JP2018003087A - Three-dimensional molding apparatus, and method for manufacturing three-dimensionally molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce figure defects of a molded article by relaxing a residual stress generated in the molded article in powder bed melt bonding and also holding an even temperature distribution of the molded article.SOLUTION: A three-dimensionally molded article is manufactured by repeating operations of laying a thin film composed of a conductive material powder 22 on a molding area (hole 6a), and selectively radiation-heating the material powder 22 formed into a film on the molding area with a laser beam L to sinter. An induction heating coil 8 is arranged around the periphery of the molding area (hole 6a). A control device (600) performs a temperature control of a molded article O having been molded inside the molding area through electrifying control of the induction heating coil 8. A temperature of non-sintered material powder in the molding area is controlled by circulating refrigerant in the hollow induction hating coil 8.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a three-dimensional modeling apparatus that manufactures a three-dimensional structure by repeatedly radiatively heating and sintering a material powder laid on a modeling stage, and a method for manufacturing the three-dimensional structure.

  2. Description of the Related Art Conventionally, a powder bed fusion bonding technique for modeling a three-dimensional model has been used in products such as so-called 3D printers.

  In this powder bed fusion, for example, an energy beam such as a laser beam is used to form a three-dimensional part by radiatively heating and sintering material powders one by one in layers (for example, the following patent documents) 1). The first layer made of the material powder is irradiated with a laser beam to selectively sinter necessary portions, and then a second layer of the material powder is formed on the first layer. Similarly, the second layer is irradiated with the laser beam. While selectively sintering, it is joined to the sintered portion of the first layer. Thereafter, the above process is repeated for the third and subsequent layers to manufacture a three-dimensional part. The laser beam is used as a means for selectively applying an amount of heat according to the desired shape of the modeled object, but another energy beam may be used as the means for applying an amount of heat.

  In powder bed fusion bonding, when the outermost layer of the spot irradiated with the laser beam is sintered, the outermost layer and a part of the sintered object underneath are instantaneously thermally expanded, and then suddenly Residual stress may occur in the vicinity of the spot due to cooling shrinkage. In many powder bed fusion bonding modeling apparatuses, the modeled object is greatly deformed because it is constrained by the rigidity of the base plate to which the first layer is joined and the fastening force for fastening the base plate to the apparatus. There is no. However, after removing the modeled object from the apparatus or after removing the base plate, a shape defect such as warping or distortion of the modeled object may occur due to the release of stress remaining during modeling.

  In consideration of the shape defect of such a modeled object, the latest formed sintered layer is reheated to form a remelted portion, thereby removing the residual stress of the modeled object during modeling (for example, the following Patent Document 2) has been proposed. In addition, it is assumed that the stress remaining in the portion corresponding to the outermost layer of the final shaped part is a main factor of the shape defect, and only such a portion is reheated during shaping to relieve the residual stress (for example, The following patent document 3) has also been proposed.

Japanese Patent No. 2620353 Japanese Patent No. 4693681 Japanese Patent No. 5612530

  According to the techniques as described in Patent Documents 2 and 3 above, the application of the main amount of heat to the modeled object being modeled is limited to the top of the modeled object. Distribution may occur. When the temperature distribution is eliminated after modeling, the modeled object with such a temperature distribution has a difference in the amount of shrinkage between the part that was hot and the part that was cold during modeling. A shape defect may occur.

  In view of the above problems, the object of the present invention is to relieve residual stress generated in a shaped article in powder bed fusion bonding, and to suppress the shape defect of the shaped article by keeping the temperature distribution of the shaped article uniform. There is to do.

  In order to solve the above problems, in the present invention, a conductive material powder is laid in a modeling area, and a part of the laid material powder is selectively radiantly heated and sintered to repeat three-dimensional operation. In the three-dimensional modeling apparatus that manufactures a modeled object, the induction heating coil that is arranged on the outer periphery of the modeling area and induces heat generation of the modeled modeled object inside the modeling area by energization, and energization of the induction heating coil The control apparatus which performs the temperature management of the said molded object by controlling was employ | adopted.

  According to the above configuration, by controlling the temperature of the model so as to heat or keep the model during the modeling period, it is possible to suppress the residual stress in the model and release the residual stress after the model is finished. Therefore, it is possible to reduce the shape defects caused by the above and to perform highly accurate three-dimensional modeling. During modeling, the temperature difference in the vertical direction of the modeled object can be suppressed by heating or keeping the entire modeled object, and shape defects caused by the temperature distribution during modeling can be suppressed.

It is the schematic diagram which showed the structural example of the three-dimensional modeling apparatus which can implement this invention. It is the schematic diagram which showed the structural example of the test container used for the confirmation experiment of the diffusion joining boundary temperature of modeling material. It is the schematic diagram which showed the vicinity of the modeling area in the apparatus of FIG. In the apparatus of FIG. 1, it is the schematic diagram which showed the vicinity of the modeling area when modeling of a lower layer part is complete | finished. In the apparatus of FIG. 1, it is the schematic diagram which showed the vicinity of the modeling area when modeling of a middle layer part is complete | finished. In the apparatus of FIG. 1, it is the schematic diagram which showed the vicinity of the modeling area when modeling of an upper layer part is complete | finished. In the apparatus of FIG. 1, it is the table | surface figure which showed the control command value and control point of each heating zone in each step of modeling. In the apparatus of FIG. 1, it is explanatory drawing which showed the heating output control in the case of performing temperature control of the upper surface of a molded article. In the apparatus of FIG. 1, it is explanatory drawing which showed the example of control of the control command value in heating zones other than the uppermost end and the lowest end of a molded article. It is the schematic diagram which showed the structure in the case of providing an insulator and an induction heating coil independently regarding the modification of the apparatus of FIG. It is explanatory drawing which showed the structure of the induction heating system of the apparatus of FIG. It is explanatory drawing which showed the structural example of the induction heating coil used in the apparatus of FIG. It is the block diagram which showed the structural example of the control system (control apparatus) of the apparatus of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to embodiments shown in the accompanying drawings. The following embodiment is merely an example, and for example, a detailed configuration can be appropriately changed by those skilled in the art without departing from the gist of the present invention. Moreover, the numerical value taken up by this embodiment is a reference numerical value, Comprising: This invention is not limited.

<Embodiment 1>
FIG. 1 shows a configuration example of a three-dimensional modeling apparatus employing the present invention. The apparatus shown in FIG. 1 is a three-dimensional modeling apparatus such as a 3D printer that manufactures a three-dimensional structure by repeatedly radiating and heating a conductive material powder deposited in a modeling area and sintering it. is there.

  In the modeling apparatus of FIG. 1, the modeling table 4 is accommodated in the modeling chamber 1, and the laser light source 12 as an energy beam irradiation apparatus and its scanning system are arranged outside the modeling chamber 1. The modeling chamber 1 is configured to be airtight with respect to the external atmosphere. The modeling chamber 1 is provided with an exhaust port 2, and the inside of the modeling chamber 1 can be decompressed by a vacuum pump (not shown) through the exhaust port 2. In addition, the modeling chamber 1 of the present embodiment is configured such that a desired gas (for example, an inert gas) can be sealed through the air supply port 3 after decompression.

  A laser irradiation apparatus for irradiating a laser beam L as an energy beam for performing modeling by radiation heating is disposed above the modeling chamber 1 in FIG. This laser irradiation system includes, for example, a laser light source 12, a collimator lens 13, a beam expander 14, a condensing lens 15, a galvano scanner 16, and an f-θ lens 17 for scanning a laser spot at a constant speed on an imaging surface. Etc. The galvano scanner 16 is modulated by, for example, a 3D CAD (or 3DCG) signal representing the shape of the modeled object and controlled to scan the laser spot in a horizontal plane in a shape corresponding to one layer of the modeled object by a control device described later. The

  A modeling table 4 made of a material such as metal or resin is installed in the modeling chamber 1. The modeling table 4 is provided with holes 5a, 6a, 10a in the vertical direction, for example. The cross-sectional shape of these holes 5a, 6a, and 10a is arbitrary, such as a rectangle and a circle.

  The holes 5a, 6a, and 10a correspond to holes for storing material powder before modeling, holes for modeling, and holes for collecting unsintered material powder, respectively. In particular, the hole 6a for modeling corresponds to a modeling area for performing 3D modeling.

