Laser arc coaxial heat source coupled additive manufacturing device and manufacturing method

Abstract

The present invention relates to the technical field of metal additive manufacturing, and specifically to a laser arc coaxial heat source coupled additive manufacturing device and a manufacturing method. The manufacturing device includes: a ring laser system, which uses a laser to emit laser light and transmits it to a laser mirror group, and the laser mirror group emits a hollow ring laser beam; a rotating tungsten pole TIG welding system, the rotating motor rotates to drive the fixed disk and the tungsten pole to rotate, the fixed disk and the ring laser beam are coaxial, and the tungsten pole passes through the inside of the ring laser beam; a wire feeding system, which is used to transport the metal wire to the molten pool. The present invention utilizes the rotation of the tungsten pole to make the generated TIG arc rotate, and the rotation of the TIG arc and the ring laser beam are coupled to form a coupled heat source. The rotating TIG arc will increase the heated area of ​​the area to be added and increase the cladding efficiency of the ring laser beam. The rotation of the TIG arc will also drive the flow of the molten pool and improve the spreadability of the molten metal. The ring laser beam is conducive to increasing the arc stability of the TIG arc, thereby improving the droplet transition form.

Description

Technical Field

[0001] The present invention relates to the technical field of metal additive manufacturing, and in particular to a laser arc coaxial heat source coupled additive manufacturing device and a manufacturing method. Background Art

[0002] When performing laser additive manufacturing of titanium alloy materials, the high energy density and small heat source range of the ring laser lead to uneven heating of the base material and the metal wire, which can easily lead to problems such as insufficient melting of the metal wire, poor weld formation, and low additive efficiency.

[0003] CN109759707B proposes to use a laser + off-axis TIG heat source composite additive method, which can increase the range of the coupled heat source to a certain extent. However, due to the certain angle between the laser and the TIG heat source, the coupling effect between the two is limited, and the expected additive effect cannot be obtained; in addition, the heat source of the laser + off-axis TIG heat source composite additive method is non-axisymmetric, has a certain directionality, and has poor flexibility. CN116000457B proposes to use a laser coaxial induced multi-TIG arc multi-wire additive manufacturing method, which improves the deposition efficiency by introducing multiple TIG arc heat sources and multiple welding wires, which improves the melting efficiency of the welding wire to a certain extent, but the introduction of multiple TIG arcs does not completely eliminate the directionality of the additive, and will significantly increase the heat input, causing the welding deformation to increase. CN114951905A discloses a device and method for additive manufacturing of composite arc by laser impact stirring a molten pool in a variable direction. Although composite arc additive manufacturing of composite arc by laser impact stirring a molten pool in different directions can be realized through a variable direction rotating device, the laser is emitted at a certain angle on one side and has a certain directionality, which will increase heat input. Moreover, this method of physically rotating the laser is not suitable for situations where the welding direction needs to be changed back and forth. Due to the excessively fast physical rotation, the reliability of the entire system will be poor. Summary of the invention

[0004] In view of this, the present invention aims to propose a laser arc coaxial heat source coupled additive manufacturing device and manufacturing method, in which the central axis of the rotating tungsten pole is coaxial with the annular laser beam, the tungsten pole rotates, and the TIG arc moves along a circular trajectory to increase the heated area, promote the spreading of molten metal, improve the forming of the additive weld, and improve the cladding efficiency of the welding wire.

[0005] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] On the one hand, the present invention provides a laser arc coaxial heat source coupled additive manufacturing device, comprising:

[0007] The ring laser system comprises a laser and a laser mirror assembly, wherein the laser can emit laser light and transmit the laser light to the laser mirror assembly through an optical fiber, and the laser light is emitted to form a hollow ring laser beam under the action of the laser mirror assembly;

[0008] A rotating tungsten electrode TIG welding system comprises a TIG power supply, a controller, a rotating motor, a fixed disk and a tungsten electrode. One end of the TIG power supply is connected to the tungsten electrode, and the other end is connected to the substrate. The controller is connected to the rotating motor, and the tungsten electrode is connected to the fixed disk. The rotation of the rotating motor drives the fixed disk and the tungsten electrode to rotate. The fixed disk and the annular laser beam are coaxial, and the tungsten electrode passes through the inside of the annular laser beam. The TIG power supply is used to generate a TIG arc between the tungsten electrode and the substrate. The rotation of the TIG arc and the annular laser beam are coupled to form a coupled heat source.

