JP6855181B2 - 3D modeling device and manufacturing method of 3D modeled object - Google Patents

Description

The present invention relates to a three-dimensional modeling apparatus for producing a three-dimensional model by repeating an operation of selectively radiating and heating material powder laid on a modeling stage and sintering it, and a method for manufacturing a three-dimensional model.

Conventionally, in products such as so-called 3D printers, a powder bed melt-bonding technique for modeling a three-dimensional model has been used.

In this powder bed fusion, for example, an energy beam such as a laser beam is used, and the material powder is radiantly heated and sintered layer by layer to form a three-dimensional component (for example, the following patent documents). 1). The first layer made of the material powder is irradiated with a laser beam, the necessary portion is selectively sintered, a second layer of the material powder is subsequently prepared on the first layer, and the laser beam is irradiated in the same manner to form the second layer. It is selectively sintered and joined with the sintered portion of the first layer. After that, the three-dimensional parts are manufactured by repeating the above process for the third and subsequent layers. The laser beam is used as a means for selectively applying heat according to the desired shape of the modeled object, but it is also conceivable to use another energy beam as the means for applying heat.

In the powder bed fusion bond, when the outermost layer of the spot irradiated with the laser beam is sintered, the outermost layer and a part of the sintered structure below it are instantaneously thermally expanded, and then rapidly. Residual stress may be generated near the spot due to cooling shrinkage. In many powder bed melt-bonded modeling devices, the modeled object during modeling is significantly deformed because it is constrained by the rigidity of the base plate to which the first layer is joined and the fastening force that fastens the base plate to the device. There is no. However, after the modeled object is taken out from the device and after the base plate is removed, the stress remaining during the modeling is released, which may cause a shape defect such as warpage or distortion of the modeled object.

In consideration of such shape defects of the 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, the stress remaining on the outermost layer of the final modeled part is considered to be the main cause of the shape defect, and only such a part is reheated during modeling 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 described in Patent Documents 2 and 3 above, since the main amount of heat applied to the modeled object during modeling is limited to the upper part of the modeled object, the temperature in the vertical direction to the modeled object being modeled. Distribution can 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, so the resulting modeled object is warped and distorted. Poor shape may occur.

In view of the above problems, the object of the present invention is to alleviate the residual stress generated in the modeled object in the powder bed melt bonding, and to suppress the shape defect of the modeled object by keeping the temperature distribution of the modeled object uniform. To do.

In one aspect of the present invention, a conductive material powder is laid in a molding area, and a series of operations of selectively radiating and sintering a part of the laid material powder are repeated to manufacture a three-dimensional model. In a three-dimensional modeling apparatus, an induction heating coil arranged on the outer peripheral portion of the modeling area and inducing heat generation of a molded object inside the modeling area by energization, and an induction heating coil arranged on the outer peripheral portion of the modeling area and described above. Three-dimensional modeling including a cooling device for cooling unsintered material powder in the area and a control device for performing temperature control of the modeled object by energizing the induction heating coil and controlling the cooling device. It is a device .

According to the above configuration, by performing temperature control of the modeled object so as to heat or keep the modeled object warm during the modeling period, it is possible to suppress the occurrence of stress residue in the modeled object and release the residual stress after the modeling is completed. It is possible to reduce the shape defects caused by the above and perform highly accurate three-dimensional modeling. By heating or keeping the entire modeled object warm during modeling, the temperature difference in the vertical direction of the modeled object can be suppressed, and shape defects due to the temperature distribution during modeling can be suppressed.

It is a schematic diagram which showed the structural example of the 3D modeling apparatus which can carry out this invention. It is a schematic diagram which showed the structural example of the test container used for the confirmation experiment of the diffusion bonding boundary temperature of a modeling material. It is a schematic diagram which showed the neighborhood of the modeling area in the apparatus of FIG. In the apparatus of FIG. 1, it is a schematic diagram which showed the vicinity of the modeling area at the time of completion of modeling of a lower layer part. In the apparatus of FIG. 1, it is a schematic diagram which showed the vicinity of the modeling area at the time of completion of modeling of a middle layer part. In the apparatus of FIG. 1, it is a schematic diagram which showed the vicinity of the modeling area at the time of completion of modeling of the upper layer part. In the apparatus of FIG. 1, it is a table diagram which showed the control command value and the control point of each heating zone in each stage of modeling. It is explanatory drawing which showed the heating output control at the time of performing the temperature control of the upper surface of a modeled object in the apparatus of FIG. FIG. 5 is an explanatory diagram showing a control example of a control command value in a heating zone other than the uppermost end and the lowermost end of the modeled object in the apparatus of FIG. It is a schematic diagram which showed the structure in the case where the insulator and the induction heating coil are provided independently with respect to 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 a block diagram which showed the structural example of the control system (control device) of the device of FIG.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the examples shown in the accompanying drawings. It should be noted that the examples shown below are merely examples, and for example, those skilled in the art can appropriately change the detailed configuration without departing from the spirit of the present invention. Further, the numerical values taken up in the present embodiment are reference numerical values and do not limit the present invention.

<Embodiment 1>
FIG. 1 shows a configuration example of a three-dimensional modeling apparatus adopting the present invention. The device of FIG. 1 is a three-dimensional modeling device such as a 3D printer, which manufactures a three-dimensional model by repeating the operation of selectively radiating and heating the conductive material powder formed in the modeling area and sintering it. is there.

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

Above the modeling chamber 1 of FIG. 1, a laser irradiation device that irradiates a laser beam L as an energy beam for performing modeling by radiant heating is arranged. This laser irradiation system includes, for example, a laser light source 12, a collimator lens 13, a beam expander 14, a condenser lens 15, a galvano scanner 16, and an f-θ lens 17 for scanning a laser spot on an imaging surface at a constant velocity. It is composed of such as. The galvano scanner 16 is modulated by a control device described later, for example, by a 3DCAD (or 3DCG) signal expressing the shape of the modeled object, and is controlled to scan the laser spot in a horizontal plane into a shape corresponding to one layer of the modeled object. To.

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

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

A material supply stage 5 that can be raised and lowered is arranged inside the hole 5a for storing the material powder. The material supply stage 5 raises the material powder previously stored in the upper part of the hole 5a before modeling, and the powder laying roller 11 can appropriately supply a required amount of the material powder onto the modeling table 4. The material supply stage 5 is configured to be able to move up and down by, for example, an external drive means (for example, a transmission system using a servomotor + rack & pinion (not shown)) of the modeling chamber 1. In the present embodiment, the material powder stored inside the hole 5a is assumed to be a conductive metal material.