  A material supply stage 5 that can be moved up and down is arranged inside the hole 5a for storing the material powder. By this material supply stage 5, the material powder stored in advance in the upper part of the hole 5 a before modeling can be raised, and a necessary amount of material powder can be appropriately supplied onto the modeling table 4 by the powder spreading roller 11. The material supply stage 5 is configured to be movable up and down by, for example, a driving means outside the modeling chamber 1 (for example, a transmission system (not shown) using a servo motor + rack & pinion). In the present embodiment, the material powder stored in the hole 5a is a conductive metal material.

  Inside the hole 6a for modeling, a modeling stage 6 that can be moved up and down is arranged. A base plate 7 is provided on the modeling stage 6. The base plate 7 is fixed to the modeling stage 6 by a technique such as screwing. The modeling stage 6 is configured to be movable up and down by, for example, a driving means outside the modeling chamber 1 (for example, a transmission system (not shown) using a servo motor + a rack & pinion, etc.), and will be described later as the modeling for each layer proceeds. It is controlled to descend, for example, by the device. A collection container 10 is disposed in the material collection hole 10 a of the modeling table 4.

  In this embodiment, the helical induction heating coil 8 is arranged on the peripheral side surface of the hole 6a for modeling. In this embodiment, the induction heating coil 8 is used for induction heating of a modeled object (O) modeled from the metallic material powder (22). In FIG. 1 (or FIG. 12), only two turns of the induction heating coil 8 are shown, but the number of loops of the induction heating coil 8 is arbitrary.

  The inner wall of the hole 6 a (modeling area) for modeling the modeling table 4 is configured by the insulator 9, and the induction heating coil 8 is embedded in the insulator 9. The insulator 9 can be formed by using an insulating ceramic material, in particular, a material such as aluminum nitride or silicon nitride that is resistant to thermal shock, by a method such as coating, drying, or sintering. The induction heating coil 8 and the following thermocouple 18 can be embedded in the insulator 9 when the insulator 9 is formed. By this insulator 9, the induction heating coil 8 (or a cooling device constituted by this hollow portion) is isolated from the inside of the modeling area (hole 6a).

  The induction heating coil 8 has a shape as shown in FIG. 12, for example, and includes a spiral portion and a lead portion 81. The shape of the induction heating coil 8 is the same as that of the induction heating coil 37 used in the third embodiment described later. The induction heating coil 8 is made of a conductive material such as copper, preferably a hollow pipe material. Electrically, the lead part 81 is connected to a power supply system (FIG. 11) described later via power supply lines 82 and 82. Moreover, the hollow part of the induction heating coil 8 is connected to a cooling system (FIG. 11) described later, and as shown by 81a and 81b, a refrigerant (for example, cooling water) is supplied, recovered, and circulated. In this way, by circulating a coolant (for example, cooling water) through the induction heating coil 8, the insulator 9 on the inner wall of the hole 6a to be specifically modeled is cooled (FIG. 1), and the temperature of this portion is controlled.

  In this embodiment, by controlling the induction heating by the induction heating coil 8 and the circulation of the refrigerant in the inside by a control device to be described later, in particular, the shaped object O of FIG. 1 and the modeling area (modeling is performed). The temperature of the inner wall portion of the hole 6a) is controlled.

  For this temperature management, a radiation thermometer 19 is arranged as a first temperature measuring device that measures the temperature of the uppermost part of the shaped object (O) that has been shaped in the modeling area (hole 6a). Moreover, the thermocouple 18 is arrange | positioned at the baseplate 7 as a 2nd temperature measurement apparatus which measures the temperature of the lowest part of the modeling molded object (O) in the modeling area (hole 6a).

  Moreover, the thermocouple 20 is arrange | positioned as a 3rd temperature measurement apparatus which each detects the temperature of the some measurement point arrange | positioned in the different position around the modeling area (hole 6a). It constitutes temperature detecting means for the unsintered material powder 22 around the side surface of the modeled object (O) surrounding the modeled modeled object, particularly the inner wall portion of the modeled area (hole 6a). The thermocouple 20 is embedded and arranged inside the insulator 9.

  In the modeling apparatus of FIG. 1, the powder spreading roller 11 is arranged so that the region on the upper surface of the opening from the upper part of the hole 5 a of the modeling table 4 to the upper part of the collection container 10 can be moved. Known configurations can be used for the rotational drive system of the powder spread roller 11 and the (horizontal) reciprocating system in the above region. Although not shown in detail in FIG. 1, the driving means for the powder spreading roller 11 can be controlled independently of at least the horizontal (horizontal) reciprocation in FIG. 1 and the forward and reverse rotational movements. Composed. The supply and recovery of the material powder by the powder spreading roller 11 at the time of modeling is performed as follows, for example.

  In the modeling of one layer, the material supply stage 5 is raised so that an appropriate amount of the material powder on the upper part of the hole 5a can be supplied. On the other hand, for example, the modeling stage 6 lowers the height of one layer of the modeled object and stands by. In this state, the powder spread roller 11 is rolled from the left side of the drawing from the upper part of the hole 5a to the upper part of the modeling stage 6 to adjust the material powder for one layer, and then the modeling stage 6 or a modeled object that has already been modeled ( O) Supply above. Furthermore, by rolling the powder spreading roller 11 to the opening at the top of the collection container 10, excess material powder exceeding one layer is collected in the collection container 10.

  FIG. 11 shows an example of a hardware configuration for performing heating and cooling (temperature management) using the induction heating coil 8 of the modeling apparatus (FIG. 1). In FIG. 11, the lead portion 81 of the induction heating coil 8 is electrically connected to an AC power source 86 via a power line 82, a matching transformer 88, and a power line 84. The AC power source 86 is preferably one that can perform auto-matching of output frequencies as described later, for example. A CPU (601) of the control device (600) to be described later can control the output AC power, frequency, duty ratio, etc. of the AC power source 86 via the sequencer 87.

  On the other hand, the refrigerant (cooling water) in the induction heating coil 8 is circulated by the chiller 85. The chiller 85 communicates with the hollow refrigerant (cooling water) flow path of the induction heating coil 8 through the refrigerant flow path 83. The chiller 85 is for performing circulation control of this type of refrigerant (cooling water), and includes, for example, a heating (or cooling) element that controls the temperature of the refrigerant (cooling water), and a flow rate control unit such as a pump. . In addition, the chiller 85 includes interface means with a control circuit, and a CPU (601) of a control device (600), which will be described later, appropriately transmits control information to set the temperature of the refrigerant (cooling water) and per unit time. The flow rate can be set.

  FIG. 13 shows a configuration example of the control device 600 (control system) of the modeling apparatus of FIG. The control system in FIG. 13 includes a CPU 601, a ROM 602, a RAM 603, interfaces 604, 605, and 606, which are general-purpose microprocessors. In addition, the control device 600 may be provided with a network interface, for example, an external storage device configured with a disk device such as an SSD or an HDD, as necessary.

  The ROM 602 stores a control program and control data for causing the CPU 601 to execute, for example, basic control of the modeling apparatus of FIG. 1 and temperature management of the present embodiment. Note that the storage area for this purpose may be configured by a storage device such as an E (E) PROM so that the control program and control data stored in the ROM 602 can be updated later. The RAM 603 is composed of a DRAM element or the like, and is used as a work area for the CPU 601 to execute various controls and processes. A function related to a temperature management control procedure to be described later is realized by the CPU 601 executing a control program (for example, FIG. 8) of the present embodiment. In the case where an external storage device such as an SSD or HDD is provided, the above control program and control data can be stored in a file format, for example. An external storage device such as an SSD or HDD can also be used to arrange a virtual storage area that complements the main storage area on the RAM 603.

  The external storage device is not limited to an SSD or HDD, but may be configured by a recording medium such as various removable optical disks, a removable SSD or HDD disk device, or a removable flash memory. Such various detachable computer-readable recording media are used, for example, for installing or updating a control program constituting a part of the present invention in the ROM 602 (E (E) PROM area). be able to. In this case, various detachable computer-readable recording media store the control program constituting the present invention, and the recording medium itself constitutes the present invention.

  The control data stored in the ROM 602 (or external storage device) includes, for example, “diffusion bonding boundary temperature” (described later) related to a modeled object formed from a specific material powder obtained by an experiment (FIG. 2 described later). Contains data.