[0009] The wire feeding system comprises a metal wire, a wire feeder, a wire guide tube and a wire feeding nozzle. The wire feeder is connected to the metal wire and is used to feed the metal wire through the wire guide tube and the wire feeding nozzle to a molten pool formed by a coupled heat source.

[0010] The present invention utilizes the rotation of the tungsten pole to cause the generated TIG arc to rotate as well, and the rotation of the TIG arc and the annular laser beam are coupled to form a coupled heat source. Compared with the conventional fixed arc, the rotating TIG arc will increase the heating area of ​​the area to be added, thereby increasing the cladding efficiency of the annular laser beam. The rotation of the TIG arc will also drive the flow of the molten pool, improve the spreadability of the molten metal, and thus improve the forming of the weld bead in the area of ​​the added material. The annular laser beam is conducive to increasing the arc stability of the TIG arc, thereby improving the form of the droplet transition.

[0011] Furthermore, the position of the tungsten pole on the fixed disk is variable, so as to adjust the rotation amplitude of the tungsten pole.

[0012] Furthermore, when the center line of the tungsten electrode coincides with the center line of the fixed disk, the tungsten electrode can realize rotation; when the distance between the center line of the tungsten electrode and the center line of the fixed disk is less than the radius of the tungsten electrode, the tungsten electrode rotates eccentrically around the center line of the fixed disk; when the distance between the center line of the tungsten electrode and the center line of the fixed disk is greater than the radius of the tungsten electrode, the tungsten electrode revolves around the center line of the fixed disk. By adjusting the relative position of the tungsten electrode and the center line of the fixed disk, the tungsten electrode can realize rotation, eccentric rotation or revolution. The rotation mode is flexible and changeable. By using different rotation modes of the tungsten electrode, adjusting the rotation amplitude of the TIG arc can adjust the width of the weld in the additive area.

[0013] Furthermore, the fixed disk clamps the tungsten electrode, which facilitates changing the position of the tungsten electrode, thereby adjusting the rotation amplitude of the tungsten electrode.

[0014] Furthermore, the controller is used to adjust the rotation speed of the rotating motor, thereby controlling the rotation speed of the fixed disk, so as to adjust the rotation period of the tungsten electrode and adjust the single-layer cladding amount in the additive area.

[0015] Furthermore, the annular laser beam radiates to form an annular spot on the substrate, and the rotation frequency of the tungsten pole, the rotation amplitude of the tungsten pole, the outer diameter of the annular spot and the light band width of the annular spot are set according to the additive width. The setting parameters are shown in the following table.

[0016]

[0017] Furthermore, the TIG arc and the ring laser beam are both perpendicular to the substrate, the coupled heat source has no directionality, and the flexibility of additive manufacturing is greatly increased.

[0018] Another invention, the present invention also proposes a laser arc coaxial heat source coupled additive manufacturing method, which is applied to the above-mentioned laser arc coaxial heat source coupled additive manufacturing device, and the manufacturing method comprises the following steps:

[0019] S1. Pre-treating the substrate;

[0020] S2. Start the annular laser system, the laser emits a laser beam and transmits it to the laser mirror group through an optical fiber, the laser mirror group emits a centrally controlled annular laser beam, the annular laser beam radiates on the substrate to form an annular spot, and the annular spot heats the base material to form a molten pool;

[0021] S3. Start the rotating tungsten electrode TIG welding system, generate a TIG arc between the tungsten electrode and the substrate, and under the control of the controller, the rotating motor drives the fixed plate and the tungsten electrode to rotate. According to the process requirements and the width of the additive material, set the TIG current, tungsten electrode rotation period, tungsten electrode rotation amplitude, the outer diameter of the annular light spot, and the light band width of the annular light spot;

[0022] S4. A TIG arc is generated between the tungsten electrode and the substrate, and the TIG arc rotation and the annular laser beam are coupled to form a coupled heat source;

[0023] S5. Start the wire feeding system. Driven by the wire feeder, the metal wire is fed into the molten pool formed by the coupled heat source, and melted under the action of the coupled heat source to form an additive weld.

