Method for manufacturing objects using a metal 3D printer

Abstract

This invention provides a method for manufacturing objects using a metal 3D printer that suppresses the generation of slag. [Solution] The manufacturing method of the present disclosure is a method for manufacturing a molded object using a metal 3D printer 1, and includes a molding step in which a molten tip is formed by the heat of an arc discharge ARC while supplying a shielding gas SG to the tip of a carbon steel wire WR, and the molten tip is laminated onto a target portion to form a molded object, wherein the arc discharge ARC is formed by applying a voltage between the carbon steel wire WR and the target portion and passing a current of 200A or less, and the shielding gas SG is 100% argon gas.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a shaped object using a metal 3D printer.

Background Art

[0002] Patent Document 1 discloses a metal 3D printer that performs shaping by melting a wire by arc discharge from the tip of the wire while supplying a shielding gas and laminating the melted welding material on the upper surface of a base plate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when melting a carbon steel wire by arc discharge, a shielding gas such as carbon dioxide gas, a mixed gas of argon and oxygen, or a mixed gas of argon and carbon dioxide gas is used.

[0005] That is, a gas containing an active gas such as carbon dioxide gas and oxygen gas is used as the shielding gas.

[0006] However, when the shielding gas contains an active gas, a large amount of slag is generated.

[0007] And if the next lamination is performed while leaving the slag, the slag will be involved, leading to a deterioration in the quality of the shaped object to be formed.

[0008] Therefore, it is necessary to clean the lamination surface and remove the slag on the lamination surface before laminating each layer, which is a problem that takes time and effort.

[0009] This disclosure is made in view of these circumstances and aims to provide a method for manufacturing molded objects using a metal 3D printer that suppresses slag generation. [Means for solving the problem]

[0010] The manufacturing method disclosed herein is a method for manufacturing an object using a metal 3D printer, The process includes a molding step in which a shielding gas is supplied to the tip of a carbon steel wire, a molten tip is formed by the heat of an arc discharge, and the molten tip is laminated onto the target portion to form the object, The aforementioned arc discharge is formed by applying a voltage between the carbon steel wire and the target portion, thereby passing a current of 200A or less. The shielding gas is 100% argon. [Effects of the Invention]

[0011] According to this disclosure, it is possible to provide a method for manufacturing a molded object using a metal 3D printer that suppresses the generation of slag. [Brief explanation of the drawing]

[0012] [Figure 1] This is a side view of a metal 3D printer according to an embodiment of the present disclosure. [Figure 2] Figure 1 is a side view of the metal 3D printer with the nozzle removed from the manipulator. [Figure 3] Figure 1 is a front view of the metal 3D printer with the nozzle removed from the manipulator. [Figure 4] This is a schematic diagram illustrating the configuration of the nozzle in the embodiment of the present disclosure. [Figure 5] This diagram schematically shows the state of a fabricated object created using 100% argon as the shielding gas. [Figure 6] This diagram schematically shows the state of a fabricated object created under appropriate conditions with 100% argon as the shielding gas. [Modes for carrying out the invention]

[0013] Hereinafter, with reference to the accompanying drawings, embodiments for implementation (hereinafter referred to as "embodiments") will be described in detail. Throughout the description of the embodiments, the same elements are denoted by the same numbers or symbols.

[0014] <<Embodiment>> Regarding the metal 3D printer 1 according to the embodiment of the present disclosure and the manufacturing method of the molded object M using the metal 3D printer 1, description will be made while referring to FIGS. 1 to 6.

[0015] FIG. 1 is a side view of the metal 3D printer 1 according to the embodiment of the present disclosure. FIG. 2 is a side view of the metal 3D printer 1 in FIG. 1 with the nozzle 6 removed from the manipulator 2. FIG. 3 is a front view of the metal 3D printer 1 in FIG. 1 with the nozzle 6 removed from the manipulator 2.

