KR20210147194A - Control method of slicing thickness with constant deposition and melting volume - Google Patents

Abstract

The present invention relates to a volumetric height control method of equivalent stacking, and more specifically, to a volumetric height control method of equivalent stacking, wherein powder stacked on a substrate having an inclined surface or a melting layer formed in a line process can be melted uniformly during a directed energy deposition process. According to the volumetric height control method of equivalent stacking according to the present invention, the moving velocity of a high-energy beam radiated to a powder layer stacked on an inclined surface of a substrate or a unit metal layer laminate is reduced or power thereof is increased or the thickness of the powder layer is adjusted during the melting of the powder layer stacked on the substrate or the unit metal layer laminate formed in a line process, thereby forming a unit metal layer having a uniform thermal effect part and comparatively constant beads from the inclined surface of the substrate or the unit metal layer laminate to a horizontal surface and moreover generating a stable three-dimensional product.

Description

Equivalent lamination volume height control method {Control method of slicing thickness with constant deposition and melting volume}

The present invention relates to a method for controlling the volume height of equivalent lamination, and more particularly, uniformly melting powder laminated on a substrate having an inclined surface during a directed energy deposition process or a metal layer formed in a line process. It relates to a method for controlling the equivalent stacking volume height that can be performed.

The additive manufacturing process is widely used in various fields such as the mold industry, the building industry, and the aviation industry. The additive manufacturing process is typically a material extrusion process, a material jetting process, a binder jetting process, a sheet lamination process, a container photopolymerization process, and a powder bed melting process. (Power Bed Fusion) process and energy-controlled deposition (Directed Energy Deposition) process, etc. are mentioned.

Among the additive manufacturing processes, the Directed Energy Deposition process is a laser metal forming technology that can rapidly produce metal products directly from 3D CAD (Computer-Aided Design) data or 3D program models. box.)

In the DED method, a high-power laser beam of 1 kW or more is locally irradiated to form a melt pool on the surface of a substrate (or laminated plate, original plate), and when irradiated with a high-power laser beam, the metal powder sprayed at the same time is also melted and laminated. In this way, by slicing a 3D CAD model or a 3D program model to a certain thickness and stacking the calculated 2D cross sections layer by layer, a 3D shape in which the 2D sections are stacked is made.

When irradiating a high-power laser beam, the metal powder supplied in real time through a coaxial powder feeder undergoes melting and rapid solidification to form a unit metal layer corresponding to a two-dimensional section with a dense structure. At this time, an inert gas such as helium (He) or argon (Ar) is supplied to transport the metal powder and prevent oxidation. At this time, the laser beam freely moves according to a path calculated from the 3D CAD model or the 3D program model.

Therefore, in order to manufacture the same three-dimensional shape as the 3D CAD model, it is important to precisely make the height of the metal single layer corresponding to the two-dimensional cross section in 3D printing.

On the other hand, when the metal single layer formed in the substrate (or laminate, original plate) or the line process consists only of a horizontal plane parallel to the ground, the heat-affected zone (HAZ) and the single layer in which properties change when the metal single layer is formed It is easy to form a uniform thickness.

However, when an inclined surface is formed on a substrate (or laminate, or a single layer of metal formed in the line process), the contact area of the powders supplied on the inclined surface is wider than the contact area of the powders supplied on the horizontal plane parallel to the ground. Since the heat loss is large and the amount of powder to be melted increases, there is a problem in that it is difficult to form a molten layer of uniform thickness, that is, a uniform unit metal layer, when irradiated with a high energy beam under the same conditions on a horizontal surface and an inclined surface.

Accordingly, there is a need for a method capable of forming a uniform molten layer from a horizontal surface to an inclined surface when the supplied powder is melted.

Republic of Korea Patent Publication No. 10-2018-0040744 : 3D printing laser beam irradiation device and 3D printing laser beam irradiation system including the same

The present invention was created to solve the above problems. Considering that the contact area of the powder layer is larger on the inclined surface than on the horizontal surface, so that heat loss and the amount of powder are increased, irradiation of a high energy beam between the horizontal surface and the inclined surfaces An object of the present invention is to provide an equivalent lamination volume height control method capable of forming a molten unit metal layer with a relatively uniform thickness by controlling the melting amount of metal powders by adjusting the conditions or powder supply amount.

