JP6648928B2 - 3D modeling equipment - Google Patents

Description

  The present invention relates to a three-dimensional modeling apparatus for heating and laminating a thin layer of raw material powder formed in a container with a laser beam transmitted through a transmission member.

  A thin-layer forming step of forming a thin layer of the raw material powder, and a heating step of heating and laminating the thin layer of the raw material powder with a laser beam, and a three-dimensional forming apparatus for forming a three-dimensional structure, so-called 3D printers have been developed. In the three-dimensional modeling apparatus, when it is preferable to perform the heating step in a depressurized container, a thin layer of the raw material powder is formed in the depressurized container, and the inside of the container is irradiated with a laser beam transmitted through a transmission member provided in the container. It is conceivable to heat the thin layer.

  Patent Literature 1 discloses a vapor deposition apparatus that heats and evaporates a metal lump placed in a depressurized container by a laser beam transmitted through a transmission member provided in the container. Patent Literature 2 discloses a laser processing machine that performs welding or fusing of a metal plate using a laser beam transmitted through a lens.

JP-A-63-176462 JP-A-2-121788

  In a three-dimensional modeling device that heats a thin layer in a container with a laser beam transmitted through a transmitting member, the substance evaporated from the heated thin layer adheres to the inner surface of the transmitting member and reduces the transmission amount of the laser beam. found.

  Therefore, referring to Patent Document 1, a sensor for detecting the laser power is provided in the container, and the detection result is fed back to the laser beam output to increase the laser beam output so as to keep the heating state of the thin layer constant. Control was considered. However, since the substance evaporated from the heated thin layer adheres to the sensor in the container and the sensitivity of the sensor decreases, the heating state of the thin layer by the laser beam becomes closer to the end of the forming process of the three-dimensional printing apparatus. Become excessive.

  Further, with reference to Patent Literature 2, control for continuously increasing the laser beam output in accordance with a predetermined function throughout the forming process of a three-dimensional structure has been considered. However, unlike a simple laser processing device, if the shape of the three-dimensional structure and the heating conditions of the thin layer are different, the change in the transmittance of the transmission member during the formation of the three-dimensional structure is different in the three-dimensional structure. to differ greatly. For this reason, the heating state of the thin layer by the laser beam tends to become inappropriate as the end of the forming process of the three-dimensional structure is approached.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a three-dimensional modeling apparatus in which a heating state of a thin layer by a laser beam is easily maintained appropriately until the end of a modeling process of a three-dimensional model.

The three-dimensional modeling apparatus according to the present invention includes a thin layer forming unit that forms a thin layer of the raw material powder, a container that houses the thin layer forming unit, a transmission member provided in the container, and a transmission member that transmits the thin layer. Heating means for forming a three-dimensional structure by heating and laminating a predetermined region of the thin layer with the laser beam, and compensating for a decrease in transmittance of the transmission member due to heating of the predetermined region by the heating unit. A control unit that executes a process of increasing the laser beam output of the heating means in accordance with the formation of the three-dimensional structure , wherein the control unit is generated based on design data of the three-dimensional structure. and a shall perform the increasing process on the basis of increasing schedule of the laser beam output of the heating means.

  According to the present invention, the control unit increases the laser beam output of the heating unit with the formation of the three-dimensional object so as to compensate for the decrease in the transmittance of the transmission member due to the heating of the solidified region by the heating unit. Execute. For this reason, the heating state of the thin layer by the laser beam is likely to be appropriately maintained until the end of the forming process of the three-dimensional structure.

FIG. 2 is an explanatory diagram of a configuration of the three-dimensional printing apparatus according to the first embodiment. It is a flowchart of a laser parameter creation control. It is a flowchart of modeling process control of a three-dimensional modeled object. It is a flowchart of a laser power reduction rate calculation control. 9 is a flowchart of laser beam output correction control. FIG. 3 is an explanatory diagram of a three-dimensional structure according to the first embodiment. 9 is a flowchart of laser parameter creation control according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<First Embodiment>
(3D modeling equipment)
FIG. 1 is an explanatory diagram of the configuration of the three-dimensional printing apparatus according to the first embodiment. As shown in FIG. 1, a three-dimensional modeling apparatus 100 heats and solidifies a solidified region 1e on a thin layer 1a of a metal raw material powder 1 by a laser beam, and laminates the solidified region 1e to form a three-dimensional structure. This is a so-called 3D printer of a powder-bed fusion-bonding type for forming the modeled object 2. Since the three-dimensional modeling apparatus 100 performs the molding by the powder bed fusion bonding method by setting a low oxygen atmosphere such as an inert gas atmosphere or a high vacuum atmosphere, the three-dimensional modeling object 2 is prevented from being oxidized, and the three-dimensional modeling object is prevented. 2 also improves the mechanical strength.

  The processing chamber 4, which is an example of a container, houses a modeling stage 5, which is an example of a thin layer forming section, and a supply mechanism 7. The processing chamber 4 has a capacity of 1500 mm in width, 1000 mm in depth, and 900 mm in height, is formed of stainless steel, and can be sealed from outside air. A vacuum gauge 16 is connected to the processing chamber 4. The vacuum gauge 16 detects the degree of vacuum (pressure) in the processing chamber 4.

The exhaust mechanism 13 as an example of the decompression unit decompresses the processing chamber 4. The exhaust mechanism 13 exhausts air in the processing chamber 4 to reduce oxygen in the processing chamber 4. The evacuation mechanism 13 is configured by connecting a dry pump and a turbo molecular pump in series, and the ultimate vacuum degree of the processing chamber 4 is 1 × 10 ⁻⁴ Pa. The exhaust mechanism 13 has an opening adjustment valve capable of adjusting an opening amount at a connection portion with the processing chamber 4.

  A gas supply mechanism 12, which is an example of a substance supply unit, supplies a substance to the processing chamber 4 decompressed by the exhaust mechanism 13 to form an atmosphere when the solidified region 1e is heated by a laser beam. The gas supply mechanism 12 can supply various reaction gases at a constant flow rate to the processing chamber 4 through the mass flow meter 12a. The gas supply unit 12b can supply nitrogen gas, hydrogen gas, hydrocarbon gas, argon gas, and the like to the mass flow meter 12a at an arbitrary mixing ratio.

