JP4519560B2 - Additive manufacturing method - Google Patents

Description

  The present invention relates to an additive manufacturing method, and more particularly to an additive manufacturing method for forming an intended three-dimensional shape using powder as a material.

  Conventionally, a solid shape created by CAD (Computer Aided Design) has been materialized by a rapid prototyping (hereinafter referred to as “RP”) system in various fields. In particular, the RP system using the layered manufacturing method has a high degree of freedom in processing while being a simple device as compared with a machining center or the like. The additive manufacturing method having such advantages has been widely applied to materials made of resin or paper, but there are problems in terms of strength, aging and aging. For this reason, research of three-dimensional modeling by a layered modeling method using a metal or the like as a material has been actively promoted.

  Among the three-dimensional additive manufacturing using such metals as materials, (a) after applying a resin to the surface of the material powder such as metal, it was heated and melted by laser irradiation. The resin part is made to function as an adhesive and the cross-sectional elements are sequentially laminated to form a solid, or (b) a material powder such as metal is directly heated and melted by one type of laser irradiation to form a continuous body. A method has been proposed. In such a method, a predetermined region is melted by laser irradiation and solidification occurs in the melted portion. However, only with such melting and solidification, cavities and resin remain inside the shaped solid, and sufficient strength cannot be obtained. Therefore, the volatilization of the residual resin component in the high-temperature atmosphere and the local bonding of the material particles are promoted to be in a sintered state, or a material having a melting point lower than that of the metal used is dissolved and penetrated into the cavity. Therefore, post-treatment is required, and the strength is improved by such post-treatment.

  On the other hand, recently, a layered manufacturing method for metals and the like that can achieve high strength without requiring post-treatment such as sintering or a low melting point material has been proposed (see Non-Patent Document 1; Called Example 1). In this conventional layered manufacturing method, as shown in FIG. 8, first, a material powder 91 is supplied (see FIG. 8A). FIG. 8A shows an example in which a material powder 91 for a layer to be newly layered is supplied onto a compressed material body 98 in which a part of the target shape has already been layered and modeled. ing.

  Subsequently, the material powder 91 is flattened using a blade or the like to form the material powder layer 92 (see FIG. 8B). Then, the material powder layer 92 is compressed with a high pressure P to form a compressed material layer 93 (see FIG. 8C).

  Next, the region of the compression material layer 93 corresponding to the design cross-sectional shape at the position of the compression material layer 93 in the target three-dimensional stacking direction (+ Z direction) is irradiated with a relatively low power laser beam L1. As a result, the material in the irradiated region is heated and melted. And the irradiation of the laser beam L1 to the fusion | melting part is stopped, and it solidifies. As a result, a cross-sectional element 95 is formed in the compressed material layer 93 (see FIG. 8D). The material is locally melted and solidified continuously by scanning the region of the compressed material layer 93 corresponding to the design cross-sectional shape with the laser beam L1 at an appropriate speed.

  Next, the laser beam L2 having a higher power than the laser beam L1 is irradiated to the cross-sectional element 95 and heated, so that the already layered part and the cross-sectional element are integrated. As a result, a layered product 97 in which the cross-sectional elements 95 are newly stacked is formed (see FIG. 8E). Thereafter, in the same manner as described above, the target three-dimensional shape is formed with high strength by sequentially proceeding the layered modeling.

  In addition, a technique that omits the step of compressing the material powder layer at a high pressure P in the above-described conventional example 1 is also proposed (see Non-Patent Document 2; hereinafter referred to as “Conventional Example 2”).

Tokunaga et al. “Three-dimensional modeling using pure iron powder material by two-step laser irradiation method” Journal of Precision Engineering, Vol. 65, No. 8, pp. 1136-1140, August 5, 1999 Tokunaga et al. "High-strength modeling of metal powders using lasers-Melt-bonding characteristics of powders" FY2002 Annual Meeting of the Japan Society for Precision Engineering 480th page, September 10, 2002

  The additive manufacturing method of the above-mentioned conventional example 1 and conventional example 2 promotes volatilization of residual resin components and local bonding of material particles in a high-temperature atmosphere so far, and a sintered state is used. Compared to a layered manufacturing method that requires post-processing such as dissolving a low-melting-point material rather than the material and allowing it to penetrate into the cavity, it is very excellent in that no post-processing is required. However, in the conventional example 1, the process of compressing the material powder layer along the stacking direction with a very high pressure, for example, on the order of 100 MPa is essential. For this reason, in order to form a high-strength solid using the additive manufacturing method of the prior art, a large-scale compression device is required, and a movable stage that is a place where the material powder layer is formed is also like this. It was necessary to be able to withstand high pressures. As a result, the additive manufacturing apparatus that employs the additive manufacturing method of the prior art has to be large-scale. Therefore, it is difficult to easily form a high-strength solid depending on the prior art.

  Moreover, in the prior art example 2, there is no need for the post-processing as described above, and there is no need for a step of compressing the material powder layer along the laminating direction with a very high pressure, but the shaping that is finally achieved The filling factor in the body was about 60 to 70%. Here, the “filling rate” refers to the ratio of the volume to the total volume obtained by subtracting the volume of the void from the total volume. That is, when the porosity is α, the filling rate is defined by (1−α). For this reason, the realization of the further high intensity | strength by the improvement of the further filling rate was desired.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an additive manufacturing method capable of easily and quickly forming a high-strength solid.