In order to achieve the above object, the method for controlling the volume height of equivalent lamination of the present invention forms a molten pool on a substrate or a unit metal layer laminate and melts the powder layers formed by a plurality of metal powders supplied to the molten pool together. a beam irradiation step of irradiating the high energy beam while moving the high energy beam in a horizontal direction parallel to the ground from the inclined surface of the substrate or the unit metal layer stack; In the high-energy beam of the same diameter, the powder layer stacked on the inclined surface, in which the heat loss rate increases because the contact area of the powder layer is large compared to the horizontal plane, so that the powder layer stacked on the horizontal plane can be uniformly melted with the powder layer stacked on the horizontal plane , a lamination control step of adjusting the feed rate, power, or powder supply amount of the high energy beam to generate beads formed by melting the powder layer.

The stacking adjustment step is a beam power reduction step of reducing the power of the high energy beam so that, when the high energy beam is irradiated to the powder layer stacked on the horizontal plane, the residual stress in the powder layer can be reduced than on the inclined plane. It is preferable to include;

In the stacking control step, when the high-energy beam is irradiated to the powder layer stacked on the horizontal plane, the amount of melting of the powder layer stacked on the inclined plane is increased by increasing the transport speed of the high-energy beam than on the inclined plane. It is preferable to include a beam acceleration step to induce

In the stacking control step, when the high energy beam is irradiated to the powder layer stacked on the inclined surface, the amount of supply of the metal powder is reduced compared to the horizontal plane so that heat transfer of the high energy beam to the inclined surface is facilitated. It is preferable to include a powder supply reduction step of lowering the thickness of the powder layer.

In the step of reducing the beam power, it is preferable to reduce the power output of the high energy beam when the edge of the rear side opposite to the moving direction of the high energy beam passes on the boundary line between the horizontal plane and the inclined plane.

In the beam acceleration step, it is preferable to increase the moving speed of the high energy beam when the edge of the rear side, which is opposite to the moving direction of the high energy beam, passes on the boundary line between the horizontal plane and the inclined plane.

The equivalent lamination volume height control method of the present invention is a high-energy beam irradiated to the powder layer laminated on the inclined surface of the substrate or unit metal layer laminate when the powder layer laminated on the substrate or the unit metal layer laminate formed in the line process is melted. By lowering or increasing the power, or adjusting the thickness of the powder layer, it is possible to form a unit metal layer having a uniform heat-affected zone and a relatively constant bead from the inclined surface of the substrate or unit metal layer stack to the horizontal surface, and furthermore, stable 3 Allows dimensional products to be created.

1 is a partial cross-sectional view showing a state in which a high-energy beam device of a system for an energy-controlled lamination process irradiates a high-energy beam to a horizontal plane of a substrate or a unit metal layer stack,
2 is a view showing a heat-affected zone formed along an inclined surface inclined at 15 degrees of a substrate or a unit metal layer laminate;
3 is a view showing a heat-affected zone formed along an inclined surface inclined at 30 of a substrate or a unit metal layer laminate having the same hardness as in FIG. 2;
4 is an enlarged cross-sectional view of the heat-affected zone side of the bead formed by melting the powder layer laminated on the inclined surface inclined at 15 degrees of the substrate or the unit metal layer laminate;
5 and 6 are enlarged cross-sectional views of the heat-affected zone side of the bead formed by melting the powder layer laminated on the inclined surface inclined at 30 degrees of the substrate or the unit metal layer laminate.
7 is a partial side cross-sectional view of a substrate or a unit metal layer laminate having an inclined surface;
FIG. 8 is a view for comparing a region to which a high energy beam is irradiated to a horizontal surface and an inclined surface of the substrate or unit metal layer laminate of FIG. 7 .

Hereinafter, the equivalent stacked volume height control method according to the present invention will be described in more detail with reference to the accompanying drawings.

1 to 10 are diagrams for explaining a method for controlling an equivalent stacked volume height according to an embodiment of the present invention.

Prior to a detailed description of the method for controlling the equivalent stacking volume height according to an embodiment of the present invention, a configuration of a system for a general energy-controlled deposition (Directed Energy Deposition) process will be briefly described.

Although not specifically shown, the system for the energy-controlled deposition (Directed Energy Deposition) process includes a chamber (not shown) and a molten pool formed in the substrate 31 or the unit metal layer stack 32 formed in the pre-process in the chamber. and a high-energy beam mechanism for irradiating a high-energy beam for melting together the metal powder supplied to the molten pool.

The high energy beam mechanism includes a laser oscillation unit (not shown) that oscillates a high-power laser beam, a laser condenser unit (not shown) that performs a role of condensing the laser beam by combining optical components such as lenses or mirrors, and a laser condensing unit It may include a laser beam condensed from the laser beam having an increased energy level, and a laser irradiation unit irradiating to the substrate 31 located below, and a powder supply unit (not shown) for supplying metal powder around the laser irradiation unit.