  The three-dimensional printing apparatus 100 transmits a laser beam LB from the outside of the processing chamber 4 into the processing chamber 4 through the transmitting member 3 attached to the processing chamber 4, and performs tertiary irradiation in the processing chamber 4 in a low oxygen atmosphere. The original object 2 is formed. The processing chamber 4 is provided with a disk-shaped transmission member 3 having a diameter of 294 mm and a thickness of 20 mm at a position 565 mm away from the modeling table 11 in the vertical direction. The transmitting member 3 is made of a synthetic quartz plate coated with antireflection films on both sides, and has an initial transmittance of 99% or more for the laser beam of the laser oscillator 30.

(Laser oscillator)
The laser oscillator 30 and the optical system 31, which are examples of the heating unit, heat and solidify the solidified region 1e of the thin layer 1a with the laser beam transmitted through the transmission member 3 provided in the processing chamber 4. The laser beam LB generated by the laser oscillator 30 is guided to the optical system 31 by the fiber cable 32, and reaches the thin layer 1 a of the modeling stage 5 from the optical system 31 through the transmission member 3. The laser oscillator 30 is a YAG laser oscillator having a maximum output of 500 W and a wavelength of 1070 nm. The optical system 31 includes a reflection mirror, a galvanometer mirror, and an fθ lens. The optical system 31 can operate the galvanomirror to move the beam spot of the laser beam LB to an arbitrary region on the thin layer 1 a of the modeling stage 5 and scan the beam.

(Modeling stage)
The processing chamber 4 houses the modeling table 11 and covers the upper part of the modeling table 11 in a dome shape. The molding table 11 has a supply stage 6 disposed adjacent to the molding stage 5. The supply stage 6 has an elevating mechanism 6m including a servomotor 6a, a ball screw 6b, and a linear guide 6c. The supply stage 6 accumulates raw material powder to be supplied to the modeling stage 5.

  The modeling stage 5 has a lifting mechanism 5m including a servomotor 5a, a ball screw 5b, and a linear guide 5c. The modeling stage 5 is a place where a predetermined region of the raw material powder is melted and laminated by the laser beam LB to form the three-dimensional modeled object 2. The modeling stage 5 is provided with a heater unit 9 as an example of an auxiliary heating unit. The heater unit 9 supplementarily heats the thin layer 1a heated by the laser beam output of the laser oscillator 30 when the three-dimensional structure 2 is formed.

(Supply mechanism)
The supply mechanism 7 forms the thin layer 1 a of the raw material powder 1 on the modeling stage 5. The supply mechanism 7 drives the supply roller 7 a by the linear motion mechanism 7 b to move the supply roller 7 a from the supply stage 6 to the modeling stage 5 along the upper surface of the modeling table 11. Thereby, the raw material powder of the supply stage 6 moves to the modeling stage 5.

  The supply roller 7a rotates while rotating the supply roller 7a in the counter direction with respect to the drive molding table 11, and moves while scraping the raw material powder on the upper surface of the molding stage 5. Thereby, a thin layer of the raw material powder is formed on the modeling stage 5.

(Laser parameter creation control)
FIG. 2 is a flowchart of the laser parameter creation control. As shown in FIG. 2, the computer 25 different from the control unit 20 executes the laser parameter creation control to create the heating conditions of the thin layer 1a including the laser parameters (S10). The laser parameters define the laser power of each part in the solidified region 1e of the thin layer 1a. Laser parameters can be individually specified for each contour (vertical plane), interior, and surface (horizontal plane). Further, the scanning path of the laser beam LB and the heating order for each area can be freely designed.

  The control unit 20 creates a 3D model of the three-dimensional structure based on the design data (CAD data) of the target three-dimensional structure (S11). If the 3D model of the three-dimensional structure has no independence, the control unit 20 corrects the 3D model by adding a support member for imparting independence during processing (S12). The control unit 20 slices the 3D model of the three-dimensional structure using the thickness of the thin layer using the slicer software, and obtains a solidified region 1e for one layer of the thin layer 1a (S13). The control unit 20 calculates a necessary heating amount for each portion of the solidified region 1e, sets a laser parameter, creates a heating condition including the laser parameter, and stores the heating condition in the RAM 26 of the control unit 20 (S14). The laser parameters as heating conditions define the laser beam output, beam spot diameter, scanning speed, and the like along the scanning path of the laser beam.

  The heating conditions include the type of the raw material powder 1, the laser beam output, the beam spot diameter of the laser beam, the scanning speed of the laser beam, the type and pressure (degree of vacuum) of the atmosphere in the processing chamber 4, and the heater unit. 9 for auxiliary heating of the thin layer 1a. The above-mentioned laser parameters, molding materials, molding point temperatures, and the like are also included.

(Modeling process control)
FIG. 3 is a flowchart of the modeling process control of the three-dimensional modeled object. As illustrated in FIG. 3, the three-dimensional printing apparatus 100 performs the forming process control, which is an example of the three-dimensional printing method, to control the three-dimensional printing apparatus 100 to form the three-dimensional printing object 2 (S20). . The recording medium 22 stores a processing program of the three-dimensional structure 2 generated by a computer 25 different from the control unit 20. The control unit 20 reads the processing schedule of the three-dimensional structure 2 from the recording medium 22 into the RAM 26 through the reading device 21. The CPU 27 controls the molding process of the three-dimensional structure 2 by holding the control program, various data, and the processing schedule of the three-dimensional structure 2 read from the ROM 28 in the RAM 26.

In the material supply step, the user supplies the raw material powder 1 to the supply stage 6 by supplying the raw material powder to the upper part of the supply stage 6 with the supply stage 6 lowered (S21). Thereafter, the user performs a command operation to start the modeling process on the control unit 20. In the environment adjustment step, the control unit 20 adjusts the atmosphere in the processing chamber 4 by the exhaust mechanism 13 and the gas supply mechanism 12, and heats the raw material powder of the molding stage 5 to a desired temperature by the heater unit 9 (S22). . The control unit 20 exhausts the processing chamber 4 to a degree of vacuum of 1 × 10 ⁻² Pa by the exhaust mechanism 13 to reduce oxygen in the atmosphere.

