Three dimensional shaping method, program, and structure

Abstract

To suppress deformation occurring during shaping in a method for three dimensional shaping by laminating thin layers formed by melting and solidifying powder.SOLUTION: In a powder bed type three dimensional shaping apparatus, metal powder is irradiated with a laser, the powder is melted and solidified to form a thin layer, and the thin layer is laminated to perform three dimensional shaping. At this time, a high-density layer L21 having a high density and a porous-density layer L22 having a low density are formed in a mixed manner by changing the amount of energy of laser irradiation. The high density layer and the microporous layer can be formed in various thicknesses (test pieces P2 to P4), and the high density layer and the microporous layer may be alternately formed (test pieces P6 to P9). In this way, by forming the high-density layer and the porous layer in a mixed manner, it is possible to suppress distortion without lowering the mechanical strength of the shaped article.SELECTED DRAWING: Figure 2

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] One known additive manufacturing technique for creating three-dimensional shapes by stacking thin layers of a predetermined thickness is to melt and solidify powder, such as metal powder, to create three-dimensional shapes. Various methods are known for this purpose, including Powder Bed Fusion (PBF), Binder Jetting (BJT), and Directed Energy Deposition (DED).

[0003] In such three-dimensional modeling, it is known that residual stresses caused by the effects of heating during melting and cooling during solidification can lead to delamination, cracks, deformation or breakage of the model. To avoid or mitigate these problems, attempts have been made to separate the model into small cells and irradiate them with a laser, to use a base plate in PBF that has a linear expansion coefficient close to that of the powder, and to re-irradiate the modeled layers with a laser.

[0004] Furthermore, Patent Document 1 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.Although not directly aimed at alleviating residual stress caused by heat, Patent Document 2 discloses a technology for forming a boundary within a molded object, in which a solid boundary layer and a porous layer formed within it are formed 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] Japanese Patent Application Laid-Open No. 2000-190086 [Patent Document 2] Japanese Patent Publication No. 2022-33816 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 particular, no technology has been established that can achieve a good balance between the requirements for suppressing distortion and other issues associated with residual stress, the strength of the model, and the modeling speed. The present invention has been made in light of this problem. [Means for solving the problem]

[0007] The present invention provides A three-dimensional modeling method for forming a three-dimensional object, comprising: (a) defining the shape of each layer to configure the object with thin layers having a predetermined thickness; (b) applying a predetermined amount of energy to the powder to melt and solidify it to form the thin layer conforming to the 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 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 lower mechanical strength, but relatively small residual stress. 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, thereby suppressing distortion of the molded object due to residual stress.

[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 use a method of further controlling the amount of energy depending on the location within one thin layer. Furthermore, "for each thin layer" does not necessarily mean that the amount of energy is changed for each thin layer formed, and a plurality of adjacent thin layers may be formed with the same amount of energy. A layer region refers to 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, if the amount of energy is changed every time five thin layers are formed, five thin layers will form one layer region. The present invention can be applied to various three-dimensional modeling methods that involve melting and solidifying powder, such as PBF (Powder Bed Fusion), BJT (Binder Jetting), and DED (Directed Energy Deposition).

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

[0011] As explained above, the amount of energy may be changed each time a thin layer is formed, or, as in the above embodiment, it may be changed after forming multiple thin layers. 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 molding time can be shortened. Furthermore, since the layer region can be formed with a certain thickness, the impact of variations in the formation state of each thin layer on the mechanical strength and residual stress of the entire molded object can be suppressed. In the above embodiment, the number of thin layers formed with the first energy amount can be determined arbitrarily. The number of thin layers formed with the second energy amount can be one or more. The number of layers formed with the first energy amount does not have to be the same as the number of layers formed with the second energy amount. In the above embodiment, shaping may be performed using three or more different amounts of energy.

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

[0013] According to the above-described 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 flexibly adjust the properties of the entire object. In the above embodiment, the three layer regions may have different energy amounts, or may be stacked in the order of 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.