The laser condenser serves to variably adjust or condense the width of the path of the laser beam L, and may include at least one collimation lens and a focusing lens.

The laser irradiation unit may include a nozzle 20 or the like for irradiating the laser beam L that has passed through the laser condensing unit. The laser irradiation unit may radiate a laser beam while moving along a tool path, and the distance between the laser irradiation unit and the substrate 31 or the unit metal layer stack 32 corresponds to the focal length of the laser beam L. can be adjusted. Here, the tool path may be calculated from 3D CAD data including modeling information of a metal to be manufactured.

The nozzle 20 has a beam penetrating part 21 formed so that the laser beam L focused on the center side is irradiated to the substrate 31 or the unit metal layer stack 32, and the powder supply part and connected to the beam penetrating part ( 21) to prevent metal oxidation and damage to the laser optical system in the process of laminating the powder supply line 22 and the metal single layer 40 open so that the metal powder 40a is supplied to the molten pool (not shown) side around 21). In order to do this, a molten pool is formed in an inert gas atmosphere and the metal powder 40a is melted to form a metal single layer 40 around the powder supply line 22 in the direction of the base material 31 or the unit metal layer stack 32 . A gas supply line 23 for discharging a protective gas such as argon or nitrogen is formed.

Here, the “powder layer 41” refers to a pile of a plurality of powders stacked on the upper surface of the substrate 31 or the unit metal layer stack 32 through the powder supply line 22, and the high energy beam L ) is melted as it is irradiated and formed into beads.

The unit metal layer 40 is a plurality of powder layers 41 are continuously formed on the upper surface of the substrate 31 or the unit metal layer stack 32 while being melted in the molten pool while being supplied along the moving direction of the high energy beam. It means a two-dimensional pattern and forms a unit of basic process. By stacking a plurality of these unit metal layers 40, the unit metal layer stack 32 is formed, and finally, a predetermined three-dimensional target product can be formed.

In a general energy-controlled lamination process, a metal powder 40a is supplied to the side to which the high-energy beam L is irradiated while irradiating a high-energy beam L on the upper portion of the substrate 31 or the unit metal layer stack 32 to supply the substrate. (31) or a unit metal layer forming step of forming a molten pool in the unit metal layer stack 32, and melting the metal powder in the molten pool along the movement path of the high energy beam (L); A multi-layer lamination step of forming a unit metal layer stack 32 by stacking a plurality of unit metal layers by repeating the process of supplying and melting the metal powder; may include.

On the other hand, the equivalent lamination volume height control method according to an embodiment of the present invention uses a high energy beam to melt the powder layer 41 laminated on the base material 31 or the unit metal layer laminate 32 during the energy control type lamination process. In the step of melting the powder layer 41 by supplying metal powder while irradiating the powder layer 41, a uniform single metal layer can be formed even on the inclined surface of the base material 31 or the unit metal layer stack 32. It relates to a method of controlling the irradiation condition of a high energy beam or adjusting the thickness of a powder layer. That is, the method for controlling the volume height of equivalent stacking according to an embodiment of the present invention may be included in the step of forming the unit metal layer.

On the other hand, referring to FIG. 7 , when _{comparing the same diameter (l 1} ), the area of the powder layer 41 of the part (b) in contact with the inclined surface 34 of the base material 31 or the unit metal layer laminate 32 ( S ₂ ) is greater than _{the area (S 1} ) of the portion (a) in which the powder layer 41 is in contact with the horizontal surface 33 . (S ₁ < S ₂ )

_{And, referring to FIG. 8 , when comparing the conditions of the same diameter ( l 2} ) of the high energy beam L, which is focused and narrows in width as it approaches the powder layer 41 , the portion (a) in contact with the horizontal plane 33 '), the area S' ₁ of the powder layer 41 is less than _{the area S' 2} of the powder layer 41 of the portion b' in contact with the inclined surface 34. _{(S' 1} < S ' ₂ )

Accordingly, the heat loss rate of the portion (b, b') in contact with the powder layer 41 on the inclined surface 34 is greater than the portion (a, a') in contact with the powder layer 41 in the horizontal plane, and the inclined surface 34 ), the amount of powder to be laminated on the horizontal plane 33 is increased. And, as the slope increases, the area of the powder layer 41 in contact with the slope increases, resulting in a larger heat loss rate.

