JP7806412B2 - Method for manufacturing a shaped body and shaping apparatus - Google Patents

Description

The present invention relates to a method for manufacturing a shaped object and a shaping apparatus.

Methods for manufacturing a shaped body by stacking metal-containing shaping layers have been known for some time (see, for example, Patent Documents 1 and 2). Generally, the stacked shaping layers are formed by solidifying metal powder that is melted by supplying it to the focal point of a laser beam.

Japanese Patent Application Laid-Open No. 2003-1439 Japanese Patent Application Publication No. 3-146603

However, when forming a model by stacking different types of modeling layers, there is a risk of cracks occurring due to differences in the thermal expansion coefficients of the modeling layers. When cracks occur, the strength of the model decreases. This problem has been difficult to solve even with the above-mentioned prior art.

The present invention has been made to solve the above-mentioned problems, and aims to provide a technology for suppressing a decrease in the strength of a shaped body in a manufacturing method for the shaped body.

The present invention has been made to solve at least some of the above-mentioned problems, and can be realized in the following forms.

(1) According to one aspect of the present invention, there is provided a method for manufacturing a shaped body, in which a shaped body is manufactured by stacking shaped layers containing a metal. This method for manufacturing a shaped body includes a first step of forming a first shaped layer on a substrate by melting and solidifying a first metal powder, a second step of heating the first shaped layer, and a third step of forming a second shaped layer having a smaller thermal expansion coefficient than the first shaped layer, in which the second shaped layer is formed on the heated first shaped layer by melting and solidifying a second metal powder.

According to this configuration, in the method for manufacturing a shaped body, after the first step of forming a first shaping layer on a substrate, the first shaping layer is heated in the second step, and in the third step, a second shaping layer with a low thermal expansion coefficient is formed on the heated first shaping layer to manufacture the shaped body. This reduces the difference in thermal contraction between the first and second shaping layers when the temperature of the shaped body decreases after the second shaping layer is formed, thereby reducing the number of cracks that occur in the first shaping layer due to shrinkage distortion of the second shaping layer. This therefore makes it possible to suppress a decrease in the strength of the shaped body due to cracks.

(2) In the method for manufacturing a molded body of the above aspect, in the first step, the first metal powder may be irradiated with laser light to melt the first metal powder, and in the third step, the second metal powder may be irradiated with laser light having a lower intensity than the laser light irradiated with the first metal powder in the first step to melt the second metal powder. According to this configuration, in the third step, the intensity of the laser light irradiated with the second metal powder is set lower than the intensity of the laser light irradiated with the first metal powder in the first step. This makes it difficult for the temperature of the second molded layer to rise, thereby reducing the difference in temperature between the first molded layer and the second molded layer when the second molded layer is being formed. Therefore, the difference in thermal contraction between the first molded layer and the second molded layer when the temperature of the molded body decreases is reduced, thereby suppressing a decrease in the strength of the molded body due to cracks.

(3) In the method for manufacturing a shaped body of the above aspect, the first step may include a first layer forming step of forming a first layer of the first shaping layer on the base material, and a second layer forming step of forming a second layer of the first shaping layer on the first layer, the second layer having a thermal expansion coefficient greater than that of the second shaping layer but smaller than that of the first layer, and the third step may include forming the second shaping layer on the second layer. According to this configuration, the first layer forming step of the first step forms the first layer on the base material, and the second layer laminating step of the first step forms a second layer on the first layer, the second layer having a thermal expansion coefficient greater than that of the second shaping layer but smaller than that of the first layer. Thereafter, the third step forms the second shaping layer on the second layer. This further reduces the difference in thermal contraction between the second modeling layer and the first modeling layer, further reducing the number of cracks that occur in the first modeling layer due to shrinkage distortion of the second modeling layer when the temperature of the modeled object drops. This further reduces the reduction in strength of the modeled object.

(4) In the method for manufacturing a molded body of the above aspect, the second layer formation step may form the second layer by melting and solidifying a mixed powder of the first metal powder and the second metal powder. According to this configuration, when forming the second layer, the mixed powder of the first metal powder and the second metal powder is melted and solidified. This makes it possible to easily form a second layer having a thermal expansion coefficient greater than that of the second molded layer but smaller than that of the first layer. Therefore, the difference in thermal contraction between the second molded layer side of the first molded layer and the second molded layer can be easily reduced, making it possible to easily prevent a decrease in the strength of the molded body due to cracks.

