JP2019131846A - Laminate forming apparatus - Google Patents

Abstract

To obtain a laminate forming apparatus capable of reducing the volume of a gas to be introduced into a vacuum chamber for the purpose of preventing scattering while preventing charged portions of a powder material due to irradiation of an electron beam from repelling to each other into scattering.SOLUTION: A laminate forming apparatus 100 is a laminate forming apparatus for manufacturing a three-dimensional laminate formed object 8 by repeating a process of selectively solidifying each layer of a powder bed while laminating within a vacuum chamber 1 a powder bed formed of a powder material 7, and comprises an electron gun 2 that irradiates an electron beam EB for solidifying a powder material 7 to a powder bed, a work groundsill 5 that is provided in a scanning range of an electron beam EB and adjustable in height, a plate 4 that is placed on the work groundsill 5 and for forming a powder bed, and a gas introducer 10 that introduces a molecular flow of a scattering prevention gas G to be positively ionized by an irradiation of an electron beam EB into the passage region S1 of an electron beam EB.SELECTED DRAWING: Figure 1

Description

  This invention is a laminate for producing a three-dimensional shaped object by repeating a step of selectively solidifying a powder bed of each layer while laminating a powder bed formed of a powder material made of metal particles in a vacuum chamber, for example. The present invention relates to a modeling apparatus.

  Three-dimensional shaped objects can be obtained by selectively solidifying the powder bed of each layer while laminating a powder bed made of a powder material consisting of metal particles that can be melted and solidified by electron beam irradiation in a vacuum chamber. An additive manufacturing apparatus to be manufactured is known. In the additive manufacturing apparatus using an electron beam as described above, since the powder material is negatively charged by the electron beam irradiation, the individual powder materials may repel each other due to the Coulomb force and the powder material may be scattered. In view of this, there is one in which an auxiliary gas is introduced into the vacuum chamber of the apparatus and the powder material is electrically neutralized by positively charging the auxiliary gas in the vicinity of the electron beam irradiation point (see, for example, Patent Document 1). . In addition, there is one that irradiates an electron beam to a material arranged on a work area while supplying a reactive gas that increases the conductivity of the powder surface of the powder material (for example, see Patent Document 2).

Special table 2010-526694 Special table 2011-506761 gazette

  However, since the gas introduced into the vacuum chamber easily diffuses, the gas described in Patent Document 1 and Patent Document 2 introduces a gas for preventing the powder material from being scattered into the entire vacuum chamber, In particular, as in the case of modeling a large model, there is a problem that if the vacuum chamber is increased in size, the amount of gas required increases and the production cost increases.

  The present invention has been made to solve the above-described problems, and while preventing powder materials charged by electron beam irradiation from repelling each other and scattering, a vacuum chamber is provided to prevent scattering. It is possible to obtain an additive manufacturing apparatus capable of reducing the amount of gas introduced into the apparatus.

  The additive manufacturing apparatus of the present invention is an additive manufacturing method for manufacturing a three-dimensional shaped object by repeating a process of selectively solidifying a powder bed of each layer while laminating a powder bed formed of a powder material in a vacuum chamber. An apparatus, an electron beam irradiation means for irradiating a powder bed with an electron beam for solidifying a powder material, a mounting table provided in a scanning range of the electron beam and having an adjustable height, and mounted on the mounting table, A powder bed forming unit that forms a powder bed and a gas introducing unit that introduces a molecular flow of a gas that is cationized by irradiation with an electron beam into a region through which the electron beam passes are provided.

  According to the additive manufacturing apparatus of the present invention, since the gas introducing portion for ejecting the molecular flow of the gas that is positively ionized by the electron beam irradiation to the electron beam passing region is provided, the powder materials charged by the electron beam irradiation are mutually connected. While preventing repulsion and scattering, the amount of gas introduced into the vacuum chamber to prevent scattering can be reduced.

