution centered on the arc position (heat input position) of the weld bead.

FIG. 7 is a schematic diagram showing temperature distribution due to heat transfer of each element for setting the temperature calculation area CA.
For example, the radius r of the temperature calculation area CA shown in FIG. 6A and the axial length Lm of the calculation area shown in FIG. 6B are set according to the temperature distribution of each element shown in FIG. be done. That is, the length of the range above the lower limit temperature Tb is set according to the maximum temperature Ta and its temperature distribution so that the temperature calculation is not greatly affected.

Alternatively, the radius r may be the distance from the position where the slope of the temperature distribution reaches a predetermined threshold value to the heat input position based on temperature distribution information acquired in advance from an element test or the like. Also, the size of the axial length Lm may be determined in the same manner as the radius r.
Furthermore, by setting multiple types of values for the radius r in advance and comparing the results of the temperature history of the model when the model progresses to 10 to 20% of the entire model, it is found that the heat storage temperature converges well. You may choose a value of

The shape of the temperature calculation area CA described above changes according to the bead formation trajectory (also referred to as path PS) of the welding bead.
8A to 8C are explanatory diagrams schematically showing the shape of the temperature calculation area CA.
FIG. 8A shows the temperature calculation area CA when the path PS is curved. The temperature calculation area CA in this case is curved along the axial direction, and has a circular cross-sectional area with a radius r and semispherical areas with a radius r at both ends in the axial direction.

The temperature calculation area CA shown in FIG. 8B has a substantially cylindrical shape having a circular cross section with a radius r over the entire area along the axial direction instead of the hemispherical areas at both ends in the axial direction. Also, the temperature calculation area CA shown in FIG. 8C shows the shape when the path PS is bent. The region has a circular cross-sectional shape with a radius r. Thus, the shape of the temperature calculation area CA is appropriately changed along the path PS.

Next, a specific procedure for heat transfer calculation using the above-described analytical geometric model MD will be described with reference to FIG. 2 as well.
FIG. 9 is a flow chart showing the procedure of heat transfer calculation step by step.
First, the model generation unit 31 of the control unit 13 acquires, for example, three-dimensional shape data, which is CAD data of a modeled object to be modeled, and generates the aforementioned analytical shape model MD (S1).

Next, the modeling condition acquisition unit 33 refers to a modeling plan (modeling program) that defines the modeling procedure and modeling conditions of the modeled object to be modeled, and heat input from the heat source that forms the welding bead (welding current, Welding voltage, welding speed, filler material supply speed, etc.), bead formation trajectory of the welding bead, and bead physical properties (thermal conductivity, temperature, etc.), including information on forming conditions necessary for temperature analysis (S2) .

Next, the target element selection unit 35 selects a plurality of elements centering on the position of the heat source where the welding bead is formed among the elements of the analytical geometric model MD as calculation target elements for the heat transfer calculation. In addition, boundary conditions between the selected element to be calculated for heat transfer calculation and other elements are set (S3).

FIG. 10 is a schematic explanatory view of part of the elements of the analytical geometric model MD near the heat input position _PQ , viewed from a direction orthogonal to the welding direction WD.
Here, assuming a state where a welding bead starts to be formed by an arc, elements included in a temperature calculation area CA having a circular cross section centered on the heat input position _PQ are assumed to be calculation target elements Emc for heat transfer calculation. (Elements indicated by hatching in FIG. 10). A boundary line BDL indicates the boundary between the calculation target element Emc and other elements Em other than the temperature calculation area CA.

The shape and size of each element are appropriately set according to the size of the modeled object and the target accuracy of heat transfer calculation. Here, an adiabatic condition with no heat balance is applied to the boundary between the calculation target element Emc and another element Em.

Next, three-dimensional heat transfer calculation is performed centering on the heat input position _PQ, which is the position of the heat source (S4). In other words, the heat input from the heat source is transferred to the calculation target element Emc based on the modeling conditions of the modeled object, and the temperature distribution of the temperature calculation area CA is determined based on this heat balance. For this heat transfer calculation, the following three-dimensional heat transfer basic formula (1) may be used.

Formula (1) is a basic formula for heat transfer analysis by a so-called explicit FEM (Finite Element Method). Each parameter of Formula (1) is as follows.
H: enthalpy C: reciprocal of nodal volume K: heat conduction matrix F: heat flux Q: volumetric heat generation

The amount of heat input during weld bead formation is entered as a parameter for volumetric heat generation or heat flux. According to this, nonlinear phenomena such as latent heat release can be calculated with high accuracy by using the enthalpy as an unknown quantity.