(5) In the method for manufacturing a molded body of the above aspect, the second layer formation step may form the second layer by melting and solidifying the mixed powder, in which the content of the first metal powder decreases as the thickness of the second layer increases. According to this configuration, when forming the second layer, the mixed powder is melted and solidified, in which the content of the first metal powder decreases as the thickness of the second layer increases. This allows the characteristics of the first molded layer to gradually approach the characteristics of the second molded layer from the substrate side to the second molded layer side. Therefore, it is easier to alleviate shrinkage distortion of the second molded layer when the temperature of the molded body decreases, making cracks less likely to occur and further suppressing a decrease in the strength of the molded body.

(6) Another aspect of the present invention provides a modeling device that produces a shaped object by stacking metal-containing modeling layers. This modeling device includes a powder supply unit that supplies multiple types of metal powder onto a substrate, a powder heating unit that heats and melts the metal powder on the substrate, and a modeling layer heating unit that heats the modeling layer formed by solidifying the molten metal powder. According to this configuration, the modeling device can heat the modeling layer formed by solidifying the molten metal powder using the modeling layer heating unit. Thus, when producing a shaped object, by melting and solidifying the metal powder on the heated modeling layer to form the modeling layer, it is possible to reduce the difference in thermal contraction caused by differences in the thermal expansion coefficients between adjacent modeling layers. Therefore, it is possible to reduce the number of cracks that occur in the first modeling layer due to shrinkage distortion of the second modeling layer, thereby suppressing a decrease in the strength of the shaped object.

The present invention can be realized in various forms, such as a shaped body manufactured by a shaped body manufacturing method, a system including a shaping device, a control method for these devices and systems, a computer program for causing these devices and systems to execute a shaped body manufacturing method, a server device for distributing the computer program, and a non-transitory storage medium on which the computer program is stored.

FIG. 1 is a schematic diagram illustrating a schematic configuration of a molding apparatus according to a first embodiment. 3A to 3C are diagrams illustrating a method for manufacturing a molded object using the molding apparatus of the first embodiment. 10 is a cross-sectional photograph of a shaped body of a comparative example. 1 is a cross-sectional photograph of a shaped body according to a first example. 10 is a cross-sectional photograph of a shaped body according to a second example. FIG. 10 is a diagram illustrating the change over time in the surface temperature of a shaped body. 10A and 10B are diagrams illustrating differences in thermal shrinkage of shaped bodies. FIG. 10 is a first diagram illustrating a method for manufacturing a shaped body according to a comparative example. FIG. 10 is a second diagram illustrating the method for manufacturing a shaped body of the comparative example. 10A to 10C are diagrams illustrating a method for manufacturing a molded object using a molding apparatus according to a second embodiment.

First Embodiment
FIG. 1 is a schematic diagram showing the overall configuration of a modeling apparatus 1 of the first embodiment. FIG. 2 is a diagram illustrating a method for manufacturing a modeled body 5 using the modeling apparatus 1 of the first embodiment. The modeling apparatus 1 includes a laser emission unit 10, a base plate 20, a raw material supply unit 31, a nozzle unit 40, and a control unit 50. As shown in FIG. 1 , the modeled body 5 formed by the modeling apparatus 1 of the present embodiment includes a substrate 6, a first modeling layer 7, and a second modeling layer 8. For ease of explanation, in FIGS. 1 and 2 , the vertical direction in the modeling apparatus 1 of the present embodiment is defined as the z-axis direction. Furthermore, the direction perpendicular to the z-axis is defined as the x-axis direction, and the direction perpendicular to the z-axis and x-axis is defined as the y-axis direction.

The laser emission unit 10 has a laser light source (not shown). The laser emission unit 10 is electrically connected to the control unit 50 and emits laser light Lz using the laser light source in response to commands output by the control unit 50. The laser light Lz emitted by the laser emission unit 10 is irradiated onto the base plate 20 via the nozzle unit 40. In this embodiment, the laser light Lz is irradiated from the nozzle unit 40 in the negative direction of the z-axis. The laser emission unit 10 corresponds to the "powder heating unit" in the claims.

The base plate 20 is a flat member that is positioned in the direction in which the laser light Lz is emitted, specifically below the nozzle portion 40 (in the negative direction of the z-axis). In this embodiment, the base plate 20 is made of pre-hardened steel. The base plate 20 contains a heater 21 that generates heat when electricity is applied. The heater 21 is electrically connected to the control unit 50 and generates heat in response to commands from the control unit 50.