It is the schematic which shows the additive manufacturing apparatus in Embodiment 1 of this invention. It is a side view which shows the gas introduction part which concerns on Embodiment 1 of this invention. It is a top view which shows the gas introduction part which concerns on Embodiment 1 of this invention. It is the schematic which shows the additive manufacturing apparatus in Embodiment 2 of this invention. It is a side view which shows the gas introduction part which concerns on Embodiment 2 of this invention. It is a top view which shows the gas introduction part which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIGS. 1 to 2B. 1 is a schematic diagram showing an additive manufacturing apparatus according to Embodiment 1. FIG. In the additive manufacturing apparatus 100, an electron gun 2, that is, an electron beam irradiation means is accommodated in an electron gun chamber 3 installed above the vacuum chamber 1, that is, a storage chamber. The electron gun 2 is opposed to the floor 1a of the vacuum chamber 1, and irradiates the electron beam EB to a predetermined scanning range. An opening 3b that connects the electron gun chamber 3 and the vacuum chamber 1 is provided in the floor portion 3a of the electron gun chamber 3, and an electron beam EB irradiated from the electron gun 2 passes through the opening 3b to form a vacuum chamber. 1 is irradiated. The opening 3b can be opened and closed by a shutter (not shown), and the vacuum chamber 1 and the electron gun chamber 3 are shut off by closing the opening 3b except when the electron beam EB is irradiated. It is possible to maintain.

  The electron beam EB can be operated at an irradiation position by being deflected by an electromagnetic force. Further, the electron beam EB spreads from the electron gun 2 to the floor 1a with a predetermined spread angle. In the first embodiment, a region where the electron beam path moves when the irradiation destination of the electron beam EB moves within the scanning range is defined as the electron beam EB passage region, and the passage region in the vacuum chamber 1 is defined as the passage region S1 and the electron. A passage region in the gun chamber 3 is defined as a passage region S2. The area of the opening 3b is equal to or larger than the horizontal cross-sectional area of the passing region S2 at the height of the floor 3a, and the electron beam EB passes through the opening 3b regardless of the path in the passing region S2. Then, it enters the vacuum chamber 1. In addition, since the spread of the electron beam EB is larger toward the lower side, the horizontal sectional area of the passing region S1 is larger than the horizontal sectional area of the passing region S2.

  On the floor portion 1a, a modeling region portion 1b on which the powder material 7 that is a raw material of the three-dimensional layered object 8 is spread is formed in the scanning range of the electron beam EB. The bottom surface of the modeling region portion 1b is formed by a work base 5 whose height can be adjusted by the lifting mechanism 6, that is, a mounting table, and the depth of the modeling region portion 1b is adjusted by raising and lowering the work base 5. .

  On the floor portion 1a, a powder bed forming mechanism 92 for installing the powder material 7 stored in the powder box 91 on the work base 5 is installed. The powder bed forming mechanism 92 supplies a predetermined amount of the powder material 7 into the modeling region 1b while moving and reciprocating in the upper part of the modeling region 1b, and spreads the powder material 7 on the work base 5. The powder box 91 is, for example, a rectangular parallelepiped box. When the powder bed forming mechanism 92 comes downward, the powder material 7 is dropped, and the powder material 7 is supplied to the powder bed forming mechanism 92. The powder material 7 is a powdery material that is solidified to form a three-dimensional structure, and is solidified by being melted or solidified or sintered by being irradiated with the electron beam EB from the electron gun 2. The powder material 7 is a powder material of metal particles such as a cobalt chromium molybdenum alloy or a titanium alloy, but is not limited thereto, and may be any material that can be melt solidified or sintered by irradiation with an electron beam EB. .

  Moreover, the gas introduction part 10 is installed in the floor part 1a. The gas introduction unit 10 is disposed in the vicinity of the modeling region unit 1b, and locally introduces the scattering preventing gas G in a molecular flow state into the passage region S1 of the electron beam EB through the ejection tube 104. The gas introduction unit 10 is connected to a gas supply unit 13 provided on the side wall of the vacuum chamber 1 via a pipe 103. The gas supply unit 13 is connected to a container 12 provided outside the vacuum chamber 1 via a pipe 102, and supplies the anti-scattering gas G held in the container 12 to the gas introduction unit 10. The container 12 is connected to the vacuum pump 11 via the pipe 101, and holds the anti-scattering gas G decompressed by the vacuum pump 11.

