JP7003730B2 - Metal lamination modeling method - Google Patents

Description

The present invention relates to a metal laminated molding method.

The metal layer formed by repeating the steps of lowering the base metal body, forming the metal powder layer on the base metal body, and sintering the formed metal powder layer to form the metal layer. There is known a metal laminating molding method for forming a metal body having a three-dimensional structure by sequentially laminating the metal bodies.
On the other hand, Patent Document 1 discloses a technique for forming a three-dimensional structure by repeatedly discharging a cross-linking agent onto a metal powder layer to bond the metal powder. In Patent Document 1, the amount of powder supplied in all layers is measured, and if the amount of powder is insufficient, the powder is supplied again. Therefore, the molding accuracy can be improved.

Japanese Unexamined Patent Publication No. 2016-137598

The inventors have found the following problems with respect to a metal laminating molding method in which a metal layer obtained by repeatedly sintering a metal powder layer is sequentially laminated.
In general, such a metal laminated molding method has a problem that the thickness of each formed metal layer is not constant at the molding start stage, and sufficient molding accuracy cannot be obtained.
In order to make the thickness of the metal layer constant and improve the molding accuracy, it is conceivable to make the thickness of each metal powder layer constant. Here, if the step between the formed metal powder layer and the metal layer is measured and the amount of descent of the base metal body is determined based on this measured value, the thickness of each metal powder layer can be made constant. can. However, when such measurement is performed for all layers, there is a problem that the modeling speed is lowered.

The present invention has been made in view of the above problems, and provides a metal laminated molding method capable of suppressing a decrease in molding speed while improving molding accuracy.

The metal laminated molding method according to the present invention includes a step of lowering the base metal body, a step of forming a metal powder layer on the base metal body, and a step of sintering the formed metal powder layer to form a metal layer. It is a metal lamination modeling method that forms a metal body with a three-dimensional structure by repeating the step of forming and sequentially laminating the metal layers, and a predetermined N (N is an integer larger than 2) from the second layer. ) Only up to the layer, when the base metal body is lowered, the step between the previously formed metal powder layer and the metal layer is measured, and the amount of the base metal body lowered is determined.

In the metal laminated molding method according to the present invention, when the base metal body is lowered only between the second layer and the predetermined Nth layer, a step between the previously formed metal powder layer and the metal layer is formed. The amount of descent of the base metal body is determined by measurement. Therefore, it is possible to provide a metal laminated molding method capable of suppressing a decrease in the molding speed while improving the molding accuracy.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to suppress a decrease in the modeling speed while improving the modeling accuracy of a metal body having a three-dimensional structure.

It is a schematic front view of the metal laminated molding apparatus used in the metal laminated molding method which concerns on embodiment. It is a functional block diagram of the metal laminated molding apparatus used in the metal laminated molding method which concerns on embodiment. It is a flowchart which shows the series flow of the metal laminated molding method which concerns on embodiment. It is an enlarged view of the region shown by IV of FIG. It is a photograph which shows the cube which was modeled by the metal laminated modeling method which concerns on Example and the comparative example.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. In addition, the drawings have been simplified as appropriate to clarify the explanation.
As a matter of course, the right-handed xyz coordinates shown in FIGS. 1, 4 and 5 are for convenience in explaining the positional relationship of the components. Usually, the z-axis plus direction is vertically upward, and the xy plane is a horizontal plane.

<Embodiment>
In this embodiment, a metal body having a desired three-dimensional structure (three-dimensional structure) is formed. First, slice data is produced by slicing three-dimensional CAD (computer-aided design) data of a desired metal body. Based on the slice data for each layer produced, a metal layer obtained by sintering metal powder layer by layer is formed by using the metal laminating modeling apparatus 1, and finally a metal body having a three-dimensional structure is formed.

First, with reference to FIG. 1, a metal laminating modeling apparatus used in the metal laminating method according to the present embodiment will be described.
FIG. 1 is a schematic front view of the metal laminated molding apparatus 1 used in the metal laminated molding method according to the embodiment. As shown in FIG. 1, the metal laminated molding apparatus 1 includes a base metal body 11, a molding chamber 12, a powder supply unit 13, a recoater 14, a powder spreading blade 15, a laser irradiation unit 16, a non-contact sensor 17, and a base metal. A body drive shaft 18 (not shown) and a control unit 20 (not shown) are provided.