The raw material supply unit 31 supplies multiple types of metal powder M to the nozzle unit 40. The raw material supply unit 31 is electrically connected to the control unit 50, and adjusts the type, amount, and supply timing of the metal powder M supplied to the nozzle unit 40 in accordance with commands output by the control unit 50. In this embodiment, the raw material supply unit 31 is connected to a metal powder storage unit (not shown). The raw material supply unit 31 supplies the metal powder M to the nozzle unit 40 together with a carrier gas, such as argon gas, supplied by a gas supply unit (not shown). The raw material supply unit 31 corresponds to the "powder supply unit" in the claims.

The nozzle unit 40 includes a nozzle 41 and a drive unit 42. The nozzle 41 is disposed between the base plate 20 and the laser emission unit 10. As shown in FIG. 2 , the nozzle 41 has a double-tube structure and includes an inner tube unit 43 and an outer tube unit 44. The inner tube unit 43 is a tubular member formed so that its outer diameter decreases in the negative direction of the z-axis. The inner tube unit 43 is formed to allow the laser light Lz emitted from the laser emission unit 10 to pass through. In this embodiment, a shielding gas G1 is supplied around the laser light Lz passing through the inside of the inner tube unit 43 so as to surround the laser light Lz. The outer tube unit 44 is a tubular member disposed outside the inner tube unit 43. The outer tube unit 44 is formed so that its outer diameter decreases in the negative direction of the z-axis. A passage 45 is formed between the inner tube unit 43 and the outer tube unit 44, through which the metal powder M supplied by the raw material supply unit 31 passes. The metal powder M passing through the passage 45 is supplied onto the base plate 20 together with the above-mentioned carrier gas (see symbol G2 in Figure 2).

The drive unit 42 is connected to the nozzle 41. The drive unit 42 is electrically connected to the control unit 50, and generates a drive force to drive the nozzle 41 in response to commands from the control unit 50. In this embodiment, the nozzle 41 is movable in any of the z-axis, x-axis, and y-axis directions relative to the base plate 20. This allows the shaped body 5 to be formed at any location on the surface 20a of the base plate 20.

The control unit 50 is a computer including ROM, RAM, and a CPU. The control unit 50 is electrically connected to the laser emission unit 10, the raw material supply unit 31, and the drive unit 42, and controls their operation according to a computer program that has been input in advance. Specifically, the control unit 50 controls the emission timing and intensity of the laser light Lz emitted from the laser emission unit 10. The control unit 50 controls the heat generation timing and heat amount of the heater 21 on the base plate 20. The control unit 50 controls the type, supply amount, and supply timing of the metal powder supplied by the raw material supply unit 31. The control unit 50 controls the movement of the nozzle 41 by the drive unit 42.

Next, a method for manufacturing the shaped body 5 of this embodiment will be described. The method for manufacturing the shaped body 5 of this embodiment is, for example, a manufacturing method using a directed energy deposition method (deposition method). In the directed energy deposition method, metal powder M is supplied to the focal point of the laser light Lz irradiated on the base plate 20 using a carrier gas G2. The metal powder M melted by the laser light Lz is deposited on the substrate 6 to form a shaped body 5 of any shape. The substrate 6 may be a component manufactured using a method different from the method for manufacturing the shaped body 5, or it may be a pre-formed body formed from metal powder using the directed energy deposition method described above. In this embodiment, the substrate 6 is made of maraging steel. Note that the method for manufacturing the shaped body 5 is not limited to the directed energy deposition method, and any method may be used as long as it is capable of forming a shaped body 5 of any shape by first melting and solidifying the metal that forms the first and second modeling layers 7 and 8.

First, a first modeling layer 7 is formed on the surface 60 of the substrate 6 placed on the base plate 20 (first step). The control unit 50 controls the laser emission unit 10 to emit laser light Lz toward the surface 60 of the substrate 6, while the raw material supply unit 31 supplies a first metal powder, which is the material for the first modeling layer 7, to the portion of the surface 60 of the substrate 6 that is irradiated with the laser light Lz. In this embodiment, high-speed tool steel with a thermal expansion coefficient of 11.9 × 10 ^-6 (1/°C) is used as the first metal. The high-speed tool steel powder is melted by the energy of the laser light Lz and then solidifies on the surface 60 of the substrate 6. This forms the first modeling layer 7 on the surface 60 of the substrate 6.

