Patent Description:
In recent years, development of an additive manufacturing method and an additive manufacturing device in which various metal powders are mixed in advance and the mixed metal powder is used for molding has been in progress. Therefore, in order to improve the efficiency of the manufacturing process and shorten the time of the manufacturing process, there is a demand for an additive manufacturing device having a mixed powder function capable of quickly mixing a plurality of types of powders in a desired mixing ratio. For example, Patent Literature <NUM> discloses a technique for controlling the supply amount of powder, in which in order to distribute the pressure-fed powder to a desired supply amount in the supply passage until the powder is discharged to the heat source beam irradiation point, a branch valve is provided in the middle of the supply passage, the supply amount of powder is controlled by the opening and closing ratio of the branch valve, and the pressure-feeding force reduced by branching is compensated.

Further, Patent Literature <NUM> discloses a mixing technique for mixing powders, in which a material chamber with a shutter that opens and closes at the bottom and a mixing chamber provided at the lower part of the material chamber are included, multiple types of materials are stored in each of the material chambers, the supply amount is adjusted by the opening and closing area of the shutter at the bottom so that the materials have the desired mixing ratio, and the materials are mixed in the mixing chamber.

<CIT> relates to a new nozzle head or a new nozzle for the application of materials supplied in powder form or as powder and converted into the sintered and/or molten state essentially in the area of the nozzle opening. <CIT> relates to a gradient function part forming device and method based on additional material manufacturing.

However, in Patent Literature <NUM>, it is necessary to provide a branch valve and an adjustment and control mechanism of the branch valve for each powder which results in a large-scale device, the opening and closing ratio and the actual supply amount may vary due to wear of the branch valve, and supplying a mixed powder having a desired mixing ratio is difficult because the powder is clogged in the supply flow passage due to the adhesion of the powder to the branch valve.

Further, in the method of Patent Literature <NUM>, it is also difficult to achieve a stable mixing state quickly because the mixing ratio of materials is adjusted by the degree of opening and closing of the shutter when controlled, and the materials are dropped into the mixing chamber to be mixed.

Therefore, the objective of the present invention is to provide a mixed powder production method, a mixed powder production device, an additive manufacturing method, and an additive manufacturing device, with which a plurality of types of powders can be accurately and quickly mixed in a desired mixing ratio.

The following disclosure serves a better understanding of the present invention. The present invention provides a mixed powder production method as set out in claim <NUM>.

Further, the present invention provides a mixed powder production device for producing a mixed powder with a plurality of types of powders as raw materials, as set out in claim <NUM>.

Moreover, preferably, surface roughness of the inner wall of the container has an arithmetic average roughness of Ra <NUM> or less, and surface roughness of the outer wall of the insertion member has an arithmetic average roughness of Ra <NUM> or less.

Further, the present invention provides an additive manufacturing device for additive manufacturing using a mixed powder with a plurality of types of powders as raw materials, as set out in claim <NUM>.

In addition, the present invention provides an additive manufacturing method, as set out in claim <NUM>.

The present invention can provide a mixed powder production method, a mixed powder production device, an additive manufacturing device, and an additive manufacturing method, with which a plurality of types of powders can be accurately and quickly mixed in a desired mixing ratio.

Hereinafter, embodiments of the additive manufacturing device and the mixed powder production device according to the present invention will be described in detail with reference to the drawings. Then, the additive manufacturing method will be described together with the mixed powder production method. However, the present invention is not limited to the following embodiments. Further, in order to clarify the description, the following depiction and drawings are appropriately simplified.

<FIG> shows a schematic view of an additive manufacturing device <NUM> provided with a mixed powder production device <NUM>.

The additive manufacturing device <NUM> includes a plurality of powder supply devices <NUM> provided for each of a plurality of types of raw material powders <NUM> (hereinafter, also simply referred to as powders <NUM>) as raw materials, the mixed powder production device <NUM>, powder supply passages <NUM> connecting the powder supply devices <NUM> and the mixed powder production device <NUM>, a head portion <NUM> that irradiates a heat source beam <NUM> while discharging a mixed powder <NUM>, and mixed powder supply passages <NUM> connecting the head portion <NUM> and the mixed powder production device <NUM>. Further, although the embodiment describes a case of using a metal deposition system including the head portion <NUM>, a powder bed system may also be used.

When using the powder bed system, for example, instead of using the head portion <NUM> to discharge the mixed powder <NUM>, the mixed powder <NUM> produced by the mixed powder production device <NUM> is deposited in a predetermined range (bed) in advance, and then the heat source beam <NUM> is irradiated from the head portion <NUM> to the deposited layer to form a solidified layer with melting and solidification. This operation may be repeated for additive manufacturing.

The type of the powder <NUM> as a raw material is not particularly limited. As for the particle size of the powder <NUM>, when an average particle size (D50) is about <NUM> to <NUM>, the options of the powder supply device <NUM> that can be selected can be increased. Here, in the metal deposition system, in an integrated distribution curve showing the relationship between the particle size and the volume integration from the small particle size side, which is obtained by a laser diffraction method, the average particle size (D50) is about <NUM> to <NUM>, more preferably about <NUM> to <NUM>.

