JP6912927B2 - Manufacturing method of laminated structure - Google Patents

Description

The present invention relates to a method for manufacturing a laminated structure.

There is an additional manufacturing technique called Adaptive Manufacturing. As an example of the additional manufacturing technique, a method for manufacturing a laminated structure in which a layer of resin, metal or the like is formed and the formed layers are laminated to produce a three-dimensional model is known.
A 3D printer has been put into practical use as a typical example of a modeling apparatus using additional manufacturing technology. Since 3D printers can manufacture structures with complicated shapes in a short time, they are attracting attention as promising technologies in the aircraft industry and advanced technology fields such as medical treatment.

In a 3D printer, the powder material on the stage provided in the chamber is sintered by irradiation with a laser or an electron beam to form a sintered layer of the powder material, and the formed layers are laminated on the stage. To make a three-dimensional model.
In such a 3D printer, from the viewpoint of certainty in layer formation, it is required to stably irradiate the powder material with a laser or the like having a required amount of energy. Furthermore, when modeling by irradiating a laser or the like, the oxygen gas concentration around the powder material is reduced as much as possible from the viewpoint of improving the mechanical properties of the manufactured three-dimensional model and preventing the shape from deteriorating. Is required to do.

A general conventional 3D printer is a powder material in the presence of a nitrogen gas called a shield gas and an inert gas such as argon gas for the purpose of reducing the oxygen gas concentration around the powder material. Is irradiated with a laser or the like to form a sintered layer of a powder material to produce a three-dimensional model (Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-21218

However, just by reducing the oxygen gas concentration in the shield gas as in the conventional method for manufacturing a laminated structure described in Patent Document 1, the three-dimensional model to be manufactured is fragile and its mechanical properties are insufficient. there were.
Further, in the conventional method for manufacturing a laminated structure, it takes a long time to laminate a plurality of formed layers, and improvement in productivity has been required.

The present invention has been made in view of the above circumstances, and is capable of producing a three-dimensional model having sufficient mechanical properties and improving productivity. The challenge is to provide a method.

In order to solve the above problems, the present invention has the following configurations.
[1] A layer in which heat is supplied to the powder material in the presence of a shield gas supplied to reduce the concentration of oxygen gas around the powder material, and the powder material is sintered or melt-solidified. A method for producing a laminated structure in which the formed layers are laminated, wherein the heat conductivity of the shield gas is at least higher than that of air.
[2] The method for producing a laminated structure according to [1], wherein the shield gas contains at least one of helium gas and hydrogen gas.
[3] The method for producing a laminated structure according to [1] or [2], wherein the composition of the shield gas is selected according to the powder material.

According to the present invention, a three-dimensional model having sufficient mechanical properties can be produced, and productivity can be improved.

It is a schematic diagram which shows an example of the structure for demonstrating the manufacturing method of the laminated structure which concerns on one Embodiment to which this invention was applied.

In the present specification, the apparatus for manufacturing a laminated structure means an apparatus for producing a three-dimensional model by supplying heat to a powder material to form a layer of the powder material and laminating the formed layers. do.

Means for supplying heat to the powder material of the laminated structure manufacturing apparatus include, but are not limited to, irradiating a laser, an electron beam, or the like. The apparatus for manufacturing a laminated structure is used to sinter or melt and solidify a powder material by irradiation with a laser, an electron beam, or the like to form a layer of the powder material, and then stack the formed layers.

Sintering or melting and solidifying a powder material is also referred to as "sintering, etc." The layer of the powder material formed by sintering the powder material or the like is also referred to as "a layer in which the powder material is sintered or melt-solidified" or simply "a sintered layer of the powder material". However, in the present specification, "sintered layer of powder material" is not construed as being limited to a layer formed by sintering a powder material. That is, in the present specification, the "sintered layer of powder material" is a term that may be interpreted as the meaning of a layer in which a powder material is melted and solidified.

In the present specification, the shield gas means reducing the concentration of oxygen gas around the powder material when sintering the powder material, and stably supplying a required amount of heat to the powder material. It means a gas supplied around the powder material for the purpose of such things.