Therefore, when irradiating a high energy beam to the powder layer 41 laminated on the substrate 31 or the unit metal layer stack 32 under the same conditions, the heat affected zone HAZ on the inclined surface 34 compared to the horizontal surface 33 is There is a problem in that the thickness of the unit metal layer 40 is not uniformly formed while not being uniformly formed.

2 and 3, due to the difference between the heat loss rate and the required metal powder between the horizontal plane and the inclined plane, when the substrate 31 or the unit metal layer laminate 32 is melted under a constant high energy beam irradiation condition, the horizontal plane and the inclined plane Boundary overmelting may occur. In addition, when the inclined surface and the horizontal surface of the substrate 31 or the unit metal layer laminate 32 are melted under a constant high energy beam irradiation condition, the heat affected zone (HAZ) formed in the substrate 31 or the unit metal layer laminate 32 is applied to the Cracks may occur (see FIG. 4 ), the thickness of the heat affected zone HAZ on the inclined surface may be formed narrow (see FIG. 5 ), or the thickness of the heat affected zone HAZ may not be formed uniformly ( FIG. 6 ). Reference).

The equivalent lamination volume height control method according to an embodiment of the present invention solves the above-mentioned problems to form a uniform unit metal layer 40 on the horizontal and inclined surfaces of a substrate or a unit metal layer stack, a beam irradiation step And, it may include a stacking adjustment step.

In the beam irradiation step, a high energy beam L is irradiated to form a molten pool in which the substrate 31 or the unit metal layer stack 32 is molten and to melt the powder layer 41 supplied to the molten pool together. This is a step of irradiating while moving the high energy beam L in the direction of the horizontal plane 33 parallel to the ground from the inclined surface 34 of the substrate 31 or the unit metal layer stack 32 .

In the beam irradiation step, a high energy beam (L) to form a molten pool (not shown) in which the substrate 31 or the unit metal layer stack 32 is molten and to melt the powder layer 41 supplied to the molten pool together. It is a step of irradiating while moving the high energy beam from the inclined surface 34 of the substrate 31 or the unit metal layer stack 32 to the horizontal plane 33 parallel to the ground.

In the stacking control step, in the high energy beam L of the same diameter, the powder layer 41 stacked on the inclined surface 34, which increases the heat loss rate due to the large contact area of the powder layer 41 compared to the horizontal plane 33, is a horizontal plane. Adjusting the feed rate, power reduction or powder supply amount of the high energy beam L to generate beads formed by melting the powder layer 41 so that it can be uniformly melted together with the powder layer 41 stacked on (33) is a step to

The stacking adjustment step may include any one or more of a beam power reduction step, a beam acceleration step, and a powder supply reduction step.

The beam power reduction step is the rear side opposite to the moving direction of the high energy beam (L) from one side on which the inclined surface 34 of the base material 31 or the unit metal layer stack 32 is formed to the other side on which the horizontal surface 33 is formed. It is a step of reducing the power of the high-energy beam (L) when the edge of the crosses the boundary line (3) of the horizontal plane (33) and the inclined plane (34).

In the beam power reduction step, when the high energy beam L is irradiated on the horizontal surface 33 where the powder layer 41 is easy to melt because the heat loss rate is lower than that on the inclined surface 34 , the horizontal surface is easier to melt than the inclined surface 34 . It is a step of reducing the power output of the high energy beam (L) so that the residual stress in the powder layer (41) supplied to (41) can be reduced.

For example, while outputting a high energy beam having an acceleration voltage of 15 KeV and an emission current of 15 mA to the inclined surface 34 in the beam power reduction step, a high energy beam having an acceleration voltage of 10 KeV and an emission current of 10 mA is irradiated from the horizontal surface 33. It is possible to adjust the beam irradiation condition of the instrument.

On the other hand, in the powder supply reduction step, when the high energy beam L is irradiated to the powder layer 41 stacked on the inclined surface 34 , heat transfer of the high energy beam L to the inclined surface 34 is facilitated, the metal powder 40a ) by controlling the supply amount to reduce the thickness of the powder layer 41 laminated on the inclined surface 34 rather than on the horizontal surface 33 to adjust the thickness of the bead formed by melting.