[0016] <Metal 3D Printer 1> As shown in FIGS. 1 to 3, the metal 3D printer 1 includes a manipulator 2, a base portion 3 for fixing the manipulator 2, a table 4 attached on the base portion 3, a base material 5 provided on the table 4, and a nozzle 6 (see FIG. 1) attached to the tip of the manipulator 2.

[0017] Note that the metal 3D printer 1 includes a wire supply mechanism for supplying a carbon steel wire WR (not shown) to the nozzle 6, a gas supply mechanism for a shielding gas supplied when melting the carbon steel wire WR (not shown) by arc discharge, and a power source E for arc discharge. Although not shown, the wire supply mechanism, the gas supply mechanism, and the power source E may be general ones used in a metal 3D printer.

[0018] [Manipulator 2] Mainly, the manipulator 2 will be described while referring to FIGS. 2 and 3. The manipulator 2 comprises a manipulator base 21 fixed to the base 3, a swing head 22, a forearm 23, an upper arm 24, a wrist 25, and a swivel head 26.

[0019] (Manipulator Base 21) The manipulator base 21 is a fixing part for securing the manipulator 2 to prevent it from tipping over, and is positioned on the base part 3 and fixed to the base part 3 with bolts B1.

[0020] (Swinghead 22) As shown in Figure 2, the swing head 22 is rotatably connected to the manipulator base 21 around a first axis VA (see Figure 2) parallel to the vertical.

[0021] (Lower arm 23) As shown in Figure 2, the forearm portion 23 is connected to the swing head 22 so as to be rotatable (see arrow AR1) with its base end being on a second axis RC1 that is perpendicular to the vertical and parallel to the horizontal direction.

[0022] (Upper arm 24) As shown in Figure 2, the upper arm portion 24 is rotatably connected to the lower arm portion 23 (see arrow AR2) with its proximal end being the pivot point RC2, which is the third axis parallel to the second axis.

[0023] (Wrist part 25) The wrist portion 25 is connected to the tip of the upper arm portion 24 so that its base end can pivot (see arrow AR3 in Figure 3).

[0024] (Swivel section 26) As shown in Figure 2, the swivel section 26 is provided at the tip of the wrist section 25 so as to be able to swivel (see arrow AR4) in one direction perpendicular to the longitudinal direction of the wrist section 25.

[0025] The oscillating unit 26 has a rotation mechanism (not shown) that rotates the attachment (in this example, the nozzle 6) attached to the oscillating unit 26 relative to the oscillating unit 26 (see arrow AR3 in Figure 3).

[0026] [Base section 3] As shown in Figures 1 to 3, the base section 3 is a pedestal constructed by combining H-beams to securely hold the manipulator 2 and table 4. However, it is not limited to H-beams; any structure that can securely hold the manipulator 2 and table 4 in an appropriate positional relationship is acceptable.

[0027] Furthermore, the underside of the base section 3 is equipped with casters (wheels) for use during transport and adjusters to prevent movement during use.

[0028] [Table 4] Table 4 is mounted on the base 3 so as to be positioned at an appropriate distance from the manipulator 2, in order to properly create shapes using molten metal from the nozzle 6 attached to the tip of the manipulator 2.

[0029] Specifically, the table 4 is positioned on the base 3 and fixed to the base 3 with bolts (not shown).

[0030] The suspension bolts visible in the diagram are provided for connecting shackles and other components that connect to the wires and other components of the lifting device used when moving table 4.

[0031] [Base material 5] The base material 5 is a substrate that serves as the target for layering the initially molten carbon steel when fabricating using the metal 3D printer 1. It is detachably fixed to the table 4 with bolts B2 so that it can be removed from the table 4 along with the fabricated object M (not shown) after fabrication.

[0032] In this embodiment, the base material 5 is placed on the table 4, but the table 4 itself may be used as the base material 5, and the object M may be fabricated by laminating on the table 4.

[0033] However, the substrate (base material 5 in this example), which serves as the target for laminating the initially molten carbon steel, may be reused after the laminate is removed by cleaning its surface (e.g., surface polishing), but it may also be discarded without being reused.

