Coaxial powder delivery head with variable powder spots

Abstract

The utility model relates to the technical field of laser additive manufacturing, and specifically to a coaxial powder feeding head with variable powder spot, comprising: a nozzle, wherein the interior of the nozzle is provided with a first powder feeding channel, a second powder feeding channel and a channel for laser to pass through, wherein the first powder feeding channel and the second powder feeding channel are not connected to each other; a powder feeding component, comprising a powder feeding pipe and an air intake pipe, wherein the powder feeding pipe and the air intake pipe are respectively connected to the first powder feeding channel or the second powder feeding channel. The present application assembles three nozzles in a mutually nested manner to form a nozzle, and forms two independent powder feeding channels, wherein the powder feeding pipe and the air intake pipe in the powder feeding component are respectively connected to one of the two powder feeding channels, i.e., one for powder feeding and the other for air feeding, and by changing the position of the powder feeding component, the media transported by the two powder feeding channels can be switched to each other, thereby realizing the switching between large powder spot and small powder spot, without disassembling the powder feeding pipeline and the nozzle, and thus ensuring the continuity of processing.

Description

Technical Field

[0001] The utility model relates to the technical field of laser additive manufacturing, in particular to a coaxial powder feeding head with variable powder spots. Background Art

[0002] Laser additive technology has a wide range of applications in the industrial field. In the laser additive process, a larger spot is often used to improve production efficiency. In precision printing and molding, a small spot must be replaced for processing. When the spot size changes, in order to ensure the powder utilization rate, the powder spot also needs to change accordingly. Precision processing is performed through a small spot and a small powder spot.

[0003] The common practice at present is to replace the powder feeding nozzle under the cladding head. Since the powder feeding nozzle needs to be connected to the powder inlet pipe and the cooling water pipe, it needs to be removed one by one during replacement, and then the nozzle needs to be removed from the cladding head, replaced with a new nozzle, and then the powder inlet pipe and the cooling water pipe need to be reconnected to adjust the powder spot position. The operation is extremely inconvenient, seriously affecting production efficiency and failing to meet actual needs. Summary of the invention

[0004] In view of the technical problems existing in the powder feeding structure in the prior art, the first aspect of the utility model proposes a coaxial powder feeding head with variable powder spots, comprising:

[0005] A nozzle, wherein a first powder feeding channel, a second powder feeding channel and a channel for laser to pass through are provided inside the nozzle, and the first powder feeding channel and the second powder feeding channel are not connected to each other;

[0006] A powder feeding component, comprising a powder feeding pipe and an air feeding pipe, wherein the powder feeding pipe and the air feeding pipe are respectively connected to the first powder feeding channel or the second powder feeding channel;

[0007] The powder feeding component is configured to be switchable between a first position and a second position, and when the powder feeding component is switched between the first position or the second position, the positions of the powder feeding pipe and the air inlet pipe are swapped, so that the connection state between the first powder feeding channel, the second powder feeding channel and the corresponding powder feeding pipe or air inlet pipe is switched;

[0008] The powder spots formed by powder delivery through the first powder delivery channel are larger than the powder spots formed by powder delivery through the second powder delivery channel.

[0009] Preferably, the nozzle includes a first nozzle, a second nozzle and a third nozzle, a first cavity is provided on the inner side of the first nozzle, the first powder delivery channel is provided inside the first nozzle, a connecting channel is also provided in the first nozzle, a first end of the connecting channel is connected to the powder inlet pipe or the air inlet pipe, and a second end is connected to the powder inlet end of the second powder delivery channel; the second nozzle is connected in the first cavity, a second cavity is provided on the inner side of the second nozzle; the third nozzle is connected in the second cavity, and a second powder delivery channel is formed between the inner wall of the second nozzle and the outer wall of the third nozzle, and the channel for the laser to pass through is provided on the inner side of the third nozzle.