Next, while the first modeling layer 7 is heated (second step), the second modeling layer 8 is formed on the surface 70 of the first modeling layer 7 (third step). The control unit 50 supplies power to the heater 21 to generate heat. The heat generated by the heater 21 is transferred to the first modeling layer 7 via the base plate 20 and substrate 6 (see dotted arrow H1 in the figure), causing the temperature of the first modeling layer 7 to rise. In this embodiment, the control unit 50 supplies power to the heater 21 so that the temperature of the first modeling layer 7 reaches 200°C.

With the first modeling layer 7 at 200°C, the control unit 50 controls the raw material supply unit 31 to supply the laser beam Lz with a second metal powder, which is the material for the second modeling layer 8. In this embodiment, maraging steel with a thermal expansion coefficient of 10.1 × 10 ^-6 (1/°C), is used as the second metal. In this embodiment, when forming the second modeling layer 8, the control unit 50 controls the laser emission unit 10 to irradiate the surface 70 of the first modeling layer 7 with laser beam Lz having an intensity lower than that of the laser beam Lz used when forming the first modeling layer 7. The control unit 50 controls the raw material supply unit 31 to supply maraging steel powder to the portion of the surface 70 of the first modeling layer 7 that is irradiated with the laser beam Lz. The maraging steel powder is melted by the energy of the laser beam Lz, forming a melt pool 80 of maraging steel on the surface 70 of the first modeling layer 7. As this maraging steel melt pool 80 solidifies, a second modeling layer 8 is formed on the surface 70 of the first modeling layer 7, and a modeled body 5 is produced.

Next, the effects of the manufacturing method for the molded body 5 of this embodiment will be described. First, the state of the molded bodies manufactured using three manufacturing methods for molded bodies with different conditions will be evaluated. Specifically, for molded bodies formed by stacking a substrate, a first modeling layer, and a second modeling layer on a base plate, the cross sections of the molded bodies will be compared when the temperature conditions of the first modeling layer when forming the second modeling layer are changed. In each of the three manufacturing methods for molded bodies, a directional energy deposition method was used to supply a laser beam with an output of 750 W with metal powder at a supply rate of 0.08 g/s (carrier gas flow rate of 25 L/min), forming a rectangular parallelepiped molded body.

Figure 3 is a cross-sectional photograph of a comparative example of a molded body A5. Figure 3 shows a molded body A5 formed on a base plate BP20. The molded body A5 comprises a substrate A6, a first molded layer A7, and a second molded layer A8. In the comparative example manufacturing method for producing the molded body A5, the temperature of the first molded layer A7 is not adjusted when the second molded layer A8 is formed. As shown in Figure 3, two cracks Cr1 can be seen in the first molded layer A7 of the molded body A5.

Figure 4 is a cross-sectional photograph of the formed body B5 of the first example. Figure 4 shows the formed body B5 formed on the base plate BP20. The formed body B5 comprises a substrate B6, a first forming layer B7, and a second forming layer B8. In the manufacturing method of the first example for producing the formed body B5, the first forming layer B7 is maintained at 100°C when forming the second forming layer B8. As shown in Figure 4, cracks Cr2 are formed in the first forming layer B7 of the formed body B5, but it was confirmed that the number and size of the cracks are smaller than those of the formed body A5 of the comparative example.

Figure 5 is a cross-sectional photograph of the formed body C5 of the second embodiment. Figure 5 shows the formed body C5 formed on the base plate BP20. The formed body C5 comprises a substrate C6, a first forming layer C7, and a second forming layer C8. In the manufacturing method of the second embodiment for producing the formed body C5, the first forming layer C7 is maintained at 200°C when forming the second forming layer C8. As shown in Figure 5, no cracks, such as those observed in the cross-sectional photographs of Figures 3 and 4, were observed in the first forming layer C7.

