Three-dimensional modeling method, program and structure

Abstract

In a method for three-dimensional modeling by melting powder and laminating the thin layers formed by solidifying it, deformation that occurs during modeling is suppressed. [Solution] In a powder bed type three-dimensional modeling device, a laser is irradiated onto metal powder, the powder is melted and solidified to form thin layers, and these thin layers are stacked to perform three-dimensional modeling. At this time, by changing the amount of energy by the laser irradiation, a mixture of high density layer L21 with high modeling density and porous layer L22 with low modeling density is formed. The high density layer and the porous layer can be formed in various thicknesses (test pieces P2 to P4), and the high density layer and the porous layer may be formed alternately (test pieces P6 to P9). In this way, by forming a mixture of high density layers and porous layers, it is possible to suppress distortion without reducing the mechanical strength of the shaped object.

Description

[Technical field]

[0001] The present invention relates to a method for three-dimensional modeling by laminating thin layers formed by melting and solidifying powder, and in particular to a technique for alleviating residual stress and suppressing deformation that occurs during modeling. [Background technology]

[0002] As one type of additive manufacturing in which thin layers of a specified thickness are stacked to create a three-dimensional shape, a technology is known in which powder such as metal powder is melted and solidified to create a three-dimensional shape. There are various known methods for this, such as the Powder Bed Fusion (PBF) method, the Binder Jetting (BJT) method, and the Directed Energy Deposition (DED) method.

[0003] In such three-dimensional modeling, it is known that residual stress caused by the effects of heating during melting and cooling during solidification can cause delamination, cracks, deformation and damage to the model, etc. In order to avoid or mitigate these problems, techniques have been tried, such as dividing the model into small cells and irradiating them with a laser, using a base plate in PBF that has a linear expansion coefficient close to that of the powder, and re-irradiating the modeled layer with a laser.

[0004] Patent Document 1 also discloses a technology for reducing thermal deformation and preventing warpage by embedding separately prepared block parts inside a molded object during the three-dimensional modeling process. Patent Document 2 discloses a technology for forming a boundary within a molded object, which is not directly aimed at reducing residual stress caused by heat, but which forms a solid boundary layer and a porous layer formed inside it by modulating a laser module in a technology for melting and solidifying powder to produce a composite material combining metal, plastic, and ceramic materials. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2000-190086 A [Patent Document 2] JP 2022-33816 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the problem of residual stress in three-dimensional modeling has not been sufficiently solved in the past. In particular, no technology has been established that can achieve a good balance between the requirements for suppressing distortion and the like caused by residual stress, the strength of the model, and the modeling speed in three-dimensional modeling. The present invention has been made in view of such problems. [Means for solving the problem]

[0007] The present invention relates to A three-dimensional modeling method for forming a three-dimensional object, comprising the steps of: (a) defining a shape of each layer for constructing the object with thin layers having a predetermined thickness; (b) applying a predetermined amount of energy to a powder to melt and solidify it to form said layer conforming to said shape; (c) repeating step (b) to deposit a next thin layer on top of the formed thin layer; (d) a step of controlling the amount of energy for each step (b) so that two or more layer regions having different amounts of energy are mixed in the stacking direction.

[0008] If the amount of energy used to form the thin layer is reduced, the density of the molded object will decrease, resulting in a porous shape. Conversely, if the amount of energy is increased, a solid structure will result. In this way, the amount of energy affects the density of the formed thin layer. A porous shape tends to have a relatively small residual stress, although its mechanical strength will decrease. Conversely, the more solid the structure, the greater the mechanical strength and the greater the residual stress. In the present invention, by controlling the amount of energy for each thin layer, it is possible to stack layers with different molding densities, i.e., layers with different mechanical strengths and residual stresses, and distortion of the molded object due to residual stress can be suppressed.

[0009] In the present invention, when energy is applied by laser irradiation or the like, the amount of energy can be controlled by controlling the irradiation intensity, irradiation speed, laser irradiation area, etc., either alone or in combination. "Controlling the amount of energy for each thin layer" means controlling the standard amount of energy for each thin layer, and it is also possible to adopt a method of further controlling the amount of energy depending on the location within one thin layer. Moreover, "for each thin layer" does not necessarily mean that the amount of energy is changed each time a thin layer is formed, and a plurality of adjacent thin layers may be formed with the same amount of energy. The layer region means a region consisting of one or more thin layers formed with the same amount of energy, i.e., thin layers that are considered to have the same mechanical strength and residual stress. For example, in a case where the amount of energy is changed every time five thin layers are formed, five thin layers form one layer region. The present invention can be applied to various three-dimensional modeling methods that involve melting and solidifying powder, such as the Powder Bed Fusion (PBF) method, Binder Jetting (BJT) method, and Directed Energy Deposition (DED) method.