As shown in FIG. 1, the base metal body 11 is a member that serves as a base for laminating the metal powder S, and is a member used as a part of the metal body having a three-dimensional structure in the present embodiment. The modeling chamber 12 is, for example, a rectangular parallelepiped, and is a container for accommodating the base metal body 11. A recess is formed on the upper surface of the modeling chamber 12, and the base metal body 11 is housed in the recess.

As shown in FIG. 1, the powder supply unit 13 is a powder supply source for supplying the metal powder S onto the base metal body 11. The powder supply unit 13 is, for example, a hopper. The powder supply unit 13 supplies the metal powder S in the downward direction (z-axis negative direction) of the powder supply unit 13, for example, by rotating a valve provided at the bottom of the powder supply unit 13. do. However, the device is not limited to this as long as it can supply the metal powder S in a predetermined amount at a time.

As shown in FIG. 1, a recoater 14 is arranged at the bottom of the powder supply unit 13. Since the upper surface and the lower surface of the recoater 14 are open and the inside is a hollow cone shape, the metal powder S passes through the inside of the recoater 14. The recorder 14 can move in the horizontal direction (xy direction).

As shown in FIG. 1, the powder spreading blade 15 is arranged at the tip of the recoater 14. As the recoater 14 moves horizontally, the powder spreading blade 15 transports the metal powder S to the upper surface of the base metal body 11 while leveling the metal powder S supplied from the powder supply unit 13. As shown in FIG. 1, the non-contact sensor 17 is arranged on the side surface of the recoater 14.

The non-contact type sensor 17 in the present embodiment uses a laser type displacement sensor, but it may be a non-contact type and can measure a step between the metal powder layer SL and the metal layer M. Not limited to. In the present embodiment, the non-contact type sensor 17 is arranged on the side surface of the recoater 14, but a non-contact type sensor that operates separately from the recoater 14 may be separately arranged.

As shown in FIG. 1, the laser irradiation unit 16 is arranged on the upper portion of the base metal body 11 in the positive direction of the z-axis. The laser irradiation unit 16 irradiates the metal powder layer SL with the laser L based on the slice data registered in advance in the control unit 20, and sintered the metal powder layer SL to form the metal layer M.

Next, the configuration of the metal modeling apparatus will be described with reference to FIG.
FIG. 2 is a functional block diagram of a metal laminated molding apparatus used in the metal laminated molding method according to the embodiment. The control unit 20 controls the powder supply unit 13, the recoater 14, the laser irradiation unit 16, the non-contact sensor 17, and the base metal body drive shaft 18. The control unit 20 stores slice data obtained by slicing three-dimensional CAD data of a desired metal body.

Next, with reference to FIG. 3, a series of flow of the metal laminated molding method will be described.
FIG. 3 is a flowchart showing a series of flows of the metal laminated molding method according to the embodiment. First, the base metal body is lowered (step S1). Next, a metal powder layer is formed on the base metal body (step S2). Next, the formed metal powder layer is sintered to form a metal layer (step S3). Next, it is determined whether or not a predetermined N layer has been formed (step S4). Only between the second layer and the predetermined Nth layer, when the base metal body is lowered, the step between the formed metal powder layer and the metal layer is measured and acquired (step S5). Then, the amount of descent of the base metal body is determined according to the acquired step (step S6). The above steps are repeated to form a metal body having a three-dimensional structure.

Hereinafter, each of the above steps will be described with reference to FIGS. 3 and 1.
<Step S1: Lowering of the base metal body>
In step S1, the base metal body 11 is lowered. Before the start of laminating the metal powder S, the upper surface (xy plane) of the base metal body 11 and the uppermost surface (xy plane) of the modeling chamber 12 are located on the same plane. The amount of descent of the base metal body 11 of the first layer is set according to the desired stacking pitch of the metal powder S. The stacking pitch can be appropriately changed according to the desired processing accuracy. Further, the amount of descent of the base metal body from the second layer to the predetermined N (N is an integer larger than 2) layer will be described later in steps S5 and S6.

<Step S2: Formation of metal powder layer>
In step S2, the metal powder S is laminated to form the metal powder layer SL. Specifically, the metal powder S for one layer of slice data prepared in advance is supplied to the recess formed by the base metal body 11 lowered in step S1 and the modeling chamber 12, and the metal powder layer SL is supplied. To form.