Next, we will explain the difference in thermal shrinkage between the first and second modeling layers in each of the modeling bodies shown in Figures 3 to 5. The difference in thermal shrinkage between the first and second modeling layers is calculated from the amount of thermal shrinkage of each of the first and second modeling layers, using the temperature at the end of formation of the second modeling layer and the temperature a certain time after formation of the second modeling layer is completed. The amount of thermal shrinkage of the modeling layer is calculated using the following formula (1):
ΔL=α×(T1-T2)×L...(1)
ΔL: Heat shrinkage amount (μm)
α: Coefficient of thermal expansion (×10 ^-6 /°C)
T1: Temperature (°C) when formation of the second modeling layer is completed
T2: Temperature (°C) at a certain time after the formation of the second modeling layer is completed
L: length of one side of the rectangular parallelepiped shaped object (mm)

FIG. 6 is a diagram illustrating the change in the surface temperature of the molded body over time. FIG. 6 shows the change in the surface temperature of the second molded layer over time, from the end of the formation of the second molded layer (time 0 minutes in FIG. 6 ) to 13 minutes. To calculate the difference in thermal contraction between the first and second molded layers, the temperature T1 of the second molded layer at the end of the formation of the second molded layer is first calculated. Using the data on the change in temperature over time shown in FIG. 6 , the temperature T1 at the end of the formation of the second molded layer is extrapolated to obtain the following temperature:
Comparative example (without temperature adjustment): 217°C
First Example (Temperature 100°C): 152°C
Second Example (Temperature 200°C): 127°C

The temperature T2 of the second modeling layer after a certain time has elapsed since the formation of the second modeling layer was completed was the temperature 3 minutes after the formation of the second modeling layer was completed, as shown in Figure 6. The temperature T2 of the first modeling layer was the following temperature 3 minutes after the formation of the second modeling layer was completed.
Comparative example: 41°C
First Example: 102°C
Second Example: 201°C

Figure 7 illustrates the difference in thermal shrinkage between the formed bodies. Figure 7 shows the thermal shrinkage difference calculated for the formed body A5 of the comparative example, the formed body B5 of the first example, and the formed body C5 of the second example using the data on the temperature change over time shown in Figure 6. As shown in Figure 7, the formed body A5 of the comparative example, in which two relatively large cracks Cr1 were observed, had a thermal shrinkage difference of 1.55 μm. On the other hand, the formed body A5 of the first example, in which the number and size of cracks were smaller than those of the formed body A5 of the comparative example, had a thermal shrinkage difference of 0.90 μm, which is smaller than the thermal shrinkage difference of the formed body A5 of the comparative example. Furthermore, the formed body C5 of the second example, in which no cracks were observed, had a thermal shrinkage difference of 0.29 μm. In other words, the evaluation results for the first and second examples reveal that heating the first forming layer when forming the second forming layer can reduce the number and size of cracks. In particular, under the conditions of this embodiment (rectangular shaped object, first modeling layer: high-speed tool steel, second modeling layer: maraging steel), it was confirmed that the occurrence of cracks in the first modeling layer can be suppressed by heating the first modeling layer to 200°C so that the difference in thermal contraction between the first and second modeling layers is 0.3 μm or less (Second Example).

Figure 8 is the first diagram illustrating the manufacturing method for the comparative example molded body A5. As described above, in the comparative example molded body A5, when the second molded layer A8 is formed, the temperature of the first molded layer A7 is not adjusted, and therefore is relatively low. Therefore, the second molded layer A8, which has been heated to a high temperature by the energy of the laser light, is formed on top of the relatively low-temperature first molded layer A7.

Figure 9 is the second diagram illustrating the manufacturing method for the comparative example molded body A5, showing the molded body A5 after the second molded layer A8 has been formed. After the second molded layer A8 is formed and the molded body A5 is completed, the temperature of the entire molded body A5 drops, and the second molded layer A8, which is at a high temperature, shrinks relatively significantly due to the temperature change (see the open arrow F1 in Figure 9). On the other hand, the first molded layer A7 adjacent to the second molded layer A8 was at a relatively low temperature, and therefore shrinks relatively little due to the temperature change. As a result, stress is generated due to shrinkage distortion in the second molded layer A8, and numerous cracks Cr1 occur in the first molded layer A7. When cracks Cr1 occur, the strength of the molded body A5 decreases, potentially resulting in damage.

According to the method for manufacturing the molded body 5 of this embodiment described above, after the first step of forming the first molded layer 7 on the substrate 6, the first molded layer 7 is heated in the second step, and in the third step, the second molded layer 8, which has a small thermal expansion coefficient, is formed on the heated first molded layer 7 to manufacture the molded body 5. As a result, when the temperature of the molded body 5 decreases after the second molded layer 8 is formed, the difference in thermal contraction between the first molded layer 7 and the second molded layer 8 becomes smaller, thereby reducing the number of cracks that occur in the first molded layer 7 due to shrinkage distortion of the second molded layer 8. Therefore, a decrease in the strength of the molded body 5 due to cracks can be suppressed.