Inside the hole 6a for modeling, a modeling stage 6 that can be raised and lowered 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 method such as screwing. The modeling stage 6 is configured to be able to move up and down by, for example, an external drive means of the modeling chamber 1 (for example, a transmission system using a servomotor + rack & pinion (not shown)), and controls described later as the modeling of each layer progresses. The device controls, for example, to descend. Further, a recovery container 10 is arranged in the material recovery hole 10a of the modeling table 4.

In the present embodiment, the spiral induction heating coil 8 is arranged on the peripheral side surface of the hole 6a to be modeled. In the present embodiment, the induction heating coil 8 is used for induction heating the modeled object (O) formed from the metallic material powder (22). Although the induction heating coil 8 is shown only for two turns in FIG. 1 (or FIG. 12), the number of loops of the induction heating coil 8 is arbitrary.

The inner wall of the hole 6a (modeling area) for modeling the modeling table 4 is formed of an insulator 9, and the induction heating coil 8 is embedded in the insulator 9. It is conceivable that the insulator 9 is formed by a method such as coating, drying, or sintering using an insulating ceramic material, particularly a material such as aluminum nitride or silicon nitride which is a material resistant to thermal shock. The induction heating coil 8 and the thermocouple 18 described below can be embedded in the insulator 9 when the insulator 9 is formed. The insulator 9 isolates the induction heating coil 8 (or a cooling device composed of the hollow portion thereof) 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-shaped portion and a lead portion 81. The shape of the induction heating coil 8 is the same for 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 portion 81 is connected to the power supply system (FIG. 11) described later via the power supply lines 82 and 82. Further, the hollow portion of the induction heating coil 8 is connected to a cooling system (FIG. 11) described later, and a refrigerant (for example, cooling water) is supplied, recovered, and circulated as shown by 81a and 81b. By circulating a refrigerant (for example, cooling water) inside the induction heating coil 8 in this way, the insulator 9 on the inner wall of the hole 6a to be modeled is cooled (FIG. 1), and the temperature of this portion is controlled.

In the present embodiment, by controlling the induction heating by the induction heating coil 8 and the circulation of the refrigerant inside the induction heating coil 8 by the control device described later, particularly the modeled 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 control, a radiation thermometer 19 is arranged as a first temperature measuring device for measuring the temperature of the uppermost part of the modeled object (O) in the modeling area (hole 6a). Further, a thermocouple 18 is arranged on the base plate 7 as a second temperature measuring device for measuring the temperature of the lowermost portion of the modeled object (O) in the modeling area (hole 6a).

Further, a thermocouple 20 is arranged as a third temperature measuring device for detecting the temperatures of a plurality of measuring points arranged at different positions around the modeling area (hole 6a). It constitutes a temperature detecting means for the unsintered material powder 22 around the side surface of the modeled object (O) surrounding the modeled object, particularly the inner wall portion of the modeling area (hole 6a). The thermocouple 20 is embedded and arranged inside the insulator 9.

In the modeling apparatus of FIG. 1, the powder laying roller 11 is arranged so that the region from the upper part of the hole 5a of the modeling table 4 to the upper surface of the opening at the upper part of the collection container 10 can be moved. Known configurations can be used for the rotary drive system of the powder spreading roller 11 and the (horizontal) reciprocating movement system in the above region. Although detailed illustration of these powder spreading rollers 11 is omitted in FIG. 1, at least the left-right (horizontal) reciprocating movement in FIG. 1 and the rotational movement in the forward and reverse directions can be independently controlled. It is composed. The material powder is supplied and recovered by the powder spreading roller 11 at the time of modeling, for example, as follows.

When forming one layer, the material supply stage 5 is raised so that an appropriate amount of the material powder above the hole 5a can be supplied. On the other hand, the modeling stage 6 is made to stand by, for example, by lowering the height of one layer of the modeled object. In this state, the powder laying roller 11 is rolled from the upper part of the hole 5a to the upper part of the modeling stage 6 from the left side in the drawing, and the modeling stage 6 or the already modeled object (which has already been modeled) while acclimatizing one layer of material powder O) Supply on. Further, by rolling the powder laying roller 11 to the upper opening of the collection container 10, excess material powder exceeding one layer is collected inside the collection container 10.

FIG. 11 shows an example of a hardware configuration for heating and cooling (temperature control) using the induction heating coil 8 of the above-mentioned modeling apparatus (FIG. 1). In FIG. 11, the lead portion 81 of the induction heating coil 8 is electrically connected to the AC power supply 86 via the power supply line 82, the matching transformer 88, and the power supply line 84. As the AC power supply 86, for example, one capable of auto-matching the output frequency as described later is used. The CPU (601) of the control device (600) described later can control the power, frequency, duty ratio, and the like of the output AC of the AC power supply 86 via the sequencer 87.

On the other hand, the refrigerant (cooling water) of 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 via the refrigerant flow path 83. The chiller 85 is for controlling the circulation 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 control unit such as a pump. .. Further, the chiller 85 is provided with an interface means with a control circuit, and the CPU (601) of the control device (600) described later appropriately transmits control information to set the temperature of the refrigerant (cooling water) or per unit time. Flow rate can be set.

FIG. 13 shows a configuration example of the control device 600 (control system) of the modeling device of FIG. The control system of FIG. 13 is composed of a CPU 601 including a general-purpose microprocessor and the like, a ROM 602, a RAM 603, interfaces 604, 605, 606, and the like. In addition, the control device 600 may be provided with a network interface or an external storage device composed of, for example, an SSD or HDD disk device, if necessary.

The ROM 602 stores, for example, a control program and control data for causing the CPU 601 to execute the basic control of the modeling apparatus of FIG. 1 and the temperature control of the present embodiment. The storage area for the control program and the control data stored in the ROM 602 may be configured by a storage device such as an E (E) PRO so that the control program and the control data 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. The function related to the temperature control control procedure described later is realized by the CPU 601 executing the control program of the present embodiment (for example, FIG. 8). When an external storage device such as an SSD or HDD is arranged, the above control program and control data can be stored in, for example, a file format. Further, an external storage device such as an SSD or an 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 the SSD and the HDD, and may be composed of a recording medium such as various detachable optical disks, a detachable SSD or HDD disk device, and a detachable flash memory. Such various removable computer-readable recording media are used, for example, to install or update a control program constituting a part of the present invention in ROM 602 (E (E) PROM area). be able to. In this case, various removable 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 an external storage device) includes, for example, the "diffusion bonding boundary temperature" (described later) relating 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 control program related to temperature control, firmware, and the like stored in the ROM 602 (or an external storage device (not shown)). As a result, for example, each functional block (or control step) shown in FIG. 8 (of the control device 600) is realized.