Hereinafter, a method for manufacturing a laminated structure according to an embodiment to which the present invention is applied will be described with reference to the drawings, taking as an example a case where a laser is used as a heat supply means for sintering a powder material or the like. .. In the drawings used in the following description, in order to make the features easier to understand, the featured parts may be enlarged for convenience, and the dimensional ratios of each component may not be the same as the actual ones. do not have.

FIG. 1 is a schematic view showing an example of the configuration of a laminated structure manufacturing apparatus 10 (hereinafter, also referred to as “manufacturing apparatus 10”). As shown in FIG. 1, the manufacturing apparatus 10 includes a laser irradiation source 1, a reflector 2, a modeling unit 3, a stage 4, a shield gas supply source 5, a chamber 6, a circulation machine 7, and a pipeline. It is roughly configured with L1 and a pipeline L2.
In the manufacturing apparatus 10, the powder material is placed on the stage 4. Examples of the powder material include, but are not limited to, known metals, alloys, resins and the like used in manufacturing equipment for laminated structures such as 3D printers.

The manufacturing apparatus 10 irradiates the powder material on the stage 4 with a laser from the laser irradiation source 1 via the reflector 2. By irradiating the laser, the powder material at the position irradiated with the laser can be sintered or the like. The position where the laser is irradiated on the powder material can be determined according to the angle of the reflector 2. The manufacturing apparatus 10 can form a layer having an arbitrary shape on the stage 4 by controlling the angle of the reflector 2 according to the input data.

The modeling unit 3 accommodates the stage 4. The modeling unit 3 can move in the vertical direction. The manufacturing apparatus 10 repeats a step of molding the sintered layer of the powder material on the stage 4 and a step of moving the molding portion 3 downward to form the sintered layer of the powder material into an arbitrary shape. Can be laminated to produce a three-dimensional model having an arbitrary three-dimensional structure.

The stage 4 is housed and fixed inside the modeling portion 3. The stage 4 can move in the vertical direction according to the vertical movement of the modeling unit 3. After a certain layer is formed on the stage 4, the stage 4 moves downward, so that the manufacturing apparatus 10 newly forms and laminates a sintered layer of powder material on the formed layer. can do. Therefore, the thickness of the sintered layer of the powder material is determined by the descending distance of the stage 4 (modeling portion 3).

The first end of the pipeline L1 is connected to the shield gas supply source 5, and the second end is connected to the modeling portion 3. The first end of the pipeline L2 is connected to the modeling portion 3, and the second end is open in the chamber 6.

The shield gas supply source 5 is connected to the modeling portion 3 via the pipeline L1. The shield gas supply source 5 supplies the shield gas to the periphery of the stage 4 housed in the modeling portion 3 via the pipeline L1. The shield gas supply source 5 is provided to maintain the purity of the shield gas inside the modeling portion 3 and the chamber 6 at a high level.

The shield gas is not particularly limited as long as the thermal conductivity of the shield gas is at least higher than that of air, and may be a mixed gas containing a gas of at least one chemical species. From the viewpoint of making the thermal conductivity of the shield gas higher than that of air, the shield gas is preferably a mixed gas containing at least one of helium gas and hydrogen gas.

In the method for producing a laminated structure of the present embodiment, the composition of the shield gas can be selected according to the properties such as the physical properties of the powder material.
For example, austenitic stainless steels and metals with an austenitic structure such as nickel alloys have low hydrogen embrittlement sensitivity. When the powder material contains a metal having an austenite structure, the powder material is easily oxidized, which tends to deteriorate corrosion resistance and the like. Therefore, when the powder material contains austenitic stainless steel and a metal having an austenitic structure such as a nickel alloy, it is preferable to apply a reducing gas such as hydrogen gas as a shield gas from the viewpoint of preventing oxidation.
On the other hand, when the powder material contains an alloy containing iron as a main component, it is preferable that the shield gas does not contain hydrogen gas from the viewpoint of preventing hydrogen embrittlement. When the powder material contains aluminum, titanium, or an alloy containing these as main components, it is preferable that the shield gas does not contain hydrogen gas from the viewpoint of preventing the formation of blow holes.