Furthermore, according to the manufacturing method of the shaped body 5 of this embodiment, in the third step, the intensity of the laser light Lz irradiated onto the maraging steel powder is set lower than the intensity of the laser light Lz irradiated onto the high-speed tool steel powder in the first step. This makes it difficult for the second shaping layer 8 to become too hot, and therefore the difference in temperature between the first shaping layer 7 and the second shaping layer 8 when the second shaping layer 8 is being formed can be reduced. Therefore, the difference in thermal contraction between the first shaping layer 7 and the second shaping layer 8 when the temperature of the shaped body 5 drops is reduced, and therefore a decrease in the strength of the shaped body 5 due to cracks can be suppressed.

Furthermore, with the modeling device 1 of this embodiment, the heater 21 can heat the first modeling layer 7, which is formed by solidifying molten high-speed tool steel powder. As a result, when manufacturing the modeled body 5, the second modeling layer 8 is formed by melting and solidifying maraging steel powder on the heated first modeling layer 7, thereby reducing the difference in thermal contraction caused by differences in the thermal expansion coefficients between the first modeling layer 7 and the second modeling layer 8. Therefore, the number of cracks that occur in the first modeling layer 7 due to shrinkage distortion of the second modeling layer 8 can be reduced, thereby suppressing a decrease in the strength of the modeled body 5.

Second Embodiment
10 is a diagram illustrating a method for manufacturing a molded body using the molding apparatus of the second embodiment. The method for manufacturing a molded body of the second embodiment differs from the method for manufacturing a molded body of the first embodiment ( FIG. 2 ) in that the characteristics of the first molded body are changed depending on the thickness of the first molded layer.

The modeling device 2 of this embodiment includes a laser emission unit 10, a base plate 20, a raw material supply unit 32, a nozzle unit 40, and a control unit 50.

The raw material supply unit 32 supplies multiple types of metal powder M to the nozzle unit 40. The raw material supply unit 32 is electrically connected to the control unit 50, and adjusts the type, amount, and supply timing of the metal powder M supplied to the nozzle unit 40 in response to commands output by the control unit 50. In this embodiment, the raw material supply unit 32 is capable of supplying a mixed powder of high-speed tool steel powder and maraging steel powder to the nozzle unit 40 in response to commands from the control unit 50. The raw material supply unit 32 corresponds to the "powder supply unit" in the claims.

Next, a method for manufacturing the molded body 5 of this embodiment will be described. In the method for manufacturing the molded body 5 of this embodiment, in the first step of forming the first molded layer 7, first, a first layer 71 of the first molded layer 7 on the substrate 6 side is formed (first layer formation step). The control unit 50 controls the laser emission unit 10 to irradiate the surface 60 of the substrate 6 placed on the surface 20a of the base plate 20 with laser light Lz, while controlling the raw material supply unit 31 to supply high-speed tool steel powder. This forms a first layer 71 made of high-speed tool steel on the surface 60 of the substrate 6.

Next, the second layer 72 of the first modeling layer 7, which will be on the second modeling layer 8 side, is formed (second layer formation process). The control unit 50 controls the laser emission unit 10 to irradiate the surface of the first layer 71 with laser light Lz, while controlling the raw material supply unit 31 to supply a mixed powder of high-speed tool steel powder and maraging steel powder. In this embodiment, when forming the second layer 72, a mixed powder with a higher proportion of high-speed tool steel powder than maraging steel powder is initially supplied to form a portion of the second layer 72. Thereafter, as the thickness of the second layer 72 increases, a mixed powder with a smaller proportion of high-speed tool steel powder and a larger proportion of maraging steel powder is supplied. As a result, a portion of the second layer 72 with characteristics similar to those of the first layer 71 is formed on the first layer 71 side, and a portion of the second layer 72 with characteristics similar to those of the second modeling layer 8 is formed on the second layer 72 side.

Next, as in the first embodiment, the first modeling layer 7 is heated by the heater 21 while the second modeling layer 8 is formed on the surface of the second layer 72. This forms the second modeling layer 8 on the surface 70 of the first modeling layer 7, producing the modeled body 5.