The powder supply devices <NUM> can be disposed according to the number of powders <NUM> to be mixed, and the powders <NUM> are stored in the powder supply devices, respectively. Each of the powder supply devices <NUM> is connected to the mixed powder production device <NUM> by the powder supply passage <NUM>, and pressure-feeds a preset supply amount for each of the powders <NUM> to the mixed powder production device <NUM>.

The method for supplying and controlling the powders <NUM> is not particularly limited, but the disc type can be used.

The disc type is a system that drops the powder to be supplied into a groove or the like on a rotating plate (dish) provided below a container containing the powder, and pressure-feeds the powder to a supply passage by a pressure-feeding fluid (pressure-feeding gas). With such a system, it is easy to control the supply amount of powder stably by controlling the rotation speed of the rotating plate. Further, since the supply amount of the powder can be changed by changing the speed of the rotating plate, the mixing ratio can be rapidly changed even during the additive manufacturing, and the additive manufacturing can be performed. A pressure-feeding gas <NUM> such as an inert gas or compressed air is used as the medium used for pressure-feeding.

Although not shown in <FIG>, it is preferable to provide a pressure-feeding fluid replenishment mechanism for replenishing the pressure-feeding fluid in the path of the powder supply passage <NUM> in order to compensate for the pressure loss of the powder supply passage <NUM>.

The head portion <NUM> is connected to the mixed powder production device <NUM> by the mixed powder supply passage <NUM> for pressure-feeding the mixed powder <NUM>. The head portion <NUM> is connected to an external control device, and discharges the mixed powder <NUM> while irradiating the heat source beam <NUM>.

The mixed powder production device <NUM> according to the present invention is to be described. <FIG> show an example of the mixed powder production device. Here, the mixed powder production device <NUM> includes the plurality of powder supply passages <NUM> provided for each of the powders <NUM>, a mixing chamber <NUM> to which the plurality of powder supply passages <NUM> are connected, and a discharge passage <NUM> for discharging the mixed powder <NUM>. The material of the powder supply passage <NUM> is not particularly limited, but a metal or resin pipeline member can be used. From the viewpoint of pressure resistance and wear resistance, for example, stainless steel or engineering plastic can be used.

The mixing chamber <NUM> includes a container <NUM> and an insertion member <NUM> disposed in the container <NUM> and having an outer wall facing an inner wall <NUM> of the container <NUM>, and a gap space <NUM> is formed between the inner wall <NUM> of the container <NUM> and the outer wall <NUM> of the insertion member <NUM>. At the upper part of the gap space <NUM>, openings <NUM> each connected to the plurality of powder supply passages <NUM> are provided. Moreover, at the lower part of the gap space <NUM>, the discharge passage <NUM> having a cross-sectional area equal to or less than the minimum cross-sectional area of the gap space <NUM> is provided. The discharge passage <NUM> is connected to a discharge opening <NUM>. Here, one of the features of the embodiment is that the cross-sectional area of the upper part of the gap space <NUM> is larger than the total of the cross-sectional areas of the plurality of powder supply passages <NUM>. Further, the cross-sectional area referred to here is a cross-sectional area in a cross section perpendicular to the direction in which the powder <NUM> flows, that is, the supply/discharge direction (the vertical direction).

Since the cross-sectional area of the upper part of the gap space <NUM> is larger than the total of the cross-sectional areas of the plurality of powder supply passages <NUM> (the total cross-sectional area), even if a difference in the supply amount of each of the powders <NUM> exists, the powders <NUM> can be sprayed into the gap space <NUM> and mixed in a desired mixing ratio without being clogged. Further, when the inside of the gap space <NUM> is maintained in a negative pressure state with respect to the pressure applied in the powder supply passage <NUM>, and the powder <NUM> is sprayed (introduced) from the powder supply passage <NUM> into the gap space <NUM> through the opening <NUM>, if a flow that draws the powder <NUM> into the gap space <NUM> is generated, the powder <NUM> can be sprayed into the gap space <NUM> without being clogged.

By doing so, even if a plurality of types of powders <NUM> are used, the mixed powder <NUM> in a desired mixing ratio can be accurately and quickly obtained.

Further, in order to efficiently mix the mixed powder <NUM>, preferably, the powders <NUM> are sprayed so as not to collide with each other in their traveling directions (the opposite directions) or a direction close to the traveling directions so that the powders <NUM> can flow smoothly in the gap space <NUM>. Specifically, for example, the outline of the cross section of the gap space <NUM> when viewed from the direction in which the powders <NUM> flow, that is, the supply/discharge direction (the vertical direction), can be a circular or polygonal annular shape.

Hereinafter, the configuration of the mixed powder production device <NUM> according to the first embodiment of the present invention is to be described in detail with reference to <FIG>. <FIG> is a diagram showing a schematic diagram and a partial cross-sectional view of the mixed powder production device <NUM> according to the first embodiment of the present invention. (a) of <FIG> is a diagram of the mixed powder production device <NUM> when viewed from the direction in which the powders <NUM> flow in, that is, from the upper surface side, (b) of <FIG> is a cross-sectional view at the center position when viewed perpendicular to the inflow direction of the powders <NUM>, (c) of <FIG> is a cross-sectional view from the A-A cross section, and (d) of <FIG> is a cross-sectional view from the B-B cross section.