[0014] In the three-dimensional modeling method of the present invention, Step (d) may control the amount of energy so that first layer regions made of the thin layers formed with a first amount of energy and second layer regions made of the thin layers formed with a second amount of energy are alternately stacked.

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

[0016] The three-dimensional modeling method of the present invention further comprises: (e) determining the amount of energy to be applied to each thin layer according to the mechanical strength required for the object; Step (d) may control the amount of energy according to the setting result of step (e).

[0017] In the present invention, layer regions with different build densities, i.e., layer regions with different properties such as mechanical strength and residual stress, are mixed together to form the object. 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 object will decrease. 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 object will also increase. In this way, the amount of energy affects the mechanical strength of the object. According to the above aspect, the amount of energy can be determined depending on the mechanical strength required for the object, and therefore, the object can be shaped so that the entire object satisfies the required mechanical strength.

[0018] The three-dimensional modeling method of the present invention further comprises: (f) determining the amount of energy to be applied to each thin layer according to the range of distortion allowed for the object; Step (d) may control the amount of energy according to the setting result of step (e).

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

[0020] Generally, layer regions with high mechanical strength tend to have high residual stress, while layer regions with low mechanical strength tend 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 step (b) is preferably applied to a three-dimensional fabrication method in which the thin layers are laminated using metal powder.

[0022] The present invention is applicable not only to metal powders but also to various other molding methods that involve melting and solidifying powders. However, the issue 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-described 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 to configure the object with thin layers of a predetermined thickness; a thin layer forming unit that applies a predetermined amount of energy to the powder to melt and solidify it, thereby forming the thin layer according to the shape data; a lamination unit that moves the thin layer formation unit and the formed thin layer relatively to each other 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] The 3D modeling apparatus of the present invention can form thin layers by controlling the amount of energy, which makes it possible to realize the 3D modeling method described in the present invention. The various features described in the 3D modeling method can also be applied to the 3D modeling apparatus of the present invention.

[0026] The present invention also provides 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 of a predetermined thickness; (b) applying a controlled amount of energy to the powder to melt and solidify it to form the thin layer conforming to the 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) defining the shape of each layer to construct a shaped object from thin layers of a predetermined thickness; (b) applying a predetermined amount of energy to the powder to melt and solidify it to form the thin layer conforming to the 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 3D object manufactured by a 3D modeling method comprising the steps of:

[0028] The present invention also provides A profile setting method for a three-dimensional modeling apparatus that applies a predetermined amount of energy to powder to melt it, solidify it, and stack the resulting thin layers to form a three-dimensional model, the method comprising: a step of reading in modeling data that stores the shape of a previously modeled object, a profile of the amount of energy applied to form 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 based on the shaping data, using one or both of the magnitude of the distortion and the mechanical strength, and the shape as explanatory variables, and the profile as a response variable, to obtain a learning model; a step of inputting required values ​​corresponding to the learning model among the shape of the object to be formed, the magnitude of allowable distortion, and the mechanical strength requirements; 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 the profile of the amount of energy to be applied to each thin layer. By doing so, it is possible to easily set a profile that satisfies requirements such as mechanical strength and distortion by utilizing past modeling results. The required values ​​can be set for both the magnitude of distortion and mechanical strength, or for just one of them. In the above-mentioned embodiment, constraints may be imposed, such as a condition that all layer regions are composed of a certain number of thin layers, or a condition that the amount of available energy must be selected from a preset number of options, etc. This makes it possible to easily obtain a learning model through machine learning. Furthermore, the "shape of the object" used in learning may be represented by the thickness in the stacking direction. Distortion may also be given as distortion in the stacking direction or distortion within the plane of the layer. In this way, explanatory variables and objective variables can be given in various ways. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is an explanatory diagram schematically illustrating a configuration of a three-dimensional modeling apparatus in an embodiment. [Figure 2] FIG. 10 is an explanatory diagram showing a molding example in the embodiment. [Figure 3] FIG. 10 is an explanatory diagram showing the experimental results of tensile strength. [Figure 4] 10A and 10B are explanatory diagrams showing experimental results of tensile strength, deformation amount, and molding speed. [Figure 5] 10 is a flowchart of a forming process. [Figure 6] 10 is a flowchart of a learning model generation process and a profile setting process. DETAILED DESCRIPTION OF THE INVENTION