According to the manufacturing method of the molded body 5 of this embodiment described above, in the first step, the first layer formation step, a first layer 71 is formed on the substrate 6. In the first step, the second layer formation step, a second layer 72 is formed on the first layer 71. The second layer 72 has a thermal expansion coefficient greater than that of the second molded layer 8 but less than that of the first layer 71. Then, in the third step, the second molded layer 8 is formed on the second layer 72. This further reduces the difference in thermal contraction between the second molded layer side of the first molded layer 7 and the second molded layer 8, thereby further reducing the number of cracks that occur in the first molded layer 7 due to shrinkage distortion of the second molded layer 8 when the temperature of the molded body 5 drops. This further reduces the reduction in strength of the molded body 5 due to cracks.

Furthermore, according to the manufacturing method of the molded body 5 of this embodiment, when forming the second layer 72, a mixed powder of high-speed tool steel powder and maraging steel powder is melted and solidified. This makes it easy to form the second layer 72 with a thermal expansion coefficient greater than that of the second molding layer 8 but smaller than that of the first layer 71. Therefore, the difference in thermal contraction between the second molding layer side of the first molding layer 7 and the second molding layer 8 can be easily reduced, making it easy to prevent a decrease in the strength of the molded body 5 due to cracks.

Furthermore, according to the manufacturing method of the molded body 5 of this embodiment, when forming the second layer 72, a mixed powder is melted and solidified in which the content of high-speed tool steel powder decreases as the thickness of the second layer 72 increases. This allows the characteristics of the first molded layer 7 to gradually approach the characteristics of the second molded layer 8 from the substrate 6 side to the second molded layer 8 side. Therefore, stress caused by shrinkage distortion in the second molded layer 8 when the temperature of the molded body 5 decreases is more easily alleviated, making cracks less likely to occur and further suppressing a decrease in the strength of the molded body 5.

<Modification of this embodiment>
The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[Modification 1]
In the first embodiment, when forming the second modeling layer 8, the heater 21 serving as the "modeling layer heating unit" heats the first modeling layer 7 together with the substrate 6, but it is also possible to heat only the first modeling layer 7. In this case, for example, the first modeling layer 7 may be heated using a heat gun capable of heating only the first modeling layer 7, and the heating method is not limited to these.

[Modification 2]
In the above embodiment, the first modeling layer 7 is heated in the "second step" while the second modeling layer 8 is formed in the "third step," but the timing of heating the first modeling layer 7 is not limited to this. When the second modeling layer 8 is formed, it is sufficient that the temperature of the first modeling layer 7 has risen. For example, the first modeling layer 7 may be heated in the "second step" before the second modeling layer 8 is formed in the "third step."

[Modification 3]
In the above-described embodiment, the high-speed tool steel powder forming the first molding layer 7 and the maraging steel powder forming the second molding layer 8 are each heated by the laser light Lz. The method of heating the metal powder is not limited to this. The intensity of the laser light Lz may be the same in the first and third steps, or may be greater in the third step than in the first step.

[Modification 4]
In the second embodiment, a mixed powder of high-speed tool steel powder and maraging steel powder is supplied when forming the second layer 72. When forming the second layer 72, a powder of a metal having a thermal expansion coefficient larger than that of the second modeling layer 8 but smaller than that of the first layer 71 may be supplied.

[Modification 5]
In the second embodiment, the second layer 72 is formed by melting and solidifying a mixed powder in which the content of high-speed tool steel powder decreases as the thickness of the second layer 72 increases. For example, the second layer 72 may be formed by melting and solidifying a mixed powder in which the content of high-speed tool steel powder and the content of maraging steel powder each are 50%.

[Modification 6]
In the above-described embodiment, the base material 6 is made of maraging steel, which is an iron-based material. The base material 6 may be made of another iron-based material, or may be made of a material different from the iron-based material.

[Modification 7]
In the above-described embodiment, the shaped body 5 includes a substrate 6, a first shaped layer 7, and a second shaped layer 8. The configuration of the shaped body 5 is not limited to this. The substrate 6 may be omitted, and the first shaped layer 7 and the second shaped layer 8 may be stacked on a base plate 20. The number of shaped layers included in the shaped body 5 is not limited to two, and may be three or more. In this case, it is sufficient that the shaped layer on which the molten metal powder is placed is heated to a high temperature. Furthermore, although the substrate 6 may be a member manufactured by a method different from the manufacturing method of the shaped body 5, or a pre-shaped body formed from metal powder by directed energy deposition, the substrate 6 may be configured by stacking multiple layers.