Then, the heat input position _PQ , which is the heat source position, and the temperature calculation area CA are moved according to the welding speed V and the bead formation locus (path), and the heat transfer calculation starting from the heat source is sequentially updated (S5).
11A and 11B are explanatory diagrams showing how the heat source position is moved.
In FIG. 11A, assuming that an arc as a heat source is generated at one end of the analytical geometric model MD, a temperature calculation area CA centered on the heat input position _PQ is set. Then, heat transfer calculation is performed in this state to obtain the temperature distribution in the temperature calculation area CA.

Next, assuming that the movement of the welding torch causes the arc generation position to move, the heat input position _PQ is moved along the welding direction WD. In FIG. 11B, the heat input position _PQ has moved, and the temperature calculation area CA has moved accordingly. However, the shape of the temperature calculation area CA is such that the length in the axial direction is extended because the heat input position _PQ becomes high in temperature and the heat-affected range expands. The temperature distribution of the temperature calculation area CA is obtained at each destination of the heat input position _PQ . In this way, by updating the calculation results from the start of modeling to the end of modeling, it is possible to obtain the temperature distribution and temperature history of the entire model.

According to this heat transfer calculation, since the temperature calculation area CA is limited within a predetermined range from the heat source, the calculation load can be reduced compared to the case of calculating the entire analysis shape model at once. Therefore, the calculation time required for heat transfer calculation can be greatly reduced. In addition, by simulating the shape of the welding bead with a columnar body (which may be a prism in addition to the cylinder described above) along the bead formation trajectory, compared to the case of precisely reproducing the shape of the bead cross section. , can simplify the generation of elements and contribute to speeding up calculations.

If there is an element test result, the shape and size of the temperature calculation area CA can be appropriately set by referring to the information. Also, even if there are no element test results, parameters such as the radius r and the axial distance Lm can be easily adjusted so as to speed up the calculation while maintaining appropriate accuracy.

In the above example, the boundary condition between the calculation target element Emc and the other element Em is an adiabatic condition, but the boundary condition is not limited to this.
FIG. 12 is a schematic diagram of part of the elements of the analysis shape model MD near the heat input position _PQ , viewed from a direction orthogonal to the welding direction WD, and is other than the calculation target element and the temperature calculation area CA. FIG. 11 is an explanatory diagram of a case where a boundary with an element of is applied to a heat transfer condition that causes heat transfer.

As a boundary condition between the inside and the outside of the temperature calculation area CA, a heat transfer condition that causes heat transfer such as heat transfer or heat conduction may be set. In that case, the elements outside the temperature calculation area CA may be regarded as one giant element (lattice), and the heat balance due to heat transfer with the external giant element 41 may be calculated. By doing so, it is possible to perform calculation that reproduces heat storage and heat release while suppressing an increase in the amount of calculation. Moreover, when the temperature calculation area CA is narrowed, the problem of excessive heat accumulation under the above-described adiabatic condition can be resolved.

In the analytical shape model MD illustrated in FIG. 12, calculation target elements Emc ₁ to Emc ₁₁ are in contact with the boundary line BDL of the temperature calculation area CA.
FIG. 13 is an explanatory diagram schematically showing the heat balance of the temperature calculation area CA of the analytical geometric model MD shown in FIG.
Here, the heat balance at the boundary (boundary line BDL) with the external giant element 41 is calculated. The heat flux q _i in the outward normal direction at the boundary with the external giant element 41 is obtained by Equation (2).

however,
V _elem : Volume of the external giant element k: Thermal conductivity at the boundary with the external giant element T _elem : Temperature of the external giant element T _i : Temperature of the calculation target element Emc _i in contact with the external giant element i: Calculation target element Emc number α is a fitting parameter, and any value can be adopted.