[0010] In the three-dimensional modeling method of the present invention, Step (d) may include switching to a second amount of energy after forming the plurality of thin layers with a first amount of energy.

[0011] As explained above, the amount of energy may be changed each time a thin layer is formed, or may be changed after forming multiple thin layers, as in the above embodiment. According to the above embodiment, multiple thin layers formed with the same amount of energy form one layer region. In this embodiment, since it is not necessary to change the amount of energy for each thin layer, the modeling time can be shortened. In addition, since the layer region can be formed with a certain degree of thickness, the effect of variations in the formation state of each thin layer on the mechanical strength and residual stress of the entire model can be suppressed. In the above embodiment, the number of thin layers formed by the first energy amount can be determined arbitrarily. Also, the number of thin layers formed by the second energy amount may be one layer or multiple layers. The number of layers formed by the first energy amount and the number of layers formed by the second energy amount do not have to be the same. In the above embodiment, shaping may be performed using three or more different energy amounts.

[0012] In the three-dimensional modeling method of the present invention, The step (d) may include switching the amount of energy at least twice during the shaping process.

[0013] According to the above embodiment, three layer regions with different energy amounts are laminated, which makes it possible to form a variety of layer regions with different properties such as mechanical strength and residual stress, and thus makes it possible to flexibly adjust the properties of the entire object. In the above embodiment, the three layer regions may have different energy amounts. Also, a layer region with a first energy amount, a layer region with a second energy amount, and a layer region with a first energy amount may be stacked.

[0014] In the three-dimensional modeling method of the present invention, Step (d) may involve controlling the amount of energy so that a first layer region made of the thin layer formed by a first amount of energy and a second layer region made of the thin layer formed by a second amount of energy are alternately laminated.

[0015] In the above embodiment, the first layer region and the second layer region may be alternately laminated in any number of layers. Furthermore, the thickness of each layer region may be constant or may vary.

[0016] In the three-dimensional modeling method of the present invention, (e) determining the amount of energy to be applied to each thin layer according to a mechanical strength required for the object; The step (d) may include controlling the amount of energy according to a result of the setting in the step (e).

[0017] In the present invention, modeling is performed by mixing layer regions with different modeling densities, i.e., layer regions with different properties such as mechanical strength and residual stress. If the amount of energy is reduced and the number of layer regions with low mechanical strength is increased, the mechanical strength of the entire model is reduced. On the other hand, if the amount of energy is increased and the number of layer regions with high mechanical strength is increased, the mechanical strength of the entire model is also increased. In this way, the amount of energy affects the mechanical strength of the model. According to the above aspect, the amount of energy can be determined according to the mechanical strength required for the object, so that the object can be shaped so that the entire object satisfies the required value for mechanical strength.

[0018] In the three-dimensional modeling method of the present invention, (f) determining the amount of energy to be applied to each thin layer according to a range of distortion permitted for the object; The step (d) may include controlling the amount of energy according to a result of the setting in the step (e).

[0019] In the present invention, by increasing the number of layer regions with low density and low residual stress, the distortion of the entire object can be suppressed. On the other hand, by increasing the number of layer regions with high density and high residual stress, the distortion of the entire object increases. In this way, the amount of energy affects the density of the thin layers, and affects the distortion of the object due to residual stress. According to the above aspect, the amount of energy can be determined according to the range of distortion allowable for the object, so that the object can be shaped so that the distortion of the entire object satisfies a required value.

[0020] In general, a layer region with high mechanical strength has a tendency to have high residual stress, while a layer region with low mechanical strength has a tendency to have low residual stress. Therefore, if the amount of energy is determined based on the requirements for both the mechanical strength and residual stress of the object, it is possible to create a shape that satisfies both requirements.

[0021] The three-dimensional modeling method of the present invention includes the steps of: The step (b) is preferably applied to a three-dimensional modeling method in which the thin layers are laminated with metal powder.

[0022] The present invention is not limited to metal powders, and can be applied to various molding methods in which powder is melted and solidified. However, the problem of residual stress caused by melting is particularly important in molding methods that use metal powders. Therefore, the present invention is particularly useful for three-dimensional molding that uses metal powders.