[Modification 8]
In the above-described embodiment, the manufacturing method of the shaped body is a manufacturing method using directed energy deposition, but the manufacturing method of the shaped body is not limited to this. Any method may be used as long as the shaped body is manufactured by forming a second shaped layer on the surface of a base material and then stacking a first shaped layer on the second shaped layer.

[Modification 9]
In the above-described embodiment, in the third step, the intensity of the laser light Lz irradiated onto the maraging steel powder is set to be smaller than the intensity of the laser light Lz irradiated onto the high-speed tool steel powder in the first step. Furthermore, when forming the second molding layer 8, even if the supply amount of the maraging steel powder is reduced and the molding speed of the second molding layer 8 is suppressed, the occurrence of cracks can be suppressed.

[Modification 10]
As described in Figures 3 to 7 of the first embodiment, we confirmed that setting the temperature of the first modeling layer C7 to 200°C when forming the second modeling layer C8 (Second Example) can suppress the occurrence of cracks in the first modeling layer C7. On the other hand, as in the first Example where the temperature of the first modeling layer B7 when forming the second modeling layer B8 was set to 100°C, by heating the first modeling layer to a certain degree when forming the second modeling layer, the thermal contraction difference is smaller than that of the comparative modeling body (see Figure 7). This allows the number and size of cracks to be smaller than that of the comparative modeling body A5. In other words, by heating the first modeling layer when forming the second modeling layer, the thermal contraction difference between the first and second modeling layers is reduced, thereby reducing the number and size of cracks and suppressing a decrease in the strength of the modeling body.

This aspect has been described above based on embodiments and variations, but the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from its spirit or the scope of the claims, and equivalents are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

REFERENCE SIGNS LIST 1, 2... Modeling device 5... Modeled body 6... Base material 7... First modeling layer 8... Second modeling layer 10... Laser emission unit 21... Heater 31, 32... Raw material supply unit 71... First layer 72... Second layer Lz... Laser light M... Metal powder

Claims (6)

A method for manufacturing a shaped body by stacking shaping layers containing a metal,
a first step of melting and solidifying a first metal powder, which is a raw material for a first modeling layer made of high-speed tool steel , to form the first modeling layer on a base material;
a second step of heating the first modeling layer;
a third step of forming a second modeling layer made of maraging steel having a smaller thermal expansion coefficient than high-speed tool steel , wherein the second modeling layer is formed on the heated first modeling layer by melting and solidifying a second metal powder that is a raw material for the second modeling layer;
A method for manufacturing a shaped object. The method for manufacturing a shaped body according to claim 1,
In the first step, the first metal powder is melted by irradiating the first metal powder with a laser beam;
In the third step, the second metal powder is melted by irradiating the second metal powder with a laser beam having an intensity lower than that of the laser beam irradiated to the first metal powder in the first step.
A method for manufacturing a shaped object. The method for manufacturing a shaped body according to claim 1 or 2, comprising:
The first step comprises:
a first layer forming step of forming a first layer of the first modeling layer on the base material;
a second layer forming step of forming a second layer of the first modeling layer on the first layer, the second layer having a thermal expansion coefficient greater than that of the second modeling layer and smaller than that of the first layer;
In the third step, the second modeling layer is formed on the second layer.
A method for manufacturing a shaped object. The method for manufacturing a shaped body according to claim 3,
In the second layer forming step, the second layer is formed by melting and solidifying a mixed powder of the first metal powder and the second metal powder.
A method for manufacturing a shaped object. The method for manufacturing a shaped body according to claim 4,
In the second layer forming step, the second layer is formed by melting and solidifying the mixed powder, in which the content of the first metal powder decreases as the thickness of the second layer increases.
A method for manufacturing a shaped object. A molding apparatus for manufacturing a molded object by stacking metal-containing molding layers,
a powder supply unit that supplies, onto the substrate, a first metal powder that is a raw material for the first molding layer made of high-speed tool steel, and a second metal powder that is a raw material for the second molding layer made of maraging steel that has a smaller thermal expansion coefficient than high-speed tool steel;
a powder heating unit that heats and melts metal powder supplied onto the base material to form a modeling layer;
a modeling layer heating unit that heats the first modeling layer formed by melting and solidifying the first metal powder,
The powder supply unit supplies the first metal powder onto the base material, and then supplies the second metal powder onto the first modeling layer , thereby forming the second modeling layer in which the second metal powder is melted and solidified;
the modeling layer heating unit heats the first modeling layer when the second metal powder is supplied onto the first modeling layer by the powder supply unit;
Modeling equipment.