Further, in FIG. 13, the control device 600 is provided with interfaces 604, 605, and 606. Of these, for example, the interface 604 is used to receive three-dimensional modeling data (data format such as 3D CAD and 3DCG data is arbitrary) from an external device. The interface 605 is also 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 powder spreading roller 11, a laser light source 12, and a drive system (of a 3D printer) for raising and lowering the modeling stage 6. Further, when a decompression device for adjusting the atmosphere in the modeling chamber 1 and an inert gas supply device (all 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.

Further, FIG. 13 shows, in particular, the chiller 85, the sequencer 87, and the sensors 609 of the temperature control system. The sensors 609 correspond to the thermocouples 18 and 20 or the radiation thermometer 19 for temperature detection. Each part of these temperature control 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 by transmitting the control signal in a predetermined signal format.

When a network interface is arranged, this interface can be used for communicating with other control terminals (not shown), other modeling devices, servers on the network, and the like. For this network interface, for example, a network communication method by a wired or wireless connection, for example, a communication method such as IEEE802.3 for a wired connection and IEEE802.11 or 802.11 for a wireless connection can be used. The interface 604 may be configured as a network interface, or input / output of modeling data may be performed via network communication.

Next, the outline of the 3D modeling process in the modeling apparatus of FIG. 1 will be described. The modeling chamber 1 is accessible to the inside through a work window (not shown). Prior to modeling, the modeling material (material powder 22) is stored in the material supply stage 5 and the base plate 7 is attached in advance.

After that, 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 there are circumstances such as the modeling material being a material that easily oxidizes, the inside of the chamber is depressurized from the exhaust port 2 with a vacuum pump for the purpose of lowering 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 an issue as an atmosphere requirement in the modeling chamber 1, the modeling chamber 1 does not necessarily have to be sealed. Further, for example, by constantly supplying and discharging the inert gas during modeling, the oxygen concentration in the modeling chamber 1 may be controlled to a specified value or less as a result. Similarly, modeling may be performed while collecting the fume and suspended material powder generated in the modeling chamber 1 by supplying and discharging the inert gas.

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

When the base plate 7 is made of a conductive material, preheating can be performed by using the induction heating coil 8. In order to start modeling 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 equal to the upper surface of the modeling table 4. However, when the induction heating coil 8 is used for the preheating, the lower component of the modeling stage may also generate heat at the same time as the preheating of the base plate 7. In consideration of this, it is desirable that the portion that can penetrate the inside of the coil during preheating and molding is made of the same insulating material as the above-mentioned insulator 9.

Further, the preheating of the base plate 7 may be performed not by using the induction heating coil 8 but by using a resistance heating heater provided on the modeling stage. In this case, the material of the base plate 7 may or may not be conductive. The resistance heating heater needs to be provided at a position where it cannot enter the inside of the induction heating coil 8 during energization.

The temperature of the base plate 7 is controlled by using a thermocouple 18 provided in the base plate 7 as a control point. The command temperature for preheating the base plate 7 may be the same as the command temperature for the modeled object (during modeling) described later. The method of determining the command temperature of this 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 of a configuration in which the temperature can be raised to the preheating temperature even in the 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, the modeling of the first layer is started. In FIG. 1, the powder spreading roller 11 is made to stand by on the left side of the material storage hole, the material supply stage 5 is raised, and an appropriate amount of material powder is supplied onto the modeling table 4. A slightly larger amount than the amount required for forming the thin film is supplied. The powdering roller 11 is translated and rotated to the right at a desired speed. In this way, a thin film of the material powder is formed on the base plate 7 while transporting the pile of the material powder protruding on the supply stage to the right.

The thickness of the thin film to be formed can be controlled by adjusting the relative height of the molding stage 6 with respect to the powder spreading roller in advance. The powder spreading roller 11 passes over the base plate 7 and the remaining powder material is poured into the recovery container 10. After that, the powdering roller is translated to the left as it is, and returned to the initial waiting place. Further, by slightly raising the modeling stage 6 and then returning the powder spreading roller 11 to the standby place, the thin film formed on the outward path may be crushed or scraped to obtain a desired film thickness. In this case, the powder spreading roller 11 is returned to the standby position while being rotated.

The preheating of the base plate 7 is not turned off even during the formation of the thin film. However, if the powdering roller 11 contains a conductive material and the induced heat generation affects the motion accuracy and the thin film forming behavior of the powdering roller 11, only while the powdering roller 11 is passing over the induction heating coil 8. , The heating energization of the induction heating coil 8 may be controlled to be cut off.

Although the powder-laying roller 11 has been illustrated as a means for forming the thin film in the above, the thin-film formation can be performed not only by the powder-laying roller 11 but also by a scraper or the like.

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

In order to control the laser spot scanning, the CPU 601 of the control device 600 inputs three-dimensional model data (3DCAD, 3DCG data, etc.) of a modeled object prepared in advance from an external device via the interface 604. Then, the three-dimensional model data is decomposed into the laminated data of the horizontal cross section, and the data of the scan locus of the modeling layer corresponding to each layer is generated. Further, the CPU 601 generates drive data of a scanning system, for example, a galvano scanner 16, based on the locus data of the modeling layer. The laser scanning optical system is not limited to the above configuration. For example, it is conceivable to use a rotary scanning system such as a polygon mirror, if necessary, without being limited to a swing scanning system such as a galvano scanner. Further, in the present embodiment, the laser beam (L) is considered as the energy beam, but when another energy beam such as an electron beam is used for radiant heating of the material powder 22, the source and the scanning system are the same. The vendor may change it as appropriate.

As described above, in this embodiment, the induction heating coil 8 continues to heat the base plate 7 and the modeled object while scanning the laser beam and sintering the thin film.

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 of the second layer is supplied and the thin film is formed in the same manner as in the first layer. In addition, in order to shorten the modeling time, a feasible part of the material supply process may be performed in parallel during the modeling of the first layer.

After that, the second and higher layers are also shaped in the same manner. In this embodiment, the induction heating coil 8 is constantly heated during modeling, and the temperature of the modeled object O is maintained at a desired temperature. The temperature control by the induction heating coil 8 from the initial stage of modeling to the end of modeling will be described in detail later.