  The CPU 601 executes a modeling control program, a temperature control control program, firmware, and the like stored in the ROM 602 (or an external storage device (not shown)). Thereby, for example, each functional block (or control step) (or control step) shown in FIG. 8 is realized.

  In FIG. 13, the control device 600 is provided with interfaces 604, 605, and 606. Among these, for example, the interface 604 is used to receive three-dimensional modeling data (data format is arbitrary such as 3D CAD and 3DCG data) from an external device. The interface 605 is used to access the controlled element 607 (P) of the modeling apparatus of FIG. The controlled element 607 (P) includes, for example, a drive system for the dusting roller 11, a laser light source 12, and a drive system (for a 3D printer) that controls the modeling stage 6 to move up and down. Further, when a decompression device for adjusting the atmosphere in the modeling chamber 1 or an inert gas supply device (both are not shown in detail) are arranged, these members are also included in the controlled element 607 (P). It is included as a control target of the CPU 601.

  FIG. 13 particularly shows the chiller 85, the sequencer 87, and the sensors 609 of the temperature management system. The sensors 609 correspond to the thermocouples 18 and 20 or the radiation thermometer 19 for temperature detection. Each part of these temperature management systems is controlled by the CPU 601 via the interface 606. For example, the CPU 601 can acquire the measurement information of the sensors 609 via the interface 606, and can control the operations of the chiller 85, the sequencer 87, and the like as desired by transmitting a control signal in a predetermined signal format.

  When a network interface is arranged, this interface can be used to communicate with other control terminals (not shown), other modeling apparatuses, servers on the network, and the like. For this network interface, for example, a network communication method using wired or wireless connection, for example, a communication method such as IEEE802.3 for wired connection or IEEE802.11 or 802.15 for wireless connection can be used. The interface 604 may be a network interface, and modeling data may be input / output via network communication.

  Next, an outline of 3D modeling processing in the modeling apparatus of FIG. 1 will be described. The modeling chamber 1 can be accessed from a work window (not shown). Prior to modeling, a storage operation of the modeling material (material powder 22) on the material supply stage 5 and a mounting operation of the base plate 7 are performed in advance.

  Thereafter, the atmosphere in the modeling chamber 1 is adjusted. For example, the work window (not shown) is closed to ensure airtightness in the chamber again. If the modeling material is a material that easily oxidizes, the inside of the chamber is depressurized from the exhaust port 2 by a vacuum pump in order to reduce the oxygen concentration in the chamber. Further, after that, an inert gas may be introduced from the air supply port 3 and sealed. As the inert gas, nitrogen, argon or the like is preferably used. If only the oxygen concentration is a problem as an atmosphere requirement in the modeling chamber 1, the modeling chamber 1 does not necessarily need to be sealed. Further, for example, the oxygen concentration in the modeling chamber 1 may be controlled below a specified value by constantly supplying and discharging an inert gas during modeling. Similarly, modeling may be performed while collecting fumes generated in the modeling chamber 1 and floating material powder by supplying and discharging an inert gas.

  After confirming that the atmosphere in the modeling chamber 1 has a desired degree of vacuum, oxygen concentration or sealed gas concentration, the base plate 7 is preheated.

  When the base plate 7 is made of a conductive material, preheating can be performed using the induction heating coil 8. In order to start modeling of the first layer while maintaining the base plate 7 at a constant temperature, it is desirable that the upper surface of the base plate 7 is preheated at a height substantially coincident with the upper surface of the modeling table 4. However, when the induction heating coil 8 is used for preheating, the lower component of the modeling stage may also generate heat simultaneously with the preheating of the base plate 7. In consideration of this, it is desirable to configure the portion that can enter the inside of the coil during preheating and modeling with the same insulating material as that of the insulator 9 described above.

  Further, the preheating of the base plate 7 may be performed by using a resistance heater provided on the modeling stage without using the induction heating coil 8. In this case, the material of the base plate 7 may be conductive or not. The resistance heater must be provided at a position where it cannot enter the inside of the induction heating coil 8 being energized.

  The temperature control of the base plate 7 is performed using a thermocouple 18 provided in the base plate 7 as a control point. The command temperature for preliminary heating of the base plate 7 may be the same as the command temperature of a modeled object (during modeling) described later. The method for determining the command temperature of the model will be described in detail later.

  For example, assuming that the base plate 7 and the modeling stage adjacent thereto can be oxidized and deteriorated at the preheating temperature, the atmosphere in the chamber is adjusted before the preheating. However, in the case where the temperature can be raised to the preheating temperature even under normal atmosphere, the atmosphere adjustment step and the preheating step may be performed in parallel to shorten the time until the start of modeling. .

  Subsequently, modeling of the first layer is started. In FIG. 1, the powder spreading roller 11 is placed on the left side of the material storage hole, the material supply stage 5 is lifted, and an appropriate amount of material powder is supplied onto the modeling table 4. The supply is performed slightly more than the amount necessary for forming the thin film. The powder spread roller 11 is translated and rotated to the right at a desired speed. In this way, a thin film of material powder is formed on the base plate 7 while conveying the pile of material powder protruding on the supply stage to the right.

  The thickness of the thin film to be formed can be controlled by adjusting in advance the relative height of the modeling stage 6 with respect to the powder spreading roller. The powder spreading roller 11 passes over the base plate 7, and the remaining powder material is poured into the collection container 10. Then, the powder spread roller is translated to the left as it is, and returned to the initial standby position. Further, the film forming stage 6 is slightly raised and then the powder spread roller 11 is returned to the standby position, whereby the thin film formed in the outward path may be crushed or scraped to obtain a desired film thickness. In this case, the powder spread roller 11 is returned to the standby position while rotating.

  During the formation of the thin film, the above preheating for the base plate 7 is not cut off. However, if the dusting roller 11 includes a conductive material and induction heat affects the motion accuracy and thin film formation behavior of the dusting roller 11, the dusting roller 11 is only passing over the induction heating coil 8. Alternatively, the induction heating coil 8 may be controlled so as to cut off the heating current.

  In the above description, the powder spread roller 11 is exemplified as a thin film forming means. However, the thin film formation is not limited to the powder spread roller 11 and can be performed by a scraper or the like.

  Subsequently, the modeling laser is selectively irradiated to the powder thin film formed on the base plate 7. The laser beam obtained from the laser light source 12 is collimated by a collimator lens 13, spread in a band shape by a beam expander 14, and then condensed by a condenser lens 15. The laser beam L is reflected by the mirror of the galvano scanner 16, passes through the f-θ lens 17, is focused on the upper surface of the thin film formed of the material powder 22 as the uppermost layer, and forms a laser spot. The galvano scanner 16 scans the laser spot horizontally within the upper surface of the thin film of the material powder 22 based on a command from a control device described later.

  In order to control this laser spot scanning, the CPU 601 of the control device 600 inputs three-dimensional model data (3D CAD, 3DCG data, etc.) of a model prepared in advance from an external device via the interface 604. Then, the three-dimensional model data is decomposed into layered data of horizontal sections, and further, data of the scan trajectory of the modeling layer corresponding to each layer is generated. Further, the CPU 601 generates drive data for the scanning system, for example, the galvano scanner 16, based on the trajectory data of the modeling layer. The laser scanning optical system is not limited to the above-described configuration. For example, it is conceivable to use a rotational scanning system such as a polygon mirror as needed without being limited to a swing scanning system such as a galvano scanner. In this embodiment, the laser beam (L) is considered as the energy beam. However, when another energy beam such as an electron beam is used for radiant heating of the material powder 22, the generation source and the scanning system are not affected. It may be changed appropriately by a trader.

  As described above, while the laser beam is scanned and the thin film is sintered, the induction heating coil 8 continues to heat the base plate 7 and the modeled object in the present embodiment.

  When the sintering of the first layer is completed, the modeling stage 6 is lowered by the desired film thickness of the second layer, and the material supply and thin film formation of the second layer are performed in the same manner as the first layer. In addition, in order to shorten modeling time, you may perform the part which can be performed among material supply processes in parallel during modeling of the 1st layer.

  Thereafter, the second and higher layers are similarly modeled. In this embodiment, the induction heating coil 8 always keeps heating during modeling, and keeps the temperature of the modeled object O at a desired temperature. The temperature management by the induction heating coil 8 from the modeling initial stage to the modeling end will be described in detail later.

