KR20210077444A - Printing method and apparatus using a 3d prining technology - Google Patents

Abstract

The present disclosure provides a three-dimensional manufacturing method and a printing apparatus of a metal material using 3D printing. According to the present disclosure, the three-dimensional manufacturing method and the printing apparatus of a metal material using 3D printing form a metal layer by 3D printing technology and apply external force to a surface of the metal layer in a direction in which the metal layer is stacked, thereby improving a structure of the stacked metal layer.

Description

Printing method and printing apparatus using 3D printing technology {PRINTING METHOD AND APPARATUS USING A 3D PRINING TECHNOLOGY}

The present invention relates to a printing method and a printing apparatus using 3D printing technology, and more particularly, to a printing method and a printing apparatus for manufacturing a shape of a metal material by 3D printing technology using a metal powder.

3D printing is based on digital design data realized in three dimensions by spraying, melting, and solidifying a material in the form of powder, liquid, or thread through a nozzle, so that a three-dimensional object is made very thin layer by layer. It is a technology that manufactures 3D objects by stacking them from the bottom to the vertex.

3D printing is a concept in contrast to Subtractive Manufacturing, which is manufactured by cutting materials. The official term is called Additive Manufacturing (AM) or Rapid Prototyping (RP), and 3D printers can implement the 3D printing process. It is a machine that can

Recently, there are studies to improve efficiency by using 3D printing technology in the manufacture of metal parts, etc., and in particular, attempts to apply 3D printing technology to precision parts requiring various processing are increasing.

The representative metal additive manufacturing process of 3D printing is largely divided into two types: Powder Bed Fusion (PBF) and Direct Energy Dsposition (DED).

First, the PBF method is a method in which a powder layer of several tens of micrometers is laid on a powder bed having a certain area in a powder supply device, a laser or electron beam is selectively irradiated according to the design drawing, and then melted layer by layer and stacked up. Terms such as SLM (Selected Laser Melting), Leser Cursing, and DMLS (Direct Metal Laser Sintering) are used interchangeably.

Next, the DED method supplies metal powder in a protective gas atmosphere in real time, melts it immediately after supply with high energy such as a high-power laser, and laminates it, and repeats the supply, melting and lamination steps until the desired metal material is completed. characterized in that

This DED method has the advantages of improved reproducibility, high productivity, advantageous application of large parts, and the ability to repair and regenerate existing metal parts, so research and development is in progress as a large-scale or complex system at home and abroad.

At this time, the DED process does not add an additional process other than the laser heat source, and after the powder is melted, it solidifies in the opposite direction (ie, the (+) direction of the z-axis) to the direction in which the heat source exits (ie, the (-) direction of the z-axis). The city tissue grows to complete the desired metal material

However, in the case of manufacturing a three-dimensional metal material using the DED method, solidification (or cooling) proceeds rapidly in the (+) direction of the z-axis during melting and lamination, so that the microstructure grows long in the vertical direction and becomes anisotropic ( anisotropic), which causes a difference in mechanical properties between the xy plane and the z-axis direction due to anisotropy, causing a problem in that the mechanical properties are deteriorated.

In order to improve the above problem, in the prior art, there is a technique of adding a recrystallization step by performing post-heat treatment on a metal material in the existing metal 3D printing technology, but a lot of costs occur, resulting in an increase in manufacturing cost, and eventually lowering productivity There are problems such as

The present invention provides a method and apparatus for solving the problem that the mechanical properties of the xy plane and the z-axis direction are different due to the anisotropy of the lamination surface generated as solidification proceeds in the z-axis direction in 3D printing using metal powder and a laser. to provide.

One embodiment of the present invention provides a printing method for manufacturing a shape of a metal material by 3D printing technology, the printing method comprising the following steps:

A layer forming step of supplying a metal powder and irradiating a modeling light source used for 3D printing to form a metal layer by melting and solidifying the metal powder;

applying an external force to the surface of the metal layer in a stacking direction of the metal layer; and

A repeated execution step of stacking a plurality of metal layers by repeatedly executing the layer forming step and the external force application step.

In the repeated execution step, the number of repetitions of the layer forming step and the external force application step may include performing the external force application step every time one metal layer is stacked, or an external force once every time a plurality of metal layers are stacked. An authorization step may also be performed.