The additive manufacturing method of the present invention is an additive manufacturing method for forming a desired three-dimensional shape using pure iron or an iron-based alloy powder as a material, and has a predetermined thickness determined according to the type of material powder. A material layer forming step of forming a material powder layer obtained by flattening the material powder; and a region of the material powder layer corresponding to a design cross-sectional shape of a stacking position of the material powder layer in the target three-dimensional shape, A cross-section element forming step of scanning with a first laser beam, locally heating and melting and then solidifying to form a cross-section element; and scanning the cross-section element with a second laser beam, which is a pulsed laser beam, An integration step of integrating the already shaped part and the cross-sectional element by heating to a pulsed laser beam and a third laser beam having a peak power higher than that of the second laser beam. In the process Ri scans the integrated cross sectional element, the integrated and surface shaping step for shaping the surface of the cross sectional element; repeatedly, a laminate molding method for molding a three-dimensional shape to the object, the first laser The light is light after continuous wave laser light having a beam diameter d ₁ [mm] passes through a condensing optical system having a focal length f ₁ [mm], and the thickness t [mm] of the powder material layer is: When the distance between the focal position of the first laser beam and the surface of the powder material layer is z ₁ [mm],
t = k · ω ₁ = k · z ₁ · d ₁ / (2f ₁ )
Here, 3.2 ≦ k ≦ 4.0
The power PM [W] and the scanning speed v [mm / s] of the first laser beam are as follows:
PM = A ・ v + B
Here, 10 <A <11, 25 <B <40
The second laser beam satisfies the above condition, and the pulse laser beam having the beam diameter d ₂ [mm], the peak power PW [W], and the pulse width of 8 to 12 [ms ] is condensed with the focal length f ₂ [mm]. It is the light after passing through the optical system, and the peak power PW [W] is obtained when the distance between the focal position of the second laser beam and the surface of the cross-sectional element is z ₂ [mm] Assuming that constant a is 600 and constant b is 470,
PW = a · ω ₂ + b = a · z ₂ · d ₂ / (2f ₂ ) + b
Together satisfy the, one pulse at a distance of (omega _2/2), the second laser beam is sequentially irradiated to the cross sectional element is a layered manufacturing method characterized by.

In this additive manufacturing method, in the material layer forming step, a material powder layer is formed by flattening the material powder to a predetermined thickness determined according to the type of material powder of pure iron or an alloy containing iron as a main component . Subsequently, in the cross-section element forming step, the region of the material powder layer corresponding to the design cross-sectional shape of the material powder layer in the target three-dimensional shape is scanned with the first laser beam that does not substantially scatter the material, It is solidified after being heated and melted.
Here, the first laser light is light after the continuous wave laser light with the beam diameter d ₁ [mm] passes through the condensing optical system with the focal length f ₁ [mm], and the thickness t of the powder material layer [Mm] satisfies the condition of the following expression when the distance between the focal position of the first laser beam and the surface of the powder material layer is z ₁ [mm].
t = k · ω ₁ = k · z ₁ · d ₁ / (2f ₁ )
Here, 3.2 ≦ k ≦ 4.0
The above constant k is such that when the material of the material powder layer is melted, it does not become droplets (granular) due to surface tension, but rather slowly heats a wide area to some extent so that the molten material sinks into the material powder layer. To be elected. In order for the molten material to sink to the material powder layer, it is necessary to make the thickness t more than a certain level. However, if the thickness t is too large, the cross-sectional element becomes too thick, and the shape of the shaped body The accuracy will be lost. According to the knowledge obtained by the inventors from the results of various experiments, when the material of the powder material layer is pure iron or an alloy containing iron as a main component, the constant k is 3.2 ≦ k ≦ 4. It is desirable to satisfy the condition of zero.
Further, the power PM [W] and the scanning speed v [mm / s] of the first laser light satisfy the condition of the following expression.
PM = A ・ v + B
Here, 10 <A <11, 25 <B <40
As described above, when the material of the powder material layer is pure iron or an alloy containing iron as a main component, the melted stage is selected by selecting the constant k, the power PM of the first laser beam, and the scanning speed v. Thus, the molten material does not become droplets (granular) due to the surface tension, and the molten material can sink to the material powder layer.

Next, in the integration step, the cross-sectional element is scanned with the second laser beam, and the already shaped portion and the cross-sectional element are integrated by locally heating. As a result, an intermediate shaped body composed of cross-sectional elements of the same quality as that obtained by the prior art is formed.
Here, the second laser beam is a condensing optical system in which a pulse laser beam having a beam diameter d ₂ [mm], a peak power PW [W], and a pulse width of 8 to 12 [ms] is a focal length f ₂ [mm]. The light after passing through. When the peak power PW [W] is z ₂ [mm] between the focal position of the second laser beam and the surface of the cross-sectional element , the constant a is 600 and the constant b is 470. It chooses to satisfy the following formula.
PW = a · ω ₂ + b = a · z ₂ · d ₂ / (2f ₂ ) + b
Thus the second laser beam having a peak power selected, one by one pulse at a distance of (omega _2/2), sequentially, is irradiated to the cross-sectional element, the cross-sectional element that is newly formed, already shaped Can be firmly integrated with each other.

