JP2020128584A - Laminate molding method - Google Patents

Abstract

To provide a laminate molding method capable of sufficiently removing fume and a sputter.SOLUTION: A laminate molding method molds a three-dimensional structure 10 by repeating, in a chamber 2, a step (step S6) of radiating a laser 9 to a prescribed part of a metal powder layer 10a for forming a solidification layer 10b and a step (step S4) of paving the solidification layer 10b with metal powder for forming a next powder layer 10a. A flow rate of a gas to be supplied into the chamber 2 is increased to an amount at which the metal powder layer 10a does not scatter in the step (step S6) for forming the solidification layer 10b, and is decreased relative to that in the step (step S6) for forming the solidification layer 10b in the step (step S4) for forming the metal powder layer 10a.SELECTED DRAWING: Figure 1

Description

The present invention relates to an additive manufacturing method.

As a method for forming a three-dimensional structure, a step of irradiating a predetermined portion of the metal powder layer with a laser to form a solidified layer, and a step of spreading the metal powder on the solidified layer to form a next metal powder layer. There is known a layered manufacturing method in which the above steps are repeatedly performed in a chamber.
For example, Patent Document 1 discloses a technique of removing fumes generated during laser irradiation by locally flowing a gas into a chamber.

Japanese Patent No. 5653358

The inventors have found the following problems regarding the additive manufacturing method.
In the technique disclosed in Patent Document 1, the gas is caused to flow locally to remove the fumes and spatters together with the gas. Therefore, it is not possible to remove the fume and spatter generated in the portion other than the vicinity of the locally flowing gas. Therefore, it is not possible to sufficiently remove fume and spatter.

The present invention has been made in view of such problems, and an object thereof is to provide a layered manufacturing method capable of sufficiently removing fume and spatter.

One mode for achieving the above object is a step of irradiating a predetermined portion of the metal powder layer with a laser to form a solidified layer, and spreading the metal powder on the solidified layer to form a next metal powder layer. And a step of repeatedly forming a three-dimensional structure in a chamber, wherein the metal powder layer does not scatter in the step of forming the solidified layer at a flow rate of a gas supplied into the chamber. The amount is increased up to the amount, and the amount in the step of forming the metal powder layer is smaller than that in the step of forming the solidified layer.

In the layered manufacturing method according to the present invention, the flow rate of the gas supplied into the chamber is increased to an amount that does not scatter the metal powder layer in the step of forming the solidified layer, and the solidified layer is formed in the step of forming the metal powder layer. Less than the process. Therefore, it is possible to sufficiently remove fumes and spatters in the step of forming the solidified layer.

According to the present invention, it is possible to provide a layered manufacturing method capable of sufficiently removing fume and spatter.

It is a schematic diagram of the additive manufacturing apparatus which concerns on this Embodiment. It is a schematic cross section of the additive manufacturing apparatus which concerns on this Embodiment at the time of laser irradiation. It is a flow chart which shows the additive manufacturing method concerning this embodiment. It is an expanded sectional view of a metal powder layer at the time of laser irradiation. It is a schematic cross section of the additive manufacturing apparatus which concerns on this Embodiment at the time of forming a metal powder layer. It is a graph which shows the density of the three-dimensional structure in Examples 1-3 and Comparative Examples 1-5. 3 is an X-ray CT measurement image in Example 1. 9 is an X-ray CT measurement image in Example 2. 9 is an X-ray CT measurement image in Example 3. 8 is an X-ray CT measurement image in Comparative Example 1. 9 is an X-ray CT measurement image in Comparative Example 5. 7 is a graph showing the number of defects in Example 1 and Comparative Example 1. It is an expanded sectional view of a metal powder layer at the time of laser irradiation in the conventional additive manufacturing method.

Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, in order to clarify the explanation, the following description and drawings are appropriately simplified.

First, with reference to FIG. 1 and FIG. 2, a configuration of an apparatus (a layered manufacturing apparatus according to the present embodiment) for performing the layered manufacturing method according to the present embodiment will be described. As shown in FIG. 1, the additive manufacturing apparatus 1 includes a chamber 2, a hopper 3, a recoater 3 a, a blade 3 b, a base plate 5, a gas replacement unit 6, a gas supply unit 7, and an exhaust unit 8. A modeling space 4 is formed in the chamber 2.