[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 illustrating a schematic configuration of a three-dimensional modeling apparatus according to an embodiment. 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 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 this metal powder. The laser irradiation unit 15 includes a laser light source and a mechanism for moving the irradiation area in accordance with the shape of the model. The metal powder melts in the area irradiated with the laser by the laser irradiation unit 15, and then solidifies as it cools, forming a thin layer that constitutes 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 forming a thin layer, 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, allowing the next layer to be stacked on top of the thin layer that has already been formed. The three-dimensional modeling apparatus of the embodiment can form a three-dimensional object by repeatedly forming thin layers and stacking them in this way.

[0033] The three-dimensional printing apparatus 10 of this embodiment switches the amount of energy supplied to the metal powder by laser irradiation when forming a thin layer in the process of achieving the above-mentioned printing. 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 conditions"), and irradiation with an energy amount for forming a thin layer with a low printing density (hereinafter, irradiation conditions based on such energy amount will be referred to as "porous conditions"). Although a thin layer formed under porous conditions often ends up in a porous state, this does not necessarily mean that it must be porous.

[0034] In this embodiment, the information specifying the amount of energy to be applied to each thin layer is called the "energy profile." The profile can be set in various ways, such as by applying the amount of energy to each layer or by applying the amount of energy to a predetermined number of thin layers. The amount of energy can be controlled according to the profile in various ways, such as by changing the scanning speed of the laser irradiation, by changing the intensity of the laser irradiation, by changing the spot area of ​​the laser irradiation, or by 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 also 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 that constitutes 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 the required mechanical strength of the object, the required tolerance for distortion during modeling, and the like. The profile of the energy amount of laser irradiation is also input to the input unit 17. The profile may be set and input by an operator, or may be set using artificial intelligence, for example.

[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 supplied, an object is formed in which layers formed under high density conditions and porous conditions are mixed. As mentioned above, the control unit 16 can be configured as software by installing a program in 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 of a predetermined thickness; (b) applying a controlled amount of energy to the powder to melt and solidify it to form the thin layer conforming to the 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 independently. 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 on a computer. Although the example in the figure shows a single device, the profile setting device 20 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 include, for example, the shape of the modeled object, its mechanical strength, the magnitude of distortion during modeling, and the profile used for modeling. 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. Various indicators such as tensile strength and bending strength can be used for the mechanical strength. The magnitude of distortion may also be expressed by parameters such as the distortion in the stacking direction or the distortion within a layer.

[0040] The machine learning unit 23 generates a learning model through machine learning regression using the modeling database 21. The purpose of machine learning is to create a learning model that provides a profile that can achieve required values, such as mechanical strength and distortion magnitude, of a future object to be modeled, when those values ​​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 formed, such as mechanical strength, tolerance of distortion, etc. It is preferable that the required values ​​have the same format as the forming 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 machine learning and profile generation simultaneously. 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 example, the amount of energy supplied is limited to two conditions: high density condition and porous condition. Furthermore, the amount of energy is not changed for each layer, but is changed in units of a predetermined number of layers. Furthermore, only one of the mechanical strength and the strain 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 the laser irradiation using the profile set by the profile setting device 20, it is possible to print a mixture of layers formed under high-density conditions (hereinafter referred to as "high-density layers") and layers formed under porous conditions (hereinafter referred to as "porous layers").

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

[0045] Figure 2 is an explanatory diagram showing a modeling example in the working example. 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 device 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 example, 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 for forming the porous layer was set to twice the scanning speed for forming the high-density layer.