[0023] The various features of the present invention described above do not necessarily need to be provided in their entirety, and some of them may be omitted or combined as appropriate. Furthermore, the present invention can be configured in various forms other than the above-mentioned three-dimensional modeling method.

[0024] For example, the present invention provides A three-dimensional printing apparatus for printing a three-dimensional object, comprising: an input unit that reads shape data of each layer for forming the object with thin layers having a predetermined thickness; a thin layer forming section for applying a predetermined amount of energy to a powder to melt and solidify the powder to form the thin layer according to the shape data; a lamination unit that relatively moves the thin layer formation unit and the formed thin layer so as to laminate a next thin layer on the formed thin layer; The three-dimensional modeling apparatus may further include a control unit that controls the amount of energy in the thin layer forming unit so that two or more layer regions having different amounts of energy are mixed in the stacking direction.

[0025] According to the 3D printing apparatus of the present invention, it is possible to form a thin layer by controlling the amount of energy, and therefore it is possible to realize the 3D printing method described in the present invention. The various features described in the 3D printing method can also be applied to the 3D printing apparatus of the present invention.

[0026] The present invention also provides a method for producing a semiconductor device comprising the steps of: A computer that controls a three-dimensional printing apparatus that prints a three-dimensional object, (a) receiving an input of a shape of each layer for constructing a model with thin layers having a predetermined thickness; (b) controlling a predetermined amount of energy to melt and solidify a powder to form said layer conforming to said shape; (c) repeating step (b) and controlling the deposition of a next thin layer on top of the formed thin layer; (d) controlling the amount of energy for each step (b) so that two or more layer regions having different amounts of energy are mixed in the stacking direction; The program may be a program for executing the above.

[0027] The present invention also provides a method for producing a semiconductor device comprising the steps of: (a) defining a shape of each layer for constructing a model with thin layers of a predetermined thickness; (b) applying a predetermined amount of energy to a powder to melt and solidify it to form said layer conforming to said shape; (c) repeating step (b) to deposit a next thin layer on top of the formed thin layer; (d) controlling the amount of energy for each step (b) so that two or more layer regions having different amounts of energy are mixed in the stacking direction; The object may be a three-dimensional object manufactured by a three-dimensional modeling method comprising the steps of:

[0028] The present invention also provides a method for producing a semiconductor device comprising the steps of: A profile setting method for a three-dimensional modeling apparatus that applies a predetermined amount of energy to a powder to melt the powder, solidify the powder, and stack the resulting thin layers to form a three-dimensional model, comprising the steps of: A step of reading in modeling data that stores the shape of a previously modeled object, a profile of the amount of energy applied for forming each thin layer in the modeling process of the previously modeled object, and one or both of the magnitude of distortion generated in the previously modeled object and the mechanical strength required for the previously modeled object; A step of performing a regression analysis by machine learning using the shape data, the shape data, and one or both of the distortion magnitude and the mechanical strength, as explanatory variables, and the profile data, as a response variable, to obtain a learning model; inputting required values ​​corresponding to the learning model among the requirements for the shape of the object to be formed, the magnitude of allowable distortion, and the mechanical strength; The profile setting method may include a step of setting a profile of the amount of energy in the modeling process using the learning model based on the input.

[0029] This method uses so-called machine learning to set a profile of the amount of energy to be given to each thin layer. By doing so, it is possible to easily set a profile that can satisfy requirements such as mechanical strength and distortion by utilizing past modeling results. The required values ​​may be set for both the magnitude of distortion and mechanical strength, or for either one of them. In the above embodiment, constraints may be imposed such as a condition that all layer regions are composed of a certain number of thin layers, a condition that the amount of usable energy is selected from a preset number of options, etc. By doing so, it becomes possible to easily obtain a learning model by machine learning. The "shape of the object" used in learning may be represented by the thickness in the stacking direction. Distortion may be given as distortion in the stacking direction, distortion within the plane of the layer, etc. In this way, the explanatory variables and the objective variables can be given in various ways. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is an explanatory diagram illustrating a schematic configuration of a three-dimensional modeling apparatus in an embodiment. [Diagram 2] FIG. 1 is an explanatory diagram showing a molding example in an embodiment. [Diagram 3] FIG. 13 is an explanatory diagram showing the experimental results of tensile strength. [Figure 4] 11 is an explanatory diagram showing the experimental results of tensile strength, deformation amount, and molding speed. [Diagram 5] 13 is a flowchart of a forming process. [Figure 6] 13 is a flowchart of a learning model generation process and a profile setting process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The present invention will be described in detail below with reference to an example of powder bed fusion molding. The present invention is applicable not only to this method, but also to various other molding methods that melt and solidify powder, such as BJT (Binder Jetting) and DED (Directed Energy Deposition).