As shown in FIG. 2, the additive manufacturing apparatus 1 includes a laser oscillator 91 in addition to the configuration shown in FIG. Note that FIG. 1 shows a laser 9 and a three-dimensional structure 10 in addition to the layered manufacturing apparatus 1. In addition, FIG. 2 illustrates the laser 9, the three-dimensional structure 10, and the metal powder layer 10 a in addition to the layered manufacturing apparatus 1. 2, the upper part of the chamber 2, the gas replacement part 6, the gas supply part 7, and the exhaust part 8 are not shown.

As shown in FIG. 1, the additive manufacturing apparatus 1 includes a chamber 2. The chamber 2 is a structure having a space inside. A modeling space 4 is formed below the chamber 2. The modeling space 4 has a bottom surface as a base plate and a side surface as an inner peripheral surface of the chamber 2. The base plate 5 is a plate-shaped member. As shown in FIG. 2, the base plate 5 is arranged in the chamber 2 so as to be vertically movable.

The hopper 3 stores metal powder inside. The bottom of the hopper 3 can be opened and closed. A recoater 3 a is arranged below the hopper 3. By opening the bottom of the hopper 3, a predetermined amount of metal powder can be supplied to the recoater 3a. The recoater 3a is movable in the horizontal direction. A blade 3b is attached to the lower portion of the recoater 3a. The blade 3b is a plate-shaped member extending in a direction perpendicular to the moving direction of the recoater 3a. The blade 3b is movable in the horizontal direction together with the recoater 3a.

Although details will be described later, when the three-dimensional structure 10 is formed, the bottom of the hopper 3 is opened and a predetermined amount of metal powder is supplied to the recoater 3a. Then, the recoater 3a is moved toward the modeling space 4, and a predetermined amount of metal powder is supplied to the modeling space 4. Since the blade 3b is attached to the lower portion of the recoater 3a, when the recoater 3a is moved toward the modeling space 4, the metal powder is leveled by the blade 3b. The metal powder is leveled by the blade 3b to form the metal powder layer 10a.

As shown in FIG. 1, the gas replacement portion 6 is formed in the chamber 2. The gas replacement unit 6 can supply gas into the chamber 2 and replace the atmosphere in the chamber 2. The gas supplied by the gas replacement unit 6 is helium gas. The position where the gas replacement portion 6 is formed is not particularly limited as long as it can replace the atmosphere in the chamber 2. The gas replacement portion 6 is formed, for example, on the side wall of the chamber 2 as shown in FIG. The gas replacement unit 6 may be formed on the ceiling of the chamber 2 or the like.

A gas supply unit 7 is formed in the chamber 2. The gas supply unit 7 supplies gas into the chamber 2 to generate a gas flow above the metal powder layer 10a. The gas supplied by the gas supply unit 7 is helium gas. The position where the gas supply unit 7 is formed is not particularly limited as long as it is a position where a gas flow is generated above the metal powder layer 10a. The gas supply unit 7 is formed, for example, as shown in FIG. 1, on the side wall of the chamber 2 and above the upper surface of the metal powder layer 10a.

An exhaust unit 8 is formed in the chamber 2. The exhaust unit 8 can exhaust the atmosphere in the chamber 2. The gas supplied from the gas replacement unit 6 and the gas supplied from the gas supply unit 7 are exhausted from the exhaust unit 8. The exhaust part 8 is formed so as to face the gas supply part 7, as shown in FIG. 1. The gas supplied from the gas supply unit 7 flows from the gas supply unit 7 toward the exhaust unit 8. Therefore, a gas flow is generated so as to cover the entire upper surface of the metal powder layer 10a.

As shown in FIG. 2, the additive manufacturing apparatus 1 includes a laser oscillator 91. The laser oscillator 91 irradiates the laser 9 toward the metal powder layer 10a. When modeling the three-dimensional structure 10, the metal powder layer 10 a is formed in the modeling space 4, as shown in FIG. 2. Then, the laser 9 is applied to a predetermined portion of the metal powder layer 10a to form the solidified layer 10b. The next metal powder layer 10a is formed on the solidified layer 10b. In this way, the solidified layer 10b is repeatedly formed to form the three-dimensional structure 10.