  Thereafter, a reaction gas of a carbonization reaction is introduced into the processing chamber 4 through the mass flow meter 12a, and the inside of the processing chamber 4 is adjusted to a carbonization reaction gas atmosphere having a low oxygen concentration and a predetermined pressure. During the execution of the modeling process, while the gas supply mechanism 12 supplies the gaseous substance to the processing chamber 4, the inside of the processing chamber 4 is adjusted to a desired state by adjusting the opening adjustment valve of the exhaust mechanism 13 according to the output of the vacuum gauge 16. The atmosphere and the degree of vacuum are maintained.

  In the thin layer forming step, the control unit 20 controls the supply mechanism 7 to form the thin layer 1a having the thickness ΔZ of the raw material powder 1 on the modeling stage 5 (S23). The control unit 20 first lowers the molding stage 5 so that the upper surface of the raw material powder of the molding stage 5 is lower than the upper surface of the molding table 11 by ΔZ1 (ΔZ1 ≧ ΔZ). Subsequently, the supply stage 6 is raised so that the upper surface of the raw material powder of the supply stage 6 is higher than the upper surface of the modeling table 11 by ΔZ2 (ΔZ2 ≧ ΔZ).

  Then, the control unit 20 moves the supply roller 7a to the collection container 8, usually as ΔZ2 ≧ ΔZ1. At this time, the excess raw material powder worn by the supply roller 7a is collected in the collection container 8 and reused. Thereafter, the control unit 20 raises the modeling stage 5 until the thickness of the thin layer 1a of the raw material powder 1 becomes ΔZ. Subsequently, the control unit 20 moves the supply roller 7 a to the origin position of the supply stage 6 while rotating the supply roller 7 a in the wise direction with respect to the modeling table 11. By pressing and compressing the supply roller 7a against the thin layer 1a of the raw material powder 1, the density of the raw material powder of the thin layer 1a is increased.

  The control unit 20 calls up the heating condition data including the laser parameters set in advance and stored in the register, and prepares the heating lamination process (S24). As will be described later, in the condition calling step, which is the output increasing step, the control unit 20 executes a laser beam output increasing process to increase the laser beam output of the laser oscillator 30 (S24).

  The control unit 20 starts the heating and laminating step using the laser beam output from the laser oscillator 30 (S25). In the heating laminating step (S25), which is a laminating step, the control unit 20 controls the laser oscillator 30 and the optical system 31 to heat and solidify the solidified region 1e. In the heating and laminating step, the designated laser beam output is output from the laser oscillator 30 to melt or sinter the solidified region 1e of the thin layer 1a of the raw material powder on the modeling table 11.

  The control unit 20 repeats the thin-layer forming step (S23), the calling of the heating condition data (S24), and the heating laminating step (S25) until the shaping is completed (No in S26). To make a three-dimensional object. When the modeling is completed (Yes in S26), the control unit 20 executes a molded product removal process (S27). In the molded article removal process, the inside of the processing chamber 4 is returned to the atmospheric pressure after the cooling of the three-dimensional molded article, and the removal of the three-dimensional molded article is permitted.

(Decrease in transmittance of transmission member)
As shown in FIG. 1, in order to obtain a desired function / characteristic of the metal material in the three-dimensional structure 2, a sufficient amount of energy is supplied to each part of the solidified region 1e of the thin layer 1a of the raw material powder 1. There is a need. Therefore, the output of the laser beam applied to the solidified region 1e of the thin layer 1a must be strictly controlled.

  However, when the raw material powder 1 is melted and laminated, metal vapor or fine particles (hereinafter referred to as fume) in which the metal vapor aggregates are generated from the laser beam irradiation point, and the fume is transmitted to the transmission member 3. As a result, the laser beam transmittance of the transmission member 3 gradually decreases. As a result, even if the same laser beam output is output from the laser oscillator 30 at the beginning and the end of the forming process of the three-dimensional structure 2, the heating energy transmitted through the transmitting member 3 and reaching the solidified region 1e of the thin layer 1a. Will be different. In the latter half of the forming process of the three-dimensional structure 2, the transmittance of the laser beam of the transmission member 3 decreases, and it becomes impossible to supply desired heating energy to the solidified region 1e of the thin layer 1a.

  Therefore, an increase control for increasing the laser beam output of the laser oscillator 30 in proportion to the cumulative value of the output time has been proposed. However, since the amount of fume generation is greatly different only by slightly different heating conditions of the solidified region 1e of the thin layer 1a, accurate increase control can be achieved by simply increasing the laser beam output during the forming process of the three-dimensional structure 2. Can't do it. The combination of the heating conditions changes for each three-dimensional structure, and also within the same three-dimensional structure. As a result, the amount of heating may be excessive or insufficient for each part of the formed three-dimensional molded object, which may cause thermal deformation, poor melting, insufficient strength, and the like.

  Therefore, in the first embodiment, the laser beam output instruction value set in the laser parameter creation control (S10: FIG. 2) is set using the laser power reduction rate set by the laser power reduction rate calculation control (S30: FIG. 4). P is corrected for each thin layer 1a. Thereby, even when the heating condition changes for each thin layer 1a, it is possible to predict the amount of decrease in the laser beam transmittance of the transmission member 3 and appropriately increase the laser beam output.

(Laser power reduction rate calculation control)
FIG. 4 is a flowchart of the laser power reduction rate calculation control. As shown in FIG. 4, the user executes the laser power reduction rate calculation control, and obtains an increase amount of the laser beam output necessary for the control unit 20 to perform the increase processing (S24: FIG. 3) (S30). . In the laser power reduction rate calculation control, the control unit 20 determines the laser power reduction rate for each heating condition with respect to the heating region of the thin layer 1a by experiment (S30). The laser power reduction rate indicates the amount of reduction in the transmittance of the transmission member 3 per unit time of the laser beam output and per unit output.

  The control unit 20 calls the heating condition of the solidified region 1e of the thin layer 1a used in the heating lamination step (S25: FIG. 3) (S31). In the transmittance measurement before modeling, the user installs the power meter 33 on the modeling stage 5 in an atmospheric pressure atmosphere and measures the transmittance of the optical system 31 and the transmission member 3 (S32).

  In the test shaping, after performing the above-described environment adjustment step (S22: FIG. 3), test shaping is performed for a fixed time t under the heating condition i (S33). During the time t, the heating and laminating step (S25: FIG. 3) is performed without changing the laser beam output, the spot diameter, the scanning speed, the heater output, the type and pressure of the atmosphere, the molding point temperature, and the raw material powder.