The external force application may be implemented in a manner that specifically causes particles to collide with the surface of the metal layer by blasting, or may be implemented by striking the surface of the metal layer with a small hammer, but is not limited thereto.

Illustratively, the hitting area by the hammer may be 1 to 2 mm in diameter.

Also illustratively, in the step of applying the external force, the external force may be applied so that the thickness of the metal layer in the stacking direction is reduced by 5 to 10%.

Another embodiment of the present invention provides a printing apparatus for manufacturing a shape of a metal material by 3D printing technology. This printing device may comprise the following components:

a printing head configured to form a metal layer by melting and solidifying the metal powder using the metal powder and the modeling light source;

an external force applying unit for applying an external force to the surface of the metal layer in a stacking direction of the metal layer; and

A control unit configured to control the printing head unit and the external force application unit to repeatedly perform formation of a metal layer and application of an external force.

Optionally, the control unit controls the printing head unit and the external force applying unit to apply an external force to the surface of the metal layer whenever one metal layer is formed, or when forming a plurality of metal layers It is possible to apply an external force to the surface of the metal layer once every time.

Illustratively, the external force applying unit may be a blasting device that collides particles with the surface of the metal layer by blasting, or a hammer device that strikes the surface of the metal layer by a hammer.

According to the present invention, by applying an external force to the surface of the metal layer in the lamination direction after forming the metal layer, the anisotropy occurring during solidification of the metal layer can be alleviated, and a separate post-treatment such as recrystallization is not required to solve this. won't

In addition, not only can the anisotropy be alleviated, but also effects such as density improvement and removal of pores or cracks can be obtained by applying an external force to the surface of the layer, and as a result, the mechanical properties of the resultant manufactured by 3D printing are improved can increase productivity.

1 is a schematic flowchart of a printing method for manufacturing a shape of a metal material by 3D printing technology according to an embodiment of the present invention.
2 is a schematic diagram for explaining the repeated execution of the layer forming step and the external force application step in the printing method according to an embodiment of the present invention.
3 is a schematic configuration diagram of a printing apparatus for manufacturing a shape of a metal material by 3D printing technology according to an embodiment of the present invention.
4 and 5 are photographs for comparing the structure of the laminated portion of the metal layer obtained according to an embodiment of the present invention with that of the prior art.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in the present specification and claims should not be construed as being limited to conventional or dictionary meanings, and the inventor should properly understand the concept of the term in order to best describe his invention. Based on the principle that can be defined, it should be interpreted as meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention, and do not represent all the technical spirit of the present invention, so at the time of the present application, they are equivalent It should be understood that there may be variations.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic flowchart of a printing method for manufacturing a shape of a metal material by 3D printing technology according to an embodiment of the present invention.

The printing method according to the present embodiment may be implemented using, for example, a printing apparatus illustrated in FIG. 3 to be described later, but is not limited thereto.

As shown in Fig. 1, the printing method according to this embodiment includes the following steps.

S100: The metal powder is supplied, and the metal powder is melted by irradiating a modeling light source used for 3D printing, and then the molten metal powder is cooled and solidified to form a metal layer of metal.

For example, it is possible to supply a metal powder such as STS316L, and irradiate a modeling light source used for 3D printing, such as an electron beam, arc, or plasma.

Since 3D printing technology using metal powder is known in the prior art, a detailed description of the process of forming a metal layer according to an input design after supplying the metal powder and melting it to a laser light source will be omitted. It is well understood by those skilled in the art that the type of metal powder, the type of laser, and the specific operation method for forming a layer are known in the prior art, and that they may vary depending on the type or structure of the object to be manufactured.

S200: An external force is applied to the surface of the metal layer in the stacking direction of the metal layer.

Applying an external force is to impact or hit the upper surface of the most recently laminated metal layer, and various methods may be used for this purpose.

As the external force application method, although exemplary, there may be a method in which particles collide with the surface of the metal layer by blasting and a method in which the surface of the metal layer is struck by a hammer. Either way, it is to apply an external force to the surface of the metal layer in its lamination direction. Here, blasting is not meant as a process of polishing the surface by spraying abrasive particles, but means a process of applying an external force to a subject by spraying particles to collide with the surface, which is the same hereafter.