Next, the additive manufacturing method according to the present embodiment will be described with reference to FIGS. 1 to 5 and 13. FIG. 3 is a flowchart showing the additive manufacturing method according to the present embodiment. FIG. 4 is an enlarged cross-sectional view of the metal powder layer at the time of laser irradiation. FIG. 5 is a schematic cross-sectional view of the additive manufacturing apparatus according to the present embodiment when forming the metal powder layer. FIG. 13 is an enlarged cross-sectional view of a metal powder layer at the time of laser irradiation in the conventional additive manufacturing method.

In the layered manufacturing method according to the present embodiment, as shown in FIG. 3, first, a gas replacement step (step S1) is performed. In the step of replacing the gas (step S1), the atmosphere in the chamber 2 is replaced by using the gas replacement unit 6, and the oxygen concentration in the chamber 2 is set to 100 ppm or less. Next, the step of supplying the metal powder (step S2) is performed. In the step of supplying the metal powder (step S2), a predetermined amount of the metal powder is supplied from the hopper 3 to the recoater 3a.

Next, the step of lowering the base plate 5 (step S3) is performed. When the additive manufacturing method according to the present embodiment is started, the step of raising the base plate 5 is performed in advance, and the base plate 5 is moved to a position where the upper surface of the base plate 5 forms the same surface as the inner peripheral surface on the bottom side of the chamber 2. Raise. In the step of lowering the base plate 5 (step S3), the base plate 5 is lowered by an amount corresponding to the thickness of the metal powder layer 10a.

In the example shown in FIG. 3, after the step of supplying the metal powder (step S2) is performed, the step of lowering the base plate 5 (step S3) is performed. However, the order of performing step S2 and step S3 is not limited. For example, after the step of lowering the base plate 5 (step S3) is performed, the step of supplying the metal powder (step S2) may be performed. Further, the step of supplying the metal powder (step S2) and the step of lowering the base plate 5 (step S3) may be performed in parallel.

Next, the step of forming the metal powder layer 10a (step S4) is performed. In the metal powder layer 10a, as shown in FIG. 4, the recoater 3a supplied with the predetermined amount of the metal powder in step S1 is moved toward the modeling space 4 to supply the modeling space 4 with the predetermined amount of the metal powder. Since the blade 3b is attached to the lower part of the recoater 3a, when the recoater 3a is moved toward the modeling space 4, the metal powder is spread over the modeling space 4 by the blade 3b to form the metal powder layer 10a.

Next, a step of increasing the gas flow rate (step S5) is performed. In the step of increasing the flow rate of gas (step S5), gas is supplied into the chamber 2 using the gas supply unit 7. Therefore, in step S5, the gas flow rate in the chamber 2 is higher than in steps S1 to S4. The gas flow rate in the step of increasing the gas flow rate (step S5) is less than 15 L/min, preferably 5 L/min or more and less than 15 L/min, and more preferably 10 L/min or more and 12 L/min or less. .. When the gas is flowed at such a flow rate, the metal powder layer 10a does not scatter. When the step of increasing the gas flow rate (step S5) is performed, a gas flow is generated in the chamber 2.

Next, the step of irradiating the laser 9 (step S6) is performed. In the step of irradiating the laser 9 (step S6), as shown in FIG. 2, the laser oscillator 91 irradiates the metal powder layer 10a formed in step S4 at a predetermined position with the laser 9 to form the solidified layer 10b. In the step of irradiating the laser 9 (step S6), the irradiation position of the laser 9 is moved so as to scan the upper surface of the metal powder layer 10a. The irradiation position of the laser 9 is moved so as to be opposite to the gas flow.

FIG. 5 is a partially enlarged view of the metal powder layer 10a in the step of irradiating the laser 9 (step S6). The dotted arrow shown in FIG. 5 indicates the reflection direction of the laser 9. As shown in FIG. 5, when the metal powder layer 10a is irradiated with the laser 9, the metal powder layer 10a is melted and becomes a molten metal 10c. The metal powder produces spatters 12 and fumes 13 when melted.

When performing the step of irradiating the laser 9 (step S6), a gas flow is generated in a direction opposite to the traveling direction of the laser 9. Therefore, the generated spatters 12 and fumes 13 flow behind the laser 9 in the traveling direction of the laser 9 due to the gas flow. That is, the spatter 12 and the fume 13 can be sufficiently removed from the path of the laser 9.