  In the test molding (S33), as the thin layer forming step, the thin layer 1a of the raw material powder 1 is formed by the supply mechanism 7 in the same manner as when forming the three-dimensional molded object 2. Then, as a lamination step, the test region of the thin layer 1a is heated by the laser oscillator 30 and the optical system 31 under one combination of heating conditions, and the lamination is performed the number of times of the test.

  In the transmittance measurement after shaping (S34), after the test shaping, the user returns the processing chamber 4 to the atmospheric pressure atmosphere, installs the power meter 33 on the shaping stage 5 in the atmospheric pressure atmosphere, and controls the optical system 31 and the transmitting member 3 to each other. The transmittance is measured (S34). That is, in the transmittance measurement before modeling (S32) and the transmittance measurement after increase (S34), the transmittance of the transmission member 3 is measured at least after the lamination process of the solidified region 1e as a measurement process.

  In the calculation of the decrease rate (S35), as a generation step, an increase amount of the laser beam output is generated based on the measurement result of the transmittance.

Here, the indicated value of the laser beam output in the transmittance measurement before modeling (S32) is P _i , and the measured value is P _{i, a} . Further, the same P _i and shaped before transmission measurements an indication of the laser beam output (S32) after the transmittance measurement (S34) increasing, the measured values P _i, and _b. In this case, the reduction rate calculation step (S35), time unit, the laser power reduction rate J _i per unit laser beam output is calculated by the following equation.
J _i = (P _{i, a} −P _{i, b} ) / (P × t) (1)

(Laser beam output correction control)
FIG. 5 is a flowchart of the laser beam output correction control. As shown in FIG. 5, the control unit 20 executes laser power correction control, which is laser beam output correction control, and generates a laser beam output increase schedule by itself (S40). The control unit 20 obtains a correction coefficient K based on the result of predicting the transmittance of the transmission member 3, and corrects the laser beam output instruction value P set in the laser parameter creation control (S10) using the correction coefficient K.

To compensate for the lack of the laser beam output instruction value P to be supplied to the modeling point set in the laser parameter creation control (S10), the correction coefficient K, and the laser beam output instruction value P due to the decrease in the transmittance of the transmission member 3. The relationship with the laser beam output instruction value P 'required for the following equation is as follows.
P ′ = (1 / K) × P (2)

  The control unit 20 calls and uses the correction coefficient Kp of the last layer of the last three-dimensional structure after the formation of the thin layer as the first layer correction coefficient K1 (S41). The control unit 20 resets or corrects the correction coefficient K1 when replacing / cleaning the transmitting member 3 after the previous modeling (Yes in S42) (S47). When the exchange / cleaning of the transmission member 3 has not been performed after the previous modeling (No in S42), the control unit 20 calls up the laser parameter from the register and corrects the laser beam output instruction value P 'according to the equation (2). (S43).

  The control unit 20 predicts, as an estimation step, a state in which the transmittance of the transmission member 3 has decreased based on the heating condition of the solidified region 1e (S44). The control unit 20 predicts the amount of decrease in the laser beam output reaching the modeling point in the modeling of the i-th layer obtained by the laser power reduction rate measurement (S44).

  As a generation step, the control unit 20 generates a schedule for increasing the laser beam output based on the estimated reduction state of the transmittance of the transmission member 3 (S43 to S46). The control unit 20 calculates a correction coefficient Kp based on the prediction result of the reduction amount of the laser beam output, and overwrites the RAM 26 (register) of the control unit 20 (S45). The control unit 20 corrects the laser beam output instruction value P ′ (S43), predicts the output reduction amount (S44), and updates the correction coefficient K (from the first layer to the last layer of the thin layer (No in S46)). S45) is repeated.

The control unit 20 calculates the laser oscillation time at each laser beam output from the i-th laser parameter. Here, _assuming that the laser oscillation time of the i-th layer under the conditions _{1 to n} is t1 _{, i to} tn _{, i} and the correction coefficient of the (i + 1) th layer is Ki _{+ 1} , the correction coefficient _{Ki + 1} is expressed by the following equation. .
_{K i + 1 = K i ×} (J 1 × t 1, i) × (J 2 × t 2, i) × ·· × (J n × t n, i) ··· (3)

  Thereby, the amount of decrease in laser beam output due to the attachment of metal vapor and fume to the transmitting member 3 is predicted for each thin layer, and the laser beam output instruction value P 'is increased according to the decrease in laser beam output. Let it. Thereby, the laser beam output reaching the modeling point on the thin layer can be kept almost constant.

  As described above, the control unit 20 controls the laser along with the formation of the three-dimensional structure 2 so as to compensate for the decrease in the transmittance of the transmission member 3 due to the heating of the solidified region 1 e due to the laser beam output of the laser oscillator 30. The laser beam output of the oscillator 30 is increased. The control unit 20, which is an example of the control unit, executes the increase processing based on the schedule for increasing the laser beam output of the laser oscillator 30 generated based on the design data of the three-dimensional structure 2. The increase schedule is generated before the modeling of the three-dimensional model 2 is started based on the heating condition of the solidified region 1 e generated based on the design data of the three-dimensional model 2.

<Example>
Hereinafter, the present invention will be described in more detail with reference to specific examples.

(Example 1)
FIG. 6 is an explanatory diagram of a three-dimensional structure according to the first embodiment. In Example 1, the powder bed fusion bonding method was performed while keeping the laser beam output in the thin layer constant, and as shown in FIG. 6, three-dimensional modeling in which 25 cubes each having a length of 20 mm on each side were arranged. I shaped things. The molding condition 1 of the first embodiment is as follows.

[Modeling condition 1]
Laser beam power to be supplied to modeling point: 200W
Spot diameter: 60 μm
Scanning speed: 500mm / sec
Heater output: 200W
Introduced gas pressure: 1.0 × 10 ⁻¹ Pa
Introduced gas type: Argon gas raw material powder: SUS630 (particle size 20 μm or less)
Scanning method: Offset hatch method Scanning pitch: 50 μm

[Laser parameter creation control]
As shown in FIG. 2, laser parameter creation control was performed to set laser parameters for each thin layer 1a of the three-dimensional structure 2 to be laminated (S10). Since the three-dimensional structure 2 has a relatively simple shape, no support is required (S12).