  The gas introduction part 10 and the plate 4 will be described in more detail. 2A and 2B are a side view and a plan view showing the gas introduction unit 10. Note that the powder material 7 is actually spread around the plate 4, but the powder material spread around the plate 4 is omitted in FIGS. 2A and 2B. The plate 4 is, for example, a metal plate having a square cross section, and a groove 4a is provided in a range where the electron beam EB is irradiated. When the powder material 7 is spread on the work base 5, the powder material 7 is also spread in the groove 4 a to form the first powder bed 71.

  The gas introduction unit 10 is provided with a plurality of ejection tubes 104 on the side surface on the side of the passage region S1 of the electron beam EB. Each of the ejection pipes 104 is, for example, a thin tube having a circular cross section, is provided in the gas introduction part 10 at a height V1 from the floor 1a, and extends from the gas introduction part 10 toward the passage region S1 of the electron beam EB. . A predetermined distance H1 is provided between the end of the ejection pipe 104 on the passage area S1 side and the groove 4a. The plurality of ejection pipes 104 are arranged along the width direction of the plate 4, and the number of the ejection pipes 104 is set in accordance with the width of the plate 4, and the anti-scattering gas G ejected from the ejection pipe 104 spreads over the entire upper portion of the plate 4. It comes to cover. For this reason, the electron beam EB irradiates the anti-scattering gas G regardless of the path in the passage region S1, and the anti-scattering gas G is positively ionized by the irradiation of the electron beam EB. The The anti-scattering gas G is not particularly limited as long as it is cationized by irradiation with the electron beam EB, but from the viewpoint of preventing the oxidation of the powder material, an inert gas such as argon or helium is used. Is desirable.

  The anti-scattering gas G is introduced from the ejection pipe 104 as a molecular flow. More specifically, the Knudsen number K which is an index indicating whether the flow of the anti-scattering gas G is a viscous flow or a molecular flow is set to be larger than 0.3. In the first embodiment, since the representative length of the system is the inner diameter D of the ejection pipe 104, the Knudsen number K is calculated by using the mean free path λ of the scattering prevention gas G and the inner diameter D of the ejection pipe 104, K = λ / D It is represented by The Knudsen number K is set by adjusting the mean free path λ and the inner diameter D of the ejection pipe 104. The mean free path λ can be adjusted by adjusting the pressure of the anti-scattering gas G. When the inner diameter D is reduced to adjust the Knudsen number K, the number of the ejection pipes 104 is increased in accordance with the amount of change in the inner diameter D, and the entire width of the ejection pipes 104 is adjusted to the width of the plate 4.

  The anti-scattering gas G introduced as a molecular flow is suppressed from diffusing as in the case of a viscous flow and flows linearly from the ejection pipe 104 as shown in FIG. The electron beam EB is locally introduced into the passage region S1.

  Next, the operation will be described. After the vacuum chamber 1 is evacuated to stabilize the degree of vacuum in the vacuum chamber 1, the working base is set so that the height from the upper surface of the plate 4 to the upper surface of the floor portion 1 a corresponds to one layer of the powder bed 71. The work base 5 is heated by adjusting the height 5 and irradiating the work base 5 with a preheating electron beam. The electron beam for preheating is one in which the output is suppressed more than the electron beam EB that melts and solidifies the powder material by adjusting beam parameters such as beam output, beam focus, and beam scanning speed. After the work base 5 is heated, the powder material 7 is spread on the work base 5. At this time, the powder material 7 is spread over the grooves 4 a of the plate 4 to form a first powder bed 71. The first powder bed 71 is preheated by heat conduction from the heated work base 5. As a result, the temperature of the powder material forming the first powder bed 71 rises, so that the powder material is negatively charged by the irradiation of the electron beam EB, and the powder materials are suppressed from being repelled and scattered by the Coulomb force. The The reason why the scattering of the powder material can be suppressed by the temperature increase as described above is that electric charges are conducted due to a decrease in electrical resistance accompanying the temperature increase, and charging of the powder material is suppressed.