[0024] Furthermore, in step S1, the pretreatment process is to acid-wash and degrease the substrate, and then use a hard grinding head to remove the surface oxide layer of the area to be added on the substrate until a bright metallic color appears, and finally wipe it with alcohol or acetone.

[0025] Compared with the prior art, the laser arc coaxial heat source coupled additive manufacturing device and manufacturing method described in the present invention have the following advantages:

[0026] (1) The rotating TIG arc and the annular laser beam couple to form a coupled heat source. The rotating TIG arc can increase the heating area of ​​the area to be added, thereby increasing the cladding efficiency of the annular laser beam. The rotation of the TIG arc will also drive the flow of the molten pool, improve the spread of the molten metal, and thus improve the formation of the weld in the additive area. The annular laser beam is conducive to increasing the arc stability of the TIG arc, thereby improving the form of the droplet transition.

[0027] (2) By adjusting the position of the tungsten electrode on the fixed disk, the tungsten electrode can achieve rotation, eccentric rotation or revolution, and the rotation mode is flexible and changeable.

[0028] (3) Adjusting the rotation amplitude of the TIG arc can adjust the width of the weld in the additive area, and adjusting the rotation period of the TIG arc can adjust the single-layer cladding amount in the additive area, thereby achieving effective control and regulation of the additive process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 It is a schematic structural diagram of a laser arc coaxial heat source coupled additive manufacturing device according to the present invention;

[0031] Figure 2 This is a schematic diagram of the change in the tungsten pole rotation trajectory within one rotation cycle.

[0032] Description of reference numerals:

[0033] 1. TIG power supply; 2. Laser; 3. Controller; 4. Rotating motor; 5. Fixed plate; 6. Tungsten electrode; 7. Laser mirror group; 8. Ring laser beam; 9. Metal wire; 10. Wire feeder; 11. Area to be added; 12. Molten pool; 13. Ring-shaped spot; 14. Additive area; 15. Substrate; 16. Tungsten electrode rotation trajectory; 17. Tungsten electrode center line; 18. TIG arc. DETAILED DESCRIPTION

[0034] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments. The embodiments described in the present invention are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0035] It should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "rear", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0036] like Figure 1 As shown, the present invention provides a laser arc coaxial heat source coupled additive manufacturing device, comprising:

[0037] The ring laser system comprises a laser 2 and a laser mirror assembly 7. The laser 2 can emit laser light and transmit the laser light to the laser mirror assembly 7 through an optical fiber. Under the action of the laser mirror assembly 7, the laser light is emitted to form a hollow ring laser beam 8.

[0038] A rotating tungsten electrode TIG welding system comprises a TIG power supply 1, a controller 3, a rotating motor 4, a fixed disk 5 and a tungsten electrode 6, wherein one end of the TIG power supply 1 is connected to the tungsten electrode 6, and the other end is connected to the substrate 15, the controller 3 is connected to the rotating motor 4, the tungsten electrode 6 is connected to the fixed disk 5, the rotating motor 4 rotates to drive the fixed disk 5 and the tungsten electrode 6 to rotate, the fixed disk 5 and the annular laser beam 8 are coaxial, the tungsten electrode 6 passes through the inside of the annular laser beam 8, the TIG power supply 1 is used to generate a TIG arc 18 between the tungsten electrode 6 and the substrate 15, and the rotation of the TIG arc 18 and the annular laser beam 8 are coupled to form a coupled heat source;

[0039] The wire feeding system includes a metal wire 9, a wire feeder 10, a wire guide tube and a wire feeding nozzle. The wire feeder 10 is connected to the metal wire 9 and is used to transport the metal wire 9 through the wire guide tube and the wire feeding nozzle to a molten pool 12 formed by a coupled heat source.