The chamber 6 has a modeling portion 3. Shield gas is led out from the modeling portion 3 to the chamber 6 via the pipeline L2.

The circulation machine 7 is provided in the chamber 6. The circulation machine 7 circulates the shield gas led out to the chamber 6 through the modeling unit 3 and the like to maintain the purity of the shield gas in the chamber 6 at a high level.

The manufacturing method of the laminated structure of the present embodiment will be described below as an example of the case where the manufacturing method of the laminated structure of the present embodiment is applied to the manufacturing apparatus 10 having the configuration described above.
The method for producing a laminated structure of the present embodiment is a method for producing a laminated structure in which a sintered layer of a powder material is formed in the presence of a shield gas and the formed layers are laminated, and the heat of the shield gas is used. It is characterized by having a conductivity at least higher than that of air.

First, in the method for manufacturing a laminated structure of the present embodiment, a shield gas is supplied to the inside of the modeling portion 3 and the chamber 6 in a state where the powder material is allowed to stand on the stage 4, and the oxygen gas is purged. do. From the viewpoint of improving the mechanical properties of the laminated structure and preventing deterioration of the shape, it is preferable to perform purging until the concentration of oxygen gas becomes 0.8% or less. When the concentration of oxygen gas inside the modeling portion 3 and the chamber 6 is 0.8% or less, it is easy to prevent the powder material from being deteriorated due to oxidation.

Next, in the method for manufacturing the laminated structure of the present embodiment, the powder material is irradiated with a laser from the laser irradiation source 1 via the reflector 2. By irradiating the laser, it is possible to form a sintered layer of the powder material by sintering the powder material at the position irradiated with the laser. The position where the laser is irradiated on the powder material can be controlled by the angle of the reflector 2.

Next, in the method for manufacturing a laminated structure of the present embodiment, the stage 4 is moved downward together with the modeling portion 3. By moving it downward, it is possible to form a new layer by sintering or the like on top of the layer that has already been formed by sintering or the like. After that, the stage 4 is moved downward, and a new layer is formed and sequentially laminated, whereby a three-dimensional modeled object can be manufactured.

In the method for producing a laminated structure of the present embodiment, since the thermal conductivity of the shield gas is at least higher than that of air, a laser can be used as compared with the case where an inert gas such as nitrogen gas or argon gas is used as the shield gas. When sintering or the like by irradiation, it is possible to prevent excessive heat input to the three-dimensional modeled object during modeling. Therefore, according to the method for manufacturing a laminated structure of the present embodiment, the temperature of the three-dimensional modeled object at the time of modeling can be lowered as compared with the case where an inert gas such as nitrogen gas or argon gas is used as the shield gas. ..

In the method for manufacturing a laminated structure of the present embodiment, the thermal conductivity of the shield gas is made higher than that of air in order to lower the temperature of the three-dimensional model in the process of modeling. By the way, as a means of lowering the temperature of the three-dimensional modeled object in the middle of modeling, after forming the sintered layer of the powder material by irradiating the laser, the stage 4 is moved downward to form the next sintered layer of the powder material. It is possible to lengthen the time until modeling. That is, if the laser irradiation interval is increased by irradiating the laser, moving the stage 4 downward, and irradiating the laser again, the temperature of the three-dimensional model can be lowered by natural heat dissipation.

However, if the laser irradiation interval is lengthened, it takes a long time to laminate the sintered layers of the sintered powder material, which lowers the productivity. In the method for manufacturing a laminated structure of the present embodiment, the temperature of the three-dimensional model during modeling is lowered without increasing the laser irradiation interval, and an excessive amount of heat is prevented from being stored in the three-dimensional model. can. For the above reasons, the productivity can be improved according to the method for manufacturing the laminated structure of the present embodiment.