<FIG> is an enlarged perspective view of the upper part of the mixed powder production device <NUM>, showing a state in which the powder supply passages <NUM>, the openings <NUM> connected to the powder supply passages <NUM>, and the gap space <NUM> are connected. <FIG> is a schematic diagram showing shape examples (a) to (b) of the gap space <NUM>.

As shown in (a) and (b) of <FIG>, the mixing chamber <NUM> includes the container <NUM>, the insertion member <NUM> disposed in the container <NUM> and having the outer wall facing the inner wall <NUM> of the container <NUM>, the gap space <NUM> formed between the inner wall <NUM> of the container <NUM> and the outer wall <NUM> of the insertion member <NUM>, the openings <NUM> provided at the upper part of the gap space <NUM> and connected to the plurality of powder supply passages <NUM>, and the discharge opening <NUM> provided at the lower part of the gap space <NUM> and connected to the discharge passage <NUM>. Hereinafter, each configuration is to be described.

For the container <NUM>, a metal material, a resin material, a fiber reinforced resin material, or the like can be used from the viewpoint of pressure resistance and wear resistance. Of these, the metal material such as stainless steel can be preferably used. Further, in order to allow the powders <NUM> flowing in the gap space <NUM>, which is to be described later, to be pressure-fed with a smooth flow to the discharge opening <NUM>, the smaller the surface roughness of the inner wall <NUM> of the container <NUM>, the better. Specifically, for example, the arithmetic average roughness Ra is preferably Ra <NUM> or less, more preferably Ra <NUM> or less, and even more preferably Ra <NUM> or less.

The shape of the insertion member <NUM> is to be described later. However, as for the material, a metal material, a resin material, a fiber reinforced resin material, or the like can be used from the viewpoint of pressure resistance and wear resistance. Further, in order for the powders <NUM> and the mixed powder <NUM> flowing in the container <NUM> to be guided without delay so as to be pressure-fed to the discharge opening <NUM> with a smooth flow, the smaller the surface roughness of the inner wall <NUM> of the container <NUM>, the better. Specifically, for example, the arithmetic average roughness Ra is preferably Ra <NUM> or less, more preferably Ra <NUM> or less, and even more preferably Ra <NUM> or less.

The opening <NUM> is an opening for introducing the powder <NUM> flowing in the powder supply passage <NUM> into the mixing chamber <NUM>. The opening <NUM> is connected to the upper part of the container <NUM>, and the number of the openings may be disposed equal to or more than the number of powder supply passages <NUM>. As for the disposition of the openings <NUM>, for example, as shown in <FIG> and <FIG>, the plurality of openings <NUM> can be disposed at rotationally symmetric positions. Further, for the opening <NUM> in which the pressure-feeding gas <NUM> and the powder <NUM> do not flow, the opening <NUM> may be appropriately sealed.

The gap space <NUM> is a space formed in the container <NUM> between the inner wall <NUM> of the container <NUM> and the outer wall <NUM> of the insertion member <NUM>, the upper part is connected to the opening <NUM>, and the lower part is connected to the discharge passage <NUM>. Further, as shown in <FIG> and <FIG>, the gap space <NUM> is a place where the plurality of types of powders <NUM> are introduced into one space through the openings <NUM> connected to each of the powder supply passages <NUM> provided for each of the plurality of types of powders <NUM>. That is, the gap space <NUM> can be rephrased as a mixing space.

The cross-sectional area of the upper part of the gap space <NUM> connected to the opening <NUM> has a cross-sectional area larger than the total cross-sectional area of the powder supply passages <NUM>. Moreover, the cross-sectional area of the lower part of the gap space <NUM> connected to the discharge passage <NUM> may be equal to or larger than the total cross-sectional area of the powder supply passages <NUM>. Furthermore, the wording of the "total cross-sectional area of the powder supply passages <NUM>" as used herein means the sum of the cross-sectional areas of the hollow portions of each of the powder supply passages.

If the gap space <NUM> has the above characteristics, even if a difference in the supply amount of each of the powders <NUM> exists, the powders <NUM> can be introduced and mixed in the gap space <NUM> without being clogged, so that a mixed powder in a desired mixing ratio can be obtained even with the plurality of types of powders <NUM>.

At this time, since mixing is performed by pressure-feeding with the pressure-feeding gas <NUM>, a mechanical driving force like a rotating member is not required. For example, the configuration of the embodiment is also suitable for mixing powders having densities of <NUM>/m<NUM> or more (<NUM> times or more) different from each other. In a state where the space communicates from the powder supply passage <NUM> to the discharge passage <NUM> via the gap space <NUM>, since the powder <NUM> is mixed while flowing, it is possible to realize highly uniform mixture stably.