When the modeling is completed, the temperature of the modeled object O is started to be lowered while maintaining the atmosphere of the modeling chamber 1. For example, the energization of the induction heating coil 8 is cut off, and the modeled object O or its surroundings is cooled to a temperature at which the operator can work. During this temperature drop, the control device 600 can continue to monitor the temperature of the modeled object (or its surroundings) using thermocouples 18 and 20 and a radiation thermometer. Then, when the temperature drops 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 modeling chamber 1. After the temperature has been lowered, the control device 600 raises the modeling stage 6 to project the modeled object onto 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 modeling stage 6. Further, the operator cleans the material powder scattered in the modeling chamber 1 and takes out the material powder (22) in the collection container 10 as necessary, whereby the modeling work is completed. After that, if necessary, the final modeled product (molding) is obtained through a treatment for removing the material powder adhering to the modeled object O, a heat treatment for the modeled object O, a processing for removing the base plate 7, an additional processing for the modeled object O, and the like.

Here, the materials of the base plate 7 and the modeled object, which are suitable in the present embodiment, 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 to have a melting point sufficiently higher than the temperature at which diffusion bonding of the modeling material occurs. Further, when the base plate 7 is preheated by induction heating using the induction heating coil 8, the base plate 7 also needs to be a conductive material.

If the bonding force between the base plate 7 and the modeled object is too weak, cracks may occur between the plate and the modeled object before the residual stress generated during modeling is relaxed. Further, if the rigidity and fastening force of the base plate 7 are too low, warpage and distortion may occur during molding before the residual stress is relaxed. Therefore, it is necessary to select the plate material, plate thickness, and fastening torque that can sufficiently withstand the temporary residual stress during modeling and provide the bonding force and rigidity. In order to facilitate 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 product as the plate material. Since the thermal conductivity and melting point are the same as those of the modeling material, it is possible to join under the same sintering conditions as when sintering the modeled object. The same level of strength can be expected.

Next, selection of a modeling material (material powder 22) suitable for this embodiment will be described. In the present embodiment, the induction heating coil 8 is driven by alternating current to generate an alternating magnetic field in the modeling area (hole 6a), and mainly 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 modeled object O is sufficiently smaller than that of the eddy current loop generated in the modeled object O that has already been modeled (solidified). It is based on the phenomenon that almost no heat is generated in the powder material powder 22 as compared with the model O. This phenomenon appears more prominently as the size of the generated eddy current loops differs. Therefore, 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, the induced heat generation due to the alternating magnetic field is known to be due to hysteresis loss based on the magnetism of the material in addition to the above-mentioned eddy current loss. This hysteresis loss occurs uniformly in both the model O and the material powder 22.

In the present embodiment, it is particularly desirable that the portion of the modeled object O that has already been modeled is induced and heated, and the material powder 22 that has not been solidified in the modeling area (hole 6a) is not induced and heated. Therefore, considering that the hysteresis loss is uniformly generated in both the molded product O and the unshaped material powder 22, it is desirable that the material powder 22 has no magnetism. However, by increasing the frequency of the alternating magnetic field, the amount of heat generated by the eddy current loss can be dominated by the hysteresis loss. Therefore, by increasing the frequency of the alternating magnetic field applied by the induction heating coil 8, it is possible to carry out the present embodiment 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 (or) the modeled object (O) formed from the conductive material powder 22 existing in the modeling area (inside the hole 6a) during the modeling period. It is to control the temperature to keep warm. As described above, if the temperature of the modeled object (O) is not controlled, for example, the laser-irradiated portion rapidly expands by heat and then is cooled and shrunk to enter the modeled object (O). Stress residue occurs. Then, in particular, when the modeled object (O) is taken out from the modeling area (inside the hole 6a) or the base plate 7 is removed, the residual stress during modeling is released, and the shape of the modeled object (O) such as warpage or distortion is released. 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, temperature control is performed in which the modeled object (O) is heated (or kept warm) by the induction heating coil 8. .. However, the induction heating by the induction heating coil 8 acts not only on the shaped object (O) existing in the modeling area (inside the hole 6a) but also on the material powder 22 made of the same material.

Therefore, in the case of temperature control in which the modeled object (O) is heated (or kept warm) by the induction heating coil 8, for example, the condition for heating the modeled object (O) and the material powder 22 in the modeling area (hole 6a), For example, it is necessary to determine the upper limit temperature of heating in advance by experiment. This is because the material powders 22 that do not need to be solidified in terms of modeling, or the material powders 22 that surround the modeled object (O) and the surrounding material powders 22 that surround the modeled object (O) if excessive heating is performed. This is because diffusion bonding (melting in severe cases) may occur.

Hereinafter, the definition and determination method of the command temperature of the modeled object (O) during modeling and the "diffusion bonding boundary temperature" which is a standard for temperature control of the side surface of the modeling area (hole 6a) during modeling will be shown.

In the material powder used in the powder bed melt bonding, for example, an iron-based alloy material, a phenomenon in which adjacent grains are bonded to each other may occur by maintaining the temperature at a certain temperature or higher for a long time even if the melting point is not reached. This occurs when the atoms that make up the grain move to reduce the surface area of the grain. Since the particles that have been coarsened in this way and have become too large cannot be used for forming a thin film, they cannot be reused as a modeling material. Also, such bonding can occur even if the grains are not grains. If the modeling material powder in the modeling area is in contact with the wall surface of the modeling device at a high temperature, the material powder sticks to the wall surface, making it difficult to take out the modeled object, and it is necessary to maintain the device wall surface every time modeling is performed. Occurs. Therefore, it is desirable that the unformed material powder in the modeling area is kept at a low temperature at which such diffusion bonding does not occur, and therefore it is necessary to know 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 advisable to carry out 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 the test container 21 used in this diffusion bonding experiment.

FIG. 2 shows a state in which the material powder 22 is contained 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 you want to confirm the adhesion of the modeled object to the material powder, use the same material as the modeled object, and if you want to confirm the adhesion to the modeling area wall surface, create it from the same material as the modeling area wall surface.

The mass of the material powder 22 in the container can be grasped from the weight difference of the test container 21 before and after charging the material powder 22 into the test container 21. The lid 23 of the test container functions as a weight (ballast) to prevent the material powder 22 from scattering and to prevent the filling state of the material powder 22 powder from changing significantly. Further, the test container 21 and the lid 23 have, for example, a gap-fitting fitting structure, and are designed so that the volume inside the test container 21 can be known by measuring the insertion length of the lid 23 into the test container 21.

With the above configuration, the volume of the test container 21 and the mass of the charged material powder 22 can be obtained. 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 factor, the lower the temperature required for diffusion bonding and the shorter the time. In this experiment, the filling density (pressure) can be controlled by constantly controlling the filling of the material powder 22 into the test container 21.