Next, in the surface shaping process, the integrated cross section is scanned by scanning the cross sectional element integrated by the integration process with the third laser light which is pulsed laser light and whose peak power is higher than that of the second laser light. Shaping is performed to remove the closed recesses on the surface of the element, and the surface of the integrated cross-sectional element is smoothed. For this reason, the powder in the material powder layer formed by the material layer formation process performed for modeling of the next layer can be equalized, and the generation of voids generated in the final modeled body can be reduced. As a result, the filling rate in the final shaped body can be improved to 90% or more, and the integration between the cross-sectional element and the already shaped part is also strong.

  Thereafter, by repeatedly performing the material layer forming step, the cross-sectional element forming step, the integration step, and the surface shaping step, the intended three-dimensional shape is formed with high strength.

  Therefore, according to the layered manufacturing method of the present invention, a high-strength solid can be modeled easily and quickly.

In the additive manufacturing method of the present invention, in the surface shaping step, the peak power of the third laser beam can be changed according to the scanning position. In this case, by changing the peak power of the third laser light according to the scanning position, the degree of scattering of a part of the material near the surface in the integrated cross-sectional element according to the scanning position is adjusted. Can do. For this reason, the surface of the integrated cross-sectional element can be flattened, or fine processing can be performed so that the uneven shape near the surface has a desired fine structure.

  In the additive manufacturing method of the present invention, when the linear region adjacent to the specific linear region is scanned by the first laser light after the specific linear region is scanned by the first laser light, the specific laser 40 to 60% of the linear regions can be included in the adjacent linear regions. By simply scanning the specific linear region with the first laser beam, the cross-sectional shape perpendicular to the scanning direction of the shaped object formed by the scanning becomes a bow, and a cross-sectional element having a uniform thickness cannot be formed. However, when the linear region adjacent to the specific linear region is scanned with the first laser light, 40 to 60% of the specific linear region is included in the adjacent linear region. A uniform plate-like cross-sectional element can be formed. Here, if the ratio of the area of the overlapping region of the specific linear region and the adjacent linear region to the specific linear region is small, the unevenness of the thickness of the cross-sectional element becomes large, and when this proportion increases. Although the time required for the cross-section forming process becomes long, when this ratio is 40 to 60%, the cross-section element can be formed quickly while suppressing the occurrence of uneven thickness of the cross-section element.

In the additive manufacturing method of the present invention, a fourth laser beam that is a pulse laser beam and has a peak power higher than that of the third laser beam is irradiated between the integration step and the surface shaping step. The cutting step of cutting the cross-sectional element so as to have the designed cross-sectional shape may be further provided.
Here, the fourth laser beam is a surface of the cross-sectional element that has an average power PC [W], a pulse width of several hundreds [ns], and a pulse frequency of 1 to 3 [kHz] via a focusing optical system. The light can be condensed. When the average power PC [W] is the scanning speed vc [mm / s], it is preferable that the constant c is 5 to 15 and the constant d is 15 to 25 so that the following equation is satisfied. .
PC = c · vc + d

In this case, after the integrated cross-sectional element is formed, the shape of the cross-sectional element formed before the next cross-sectional element is formed can be matched with the design cross-sectional shape with high accuracy. For this reason, the target three-dimensional shape can be accurately modeled.

  As described above, according to the layered manufacturing method of the present invention, there is a remarkable effect that a high-strength solid can be modeled easily and quickly.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a schematic configuration of an additive manufacturing system 10 that performs an additive manufacturing method according to an embodiment of the present invention. As shown in FIG. 1, the additive manufacturing system 10 includes (a) a computer system 20 for designing a target solid shape and storing design data, and (b) under the control of the computer system 20. A laser irradiation device 30A for generating continuous light or pulsed light; (c) a laser irradiation device 30B for generating pulsed light under the control of the computer system 20; and (d) under control of the computer system 20. And a stage device 40 having a stage 41 that can move in the three axial directions of the X-axis direction, the Y-axis direction, and the Z-axis direction.

  The computer system 20 executes (i) various programs such as a three-dimensional design program, and also controls a processing device 21 that controls the entire additive manufacturing system 10, and (ii) a figure or a pattern according to a command from the processing device 21. A display device 22 for displaying characters and the like; (iii) a stroke device 23 such as a keyboard for an operator to input commands and character data to the processing device 21; and (iv) an operator for the processing device 21 with a display device 22 A pointing device 24 such as a mouse for designating a position in the display area, and (v) a storage device 25 for storing designed solid shape data and the like.