In the powder supply reduction step, when the high energy beam L is irradiated with the inclined surface 34, the amount of the metal powder 40a supplied to the inclined surface 34 through the powder supply unit is reduced by the amount of the metal powder 40a supplied to the horizontal surface 33. supply less. That is, when the edge of the rear side opposite to the moving direction of the high energy beam L passes the boundary line 3 between the horizontal surface 33 and the inclined surface 34, the supply amount of the metal powder 40a is increased. make it

On the other hand, in the beam acceleration step, when the high energy beam (L) is irradiated with the powder layer 41 stacked on the horizontal surface 33 having a smaller heat loss rate than the inclined surface 34, the energy transfer time of the high energy beam L is reduced by the inclined surface ( 33), the moving speed of the high-energy beam L is increased to induce the melting amount of the powder layer 41 stacked on the horizontal surface 34 and the reduction of the heat-affected zone. Conversely, in the beam acceleration step, the moving speed of the high-energy beam on the inclined surface 34 is lower than that on the horizontal surface 33 to induce the expansion of the melt amount of the powder layer 41 stacked on the inclined surface 34 .

In the beam acceleration step, the high energy beam L is moved from one side of the substrate 31 or the unit metal layer stack 32 to the other side so that the high energy beam L of the same condition can be irradiated on the inclined surface 34 . When the edge of the rear side opposite to the direction passes the boundary between the horizontal plane 33 and the inclined plane 34 , it is preferable to increase the moving speed of the high energy beam L.

The beam power reduction step, the beam acceleration step, and the powder supply reduction step may be performed in parallel. The beam acceleration step may be performed simultaneously with the beam power reduction step, and the powder supply reduction step is performed before the beam acceleration step and the beam power reduction step.

The equivalent laminate volume height control method according to an embodiment of the present invention is performed when the powder layer laminated on the substrate 31 or the unit metal layer laminate 32 formed in the pre-process is melted, the substrate 31 or the unit metal layer laminate 32 ) by lowering the moving speed or increasing the power of the high-energy beam irradiated to the powder layer 41 laminated on the inclined surface 34, or by adjusting the thickness of the powder layer 41 laminated on the inclined surface 34, (31) or a molten layer having a uniform heat-affected zone and relatively constant beads from the horizontal surface 33 to the inclined surface 34 of the unit metal layer stack 32, that is, a unit metal layer can be formed, and furthermore, a stable three-dimensional Let the product be created.

Although the present invention has been described with reference to the embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent embodiments are possible therefrom. The true protection scope of the invention should be defined only by the appended claims.

31: description
32: unit metal layer laminate
33: horizontal plane
34: slope
40: single metal layer
41: powder layer
L: high energy beam

Claims (6)

The high energy beam is irradiated to form a molten molten pool on the substrate or the unit metal layer laminate and melt the powder layer formed by the metal powders supplied to the molten pool together, but the inclined surface of the substrate or the unit metal layer laminate a beam irradiation step of irradiating while moving the high energy beam in a horizontal plane direction parallel to the ground;
In the high-energy beam of the same diameter, the powder layer stacked on the inclined surface, in which the heat loss rate increases because the contact area of the powder layer is large compared to the horizontal plane, so that the powder layer stacked on the horizontal plane can be uniformly melted with the powder layer stacked on the horizontal plane , a stacking control step of adjusting the feed rate, power, or powder supply amount of the high-energy beam to melt the powder layer to generate beads. The method of claim 1, wherein the stacking control step comprises:
When the high-energy beam is irradiated to the powder layer stacked on the horizontal plane, a beam power reduction step of reducing the power of the high-energy beam so that the residual stress in the powder layer can be reduced than on the inclined plane. Equivalent stacking volume height control method, characterized in that. The method of claim 1 , wherein the stacking adjustment step comprises:
When the high-energy beam is irradiated to the powder layer stacked on the horizontal plane, the beam acceleration is increased to increase the transport speed of the high-energy beam than on the inclined plane to induce expansion of the amount of melt of the powder layer stacked on the inclined plane than on the horizontal plane Equivalent stacking volume height control method comprising the step. The method of claim 1, wherein the stacking adjustment step comprises:
When the high energy beam is irradiated to the powder layer stacked on the inclined surface, the supply amount of the metal powder is reduced compared to the horizontal plane so that heat transfer of the high energy beam to the inclined surface is facilitated. The thickness of the powder layer laminated on the inclined surface Equivalent stacking volume height control method comprising the step of reducing the powder supply to lower the. The method of claim 2, wherein the step of reducing the beam power
Equivalent stacking volume height control method, characterized in that the power output of the high energy beam is reduced when the edge of the rear side opposite to the moving direction of the high energy beam passes on the boundary line between the horizontal plane and the inclined plane . The method of claim 3, wherein the beam acceleration step
The equivalent stacking volume height control method according to claim 1, wherein the moving speed of the high energy beam is increased when the edge of the rear side opposite to the moving direction of the high energy beam passes on the boundary line between the horizontal plane and the inclined plane.

Images