[0032] A. Equipment configuration: FIG. 1 is an explanatory diagram that illustrates a schematic configuration of a three-dimensional modeling apparatus according to an embodiment of the present invention. The three-dimensional modeling apparatus 10 of the embodiment includes a modeling table 11 for forming a model, and a recoater 13 that moves back and forth above the modeling table 11 as indicated by the arrow A. When the recoater 13 moves back and forth during modeling, the surface of the modeling table 11 is covered with a substantially uniform thickness of metal powder used for modeling. The three-dimensional modeling apparatus 10 is equipped with a laser irradiation unit 15 as a mechanism for heating and melting the metal powder. The laser irradiation unit 15 is equipped with a laser light source and a mechanism for moving the irradiation site in accordance with the shape of the model. The metal powder melts in the site irradiated with the laser by the laser irradiation unit 15, and then solidifies as it cools, forming a thin layer that constitutes a part of the model. The three-dimensional modeling device 10 is equipped with a movement mechanism 12 that moves the modeling table 11 downward. After a thin layer is formed, the modeling table 11 is moved downward by the distance of one layer, and metal is dispersed by the recoater 13 and melted and solidified by the laser irradiation unit 15, so that the next layer can be laminated on the already formed thin layer. The three-dimensional modeling apparatus of the embodiment is capable of forming a three-dimensional object by repeatedly forming thin layers and stacking them in this manner.

[0033] In the process of achieving the above-mentioned modeling, the three-dimensional modeling apparatus 10 of this embodiment switches the amount of energy supplied to the metal powder by laser irradiation when forming a thin layer. Specifically, in the following embodiment, two energy amounts are used: irradiation with an energy amount for forming a thin layer in a high density state where the metal can be considered solid (hereinafter, irradiation conditions based on such energy amount will be referred to as "high density condition"), and irradiation with an energy amount for forming a thin layer with low modeling density (hereinafter, irradiation conditions based on such energy amount will be referred to as "porous condition"). Although a thin layer formed under porous conditions often becomes porous, this does not mean that it must be porous.

[0034] In this embodiment, the information that specifies the amount of energy to be applied to each thin layer is called the energy amount profile. The profile can be set in various ways, such as a mode in which the amount of energy is applied to each layer, or a mode in which the amount of energy is applied in units of a predetermined number of thin layers. The amount of energy depending on the profile can be controlled by various methods such as changing the scanning speed of the laser irradiation, changing the intensity of the laser irradiation, changing the spot area of ​​the laser irradiation, or a combination of these. In this embodiment, the method of changing the scanning speed of the laser irradiation is adopted.

[0035] In order to realize the above-mentioned modeling and energy amount control, the 3D modeling apparatus 10 has an input unit 17 and a control unit 16. These can be configured as hardware, but in this embodiment, they are configured as software by incorporating computer programs that realize each function into a computer equipped with a CPU and memory.

[0036] The input unit 17 reads shape data of the object. Since the shape of each laminated thin layer is required during modeling, the shape data may be shape data of each layer constituting the object. Alternatively, data representing the three-dimensional shape of the object may be read, and the three-dimensional modeling device 10 may generate shape data for each thin layer. In addition to the shape data, the input unit 17 also inputs requirements for the mechanical strength of the object and the tolerance for distortion during modeling. The profile of the energy amount of laser irradiation is also input through the input unit 17. The profile may be set and input by an operator, for example, or may be set using artificial intelligence.

[0037] The control unit 16 controls the operation of the three-dimensional modeling device 10 to control the laser irradiation unit 15 to By controlling the irradiation, i.e. the amount of energy supply, a shaped object is formed in which layers under high density conditions and porous conditions are mixed. As mentioned above, the control unit 16 can be configured as software by incorporating a program into a computer. Such a program can be, for example, (a) receiving an input of a shape of each layer for constructing a model with thin layers having a predetermined thickness; (b) controlling a predetermined amount of energy to melt and solidify a powder to form said layer conforming to said shape; (c) repeating step (b) and controlling the deposition of a next thin layer on top of the formed thin layer; (d) controlling the amount of energy for each step (b) so that two or more layer regions having different amounts of energy are mixed in the stacking direction; The program may be a program for executing the above. Such a program may be pre-installed in the control unit 16, or may be distributed separately. For example, the program may be stored in a storage medium and distributed, or may be provided via a communication line.