  The laser irradiation device 30A includes (i) a laser oscillator 31A that selectively performs one of continuous light oscillation and pulsed light oscillation in response to a command LCA from the computer system 20 (more specifically, the processing device 21); ii) The laser beam emitted from the laser oscillator 31A is condensed on a predetermined plane in the + Z direction of the stage 41, and the predetermined plane FP (hereinafter referred to as “focal plane FP”) according to the designation from the computer system 20. And an irradiating optical system 32A that changes the light condensing position (focal position). In the present embodiment, the laser oscillator 31A includes a YAG laser that can output continuous light with a maximum power of 100 W, and a pulsed light output unit (Q switch pulse unit) that can be added to the YAG laser. . The computer system 20 controls ON / OFF of the laser light output by controlling the YAG laser, and switches between continuous light and pulsed light by controlling the pulse light output unit. . Here, when the laser irradiation apparatus 30A receives a pulse light generation command from the computer system 20, the laser irradiation apparatus 30A has a repetition frequency of 1 to 3 [kHz] and a width of several hundred [ns] to several hundred [ns] by the Q switch method. kW] to several [MW] peak light is emitted.

In the present embodiment, in the irradiation optical system 32A, the focal length f _{1 of the} condensing lens at the final stage is about 100 [mm] in both cases of continuous light and pulsed light. In addition, the beam diameter d ₁ is about 10 [mm] immediately before entering the final stage condenser lens.

  The continuous light emitted from the laser irradiation device 30A is used as a laser light L1 described later. Further, pulsed light emitted from the laser irradiation device 30A is used as laser light L3 and laser light L4 described later.

  The laser irradiation device 30B includes (i) a laser oscillator 31B that performs pulsed light oscillation of a normal pulse in response to a command LCB from the computer system 20 (more specifically, the processing device 21), and (ii) an emission from the laser oscillator 31B. The irradiated optical system 32B that condenses the laser beam thus formed on a predetermined plane in the + Z direction of the stage 41 and changes the condensing position (focal position) on the focal plane FP in accordance with the designation from the computer system 20. And. In the present embodiment, the laser oscillator 31B has a YAG laser that can output pulsed light. Note that the pulsed light emitted from the laser irradiation device 30B is used as a laser light L2 described later.

In the present embodiment, in the irradiation optical system 32B, the focal length f _{2 of the} final stage condensing lens is about 100 [mm]. In addition, the beam diameter d ₂ is about 10 [mm] immediately before entering the final stage condenser lens.

  The stage device 40 includes (i) the stage 41 described above, and (ii) a drive device that drives the stage 41 in the three-axis directions of XYZ in response to a command STC from the computer system 20 (more specifically, the processing device 21). 42. On the stage 41, a base plate 43 having sufficient heat resistance is placed.

  Next, the operation of additive manufacturing by the additive manufacturing system configured as described above will be described.

  First, the designer uses the computer system 20 to design a target three-dimensional shape. Such a design work is performed by the designer operating the stroke device 23 and the pointing device 24 while referring to the display on the display device 22 in a state where the three-dimensional CAD program is executed by the processing device. The data of the solid shape designed in this way, and the data of the cross-sectional shape of each slice part when the solid is sliced with a thickness in a predetermined vertical direction (Z direction) on a horizontal plane (a plane parallel to the XY plane), It is stored in the storage device 25. In the present embodiment, as shown in FIG. 2, the designed solid is a square frame having an XY cross-sectional shape along the Z direction (a part of the square frame is removed on the + Z direction side). ) Is a solid OBJ in which the length of one side is changed.

  As described above, when the CAD design is completed, the computer system 20 controls the driving device 42 so that the base plate 43 on the stage 41 is on the −Z direction side of the injection position of the laser irradiation device 30A. Move.

Next, the material powder 51 ₁ for the first layer is supplied onto the + Z direction side surface of the base plate 43 (see FIG. 3A). In this embodiment, Ni-Mo alloy steel (KIP Sigmaloy 415 (trade name) manufactured by Kawasaki Steel Corporation) in which about 40% of the grain system is concentrated in 100 to 200 μm is used as the material powder 51 ₁ ,. ing. The material powder 51 _1, as is ..., in addition to Ni-Mo alloy steel, may be used, such as pure iron metals and alloys.

Subsequently, the material powder 51 ₁ is flattened by using a blade or the like to form the material powder layer 52 ₁ (see FIG. 3B). The thickness t of the material powder layer 52 ₁ is the type of material powder 51 _1, and in accordance with the irradiation conditions of the material powder layer 52 ₁ of the laser beam L1 to be described later are those determined appropriate value. That is, the thickness t is determined by the following equation (1), where k is a constant determined for each material.
t ≦ k · ω ₁ = k · z ₁ · d ₁ / (2f ₁ ) (1)

Here, when the kind of the material powder 51 ₁ is an alloy containing iron as a main component (a component occupying 50% or more of the composition) as in this embodiment, a value satisfying 3.2 ≦ k ≦ 4.0. It is desirable to select k. Note that the range of the value k is the same when the type of the material powder 51 ₁ is pure iron.

In the present embodiment, the distance z ₁ (defocus amount) is set to 5 [mm], and the thickness t of the material powder layer 52 ₁ is set to 1 [mm] where the constant k is 4.