  The model of the three-dimensional structure 2 was sliced by a slicer software with a thickness of a stacking pitch of 50 μm (S13). Laser parameters were calculated by setting a solidified region 1e on the sliced thin layer 1a (S14).

  The scanning method, which is one of the laser parameters, is an offset hatch method in which the outline is shifted inward by the scanning pitch for scanning, and the scanning pitch is 50 μm. These laser parameters were set for all layers of the three-dimensional structure and stored in the register of the control unit 20.

[Laser power reduction rate calculation control]
As shown in FIG. 4, laser power reduction rate calculation control was performed (S30).

  In an atmospheric pressure atmosphere, a transmittance measurement before molding for measuring the transmittance of the optical system 31 and the transmission member 3 was performed using a power meter FL500a-LP1 (manufactured by Ophir Japan) (S32). As a result of the measurement, the laser beam output reaching the modeling point was P1a = 187.6 W with respect to the laser beam output instruction value P1 = 200 W. This is because the transmittances of the optical system 31 and the transmission member 3 are integrated.

  After the measurement of the transmittance before modeling, an atmosphere of argon gas was set, and a test molding was performed under the molding condition 1 until the cumulative oscillation time became 14,400 sec (S33).

  In the first embodiment, the test area 15 of each thin layer 1a in the test shaping (S33) is the same as the solidified area 1e of each thin layer 1a of the three-dimensional structure 2. The number of lamination tests in the test shaping (S33) is smaller than the actual number of laminations in the three-dimensional structure 2.

After the test shaping, the atmosphere was returned to the atmospheric pressure, and the transmittance was measured after the shaping (S34). As a result of the measurement, the laser beam output reaching the modeling point was P1b = 187.2 W. Therefore, from Expression (1), the reduction rate J1 of the laser beam output per unit time under the molding condition 1 is as follows.
J ₁ = 1.389 × 10 ⁻⁷ (sec ⁻¹ )

[Laser power correction processing]
As shown in FIG. 5, a laser power correction process for correcting the laser beam output was performed (S40). Since the calculation was performed immediately after the calculation of the laser power reduction rate in the first thin layer, the correction coefficient K1 and the required value P1 ′ of the required laser beam output are as follows.
K ₁ = P _{1, b} /P=0.9360
P ₁ ′ = P / K ₁ = 213.68 W

In Example 1, the cumulative oscillation time of the first layer was t1,1 = 399.6 sec. Therefore, taking into account the decrease in laser output due to the formation of the first layer, the correction coefficient is updated to K2, and the indicated value of the laser beam output of the second layer is as follows.
_{K 2 = K 1 × (1} -t 1,1 / J 1) = 0.9359
P ₂ ′ = P / K ₂ = 213.69 W

Similarly, when the correction coefficient is repeatedly updated, K ₄₀₀ = 0.9155 and P ₄₀₀ ′ = 218.46 W in the final layer of the modeled object. The laser beam output instruction value for each layer was stored in the RAM 26 (register) in the control unit 20.

[Modeling process control]
As shown in FIG. 3, the molding process control was executed (S20).

  In the material supply step, the user supplied the raw material powder to the supply stage 6 with the supply stage 6 lowered (S21).

In the environment adjustment step, the control unit 20 exhausts the inside of the processing chamber 4 by the exhaust mechanism 13 and then introduces nitrogen gas by the gas supply mechanism 12 to increase the pressure in the processing chamber 4 to 1.0 × 10 ⁻¹ Pa. Was controlled. Further, the modeling plate 10 was heated to 250 ° C. by the heater unit 9 having an output of 300 W installed on the modeling stage 5 (S22).

  In the thin layer forming step, the control unit 20 lowers the upper surface of the raw material powder of the modeling stage 5 by ΔZ1 = 52 μm with respect to the modeling table 11 and raises the upper surface of the powder of the supply stage 6 by ΔZ2 = 55 μm with respect to the modeling table 11. In this state, the roller 7a was moved from the supply stage 6 toward the modeling stage 5 at a speed of 100 mm / sec. Thereafter, the molding stage 5 was raised so that the height of the raw material powder became ΔZ = 50 μm, and the roller 7a was moved on the molding stage 5 while rotating at a peripheral speed of 100 mm / sec. Thus, the thin layer of the raw material powder was compressed to ΔZ = 50 μm, and a thin layer having a thickness of 50 μm was formed (S23).

  In the calling step, the control unit 20 called the heating condition for each thin layer 1a including the laser beam output instruction value by the power meter (S24).

  In the heating lamination process, the control unit 20 controls the laser oscillator 30 under the called heating conditions to generate a laser beam, scans and heats and melts the thin layer, and stacks the thin layer (S25).

  The controller 20 repeats the thin-layer forming step (S23), the calling step (S24), and the heating and laminating step (S25) until the formation of the three-dimensional structure is completed (No in S26), thereby forming the three-dimensional structure.

  The control unit 20 returns the processing chamber 4 to the atmospheric pressure atmosphere after the completion of the formation of the three-dimensional structure in the formed product removal process.

[Effect confirmation]
In order to confirm the effect of Example 1, the laser beam output reaching the modeling point was measured with a power meter. As a result, when the laser beam was irradiated with the corrected indicated value P ₄₀₀ ′ = 218.46 W of the laser beam output, the laser beam output reaching the modeling point was equivalent to the desired 200 W. From this, in the first embodiment, even if the transmittance of the transmission member 3 decreases, the amount of decrease in the transmittance can be accurately predicted and integrated, whereby the laser beam output reaching the modeling point can be reduced. It became almost constant, and it became clear that a stable three-dimensional structure can be formed.

(Example 2)
As shown in FIG. 6, in the forming process control (S20) of the second embodiment, the same three-dimensional forming as in the first embodiment was formed by performing laser beam output control while interweaving a plurality of heating conditions.

  In the heating and laminating step of FIG. 3, the same molding condition 1 as in Example 1 was adopted for the contour portion 0.5 mm from the outermost periphery of the three-dimensional structure. By lowering the laser beam output, narrowing the laser spot diameter, and slowing down the scanning speed, the molding accuracy was improved and the surface properties of the three-dimensional object were improved. For the inside of the contour part, the following molding condition 2 was adopted to shorten the molding time. In the molding condition 2, the laser beam output was increased, the laser spot diameter was increased, and the scanning speed was increased compared to the molding condition 1.