(Action effect)
According to one embodiment of the present invention described above, since the thermal conductivity of the shield gas is at least higher than that of air, it is possible to prevent excessive heat input to the three-dimensional model during modeling. Therefore, it is possible to prevent oxidation of the three-dimensional modeled object during modeling, deterioration of mechanical properties, and shape deterioration, and it is possible to produce a three-dimensional modeled object having sufficient mechanical properties, and productivity. Can be improved.

Although one embodiment of the present invention has been described above, the present invention is not limited to such a specific embodiment. In addition, the present invention may be added, omitted, replaced, or otherwise modified within the scope of the gist of the present invention described in the claims.

<Example>
Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following description.

(Example 1)
A metal 3D printer device (“m2Cushing” manufactured by CONCEPT Laser) was used as the manufacturing device 10 for the laminated structure. The laser output of the metal 3D printer was 200 W, the layer thickness at the time of lamination was 30 μm, the lamination speed was 1000 to 1500 mm / s, and a titanium alloy (Ti6Al4V (Φ10 to 38 μm)) was used as the powder material. Under the above joining conditions, after the oxygen gas concentration in the modeling section 3 and the chamber 6 is reduced to 0.8% or less, helium gas (concentration: 100%) is supplied from the shield gas supply source 5 as a shield gas at 20 L / min. A three-dimensional model of a rectangular parallelepiped having a size of 10 mm × 10 mm × 20 mm was produced while being supplied to the modeling unit 3 and the chamber 6 at the flow rate of. The thermal conductivity of helium gas is 155.31 (mW / m / K (25 ° C.)).

(Comparative Example 1)
A rectangular parallelepiped three-dimensional model having a size of 10 mm × 10 mm × 20 mm was produced in the same manner as in Example 1 except that argon gas (concentration: 100%) was used as the shield gas. The thermal conductivity of argon gas is 17.62 (mW / m / K (25 ° C.)).

Table 1 shows the results of measuring the Vickers hardness (Hv) of the three-dimensional model manufactured in each example.

As a result of visual confirmation, it was found that the surface of the three-dimensional model of Example 1 had less darkened surface portions and the degree of surface oxidation was smaller than that of the three-dimensional model of Comparative Example 1. rice field. This is because the shield gas with high thermal conductivity is continuously supplied around the laminated structure, so that the heat of the sintered part is effectively removed in the process of sintering the powder material, and the powder material It is considered that this is because the oxidation reaction was suppressed.

Further, as shown in Table 1, the Vickers hardness of the three-dimensional model of Example 1 was reduced as compared with the Vickers hardness of Comparative Example 1. That is, it was found that the three-dimensional model of Example 1 was less brittle than the three-dimensional model of Comparative Example 1. This is because the powder material is a titanium-based active metal, so the three-dimensional model of Comparative Example 1 that has been exposed to high temperatures for a long time during sintering is more like oxygen gas dissolved in the three-dimensional model. It is considered that this was caused by the increase in the amount of nitrogen gas.
Based on this result, it is considered that in Comparative Example 1, the elongation and the drawing are reduced, and the manufactured three-dimensional model is more likely to be brittle.

The method for manufacturing a laminated structure of the present invention is particularly highly useful when applied to an apparatus for manufacturing a laminated structure by an additional manufacturing technique.

1 ... Laser irradiation source, 2 ... Reflector, 3 ... Modeling part, 4 ... Stage, 5 ... Shield gas supply source, 6 ... Chamber, 7 ... Circulator, 10 ... Laminated structure manufacturing equipment, L1 ... Pipe line, L2 ... Pipeline

Claims (2)

In the presence of a shield gas supplied to reduce the oxygen gas concentration around the powder material, heat is supplied to the powder material to form a layer in which the powder material is sintered or melt-solidified. , A method of manufacturing a laminated structure in which the formed layers are laminated.
The thermal conductivity of the shield gas is at least higher than that of air.
The shield gas is seen containing helium gas and hydrogen gas,
A method for producing a laminated structure , wherein the powder material contains austenitic stainless steel and a nickel alloy. The method for producing a laminated structure according to claim 1, wherein the composition of the shield gas is selected according to the powder material.

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