Further, in the gap space <NUM>, it is preferable that the cross-sectional area of the upper part connected to the opening <NUM> is the maximum cross-sectional area, and the cross-sectional area of the lower part connected to the discharge passage <NUM> is the minimum cross-sectional area. Further, it is preferable that the change in cross-sectional area changes smoothly. For example, the outline of the gap space <NUM> is an inverted conical shape or an inverted polygonal pyramid, and it is preferable that the cross-sectional shape of the gap space <NUM> when viewed perpendicular to the flow direction of the powder <NUM> is smoothly inclined from the upper part to the lower part of the gap space <NUM>.

Further, as shown in (c) and (d) of <FIG>, it is preferable that the cross-sectional shape of the gap space <NUM> viewed from the flow direction of the powder <NUM> is an annular shape. In such a way, for example, even if the particle sizes and the specific gravity of the powders <NUM> are different, the powders <NUM> can be suppressed from flying in the gap space <NUM>. Further, the powder <NUM> or the mixed powder <NUM> can be pressure-fed to the discharge passage <NUM> without being clogged in the gap space <NUM>. In addition, the effect of suppressing the generation of turbulent flow of the pressure-feeding gas <NUM> can be expected.

The gap space <NUM> is formed by the inner wall <NUM> of the container <NUM> and the outer wall <NUM> of the insertion member <NUM>. (a) to (c) of <FIG> are diagrams showing the shape of the gap space <NUM>.

(a) to (c) of <FIG> show a case where the gap space <NUM> has an inverted conical shape, and show an example in which the angle α is changed when the diameter is expanded from the apex of the central axis of the cone toward the bottom of the cone. The specific angle may be more than <NUM>° to less than <NUM>°, but is preferably about <NUM>° to <NUM>° in order to moderate the change in the cross-sectional area. In such a way, the powders <NUM> can flow toward the discharge opening <NUM> without delay when merging in the gap space <NUM>. Further, (a) shows a case where the apex angle is <NUM>°, (b) shows a case where the apex angle exceeds <NUM>° and is less than <NUM>° (<<NUM>°), and (c) shows a case where the apex angle exceeds <NUM>° and is less than <NUM>° (<NUM>°<<NUM>°).

Here, (b) of <FIG> shows that the powder <NUM> can flow while sliding down in the gap space <NUM> by making the angle sharper and extending the gap space <NUM> in the flow direction of the powder <NUM>. Further, in (c) of <FIG>, the angle is made more obtuse and shortened in the flow direction of the powder <NUM>, so that suppressing the pressure loss of the pressure-feeding gas <NUM> for pressure-feeding the powder <NUM> can be expected, which is effective when the number of powders <NUM> to be mixed is small and the powders <NUM> are pressured-fed at a low pressure.

Moreover, it is also possible to mix in the mixing chamber <NUM> without using the insertion member <NUM>. By doing so, the mixing chamber <NUM> can be further miniaturized by the amount that the insertion member <NUM> is not inserted. When it is desired to use the insertion member <NUM>, for example, the flow velocity (flow rate) of the pressure-feeding gas <NUM> for pressure-feeding the powder <NUM> may be reduced to prevent the powder <NUM> from flying up.

One end of the discharge passage <NUM> is connected to the gap space <NUM>, and the other end is provided with a discharge opening <NUM> for discharging the mixed powder <NUM> pressure-fed from the gap space <NUM>. Moreover, the discharge opening <NUM> can be connected to the mixed powder supply passage <NUM> and can also be used as a connection portion when the mixed powder <NUM> is pressure-fed to a device or the like located further downstream.

The shape of the discharge passage <NUM> can be, for example, equal to or less than the minimum cross-sectional area of the gap space <NUM>. When the shape of the discharge passage is less than the minimum cross-sectional area of the gap space <NUM>, it is preferable to avoid a sharp decrease from the minimum cross-sectional area of the gap space <NUM>. The opening area of the discharge opening <NUM> can be equal to or less than the cross-sectional area of the discharge passage <NUM>. Further, at least one discharge opening <NUM> may be provided, and a plurality of discharge openings <NUM> may be provided by branching the discharge passage <NUM>.

(d) to (f) of <FIG> show a gap space <NUM>, which is another form of the gap space <NUM> including the inner wall <NUM> of the container <NUM> and the insertion member <NUM>. As shown in (d) to (f) of <FIG>, the gap space <NUM> may include an inner wall <NUM> of a container <NUM> and an outer wall <NUM> of an insertion member <NUM> having a shape facing the inner wall <NUM>.

As shown in <FIG>, the cross section when viewed vertically with respect to the flow direction of the powder <NUM> may have a shape other than the inverted conical shape. For example, the surface of the inner wall <NUM> of the container <NUM> may be convex toward the outside of the gap space as shown in (d) of <FIG>, the surface of the inner wall <NUM> of the container <NUM> may be convex toward the inside of the gap space as shown in (e) of <FIG>, or the cross section may have plural angle changes as shown in (f) of <FIG>.

A mixing chamber <NUM> having a container <NUM> and in a different form from the mixing chamber <NUM> of the first embodiment is to be described. The mixing chamber <NUM> in the embodiment is a mixing chamber <NUM> that includes the container <NUM> composed of a combination of divided blocks. <FIG> shows the mixing chamber <NUM> including the container <NUM> composed of the combination of the divided blocks.