[0010] Preferably, the size of the first cavity at the first end of the first nozzle is larger than that at the second end, the second nozzle is assembled into the first cavity from the first end of the first nozzle, the size of the second cavity at the first end of the second nozzle is larger than that at the second end, the third nozzle is assembled into the second cavity from the first end of the second nozzle and is connected to the first nozzle, and the third nozzle has a portion that is higher than the end face of the first end of the first nozzle.

[0011] Preferably, the powder feeding component is constructed in an annular shape and is connected to the outer wall of the third nozzle, and can be transmitted along its axis relative to the third nozzle. When the powder feeding component is transmitted around the axis of the third nozzle by a predetermined angle, the first position and the second position are switched mutually.

[0012] Preferably, the outer wall of the third nozzle is provided with a threaded connection structure, and a pressure plate is provided on the threaded connection structure. When the pressure plate is tightened on the threaded connection structure, it can press the powder feeding component to keep the powder feeding component in the first position or the second position.

[0013] Preferably, the first end of the connecting channel is connected to the upper end surface of the first nozzle, the first end of the first powder feeding channel is connected to the upper end surface of the first nozzle, and the powder feed end of the connecting channel and the powder feed end corresponding to the first powder feeding channel are centrally symmetrically distributed.

[0014] Preferably, a gasket is provided between the powder feeding component and the first nozzle, and a plurality of through holes are provided on the gasket, and the through holes are distributed corresponding to the connecting channel and the first powder feeding channel.

[0015] Preferably, the first powder delivery channel extends from a first end surface to a second end surface of the first nozzle, and the first powder delivery channel is constructed to include a plurality of independent tubular channels distributed in an axisymmetric manner.

[0016] Preferably, a powder delivery pipe is provided in the tubular channel, and a step groove is provided at the bottom of the tubular channel, and the outer diameter of the step of the step groove is equal to the outer diameter of the powder delivery pipe.

[0017] Preferably, the inner wall surface of the second nozzle includes a first conical surface with an inner diameter gradually decreasing, and the outer wall surface of the third nozzle includes a second conical surface with an inner diameter gradually decreasing, and an annular channel with a diameter gradually decreasing from the first end to the second end is formed between the first conical surface and the second conical surface, and an annular cavity is provided above the annular channel, and the annular cavity is connected to the connecting channel.

[0018] Preferably, the second end of the second nozzle is provided with a first step, the first step is connected to the inner wall of the first nozzle and limits the second nozzle from continuously moving toward the second end of the first nozzle, the third nozzle is provided with a second step, the second step abuts against the first end face of the second nozzle and limits the second nozzle from moving toward the first end of the first nozzle, and the third nozzle and the first nozzle are connected by bolts.

[0019] Preferably, a water cooling cavity is provided between the second nozzle and the first nozzle, and a water inlet hole and a water outlet hole are provided on an outer wall of the first nozzle, and the water inlet hole and the water outlet hole are communicated with the water cooling cavity.

[0020] Compared with the prior art, the advantages of the utility model are:

[0021] The present application assembles three nozzles in a nested manner to form a nozzle, which has a compact structure and can be used in smaller working holes. The nozzle forms two independent powder delivery channels, and the powder delivery pipe and air delivery pipe in the powder feeding component are respectively connected to one of the two powder delivery channels, that is, one for powder delivery and the other for air delivery. By changing the position of the powder feeding component, the media transported by the two powder delivery channels can be switched with each other, thereby realizing the switching between large powder spots and small powder spots. There is no need to disassemble the powder delivery pipe and the nozzle, and the continuity of processing can be ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings are not intended to be drawn to scale. In the accompanying drawings, each identical or nearly identical component shown in various figures may be represented by the same reference numeral. For the sake of clarity, not every component is labeled in each figure. Now, embodiments of various aspects of the utility model will be described by way of example and with reference to the accompanying drawings, in which:

[0023] Figure 1 It is a schematic diagram of a coaxial powder feeding head with variable powder spots shown in the utility model;