[0038] In this embodiment, a profile is set using artificial intelligence. The diagram also shows the configuration of a profile setting device 20 for setting a profile. Each component in the diagram can be prepared as hardware, but in this embodiment, each component is configured as software by installing a program that realizes each function in a computer. In the illustrated example, the profile setting device 20 is shown as a single device, but it may be configured by connecting a plurality of computers, servers, etc. via a network to provide each function.

[0039] The modeling database 21 provided in the profile setting device 20 stores modeling data representing past modeling results. The content of the modeling data can be determined arbitrarily, and may be, for example, the shape of the modeled object, its mechanical strength, the magnitude of distortion during modeling, the profile used for modeling, etc. The shape of the modeled object may be a three-dimensional shape, or may be represented by a parameter such as the thickness in the stacking direction. The mechanical strength may be represented by various indices such as tensile strength and bending strength. The magnitude of distortion may also be represented by parameters such as the distortion in the stacking direction or the distortion within a layer.

[0040] The machine learning unit 23 uses the modeling database 21 to generate a learning model through machine learning regression. The purpose of machine learning is to create a learning model that gives a profile that can realize required values, such as mechanical strength and the magnitude of distortion, of a future model to be modeled, when these are specified. Therefore, machine learning is performed with the shape, mechanical strength, distortion, etc. as explanatory variables and the profile as the objective variable. Machine learning can be performed using various algorithms. The generated learning model is stored in the profile setting device 20.

[0041] The required value input unit 22 inputs required values ​​of the object to be modeled, such as mechanical strength, tolerance of distortion, etc. It is preferable that the required values ​​have a format that matches that of the modeling data used by the machine learning unit 23 for machine learning. The profile generation unit 24 uses the learning model generated by the machine learning unit 23 to generate a profile of the amount of energy to be supplied to the model. It is not necessary to perform the machine learning and the generation of the profile at the same time. A learning model may be generated in advance by machine learning and saved. The profile thus generated is passed to the three-dimensional modeling device 10 and used for modeling.

[0042] In order to easily realize the machine learning and profile generation, some constraints may be set. First, in this embodiment, the amount of energy supply is limited to two conditions, high density condition and porous condition. Also, the amount of energy is not changed for each layer, but is changed for a certain number of layers. Furthermore, only one of the mechanical strength and the distortion may be used as the required value, which makes it possible to relatively easily create a learning model.

[0043] As described above, according to the three-dimensional printing apparatus 10 of this embodiment, by controlling the amount of energy of laser irradiation using the profile set by the profile setting device 20, it is possible to print a mixture of a layer formed under high-density conditions (hereinafter referred to as a "high-density layer") and a layer formed under porous conditions (hereinafter referred to as a "porous layer").

[0044] B. Experimental results: Next, the inventors conducted an experiment to examine the effect on the mechanical strength and distortion of a shaped object of the mixture of a high density layer and a porous layer. The results will be described below.

[0045] Fig. 2 is an explanatory diagram showing a modeling example in the embodiment. It shows a schematic diagram of the layer structure of test pieces P1 to P9 used in the experiment. Hereinafter, a layer formed at one time by the three-dimensional modeling apparatus 10 will be referred to as a "thin layer," and a portion where multiple thin layers formed under the same conditions are stacked will be referred to as a "layer region." In this embodiment, the energy amounts of the high density layer and the porous layer were controlled by changing the scanning speed of the laser irradiation. Specifically, the scanning speed when forming the porous layer was twice as fast as the scanning speed when forming the high density layer.

[0046] The test piece P1 is formed entirely of high density layers. The bottom part Lb0 is formed of 20 high density layers. The upper part Lu0 is formed of 10 high density layers. The layer region L1 of the main body is formed of 100 high density layers. The proportion of high density layers in the main body is 100%.

[0047] The bottom part Lb1 of the test piece P2 is a porous layer of 20 layers. The main body is composed of a layer region L21 formed of 75 high density layers and a layer region L22 formed of 25 porous layers. The upper part Lu0 is the same as the test piece P1. The proportion of the high density layer in the main body is 75%.

[0048] The bottom part Lb1 and the top part Lu0 of the test piece P3 are the same as those of the test piece P2. The main body is composed of a layer region L31 formed of 50 high density layers and a layer region L32 formed of 50 porous layers. The proportion of the high density layers in the main body is 50%.