Then, the calculation of the heat balance (T _elem calculation) at the boundary with the external giant element is as follows.

here,
ΔH _elem : Enthalpy change of external giant element V _elem : Volume of external giant element Δt : Time step size k : Thermal conductivity at boundary between external giant element and calculation target element h : External giant element and outside air _Tpelem : Temperature of the external giant element at the previous time Tp _i : Temperature of the calculation target element Emc _i in contact with the external giant element at the previous time T _inf : Ambient temperature A _i : Calculation target in contact with the external giant element Area of surface where element Emc _i contacts external giant element A _out : Area of surface where external giant element contacts the outside of the object n: Number of calculation target elements Emc in contact with external giant element ΔQ _delete : Temperature calculation area CA due to movement of heat source Quantity of heat possessed by elements to be calculated that deviate from ΔQ _entry : Heat quantity possessed by elements re-entering the temperature calculation area CA due to movement of the heat source

When the above boundary conditions are used as heat transfer conditions, the amount of calculation increases compared to the case of adiabatic conditions. can be achieved. In addition, by treating the outside of the calculation area as an external giant element and calculating the heat balance, it is possible to perform calculations that reproduce heat storage and heat dissipation with high accuracy. This enables highly reliable heat transfer calculation in a short calculation time.

<Example of heat transfer calculation>
Here, the results of heat transfer calculations were compared for the case where the above boundary conditions were adiabatic conditions, the case where heat transfer conditions were used, and the case where calculation was performed in all regions without setting the temperature calculation region. .
The analysis shape model and calculation conditions used are as follows.
Number of passes: 1275
Cooling temperature between passes: Lower temperature and hold until 300°C Computational element type: Hexa-shaped element Number of elements: 135000 Total number of contacts: 143055

FIG. 14 is a graph schematically showing the results of obtaining the cooling time required for reaching the reference temperature by heat transfer calculations performed under various conditions for each bead forming pass for forming a modeled object.
Calculation results for the entire area of the shape of the modeled object without setting a temperature calculation area required a long calculation time, but a highly accurate calculation result was obtained. Therefore, the results of each condition are compared based on the results calculated for the entire region.

When the boundary conditions are adiabatic conditions (adiabatic model) and the calculation is divided into temperature calculation regions, and the radius r of the temperature calculation region is 20 mm, the cooling time is significantly longer than the result calculated for the entire region. , and it can be seen that the cooling condition cannot be reproduced.

Further, when the temperature calculation area is expanded to have a radius r of 60 mm, a result close to the result calculated in the entire area is obtained, and the same degree of cooling condition as in the case of calculation in the entire area can be reproduced.

On the other hand, when the boundary conditions are heat transfer conditions (heat transfer model) and the calculation is performed by dividing the temperature calculation region with a radius r of 20 mm, the total region It is close when calculated with In this case, it is possible to reproduce a cooling condition that is almost the same as the case where the calculation is performed for the entire area.

In this calculation example, the calculation time (the time from the start of the calculation until 10000 seconds have passed) was 551 seconds in the case of calculating the entire region, but it was 431 seconds in the heat transfer model with the temperature calculation region divided. rice field. However, the calculation time varies greatly depending on the calculation target, and the difference between the two tends to increase as the number of computational grids increases. In this calculation example, the number of elements to be calculated increased with the passage of time, and the number of grids was approximately 20,000 at 10,000 seconds after the start of calculation.

FIG. 15 is an explanatory diagram showing the result of heat transfer calculation, in which the temperature distribution during the calculation of the analytical shape model is shown in shading. FIG. 16 is a perspective view showing the result of heat transfer calculation, in which the temperature distribution of each calculation target element within the temperature calculation region is indicated by shading.
It can be seen from FIGS. 15 and 16 that the state in which the heat from the heat input position is transferred to the surrounding elements is reproduced.

The present invention is not limited to the above-described embodiments, and it is also possible for those skilled in the art to combine each configuration of the embodiments with each other, modify and apply based on the description of the specification and well-known technology. It is intended by the invention and falls within the scope for which protection is sought.

As described above, this specification discloses the following matters.
(1) Heat transfer calculation of a modeled object for calculating the heat transfer from the heat source forming the weld bead to the modeled object when the modeled object is modeled by laminating welding beads based on a preset modeling plan. a method,
obtaining an analytical shape model in which the shape of the object is divided into a plurality of elements;
a step of obtaining molding conditions including information on heat input from a heat source for forming the welding bead, bead formation trajectory of the welding bead, and bead physical properties from the molding plan;
a step of selecting, from among the plurality of elements of the analytical shape model, elements included in a temperature calculation region centered on the position of the heat source where the welding bead is formed, as calculation target elements for heat transfer calculation;
obtaining a temperature distribution in the temperature calculation area based on a heat balance in which heat from the heat source is transferred to the calculation target element based on the modeling conditions;
Move the position of the heat source in the analytical shape model along the bead formation trajectory, select the calculation target element included in the temperature calculation area centered on the movement destination position of the heat source, and select the temperature calculation area a step of repeating the calculation of the temperature distribution to obtain a temperature history during the modeling of the modeled object;
having
Heat transfer calculation method for molded objects.
According to this modeled object heat transfer calculation method, the temperature calculation area is limited to within a predetermined range from the heat source, so the calculation load can be reduced compared to the case where the entire analysis shape model is calculated at once. Therefore, the calculation time required for heat transfer calculation can be greatly reduced.