First, a predetermined amount of the metal powder S is supplied from the powder supply unit 13 to a part of the upper surface of the modeling chamber 12. The predetermined amount in the present embodiment is an amount set according to a desired stacking pitch of the metal powder S, and is supplied from the powder supply unit 13 in a fixed amount for each layer. The amount of the metal powder S can be appropriately changed according to the desired stacking pitch.

Next, the recorder 14 is moved in the horizontal direction (x-axis positive direction). With the horizontal movement of the recoater 14, the powder spreading blade 15 arranged at the tip of the recoater 14 is based on the metal powder S while leveling the metal powder S supplied to a part of the upper surface of the modeling chamber 12. It is transported to the upper surface of the metal body 11. If excess metal powder S is generated after the metal powder S is transported, it can be transported to a separately provided container or the like by using the powder spreading blade 15 arranged on the recoater 14. Illustrated). When the metal powder S is transported to the upper surface of the base metal body 11 and the upper surface of the modeling chamber 12, the recoater 14 moves again in the horizontal direction (x-axis negative direction) and returns to the original position.

<Step S3: Formation of metal layer>
In step S3, the metal powder layer SL is sintered to form the metal layer M. In the metal laminating molding method of the present embodiment, among the powder bed melting bonds (powder bed method), the laser melting method (Seceltive) in which the metal powder S is irradiated with a laser to melt and sinter the metal powder S is performed. Although laser melting (SLM) is used, an electron beam melting method (Electron Beam Melting, EBM) or the like may be used.

As shown in FIG. 1, the laser irradiation unit 16 irradiates the metal powder layer SL with the laser L based on the slice data registered in advance in the control unit 20, and the metal powder layer SL is sintered. , A metal layer M is formed. As shown in FIG. 1, when the metal powder layer SL is sintered, the formed metal layer M becomes thinner than the metal powder layer SL. That is, a step is formed between the metal powder layer SL and the metal layer M, and the metal layer M becomes a recess with respect to the metal powder layer SL.

<Step S4: Determination of N layer formation>
In step S4, it is determined whether or not a predetermined N layer has been formed. In the case of N layers or less (step S4: NO), the process proceeds to the measurement of the step between the metal powder layer and the metal layer (step S5), and steps S1 to S6 are repeated until the N layer is formed.
On the other hand, when the N layer is formed, that is, when the N + 1 layer or later (step S4: YES), steps S5 and S6 are completed, and the process returns to step S1 (descending of the base metal body) to reduce the amount of the base metal body descending. It is fixed and steps S1 to S3 are repeated.

Here, the "predetermined N layer" in the present embodiment will be described. In the present embodiment, the metal body P is formed by lowering the base metal body 11 layer by layer. After the N + 1 layer, the thickness of each formed metal layer becomes constant without changing the amount of descent of the base metal body 11. Here, N is equal to the number of times the base metal body 11 descends.

In the present embodiment, N, that is, the number of times the base metal body 11 for measuring the step is lowered is determined in advance, and then the base metal body 11 is lowered, but the present invention is not limited to this. For example, in the following steps S5 and S6, if the step formed between the previously formed metal powder layer SL and the metal layer M is measured and the step is stably within a predetermined step several times. After that, N may be determined so as not to measure.

<Step S5: Measurement of the step between the metal powder layer and the metal layer>
In step S5, the step h between the metal powder layer SL and the metal layer M is measured and acquired. FIG. 4 is an enlarged view of the region shown by IV in FIG.

As shown in FIG. 4, the non-contact sensor 17 arranged on the recoater 14 is used to measure and acquire the step h in the z-axis direction between the previously formed metal powder layer SL and the metal layer M. Specifically, the recoater 14 returned to the original position in step 2 is moved in the horizontal direction (x-axis positive direction) again without supplying the new metal powder S, and is not disposed on the recoater 14. The step h is acquired by using the contact type sensor 17.

<Step S6: Determination of the amount of descent of the base metal body>
In step S6, the amount of descent of the base metal body 11 is determined based on the step h acquired in step S5. Specifically, the control unit 20 determines the amount of descent of the base metal body 11 based on the step h acquired from the non-contact sensor 17. Next, returning to step S1, the control unit 20 controls the base metal body drive shaft 18 based on the determined descent amount, and lowers the base metal body 11.