[0024] Figure 2 It is an exploded view of the coaxial powder feeding head with variable powder spots shown in the utility model;

[0025] Figure 3 It is a distribution diagram of the powder inlet pipe and the air inlet pipe shown in the utility model;

[0026] Figure 4It is a cross-sectional view of the plane where the first powder feeding channel shown in the utility model is located;

[0027] Figure 5 It is a cross-sectional view of the plane where the connecting channel shown in the utility model is located;

[0028] Figure 6 It is a schematic diagram of the air supply and powder supply paths shown in the utility model. DETAILED DESCRIPTION

[0029] In order to better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0030] In the process of printing and forming large-size parts, large-size light spots and powder spots can improve production efficiency. Large-size workpieces also have areas with fine structures, so small-size light spots must be used for processing, and corresponding small-size powder spots are also required to ensure the utilization rate of powder. At present, the switching between large and small powder spots generally requires the disassembly of the powder inlet pipe and powder delivery nozzle. When the precision parts and large-size parts of the printed structural parts are frequently switched during the printing steps, the above-mentioned disassembly and replacement will seriously affect the production efficiency and cannot meet the actual production needs.

[0031] Therefore, the utility model aims to provide a powder feeding structure that can switch the size of the powder spot to be delivered, especially to complete the switching between large powder spots and small powder spots without disassembling the powder feeding tube and the nozzle. The present application arranges the powder feeding head to include two powder feeding channels, one of which can form a large powder spot, and the other can form a small powder spot. The two powder feeding channels are independent of each other, and the powder feeding pipe and the air feeding pipe are respectively connected to the two powder feeding channels. The switching between large powder spots and small powder spots is achieved by converting the connection status of the powder feeding pipe and the air feeding pipe with the two powder feeding channels, and at the same time, the other powder feeding channel is used to deliver protective gas. While protecting the molten pool, it can prevent the powder feeding channel that is not in the state of conveying powder from entering impurities such as spatter or smoke.

[0032] [Coaxial powder delivery head with variable powder spots]

[0033] Combination Figure 1-2 As shown, the first aspect of the utility model provides a coaxial powder feeding head with variable powder spots, comprising a first nozzle 1, a second nozzle 2, a third nozzle 3 and a powder feeding component 5. The powder feeding head is formed by the mutual nesting of the three nozzles, and two independent powder feeding channels are formed. The powder spots formed when the two independent channels feed powder have different sizes. The powder feeding component 5 is connected to the two independent powder feeding channels, and the powder feeding component 5 can switch the connection state with the two powder feeding channels to determine whether to feed air or powder to one of the powder feeding channels.

[0034] Combination Figure 4As shown, a first cavity is provided on the inner side of the first nozzle 1, and a first powder delivery channel 11 is provided inside the first nozzle 1; the second nozzle 2 is connected in the first cavity, and a second cavity is provided on the inner side of the second nozzle 2; the third nozzle 3 is connected in the second cavity, and a second powder delivery channel is formed between the inner wall of the second nozzle 2 and the outer wall of the third nozzle 3, and a channel 301 for the laser to pass through is provided on the inner side of the third nozzle 3.

[0035] It can be understood that the first powder feeding channel 101 and the second powder feeding channel can both transport powder or gas. In order to achieve the formation of two sizes of powder spots, the flow rates of the first powder feeding channel 101 and the second powder feeding channel are set to be large and small. For example, if the flux of the first powder feeding channel 101 is large, the size of the powder spot formed after the powder is transported from the first powder feeding channel 101 will be large. In this way, when the first powder feeding channel 101 and the second powder feeding channel are switched to transport powder, large-sized powder spots or small-sized powder spots are formed. In combination with the large-sized or small-sized laser spots output from the channel 301, small-sized fine processing and forming or large-sized processing and forming can be performed.