  When the modeling is completed, the temperature of the model O is started to be lowered while the atmosphere of the modeling chamber 1 is maintained. For example, the energization of the induction heating coil 8 is cut off, and the molded article O or its surroundings is cooled to a temperature at which the operator can work. During this temperature decrease, the control device 600 can continuously monitor the temperature of the shaped object (or its surroundings) using the thermocouples 18 and 20 and the radiation thermometer. Then, when the temperature is lowered to a temperature at which problems such as oxidation and deterioration of the modeled object do not occur, the adjustment of the atmosphere is stopped and the atmosphere is introduced into the modeled chamber 1. After the temperature lowering is finished, the control device 600 raises the modeling stage 6 and causes the modeled object to stick out on the modeling table 4.

  The operator accesses the inside of the chamber through the work window, removes the material powder around the modeled object, and removes the modeled object O on the base plate 7 from the modeled stage 6. In addition, the operator cleans the material powder scattered in the modeling chamber 1 and takes out the material powder (22) from the collection container 10 as necessary, thereby completing the modeling operation. Then, the final shaped product (molding) is obtained through the removal processing of the material powder adhered to the shaped product O, the heat treatment of the shaped product O, the removal processing of the base plate 7 and the additional processing of the shaped product O as necessary.

  Here, in this embodiment, the base plate 7 and the material of the modeled object that are suitable will be described in detail. The material of the base plate 7 is required to be able to be bonded to the modeling material, and the melting point is sufficiently higher than the temperature at which the diffusion bonding of the modeling material occurs. Further, when the base plate 7 is preheated, when the induction heating coil 8 is used for induction heating, the base plate 7 also needs to be made of a conductive material.

  When the bonding force between the base plate 7 and the modeled object is too weak, a crack may occur between the plate and the modeled object before the residual stress generated during the modeling is relaxed. Further, if the rigidity and fastening force of the base plate 7 are too low, warping and distortion may occur during modeling before the residual stress is alleviated. Therefore, it is necessary to select a plate material, a plate thickness, and a fastening torque that can obtain a joining force and rigidity sufficient to withstand a temporary residual stress during modeling. In order to make it easy to determine the conditions for joining the base plate 7 and the first layer and to secure a certain degree of joining force, it is desirable to use the same material as the modeled material for the plate material. Since the thermal conductivity and melting point are the same as the modeling material, it is possible to join under the same sintering conditions as sintering the modeled object, and the modeled object does not generate cracks due to thermal expansion differences at the joint. Similar strength can be expected.

  Next, selection of the modeling material (material powder 22) suitable for this embodiment is demonstrated. In this embodiment, the induction heating coil 8 is energized and driven with an alternating current, an alternating magnetic field is generated in the modeling area (hole 6a), and only the modeled object O is selectively induced to generate heat.

  That is, in the present embodiment, the eddy current loop generated in the powdered material powder 22 around the model O is sufficiently small compared to the eddy current loop generated in the model (solidified) model O, Compared with the molded article O, the powder material powder 22 is based on the phenomenon that almost no heat is generated. Since this phenomenon becomes more prominent as the size of the generated eddy current loop varies, it is desirable that the powder of the modeling material has a small eddy current loop, that is, a small particle size. Specifically, those having an average particle size of 10 μm or less are preferably used.

  On the other hand, in addition to the above-described eddy current loss, induction heat generated by an alternating magnetic field is known to be due to hysteresis loss based on the magnetism of the material. This hysteresis loss occurs uniformly in both the shaped article O and the material powder 22.

  In the present embodiment, it is desirable that the part of the shaped object O that has already been shaped is induction-heated, and the material powder 22 that is not solidified in the modeling area (hole 6a) is not induction-heated. Therefore, in consideration of the fact that hysteresis loss occurs uniformly in both the shaped object O and the unshaped material powder 22, it is desirable that the material powder 22 is not magnetized. However, if the frequency of the alternating magnetic field is increased, the amount of heat generated by the eddy current loss can be made dominant over the hysteresis loss. Therefore, by increasing the frequency of the alternating magnetic field applied by the induction heating coil 8, the present embodiment can be implemented even with the material powder 22 made of a magnetic material.

  In the present embodiment, the purpose of arranging the induction heating coil 8 is to heat the modeling object (O) that is modeled from the conductive material powder 22 that exists in the modeling area (inside the hole 6a) during the modeling period. It is to carry out temperature management. As described above, if the temperature control of the modeled object (O) is not performed, for example, the laser-irradiated portion rapidly expands, and then is cooled and contracted, thereby forming the modeled object (O) inside. Residual stress occurs. In particular, when the modeled object (O) is taken out from the modeled area (inside the hole 6a) or the base plate 7 is removed, the residual stress during modeling is released, and the modeled object (O) is warped or distorted. Defects may occur.

  In the present embodiment, in order to prevent deformation and shape defects of the modeled object (O) taken out after such modeling, in particular, temperature management for heating (or keeping warm) the modeled object (O) by the induction heating coil 8 is performed. . However, the induction heating by the induction heating coil 8 acts not only on the shaped object (O) already formed in the modeling area (inside the hole 6a) but also on the material powder 22 made of the same material.

  Therefore, when performing temperature management for heating (or keeping warm) the shaped object (O) by the induction heating coil 8, for example, conditions for heating the shaped object (O) and the material powder 22 in the modeling area (hole 6a), For example, it is necessary to previously determine the upper limit temperature of heating by experiment. This is because, if excessive heating is performed, the surroundings of the shaped object (O) that has already been formed, the material powders 22 that do not need to be solidified for modeling, or between the shaped object (O) and the surrounding material powder 22 are formed. This is because diffusion bonding (melting in the case of suspicion) may occur.

  The definition and determination method of the command temperature of the modeled object (O) being modeled and the “diffusion bonding boundary temperature” serving as a reference for temperature management of the side surface of the modeled area (hole 6a) being modeled will be described below.

  In the case of material powders used in powder bed fusion bonding, such as iron-based alloy materials, even if the melting point is not reached, a phenomenon in which adjacent grains are joined to each other can be maintained by maintaining the temperature above a certain temperature for a long time. This is caused by the movement of atoms constituting the grain so as to reduce the surface area of the grain. In this way, coarsening proceeds and particles that have become too large cannot be used for forming a thin film, and therefore cannot be reused as a modeling material. Moreover, even if it is not between grains, such joining can occur. If the molding material powder in the modeling area is in contact with the wall surface of the modeling apparatus in a high temperature state, the material powder adheres to the wall surface, making it difficult to take out the modeled object and maintaining the apparatus wall surface every time modeling is performed. Occurs. Therefore, it is desirable that the unshaped material powder in the modeling area be kept at a low temperature at which such diffusion bonding does not occur. For this reason, it is necessary to grasp in advance the temperature at which diffusion bonding can occur.

  In order to grasp the upper limit temperature at which diffusion bonding occurs, it is preferable to conduct an experiment in which the material powder used for modeling is heated and the presence or absence of diffusion bonding is confirmed. FIG. 2 shows a test vessel 21 used for this diffusion bonding experiment.

  FIG. 2 shows a state in which the material powder 22 is accommodated in the test container 21. The test container 21 is made of, for example, a material for which diffusion bonding with the material powder is to be confirmed. If it is desired to confirm the fixation of the modeled object with the material powder, the material is the same as that of the modeled object.

  The mass of the material powder 22 in the container can be grasped from the difference in weight of the test container 21 before and after the material powder 22 is charged into the test container 21. The lid 23 of the test container functions as a weight (ballast) that prevents the material powder 22 from scattering and prevents the filling state of the material powder 22 from changing greatly. Moreover, the test container 21 and the lid | cover 23 are made into the fitting structure of clearance fitting, for example, and it designs so that the volume inside the test container 21 can be known by measuring the insertion length of the lid | cover 23 with respect to the test container 21. FIG.

  With the configuration as described above, the volume of the test container 21 and the mass of the material powder 22 that has been charged can be acquired. Further, the filling rate of the powder in the container can be calculated from the density of the modeling material constituting the material powder 22. In general, the higher the powder filling rate, the lower the temperature required for diffusion bonding and the shorter the time. In this experiment, the filling density (pressure) can be controlled by managing the filling of the material powder 22 into the test container 21 uniformly.