Next, the computer system 20 controls the driving device 42 to move the stage 41 in the Z-axis direction so that the Z position of the material powder layer 52 ₁ is on the −Z direction side by about 5 [mm] from the focal plane FP. Let Subsequently, by the computer system 20 controls the laser irradiation apparatus 30A, performs local heating by irradiation with a laser beam L1 in an area corresponding to the design cross-sectional shape in the material powder layer 52 _1. Here, the scanning speed v [mm / s] for scanning the region corresponding to the designed cross-sectional shape by the laser light L1 for performing the local heating by the irradiation of the laser light L1, and the power PM [W of the continuous laser light L1. ] Is determined by the condition of the following equation (2).
PM = A · v + B (2)
Here, 10 <A <11, 25 <B <40

  In this embodiment, the constant A is 10.8, the constant B is 30, the scanning speed v is 2.8 to 3.7 [mm / s], and the power PW of the laser light L1 is 60 to 70 [W]. Thus, the condition of the above equation (2) is satisfied.

The material powder layer 52 ₁ that satisfies the conditions of the thickness t, is irradiated with laser light L1 at a scanning speed satisfies the condition of the above equation (2) v [mm / s] and power PM [W] Thus, the irradiated region of the material powder layer 52 ₁ does not become droplets (granular) due to surface tension at the stage of melting, and the molten material sinks into the material powder layer.

Further, when the laser beam L1 material powder layer 52 ₁ of the scanning by, after scanning of the linear region, a linear region adjacent to the linear region when scanned by the laser beam L1 is approximately of the linear region 50% is included in the adjacent linear region. This is because, when scanning, there is no overlap between adjacent irradiation areas of the laser light L1 in the direction perpendicular to the scanning direction, the cross-sectional shape perpendicular to the scanning direction of the cross-sectional element formed by the scanning of the laser light L1 becomes a bow. This is because a cross-sectional element having a uniform thickness cannot be formed. In order to prevent such a cross-sectional shape from becoming a bow, the ratio of the overlapping portion between the linear region and the adjacent linear region may be 40% or more. Further, in order to quickly form the cross-sectional element, it is preferable that the ratio of the overlapping portion is 60% or less.

In the above conditions, the laser light L1, by scanning in a region corresponding to the design cross-sectional element 55 ₁ of the first layer is formed (see FIG. 3 (C)). The YZ cross section of the formed cross-sectional element 55 portion extending along _one of the X-axis direction in this way is shown in FIG. 4 (A). As representatively shown in this FIG. 4 (A), the cross sectional element 55 ₁ is the boundary portion between the area where the laser light L1 is not irradiated with the irradiation region becomes the shape as of the end of the crescent . The Z-axis direction thickness of the cross-sectional element 55 ₁ is about 30% of the Z-axis direction thickness of the material powder layer 52 ₁ .

Returning to Figure 3, then the computer system 20 controls the laser irradiation apparatus 30A, the pulse light L3, cross sectional shape corresponding to the Z position of the cross sectional element 55 ₁ in the stereoscopic OBJ, ie design cross-section in the first layer The cross-sectional element 55 ₁ is scanned along the contour of the shape, and the cross-sectional element 55 ₁ is cut. Here, when such cutting, the laser light L3, one hundred pulse width of several [ns], a pulse laser beam having a pulse frequency 1 to 3 [kHz], the cross sectional element 55 ₁ surface to the focal plane of the laser beam L3 de When the focus amount is about 0 [mm], when the average power PC [W] and the scanning speed vc [mm / s] in the second unit of the laser light L3 satisfy the condition of the following expression (3): accurately cross sectional element 55 ₁ is disconnected.
PC = c · vc + d (3)
Here, c is 5 to 15, d is 15 to 25

  In the present embodiment, the scanning speed vc is set to 1 [mm / s] and the average power PC is set to 20 to 40 [W] so as to satisfy the condition of the expression (3).

The irradiation of such laser beam L3, cross sectional element 55 ₁ is cut along the contour of the design cross-sectional shape in the first layer, shaping the cross-sectional element 57 ₁ is formed (see FIG. 3 (D)). The shaping section element 57 ₁ is precisely matches the design cross-sectional shape in the first layer. The shaping section element 57 ₁ of the Z-axis and of a section along a plane parallel shape, a YZ cross-sectional view of a portion shaped cross-sectional element 57 ₁ extends along the X-axis direction are representatively shown in FIG. 4 (B).

Returning to Figure 3, then the computer so that the system 20 controls the drive unit 42 the Z position of the shaping cross-sectional element 57 ₁ is about 5 [mm] by -Z direction from the focal plane FP, the stage 41 Move in the Z-axis direction. Subsequently, the computer system 20 controls the laser irradiation apparatus 30A, by scanning the surface of the shaping cross-sectional element 57 ₁ by the pulse light L4, to remove the indentation was about to be closed at the surface of the shaping cross-sectional element 57 ₁ smoothness Surface shaping is performed. At this time, simultaneously with the removal of the depression was about to be closed, by changing in accordance with the peak power of the laser beam L4 to the scan position, varying degrees to scatter a portion of the material near the surface of the shaping cross-sectional element 57 ₁ be able to. As a result, the material can be scattered by a desired amount in accordance with each scanning position. Therefore, it freely be or to planarize the surface of the shaping cross-sectional element 57 _1, irregularities in the vicinity of the surface to or perform fine processing to have a desired microstructure. In the present embodiment, the scanning with the laser light L4, is set to be performed to planarize the shaping cross-sectional element 57 ₁ of the surface.