[0040] In the prior art, the annular laser beam 8 radiates on the substrate 15 to form an annular spot 13, and the annular spot 13 heats the base material to form a molten pool 12. Due to the high energy density of the laser, the simple annular laser heat source has a small range, which is prone to problems such as insufficient melting of the metal wire and low additive efficiency. The laser arc coaxial heat source coupled additive manufacturing device of the present invention utilizes the rotation of the tungsten pole 6 to cause the generated TIG arc 18 to rotate as well, and the rotation of the TIG arc 18 and the annular laser beam 8 are coupled to form a coupled heat source. Compared with the conventional fixed arc, the rotating TIG arc 18 will increase the heated area of ​​the area to be added 11, thereby increasing the cladding efficiency of the annular laser beam 8. The rotation of the TIG arc 18 will also drive the flow of the molten pool 12, improve the spreadability of the molten metal, and thus improve the forming of the weld bead in the additive area 14. For situations where the welding direction needs to be changed, the rotating TIG arc 18 eliminates the directionality, improves the operation flexibility and system reliability. The ring-shaped laser beam 8 is beneficial to increasing the arc stability of the TIG arc 18, thereby improving the droplet transfer form.

[0041] A plurality of lens groups are arranged in the laser lens group 7 , and through refraction and reflection between the plurality of lens groups, the laser lens group 7 emits a hollow ring-shaped laser beam 8 .

[0042] As a preferred example of the present invention, the position of the tungsten electrode 6 on the fixed disk 5 is variable. By adjusting the position of the tungsten electrode 6 on the fixed disk 5, the rotation amplitude of the tungsten electrode 6 can be adjusted. When the center line 17 of the tungsten electrode coincides with the center line of the fixed disk 5, the tungsten electrode 6 can realize self-rotation; when the distance between the center line 17 of the tungsten electrode and the center line of the fixed disk 5 is less than the radius of the tungsten electrode 6, the tungsten electrode 6 rotates eccentrically around the center line of the fixed disk 5; when the distance between the center line 17 of the tungsten electrode and the center line of the fixed disk 5 is greater than the radius of the tungsten electrode 6, the tungsten electrode 6 revolves around the center line of the fixed disk 5. By adjusting the relative position of the tungsten electrode 6 and the center line of the fixed disk 5, the tungsten electrode 6 can realize self-rotation, eccentric rotation or revolution, and the rotation mode is flexible and changeable. By using different rotation modes of the tungsten electrode 6, adjusting the rotation amplitude of the TIG arc 18 can adjust the width of the weld bead in the additive area 14.

[0043] Since the fixed disk 5 and the annular laser beam 8 are coaxial, that is, the center line of the fixed disk 5 and the center line of the annular laser beam 8 are coaxial, when the fixed disk 5 drives the tungsten pole 6 to rotate, the tungsten pole 6 rotates around the central axis of the fixed disk 5. During the rotation process, the center line of the tungsten pole rotation trajectory 16 is always coaxial with the annular laser beam 8.

[0044] The controller 3 is used to adjust the rotation speed of the rotating motor 4, thereby controlling the rotation speed of the fixed disk 5 to adjust the rotation period of the tungsten electrode 6, and correspondingly adjust the rotation period of the TIG arc 18. By adjusting the rotation period of the TIG arc 18, the single-layer cladding amount of the additive area 14 can be adjusted. The rotation amplitude and rotation period of the TIG arc 18 of the present invention are adjustable, thereby achieving effective control and regulation of the additive process. Figure 2 FIG. 2 shows the change of the tungsten pole rotation trajectory 16 within one rotation cycle.

[0045] Furthermore, the fixing plate 5 clamps the tungsten electrode 6 to facilitate changing the position of the tungsten electrode 6 , thereby adjusting the rotation amplitude of the tungsten electrode 6 .

[0046] For different additive widths, the rotation frequency and rotation amplitude of the tungsten electrode 6, the outer diameter of the annular light spot 13 and the light band width are set according to Table 1. By adjusting the above parameters, effective control and adjustment of the additive process is achieved. Specifically, the light band width of the annular light spot 13 described in the present invention refers to the distance between the outer circle and the inner circle of the annular light spot 13.