[0034] Therefore, the target substrate (base material 5 in this example) often serves as a disposable, supplementary component (also called a supplementary component) in the metal 3D printer 1.

[0035] Therefore, instead of using the table 4 as a target for laminating the initially molten carbon steel, it is preferable, as in this embodiment, to place a base material 5 on the table 4 as a component that can be used as a supplementary material, and then perform lamination on the base material 5.

[0036] Furthermore, although this embodiment shows the case where the base material 5 is in the shape of a plate, the base material 5 is not limited to being in the shape of a plate, and any shape can be selected as needed.

[0037] For example, when combining multiple molded objects M to produce a single structure, the base material 5 may have a shape suitable for assembling the molded objects M (for example, a shape that has a bonding structure for joining the molded objects M in addition to the layered surface).

[0038] In this way, the base material 5 is not treated as disposable, but can be effectively utilized as one of the structural components in the fabrication of the structure.

[0039] [Nozzle 6] Figure 4 is a schematic diagram illustrating the configuration of the nozzle 6 in the embodiment of the present disclosure. Nozzle 6 is a nozzle that melts the fed carbon steel wire WR with the heat of an arc discharge ARC while injecting shielding gas SG to surround the fed carbon steel wire WR.

[0040] As shown in Figure 4, the nozzle 6 includes a guide tube 61 at its tip that guides the carbon steel wire WR, and an outer tube 62 that covers the guide tube 61 so as to form a gap between them.

[0041] Furthermore, the anode of power supply E is in contact with the carbon steel wire WR, and the cathode is connected to the base material 5, and a voltage is applied between the carbon steel wire WR and the base material 5, which is the part to be laminated.

[0042] Please note that Figure 4 merely illustrates the electrical connection relationship between the anode and cathode of power supply E.

[0043] Furthermore, since the carbon steel laminated on the base material 5 is physically connected to the base material 5, it will be at almost the same potential as the base material 5. Therefore, even when further lamination is performed on top of the laminated carbon steel, a voltage is applied between the carbon steel wire WR and the already laminated portion that is the target of the lamination.

[0044] Then, shielding gas SG is flowed into the space between the guide tube 61 and the outer tube 62, and while supplying shielding gas SG to the tip of the carbon steel wire WR, a voltage is applied between the carbon steel wire WR and the target area for lamination (base material 5 in Figure 4). The heat from the arc discharge ARC, which is a continuous discharge generated by the application of voltage, forms a tip molten portion at the tip of the carbon steel wire WR, and this tip molten portion is deposited as molten droplets onto the target area for lamination.

[0045] Here, it was hypothesized that slag generation was caused by the reaction of active gases (carbon dioxide, oxygen, etc.) with components in the carbon steel wire WR due to the presence of active gases in the shielding gas SG. Therefore, the shielding gas SG was not mixed with active gases, and the layering was carried out using 100% argon as the shielding gas SG.

[0046] Figure 5 schematically shows the state of the fabricated object M when the shielding gas SG is 100% argon, and schematically shows the state of the fabricated object M before adjusting the conditions.

[0047] Note that Figure 5 schematically shows only the part of the molded object M, and other parts such as the base material 5 are omitted from the illustration.

[0048] When the shielding gas SG was changed to 100% argon, the generation of slag was significantly suppressed, but a new problem arose: as shown in Figure 5, the thickness and width of the stacked layers were not uniform, resulting in a fabricated object M with many bumps and irregularities on its surface.

[0049] Upon observing the state during lamination, it was found that fluctuations occurred in the formed arc discharge (ARC), resulting in significant variations in the width and height of the beads formed during lamination, and consequently, irregular irregularities appearing.

[0050] Therefore, we proceeded with investigations to stabilize the arc discharge (ARC), and found that by applying a voltage between the carbon steel wire (WR) and the target part of the laminate and passing a current of 200A or less, the fluctuation of the arc discharge (ARC) can be suppressed.