[0049] The bottom part Lb1 and the top part Lu0 of the test piece P4 are the same as those of the test piece P2. The main body is composed of a layer region L41 formed of 25 high density layers and a layer region L42 formed of 75 porous layers. The proportion of the high density layers in the main body is 25%.

[0050] The test piece P5 has a bottom Lb1 formed of 20 porous layers and an upper Lu0 formed of 10 porous layers. The main body is composed of a layer region L5 formed of 100 porous layers. The proportion of the high density layer in the main body is 0%.

[0051] In the test piece P6, the bottom Lb0 is formed of 20 high density layers, and the top Lu0 is formed of 10 high density layers. The main body is formed by alternately stacking a layer region L61 formed of 25 high density layers, a layer region L62 formed of 50 porous layers, and a layer region L63 formed of 25 high density layers. The proportion of high density layers in the main body is 50%.

[0052] In the test piece P7, the bottom Lb0 is formed of 20 high density layers, and the top Lu0 is formed of 10 high density layers. The main body is formed by alternating high density layer layer regions and porous layer layer regions every 10 layers, such as layer region L71 formed of 10 high density layers and layer region L72 formed of 10 porous layers. The main body is 100 layers thick in total. The proportion of high density layers in the main body is 50%.

[0053] In the test piece P8, the bottom Lb0 is formed of 20 high density layers, and the top Lu0 is formed of 10 high density layers. The main body is formed of layer regions of high density layers and layer regions of porous layers, each layered in alternating layers of 5 layers, such as layer region L81 formed of 5 high density layers and layer region L82 formed of 5 porous layers. The main body is 100 layers thick in total. The proportion of high density layers in the main body is 50%.

[0054] In the test piece P9, the bottom Lb0 is formed of 20 high density layers, and the top Lu0 is formed of 10 high density layers. The main body is formed by alternating high density layer layer regions and porous layer layer regions every 5 layers, such as layer region L91 formed of 2 high density layers and layer region L92 formed of 2 porous layers. The main body is 100 layers thick in total. The proportion of high density layers in the main body is 50%.

[0055] As described above, in this embodiment, the high density layer and the porous layer can be formed in various ways. As in the case of the test pieces P2 to P4, the high density condition and the porous condition may be switched only once when stacking the shaped objects. As in the case of the test pieces P6 and the test pieces P7 to P9, the high density condition and the porous condition may be switched two or more times, or the high density layer and the porous layer may be formed alternately. In this embodiment, two types of energy amounts, high density conditions and porous conditions, are selectively used, but when three or more types of energy amounts are used, even more diverse switching is possible.

[0056] Fig. 3 is an explanatory diagram showing the experimental results of tensile strength. It shows the relationship between the proportion of high density layer and tensile strength. As shown in the figure, it can be seen that as the proportion of high density layer increases, the tensile strength increases almost linearly. However, it can be seen that when the high density layer is around 50%, the tensile strength is affected depending on the thickness of the high density layer and the porous layer.

[0057] FIG. 4 is an explanatory diagram showing the experimental results of tensile strength, deformation amount, and molding speed. Figure 4(a) shows the experimental results of the tensile strength. It shows the same results as in Figure 3 in a different form. Looking at the results R1 for test pieces P1 to P5, it can be seen that the tensile strength gradually decreases. Test pieces P1 to P5 are test pieces in which the proportion of the high density layer was gradually decreased under conditions where the high density conditions and the porous conditions were switched at most once. As can be seen in Figure 3, these test pieces confirm that the proportion of the high density layer and the tensile strength change almost linearly. Next, we consider the results R2 of specimens P3 and P6 to P9. The proportion of the high density layer in these specimens is approximately 50%, and the thickness of the high density layer and the porous layer are different. According to this result, it can be seen that specimen P9, which is composed of the thinnest layer, has a tensile strength similar to that of specimen P1. Considering that the layer thickness of specimens P7 to P9 gradually decreases, it seems that from the viewpoint of tensile strength, it is preferable for each layer to be thin. However, since specimen P7, which has thinner layers than specimen P6, has a slightly lower tensile strength, it cannot be said with certainty that there is a linear relationship between layer thickness and tensile strength.