[0036] In the following embodiments, it is defined that the powder spots formed by powder feeding through the first powder feeding channel 11 are larger than the powder spots formed by powder feeding through the second powder feeding channel.

[0037] Further, combined with Figure 3 and 5 As shown, the powder feeding component 5 includes a powder feeding pipe 51 and an air inlet pipe 52; wherein, a connecting channel 101 is also provided in the first nozzle 1, and a first end of the connecting channel 101 is connected to the powder feeding pipe 51 or the air inlet pipe 52, and a second end is connected to the powder feeding end of the second powder feeding channel.

[0038] In this way, through the connection function of the connecting channel 101, the powder feeding end of the second powder feeding channel and the powder feeding end of the first powder feeding channel are placed in a position that is conducive to the mutual switching of the powder feeding pipe 51 and the air intake pipe 52 of the powder feeding component 5.

[0039] Furthermore, the powder feeding component 5 is configured to be switchable between a first position and a second position, and when the powder feeding component 5 is switched between the first position or the second position, the positions of the powder feeding pipe 51 and the air intake pipe 52 are interchanged, so that the connection status of the first powder feeding channel 11, the second powder feeding channel and the corresponding powder feeding pipe 51 or the air intake pipe 52 is switched.

[0040] In an optional embodiment, a positioning hole is provided on the first nozzle 1, the second nozzle 2 or the third nozzle 3, and a ball head screw is installed on the powder feeding component 5, which can cooperate with the positioning hole to achieve a suitable angle position when switching the powder feeding mode.

[0041] In this way, when large-size processing is required, the powder feeding component 5 is adjusted to the first position. At this time, the powder feeding pipe 51 is connected to the first powder feeding channel, and the air intake pipe 52 is connected to the second powder feeding channel. After the first powder feeding channel feeds powder, a large-size powder spot is formed, and a large-size light spot is formed to form a large-size processing. The second powder feeding channel is fed with air by the air intake pipe 52 to form a protective gas around the molten pool, while also preventing splashes and smoke from entering and adhering to the inner wall of the second powder feeding channel.

[0042] It is understandable that if splashes and smoke enter the inner wall of the powder feeding channel, the powder feeding path, that is, the powder convergence point, will be changed, and even serious powder feeding flow changes or blockages will be caused. Therefore, it is very necessary to transport protective gas in the first powder feeding channel 11 and the second powder feeding channel that is in a non-powder feeding state.

[0043] In an optional embodiment, in combination with Figure 1-2 As shown, the size of the first cavity at the first end of the first nozzle 1 is larger than that at the second end, the second nozzle 2 is assembled into the first cavity from the first end of the first nozzle 1, the size of the second cavity at the first end of the second nozzle is larger than that at the second end, the third nozzle 3 is assembled into the second cavity from the first end of the second nozzle 2 and is connected to the first nozzle 1, and the third nozzle 3 has a portion that is higher than the end face of the first end of the first nozzle 1.

[0044] In this way, the main body of the powder delivery head can be assembled by sequentially assembling the three parts of the first nozzle 1, the second nozzle 2 and the third nozzle 3, and the assembly is simple and reliable.

[0045] Optionally, the first nozzle 1, the second nozzle 2 and the third nozzle 3 are made of copper or chromium-zirconium-copper.

[0046] Specifically, Figure 4 As shown, the first nozzle 1 is constructed with an outer contour whose upper portion is cylindrical and whose lower portion is conical, and the inner contour and the outer contour are approximately contour-matching structures. In particular, a step structure is provided at the bottom of the inner contour of the first nozzle 1, and the second nozzle 2 is constructed as a thin-walled structure with a cylindrical upper portion and a conical lower portion. A first step 21 is provided at the bottom of the second nozzle 2. When the second nozzle 2 is assembled from top to bottom into the first cavity of the first nozzle 1, the step structure can engage the first step 21 to limit the second nozzle 2 from continuously moving toward the second end of the first nozzle 1, thereby achieving axial limitation on one end of the second nozzle 2.