[0051] In other words, in a manufacturing method for a fabricated object M using a metal 3D printer 1, which includes a fabrication process in which a molten tip is formed by the heat of an arc discharge ARC while supplying a shielding gas SG to the tip of a carbon steel wire WR, and the molten tip is then layered onto the target area to fabricate the fabricated object M, it was found that when the shielding gas SG is 100% argon, applying a voltage between the carbon steel wire WR and the target area to create an arc discharge with an arc current (also simply called current) of 200A or less is effective in suppressing variations in the width and thickness of the layered layers.

[0052] Furthermore, if the arc current becomes too low, it becomes difficult to properly form the molten tip, so it is desirable that the arc current be 100A or higher.

[0053] Furthermore, in order to ensure stable lamination, it is desirable to move the nozzle 6, which supplies carbon steel wire WR and shielding gas SG to the lamination target area, at a speed within a predetermined range of movement speeds.

[0054] To explain in more detail, the movement speed of the nozzle 6 corresponds to the length of the layer that is stacked per unit time. To make the explanation easier to understand, let's consider the case where carbon steel wire WR is supplied to the nozzle 6 at a constant supply rate. If the movement speed of the nozzle 6 is fast, the thickness (height) of the stacked layer will be thin (low), and conversely, if the movement speed of the nozzle 6 is slow, the thickness (height) of the stacked layer will be thick (high).

[0055] Furthermore, when the nozzle 6 moves slowly, the temperature of the layered area tends to rise, causing the layer width to widen. Conversely, when the nozzle 6 moves quickly, the temperature of the layered area is kept low, so the layer width tends not to widen. Therefore, the nozzle 6's movement speed is also related to the width of the layer being stacked.

[0056] Furthermore, when forming a melted tip using the heat of an arc discharge created by an arc current of 100A or more and 200A or less, and performing lamination, the range of the predetermined movement speed of the nozzle 6 is preferably 15cm / min or more and 50cm / min or less. By setting the movement speed of the nozzle 6 within this range, it is easier to control the width and thickness of the laminated layers to an appropriate width and thickness.

[0057] Furthermore, considering the voltage, current, and the movement speed of the nozzle 6, the preferred conditions for arc discharge are such that the heat input (J / cm) calculated by the following formula (1) is in the range of 3000 J / cm or more and 10000 J / cm or less. Heat input = [Current (A) × Voltage (V) × 60] / Moving speed (cm / min) ... (1) As can be seen from equation (1) above, the heat input is the amount of heat (thermal energy) supplied per unit length (cm).

[0058] In other words, lamination should ideally be carried out with a heat input in the range of 3000 J / cm or more and 10000 J / cm or less.

[0059] Furthermore, after considering various types of carbon steel wire (WR), it was found that it is preferable for the carbon steel wire (WR) to conform to the AWS standard "A5.18 ER70S-G".

[0060] For example, MG-S50 manufactured by Kobe Steel, Ltd. is a carbon steel wire WR that conforms to the AWS standard "A5.18 ER70S-G".

[0061] By the way, in a fabrication process in which a molten tip is formed by the heat of an arc discharge ARC while supplying a shielding gas SG to the tip of a carbon steel wire WR, and the molten tip is then layered onto the target area to create a fabricated object M, if the layering is repeated continuously, heat accumulates in the layered material, and as a result, the surface temperature of the next layer to be added becomes higher.

[0062] Furthermore, if the next layer is laid on a surface where the surface temperature exceeds 250°C, the bonding strength between layers may decrease.

[0063] Therefore, it is preferable to perform lamination on the target portion of the material at temperatures below 250°C.

[0064] Therefore, the fabrication process for fabricating an object M by layering the molten tip onto the layer to be layered preferably comprises a layering process in which layering is performed on the layer to be layered at a temperature of 250°C or lower, and a cooling process in which, if the layer to be layered is higher than 250°C, the process is to wait until it cools to 250°C or lower.

[0065] Furthermore, since a surface temperature closer to room temperature during lamination tends to improve the bonding strength between layers, the lamination process is preferably performed on the target portion of the lamination at a temperature of 200°C or lower, more preferably 150°C or lower, and even more preferably 100°C or lower.