[Modeling condition 2]
Laser beam output to be supplied to modeling point: 500W
Spot diameter: 110 μm
Scanning speed: 700mm / sec
Heater output: 500W
Introduced gas pressure: 1.0 × 10 ⁻¹ Pa
Introduced gas type: Argon gas raw material powder: SUS630 (particle size 20 μm or less)
Scanning method: Offset hatch method Scanning pitch: 50 μm

[Laser power reduction rate calculation control]
As shown in FIG. 4, laser power reduction rate calculation control was performed (S30). As a result, the reduction rate J2 of the laser beam output per unit time under the molding condition 2 was as follows.
J2 = 1.80 × 10 ⁻⁷ (sec ⁻¹ )

In Example 2, the cumulative oscillation time for one layer of the thin layer 1a is t1,1 = 39.0 sec for the shaping condition _{1, and} t _2,1 = 128.8 sec for the shaping condition 2. Further, the initial correction factors _{K 1 was} K 1 = 0.9130. Therefore, the correction coefficient K ₂ of the second layer is as follows.
_{K 2 = K 1 × (1} -t 1,1 / J 1) × (1-t 2,1 / J 2)
= 0.9129

Similarly, when the update of the correction coefficient is repeated, K ₄₀₀ = 0.9026 in the final layer of the modeled object. As a result, assuming that the laser beam output to be supplied to the modeling point is 200 W, the required value of the laser beam output is 221.59 W. Also, assuming that the laser beam output to be supplied to the modeling point is 500 W, the required indicated value of the laser beam output is 553.97 W.

[Modeling process control]
As shown in FIG. 3, the molding process control in which the molding condition 1 and the molding condition 2 were interwoven was executed in the same procedure as in the first embodiment (S20).

[Effect confirmation]
After the formation of the three-dimensional structure, the processing chamber 4 was returned to the atmospheric pressure atmosphere, and the power of the laser beam reaching the formation point was measured with a power meter to confirm the effect of the second embodiment.

As a result, when irradiation was performed with the laser beam output instruction value P ₄₀₀ ′ = 221.59 W, the laser beam output reaching the modeling point was equivalent to the desired 200 W. Irradiation was performed with the laser beam output indicated value P ₄₀₀ ′ = 553.97 W, and the laser beam output reaching the modeling point was equivalent to the desired 500 W.

  For this reason, in the first embodiment, the amount of decrease in the transmittance of the transmission member 3 is predicted and integrated, so that the molding point is reached even when the powder bed fusion bonding method is performed using a plurality of molding conditions. It was found that the laser beam output could be kept almost constant.

(Comparative Example 1)
In Comparative Example 1, the same molding as in Example 1 using the molding condition 1 was performed without correcting the laser beam output.

In Comparative Example 1, the initial correction coefficient was K ₁ = 0.9025. Therefore, according to equation (2), the laser beam output instruction value P ′ is P ′ = 221.60 W.

  As shown in FIG. 3, the molding process control under the molding condition 1 was executed in the same procedure as in the first embodiment (S20).

  In Comparative Example 1, the heating lamination step (S25) was performed with the laser beam output instruction value P 'being a fixed value over all the thin layers of the three-dimensional structure.

[Effect confirmation]
After the formation of the three-dimensional structure was completed, the processing chamber 4 was returned to the atmospheric pressure atmosphere, and the power of the laser beam reaching the modeling point was measured with a power meter to confirm the effect of Comparative Example 1.

  As a result, when irradiation was performed at the laser beam output instruction value P ′ = 221.60 W, the laser beam output reaching the modeling point was 195.6 W. From this, it was found that, unless the laser beam output was corrected, a desired laser beam output could not be supplied to the modeling point due to a decrease in the transmittance of the transmission member 3.

  As a result, in Comparative Example 1, there is a possibility that the shaping quality becomes uneven in the three-dimensional structure, and the desired function and characteristics of the metal material cannot be obtained. On the other hand, in the first embodiment, even when the heating condition changes for each work in the molding process of the powder bed fusion bonding method, and even in the same work, the light passes through the transmission member 3 and reaches the thin layer 1a. The amount of decrease in laser power can be predicted fairly accurately. Then, by increasing the laser beam output power of the laser oscillator 30 in accordance with the amount of decrease in the laser power reaching the thin layer 1a, a desired laser power is supplied to the thin layer 1a, and a stable high-quality tertiary An original object can be formed.

(Effect of Embodiment 1)
In the first embodiment, the rate at which the laser beam output is increased with the accumulation of the scanning heating of the thin layer 1a is changed according to the heating condition of the laser oscillator 30. For this reason, even if the heating conditions of the thin layer 1a by the laser beam are different, excess or deficiency of the heating amount in the solidified region of the thin layer 1a is suppressed.

  In the first embodiment, the process of increasing the laser beam output of the laser oscillator 30 is performed so as to compensate for the decrease in the transmittance of the transmission member 3 due to the heating of the solidified region 1e by the laser beam during the forming process of the three-dimensional structure 2. Execute. For this reason, it is possible to set the laser beam output of the laser oscillator 30 with little excess or deficiency according to the heating condition of the solidified region 1e.

  In the first embodiment, the increase process is performed based on the schedule for increasing the laser beam output of the laser oscillator 30 generated from the design data of the three-dimensional structure 2. Therefore, it is not necessary to measure the laser beam output during the forming process of the three-dimensional structure 2. The configuration and control for measuring the laser beam output and feeding back the measurement result to the laser oscillator 30 are unnecessary. There is no fear that the laser beam output is inappropriately controlled due to the cumulative measurement error of the laser beam output or the temporary measurement error of the laser beam output.

  In the first embodiment, the increase schedule is generated based on the heating condition of the solidified region 1e generated from the design data of the three-dimensional structure 2. The heating conditions include the type of the raw material powder 1, the laser beam output, the beam spot diameter of the laser beam, the scanning speed of the laser beam, the type and pressure of the atmosphere in the processing chamber 4, and the thin layer by the heater unit 9. 1a auxiliary heating conditions. Therefore, it is possible to accurately estimate the required increase in the laser beam output of the laser oscillator 30 for each solidified region 1e. By accurately estimating the state of decrease in the transmittance of the transmission member 3 due to the difference in the heating conditions, it is possible to obtain an increase in the laser beam output of the laser oscillator 30 with little excess or deficiency.