[0058] Figure 4(b) shows the experimental results of the deformation of the test specimens. The positive side represents downward convex deformation, and the negative side represents upward convex deformation. Looking at the results R3 for test specimens P6 to P9, it can be seen that the deformation amount is affected by the thickness of the layer region, even when the proportion of the high-density layer is 50%. For test specimens P6 to P8, the deformation amount decreases as the layer region becomes thinner. However, for test specimen P9, the deformation amount is large even though the layer region is the thinnest. Also, even when looking at the results of test pieces P1 to P5, it is confirmed that the proportion of the high density layer affects the amount of deformation, but it is not possible to determine conclusively what correlation exists. The amount of deformation is due to residual stresses that accompany the heating and cooling during the molding process. However, in the case of the powder bed method used in this embodiment, it is believed that the residual stresses are also affected by the transfer of heat to the molding table 11, and therefore it is considered necessary to comprehensively analyze various factors.

[0059] Figure 4(c) shows the experimental results of the printing speed of the test pieces. This experiment was conducted only for test pieces P1 and P7 to P9. According to this result, when printing a mixture of high-density and porous layers, as in test pieces P7 to P9, the scanning speed of the porous layer is faster than that of the high-density layer, so there is an advantage in that the printing speed is faster than when all layers are high-density layers (test piece P1). However, it was confirmed that the printing speed is slightly reduced by making each layer thin, as in test pieces P7 to P9.

[0060] Based on the experimental results shown above, it was confirmed that when performing 3D modeling, the tensile strength, deformation amount, and modeling speed are each affected by changing the ratio of high-density and low-density layers and the thickness of each layer. In other words, by controlling the amount of energy, it is possible to perform modeling that appropriately satisfies the requirements for the mechanical strength, distortion tolerance, etc. required for the object.

[0061] C. Modeling process: Next, a process for modeling using the three-dimensional modeling apparatus 10 of this embodiment will be described. 5 is a flowchart of the modeling process, which is executed by the control unit of the three-dimensional modeling apparatus 10. When the process starts, the 3D printing device 10 first reads shape data of the object (step S10). This shape data is data that defines the shape of each thin layer when the object is constructed as a laminate of thin layers. When the shape data is three-dimensional data of the object, the 3D printing device 10 needs to generate shape data of the thin layers based on the three-dimensional data.

[0062] Next, the 3D modeling device 10 sets a profile of the amount of energy (step S11). In this embodiment, as described later, the profile set by the profile setting device 20 is read. Alternatively, the profile may be manually set by an operator of the 3D modeling device 10.

[0063] Once the above processing is completed, the 3D modeling device 10 starts the modeling process. First, the first thin layer is formed (step S12). As described in FIG. 1, the method of forming the thin layer is to irradiate the laser according to the shape data, and melt and solidify the metal powder. This laser irradiation is performed under either high density conditions or porous conditions according to the profile. If modeling is not completed after forming a thin layer (step S13), the 3D modeling device 10 sets the energy amount for the next thin layer according to the profile (step S14). This process does not mean that the energy amount must be switched for each layer. If the next layer is also irradiated with the same energy amount, there is no need to switch the energy amount. The three-dimensional modeling device 10 repeatedly executes the above process until modeling is completed (step S13).

[0064] In this embodiment, the energy amount profile is set by machine learning, and the method for doing so will be described below. Fig. 6 is a flowchart of a learning model generation process and a profile setting process. Each process is executed by the profile setting device 20. However, as described in Fig. 1, the profile setting device 20 does not need to be a single device, and may be configured by connecting multiple computers, servers, etc. via a network.

[0065] First, a learning model generation process executed by the profile setting device 20 will be described. When this process starts, the profile setting device 20 reads past shaping data from the shaping database (step S20). The shaping data may be, for example, the shape of the shaped object, its mechanical strength, the magnitude of distortion during shaping, the profile used for shaping, and the like.

[0066] Then, the profile setting device 20 generates a learning model by machine learning regression (step S21), and stores the obtained learning model (step S22). This learning model is intended to provide a profile that realizes requirements such as mechanical strength, the magnitude of distortion during modeling, etc. Various methods can be adopted as an algorithm for generating the learning model.

[0067] Next, a profile setting process will be described. This process is carried out to determine a profile when an object is to be formed. When the process starts, the profile setting device 20 reads required values ​​(step S30). The required values ​​may be the mechanical strength or the allowable range of distortion for the shape of the shaped object. Next, the profile setting device 20 reads the learning model generated in the learning model generation process (step S31). Then, the profile of the amount of energy is set using the learning model (step S32). The set profile is output to the three-dimensional modeling device 10 (step S33).

[0068] In the above process, it is not necessary to generate a learning model when executing the profile setting process, but the learning model may be generated in advance. Also, a learning model that has been generated once may be used continuously.