The container <NUM> can also form the mixing chamber <NUM> by joining an upper block <NUM> having the opening <NUM>, a lower block <NUM> having the discharge opening <NUM>, and an intermediate block <NUM>, which are divided blocks. More specifically, for example, the upper block <NUM> has a cylindrical hollow portion <NUM> penetrating in the thickness direction that forms a part of the powder supply passages <NUM>, and the lower block <NUM> may be formed with a cylindrical hollow portion <NUM> penetrating in the thickness direction that constitutes the discharge passage <NUM>. The intermediate block <NUM> may include a funnel-shaped hollow portion <NUM> penetrating in the thickness direction that communicates with the cylindrical hollow portion <NUM> of the upper block and the cylindrical hollow portion <NUM> of the lower block.

By being divided in this way, for example, when the number or supply amount of the powders <NUM> is increased, it may be desired to increase the capacity of the gap space <NUM> in order to avoid collision or turbulence of the powders. Even in such a case, the volume of the gap space <NUM> can be easily changed by inserting a spacer between the upper block <NUM> having the opening <NUM> and the intermediate block <NUM>. Further, for example, if the position where the inclination of the inner wall <NUM> of the container <NUM> changes is divided, the configuration and assembly of the container <NUM> can be simplified.

<FIG> shows another mixed powder production device <NUM> according to the embodiment. The mixed powder production device <NUM> differs from the mixed powder production device <NUM> in that a pressure replenishment mechanism <NUM> is provided in the discharge passage <NUM>.

The pressure replenishment mechanism <NUM> is configured to control the increase in the flow rate of the pressure-feeding gas <NUM> for pressure-feeding the mixed powder <NUM> when the mixed powder <NUM> flowing from the gap space <NUM> to the discharge passage <NUM> is pressure-fed to the head portion <NUM>.

The pressure replenishment mechanism <NUM> can be disposed between the discharge passage <NUM> and the discharge opening <NUM> and in a direction perpendicular to the discharge passage <NUM>. The pressure replenishment mechanism <NUM> can introduce the pressure-feeding gas <NUM> into the discharge passage <NUM> by an arbitrary flow rate, and depending on the flow rate of the introduced pressure-feeding gas, it can be expected that the pressure inside the gap space <NUM> is to be more negative. Further, it can be expected that the mixed powder <NUM> is further pressure-fed to the head portion <NUM> without any delay.

Next, an embodiment of a mixed powder production method in which the plurality of types of powders <NUM> are mixed to obtain the mixed powder <NUM> is to be described with reference to <FIG>.

The embodiment is a mixed powder production method using a plurality of types of powders as raw materials. One of the features of the mixed powder production method lies in that the mixed powder production method includes a first step, in which a plurality of raw material powder supply passages provided respectively for each of the plurality of types of powders are used to pressure-feed the plurality of types of powders to a gap space; a second step, in which the pressure-fed plurality of types of powders are sprayed into the gap space having a cross-sectional area larger than the total of the cross-sectional areas of the plurality of raw material powder supply passages, thereby mixing the plurality of types of powders and obtaining a mixed powder; and a third step, in which the mixed powder is discharged from a discharge opening provided downstream from the gap space. Therefore, as mentioned above, in the mixed powder production device <NUM>, the relationship is such that the total of the cross-sectional areas of the plurality of powder supply passages <NUM> (the total cross-sectional area) < the upper cross-sectional area of the gap space <NUM>.

In the mixed powder production method of the embodiment, by maintaining a negative pressure state in the gap space <NUM> with respect to the pressure applied in the powder supply passage <NUM>, when the powder <NUM> is introduced from the powder supply passage <NUM> into the gap space <NUM> through the opening <NUM>, it can be expected that a flow that draws the powder <NUM> into the gap space <NUM> is generated. Due to this drawing flow, even if a difference in the supply amount of each of the powders <NUM> exists, the powders <NUM> can be introduced and mixed in the gap space <NUM> without being clogged. Therefore, a mixed powder in a desired mixing ratio can be obtained accurately and quickly even with the plurality of types of powders <NUM>.

Since mixing is performed by pressure-feeding with the pressure-feeding gas <NUM>, a mechanical driving force like a rotating member is not required. For example, the configuration of the embodiment is also suitable for mixing powders having densities of <NUM>/m<NUM> or more (<NUM> times or more) different from each other. In a state where the space communicates from the powder supply passage <NUM> to the discharge passage <NUM> via the gap space <NUM>, since the powders <NUM> are mixed while flowing, it is possible to realize highly uniform mixture stably. Hereinafter, each of the steps is to be described.

The first step is a step, in which the plurality of powder supply passages <NUM> provided for each of the powders <NUM> are used to pressure-feed the plurality of types of powders <NUM> to be mixed to the gap space <NUM>.

As a method of pressure-feeding the powder <NUM>, the pressure-feeding gas <NUM> can be used. The pressure-feeding gas <NUM> can use, for example, compressed air or an inert gas, but it is preferable to use an inert gas that can be expected to prevent oxidation, specifically, an argon gas or a nitrogen gas. The flow rate of the pressure-feeding gas can be appropriately changed by the powder supply device <NUM>.