  In the first embodiment, the control unit 20 generates the schedule for increasing the output of the laser beam used in the three-dimensional printing apparatus 100 by itself. For this reason, it is possible to estimate the state of decrease in the transmittance of the transmission member 3 in consideration of the individual difference of the three-dimensional printing apparatus 100, and to obtain an increase in the laser beam output of the laser oscillator 30 with little excess or deficiency.

  In the first embodiment, the state of decrease in the transmittance of the transmission member 3 is estimated based on the heating condition of the solidified region 1e, and a schedule for increasing the laser beam output is generated based on the estimated state of the decrease in transmittance of the transmission member 3. I do. For this reason, it is possible to estimate the state of decrease in the transmittance of the transmission member 3 in consideration of the difference in the heating conditions of the solidified region 1e, and to obtain an increase in the laser beam output of the laser oscillator 30 with little excess or deficiency.

  In the first embodiment, data on the amount of increase in the laser beam output required to perform the increase process is obtained based on the experimental results of test shaping. For this reason, the state of reduction in the transmittance of the transmission member 3 is estimated by matching the three-dimensional object 2 at each thin layer level for the purpose of combining a plurality of heating conditions, and the laser beam output of the laser oscillator 30 is excessive or insufficient. Can be obtained with a small increase.

  In the first embodiment, the thin layer 1a of the raw material powder 1 is formed in the same manner as when the three-dimensional modeled object 2 is formed by the supply mechanism 7, and the test area 15 of the thin layer 1a is heated under one combination of heating conditions. Perform lamination for the number of tests. For this reason, the heating condition of each thin layer 1a of the three-dimensional structure 2 and the state of fume generation can be accurately reproduced by test molding, and the accuracy of the schedule for increasing the laser beam output can be increased.

  In Example 1, the transmittance of the transmitting member 3 is measured by performing both the transmittance measurement before the shaping and the transmittance measurement after the increase. For this reason, a change in the transmittance of the transmission member 3 can be estimated more accurately than when the transmittance measurement before modeling is not performed. In the first embodiment, the test area 15 of each thin layer 1a in the test shaping is the same as the solidified area 1e of each thin layer 1a of the three-dimensional structure 2. For this reason, the state of fume generation in the solidified region 1e of the three-dimensional structure 2 can be reproduced with high accuracy in test modeling using the test region 15. In the first embodiment, the number of times of lamination in the test shaping is smaller than the actual number of times of lamination in the three-dimensional structure 2. Therefore, the time required for test shaping can be reduced.

<Embodiment 2>
In the first embodiment, the control unit 20 generates the increase schedule used for the laser beam output increase processing. On the other hand, in the second embodiment, as shown in FIG. 1, a computer 25 different from the control unit 20 generates an increase schedule used for the laser beam output increase processing. The configuration of the three-dimensional printing apparatus 100 and the modeling control in the three-dimensional printing object 2 are the same as those in the first embodiment, and thus, duplicate description will be omitted.

(Control of Embodiment 2)
FIG. 7 is a flowchart of laser parameter creation control according to the second embodiment. As shown in FIG. 7, the computer 25 executes laser parameter creation control to create laser parameters including a schedule for increasing the laser beam output (S50).

  The computer 25 creates a 3D model of the three-dimensional structure from the design data (CAD data) of the target three-dimensional structure 2 (S51). If the 3D model of the three-dimensional structure has no independence, the computer 25 corrects the 3D model by adding a support member for imparting independence during processing (S52).

  As a determination step, the computer 25 determines the heating condition of the solidified region 1e from the design data of the three-dimensional structure 2 (S53). The computer 25 slices the 3D model of the three-dimensional structure with the thickness of the thin layer using the slicer software, and obtains a solidified region 1e corresponding to one layer of the thin layer 1a. The computer 25 calculates the required heating amount for each portion of the solidified region 1e, sets the laser parameters, creates a heating condition including the laser parameters, and stores it in the RAM 26 of the control unit 20 (S53). As an estimation step, the computer 25 estimates the state of decrease in the transmittance of the transmission member 3 based on the heating condition of the solidified region 1e (S54).

  As a generation step, the computer 25 generates a laser beam output increase schedule based on the estimated reduction state of the transmittance of the transmission member 3. The computer 25 generates an increase schedule of the laser beam output as a part of the control schedule of the laser oscillator 30 through the shaping process of the three-dimensional structure 2 (S55).

(Effect of Embodiment 2)
In the second embodiment, a computer 25 different from the control unit 20 generates a laser beam output increase schedule. For this reason, after acquiring the processing program of the three-dimensional structure 2, the modeling of the three-dimensional structure 2 can be started immediately without generating a laser beam output increase schedule in the control unit 20.

<Other embodiments>
The three-dimensional printing apparatus of the present invention is not limited to the specific configuration of each part, the form of parts, and the actual dimensions in the first embodiment. Another embodiment in which part or all of the configuration of the first and second embodiments is replaced with an equivalent member can be implemented. In the first embodiment, the embodiment in which the solidified region 1e of the thin layer 1a is melted by a laser beam has been described. However, the present invention may be implemented in an embodiment in which the solidified region 1e of the thin layer 1a is sintered.

  In the first embodiment, the laser beam output rate, the cumulative oscillation time, the spot diameter, the scanning speed, the heater output, the type and pressure of the atmosphere, and the conditions for forming the thin layer of the molding material are equally reproduced to control the laser power reduction rate (S30). Was executed. In the first embodiment, test shaping was performed to determine the reduction rate J1 of the laser beam output per unit time in one combination of the heating conditions. Then, laser beam output correction (S40) was performed based on the laser power reduction rate calculation control (S30).

However, even if the test molding in which one combination of the heating conditions is set as in the first embodiment is not performed to the end, the molding point temperature of the laser beam spot is measured during the test molding, and evaporation rate a _v can be estimated.

  For example, considering the case where the temperature of the processing point is 1800 ° C. and the case of aluminum where the temperature of the processing point is 1000 ° C., the numerical values of the heating conditions are as follows.

In general, when the material is heated in a vacuum, the mass of material to be vaporized per unit area of the surface of the material, apply the formula Langmuir, evaporation rate a _v is obtained by the following equation.
^{_{a v = 5.85 × 10 -2 ×}} P × (T) × (M / T) 0.5
Thus, as it follows and determining the evaporation rate a _v based on the values in Table 1.