  When determining the temperature management conditions of the test container 21 and the material powder 22 as shown in FIG. 2, it is desirable to perform evaluation with a high filling rate in order to reliably suppress diffusion bonding in actual modeling. As the powder filling rate, for example, it is desirable to obtain and evaluate a value corresponding to the tap density.

  The purpose of the experiment shown in FIG. 2 is to set, for example, the material powder 22 itself or a heating temperature standard that does not cause diffusion bonding between the material powder 22 and the test vessel 21 (for example, “diffusion bonding boundary temperature” described below). There is to ask.

  However, the conditions for the diffusion bonding of the material powder (22) are closely related not only to the temperature but also to the heating time (predicted total modeling time in the apparatus of FIG. 1) and the filling density (pressure). For example, even if the heating temperature is the same, diffusion bonding of the material powder 22 may or may not occur depending on the value of the heating time (predicted total modeling time in the apparatus of FIG. 1) and the filling density (pressure). The modeling time of a certain model can be quantitatively predicted from the number of layers of the model, the scanning distance and speed of the laser in each layer, and the thin film formation time per layer.

  Therefore, in this experiment, using the same heating time (predicted total modeling time) and filling density (pressure) conditions as in the apparatus of FIG. 1, “diffusion bonding of the material powder 22 cannot occur within the predicted total modeling time. The “diffusion junction boundary temperature”, which is the “maximum temperature”, is obtained. That is, the “diffusion bonding boundary temperature” in the present invention is defined as “the upper limit temperature at which diffusion bonding of the material powder 22 cannot occur within the predicted total modeling time”. That is, this “diffusion bonding boundary temperature” is within the range of the heating time (predicted total modeling time in the apparatus of FIG. 1) or a specific filling density (pressure), and even if heating is continued at that temperature, the material powder 22 The temperature at which no diffusion bonding occurs.

  In order to obtain the “diffusion bonding boundary temperature” used for temperature management of the test container 21 and the material powder 22, for example, the test container 21 containing the material powder 22 can be controlled at the same temperature as the modeling chamber 1 of FIG. Put in the furnace. And in the atmosphere similar to the actual modeling in the apparatus of FIG. 1, the heating time and the heating temperature are variously changed, and the relationship between the temperature and time at which diffusion bonding occurs is evaluated.

  Here, the criterion of “whether or not diffusion bonding occurs” may be adjusted to a level required for operation. If only the fixation of the apparatus wall surface and the material in the modeling area is a problem, it is only necessary to visually determine whether the test container and the material powder are fixed. On the other hand, if the reuse of the modeling material is considered, it is necessary to determine whether or not the material can be reused by measuring the particle size distribution of the powder after heating or measuring the residual oxygen concentration.

  By performing the experiment as described above, the above “diffusion bonding boundary temperature” that satisfies the same heating time (predicted total modeling time) and filling density (pressure) as in the apparatus of FIG. 1 can be obtained.

  Here, regarding the original purpose of suppressing the residual stress accumulation of the modeled object, the temperature of the modeled object during modeling (or already modeled) can be determined based on the above “diffusion bonding boundary temperature”. For example, according to the inventor's experiment, the heating temperature of the molded article is preferably higher than the “diffusion bonding boundary temperature”, for example, by about 50 ° C. to 100 ° C. higher than the “diffusion bonding boundary temperature” obtained by the above experiment. It was found that it can be used for.

  In other words, in the present embodiment, the modeling object command temperature of the modeling object by the induction heating coil 8 is determined based on the “diffusion bonding boundary temperature” obtained by the above experiment, for example, the above range (50 ° C. to 100 ° C.). High temperature value. Here, the article command temperature is a control amount for controlling the induction heating coil 8 based on the temperatures detected at the control points (temperature detection positions) by the radiation thermometer 19 and the thermocouples 18 and 20. Equivalent to.

  Such temperature management control makes it possible to relieve the residual stress in the model during modeling, but if the temperature is too high, there is an adverse effect that the modeling material adheres to the model. Based on the “diffusion bonding boundary temperature” obtained by experiments, the extent to which the heating temperature (heating upper limit temperature) of the molded article is to be obtained may be determined by a person skilled in the art after confirming each experiment.

  On the other hand, it is needless to say that the material powder 22 in the modeling area (hole 6a) should be managed at a temperature lower than, for example, the “diffusion bonding boundary temperature” in the inner surface area of the modeling area. . Regarding the unsintered (unshaped) material powder 22 in the region of the inner side surface of the modeling area, there is no particular adverse effect due to the low temperature. Therefore, the lower the temperature, the more desirable and positively from the side of the modeling area (hole 6a). It is desirable to cool. In the present embodiment, the inner surface of the modeling area (hole 6a) and the material powder 22 inside thereof can be positively cooled by circulation of the refrigerant inside the induction heating coil 8.

  Further, by controlling the temperature of the inner surface of the modeling area (hole 6a) and the unmolded material powder 22 inside the modeling area (hole 6a), for example, lower than the above-mentioned “diffusion bonding boundary temperature”, an unsintered (unshaped) material The effect of shortening the temperature-falling process after the completion of recycling and molding can be expected.

  Next, in the present embodiment, the configuration of the modeling stage 6, the induction heating coil 8, the insulator 9, and the temperature detection means that are considered suitable will be described.

  FIG. 3 schematically shows a cross section in the vicinity of a modeling area (hole 6a: FIG. 1) during modeling of the first layer. In the figure, the induction heating coil 8 is divided into three upper, middle, and lower heating zones in the vertical direction, and output control can be performed based on each desired control point temperature. The induction heating coils 8 are each formed of, for example, a spiral copper pipe, and the refrigerant (cooling water) is circulated therein as described above. The induction heating coil 8 is embedded in the insulator 9. As a material of the insulator 9, an insulating ceramic material having high strength even at a high temperature, particularly aluminum nitride or silicon nitride resistant to thermal shock is preferably used. Since the heating efficiency improves as the distance between the induction heating coil 8 and the modeled object O becomes shorter, it is desirable to provide the induction heating coil 8 on the inner diameter side of the insulator 9.

  On the other hand, in order to suppress the heat generation at the modeling table 4, the insulation heating coil 8 and the modeling table 4 are arranged at a distance in the cross section of the insulator 9. Thus, by burying the induction heating coil 8 in the insulator 9, the induction heating coil 8 can also function as a cooling pipe on the side surface of the modeling area, and the powder material on the side surface can be actively cooled. In addition, as a material of the insulator 9, a thing with high heat conductivity is desirable, and aluminum nitride etc. are suitable.

  In the modeling stage 6, it is desirable that the mounting portion of the base plate 7 and the structural member immediately below the base plate 7 are made of an insulator so as not to generate heat during modeling (details not shown). As the insulator material, aluminum nitride, silicon nitride, or the like is preferably used for the insulator at this portion.

  Next, temperature detection means for each part will be described. How to use each detected temperature during modeling will be described later. As described above, the radiation thermometer 19 that measures the upper surface temperature of the modeled object being modeled is disposed above the modeled area (hole 6a). The measurement points of the radiation thermometer 19 are preferably a plurality of points on the upper surface of the modeled object, and ideally the surface temperature distribution can be measured on the surface. Of course, the housing of the radiation thermometer 19 is installed outside the region through which the modeling laser can pass. The radiation thermometer 19 is provided with a filter for cutting the wavelength of the modeling laser.

  At the time of modeling, it is desirable to calibrate the emissivities of the modeled object O and the material powder 22 with the radiation thermometer 19 in advance. The top surface temperature measurement during modeling is performed, for example, at least twice for each layer, immediately before and after the sintering step. In the temperature measurement of the thin film on the modeling object O immediately before the one-layer sintering process, the measurement is performed on the assumption that the thin film temperature immediately above the modeling object of the previous layer is equivalent to the upper surface temperature of the modeling object. In addition, immediately after the sintering process of one layer, the upper surface of the shaped object O is measured as it is. In this case, for example, an in-plane average temperature measured by the radiation thermometer 19 is used as the detection temperature.

  Moreover, in order to measure the temperature of the lowest part of the molded article O, the thermocouple 18 provided in the base plate 7 is arrange | positioned. For example, by making the material of the base plate 7 and the material of the model O the same, the temperature of the base plate 7 detected by the thermocouple 18 can be measured as the bottom surface temperature of the model. The arrangement position of the thermocouple 18 is desirably directly below the lowermost surface of the molded article O. In addition, when the area of the lowermost surface of the molded article O is large, it is desirable to provide a plurality of thermocouples in the plane where the modeling is performed. As the thermocouple 18, a sheath thermocouple insulated from the base plate 7 can be used. Here, in order to suppress self-heating of the thermocouple 18, an excessively thick thermocouple is not desirable, and a sheath diameter of about 0.2 mm to 1 mm is preferably used.