The thickness of the metal layer is reduced in the stacking direction by the external force, but an external force can be applied to decrease by about 5 to 10%, but is not limited thereto, and it can be adjusted according to the type of metal material or other conditions. can However, if the external force is too small, the desired effect cannot be obtained. On the contrary, if the external force is too large, the metal layer may be damaged. The strength of an appropriate external force can be easily determined through limited repeated experiments.

When hitting the surface with a hammer, the diameter of the striking area may be approximately 1 to 2 mm.

S300: The metal layers are laminated by alternately repeating the steps S100 and S200.

When repeating the layer forming step (S100) and the external force application step (S200), the ratio of the number of trials can be adjusted, and most basically, the step of applying an external force to the surface whenever a single metal layer is formed. can be done

However, if the step of applying an external force to the surface is performed whenever a single metal layer is formed, a relatively high level of results may be obtained, but productivity may decrease due to an increase in manufacturing time.

Therefore, it can be seen that the step of applying an external force is performed once every time a plurality of metal layers are formed. In this case, an external force is applied to the surface of the uppermost metal layer, and the applied external force affects not only the uppermost metallic layer but also the lower metallic layer. Even if an external force is applied once every time, the anisotropy of the metal layer stacked under the uppermost metal layer is not completely eliminated.

Illustratively, one external force application may be performed every time 3-5 metal layers are formed.

In this case, since the increase in manufacturing time is not relatively large, the effect of improving the structure of the metal layer can be obtained while maintaining productivity.

2 is a schematic diagram for explaining the printing method according to the present embodiment for easier understanding.

As shown on the leftmost side in FIG. 2 , a metal layer is laminated using a laser and metal powder. Thereafter, as shown in the middle of FIG. 2 , an external force is applied to the surface in the stacking direction. As the external force application method, as described above, a method in which particles collide with the surface by blasting or strike the surface by a hammer may be used. After the external force is applied to the entire surface of the metal layer of the uppermost layer, the metal layer is laminated using a metal powder and a laser, again as shown in the far right of FIG. 2 . Thereafter, the process of applying an external force again after laminating one or more metal layers is repeated.

3 is a schematic configuration diagram of a printing apparatus for manufacturing a shape of a metal material by 3D printing technology according to an embodiment of the present invention.

As shown in FIG. 3 , the printing apparatus according to the present embodiment largely includes a printing head unit 100 , an external force applying unit 200 , and a control unit 300 .

The printing head unit 100 is configured to form a metal layer by melting the metal powder and releasing the metal powder according to the design using a modeling light source (eg, a laser) to solidify it.

The printing head unit 100 may include, for example, a powder supply unit 130 , a shield gas supply unit 140 , and a light source unit 120 .

The printing head unit 100 receives the metal powder from the powder supply unit 130 and receives the shield gas from the shield gas supply unit 140 under the control of the control unit 300 , while irradiating the light source from the light source unit 120 . The metal powder is melted, discharged to a predetermined position, and solidified. At this time, as the bed 110 in FIG. 3 moves, or the printing head 100 moves, or both move, the metal layer is formed along a pre-designed path.

The external force applying unit 200 is configured to apply an external force to the surface of the metal layer in the stacking direction after the metal layer is formed by the printing head unit 100 under the control of the control unit 300 .

The external force applying unit 200 may be, for example, a blasting device that collides particles onto the surface of the metal layer by blasting, or a hammer device that hits the surface of the metal layer by a hammer, but is not limited thereto, and the surface of the metal layer is not limited thereto. Any other means capable of applying an external force in the stacking direction may be used.

The control unit 300 controls the printing head unit 100 and the external force application unit 200 to repeatedly perform the formation of the metal layer and the application of the external force. In this case, the execution ratio of the metal layer formation and the external force application may be set as 1:1, 3:1, or 4:1. That is, an external force may be applied every time one metal layer is formed, an external force may be applied once every three metal layers are formed, and once every four or five metal layers are formed. External force application may also be performed.

Of course, it is not necessary to repeat at the same execution rate until one finished product is manufactured, for example, the execution rate may be different at the initial stage of lamination and at the end of lamination. In addition, the strength of the external force to be applied can also be adjusted differently in the initial stage and in the latter stage of lamination.

The present inventors confirmed the effect according to the embodiment of the present invention through the following experiment.