Evaporation rate a _v of the material powder 1, because it corresponds to the amount of decrease in the transmittance of the transparent member 3 of each heating of the thin layer 1a, per unit time according to the thus computed evaporation rate a _v It is possible to obtain the laser beam output decrease rate J1. Then, it is possible to set an additional rate of the laser beam output for each heating of the thin layer 1a based on the laser beam output reduction rate J1 per unit time.

  Note that, instead of actually measuring the temperature of the processing point by test molding in which one combination of heating conditions is set as in Embodiment 1, the temperature of the processing point is calculated by computer simulation of heating of the solidified region 1e based on the laser beam output. You may ask.

When determining the amount of decrease in the transmittance of the transmission member 3 based on the evaporation rate _av , the thickness t of the substance adhering to the transmission member 3 may be determined. The evaporation amount of the material powder 1 m [g] is proportional to the rate of evaporation _{a v.} Then, the evaporation angle distribution of the substance from the evaporation source floating in the space is uniform in all directions. For this reason, the film thickness t of the substance adhering to the transmission member 3 is obtained by, for example, the following equation.
t = (m / ρ) × cos φ / 4π (h ² + l ² ) ^0.5
Thus, the film thickness t adhering to the transmission member 3 is calculated based on the numerical values in Table 1 as follows.

  Therefore, the film thickness per unit time (t / s) is obtained from the processing time s and the film thickness t, and the reduction rate J1 of the laser beam output per unit time can be calculated.

1: Raw material powder, 1a: thin layer, 1e: solidified region, 2: three-dimensional model, 3: transmission member, 4: container (processing chamber), 5: thin layer forming section (modeling stage), 6: thin Layer forming section (supply stage), 7: thin layer forming section (supply mechanism), 9: auxiliary heating means (heater unit),
12: substance supply unit (gas supply mechanism), 13: pressure reducing unit (exhaust mechanism), 15: test area, 20: control unit, 21: reading device, 22: recording medium, 30: heating means (laser oscillator), 31 : Heating means (optical system), 32: heating means (fiber cable), 100: three-dimensional modeling device

Claims (16)

A thin layer forming section for forming a thin layer of the raw material powder,
A container for accommodating the thin layer forming portion,
A transmission member provided in the container,
Heating means for forming a three-dimensional structure by heating and laminating a predetermined region of the thin layer by the laser beam transmitted through the transmitting member,
A control unit that executes a process of increasing a laser beam output of the heating unit along with shaping of the three-dimensional structure so as to compensate for a decrease in transmittance of the transmission member due to heating of the predetermined region by the heating unit, equipped with a,
Wherein the control unit, the three-dimensional model a three-dimensional modeling apparatus characterized that you perform the increasing process on the basis of increasing schedule of the laser beam output of the generated said heating means based on the design data of the. The three-dimensional printing apparatus according to claim 1 , wherein the increase schedule is generated based on a heating condition of the predetermined region generated based on design data of the three-dimensional printing object. The heating conditions, the type of the raw material powder, and an output of the laser beam, and the beam spot diameter of the laser beam, according to claim 2, characterized in that it comprises a scanning speed of the laser beam 3D modeling equipment. A decompression unit for decompressing the inside of the container,
And a substance supply unit which forms the atmosphere of the time of heating the predetermined area by supplying material to the decompressed the container by the vacuum unit,
The three-dimensional modeling apparatus according to claim 3 , wherein the heating condition includes a type of the atmosphere and a pressure. An auxiliary heating means for auxiliary heating the thin layer heated by the laser beam output of the heating means,
The three-dimensional modeling apparatus according to claim 4 , wherein the heating condition includes an auxiliary heating condition of the thin layer by the auxiliary heating unit. A three-dimensional modeling method for modeling a three-dimensional molded object by the three-dimensional modeling device according to any one of claims 1 to 5 ,
The controller, the thin layer forming step of controlling the thin layer forming section to form a thin layer of the raw material powder,
A lamination step in which the control unit controls the heating unit to heat and laminate the predetermined region,
An output increasing step of increasing the laser beam output of the heating means by executing the increasing process in accordance with the molding process of the three-dimensional object. A program for causing a computer to execute the three-dimensional modeling method according to claim 6 . A recording medium on which the program according to claim 7 is recorded. A method for generating an increase schedule, wherein the increase schedule used by the control unit in the three-dimensional printing apparatus according to claim 1 or 2 , is generated by the control unit.
An estimation step in which the control unit estimates a state of decrease in transmittance of the transmission member based on a heating condition of the predetermined region,
A generation step for the control unit to generate the increase schedule based on the state of decrease in the transmittance of the transmission member estimated in the estimation step. A method of generating an increase schedule, wherein the increase schedule used by the control unit in the three-dimensional printing apparatus according to claim 1 or 2 , is generated by a computer different from the control unit,
A determination step in which the computer determines the heating condition of the predetermined area from the design data of the three-dimensional structure,
An estimation step in which the computer estimates a decrease in transmittance of the transmission member based on the heating condition determined in the determination step,
A generation step for the computer to generate the increase schedule based on the decrease in the transmittance of the transmission member estimated in the estimation step. The computer method of generating increased schedule of claim 1 0, characterized in that to generate the increase scheduled as part of the control schedule of the heating means through a shaped course of the three-dimensional model. Claim 1 0 or program for executing a method of generating increased schedule according to computer 1 1. A recording medium recording the program according to claim 1 2. The three-dimensional modeling apparatus according to any one of claims 1 to 5 , wherein the controller is configured to generate an increase in a laser beam output of the heating unit for performing the increase processing,
A thin layer forming step of forming the thin layer by the thin layer forming section,
A lamination step of heating the test region of the thin layer by the heating means under one combination of heating conditions and laminating the test number of times;
A measuring step of measuring the transmittance of the transmitting member after at least the laminating step,
A generating step of generating the increase amount based on a measurement result of the measurement step. Wherein the test area in the lamination step, the method of generating the increment of claim 1 4, wherein the same as the predetermined region at the time of shaping the 3D object. The number of tests in the lamination step, increase generation method according to claim 1 5, characterized in that less than number of lamination in the three-dimensional model.

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