[0047] Table 1

[0048]

[0049] As a preferred example of the present invention, the TIG arc 18 and the annular laser beam 8 are both perpendicular to the substrate 15, the coupled heat source has no directionality, and the flexibility of additive manufacturing is greatly increased.

[0050] The present invention also discloses a laser arc coaxial heat source coupled additive manufacturing method, which is applied to the above-mentioned laser arc coaxial heat source coupled additive manufacturing device. The manufacturing method comprises the following steps:

[0051] S1. Pre-treating the substrate 15;

[0052] Specifically, in step S1, the substrate 15 is pickled and degreased, and then a hard grinding head is used to remove the surface oxide layer of the area 11 to be added on the substrate 15 until a bright metallic color appears, and finally alcohol or acetone is used to wipe the area 11 to be added and its surrounding areas.

[0053] S2. Start the annular laser system, the laser 2 emits a laser beam and transmits it to the laser mirror group 7 through an optical fiber, the laser mirror group 7 emits a centrally controlled annular laser beam 8, the annular laser beam 8 radiates on the substrate 15 to form an annular spot 13, and the annular spot 13 heats the base material to form a molten pool 12;

[0054] Specifically, in step S2, the working distance between the laser lens group 7 and the substrate 15 is set according to the process requirements to ensure that the annular laser beam 8 can radiate to form an annular spot 13 on the substrate 15. At the same time, the outer diameter of the annular spot 13, laser power and other parameters are set according to the process requirements.

[0055] S3. Start the rotating tungsten electrode TIG welding system, generate a TIG arc 18 between the tungsten electrode 6 and the substrate 15, and under the control of the controller 3, the rotating motor 4 drives the fixed plate 5 and the tungsten electrode 6 to rotate, and set the TIG current, the rotation period of the tungsten electrode 6, the rotation amplitude of the tungsten electrode 6, the outer diameter of the annular light spot 13, and the light band width of the annular light spot 13 according to the process requirements and the additive width;

[0056] S4. A TIG arc 18 is generated between the tungsten electrode 6 and the substrate 15, and the TIG arc 18 rotates and couples with the annular laser beam 8 to form a coupled heat source;

[0057] S5. Start the wire feeding system. Driven by the wire feeder 10, the metal wire 9 is fed into the molten pool 12 formed by the coupled heat source, and melted under the action of the coupled heat source to form an additive weld.

[0058] By using a laser arc coaxial heat source coupled additive manufacturing device and manufacturing method of the present invention, each system works in coordination to finally obtain the expected additive weld bead forming. The present invention can be used not only for additive manufacturing, but also for surfacing, surface treatment and modification of titanium alloy materials.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser arc coaxial heat source coupled additive manufacturing device, characterized in that: include: A ring-shaped laser system, comprising a laser (2) and a laser mirror assembly (7), wherein the laser (2) is capable of emitting laser light and transmitting the laser light to the laser mirror assembly (7) via an optical fiber, and under the action of the laser mirror assembly (7), the laser light is emitted to form a hollow ring-shaped laser beam (8); A rotating tungsten electrode TIG welding system comprises a TIG power supply (1), a controller (3), a rotating motor (4), a fixed disk (5) and a tungsten electrode (6), wherein one end of the TIG power supply (1) is connected to the tungsten electrode (6) and the other end is connected to a substrate (15), the controller (3) is connected to the rotating motor (4), the tungsten electrode (6) is connected to the fixed disk (5), the rotating motor (4) rotates to drive the fixed disk (5) and the tungsten electrode (6) to rotate, the fixed disk (5) and the annular laser beam (8) are coaxial, the tungsten electrode (6) passes through the inside of the annular laser beam (8), the TIG power supply (1) is used to generate a TIG arc (18) between the tungsten electrode (6) and the substrate (15), the rotation of the tungsten electrode (6) causes the generated TIG arc (18) to rotate, and the rotation of the TIG arc (18) and the annular laser beam (8) are coupled to form a coupled heat source; A wire feeding system comprises a metal wire (9), a wire feeder (10), a wire guide tube and a wire feeding nozzle, wherein the wire feeder (10) is connected to the metal wire (9) and is used to feed the metal wire (9) through the wire guide tube and the wire feeding nozzle to a molten pool (12) formed by a coupled heat source, wherein the metal wire (9) is fed into the molten pool (12) on the side of a ring-shaped laser beam (8).