(2) The size of the temperature calculation area is set according to at least one of the amount of heat received by the element from the heat source and the amount of change in temperature with respect to the distance of the element to the heat source. heat transfer calculation method of the shaped object.
According to this modeled object heat transfer calculation method, the size of the temperature calculation region is set according to the amount of heat received by the element or the amount of change in temperature, so that the necessary calculation accuracy can be obtained efficiently.

(3) The modeling according to (2), wherein the temperature calculation area includes the element receiving more heat from the heat source than its surroundings, or the element receiving a greater amount of temperature change with respect to the distance to the heat source than its surroundings. How to calculate the heat transfer of objects.
According to this modeled object heat transfer calculation method, it is possible to omit the calculation of a region that has little effect on the temperature.

(4) The temperature calculation area extends along the bead formation trajectory and is an area composed of the calculation target elements included in a virtual solid having a circular cross section perpendicular to the axis with the position of the heat source as the central axis, ( 1) A heat transfer calculation method for a model according to any one of (3).
According to this modeled object heat transfer calculation method, the heat transfer calculation can be efficiently performed by limiting the use of the calculation target elements in the virtual solid whose axis-orthogonal cross section is circular.

(5) When the size of at least one of the radius and the axial length of the virtual solid is changed, the difference between the temperature distribution calculated with the size after the change and the temperature distribution calculated with the size before the change. The heat transfer calculation method for a model according to (4), wherein the size is set large within a range in which the temperature difference is smaller than a predetermined threshold value.
According to this modeled object heat transfer calculation method, the size of the virtual solid can be set more appropriately because the size is determined based on the actually calculated temperature distribution.

(6) In the step of calculating the temperature distribution, any of (1) to (5), wherein a thermal boundary condition between the inside and the outside of the temperature calculation area is calculated under an adiabatic condition in which heat transfer does not occur. 3. A heat transfer calculation method for a model according to claim 1.
According to this heat transfer calculation method for a modeled object, the calculation load is reduced by calculating under adiabatic conditions, and the calculation time for heat transfer calculation can be shortened.

(7) In the step of calculating the temperature distribution, any one of (1) to (5), wherein a thermal boundary condition between the inside and the outside of the temperature calculation area is calculated under heat transfer conditions that cause heat transfer. 3. A heat transfer calculation method for a model according to claim 1.
According to this heat transfer calculation method for a model, highly accurate heat transfer calculation can be performed by performing calculation under heat transfer conditions, and more accurate temperature distribution and temperature history can be obtained.

(8) the step of calculating the temperature distribution,
Considering the plurality of elements arranged outside the temperature calculation area as a single outer element,
The molding according to (7), wherein a heat balance between inside and outside of the temperature calculation region is determined between the plurality of elements arranged inside the temperature calculation region and the single outer element. How to calculate the heat transfer of objects.
According to this modeled object heat transfer calculation method, it is possible to easily reflect the influence of the heat transfer phenomenon. As a result, the number of calculation elements is smaller than the temperature calculation area required for the adiabatic conditions, so the calculation time can be shortened by the number of calculation elements saved.

(9) A method for manufacturing a shaped article, wherein the shaped article is manufactured based on the shaping plan determined by using the heat transfer calculation method for the shaped article according to any one of (1) to (8).
According to this method of manufacturing a modeled object, it is possible to create a modeling plan that takes heat transfer characteristics into account, and to manufacture a higher-quality modeled object.