The second step is a step, in which the plurality of types of powders <NUM> sprayed into the gap space <NUM> are mixed in the gap space <NUM>. At this time, by spraying the powders into the gap space <NUM> having a cross-sectional area larger than the total of the cross-sectional areas of the plurality of powder supply passages <NUM>, the powders can be sprayed into the gap space <NUM> without being clogged, and a highly uniform mixed powder can be obtained. When the powders <NUM> are sprayed into the gap space <NUM>, it is preferable that the powders <NUM> are sprayed into and mixed in the gap space <NUM> having a lower atmospheric pressure than the upstream (the powder supply passage <NUM>). In other words, the powders may be sprayed into and mixed in the gap space <NUM> having a low pressure, that is, the gap space <NUM> having a negative pressure region, with respect to the pressure applied upstream of the gap space <NUM> (the powder supply passage <NUM>).

According to the invention the relationship between the total of the cross-sectional areas of the plurality of powder supply passages <NUM> and the cross-sectional area of the gap space <NUM>, specifically, the ratio (S2/S1) of a cross-sectional area S2 of the gap space <NUM> to a total of the cross-sectional areas S1 of the plurality of powder supply passages <NUM> is <NUM> or more, preferably <NUM> or more, and more preferably <NUM> or more.

Further, the ratio (S2/S3) of the cross-sectional area S2 of the gap space <NUM> to an area (an opening area) S3 of the opening of the discharge opening <NUM> is <NUM> or more, preferably <NUM> or more, and more preferably <NUM> or more. Further, the ratio (S1/S3) of the total of the cross-sectional areas S1 of the plurality of powder supply passages <NUM> to the area S3 of the opening of the discharge opening <NUM> is <NUM> or more.

Further, the cross section of the gap space <NUM> when viewed from the flow direction of the powder <NUM> may have an annular shape. When the gap space <NUM> has an annular shape, the effect of suppressing the rising of the powders <NUM> sprayed into the gap space <NUM> and the effect of suppressing collisions of the plurality of types of powders <NUM> with each other in their traveling directions (the opposite directions) or a direction close to the traveling directions and gradually mixing the powders are expected. As a result, the powders <NUM> can flow smoothly in the gap space <NUM>, and the mixed powder <NUM> can be efficiently produced. For example, as shown in <FIG>, a flow <NUM> in which the powder <NUM> flows in the gap space <NUM> toward the discharge passage <NUM> along the shape of the gap space <NUM>, and a flow <NUM> in which the powder <NUM> flows while spreading in the gap space <NUM> toward the discharge passage <NUM> can be formed.

The third step is a step, in which the mixed powder <NUM> obtained in the second step is discharged by the discharge opening <NUM> through the discharge passage <NUM> provided downstream from the gap space <NUM>. The discharge passage <NUM> is provided with an opening <NUM> serving as a discharge opening <NUM> at one end. Further, at least one discharge openings <NUM> may be provided, and a plurality of discharge openings <NUM> may be provided by branching the discharge passage <NUM>.

Further, it is preferable that the cross-sectional area of the gap space <NUM> gradually decreases toward the discharge opening <NUM>. For example, the shape of the gap space <NUM> is an inverted conical shape or an inverted polygonal pyramid, and it is preferable that the cross-sectional shape of the gap space <NUM> when viewed perpendicular to the flow direction of the powder <NUM> is smoothly inclined from the upper part to the lower part of the gap space <NUM>.

Next, an additive manufacturing method for additive manufacturing using the additive manufacturing device of the embodiment is to be described.

One of the features of the additive manufacturing method using the additive manufacturing device of the embodiment lies in that the additive manufacturing method includes step A, in which a plurality of powder supply passages <NUM> provided for each of the plurality of types of powders <NUM> are used to pressure-feed the plurality of types of powders <NUM> to the gap space <NUM>; step B, in which the pressure-fed plurality of types of powders <NUM> are sprayed into the gap space <NUM> having a cross-sectional area larger than the total of the cross-sectional areas of the plurality of powder supply passages <NUM>, thereby mixing the plurality of types of powders and obtaining the mixed powder <NUM>; step C, in which the mixed powder <NUM> is discharged from the discharge opening <NUM> provided downstream from the gap space <NUM> to the mixed powder supply passage <NUM>; step D, in which the mixed powder <NUM> discharged from the discharge opening <NUM> is pressure-fed to the head portion <NUM> connected to the mixed powder supply passage13; and step E, in which the mixed powder <NUM> pressure-fed to the head portion <NUM> is discharged toward a molding site <NUM>, melted, and solidified.

Then, in the additive manufacturing method of additive manufacturing using the additive manufacturing device of the embodiment, it is possible to perform additive manufacturing while accurately and quickly mixing a plurality of types of powders in a desired mixing ratio.