2. The laser arc coaxial heat source coupled additive manufacturing device according to claim 1, characterized in that: The position of the tungsten pole (6) on the fixed disk (5) is variable, and is used to adjust the rotation amplitude of the tungsten pole (6).

3. The laser arc coaxial heat source coupled additive manufacturing device according to claim 2, characterized in that: When the center line of the tungsten pole (17) coincides with the center line of the fixed disk (5), the tungsten pole (6) can realize rotation; when the distance between the center line of the tungsten pole (17) and the center line of the fixed disk (5) is less than the radius of the tungsten pole (6), the tungsten pole (6) rotates eccentrically around the center line of the fixed disk (5); when the distance between the center line of the tungsten pole (17) and the center line of the fixed disk (5) is greater than the radius of the tungsten pole (6), the tungsten pole (6) revolves around the center line of the fixed disk (5).

4. The laser arc coaxial heat source coupled additive manufacturing device according to claim 2, characterized in that: The fixed disk (5) clamps the tungsten electrode (6).

5. The laser arc coaxial heat source coupled additive manufacturing device according to claim 1, characterized in that: The controller (3) is used to adjust the rotation speed of the rotating motor (4), thereby controlling the rotation speed of the fixed disk (5) to adjust the rotation period of the tungsten pole (6).

6. The laser arc coaxial heat source coupled additive manufacturing device according to claim 1, characterized in that: The annular laser beam (8) radiates to form an annular light spot (13) on the substrate (15). The rotation frequency of the tungsten pole (6), the rotation amplitude of the tungsten pole (6), the outer diameter of the annular light spot (13) and the light band width of the annular light spot (13) are set according to the width of the additive material. The setting parameters are shown in the following table:

7. The laser arc coaxial heat source coupled additive manufacturing device according to claim 1, characterized in that: The TIG arc (18) and the annular laser beam (8) are both perpendicular to the substrate (15).

8. A laser arc coaxial heat source coupled additive manufacturing method, applied to the laser arc coaxial heat source coupled additive manufacturing device according to any one of claims 1 to 7, characterized in that: The manufacturing method comprises the following steps: S1. Pre-treating the substrate (15); S2. Start the annular laser system, the laser (2) emits a laser beam and transmits it to the laser mirror group (7) through an optical fiber, the laser mirror group (7) emits a centrally controlled annular laser beam (8), the annular laser beam (8) radiates on the substrate (15) to form an annular light spot (13), and the annular light spot (13) heats the base material to form a molten pool (12); S3. Start the rotating tungsten electrode TIG welding system, generate a TIG arc (18) between the tungsten electrode (6) and the substrate (15), and under the control of the controller (3), the rotating motor (4) drives the fixed plate (5) and the tungsten electrode (6) to rotate, and set the TIG current, the tungsten electrode (6) rotation period, the tungsten electrode (6) rotation amplitude, the outer diameter of the annular light spot (13), and the light band width of the annular light spot (13) according to the process requirements and the additive width; S4. A TIG arc (18) is generated between the tungsten electrode (6) and the substrate (15), and the TIG arc (18) rotates and couples with the annular laser beam (8) to form a coupled heat source; S5. The wire feeding system is started. Driven by the wire feeder (10), the metal wire (9) is fed into the molten pool (12) formed by the coupled heat source, and melted under the action of the coupled heat source to form an additive weld.

9. The laser arc coaxial heat source coupled additive manufacturing method according to claim 8, characterized in that: In step S1, the pretreatment process is to acid-wash and degrease the substrate (15), then use a hard grinding head to remove the surface oxide layer of the area (11) to be added on the substrate (15) until a bright metallic color appears, and finally wipe it with alcohol or acetone.

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