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

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

[0048] Specimen P3 has the same bottom Lb1 and top Lu0 as specimen P2. The main body is composed of layer region L31, which is made up of 50 high-density layers, and layer region L32, which is made up of 50 porous layers. The proportion of high-density layers in the main body is 50%.

[0049] Specimen P4 has the same bottom Lb1 and top Lu0 as specimen P2. The main body is composed of layer region L41, which is made up of 25 high-density layers, and layer region L42, which is made up 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 consisting of 20 porous layers and an upper Lu0 consisting of 10 porous layers. The main body is composed of a layer region L5 consisting of 100 porous layers. The proportion of high-density layers in the main body is 0%.

[0051] In specimen 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 alternating layer regions L61, L62, L63, L64, L65, L66, L67, L68, L69, L70, L71, L72, L73, L74, L75, L76, L77, L78, L79, L80, L81, L82, L83, L84, L85, L86, L87, L88, L89, L90, L91, L92, L93, L94, L95, L96, L97, L98, L99, L99, L100, L101, L102, L103, L104, L105, L106, L107, L10

[0052] In specimen 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 layers of 10 high-density layers and layers of porous 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 specimen 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 by alternating layers of high-density layers and porous layers, with layer region L81 being formed of 5 high-density layers and layer region L82 being 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 specimen 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 regions and porous layer regions every five layers, such as layer region L91 formed of two high-density layers and layer region L92 formed of two 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 example, the high-density layer and the porous layer can be formed in various ways. As with specimens P2 to P4, the high-density condition and the porous condition may be switched only once when stacking the shaped objects. Alternatively, as with specimens P6 and 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 example, 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] Figure 3 is an explanatory diagram showing the experimental results of tensile strength. It shows the relationship between the proportion of high-density layers and tensile strength. As shown in the figure, as the proportion of high-density layers increases, the tensile strength increases almost linearly. However, when the high density layer is around 50%, it is clear that 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 format. Looking at result R1 for test pieces P1 to P5, we can see 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 in which 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 will examine the results (R2) for specimens P3 and P6-P9. These specimens have a high-density layer ratio of approximately 50%, with the thickness of the high-density and porous layers varying. These results show that specimen P9, which has the thinnest layers, achieved a tensile strength comparable to that of specimen P1. Considering that specimens P7-P9 have gradually thinner layers, it seems that thinner layers are preferable from the perspective of tensile strength. However, specimen P7, which has thinner layers than specimen P6, exhibited a slightly lower tensile strength, so it cannot be concluded with certainty that there is a linear relationship between layer thickness and tensile strength.

[0058] Figure 4(b) shows the experimental results for 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 thickness of the layer region affects the deformation amount, 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. Furthermore, even when the results of test pieces P1 to P5 are examined, it is confirmed that the proportion of the high-density layer affects the amount of deformation, but it is not possible to determine what correlation exists. The amount of deformation is due to residual stress caused by heating and cooling during the molding process, but in the case of the powder bed method used in this embodiment, it is believed that the residual stress is also affected by the transfer of heat to the molding table 11, so 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 on test pieces P1 and P7 to P9. These results show that when printing a mixture of high-density and porous layers, as in test pieces P7 to P9, the scanning speed of the porous layers is faster than that of the high-density layers, which has the advantage of faster printing speed compared to when all layers are high-density (test piece P1). However, it was confirmed that the printing speed was slightly reduced by making each layer thinner, as in test pieces P7 to P9.

[0060] Based on the experimental results shown above, it was confirmed that when performing three-dimensional printing, the tensile strength, deformation amount, and printing speed are all affected by changing the ratio of high-density to low-density layers and the thickness of each layer. In other words, by controlling the amount of energy, it is possible to print objects that appropriately satisfy the requirements for mechanical strength, distortion tolerance, etc.