When the temperature control conditions of the test container 21 and the material powder 22 are determined as shown in FIG. 2, it is desirable to perform the evaluation in a state where the filling rate is high in order to surely suppress the diffusion bonding in the actual molding. 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 a standard of heating temperature (for example, "diffusion bonding boundary temperature" below) that does not cause diffusion bonding between the material powder 22 itself or the material powder 22 and the test container 21. To ask.

However, not only the temperature but also the heating time (predicted total molding time in the apparatus of FIG. 1) and the filling density (pressure) are closely related to the conditions for diffusion bonding of the material powder (22). For example, even at the same heating temperature, diffusion bonding of the material powder 22 may or may not occur depending on the magnitude of the heating time (predicted total modeling time in the apparatus of FIG. 1) and the filling density (pressure). The modeling time of a modeled object can be quantitatively predicted from the number of layers of the modeled object, 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 molding 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 molding time. Obtain the "diffusion junction boundary temperature" which is the "upper limit temperature". 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 molding time". That is, if this "diffusion bonding boundary temperature" is within the heating time (predicted total molding time in the apparatus of FIG. 1) or a specific packing density (pressure), the material powder 22 can be continuously heated at that temperature. This is the temperature at which diffusion bonding does not occur.

In order to obtain the "diffusion bonding boundary temperature" used for temperature control of the test container 21 and the material powder 22, for example, the test container 21 containing the material powder 22 has a constant temperature capable of adjusting the atmosphere equivalent to that of the modeling chamber 1 of FIG. Put in a furnace. Then, under the same atmosphere as 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 at which diffusion bonding occurs and the time is evaluated.

Here, the criterion for "whether or not diffusion bonding occurs" may be adjusted to the level required for operation. If only the adhesion between the device wall surface and the material in the modeling area is an issue, it is sufficient to visually determine whether the test container and the material powder are adhered. On the other hand, when considering the reuse of modeling materials, it is necessary to measure the particle size distribution of the powder after heating and the residual oxygen concentration to determine whether or not it can be reused.

By conducting the above experiments, it is possible to obtain the above-mentioned "diffusion junction boundary temperature" that satisfies the same heating time (predicted total molding time) and packing density (pressure) as the apparatus of FIG.

Here, with respect to the original purpose of suppressing the accumulation of residual stress in the modeled object, the temperature of the modeled object during (or already modeled) modeling can be determined with reference to the above-mentioned "diffusion junction boundary temperature". For example, according to the inventor's experiment, the heating temperature of the modeled object is preferably, for example, about 50 ° C. to 100 ° C. higher than the "diffusion junction boundary temperature" obtained by the above experiment. It turned out that it can be used for.

That is, in the present embodiment, the commanded temperature of the modeled object by the induction heating coil 8 is determined based on the "diffusion bonding boundary temperature" obtained by the above experiment, for example, in the above range (50 ° C. to 100). (Approximately ° C) Set a high temperature value. Here, the modeled object command temperature is a control amount for controlling the induction heating coil 8 based on the temperature detected at the control points (temperature detection positions) of the radiation thermometer 19, thermocouples 18, 20, and the like. Equivalent to.

Such temperature control can alleviate the residual stress in the modeled object during modeling, but if the temperature is too high, the modeling material has an adverse effect of sticking to the modeled object. Based on the "diffusion bonding boundary temperature" obtained by the experiment, a person skilled in the art may determine within what range the heating temperature (heating upper limit temperature) of the modeled object should be obtained after confirming by his / her own experiment.

On the other hand, it goes without saying that the material powder 22 in the modeling area (hole 6a) should be controlled to a temperature lower than, for example, the above-mentioned "diffusion bonding boundary temperature" in the region on the inner surface of the modeling area. .. Regarding the unsintered (unformed) material powder 22 in the region of the inner surface of the modeling area, there is no particular adverse effect due to the low temperature, so the lower the temperature, the more desirable, and the positively from the side surface of the modeling area (hole 6a) It is desirable to cool. In the present embodiment, the inner side surface of the modeling area (hole 6a) and the material powder 22 inside the modeling area (hole 6a) can be positively cooled by the circulation of the refrigerant inside the induction heating coil 8.

Further, by controlling the temperature of the unmolded material powder 22 on the inner surface of the molding area (hole 6a) and the inside thereof to be lower than, for example, the above-mentioned "diffusion bonding boundary temperature", the unsintered (unshaped) material. It can be expected to have effects such as recycling and shortening the temperature lowering process after the completion of modeling.

Next, in the present embodiment, the configurations of the modeling stage 6, the induction heating coil 8, the insulator 9, and the temperature detecting means, which are considered to be suitable, will be described.

FIG. 3 schematically shows a cross section in the vicinity of the modeling area (hole 6a: FIG. 1) during modeling of the first layer. In the figure, the induction heating coil 8 is divided into three heating zones of upper, middle, and lower in the vertical direction, and output control can be performed based on each desired control point temperature. Each of the induction heating coils 8 is composed of a spiral, for example, a copper tube, and a refrigerant (cooling water) is circulated inside the induction heating coil 8 as described above. The induction heating coil 8 is embedded in the insulator 9. As the material of the insulator 9, an insulating ceramic material having high strength even at a high temperature, particularly aluminum nitride or silicon nitride which is resistant to thermal shock, is preferably used. The closer the distance between the induction heating coil 8 and the modeled object O, the better the heating efficiency. Therefore, 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 heat generation in the modeling table 4, the induction heating coil 8 and the modeling table 4 are arranged so as to have a distance in the cross section of the insulator 9. By embedding the induction heating coil 8 in the insulator 9 in this way, the induction heating coil 8 can also function as a cooling pipe on the side surface of the molding area, and the powder material on the side surface can be positively cooled. As the material of the insulator 9, it is desirable that the insulator 9 has a high thermal conductivity, and aluminum nitride or the like is preferable.

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

Subsequently, the temperature detecting means of each part will be described. How to use each detected temperature during modeling will be described later. As described above, a radiation thermometer 19 for measuring the upper surface temperature of the modeled object being modeled is arranged above the modeling area (hole 6a). It is desirable that the measurement points of the radiation thermometer 19 are a plurality of points in the upper surface of the modeled object, and it is ideal that the temperature distribution in the plane can be measured in a plane. As a matter of course, the housing of the radiation thermometer 19 is installed outside the area through which the modeling laser can pass. Further, the radiation thermometer 19 is provided with a filter that cuts the wavelength of the modeling laser.