  Further, as described above, the thermocouple 20 is disposed at a position close to the inner surface of the insulator 9 in order to detect the inner surface of the modeling area (hole 6a) or the temperature of the material powder 22 particularly in the vicinity of this portion. ing. The position of the tip (detection end) of the thermocouple 20 is preferably closer to the inner wall surface of the modeling area (hole 6a). In addition, it is desirable that at least one thermocouple 20 is arranged independently for each of the heating zones so that the temperatures corresponding to the upper, middle, and lower three heating zones of the induction heating coil 8 can be measured. The detected temperature in each heating zone is the average temperature of a plurality of thermocouples provided in the zone. Moreover, it is desirable to provide a plurality of thermocouples 20 at the same height and equally spaced in the circumferential direction of the modeling area (hole 6a). Also for these thermocouples 20, sheath thermocouples having a sheath diameter of about 0.2 mm to 1 mm can be suitably used.

  Then, the temperature control method in each step during modeling is shown. 3-6 has shown the mode of modeling when the molded article O was divided | segmented and considered as an area | region of three heights, an upper layer, a middle layer, and a lower layer. 3 corresponds to a state in which the first layer of the lowermost layer of the modeled object O is modeled, and FIG. 4 corresponds to a state in which the modeling of the lower layer of the modeled object O is completed. FIG. 5 corresponds to a state in which the middle layer of the model O is finished, and FIG. 6 corresponds to a state in which the upper layer of the model O is finished.

  4 to 6 are shown in conformity with FIG. 3 described above, and each part and the relationship between them and reference numerals are the same as those in FIG. According to the configuration of FIG. 1, modeling (single layer sintering) by the laser beam L is performed on the uppermost layer of the modeling area (hole 6a). O is modeled in the order of the lower layer, the middle layer, and the upper layer, and descends in the modeling area by the modeling stage 6.

  FIG. 7 shows each stage of modeling of the lower layer, middle layer, and upper layer of the modeled article O, and control command values and control points (temperature detection positions) of the upper (part), middle (part), and lower (part) heating zones. Shows the relationship. In FIG. 7, reference numerals 701, 702, and 703 respectively denote control command values and control points (temperature detection positions) of the upper (part), middle (part), and lower (part) heating zones. Reference numerals 704, 705, and 706 correspond to the respective stages of modeling of the lower layer, the middle layer, and the upper layer of the modeled object O, respectively.

  As shown in FIG. 7, the induction heating coil 8 uses only the upper heating zone in the modeling of the lower layer of the modeled article O from FIG. 3 to FIG. 4 (section 704 in FIG. 7). Further, as the modeled object command temperature, a modeled object command temperature determined in advance as described above based on the “diffusion bonding boundary temperature” can be used. Further, as the control point (temperature detection position), the upper surface of the modeled object that is a measurement point by the radiation thermometer 19 may be adopted, or the lower surface of the modeled object O (the measurement point of the thermocouple 18) may be used. Here, the CPU 601 of the control device 600 gives a driving amount corresponding to the modeled object command temperature to the induction heating coil 8 in the upper heating zone, and heats the modeled object O.

  In the formation of the middle layer from FIG. 4 to FIG. 5 (the section 705 in FIG. 7), the induction heating coil uses two zones, the upper part and the middle part (701, 702). As the control point of the upper heating zone, the upper surface of the modeled object (measurement point of the radiation thermometer 19) is used. Moreover, the lower surface (measurement point of the thermocouple 18) of the molded article O is used as a control point of the middle heating zone.

  Further, in the upper layer modeling from FIG. 5 to FIG. 6 (section 706 in FIG. 7), the induction heating coil 8 uses all of the upper, middle, and lower heating zones (701, 702, 703). . The upper surface of the modeled object (measurement point of the radiation thermometer 19) is used as the control point of the upper heating zone, and the lower surface of the modeled object (measurement point of the thermocouple 18) is used as the control point of the lower heating zone. Further, for the middle heating zone, the temperature of the material on the side surface is detected and controlled because the temperature of the molded article cannot be directly detected. The average value of the material temperature on the side surfaces in the upper and lower heating zones is set as a command temperature, and the inner surface of the modeling area (measurement point of the thermocouple 20) is controlled as a control point.

  Here, in the modeling of the middle layer or the upper layer of the molded article O (FIGS. 4 to 6), the CPU 601 of the control device 600 performs temperature management for determining the output value of the induction heating coil 8 according to the procedure shown in FIG. be able to. FIG. 8 shows details of the control particularly when the upper surface temperature of the molded article O is used as a control point.

  The temperature management control in FIG. 8 is for maintaining the temperature of the shaped object O that has been shaped at a constant target shaped object command temperature (807) determined based on the “diffusion bonding boundary temperature”. In the control using the upper surface temperature of the modeled object O as a control point as shown in FIG. 8, the control cycle is set for each layer in order to determine the heating output for each layer. For example, there is a possibility that the temperature and area of the top surface of the object to be measured will fluctuate greatly during one layer of sintering and subsequent thin film formation, and the temperature measurement is fed back to the drive of the induction heating coil 8 in real time. It is difficult to let Therefore, in the control of FIG. 8, the temperature of the upper surface is determined using immediately before sintering considered to be the lowest temperature and immediately after sintering considered to be the highest temperature in the formation of one layer.

  The temperature management control in FIG. 8 is such that a heating control amount by the induction heating coil 8 in modeling a certain layer, for example, N layer, is performed based on temperature measurement in modeling the previous layer, for example, N−1 layer. That is, before the N-1 layer is sintered, the CPU 601 of the control device 600 uses the radiation thermometer 19 to measure the temperature (801) immediately before sintering (considered to be the lowest temperature during the formation of the N-1 layer). Let it be done. In addition, after the sintering of the N-1 layer, the radiation thermometer 19 causes the temperature measurement (802) immediately after the sintering (which is considered to be the highest temperature during the formation of the N-1 layer) to be performed.

  Then, the CPU 601 calculates a representative value of the upper surface temperature of the N-1 layer from the measured values of the temperature measurement immediately before sintering (801) and the temperature measurement immediately after sintering (802) using an appropriate calculation method ( 803). Moreover, the effect (temperature change) of the heating by the N-1 layer induction heating coil 8 can be evaluated by calculating the temperature deviation (804) of the temperature measurement (801, 802) immediately before and immediately after the sintering. .

  Then, the CPU 601 uses the representative value (803) of the upper surface temperature of the N-1 layer and the temperature deviation (804) immediately before and immediately after the sintering of the N-1 layer, and continues to form the N layer by an appropriate calculation method. The drive control amount of the induction heating coil 8 is acquired (805). Thereafter, the induction heating coil 8 during the modeling of the N layer is driven using the acquired drive control amount (805), and the modeled object O is heated (insulated) (806). Note that an example of a method for calculating the drive control amount (or command temperature) of the induction heating coil 8 based on temperature detection of a plurality of heating zones is shown as Embodiment 2 (FIG. 9).

  As described above, in the present embodiment, temperature management control of the modeled object O is performed through induction heating of the induction heating coil 8, and the temperature of the modeled model O is based on the above-described “diffusion bonding boundary temperature”. The temperature is controlled to the determined fixed object command temperature. Therefore, the residual stress during the modeling period of the modeled object O is alleviated, and the modeled object (O) that may be generated when the modeled object O is taken out from the modeled area (inside the hole 6a) or the base plate 7 is removed. Can be satisfactorily suppressed. Moreover, the temperature difference of the vertical direction of a molded article can be suppressed by heating thru | or keeping the whole molded article (O) during a modeling period, and the shape defect resulting from the temperature distribution during modeling can be suppressed.

  In this case, in the present embodiment, the article command temperature is determined based on the “diffusion bonding boundary temperature” obtained in advance by experiments (FIG. 2) as described above. For this reason, accurate three-dimensional modeling without causing inadvertent adhesion between the modeled object (O) and the unshaped material powder 22, alteration of the unshaped material powder 22, and adhesion to the inner wall surface of the modeling area. Is possible.