[0047] Furthermore, the third nozzle 3 is provided with a second step 31, and the second step 31 abuts against the upper end surface of the second nozzle 2 to limit the second nozzle from moving toward the first end of the first nozzle 1, thereby forming a limit on the other end of the second nozzle 2. The third nozzle 3 and the first nozzle 1 are connected by bolts. When the bolts are tightened, the first nozzle 1, the second nozzle 2 and the third nozzle 3 form an integrated structure.

[0048] Furthermore, below the second step 13, the third nozzle 3 is configured to have a recessed portion 33, below the recessed portion 33, the third nozzle 3 is configured to have a gradually narrowing conical shape, and above the second step 13, the third nozzle 3 is configured to be approximately cylindrical.

[0049] Preferably, sealing rings are added at the connection between the second nozzle 2 and the first nozzle 1 below and at the connection between the second nozzle and the first nozzle 1 above, so as to form a sealed water-cooling chamber 102 between the second nozzle 2 and the first nozzle 1, and the outer wall of the first nozzle 1 is provided with a water inlet hole 12 and a water outlet hole, and the water inlet hole 12 and the water outlet hole are connected to the water-cooling chamber 102.

[0050] In this way, the nozzle can be cooled by connecting to a water circulation system through the water inlet and outlet holes.

[0051] In an optional embodiment, the first powder delivery channel 11 extends from the first end face to the second end face of the first nozzle 1, and the first powder delivery channel 11 is configured to include a plurality of independent tubular channels distributed in an axisymmetric manner. In this way, the powder delivered from the powder delivery pipe 51 can directly enter the tubular channel, be transported downward along the axis direction of the tubular channel, and finally converge into powder spots.

[0052] Preferably, a powder delivery pipe is provided in the tubular channel, and a step groove is provided at the bottom of the tubular channel, and the step outer diameter of the step groove is equal to the outer diameter of the powder delivery pipe. In this way, the powder delivery pipe can be assembled into the tubular channel, and powder delivery pipes with different inner diameters can be replaced according to processing requirements to change the conveying capacity of the powder delivery pipe and change the size of the powder spot.

[0053] Furthermore, the inner wall surface of the second nozzle 2 includes a first conical surface with an inner diameter that gradually decreases, and the outer wall surface of the third nozzle 3 includes a second conical surface with an inner diameter that gradually decreases, that is, the outer wall surface of the third nozzle 3 is a conical surface formed below the recessed portion 33, and an annular channel 202 is formed between the first conical surface and the second conical surface, the diameter of which gradually decreases from the first end to the second end, and an annular cavity 201 is provided above the annular channel 202, and the annular cavity 201 is connected to the connecting channel 101.

[0054] In this way, the powder can enter the annular cavity 201 from the connecting channel 101, and be transported downward from the annular channel 202, and gather into small-sized powder spots along the extension direction of the annular channel.

[0055] The first powder feeding channel and the second powder feeding channel formed in this way have good powder convergence and water cooling structure, which can ensure the long-term stable use of the nozzle.

[0056] Combination Figure 2As shown, the powder feeding component 5 is constructed in an annular shape and is connected to the outer wall of the third nozzle 3, and can be transmitted along its axis relative to the third nozzle 3. When the powder feeding component 5 is transmitted around the axis of the third nozzle 3 by a predetermined angle, the first position and the second position are switched mutually.

[0057] It can be understood that when the powder feeding end of the first powder feeding channel 11 and the powder feeding end of the connecting channel 101 are in a centrally symmetrically distributed position, the powder feeding component 5 only needs to transmit a predetermined angle to switch the connection status of all powder feeding pipes 51, air intake pipes 52 and the first powder feeding channel 11 and the second powder feeding channel.