At the time of modeling, it is desirable to calibrate the emissivity of the modeled object O and the material powder 22 with a radiation thermometer 19 in advance. The top surface temperature during molding is measured, for example, at least twice for each layer, immediately before and immediately after the sintering process. In the temperature measurement of the thin film on the upper part of the modeled object O immediately before the sintering step of one layer, the temperature of the thin film directly above the modeled object in the front layer is assumed to be equivalent to the upper surface temperature of the modeled object, and the measurement is performed. Immediately after the sintering process of one layer, the upper surface of the modeled object O is measured as it is. In this case, for example, the in-plane average temperature measured by the radiation thermometer 19 is used as the detection temperature.

Further, a thermocouple 18 provided on the base plate 7 is arranged in order to measure the temperature of the lowermost portion of the modeled object O. For example, by keeping the material of the base plate 7 and the material of the modeled object O the same, the temperature of the base plate 7 detected by the thermocouple 18 can be measured as the temperature of the lowermost surface of the modeled object. The position of the thermocouple 18 is preferably directly below the lowermost surface of the modeled object O. When the area of the lowermost surface of the modeled object O is large, it is desirable to provide a plurality of thermocouples in the plane on which the modeled object O is performed. As the thermocouple 18, a sheath thermocouple insulated from the base plate 7 can be used. Here, in order to suppress the self-heating of the thermocouple 18, a thermocouple that is too thick is not desirable, and a thermocouple having a sheath diameter of about 0.2 mm to 1 mm is preferably used.

Further, as described above, the thermocouple 20 is arranged at a position close to the inner surface of the insulator 9 in order to detect the temperature of the material powder 22 on the inner surface of the modeling area (hole 6a) or particularly near 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). Further, it is desirable that at least one thermocouple 20 is independently arranged in each of the three heating zones so that the temperature corresponding to the upper, middle, and lower 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. Further, it is desirable that a plurality of thermocouples 20 are provided at the same height and evenly distributed in the circumferential direction of the modeling area (hole 6a). As for these thermocouples 20, sheath thermocouples having a sheath diameter of about 0.2 mm to 1 mm can be preferably used.

Next, a temperature control method at each stage during modeling will be shown. FIGS. 3 to 6 show a state of modeling when the modeled object O is divided into three height regions of an upper layer, a middle layer, and a lower layer. FIG. 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 modeling of the lower layer of the modeled object O is completed. Further, FIG. 5 corresponds to a state in which the molding of the middle layer of the modeled object O is completed, and FIG. 6 corresponds to a state in which the modeling of the upper layer of the modeled object O is completed.

4 to 6 are diagrams based on FIG. 3 described above, and the relationship between each part and their reference numerals is the same as that in FIG. According to the configuration of FIG. 1, modeling by the laser beam L (sintering of one layer) is performed on the uppermost one layer of the modeling area (hole 6a), so that the modeled object is as shown in FIGS. 3 to 6. O is formed 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 the control command values and control points (temperature detection positions) of the lower layer, middle layer, and upper layer of the modeled object O, and the heating zones of the upper (part), middle (part), and lower (part). Shows the relationship. In FIG. 7, 701, 702, and 703 indicate control command values and control points (temperature detection positions) of the upper (part), middle (part), and lower (part) heating zones, respectively. Further, 704, 705, and 706 correspond to each stage of modeling of the lower layer, the middle layer, and the upper layer of the modeled object O, respectively.

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

In the middle layer shaping (section 705 of FIG. 7) from FIG. 4 to FIG. 5, the induction heating coil uses two zones, upper and middle (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. Further, as the control point of the central heating zone, the lower surface of the modeled object O (the measurement point of the thermocouple 18) is used.

Further, in the upper layer modeling (section 706 of FIG. 7) from FIG. 5 to FIG. 6, all of the induction heating coils 8 in the upper, middle, and lower three heating zones are used (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, in the central heating zone, since the temperature of the modeled object cannot be directly detected, the temperature of the material on the side surface is detected and controlled. The average value of the material temperature of the side surfaces in the upper and lower heating zones is set as the command temperature, and the inner side surface of the modeling area (measurement point of the thermocouple 20) is controlled as a control point.

Here, in the molding of the middle layer to the upper layer of the modeled object O (FIGS. 4 to 6), the CPU 601 of the control device 600 performs temperature control for determining the output value of the induction heating coil 8 by the procedure shown in FIG. be able to. FIG. 8 shows in detail the control when the upper surface temperature of the modeled object O is used as a control point.

The temperature control control of FIG. 8 is for keeping the temperature of the modeled object O at a constant target modeled object command temperature (807) determined based on the above-mentioned “diffusion bonding boundary temperature”. As shown in FIG. 8, in the control using the upper surface temperature of the modeled object O as the control point, the control cycle is set as a unit for each layer in order to determine the heating output for each layer. For example, the temperature and region of the upper surface of the modeled object to be measured may fluctuate significantly while repeating the sintering of one layer and the formation of the next thin film, and the temperature measurement is guided in real time as feedback to the drive of the heating coil 8. It's hard to get it done. Therefore, in the control of FIG. 8, the temperature of the upper surface is determined by using immediately before sintering, which is considered to be the lowest temperature in the molding of one layer, and immediately after sintering, which is considered to be high temperature.

The temperature control control in FIG. 8 is such that the amount of heating control by the induction heating coil 8 in the molding of a certain layer, for example, the N layer, is performed based on the temperature measurement in the molding of the front layer, for example, the N-1 layer. That is, before the N-1 layer is sintered, the CPU 601 of the control device 600 measures the temperature (801) immediately before the sintering (which is considered to be the lowest temperature in the modeling of the N-1 layer) by the radiation thermometer 19. Let me do it. Further, after the N-1 layer is sintered, the radiation thermometer 19 is used to measure the temperature (802) immediately after the sintering (which is considered to be the highest temperature in the modeling of the N-1 layer).

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) by using an appropriate calculation method (). 803). Further, by calculating the temperature deviation (804) of the temperature measurement (801, 802) immediately before and after sintering, the effect (temperature change) of heating by the induction heating coil 8 of the N-1 layer can be evaluated. ..

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 after the sintering of the N-1 layer, and is in the process of forming the subsequent N layer by an appropriate calculation method. The drive control amount of the induction heating coil 8 of the above is acquired (805). Then, using the acquired drive control amount (805), the induction heating coil 8 during modeling of the N layer is driven to heat (heat-retain) the modeled object O (806). An example of a method of calculating the drive control amount (or command temperature) of the induction heating coil 8 based on the temperature detection of a plurality of heating zones is shown in the second embodiment (FIG. 9).