The system of additive manufacturing is not particularly limited, but for example, the directed energy deposition system such as laser metal deposition, a powder bed system (powder bed fusion bonding system), a plasma powder overlay, or the like can be used. Further, the heat source beam <NUM> can be used as the heat source for melting the mixed powder <NUM>, and the heat source beam can be, for example, a laser beam, an electron beam, a plasma, an arc, or the like.

Examples are to be described in detail below. In the examples, the following was used as the mixed powder production device <NUM>. As for the powder supply devices, two TP-Z180111VEFDR manufactured by JEOL Ltd. and two PF2/<NUM> manufactured by GTV Co. , Ltd, a total of <NUM> units, were used to mix <NUM> types of raw material powders (powder A, powder B, powder C, and powder D). The supply amount of the raw material powder and the flow rate of the pressure-feeding gas were set for each of the four powder supply devices to set the total flow rate of the pressure-feeding gas to <NUM>.

The mixed powder production device used resin tubes with an inner diameter of <NUM> and an inner diameter of <NUM> for the powder supply passage, and a member having an inverted conical apex angle of <NUM>° and an outer wall surface having an arithmetic average roughness of Ra <NUM> or less for the insertion member.

The mixing chamber had an inverted conical inner wall facing the inverted conical insertion member, and was configured by connecting an upper block having four openings with an inner diameter of <NUM>, a lower block having a discharge opening with a diameter of <NUM>, and an intermediate block connecting the opening to the discharge opening. As shown in <FIG>, the upper block is formed with a cylindrical hollow portion that forms a part of the powder supply passage and penetrates in the thickness direction, and the lower block is formed with a cylindrical hollow portion that forms a discharge passage and penetrates in the thickness direction. The intermediate block includes a funnel-shaped hollow portion that penetrates in the thickness direction and communicates with the cylindrical hollow portion of the upper block and the cylindrical hollow portion of the lower block. Moreover, the material of each of the blocks was stainless steel (SUS303), and the arithmetic average roughness of the surface in contact with the raw material powder was Ra <NUM> or less.

Regarding the gap space formed by the inner wall of the container and the outer wall of the insertion member used in the embodiment, the upper end of the gap space had a maximum cross-sectional area, and the cross-sectional area S2 was <NUM><NUM>. Furthermore, the total of the cross-sectional areas of the powder supply passages (the total cross-sectional area) S1 could be calculated as (<NUM>/<NUM>)<NUM> × π × <NUM> (number of openings) + (<NUM>/<NUM>)<NUM> × π × <NUM> (number of openings) = <NUM><NUM>, and the opening area S3 of the discharge opening could be calculated as <NUM><NUM>. That is, it was confirmed that the ratio (S2/S1) of the total of the cross-sectional areas S1 of the powder supply passages to the cross-sectional area S2 of the gap space was <NUM>, and that the ratio (S2/S3) of the area (the opening area) S3 of the opening of the discharge opening to the cross-sectional area S2 of the gap space was <NUM>. Further, the ratio (S1/S3) of the opening area S3 of the discharge opening <NUM> to the total of the cross-sectional areas S1 of the plurality of powder supply passages <NUM> was <NUM>.

In the example, four types of raw material powders (hereinafter, powders A to D) shown in Table <NUM> were prepared.

The supply amounts of the powders A to D were respectively set by the powder supply device prepared for each of the powders A to D. As for each of the supply amounts, powder A was <NUM>/min, powder B was <NUM>/min, powder C was <NUM>/min, and powder D was <NUM>/min (the total supply amount of the powders A to D: <NUM>/min). Argon gas was used as the pressure-feeding gas. The supply pressure of argon gas was set to be constant at <NUM> MPa (gauge pressure), and the flow rate of the pressure-feeding gas (argon gas) was set to <NUM>/min for the powders A and B, and <NUM>/min for the powder C and the powder D.

In addition, in Examples <NUM> to <NUM>, the cases where the supply amounts of the powders A to D were changed while the type of the pressure-feeding gas, the supply pressure of the pressure-feeding gas, and the flow rate of the pressure-feeding gas remained the same as in Example <NUM> were implemented. In Example <NUM>, the supply amounts of powders A to D were set to powder A: <NUM>/min, powder B: <NUM>/min, powder C: <NUM>/min, and powder D: <NUM>/min, and the total was <NUM>/min. In Example <NUM>, the supply amounts of powders A to D were set to powder A: <NUM>/min, powder B: <NUM>/min, powder C: <NUM>/min, and powder D: <NUM>/min, and the total was <NUM>/min. In Example <NUM>, the supply amounts of powders A to D were set to powder A: <NUM>/min, powder B: <NUM>/min, powder C: <NUM>/min, and powder D: <NUM>/min, and the total was <NUM>/min. As described above, Table <NUM> shows the conditions of Examples <NUM> to <NUM>.