[0061] C.Modeling process: Next, a process for performing 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 the shape data of the object (step S10). This shape data defines the shape of each thin layer when the object is constructed as a stack of thin layers. If 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 apparatus 10 sets an energy amount profile (step S11). In this embodiment, as will be described later, the profile set by the profile setting device 20 is read. Alternatively, the profile may be set manually by an operator of the 3D modeling apparatus 10.

[0063] Once the above process is complete, the 3D modeling device 10 starts the modeling process. First, the first thin layer is formed (step S12). As explained in FIG. 1, the thin layer is formed by irradiating a laser according to the shape data, melting and solidifying the metal powder. This laser irradiation is performed under either high-density conditions or porous conditions according to the profile. If modeling is not complete 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 necessarily 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. 6 is a flowchart of the learning model generation process and the profile setting process. Each of these processes is executed by the profile setting device 20. However, as explained in FIG. 1, the profile setting device 20 does not have to be a single device, and may be configured by connecting multiple computers, servers, etc. via a network.

[0065] First, we will explain the learning model generation process executed by the profile setting device 20. When this process starts, the profile setting device 20 reads past modeling data from the modeling database (step S20). The modeling data can be, for example, the shape of the modeled object, its mechanical strength, the magnitude of distortion during modeling, the profile used for modeling, etc.

[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 meets requirements such as mechanical strength, the magnitude of distortion during modeling, etc. Various methods can be used as an algorithm for generating the learning model.

[0067] Next, a description will be given of the profile setting process, which is carried out to determine the 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 tolerance 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, using this learning model, a profile of the amount of energy is set (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 a learning model may be generated in advance. Also, a learning model that has been generated once may be continued to be used.

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

[0070] In this embodiment, a profile can be set by machine learning, which allows an appropriate profile to be set so as to satisfy 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. Furthermore, the present invention is not limited to the embodiments, and various modifications may be made. For example, the amount of energy is not limited to the two conditions of high density 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 three-dimensional modeling in a method of laminating thin layers formed by melting and solidifying powder. [Explanation of symbols]

[0073] 10 Three-dimensional printing equipment 11. Modeling Table 12 Moving mechanism 13 Recoater 15 Laser irradiation unit 16 Control Unit 17 Input section 20 Profile setting device 21 Modeling Database 22 Required 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: (a) defining the shape of each layer to configure the object with thin layers having a predetermined thickness; (b) applying a predetermined amount of energy to the powder to melt it and solidify it to form the thin layer conforming to the 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.

2. The three-dimensional modeling method according to claim 1, The step (d) is a three-dimensional modeling method in which, after forming the plurality of thin layers with a first amount of energy, the amount of energy is switched 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 layers formed by a first amount of energy and a second layer region consisting of the thin layers 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 the mechanical strength required for the shaped object; The step (d) is a three-dimensional modeling method in which the amount of energy is controlled in accordance with the setting result of the step (e).

6. The three-dimensional modeling method according to claim 1, further comprising: (f) determining the amount of energy to be applied to each thin layer according to a range of distortion allowable for the object; The step (d) is a three-dimensional modeling method in which the amount of energy is controlled in accordance with the setting result of the step (e).

7. 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.

8. A three-dimensional printing apparatus for printing a three-dimensional object, comprising: an input unit that reads shape data of each layer to configure the object with thin layers of a predetermined thickness; a thin layer forming unit that applies a predetermined amount of energy to the powder to melt and solidify it, thereby forming the thin layer according to the shape data; a lamination unit that moves the thin layer formation unit and the formed thin layer relatively to each other 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.

9. 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 of a predetermined thickness; (b) applying a predetermined amount of energy to the powder to melt it and solidify it to form the thin layer according to the 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; A program to execute.

10. (a) defining the shape of each layer to construct a shaped object from thin layers of a predetermined thickness; (b) applying a predetermined amount of energy to the powder to melt it and solidify it to form the thin layer conforming to the 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; A 3D object manufactured by a 3D modeling method comprising the steps of:

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