As described above, in the present embodiment, the temperature control of the modeled object O is performed through the induction heating of the induction heating coil 8, and the temperature of the modeled object O is set based on the above-mentioned "diffusion bonding boundary temperature". The temperature is controlled to the determined constant modeled object command temperature. Therefore, the stress residue during the modeling period of the modeled object O is relaxed, and the modeled object (O) that may occur when the modeled object O is taken out from the modeling area (inside the hole 6a) or the base plate 7 is removed. Deformation (poor shape) can be satisfactorily suppressed. Further, by heating or keeping the entire modeled object (O) warm during the modeling period, the temperature difference in the vertical direction of the modeled object can be suppressed, and the shape defect due to the temperature distribution during modeling can be suppressed.

In that case, in the present embodiment, as described above, the commanded temperature of the modeled object is determined based on the "diffusion junction boundary temperature" obtained in advance by the experiment (FIG. 2). Therefore, accurate three-dimensional modeling does not occur without inadvertent sticking of the modeled object (O) and the unmodeled material powder 22, alteration of the unmodeled material powder 22, or adhesion to the inner wall surface of the modeling area. Is possible.

When controlling with the modeled object temperature as the control point as described above, the material temperature of the inner surface of the modeling area exceeds the diffusion bonding boundary temperature in a configuration in which the cooling capacity of the inner surface of the modeling area is insufficient. There is a possibility that it will end up. Therefore, the temperature control 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 via the thermocouple 20 or the like exceeds the diffusion bonding boundary temperature. It is desirable to keep it.

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 to lower the modeled object command temperature. For example, the commanded temperature of the modeled object can be lowered from the value obtained by adding a margin of about 50 ° C. to 100 ° C. to the above-mentioned "diffusion bonding boundary temperature" to the "diffusion bonding boundary temperature" itself obtained by experiments or the like. 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 control position) is set as the inner surface of the modeling area and the temperature of the material powder on the inner surface of the modeling area is directly controlled.

In the present embodiment, the case where the device is modeled to the limit of the modelable height of the device is described, but the present invention can also be applied to a modeled object having a low height. In such a case, the number of zones of the induction heating coil used for heating during modeling decreases according to the height of the modeled object.

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

FIG. 9 shows an example of determining a command value of a heating zone other than the uppermost portion and the lowermost portion 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 diagram of the modeling area (hole 6a) shown at the left end of FIG. 9, there is a (modeled) modeled object O, and the (unshaped) material powder 32 surrounds the modeled object O. The other configuration of the modeling device is the same as that of the first embodiment described above.

In the example of FIG. 9, five thermocouples 31 are arranged in each of 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 the inner wall surface. 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 the actual modeling, the plot (33) of the material temperature detection result is not shown in this way according to the amount of heat storage of the area of each modeling layer (volume of the layer) corresponding to the shape of the modeled object O. Linearity can occur.

Considering that the plot (33) of the material temperature detection result has non-linearity in this way, the command temperature of each heating zone is obtained from the material temperature detection results obtained from a plurality of (five in this example) thermocouples 31. The following calculation methods can be considered to determine the value.

In FIG. 9, 34 was determined based on the temperature detected in the uppermost and lowermost zones of each of the five thermocouple 31 temperature detection zones 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 by a straight line. Further, the CPU 601 can acquire the command temperature value at a position corresponding to the height of the three intermediate temperature detection zones by using the approximate line (34) and the distance of each zone, for example. That is, in the present embodiment, as shown in FIG. 9, the vertical temperature distribution on the side surface is gently connected with reference to the material temperature detected by the thermocouples 31 arranged in the uppermost and lowermost heating (temperature detection) zones. Set the command temperature for each heating (temperature detection) zone.

The frequency of the alternating current flowing through the induction heating coil 8 varies depending on the material and shape of the modeled object, but there are merits depending on the frequency. When the frequency is increased, the present invention may be applied to a magnetic material as described above. On the other hand, the merit of lowering the frequency is that the heat generation region generated in the skin of the modeled object becomes deeper than that of the high frequency. When the temperature near the skin of the modeled object decreases, more uniform heating of the modeled object can be realized. In addition, there is an advantage that the adhesion of the material powder to the modeled object can be suppressed by lowering the temperature in the vicinity of the epidermis. In consideration of the above, for example, when SUS316L, which is a non-magnetic material, is used as a modeling material, it is considered that the frequency of alternating current for energizing the induction heating coil 8 is, for example, about 150 kHz to 400 kHz.

<Embodiment 3>
In the above-described first embodiment, 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 separate configurations. For example, as shown in FIG. 10, a configuration in which a cooling water channel (cooling pipe) is arranged separately from these induction heating coils is also conceivable. FIG. 10 shows an example of a cross-sectional structure of a portion near the modeling table 4, and other configurations are the same as those of the above-described first embodiment (or second embodiment). Note that FIG. 10 illustrates a state in which the modeling stage 6 and the base plate 7 are in the uppermost positions.

In the example of FIG. 10, the cooling water channel 36 is arranged in the insulator 25, and the induction heating coil 37 (corresponding to the above-mentioned induction heating coil 8) is arranged in the defined space outside the insulator 25. There is. Further, a top plate 38 is arranged above the space where the induction heating coil 37 is arranged so that the material powder 22 does not flow into the space where the induction heating coil 37 is arranged. The cooling water channel 36 can be created, for example, by grooving the insulator 25, and it is not necessary to use a conductive material in 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 the induction heating coil in the insulator 25, and the portion of the insulator 25 can be easily manufactured. Further, the portion of the insulator 25 is not an integral part that covers the entire side surface of the modeling area, but can be formed by a combination of inexpensive plate-shaped members or the like. Further, since the induction heating coil 37 is not embedded, it is not necessary to consider problems such as deformation and breakage of the insulator 25 due to the difference in thermal expansion between the coil and the insulator 25.

However, in the configuration of FIG. 10, on the other hand, the distance between the induction heating coil 37 and the modeled object tends to be large, and the heating efficiency may decrease. Therefore, in the configuration of FIG. 10, the energizing energy of the induction heating coil 37 may be increased for the desired heating control. Further, if the top plate 38 is configured to withstand the vertical load from the powder spreading roller, the uppermost end position of the coil may be 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 embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes 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>
The results of modeling a three-dimensional model by the control procedure shown in FIG. 7 will be illustrated below in the modeling device based on the configuration illustrated in each of the above embodiments. The control conditions for modeling in this example are as follows.