The irradiation of such laser beam L4, (see FIG. 3 (E)) surface shaped cross-sectional element 58 ₁ having a flattened is formed, and shaped bodies at this stage. The cross-sectional shape by the Z axis and parallel to the plane of the shaped body 58 _1, a YZ cross-sectional view of a portion shaped bodies 58 ₁ extends along the X-axis direction are representatively shown in FIG. 4 (C). The material in the material powder layer 52 ₁ (see FIG. 5B) for shaping the next layer is obtained by smoothing the surface of the shaped cross-section element 57 ₁ (in the case of this layer, flattening). It is possible to equalize the powder, and consequently improve the filling rate of the final shaped body.

Next, the material powder 51 ₂ for the second layer is supplied onto the + Z direction side surface of the material powder layer 52 ₁ (see FIG. 5A). Subsequently, using a blade or the like, a material powder 51 ₂ is planarized to form a material powder layer 52 ₂ (see FIG. 5 (B)). The thickness of the material powder layer 52 ₂ is in the thickness of the same as in the case of the material powder layer 52 ₁ described above.

Next, in the same manner as shown in FIG. 4 (C) described above, the computer system 20, Z position of the material powder layer 52 ₂ is only 5 [mm] from the focal plane FP controls the drive unit 42 -Z direction The stage 41 is moved in the Z-axis direction so as to be on the side. Subsequently, the computer system 20 controls the laser irradiation apparatus 30A to irradiate the region corresponding to the design cross-sectional shape in the material powder layer 52 ₂ with the laser beam L1 in the same manner as in the case of the material powder layer 52 _1. Heat. As a result, cross-sectional element 55 ₂ of the second layer is formed (see FIG. 5 (C)). The YZ cross section of the formed cross-sectional element 55 portion extending along _one of the X-axis direction in this way is shown in FIG. 6 (A). As representatively shown in FIG. 6A, the cross-sectional element 55 ₂ has a crescent-shaped boundary between the region irradiated with the laser light L1 and the region not irradiated with the cross-sectional element 55 ₁ . It has a shape like an end.

Next, the computer system 20 controls the driving device 42 to move the stage 41 so that the base plate 43 on the stage 41 is on the −Z direction side of the emission position of the laser irradiation device 30B. Subsequently, the computer system 20 controls the drive unit 42, so that the cross-sectional element 55 ₂ is only -Z direction side 5 [mm] from the focal plane FP, moves the stage 41 in the Z-axis direction. Then, the computer system 20 controls the laser irradiation device 30B, by scanning the pulsed laser beam L2 by the cross sectional element 55 ₂ in the formation region, performs a localized heating, the cross-sectional element 55 _2, until it It is integrated by welding the shaped bodies 58 ₁ (see FIG. 5 (D)).

The peak power PW [W] of the laser beam L2 for such welding is generally determined by the following equation (4).
PW = a · ω ₂ + b = a · z ₂ · d ₂ / (2f ₂ ) + b (4)
Here, a is 600, b is 470

In the present embodiment, the pulse width of the laser beam L2 is set to 8 to 12 ms, and the peak power PW is set to 560 to 650 [W] so that the condition of the expression (4) is satisfied. Then, the laser beam L2, one pulse at a distance of (omega _2/2), sequentially, and irradiating the cross-sectional element 55 _2.

The irradiation of such laser light L2, it until the shaped body 58 ₁ and the cross sectional element 55 ₂ of, integrated firmly. The cross-sectional shape by the Z axis and parallel to a plane in the integrated state, representatively shown in FIG. 6 (B) as a YZ cross-sectional view of a portion laminate 57 ₂ extends along the X-axis direction.

Returning to FIG. 5, next, the computer system 20 controls the driving device 42 to move the stage 41 so that the base plate 43 on the stage 41 is on the −Z direction side of the injection position of the laser irradiation device 30A. Subsequently, the computer system 20 controls the drive unit 42, as cross sectional element 55 ₂ is substantially coincident with the focal plane FP, moves the stage 41 in the Z-axis direction. By the computer system 20 controls the laser irradiation apparatus 30A, as in the case of cross sectional element 55 _1, the pulsed light L3, cross sectional shape corresponding to the Z position of the cross sectional element 55 ₂ in the stereoscopic OBJ, i.e. the It is scanned by the cross sectional element 55 within ₂ along the contour of the design cross-sectional shape in the second layer, to cut the cross-sectional element 55 _2. As a result, along the contour of the design cross-sectional shape in the second layer is cross sectional element 55 ₂ is cut, shaped cross-sectional element 57 ₂ is formed (see FIG. 5 (E)). The cross-sectional shape by the Z axis and parallel to the plane in this state, as YZ cross-sectional view of a portion shaped cross-sectional element 57 ₂ extends along the X-axis direction are representatively shown in FIG. 6 (C).