  When performing control using the object temperature as a control point as described above, the material temperature on the inner surface of the modeling area exceeds the diffusion bonding boundary temperature in a configuration where the cooling capacity of the inner surface of the modeling area is insufficient. There is a possibility that. Therefore, the temperature management control by the CPU 601 incorporates a routine for switching the control method when the temperature of the inner surface (material powder) of the modeling area measured through the thermocouple 20 or the like exceeds the diffusion bonding boundary temperature. It is desirable to leave in.

  For example, in the control method switching performed when the temperature of the inner surface (material powder) of the modeling area exceeds the diffusion bonding boundary temperature, it is conceivable that the model command temperature is lowered. For example, it is possible to lower the molded article command temperature to the “diffusion bonding boundary temperature” itself obtained by an experiment from the value obtained by adding a margin of about 50 ° C. to 100 ° C. to the above “diffusion bonding boundary temperature”. Conceivable. Further, in this control method switching, it is desirable to switch to a control method in which the control point (temperature detection or temperature management position) is the inner surface of the modeling area and the temperature of the material powder on the inner surface of the modeling area is directly managed.

  In addition, in this embodiment, although the case where it modeled to the limit of the modelable height of an apparatus is demonstrated, this invention is applicable also to a molded article with low height. In such a case, the number of zones of the induction heating coil used for heating during modeling is reduced according to the height of the modeled object.

<Embodiment 2>
In the above, a configuration has been described in which a plurality of induction heating coils that can be independently controlled to be energized are arranged in the three heating zones above, inside, and below the outer peripheral portion of the modeling area (hole 6a). However, the number of heating zones is preferably at least two zones in the vertical direction, or the larger the number of heating zones, the more desirable. In that case, it is difficult to detect the temperature of the molded object itself in an intermediate heating zone other than the uppermost and lowermost heating zones, and the temperature of the temperature of the side surface of the modeling area (hole 6a) (or the material powder in the vicinity thereof) is controlled. It will be used for control.

  FIG. 9 shows an example of determining command values for heating zones other than the uppermost part and the lowermost part in a configuration in which five heating zones are arranged in the vertical direction in the modeling area (hole 6a) of the modeling apparatus of FIG. In the schematic illustration of the modeling area (hole 6a) shown at the left end of FIG. 9, there is a (modeled) modeled object O, and (unmolded) material powder 32 surrounds it. In addition, the other structure of the modeling apparatus shall be the same as that of the above-mentioned Embodiment 1.

  In the example of FIG. 9, five thermocouples 31 are arranged in the five heating zones in order to detect the temperature of the inner wall surface of the modeling area or the material powder 32 facing it. In FIG. 9, 33 shows a plot of the material temperature detection result of each zone in the N-1th control cycle. In this example, the plot (33) of the material temperature detection result of each zone does not change gently from the lower layer to the upper layer. In actual modeling, as described above, the plot (33) of the material temperature detection result is not dependent on the amount of heat stored in the area (volume of the layer) of each modeling layer corresponding to the shape of the modeled object O. Linearity can occur.

  In consideration of the occurrence of nonlinearity in the plot (33) of the material temperature detection result in this way, the command temperature of each heating zone is determined from the material temperature detection results obtained from a plurality (five in this example) of thermocouples 31. The following calculation methods can be considered to determine the value.

  In FIG. 9, 34 is determined based on the temperatures detected in the uppermost and lowermost zones among the temperature detection zones of the five thermocouples 31 based on the N-1th temperature detection result (33). It corresponds to an approximate line that connects the command temperature values linearly. The CPU 601 of the control device 600 can obtain an approximate line (34) in which the command temperature values obtained in the uppermost and lowermost zones of the detection zone of the thermocouple 31 are connected in a straight line. Further, the CPU 601 can acquire a command temperature value at a position corresponding to the height of the three intermediate temperature detection zones by using the approximate line (34) and, for example, the distance between the zones. That is, in this embodiment, as shown in FIG. 9, the temperature distribution in the vertical direction on the side surface is gently connected with reference to the material temperatures detected by the thermocouples 31 arranged in the uppermost and lowermost heating (temperature detection) zones. The command temperature of each heating (temperature detection) zone is set.

  In addition, although the suitable thing of the frequency of the alternating current sent through the induction heating coil 8 changes according to the material and shape of a molded article, there exists a merit according to the height of a frequency, respectively. In the case of increasing the frequency, as described above, there is a possibility that the present invention can be applied to the magnetic material. On the other hand, the merit of lowering the frequency is that the heat generation region generated in the skin of the model becomes deeper than the high frequency. When the temperature in the vicinity of the skin of the modeled object decreases, more uniform modeled object heating can be realized. Moreover, there exists an advantage that the adhering to the molded article of material powder can be suppressed because the temperature of the skin vicinity falls. Considering the above, for example, when SUS316L, which is a non-magnetic material, is used as a modeling material, it is considered that an AC frequency for energizing the induction heating coil 8 is preferably about 150 kHz to 400 kHz, for example.

<Embodiment 3>
In Embodiment 1 described above, the hollow induction heating coil also serves as a cooling pipe (cooling device or cooling means) for the inner wall portion of the modeling area. However, these two functions of induction heating and cooling may be separated into different configurations. For example, as shown in FIG. 10, the structure which arrange | positions a cooling water path (cooling piping) separately from these induction heating coils can also be considered. FIG. 10 shows an example of a cross-sectional structure in the vicinity of the modeling table 4, and other configurations are the same as those in the first embodiment (or the second embodiment). In addition, in FIG. 10, the state which has the modeling stage 6 and the baseplate 7 in the highest position is illustrated.

  In the example of FIG. 10, the cooling water channel 36 is disposed in the insulator 25, and the induction heating coil 37 (corresponding to the induction heating coil 8) is disposed in the space defined outside the insulator 25. Yes. In addition, a top plate 38 is disposed above the space where the induction heating coil 37 is disposed in order to shield the material powder 22 from flowing into the space where the induction heating coil 37 is disposed. The cooling water channel 36 can be formed, for example, by performing groove processing on the insulator 25, and it is not necessary to use a conductive material for this portion. The induction heating coil 37 is supported in a non-contact manner with the surrounding insulator 25 and the modeling table.

  Even in such a configuration, the induction heating coil 37 is preferably made of a hollow material, and cooling water is circulated inside the induction heating coil 37 in the same manner as described above in order to cool the coil itself. The top plate 38 can be made of the same insulating material as the insulator 25.

  According to the configuration example as shown in FIG. 10, it is not necessary to embed an induction heating coil in the insulator 25, and it becomes easy to manufacture a portion of the insulator 25. Moreover, the part of the insulator 25 can be constituted by a combination of inexpensive plate-like members instead of an integral part that covers the entire side surface of the modeling area. Further, since the induction heating coil 37 is not embedded, problems such as deformation and breakage of the insulator 25 due to a difference in thermal expansion between the coil and the insulator 25 need not be considered.

  However, in the configuration of FIG. 10, on the other hand, the distance between the induction heating coil 37 and the shaped object tends to be large, and the heating efficiency may be reduced. For this reason, in the structure of FIG. 10, the energization energy of the induction heating coil 37 may become large for desired heating control. In addition, if the top plate 38 is configured to withstand the vertical load from the powder spread roller, the uppermost end position of the coil becomes lower than the upper end of the modeled object, and as a result, it may be difficult to heat the upper surface of the modeled object.

  The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program. It can also be realized by processing. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

<Example 1>
Below, the modeling apparatus based on the structure illustrated by said each embodiment WHEREIN: The result of having modeled the three-dimensional molded item in the control procedure shown in FIG. 7 is illustrated. The modeling control conditions in this example were as follows.

  The inside of the modeling chamber is purged with nitrogen at normal temperature and normal pressure so that the oxygen concentration is 300 ppm or less.

  The size of the modeling stage is a square shape of 144 mm × 144 mm, and the base plate 7 is the same. Aluminum nitride is used as the material for the mounting plate of the modeling stage. As a material for the base plate 7, SUS316L having a thickness of 10 mm was selected. The base plate 7 was fastened with eight M5 screws, and each fastening torque was 5 Nm.