The inside of the modeling chamber is replaced with nitrogen at normal temperature and pressure to reduce the oxygen concentration to 300 ppm or less.

The size of the modeling stage is a square shape of 144 mm × 144 mm, and the same applies to the base plate 7. Aluminum nitride is used as the material for the mounting plate of the modeling stage. As the material of 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), a material having an average particle size of SUS316L of about 7 μm was used. The thickness of the one-layer thin film formed by the powder spreading roller 11 through the molding is 40 μm. Further, as the induction heating coil 8, for example, a spiral coil having about 3 turns and a height of about 35 mm was arranged in three heating zones of upper, middle and lower as shown in FIG. As the AC power source that generates high frequency to drive the induction heating coil 8, an AC power source capable of auto-matching in the range of 150 kHz to 400 kHz was used, and the drive frequency during modeling was set in the range of 200 to 300 kHz.

A 0.5 mm diameter SUS sheath and a non-grounded K thermocouple were used as the thermocouple for temperature detection. Further, a thermometer 19 for measuring the temperature of the upper surface of the modeling area was used with a thermometer having a detection wavelength full width at half maximum of 8 to 15 mm, and the area average was taken from the surface measurement data to obtain the detection temperature.

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

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

After the modeling was completed under the above control conditions, the material powder 22 was not fixed 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 low layer of the modeled object were not observed. 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), but no sticking of the material powder 22 to the modeled object (O) formed into the desired shape was also observed.

Then, in order to evaluate the deformation of the modeled object (O), the modeled object (O) was removed from the base plate 7, and the warped shape was measured using the horizontal upper surface portion of the modeled object (O). In this embodiment, the horizontal upper surface portion of the modeled object (O) has a concave warp shape, and the maximum warp amount (concave depth) of about 27 μm is recognized with respect to the in-plane length of 100 mm. .. On the other hand, only the preheating 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 warp amount of the modeled object (O) formed under the same modeling conditions was 85 μm.

Therefore, according to this embodiment, the preheating of the base plate 7 and the induction heating of the modeled object (O) by the induction heating coil 8 are caused by suppressing the residual stress in the modeled object (O) and releasing the stress after taking out the modeled object (O). The amount of deformation to be performed could be reduced satisfactorily. According to this embodiment, the amount of deformation 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. It could be reduced to:

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 10, 10 ... Recovery container, 11 ... Powder roller, 12 ... Laser light source, 13 ... Collimator lens, 14 ... Beam expander, 15 ... Condensing lens, 16 ... Galvano scanner, 17 ... f-θ lens, 18, 20, 29-31 ... Thermocouple, 19, 28 ... Radiation thermometer, 21 ... Test container, 22, 32 ... (Unshaped) material powder, 23 ... Lid, 36 ... Cooling channel, 38 ... Top plate, 85 ... Chiller, 87 ... Sequencer, 601 ... CPU, 602 ... ROM, 603 ... RAM, O ... (preformed) modeled object.

Claims (14)

In a three-dimensional modeling apparatus that manufactures a three-dimensional model by laying a conductive material powder in the modeling area and repeating a series of operations of selectively radiating and sintering a part of the laid material powder.
An induction heating coil arranged on the outer peripheral portion of the modeling area and inducing heat generation of a modeled object inside the modeling area by energization.
A cooling device arranged on the outer peripheral portion of the modeling area and cooling the unsintered material powder in the modeling area.
A control device that executes temperature control of the modeled object by energizing the induction heating coil and controlling the cooling device.
3D modeling device equipped with. In the three-dimensional modeling device according to claim 1, the control device controls the energization of a plurality of the induction heating coils during the modeling of the modeled object within the predicted total modeling time of the modeled object. A three-dimensional modeling apparatus that controls energization 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. In the three-dimensional modeling apparatus according to claim 1 or 2, before Symbol controller through said cooling apparatus, the predicted temperature of the unsintered material powder existing on the side surface near the shaping area of the shaped article A three-dimensional modeling device that controls the cooling device so that the temperature is kept lower than the diffusion bonding boundary temperature corresponding to the upper limit temperature at which diffusion bonding of the material powder cannot occur within the total modeling time. In the three-dimensional modeling apparatus according to claim 1 , by forming the induction heating coil with a hollow material capable of circulating a refrigerant inside the induction heating coil, the induction heating coil also serves as the cooling device and the control device. a three-dimensional modeling apparatus that controls the circulation of the refrigerant inside of the induction heating coil. In the three-dimensional modeling apparatus according to any one of claims 1 to 4, a plurality of the induction heating coils, each of which can independently control energization, are defined at different positions around the modeling area. The control device is a three-dimensional modeling device that is arranged in a heating zone and executes temperature control of each of the heating zones via a plurality of the induction heating coils. In the three-dimensional modeling apparatus according to any one of claims 1 to 5, a first temperature measuring device for measuring the temperature of the uppermost portion of a modeled object inside the modeling area, the inside of the modeling area. A second temperature measuring device that measures the temperature of the bottom of the modeled object, or a third temperature that detects the temperature of a plurality of measuring points arranged at different positions around the modeling area. A three-dimensional modeling device including a measuring device, wherein the control device controls the induction heating coil based on the temperature measured by the first, second, or third temperature measuring device. In the three-dimensional modeling apparatus according to claim 6, before Symbol controller, based on the temperature measured by the third temperature measuring device, three-dimensional modeling apparatus that controls the cooling device. In the three-dimensional modeling apparatus according to any one of claims 1 to 7, before Symbol induction heating coil, the shaped area A and three-dimensional modeling apparatus Ru comprising an insulator for isolating the. In the three-dimensional modeling apparatus according to any one of claims 1 to 8, pre-Symbol cooling device and the shaped area A and three-dimensional modeling apparatus Ru comprising an insulator for isolating the. In the three-dimensional modeling apparatus according to any one of claims 1 to 9, the material powder formed in the modeling area is selectively radiantly heated and sintered by the energy beam generated by the energy beam irradiation apparatus. 3D modeling device. The three-dimensional modeling device according to claim 10, wherein the energy beam irradiation device is a laser irradiation device that irradiates a laser beam as the energy beam. The control program of the three-dimensional modeling apparatus for causing the control apparatus to execute any of the above temperatures in the three-dimensional modeling apparatus according to any one of claims 1 to 11. A computer-readable recording medium containing the control program according to claim 12. A method for manufacturing a three-dimensional model, in which the model is three-dimensionally modeled using the three-dimensional modeling device according to any one of claims 1 to 11.

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