Returning to FIG. 5, then the computer so that the system 20 is the Z position of the control to shaping cross-sectional element 57 ₂ the drive unit 42 is about 5 [mm] by -Z direction from the focal plane FP, the stage 41 Z Move in the axial direction. Subsequently, the computer system 20 controls the laser irradiation apparatus 30A, the pulse light L4, by scanning the surface of the shaping cross-sectional element 57 _1, to remove the indentation was about to be closed at the surface of the shaping cross-sectional element 57 ₂ surface shaping, and performs fine processing to the irregular shape in the vicinity of the surface of the shaping cross sectional element 57 ₂ to have a desired microstructure. As a result, the shaped bodies 58 ₂ at this stage is formed (see FIG. 5 (F)). The cross-sectional shape by the Z axis and parallel to the plane of the shaped bodies 58 _2, as YZ cross-sectional view of a portion shaped bodies 58 ₂ extends along the X-axis direction are representatively shown in FIG. 6 (D). As surface treatment of the shaped cross-sectional element 57 ₂ by a laser beam L4, Y-direction central portion of the shaping cross-sectional element 57 ₂ in FIG. 6 (C), together with the planarized, Y-direction end portion of the machining to form a round went.

  Thereafter, the layered modeling of the third and subsequent layers is performed in the same manner as the layered modeling of the second layer. Finally, the target solid OBJ is modeled with high strength and high accuracy.

  A cross-sectional photograph of the layered object formed in this way is shown in FIG. 7A, and a comparative example formed when the laser beam L4 irradiation in FIGS. 3E and 5E is omitted. FIG. 7B shows a cross-sectional photograph of the layered manufacturing body of Conventional Example 2 (that is, Conventional Example 2 described above). While the filling rate of the layered object of the comparative example is 63.1%, the filling rate of the layered object according to this embodiment is 95.0%, and the improvement of the filling rate according to this embodiment is confirmed. It was.

  As described above, in this embodiment, the material powder layer is formed by flattening the material powder to a predetermined thickness determined according to the type of the material powder. Then, the cross-sectional element is formed using the laser light L1, and the cross-sectional element is integrated with the shaped body formed so far using the laser light L2, and then the surface of the cross-sectional element is smoothed by the laser light L4. Surface shaping is performed. Therefore, according to this embodiment, the filling rate of the final shaped body can be improved, and a high-strength solid can be shaped easily and quickly.

In the present embodiment, when the surface of the cross-sectional element is shaped by the laser light L4, the peak power of the laser light L4 is changed according to the scanning position, so that the surface of the cross-sectional element can be processed into a desired shape. it can.

  In the present embodiment, each time the cross-sectional elements of each layer are formed, the cross-sectional elements are cut using the laser light L3 so that the shape of the cross-sectional elements matches the design cross-sectional element shape with high accuracy. Therefore, the target three-dimensional shape can be accurately modeled.

  In the above-described embodiment, continuous light is used as the laser light L1, but pulsed light may be used as long as the pulse height and the pulse interval are appropriate.

  In addition to the Ni-Mo alloy steel powder, other alloy powders, and metal powders such as pure iron, as a powder material powder, even if ceramic powder or the like is used as a material, additive manufacturing is similarly performed. Can also be done. In addition, when the content of carbon is high in the composition of the alloy powder, it is preferable to perform laser light irradiation in an atmosphere that does not substantially contain oxygen, such as a nitrogen atmosphere or an argon atmosphere.

  In the above-described embodiment, the stage 41 is movable in the XY axis direction. However, if the scanning range of the laser beam by the laser irradiation devices 30A and 30B is sufficiently wide, the stage 41 may be fixed in the XY axis direction. Good. In the above embodiment, the stage 41 is moved in the Z-axis direction under the control of the computer system. However, the stage 41 may be manually moved in the Z-axis direction.

  Further, in the above embodiment, the adjustment of the positional relationship in the Z-axis direction between the material powder layer and the focal plane, which is required when a new material powder is supplied, is performed by moving the stage 41 in the Z-axis direction. It was. On the other hand, the Z position of the focal plane of the laser beams L1, L2, L3, and L4 is adjusted by moving the laser irradiation devices 30A and 30B and adjusting the irradiation optical systems 32A and 32B. May be.

  In the above embodiment, the scanning with the laser beams L1, L2, L3, and L4 may be performed using a movable mirror or the like, or the optical fiber light that guides the laser beams L1, L2, L3, and L4. The injection position may be moved.

  In the above embodiment, a YAG laser is used as the laser, but a carbon dioxide laser, a semiconductor laser, or the like can also be used.

  In the above embodiment, each of the laser irradiation devices 30A and 30B is independently provided with an irradiation optical system. On the other hand, one irradiation optical system can be obtained by guiding one of the lights emitted from the laser oscillators 31A and 31B to a common irradiation optical system by an optical switch that selectively outputs one of the lights. it can. Such a light switch can be constructed by making one or more mirrors movable.

  In addition, the three-dimensional shape that is the object of the layered modeling is not limited to the shape of the three-dimensional OBJ in the above-described embodiment, and can be an arbitrary three-dimensional shape.