  After the powder bed 71 is preheated, the anti-scattering gas G held in the container 12 is sent to the gas introduction unit 10, and the anti-scattering gas G is locally introduced into the passage region S1 of the electron beam EB through the ejection pipe 104.

  Next, the first powder bed 71 is irradiated with an electron beam EB according to a preset irradiation pattern to selectively solidify the powder material of the first powder bed 71. At this time, in the vicinity of the powder bed 71, the scattering prevention gas G introduced into the passage region S1 is irradiated to the electron beam EB, and positive ions are generated by the interaction between the scattering prevention gas G and the electron beam EB. This cation electrically neutralizes the powder material 7 of the first powder bed 71 that is negatively charged by irradiation with the electron beam EB. When solidification of the powder material is completed for the first powder bed 71, the irradiation of the electron beam EB is stopped, and the height of the work base 5 is lowered by the thickness of the second powder bed (not shown). A second powder bed is formed on the first powder bed 71 as in the case of the eyes. The second powder bed is heated by the residual heat of the first powder bed 71 solidified by the electron beam EB, so that the powder material forming the second powder bed becomes negative by the irradiation of the electron beam EB. It is charged and repelled by Coulomb force, and scattering of the powder material 7 is suppressed.

  After the formation of the second layer of powder bed, as in the case of the first layer, the scattering prevention gas G is locally introduced into the passage region S1 of the electron beam EB and irradiated with the electron beam EB to form the second layer of powder bed. 71 powder materials are selectively solidified. In addition, before irradiating the electron beam EB with respect to the 2nd layer powder bed, you may re-preheat the 2nd layer powder bed by irradiating the electron beam for preheating. In the same manner for the third and subsequent layers, the three-dimensional layered object 8 is manufactured on the work base 5 by repeating the step of selectively solidifying the powder bed of each layer while laminating the powder beds.

  The effect by Embodiment 1 is demonstrated. In order to confirm the effect of the first embodiment, the electron beam EB when the negatively charged powder material is repelled and scattered by the Coulomb force between the case where the scattering prevention gas G is introduced locally and the case where it is not introduced. The current values were measured as “allowable current values” and compared. In the measurement of the allowable current value, first, the degree of vacuum in the vacuum chamber 1 is stabilized, and the powder material 7 made of metal particles is uniformly spread over the groove portion 4a with a thickness of 100 μm, and then the spread powder material 7 is applied to the spread powder material 7 Then, the electron beam EB is irradiated. In addition, the powder material 7 is not preheated, and the electron beam EB is irradiated to the powder material 7 at room temperature. Under this condition, the current value of the electron beam EB is gradually increased, and the current value of the electron beam EB when the scattering of the powder material is confirmed is measured. The presence or absence of scattering of the powder material 7 is confirmed by visually confirming the inside of the vacuum chamber 1 from a viewing window (not shown) of the vacuum chamber 1 for about 2 seconds after irradiation with the electron beam EB. In the comparison of the allowable current value, the measurement is performed a plurality of times depending on whether the anti-scattering gas G is locally introduced or not introduced, and an average value is calculated and compared. As a result of measuring the allowable current value as described above, the average value of the allowable current value when the anti-scattering gas G is not introduced is about 0.6 mA, the allowable current value when the anti-scattering gas G is locally introduced. The average value was about 1.1 mA, and it was confirmed that there was an effect of increasing the allowable current value by introducing the local anti-scattering gas G. Even if the introduction of the scattering prevention gas G is local, such an effect is caused by the cations generated by the interaction between the scattering prevention gas G introduced into the passage region S1 and the electron beam EB. It is considered that the charged powder material 7 was electrically neutralized.