Here, a case where the spatter 12 and the fume 13 are not sufficiently removed will be described. FIG. 13 is an enlarged cross-sectional view of a metal powder layer at the time of laser irradiation in the conventional additive manufacturing method. In the conventional additive manufacturing method, as shown in FIG. 13, a metal powder layer 100a is formed on a solidified layer 100b, and the metal powder layer 100a is irradiated with a laser 900. When the laser powder 900 is irradiated, the metal powder layer 100a melts and becomes the molten metal 100c. The metal powder produces spatters 120 and fumes 130 when melted.

In the conventional additive manufacturing method, the gas flow rate when irradiating the laser 900 is smaller than that in the additive manufacturing method according to the present embodiment. Therefore, in the conventional additive manufacturing method, the laser 900 is applied in a state where the spatter 120 and the fume 130 are not sufficiently removed. Therefore, the spatter 120 and the fume 130 are present on the path of the laser 900.

The laser 900 may reflect toward the molten metal 100c when the spatter 120 and the fume 130 are present on the path. When the laser 900 reflects toward the molten metal 100c, as shown in FIG. 13, it is easy for air to be entrained when the molten metal 100c convects. When the molten metal 100c is entrained with air and solidified, defects occur in the solidified layer 100b.

In the layered manufacturing method according to the present embodiment, since the spatter 12 and the fume 13 are removed from the path of the laser 9, the laser 9 is, as shown in FIG. 5, the second solidified layer 10b counted from the top. Easy to enter near the upper surface of. Therefore, it is difficult for air to be entrained when the molten metal 10c convects. Therefore, it is possible to suppress the occurrence of defects caused by the air entering the solidified layer 10b.

Next, a step of reducing the gas flow rate (step S7) is performed. In the step of reducing the gas flow rate (step S7), the gas supply from the gas supply unit 7 is stopped to reduce the gas flow rate in the chamber 2.

Next, a step of determining whether the three-dimensional structure 10 has a predetermined thickness (step S8) is performed. In the step of determining whether the three-dimensional structure 10 has a predetermined thickness (step S8), for example, it is checked in advance how many solidified layers 10b should be formed to give the three-dimensional structure 10 a predetermined thickness, and the predetermined number of times is determined. This is performed by determining whether or not the solidified layer 10b is formed.

In the step of determining whether the three-dimensional structure 10 has the predetermined thickness (step S8), if the three-dimensional structure 10 has the predetermined thickness (step S8 Yes), the additive manufacturing method ends. In the step of determining whether the three-dimensional structure 10 has the predetermined thickness (step S8), if the three-dimensional structure 10 has the predetermined thickness or less (step S8 No), steps S2 to S8 are performed again.

When performing the step of supplying the metal powder again (step S2), the gas supply from the gas supply part 7 is stopped in the step of reducing the gas flow rate (step S7), and the gas flow rate in the chamber 2 is low. Therefore, it is possible to spread the metal powder while suppressing the scattering of the metal powder. Thus, the additive manufacturing method according to the present embodiment can irradiate the laser 9 on the metal powder layer 10a while sufficiently removing the fume 13.

Hereinafter, the present invention will be specifically described with reference to examples. These descriptions do not limit the present invention.

[Example 1]
(Measurement of density)
The gas flow rate during laser irradiation was 10 L/min, and the gas flow rate when forming the metal powder layer was smaller than 10 L/min, thereby forming a three-dimensional structure. The three-dimensional structure formed in Example 1 was subjected to X-ray CT measurement to measure the density. The density of the three-dimensional structure in Example 1 was 99.8%. FIG. 7 shows an X-ray CT measurement sectional view in the first embodiment.

[Example 2]
The gas flow rate at the time of laser irradiation was 5 L/min, and the gas flow rate at the time of forming the metal powder layer was smaller than 5 L/min to form a three-dimensional structure. X-ray CT measurement of the three-dimensional structure formed in Example 2 was performed to measure the density. The density of the three-dimensional structure in Example 2 was 98.5%. FIG. 8 shows a cross-sectional view of X-ray CT measurement in Example 2.