[0058] Optionally, the first end of the connecting channel 101 is connected to the upper end surface of the first nozzle 1, and the first end of the first powder delivery channel 11 is connected to the upper end surface of the first nozzle 1. A gasket 4 is provided between the powder feeding component 5 and the first nozzle 1, and a plurality of through holes are provided on the gasket 4. The through holes are distributed corresponding to the connecting channel 101 and the first powder delivery channel 11, and the through holes corresponding to the connecting channel 101 and the through holes corresponding to the first powder delivery channel 11 are distributed at equal intervals.

[0059] Optionally, the gasket 4 is made of polytetrafluoroethylene, and the gasket 4 and the first nozzle 1 are positioned by a positioning pin.

[0060] In other embodiments, the first end of the connecting channel 101 and the first end of the first powder delivery channel 11 can also be connected to the side of the first nozzle 1, and the powder inlet pipe 51 and the air inlet pipe 52 of the powder feeding component 5 can be correspondingly arranged on the side of the first nozzle 1, and the powder delivery state can also be switched after the powder feeding component 5 completes the relative angle rotation.

[0061] Specifically, eight holes are formed on the upper end surface of the first nozzle 1, four of which are powder inlets of the first powder feeding channel 11, and the other four are powder inlets of the connecting channel 101. The eight holes are distributed at 45° intervals, and the powder inlet of the first powder feeding channel 11 and the powder inlet of the connecting channel 101 are distributed at intervals. The powder feeding component 5 includes four powder inlet pipes 51 and four air inlet pipes 52, and the air inlet pipes 52 and the powder inlet pipes 51 are distributed at intervals.

[0062] In this way, when the powder feeding component 5 is transmitted by 45°, the powder feeding pipe 51 originally connected to the first powder feeding channel 11 becomes connected to the powder feeding port of the connecting channel 101, and the air inlet pipe 52 originally connected to the powder feeding port of the connecting channel 101 becomes connected to the powder feeding port of the first powder feeding channel 11, thereby realizing the switching of powder feeding / air between the first powder feeding channel 11 and the second powder feeding channel.

[0063] The transmission state of the powder feeding component 5 is controlled so that it switches between the first position and the second position, which can be adjusted manually or by using other automated equipment.

[0064] Further, such as Figure 4-5 As shown, the outer wall of the third nozzle 3 is provided with a threaded connection structure 32, and a pressure plate 6 is provided on the threaded connection structure 32. When the pressure plate 6 is tightened on the threaded connection structure 32, it can press the powder feeding component 5 to keep the powder feeding component 5 in the first position or the second position.

[0065] In this way, when it is necessary to switch the powder spot size, the laser, air supply and powder supply will be paused, the pressure plate 6 will be loosened, the powder feeding component 5 will be driven forty-five degrees, and then the pressure plate 6 will be tightened to realize the switching of powder / air supply between the first powder feeding channel 11 and the second powder feeding channel, the paused laser, air supply and powder supply will be turned on, and switched to a predetermined size of light spot, so that it can switch between large-size printing and fine printing states.

[0066] The loosening of the pressing plate 6 and the powder feeding transmission component 5 can be adjusted manually or by using other automated equipment.

[0067] In the above embodiment, the plane where the lower end face of the first nozzle 1 is located is defined as the powder outflow end face, the outlet of the first powder delivery channel 11 is located at the powder outflow end face, and the outlet of the second powder delivery channel is also located at the powder outflow end face. In this way, the powder can converge downward from the plane where the lower end face of the first nozzle 1 is located at a predetermined angle to form a powder spot of predetermined size and shape, and the outlets of the two channels are in the same plane, avoiding the axial displacement difference between the outlets of the two powder delivery channels, especially avoiding the large difference between the powder convergence points or the attachment of particles due to one of the outlets being too close to the molten pool.