  According to the first embodiment, it is possible to reduce the amount of anti-scattering gas introduced into the vacuum chamber while preventing the powder materials charged by the electron beam irradiation from repelling each other and scattering. More specifically, it has a gas introduction part that introduces the molecular flow of the anti-scattering gas that is positively ionized by electron beam irradiation into the electron beam passage region, so that the anti-scattering gas is locally introduced into the electron beam passage region. It is possible to do. For this reason, it is not necessary to introduce the scattering prevention gas into the entire vacuum chamber, and the amount of the scattering prevention gas introduced into the vacuum chamber is reduced. The reduction in the amount of the anti-scattering gas introduced can reduce the cost associated with the anti-scattering gas, suppress an increase in gas molecules in the vacuum chamber, and suppress a decrease in the degree of vacuum. Thereby, since the fall of the energy of the electron beam by the collision of the gas molecule of scattering prevention gas and an electron beam is also suppressed, the increase in the energy input amount to an electron beam can be suppressed.

  Moreover, since the gas introduction part is installed in the floor part of the vacuum chamber, the scattering prevention gas is introduced in the vicinity of the powder bed, and the scattering of the powder material can be more effectively prevented.

Embodiment 2. FIG.
A second embodiment of the present invention will be described below with reference to FIGS. 3 to 4B. In addition, the same code | symbol is attached | subjected about FIG. 1 to FIG. The second embodiment is different from the second embodiment in that the gas introduction part is installed in the electron gun chamber. FIG. 3 is a schematic diagram showing an additive manufacturing apparatus in the second embodiment. In the additive manufacturing apparatus 200, a gas introduction unit 20 is installed on the floor 3 a of the electron gun chamber 3. The gas introduction unit 20 is disposed in the vicinity of the opening 3b, and locally introduces the anti-scattering gas G in the molecular flow state into the passage region S2 of the electron beam EB through the ejection tube 204. The gas introduction unit 20 is connected to a gas supply unit 23 provided on the side wall of the electron gun chamber 3 via a pipe 203. The gas supply unit 23 is connected to the container 12 via a pipe 202, and supplies the anti-scattering gas G held in the container 12 to the gas introduction unit 20.

The gas introduction unit 20 will be described in more detail. 4A and 4B are a side view and a plan view showing the gas introduction unit 20. The gas introduction unit 20 is provided with a plurality of ejection pipes 204 on the side surface on the opening 3b side. The ejection pipe 204 is, for example, a plurality of thin tubes having a circular cross section, and is provided in the gas introduction part 20 at a height V2 from the floor 3a and extends from the gas introduction part 20 side toward the opening 3b. A predetermined distance H2 is provided between the end of the ejection pipe 204 on the opening 3b side and the opening 3b. The plurality of ejection pipes 204 are arranged along the width direction of the opening 3b. The number of the ejection pipes 204 is set in accordance with the width of the opening 3b, and the anti-scattering gas G ejected from the ejection pipe 204 is in the opening 3b. It covers the entire upper part. For this reason, the electron beam EB irradiates the scattering prevention gas G no matter what path the electron beam EB passes through, and the scattering prevention gas G is positively ionized by the irradiation of the electron beam EB. The
The point that the anti-scattering gas G is introduced as a molecular flow from the ejection pipe 204 and is locally introduced into the passage region S2 is the same as in the first embodiment. Further, when the inner diameter D of the ejection pipe 204 is reduced in order to adjust the Knudsen number K, the number of the ejection pipes 204 is increased in accordance with the amount of change in the inner diameter D, so that the entire width of the ejection pipe 204 becomes the width of the opening 3b. Match.

  Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  Next, the operation will be described. As in the first embodiment, after the degree of vacuum in the vacuum chamber 1 is stabilized and the height of the work base 5 is adjusted, the work base 5 is heated with a preheating electron beam. After the work base 5 is heated, the powder material 7 is spread on the work base 5 and in the groove 4a of the plate 4 to form the first powder bed 71 in the groove 4a. The first powder bed 71 is preheated by heat conduction from the work base 5. After the powder bed 71 is preheated, the anti-scattering gas G held in the container 12 is sent to the gas introducing unit 20, and the anti-scattering gas G is locally introduced into the passage region S2 of the electron beam EB through the ejection pipe 204.

  After introducing the anti-scattering gas G into the passage region S2, the first powder bed 71 is irradiated with the electron beam EB in accordance with a preset irradiation pattern. At this time, in the vicinity of the opening 3b in the electron gun chamber 3, the scattering preventing gas G and the electron beam EB interact to generate cations. The cations enter the vacuum chamber 1 through the opening 3b, reach the vicinity of the first powder bed 71, and are negatively charged by the irradiation with the electron beam EB. Material 7 is electrically neutralized. When solidification of the powder material is completed for the first powder bed 71, the irradiation of the electron beam EB is stopped, and the height of the work base 5 is lowered by the thickness of the second powder bed (not shown). Thereafter, a second powder bed is formed on the first powder bed 71 in the same manner as in the first layer. Since the subsequent steps are the same as those in the first embodiment, the description thereof is omitted.

  According to the second embodiment, as in the first embodiment, since the gas introducing portion for introducing the molecular flow of the scattering prevention gas into the electron beam passage region is provided, the powder materials charged by the electron beam irradiation are repelled from each other. Thus, the amount of anti-scattering gas introduced into the vacuum chamber can be reduced while preventing the scattering.

  Further, the amount of anti-scattering gas to be introduced can be further reduced. More specifically, since the gas introduction part for introducing the anti-scattering gas into the electron beam passage region is installed in the electron gun chamber, the width to be covered by the ejection pipe provided in the gas introduction part is greater than that of the first embodiment. Is also getting smaller. This is because, as described above, the electron beam has a predetermined spread angle, and the spread becomes larger downward, so that the horizontal cross-sectional area of the passage region in the electron gun chamber is smaller than the horizontal cross-sectional area of the passage region in the vacuum chamber. Because. Since the width to be covered by the ejection tube is the width of the electron beam passage region, the width to be covered by the ejection tube in the second embodiment is the width that the ejection tube needs to cover in the first embodiment. The number of ejection pipes can be reduced, and the amount of anti-scattering gas to be introduced can be further reduced.

  Further, in the present invention, the embodiments and configurations can be appropriately combined, or the configurations can be partially modified or omitted without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Vacuum chamber, 1a floor part, 1b modeling area part, 2 electron gun, 3 electron gun chamber, 4 plate, 4a groove part, 5 work foundation, 7 powder material, 71 powder bed, 8 three-dimensional layered object 10, 20 Gas introduction part, 104, 204 ejection pipe, 100, 200 additive manufacturing apparatus, EB electron beam, G scattering prevention gas, S1, S2 passage region,

Claims (4)

A layered modeling apparatus for manufacturing a three-dimensional shaped object by repeating a process of selectively solidifying a powder bed of each layer while laminating a powder bed formed of a powder material in a vacuum chamber,
Electron beam irradiation means for irradiating the powder bed with an electron beam for solidifying the powder material;
A mounting table provided in a scanning range of the electron beam, the height of which can be adjusted;
A powder bed forming part mounted on the mounting table and forming the powder bed;
An additive manufacturing apparatus comprising: a gas introduction unit that introduces a molecular flow of a gas that is positively ionized by irradiation of the electron beam into a region through which the electron beam passes.   The additive manufacturing apparatus according to claim 1, wherein the gas introduction unit is installed on a floor portion having a modeling region portion on which the powder material is spread.   The additive manufacturing apparatus according to claim 1, wherein the gas introduction unit is installed in a storage chamber that stores the electron beam irradiation unit.   The additive manufacturing apparatus according to any one of claims 1 to 3, wherein the molecular flow has a Knudsen number greater than 0.3.

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