Further, as a comparative example, two types of powder C and powder D were mixed using a one-touch tube fitting KQ2 series Different Diameter Double Union Y (model: KQ2U04-06A) manufactured by SMC Corporation. The relationships between the cross-sectional areas at this time were that the total of the cross-sectional areas S <NUM> of the powder supply passages was 4π (mm<NUM>) × <NUM> (openings) = <NUM><NUM>, the cross-sectional area S2 of the confluence portion was <NUM><NUM>, and the area (the opening area) S3 of the opening of the discharge opening was <NUM><NUM>. That is, the ratio (S2/S1) of the total of the cross-sectional areas S1 of the powder supply passages to the cross-sectional area S2 of the confluence portion was <NUM>, and the ratio (S2/S3) of the opening area S3 of the discharge opening to the cross-sectional area S2 of the confluence portion was <NUM>. Further, the ratio (S1/S3) of the opening area S3 of the discharge opening <NUM> to the total of the cross-sectional areas S1 of the plurality of powder supply passages <NUM> was <NUM>.

The supply amount of powder C was <NUM>/min, the supply amount of powder D was <NUM>/min, and the total supply amount was <NUM>/min. Argon gas was used as the pressure-feeding gas, the supply pressure was set to be constant at <NUM> MPa (gauge pressure), and the flow rate of the argon gas was set to <NUM>/min for the powder C, and <NUM>/min for the powder D. As described above, Table <NUM> shows the conditions of Comparative Example.

In the example, the mixed powder obtained by mixing the powders was discharged from the head portion, and the amount of the mixed powder (hereinafter referred to as the total discharge amount) was measured and evaluated. Regarding Examples <NUM> to <NUM>, specifically, the powders A to D were supplied to the mixed powder production device and discharged from the head portion. More specifically, the powders A to D were pressure-fed from the mixed powder supply device to the mixed powder production device with argon gas and then mixed in the mixed powder production device to form the mixed powder, the mixed powder was pressure-fed to the head portion, and the mixed powder was discharged toward the measuring container provided below the head portion.

The total discharge amount was measured by measuring the weight change of the measuring container with a measuring instrument (an electronic balance) provided under the measuring container. The measurement cycle was about <NUM>, and the average value for <NUM> seconds was measured. The results are shown in Table <NUM>. In addition, the measured weight change was further differentiated, the converted value was calculated so that the supply amount (g/min) per minute was obtained from the differentiated value, and evaluation was performed with the vertical axis as the total discharge amount (g/min) and the horizontal axis as the elapsed time (s). Moreover, Comparative Example was also measured and evaluated in the same manner.

Table <NUM> shows the measurement results of the total discharge amount for each of the examples, and Table <NUM> shows the measurement results of Comparative Example <NUM>. Further, <FIG> shows the change over time of the total discharge amount of each of the powders in Example <NUM> for each sampling cycle, and <FIG> shows the change over time of the powder discharge amount in Comparative Example <NUM> for each sampling cycle.

In Examples <NUM> to <NUM>, as shown in Table <NUM> and <FIG>, since the difference between the average value and the target value for <NUM> in the steady state (<NUM> or later) is <NUM> at the maximum, it was confirmed that the powders could be mixed with high accuracy. In addition, since the change in the supply amount in the steady state (<NUM> or later) is within <NUM>% of the supply amount, even in the case of long-term operation, a mixed powder having a desired mixing ratio could be obtained.

Further, it could be confirmed that, even in the cases of Examples <NUM> to <NUM> in which the mixing ratio of the powders A to D was changed while the flow rate of argon gas for each of the powders was kept under the same conditions as in Example <NUM>, the average value of the total discharge amount is still close to the total value (target value) of each supply amount, that is, the mixed powder having a desired mixing ratio can be obtained without being affected by the difference in the properties (specific gravity, etc.) of the powder. Specifically, it could be confirmed that powders having different densities of <NUM>/m<NUM> or more (<NUM> times or more) can be stably mixed.

Conversely, in Comparative Example <NUM>, as shown in Table <NUM> and <FIG>, the total discharge amount was not stable, and the average value of the total discharge amount for <NUM> could not be calculated. In addition, the obtained result is that the spray amount gradually decreases.

Claim 1:
A mixed powder production method for producing a mixed powder with a plurality of types of powders as raw materials, comprising:
a first step of pressure-feeding the plurality of types of powders to a gap space (<NUM>) by using a plurality of raw material powder supply passages (<NUM>) provided respectively for each of the plurality of types of powders;
a second step of spraying the pressure-fed plurality of types of powders into the gap space (<NUM>) having a cross-sectional area larger than a total of cross-sectional areas of the plurality of raw material powder supply passages (<NUM>), mixing the plurality of types of powders, and obtaining the mixed powder; and
a third step of discharging the mixed powder from a discharge opening (<NUM>) provided downstream from the gap space (<NUM>);
wherein the mixed powder production method is characterized in that,
a ratio (S2/S1) of the cross-sectional area (S2) of the gap space (<NUM>) to the total of cross-sectional areas (S1) of the plurality of raw material powder supply passages (<NUM>) is <NUM> or more;
a ratio (S2/S3) of the cross-sectional area (S2) of the gap space (<NUM>) to an opening area (S3) of the discharge opening (<NUM>) is <NUM> or more;
a ratio (S1/S3) of the total of cross-sectional areas (S1) of the plurality of raw material powder supply passages (<NUM>) to the opening area (S3) of the discharge opening (<NUM>) is <NUM> or more.