  As the modeling material (material powder 22), SUS316L having an average particle diameter of about 7 μm was used. Through the modeling, the thickness of the thin film formed by the powder spreading roller 11 is 40 μm. In addition, as the induction heating coil 8, for example, a spiral shape of about 3 turns and a height of about 35 mm is arranged in the upper, middle, and lower three heating zones as shown in FIG. 1. An AC power source that generates a high frequency for driving the induction heating coil 8 is one that can perform auto-matching in the range of 150 kHz to 400 kHz, and the driving frequency during modeling is in the range of 200 to 300 kHz.

  As the thermocouple for temperature detection, a 0.5 mm diameter SUS sheath and an ungrounded K thermocouple were used. Further, a thermoviewer having a detection wavelength half width of 8 to 15 mm was used for the radiation thermometer 19 for measuring the temperature of the upper surface of the modeling area, and the detected temperature was obtained by averaging the area from the surface measurement data.

The design height of the modeled object modeled in this example was 103 mm, the design volume was 1046 cm ³ , and the predicted total modeling time was 9 hours and 40 minutes. The insulator 9 was made of aluminum nitride.

  Further, the above-mentioned “diffusion bonding boundary temperature” was 450 ° C. by performing an experiment with the technique shown in FIG. 2 using a modeling material (material powder 22) having an average particle diameter of SUS316L of about 7 μm. . Then, based on the temperature detection of the upper surface and the lower surface, the command temperature of the modeling object (O) during modeling whose temperature is controlled by driving the induction heating coil 8 was set to 500 ° C. A Yb fiber laser having a wavelength of 1070 nm was used for the laser light source 12 as a modeling laser, and an average laser output during sintering of one layer was 40 W. During modeling, the modeling area (hole 6a) is simultaneously cooled by the refrigerant circulation of the hollow induction heating coil 8 described in the first embodiment, for example. Throughout the modeling, the temperature (the temperature of the material powder 22) detected via the thermocouple 18 on the side surface of the modeling area (hole 6a) could be kept below the diffusion bonding boundary temperature.

  After completion of the modeling under the control conditions as described above, the material powder 22 did not adhere to the inner wall surface (insulator 9) of the modeling area (hole 6a), but a part of the upper surface of the base plate 7 and the lower layer of the modeled object Some sticking was seen between the parts.

  The material supply stage 5 was raised to remove the material powder 22 around the modeled object (O). However, the material powder 22 was not fixed to the modeled object (O) modeled in the desired shape.

  Then, in order to evaluate the deformation | transformation of a molded article (O), the molded article (O) was removed from the baseplate 7, and the curvature shape was measured using the horizontal upper surface part of the molded article (O). In this example, the horizontal upper surface portion of the shaped object (O) has a concave warpage shape, and the maximum warpage amount (depth of the concave surface) is recognized to be about 27 μm with respect to the in-plane length of 100 mm. . On the other hand, only the preliminary heating of the base plate 7 and the induction heating of the modeled object (O) by the induction heating coil 8 were omitted, and the maximum warpage amount of the modeled object (O) modeled under the same modeling conditions was 85 μm.

  Therefore, according to the present embodiment, due to the preheating of the base plate 7 and the induction heating of the object (O) by the induction heating coil 8, the residual stress is suppressed in the object (O) and the stress is released after the removal. The amount of deformation to be reduced was successfully reduced. According to the present embodiment, the deformation amount of the modeled object (O) is about 1/3 as compared with the case where the preheating of the base plate 7 and the induction heating of the modeled object (O) by the induction heating coil 8 are not performed. The following could be reduced.

  DESCRIPTION OF SYMBOLS 1 ... Modeling chamber, 2 ... Exhaust port, 3 ... Air supply port, 4 ... Modeling table, 5 ... Material supply stage, 6, 27 ... Modeling stage, 7 ... Base plate, 8, 37 ... Induction heating coil, 9 ... Insulator DESCRIPTION OF SYMBOLS 10 ... Recovery container, 11 ... Powder spread roller, 12 ... Laser light source, 13 ... Collimator lens, 14 ... Beam expander, 15 ... Condensing lens, 16 ... Galvano scanner, 17 ... f-theta lens, 18, 20, 29-31 ... thermocouple, 19, 28 ... radiation thermometer, 21 ... test container, 22, 32 ... (unformed) material powder, 23 ... lid, 36 ... cooling channel, 38 ... top plate, 85 ... chiller, 87 ... Sequencer, 601 ... CPU, 602 ... ROM, 603 ... RAM, O ... (modeled) modeled object.

Claims (14)

In a three-dimensional modeling apparatus for manufacturing a three-dimensional structure by repeating a series of operations in which conductive material powder is laid in a modeling area, and a part of the laid material powder is selectively radiantly heated and sintered,
An induction heating coil that is arranged on the outer periphery of the modeling area and induces heat generation of a modeled object inside the modeling area by energization;
A control device for performing temperature management of the shaped article by controlling energization of the induction heating coil;
3D modeling device.   2. The three-dimensional modeling apparatus according to claim 1, wherein the control device is configured to perform the material generation within a predicted total modeling time of the modeled object through energization control of the plurality of induction heating coils during modeling of the modeled object. A three-dimensional modeling apparatus that performs temperature management of the modeled object so as to heat the modeled object to a temperature determined based on a diffusion bonding boundary temperature corresponding to an upper limit temperature at which powder diffusion bonding cannot occur.   3. The three-dimensional modeling apparatus according to claim 1, further comprising a cooling device that is disposed on an outer peripheral portion of the modeling area and can be controlled by the control device, and the control device is configured to perform the modeling via the cooling device. The temperature of the unsintered material powder facing the inner surface of the area is kept below the diffusion bonding boundary temperature corresponding to the upper limit temperature at which the material powder cannot undergo diffusion bonding within the predicted total modeling time of the modeled object A three-dimensional modeling apparatus that performs temperature control of the unsintered material powder.   4. The three-dimensional modeling apparatus according to claim 3, wherein the induction heating coil is made of a hollow material capable of circulating a refrigerant therein, so that the induction heating coil also serves as the cooling device, and the control device. Is a three-dimensional modeling apparatus that controls the temperature of the unsintered material powder by controlling the circulation of the refrigerant inside the induction heating coil.   5. The three-dimensional modeling apparatus according to claim 1, wherein a plurality of the induction heating coils that can be energized and controlled independently are defined at different positions around the modeling area. 6. A three-dimensional modeling apparatus that is disposed in a heating zone, and wherein the control device performs temperature management of each of the heating zones via the plurality of induction heating coils.   The three-dimensional modeling apparatus according to any one of claims 1 to 5, wherein a first temperature measuring device that measures a temperature of an uppermost part of a modeled model inside the modeling area, the interior of the modeling area A second temperature measuring device that measures the temperature of the lowermost part of the shaped article that has been shaped, or a third temperature that detects the temperatures of a plurality of measuring points arranged at different positions around the shaping area, respectively. A three-dimensional modeling apparatus comprising a measuring device, wherein the control device performs temperature management of the modeled object via the induction heating coil based on the temperature measured by the first, second, or third temperature measuring device .   The three-dimensional modeling apparatus according to claim 6, further comprising: a cooling device that is disposed on an outer peripheral portion of the modeling area and that can be controlled by the control device, and the control device has a temperature measured by a third temperature measurement device. Based on this, the three-dimensional modeling apparatus which performs temperature management of the unsintered material powder in a modeling area via the said cooling device.   8. The three-dimensional modeling apparatus according to claim 1, wherein an inner surface of the modeling area is configured by an insulator that separates the induction heating coil from an inner side of the modeling area. Dimensional modeling device.   5. The three-dimensional modeling apparatus according to claim 3, wherein an inner surface of the modeling area is configured by an insulator that separates the cooling device from the inside of the modeling area.   The three-dimensional modeling apparatus according to any one of claims 1 to 9, wherein the material powder formed in the modeling area is selectively radiated and sintered by the energy beam generated by the energy beam irradiation apparatus. 3D modeling device.   The three-dimensional modeling apparatus according to claim 10, wherein the energy beam irradiation apparatus is a laser irradiation apparatus that irradiates a laser beam as the energy beam.   The three-dimensional modeling apparatus according to claim 1, wherein the control apparatus causes the control device to execute any one of the temperatures.   A computer-readable recording medium storing the control program according to claim 12.   The manufacturing method of the three-dimensional structure which shape | molds the said three-dimensional object three-dimensionally using the three-dimensional modeling apparatus of any one of Claim 1 to 11.

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