[0066] The cooling process can be defined as waiting for the material to cool to a temperature below the temperature at which the lamination process takes place. For example, if the lamination process involves laminating a portion of the material that is at a temperature of 200°C or lower, the cooling process can be defined as waiting for the portion of the material to cool to a temperature of 200°C or lower if its temperature is higher than 200°C.

[0067] Figure 6 schematically shows the state of the fabricated object M, which was fabricated under appropriate conditions with 100% argon as the shielding gas SG.

[0068] Note that Figure 6 schematically shows only the part of the molded object M, and other parts such as the base material 5 are omitted from the illustration.

[0069] Specifically, the diagram schematically shows the state of the fabricated object M when the fabrication process conditions (more precisely, the additive manufacturing process conditions) are as follows: the carbon steel wire WR is MG-S50 manufactured by Kobe Steel, Ltd., and the arc discharge ARC is formed by applying a voltage of 12.5V between the carbon steel wire WR and the target area and passing a current of 200A.

[0070] The flow rate of the shielding gas SG is set to 18 SLM, the movement speed of the nozzle 6 is set to 50 cm / min, and the heat input is 3000 J / cm.

[0071] As shown in Figure 6, although there are some areas where slight lines are visible between the stacked layers, the overall layering is excellent with almost no visible lines, and it is possible to create a molded object M with almost no irregular bumps or unevenness.

[0072] Furthermore, the improved shape stability during the molding process allows for the successful creation of complex shapes, such as those shown in Figure 6.

[0073] Furthermore, even when the nozzle 6's movement speed is set to 15 cm / min and the heat input is 10,000 J / cm, a fabricated object M with a good layered state similar to that shown in Figure 6 is obtained.

[0074] The power input (W) when forming an arc discharge can be expressed as the product of voltage (V) and current (A), and the heat input is an index that includes this factor. However, when considering the voltage alone, it is preferable that the voltage is in the range of 12.5 ± 2.5 (V).

[0075] The above description has been based on specific embodiments of this disclosure, but this disclosure is not limited to the embodiments described above.

[0076] For example, in the above embodiment, the case where a DC power supply is used for power supply E was shown, but power supply E may also be an AC power supply.

[0077] Thus, the scope of this disclosure includes modifications and improvements to the embodiments, which will be apparent to those skilled in the art from the claims. [Explanation of symbols]

[0078] 1...Metal 3D printer, 2...Manipulator, 21...Manipulator base, 22...Swing head, 23...Forearm, 24...Upper arm, 25...Wrist, 26...Swivel, 3...Base, 4...Table, 5...Base material, 6...Nozzle, 61...Guide tube, 62...Outer tube, ARC...Arc discharge, B1, B2...Bolts, E...Power supply, M...Printed object, RC1, RC2...Rotation center, SG...Shielding gas, VA...First axis, WR...Carbon steel wire

Claims

1. A method for manufacturing an object using a metal 3D printer, The process includes a molding step in which a shielding gas is supplied to the tip of a carbon steel wire, a molten tip is formed by the heat of an arc discharge, and the molten tip is laminated onto the target portion to form the object, The aforementioned arc discharge is formed by applying a voltage between the carbon steel wire and the target portion, thereby passing a current of 200 A or less. A manufacturing method in which the shielding gas is 100% argon.

2. The manufacturing method according to claim 1, wherein the lamination is performed on the target portion at a temperature of 250°C or lower.

3. The manufacturing method according to claim 1, wherein the carbon steel wire conforms to the AWS standard "A5.18 ER70S-G".

4. The manufacturing method according to any one of claims 1 to 3, wherein the lamination is carried out with a heat input of 3,000 J / cm or more and 10,000 J / cm or less.

5. The lamination is carried out by moving the carbon steel wire and the nozzle that supplies the shielding gas to the target portion at a speed within a predetermined range of movement speeds. The manufacturing method according to claim 4, wherein the predetermined range of the moving speed is 15 cm / min or more and 50 cm / min or less.

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