(10) Calculating the heat transfer of a modeled object for calculating the heat transfer from the heat source that forms the welding bead to the modeled object when the modeled object is modeled by laminating welding beads based on a preset modeling plan. a device,
a model generation unit that obtains an analysis shape model in which the shape of the object is divided into a plurality of elements;
a molding condition acquisition unit that acquires molding conditions including heat input from a heat source for forming the welding bead, bead formation trajectory of the welding bead, and bead physical properties from the molding plan;
a target element selection unit that selects, from among the plurality of elements of the analytical shape model, elements included in a temperature calculation region centering on the position of the heat source where the welding bead is formed, as calculation target elements for heat transfer calculation; ,
a temperature distribution calculation unit that obtains a temperature distribution in the temperature calculation region based on a heat balance in which heat from the heat source is transferred to the calculation target element based on the modeling conditions;
Move the position of the heat source in the analytical shape model along the bead formation trajectory, select the calculation target element included in the temperature calculation area centered on the movement destination position of the heat source, and select the temperature calculation area a temperature history calculation unit that repeats the calculation of the temperature distribution to obtain a temperature history during the molding of the modeled object;
comprising
Heat transfer calculation device for molded objects.
According to this modeled object heat transfer calculation device, since the temperature calculation region is limited to within a predetermined range from the heat source, the calculation load can be reduced compared to the case where the entire analysis shape model is calculated at once. Therefore, the calculation time required for heat transfer calculation can be greatly reduced.

(11) A model manufacturing apparatus for manufacturing the model based on the model planning determined using the model heat transfer calculation device according to (10).
According to this modeled object manufacturing apparatus, it is possible to create a modeling plan in consideration of heat transfer characteristics, and to manufacture a higher quality modeled object.

(12) Calculating the heat transfer of a modeled object for calculating the heat transfer from the heat source that forms the welding bead to the modeled object when the modeled object is modeled by laminating welding beads based on a preset modeling plan. A program that causes a computer to perform the steps of the method,
to the computer,
A function to obtain an analysis shape model in which the shape of the object is divided into a plurality of elements;
A function of acquiring molding conditions including heat input from a heat source for forming the welding bead, bead formation trajectory of the welding bead, and bead physical properties from the molding plan;
A function of selecting, from among the plurality of elements of the analytical shape model, elements included in a temperature calculation region centered on the position of the heat source where the welding bead is formed, as calculation target elements for heat transfer calculation;
a function of determining the temperature distribution in the temperature calculation area based on the heat balance in which the heat from the heat source is transferred to the calculation target element based on the modeling conditions;
Move the position of the heat source in the analytical shape model along the bead formation trajectory, select the calculation target element included in the temperature calculation area centered on the movement destination position of the heat source, and select the temperature calculation area a function of repeating the calculation of the temperature distribution to obtain a temperature history during the molding of the modeled object;
program to make it happen.
According to this program, since the temperature calculation area is limited to within a predetermined range from the heat source, the calculation load can be reduced compared to the case of calculating the entire analytical shape model at once. Therefore, the calculation time required for heat transfer calculation can be greatly reduced.

11 molding unit 13 control unit 15 welding torch 17 welding robot 21 robot drive unit 23 filler material supply unit 25 welding power supply unit 27 reel 29 base plate 31 model generation unit 33 molding condition acquisition unit 35 target element selection unit 37 temperature distribution calculation unit 39 Temperature history calculation unit 41 External giant element B Welding bead BDL Boundary line CA Temperature calculation area Em Element Emc Calculation target element M Filler metal (welding wire)
MD Analytical shape model P _Q heat input position W Object

Claims (12)