[0069] According to the present embodiment described above, when melting and solidifying metal powder to form a shape, by mixing layers with different amounts of energy, that is, high density conditions and porous conditions, it is possible to suppress distortion due to residual stress. In addition, depending on the profile settings, it is also possible to suppress distortion while satisfying the mechanical strength requirements. Therefore, according to the present embodiment, it is possible to improve the accuracy of three-dimensional modeling and improve its convenience.

[0070] In addition, in this embodiment, a profile can be set by machine learning, which makes it possible to set an appropriate profile that satisfies required values ​​for mechanical strength, distortion, and the like.

[0071] The various features described in the present embodiment do not necessarily have to be all present, and some of them may be omitted or combined as appropriate. Also, the present invention is not limited to the embodiments, and various modified examples are possible. For example, the amount of energy is not limited to two conditions, high density condition and porous condition, as in the embodiment, and more various conditions may be set. The present invention is not limited to the powder bed method as in the embodiment, but can be applied to various molding methods in which powder is melted and solidified. [Industrial Applicability]

[0072] INDUSTRIAL APPLICABILITY The present invention can be used to suppress deformation that occurs during modeling in a method for three-dimensional modeling by laminating thin layers formed by melting and solidifying powder. [Explanation of symbols]

[0073] 10 3D printing equipment 11 Modeling Table 12 Moving mechanism 13 Recoater 15 Laser irradiation section 16 Control section 17 Input section 20 Profile setting device 21 Modeling Database 22 Requirement value input section 23 Machine Learning Department 24 Profile Generation Unit

Claims

1. A three-dimensional modeling method for forming a three-dimensional object, comprising the steps of: (a) defining a shape of each layer for constructing the object with thin layers having a predetermined thickness; (b) applying a predetermined amount of energy to a powder to melt it and solidify it to form said layer conforming to said shape; (c) repeating step (b) to deposit a next thin layer on top of the formed thin layer; (d) controlling the amount of energy for each step (b) so that two or more layer regions having different amounts of energy are mixed in the stacking direction; (f) setting the amount of energy to be applied to each thin layer in accordance with a range of distortion permitted for the object; The step (d) is a three-dimensional modeling method for controlling the amount of energy in accordance with the setting result of the step (f).

2. The three-dimensional modeling method according to claim 1, The step (d) includes forming the thin layers with a first amount of energy, and then switching to a second amount of energy.

3. The three-dimensional modeling method according to claim 1, The step (d) is a three-dimensional modeling method in which the amount of energy is switched at least twice during the modeling process.

4. The three-dimensional modeling method according to claim 1, The step (d) is a three-dimensional modeling method in which the amount of energy is controlled so that a first layer region consisting of the thin layer formed by a first amount of energy and a second layer region consisting of the thin layer formed by a second amount of energy are alternately stacked.

5. The three-dimensional modeling method according to claim 1, further comprising: (e) determining the amount of energy to be applied to each thin layer according to a mechanical strength required for the object; The step (d) is a three-dimensional modeling method for controlling the amount of energy in accordance with the setting result of the step (e).

6. The three-dimensional modeling method according to claim 1, The step (b) is a three-dimensional modeling method in which the thin layers are laminated using metal powder.

7. A three-dimensional printing apparatus for printing a three-dimensional object, comprising: an input unit that reads shape data of each layer for forming the object with thin layers having a predetermined thickness; a thin layer forming section that applies a predetermined amount of energy to a powder to melt and solidify it to form the thin layer according to the shape data; a lamination unit that relatively moves the thin layer formation unit and the formed thin layer so as to laminate a next thin layer on the formed thin layer; a control unit that controls the amount of energy in the thin layer forming unit so that two or more layer regions having different amounts of energy are mixed in the stacking direction, The control unit is The amount of energy to be applied to each thin layer is set according to a range of distortion allowed for the object, and the amount of energy is controlled according to the setting result. Three-dimensional printing equipment.

8. A computer that controls a three-dimensional printing apparatus that prints a three-dimensional object, (a) receiving an input of a shape of each layer for constructing a model with thin layers having a predetermined thickness; (b) controlling a predetermined amount of energy to melt and solidify a powder to form said layer conforming to said shape; (c) repeating step (b) and controlling the deposition of a next thin layer on top of the formed thin layer; (d) controlling the amount of energy for each step (b) so that two or more layer regions having different amounts of energy are mixed in the stacking direction; (f) setting the amount of energy to be applied to each thin layer in accordance with a range of distortion permitted for the object; In the step (d), a program is provided for controlling the amount of energy in accordance with the setting result in the step (f).

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