  As described above, the additive manufacturing method of the present invention can be applied to additive manufacturing for forming an intended three-dimensional shape using powder as a material.

It is a figure showing roughly the composition of the additive manufacturing system for using the additive manufacturing method concerning one embodiment of the present invention. In one Embodiment of this invention, it is a figure for demonstrating the solid shape made into the modeling objective. It is a figure (the 1) for demonstrating the process in the additive manufacturing method which concerns on one Embodiment of this invention. It is a figure for demonstrating the cross-sectional element formed in FIG. 3, a shaping cross-section element, and a molded object. It is FIG. (2) for demonstrating the process in the additive manufacturing method which concerns on one Embodiment of this invention. It is a figure for demonstrating the cross-sectional element formed in FIG. 5, a shaping cross-sectional element, and a molded object. FIG. 7A is a cross-sectional photograph of a layered structure produced by applying the present invention, and FIG. 7B is a cross-sectional photograph of a layered structure of a comparative example. It is a figure for demonstrating the additive manufacturing method of a prior art example.

Explanation of symbols

10 ... laminate shaping system, 20 ... computer system, 30A, 30B ... laser irradiation apparatus, 40 ... stage device, 51 _1, 51 ₂ ... material powder, 52 _1, 52 ₂ ... material powder layer, 55 _1, 55 ₂ ... cross Element, 57 ₁ , 57 ₂ ... shaped cross-section element, 58 ₁ , 58 ₂ ... shaped body, L1 ... laser beam (first laser beam), L2 ... laser beam (second laser beam), L3 ... laser beam (fourth) Laser light), L4 ... laser light (third laser light), OBJ ... solid for modeling purposes.

Claims (4)

It is a layered modeling method for modeling a target three-dimensional shape using pure iron or a powder of an alloy containing iron as a main component ,
A material layer forming step of forming a material powder layer obtained by flattening the material powder to a predetermined thickness determined according to the type of material powder;
The region of the material powder layer corresponding to the design cross-sectional shape of the lamination position of the material powder layer in the target three-dimensional shape is scanned by the first laser beam, locally heated and melted, and then solidified and cross-sectioned. A cross-sectional element forming step for forming the element;
An integration step in which the cross-sectional element is scanned with a second laser beam, which is a pulsed laser beam, and a portion that has already been shaped by locally heating is integrated with the cross-sectional element;
The cross-sectional element integrated by the integration step is scanned with a third laser light that is pulsed laser light and has a peak power higher than that of the second laser light, and the surface of the integrated cross-sectional element is shaped. A surface shaping step to repeat; and a layered shaping method for shaping the intended three-dimensional shape ,
The first laser light is light after a continuous wave laser light having a beam diameter d ₁ [mm] passes through a condensing optical system having a focal length f ₁ [mm],
The thickness t [mm] of the powder material layer is determined when the distance between the focal position of the first laser beam and the surface of the powder material layer is z ₁ [mm]
t = k · ω ₁ = k · z ₁ · d ₁ / (2f ₁ )
Here, 3.2 ≦ k ≦ 4.0
Meet the requirements of
The power PM [W] and scanning speed v [mm / s] of the first laser light are as follows:
PM = A ・ v + B
Here, 10 <A <11, 25 <B <40
Meet the requirements of
The second laser beam passes through a condensing optical system in which a pulse laser beam having a beam diameter d ₂ [mm], a peak power PW [W], and a pulse width of 8 to 12 [ms] is focal length f ₂ [mm]. And the peak power PW [W] is a constant a of 600 when the distance between the focal position of the second laser beam and the surface of the cross-sectional element is z ₂ [mm]. Assuming that constant b is 470,
PW = a · ω ₂ + b = a · z ₂ · d ₂ / (2f ₂ ) + b
Together satisfy the, one pulse at a distance of (omega _2/2), the second laser beam is sequentially irradiated to the cross sectional element,
An additive manufacturing method characterized by that. 2. The additive manufacturing method according to claim 1, wherein, in the surface shaping step, a peak power of the third laser light is changed according to a scanning position. When the linear region adjacent to the specific linear region is scanned with the first laser light after scanning the specific linear region with the first laser light, 40 to 60% of the specific linear region is the It is contained in the adjacent linear area | region, The layered manufacturing method of Claim 1 or 2 characterized by the above-mentioned. Between the integration step and the surface shaping step, a fourth laser beam which is a pulse laser beam and whose peak power is higher than that of the third laser beam is irradiated, and the cross-sectional element is changed to the designed cross-sectional shape. Further comprising a cutting step of cutting so that
In the fourth laser beam, a pulse laser beam having an average power PC [W], a pulse width of several hundreds [ns], and a pulse frequency of 1 to 3 [kHz] is collected on the surface of the cross-sectional element via a condensing optical system. Light
When the scanning speed vc [mm / s], the average power PC is set such that the constant c is 5 ≦ c ≦ 15 and the constant d is 15 ≦ d ≦ 25.
PC = c · vc + d
Satisfying the conditions of
The additive manufacturing method according to any one of claims 1 to 3 , wherein the additive manufacturing method is performed.