STS316L powder was supplied as a metal powder, and the metal powder was melted by selectively irradiating an arc beam or the like as a modeling light source used for 3D printing (in this experiment, DED was used). The molten metal powder was rapidly cooled and solidified to form the first metal layer made of a metal material. Then, an external force was applied to the surface of one formed metal layer by blasting. Then, until the three-dimensional object of the metal material was completed, the above-described supply of metal powder, formation of a metal layer due to melting and solidification, and application of external force through blasting were repeated.

A metal layer stack structure formed by this embodiment is shown in FIG. 5 .

Meanwhile, in the above embodiment, the result obtained by stacking only the metal layer except for the process of applying an external force by blasting is shown in FIG. 4 .

A comparison of FIG. 4 showing the laminated structure obtained without applying an external force and FIG. 5 showing the laminated structure obtained including the process of applying an external force according to an embodiment of the present invention is as follows.

Referring to FIG. 4 , in the microstructure observed after the metal powder is melted and solidified, it was confirmed that the solidified tissue grew in a cellular dendritic form to form a long cluster.

On the other hand, referring to FIG. 5 , in the microstructure observed by melting and solidifying the metal powder by adding a blasting process, it was confirmed that the solidified structure was more observed in the equiaxed structure.

From this, it can be confirmed that when a metal material is used for 3D printing by adding an external force applied and fixed according to an embodiment of the present invention, the microstructure is improved. In addition, because of this, a separate post-processing becomes unnecessary, and since microcracks and the like can be removed by an external force application process, productivity can be improved.

The present invention is not limited to the above embodiments and/or embodiments, but may be manufactured in various different forms, and those skilled in the art to which the present invention pertains may change the technical spirit or essential features of the present invention It will be understood that the present invention may be implemented in other specific forms without not doing so. Therefore, it should be understood that the embodiments and/or embodiments described above are illustrative in all respects and not restrictive.

100: printing head unit 110: bed
120: laser head 130: powder supply unit
140: shield gas supply
200: external force applying unit
300: control unit

Claims (11)

As a printing method for manufacturing the shape of a metal material by 3D printing technology,
A layer forming step of supplying a metal powder and irradiating a modeling light source used for 3D printing to form a metal layer by melting and solidifying the metal powder;
applying an external force to the surface of the metal layer in a stacking direction of the metal layer; and
Repeated execution of stacking a plurality of metal layers by repeatedly executing the layer forming step and the external force application step
A printing method comprising a. According to claim 1,
In the repeated execution step, the layer forming step and the external force application step are repeated every time a metal layer of one layer is formed,
printing method. According to claim 1,
In the repeated execution step, the layer forming step and the external force application step are repeated in such a way that an external force is applied once every time a plurality of metal layers are formed.
printing method. 4. The method according to any one of claims 1 to 3,
The step of applying the external force is a step of applying an external force in such a way that particles collide with the surface of the metal layer by blasting,
printing method. 4. The method according to any one of claims 1 to 3,
The step of applying the external force is a step of applying an external force in a manner that strikes the surface of the metal layer with a hammer,
printing method. 6. The method of claim 5,
The striking area by the hammer is 1 to 2 mm in diameter, the printing method. 4. The method according to any one of claims 1 to 3,
In the step of applying the external force, the printing method of applying an external force so that the thickness in the stacking direction of the metal layer is reduced by 5 to 10%. As a printing device for manufacturing the shape of a metal material by 3D printing technology,
a printing head configured to form a metal layer by melting and solidifying the metal powder using the metal powder and the modeling light source;
an external force applying unit for applying an external force to the surface of the metal layer in a stacking direction of the metal layer; and
A control unit that controls the printing head unit and the external force application unit to repeatedly perform metal layer formation and external force application
A printing device comprising a. 9. The method of claim 8,
The control unit controls the printing head unit and the external force applying unit to apply an external force to the surface of the metal layer whenever one metal layer is formed. 9. The method of claim 8,
The control unit controls the printing head unit and the external force applying unit to apply an external force to the surface of the metal layer once every time a plurality of metal layers are formed. 11. The method according to any one of claims 8 to 10,
The external force applying unit is a blasting device that collides particles on the surface of the metal layer by blasting, or a hammer device that strikes the surface of the metal layer by a hammer, a printing device.

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