[0068]

Powder feeding method for laser additive manufacturing

[0069] The second aspect of the utility model proposes a technical solution, a powder feeding method for laser additive manufacturing, using the above-mentioned coaxial powder feeding head with variable powder spots, comprising the following steps:

[0070] Step 1: According to the size of the part to be manufactured, choose to use the first spot or the second spot for additive manufacturing;

[0071] Step 2: according to the selected light spot type, the size of the powder spot is switched, and the first powder spot corresponds to the first light spot, and the second powder spot corresponds to the second light spot;

[0072] The steps of switching the powder spot size include:

[0073] Step a, suspend powder feeding and gas feeding;

[0074] Step b, rotating the powder feeding component 5 to switch between the first position and the second position, after the switching is completed, turning on the powder feeding and air feeding to change the powder feeding states of the first powder feeding channel 11 and the second powder feeding channel.

[0075] like Figure 6As shown, at this time, the path indicated by the solid arrow in part A is the air delivery path along the second powder delivery channel, and the path indicated by the hollow arrow in part B is the powder delivery path along the first powder delivery channel. It can be seen that while the first powder delivery channel is delivering powder, the second powder delivery channel is delivering air. When the powder feeding component 5 switches position, the powder delivery and air delivery states of the first powder delivery channel and the second powder delivery channel change, that is, the path indicated by the solid arrow in part A is the powder delivery path along the second powder delivery channel, and the path indicated by the hollow arrow in part B is the air delivery path along the first powder delivery channel.

[0076] In combination with the above embodiments, the present application assembles a nozzle by nesting three nozzles with each other, which has a compact structure and can be used in smaller working holes. The nozzle forms two independent powder delivery channels, and the powder delivery pipe and air delivery pipe in the powder feeding component are respectively connected to one of the two powder delivery channels, that is, one for powder delivery and the other for air delivery. By changing the position of the powder feeding component, the media transported by the two powder delivery channels can be switched with each other, thereby realizing the switching between large powder spots and small powder spots. There is no need to disassemble the powder delivery pipe and the nozzle, thereby ensuring the continuity of processing.

[0077] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. A person with ordinary knowledge in the technical field to which the present invention belongs may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the definition of the claims.

Claims

1. A coaxial powder feeding head with variable powder spots, characterized in that: include: A nozzle, wherein a first powder delivery channel (11), a second powder delivery channel, and a channel (301) for laser light to pass through are provided inside the nozzle, wherein the first powder delivery channel (11) and the second powder delivery channel are not connected to each other; A powder feeding component (5) comprises a powder feeding pipe (51) and an air feeding pipe (52), wherein the powder feeding pipe (51) and the air feeding pipe (52) are respectively connected to the first powder feeding channel (11) or the second powder feeding channel; The powder feeding component (5) is configured to be switchable between a first position and a second position, and when the powder feeding component (5) is switched between the first position or the second position, the positions of the powder feeding pipe (51) and the air intake pipe (52) are swapped, so that the connection state between the first powder feeding channel (11), the second powder feeding channel and the corresponding powder feeding pipe (51) or the air intake pipe (52) is switched; The powder spots formed by powder delivery through the first powder delivery channel (11) are larger than the powder spots formed by powder delivery through the second powder delivery channel.

2. The coaxial powder feeding head with variable powder spots according to claim 1, characterized in that: The nozzle comprises a first nozzle (1), a second nozzle (2) and a third nozzle (3); a first cavity is provided inside the first nozzle (1); the first powder delivery channel (11) is provided inside the first nozzle (1); a connecting channel (101) is further provided inside the first nozzle (1); a first end of the connecting channel (101) is connected to the powder feed pipe (51) or the air intake pipe (52); and a second end is connected to the powder feed end of the second powder delivery channel; the second nozzle (2) is connected to the first cavity; a second cavity is provided inside the second nozzle (2); the third nozzle (3) is connected to the second cavity, and a second powder delivery channel is formed between the inner wall of the second nozzle (2) and the outer wall of the third nozzle (3); the channel (301) for laser to pass through is provided inside the third nozzle (3).