In the conventional metal laminated molding method, there is a problem that the thickness of each formed metal layer is not constant at the molding start stage, and sufficient molding accuracy cannot be obtained.
In order to make the thickness of the metal layer constant and improve the molding accuracy, it is conceivable to make the thickness of each metal powder layer constant. Here, if the step between the formed metal powder layer and the metal layer is measured and the amount of descent of the base metal body is determined based on this measured value, the thickness of each metal powder layer can be made constant. can. However, when such measurement is performed for all layers, there is a problem that the modeling speed is lowered.

In the present embodiment, when the base metal body is lowered only between the second layer and the predetermined Nth layer, the step between the previously formed metal powder layer and the metal layer is measured to measure the base metal body. The amount of descent is determined. That is, in determining the amount of descent of the base metal body, the step between the previously formed metal powder layer and the metal layer is acquired until the thickness of the metal powder layer becomes constant for each layer, not for all layers. It is done only during the period. Therefore, it is possible to suppress a decrease in the modeling speed while improving the modeling accuracy of the metal body having a three-dimensional structure. Further, since the molding accuracy can be improved, the formation of internal defects near the boundary between the base metal body and the molded metal body can be suppressed. Further, since the formation of internal defects in the molded portion can be suppressed, fatigue fracture of the product due to internal defects can be suppressed.

The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit.

Next, examples of the present invention will be described.
Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

FIG. 5 is a photograph showing a cube formed by the metal laminated molding method according to Examples and Comparative Examples. In both Examples and Comparative Examples, aluminum powder was used as the metal powder S. The metal powder S having a particle size of 40 to 63 μm was used. A cubic metal body having a side of 10 mm was formed on each of the base metal body 11 and the base metal body 101.

In the embodiment, the control unit 20 determines the amount of descent of the base metal body 11 only between the second layer and the 100th layer, that is, until the step h acquired from the non-contact sensor 17 becomes constant. went. The step h was acquired using the non-contact sensor 17 with a resolution of 5 μm and a measurement time of 10 seconds. After the step h became constant, steps S4 and S5 were completed, and the steps S1 to S3 were repeated to form the metal body P1. The modeling time was 130 minutes. In the metal body P1 according to the embodiment formed in this way, as shown in FIG. 5, the metal body P1 having few internal defects and high density near the boundary between the base metal body 11 and the laminated metal body P1. I was able to get.

On the other hand, in the comparative example, the amount of descent of the base metal body 101 was fixed at 100 μm, and the metal body P100 was modeled. As shown in FIG. 5, it was obtained that the metal body P100 according to the comparative example formed in this way had many internal defects as a whole. In particular, there are many internal defects near the boundary between the base metal body 101 immediately after the start of laminating the metal powder S and the metal body P100 formed by laminating the metal powder S, and the density of the metal body is lower than that of the examples. Was formed.

From the above, in the embodiment, the amount of descent is determined by the control unit only between the second layer to the 100th layer, that is, until the step h becomes constant, instead of all the layers. While improving the molding accuracy of the metal body, it was possible to suppress the decrease in the molding speed. Further, when the metal body having a three-dimensional structure is formed by the metal laminated molding method according to the example, the density is higher than that in the comparative example, and the metal having few internal defects near the boundary between the base metal body and the formed metal body. I was able to get a body.

1 Metal laminated molding device 11 Base metal body 12 Modeling chamber 13 Powder supply unit 14 Ricator 15 Powder laying blade 16 Laser irradiation unit 17 Non-contact sensor 18 Base metal body drive shaft 20 Control unit L Laser M Metal layer P Metal body S Metal powder SL Metal powder layer

Claims (2)

The process of lowering the base metal body and
The step of forming a metal powder layer on the base metal body and
It is a metal lamination molding method for forming a metal body having a three-dimensional structure by repeating the steps of sintering the formed metal powder layer to form a metal layer and sequentially laminating the metal layers. ,
When lowering the base metal body only between the second layer and the predetermined Nth layer (N is an integer larger than 2 and less than the total number of laminated layers ) .
The step difference between the previously formed metal powder layer and the metal layer is measured to determine the amount of descent of the base metal body.
Metal laminate modeling method. While measuring the step formed between the previously formed metal powder layer and the metal layer, if the step is stably within a predetermined step a predetermined number of times, N is set so as not to be measured thereafter. The metal laminated molding method according to claim 1, which is determined.

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