[Example 3]
The gas flow rate at the time of laser irradiation was 12 L/min, and the gas flow rate at the time of forming the metal powder layer was smaller than 12 L/min to form a three-dimensional structure. X-ray CT measurement of the three-dimensional structure formed in Example 3 was performed to measure the density. The density of the three-dimensional structure in Example 3 was 99.6%. FIG. 9 shows a sectional view of X-ray CT measurement in Example 3.

[Comparative Example 1]
A three-dimensional structure was formed with a gas flow rate of 2 L/min during laser irradiation and formation of the metal powder layer. An X-ray CT measurement of the three-dimensional structure formed in Comparative Example 1 was performed to measure the density. The density of the three-dimensional structure in Comparative Example 1 was 98.2%. FIG. 10 shows an X-ray CT measurement sectional view in Comparative Example 1.

[Comparative Example 2]
A three-dimensional structure was formed with a gas flow rate of 5 L/min during laser irradiation and formation of the metal powder layer. However, in Comparative Example 2, the metal powder was scattered during the formation of the metal powder layer, and the three-dimensional structure could not be formed.

[Comparative Example 3]
A three-dimensional structure was formed with a gas flow rate of 10 L/min during laser irradiation and formation of the metal powder layer. However, in Comparative Example 3, the metal powder was scattered during the formation of the metal powder layer, and the three-dimensional structure could not be formed.

[Comparative Example 4]
A three-dimensional structure was formed with a gas flow rate of 15 L/min during laser irradiation and formation of the metal powder layer. However, in Comparative Example 4, the metal powder was scattered when the metal powder layer was formed, and the three-dimensional structure could not be formed.

[Comparative Example 5]
The gas flow rate at the time of laser irradiation was set to 15 L/min, and the gas flow rate at the time of forming the metal powder layer was made smaller than 15 L/min to form a three-dimensional structure. X-ray CT measurement of the three-dimensional structure modeled in Comparative Example 5 was performed to measure the density. The density of the three-dimensional structure in Comparative Example 5 was 89%. FIG. 9 shows an X-ray CT measurement sectional view in Comparative Example 5.

(Density measurement result)
FIG. 6 collectively shows the measurement results of the density in Examples 1 to 3 and Comparative Examples 1 to 5. As shown in FIG. 6, in Examples 1 to 3, compared to Comparative Example 1 and Comparative Example 5, a higher density three-dimensional structure could be formed. From this, it is considered that in Examples 1 to 3, laser irradiation could be performed while sufficiently removing fume.

Further, in Comparative Examples 2 to 4, the metal powder was scattered and the three-dimensional structure could not be formed. From this, it was confirmed that in Examples 1 to 3, scattering of the metal powder was suppressed by reducing the flow rate of the gas when forming the metal powder layer.

(Counting the number of defects)
With respect to the three-dimensional structure formed in Example 1 and the three-dimensional structure formed in Comparative Example 1, the number of defective portions was counted from the X-ray CT measurement sectional view. The counting result is shown in FIG. As shown in FIG. 13, in Example 1, the number of defects was smaller than in Comparative Example 1. From this, in Example 1, it was confirmed that the three-dimensional structure can be formed while suppressing the generation of defects.

By the invention according to the present embodiment described above, it is possible to provide a layered manufacturing method capable of sufficiently removing fume and spatter.

The present invention is not limited to the above-mentioned embodiments, but can be modified as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Laminated modeling device 2 Chamber 3 Hopper 3a Recoater 3b Blade 4 Modeling space 5 Base plate 6 Gas replacement part 7 Gas supply part 8 Exhaust part 9 Laser 91 Laser oscillator 10 Three-dimensional structure 10a, 100a Metal powder layer 10b, 100b Solidification layer 10c , 100c Molten metal 12,120 Sputter 13,130 Fume

Claims (1)

A step of irradiating a predetermined portion of the metal powder layer with a laser to form a solidified layer, and a step of spreading the metal powder on the solidified layer to form the next metal powder layer are repeated in the chamber 3 A layered manufacturing method for forming a three-dimensional structure,
The flow rate of the gas supplied into the chamber is increased to an amount that does not scatter the metal powder layer in the step of forming the solidified layer, and is smaller in the step of forming the metal powder layer than in the step of forming the solidified layer. To do
Additive manufacturing method.