3. The coaxial powder feeding head with variable powder spots according to claim 2, characterized in that: The size of the first cavity at the first end of the first nozzle (1) is larger than that at the second end; the second nozzle (2) is assembled into the first cavity from the first end of the first nozzle (1); the size of the second cavity at the first end of the second nozzle is larger than that at the second end; the third nozzle (3) is assembled into the second cavity from the first end of the second nozzle (2) and is connected to the first nozzle (1); the third nozzle (3) has a portion that is higher than the end surface of the first end of the first nozzle (1).

4. The coaxial powder feeding head with variable powder spots according to claim 2, characterized in that: The powder feeding component (5) is constructed in an annular shape and is connected to the outer wall of the third nozzle (3), and can be driven relative to the third nozzle (3) along its axis. When the powder feeding component (5) is driven around the axis of the third nozzle (3) by a predetermined angle, the first position and the second position are switched to each other.

5. The coaxial powder feeding head with variable powder spots according to claim 4, characterized in that: The outer wall of the third nozzle (3) is provided with a threaded connection structure (32), and a pressure plate (6) is provided on the threaded connection structure (32). When the pressure plate (6) is tightened on the threaded connection structure (32), the powder feeding component (5) can be pressed to keep the powder feeding component (5) in the first position or the second position.

6. The coaxial powder feeding head with variable powder spots according to any one of claims 2 to 5, characterized in that: The first end of the connecting channel (101) is connected to the upper end surface of the first nozzle (1), the first end of the first powder feeding channel (11) is connected to the upper end surface of the first nozzle (1), and the powder feeding end of the connecting channel (101) and the powder feeding end corresponding to the first powder feeding channel (11) are centrally symmetrically distributed.

7. The coaxial powder feeding head with variable powder spots according to claim 6, characterized in that: A gasket (4) is provided between the powder feeding component (5) and the first nozzle (1), and a plurality of through holes are provided on the gasket (4), wherein the through holes are distributed corresponding to the connecting channel (101) and the first powder feeding channel (11).

8. The coaxial powder feeding head with variable powder spots according to claim 2, characterized in that: The first powder delivery channel (11) extends from a first end surface of the first nozzle (1) to a second end surface, and the first powder delivery channel (11) is constructed to include a plurality of independent tubular channels distributed in an axisymmetric manner.

9. The coaxial powder feeding head with variable powder spots according to claim 8, characterized in that: A powder delivery pipe is arranged in the tubular channel, and a step groove is arranged at the bottom of the tubular channel. The outer diameter of the step of the step groove is equal to the outer diameter of the powder delivery pipe.

10. The coaxial powder feeding head with variable powder spots according to claim 2 or 3, characterized in that: The inner wall surface of the second nozzle (2) comprises a first conical surface with a gradually decreasing inner diameter, and the outer wall surface of the third nozzle (3) comprises a second conical surface with a gradually decreasing inner diameter. An annular channel (202) with a diameter gradually decreasing from a first end to a second end is formed between the first conical surface and the second conical surface. An annular cavity (201) is provided above the annular channel (202), and the annular cavity (201) is connected to the connecting channel (101).

11. The coaxial powder feeding head with variable powder spots according to claim 3, characterized in that: The second end of the second nozzle (2) is provided with a first step (21), the first step (21) is connected to the inner wall of the first nozzle (1) and limits the second nozzle (2) from continuously moving toward the second end of the first nozzle (1), the third nozzle (3) is provided with a second step (31), the second step abuts against the first end surface of the second nozzle (2) and limits the second nozzle from moving toward the first end of the first nozzle (1), and the third nozzle (3) and the first nozzle (1) are connected by bolts.

12. The coaxial powder feeding head with variable powder spots according to claim 2 or 3, characterized in that: A water cooling chamber (102) is provided between the second nozzle (2) and the first nozzle (1), and a water inlet hole and a water outlet hole are provided on the outer wall of the first nozzle (1), and the water inlet hole and the water outlet hole are in communication with the water cooling chamber (102).

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