A heat transfer calculation method for a molded object for calculating heat transfer from a heat source forming a welding bead to the molded object when the molded object is built by laminating welding beads based on a preset molding plan. hand,
obtaining an analytical shape model in which the shape of the object is divided into a plurality of elements;
a step of obtaining molding conditions including information on heat input from a heat source for forming the welding bead, bead formation trajectory of the welding bead, and bead physical properties from the molding plan;
a step of selecting, from among the plurality of elements of the analytical shape model, elements included in a temperature calculation region centered on the position of the heat source where the welding bead is formed, as calculation target elements for heat transfer calculation;
obtaining a temperature distribution in the temperature calculation area based on a heat balance in which heat from the heat source is transferred to the calculation target element based on the modeling conditions;
Move the position of the heat source in the analytical shape model along the bead formation trajectory, select the calculation target element included in the temperature calculation area centered on the movement destination position of the heat source, and select the temperature calculation area a step of repeating the calculation of the temperature distribution to obtain a temperature history during the modeling of the modeled object;
having
Heat transfer calculation method for molded objects. setting the size of the temperature calculation region according to at least one of an amount of heat received by the element from the heat source and an amount of change in temperature with respect to the distance of the element to the heat source;
The heat transfer calculation method for a modeled object according to claim 1 . The temperature calculation area includes the element that receives more heat from the heat source than its surroundings, or the element that changes in temperature with respect to the distance to the heat source more than its surroundings.
The heat transfer calculation method for a modeled object according to claim 2 . The temperature calculation area extends along the bead formation trajectory, and is an area composed of the calculation target elements included in a virtual solid with an axis-orthogonal cross section having the position of the heat source as the central axis.
A heat transfer calculation method for a model according to any one of claims 1 to 3. When the size of at least one of the radius and axial length of the virtual solid is changed, the temperature difference between the temperature distribution calculated with the size after the change and the temperature distribution calculated with the size before the change is , setting the size large within a range smaller than a predetermined threshold;
The method for calculating heat transfer of a shaped object according to claim 4. In the step of calculating the temperature distribution, a thermal boundary condition between the inside and the outside of the temperature calculation area is calculated under an adiabatic condition in which heat transfer does not occur.
A heat transfer calculation method for a model according to any one of claims 1 to 5. The step of calculating the temperature distribution calculates heat boundary conditions between the inside and the outside of the temperature calculation area under heat transfer conditions in which heat transfer occurs.
A heat transfer calculation method for a model according to any one of claims 1 to 5. The step of calculating the temperature distribution includes:
Considering the plurality of elements arranged outside the temperature calculation area as a single outer element,
8. The transmission of claim 7, wherein a heat balance between inside and outside of the temperature calculation area is determined between the plurality of elements arranged inside the temperature calculation area and the single outside element. heat calculation method. A method for manufacturing a shaped article, comprising manufacturing the shaped article based on the shaping plan determined by using the heat transfer calculation method for the shaped article according to any one of claims 1 to 8. A heat transfer calculation device for a model, which calculates heat transfer from a heat source forming a welding bead to the model when the model is modeled by laminating welding beads based on a preset modeling plan. hand,
a model generation unit that obtains an analysis shape model in which the shape of the object is divided into a plurality of elements;
a molding condition acquisition unit that acquires molding conditions including heat input from a heat source for forming the welding bead, bead formation trajectory of the welding bead, and bead physical properties from the molding plan;
a target element selection unit that selects, from among the plurality of elements of the analytical shape model, elements included in a temperature calculation region centering on the position of the heat source where the welding bead is formed, as calculation target elements for heat transfer calculation; ,
a temperature distribution calculation unit that obtains a temperature distribution in the temperature calculation region based on a heat balance in which heat from the heat source is transferred to the calculation target element based on the modeling conditions;
Move the position of the heat source in the analytical shape model along the bead formation trajectory, select the calculation target element included in the temperature calculation area centered on the movement destination position of the heat source, and select the temperature calculation area a temperature history calculation unit that repeats the calculation of the temperature distribution to obtain a temperature history during the molding of the modeled object;
comprising
Heat transfer calculation device for molded objects. A model manufacturing apparatus for manufacturing the model based on the model plan determined by using the model heat transfer calculation apparatus according to claim 10 . A procedure of a model heat transfer calculation method for calculating the heat transfer from a heat source forming a welding bead to the modeled object when the modeled object is modeled by laminating welding beads based on a preset modeling plan. A program that causes a computer to execute
to the computer,
A function to obtain an analysis shape model in which the shape of the object is divided into a plurality of elements;
A function of acquiring molding conditions including heat input from a heat source for forming the welding bead, bead formation trajectory of the welding bead, and bead physical properties from the molding plan;
A function of selecting, from among the plurality of elements of the analytical shape model, elements included in a temperature calculation region centered on the position of the heat source where the welding bead is formed, as calculation target elements for heat transfer calculation;
a function of determining the temperature distribution in the temperature calculation area based on the heat balance in which the heat from the heat source is transferred to the calculation target element based on the modeling conditions;
Move the position of the heat source in the analytical shape model along the bead formation trajectory, select the calculation target element included in the temperature calculation area centered on the movement destination position of the heat source, and select the temperature calculation area a function of repeating the calculation of the temperature distribution to obtain a temperature history during the molding of the modeled object;
program to make it happen.

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