An ultrasonic vibration type micro powder feeding nozzle for 3D printing

Abstract

The present invention provides an ultrasonic vibration type micro powder feeding nozzle for 3D printing. The nozzle includes a special bolt, a rear cover plate, a piezoelectric ceramic, a front cover plate, a conical horn and a needle head. The piezoelectric ceramic is arranged between the rear cover plate and the front cover plate. The special bolt is threadedly connected to the front cover plate, so that the rear cover plate and the piezoelectric ceramic are clamped in the middle to form a sandwich type ultrasonic transducer. A curved hopper is arranged in the needle head. The outflow of the powder is controlled by ultrasonic vibration. The amplitude of the ultrasonic vibration is small, which reduces the influence when the nozzle needle tube inserts into the B powder layer and is beneficial to improving the precision of the part. The flow and stop of the S powder are controlled by using the mechanism of ultrasonic vibration to break the powder arching in the curved hopper. The principle is simple and the operation is convenient, which is beneficial to cost saving. Moreover, the curved hopper with a hyperbolic generatrix has the characteristic of a constant shrinkage rate. When the powder flows in the hopper, the flow rate is stable, which is beneficial to improving the uniformity of the S powder isolation line and further improving the precision of the formed part.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder discharging equipment, and particularly relates to an ultrasonic vibration type micro powder feeding nozzle for 3D printing. Background Art

[0002] In the field of 3D printing, powder materials are raw materials for selective laser sintering forming technology, binder jetting forming technology, etc. In order to improve the density and surface quality of finished parts, etc., the particle size of the powder is usually in the range of 1 to 100 μm, which results in poor fluidity of the powder. A novel 3D printing technology involved in the present invention, selective separation forming, is an additive manufacturing technology using two kinds of powders, and these two kinds of powders need to be sintered after printing all layers. In the selective separation forming technology, the base powder (B powder) is spread layer by layer in the forming cylinder by a powder spreading roller, and the separation powder (S powder) is selectively deposited into each layer of the base powder (B powder) by using a powder nozzle. Compared with the B powder, the S powder obviously has different feeding conditions, which define the boundary of the cross-section of each layer of the part. Generally speaking, the S powder has a higher sintering temperature than the B powder. Therefore, at a specific sintering temperature, the B powder is sintered into shape while the S powder remains loose. After sintering, the part formed by sintering the B powder can be separated from the S powder and the solid waste of the B powder sintered around. In the selective separation forming printing technology, to improve the surface quality and forming accuracy of the part, it is required that the S powder feeding device has sufficient sensitivity, reliability, and tries to eliminate the problem of uneven powder discharging of the S powder caused by poor powder fluidity.

[0003] Currently, the common powder feeding method of the micro powder feeding nozzle is pneumatic powder feeding. Patent CN202020186136.7 introduces a pneumatic powder printing nozzle. This method controls the speed and flow rate of powder spraying through compressed gas, and controls the closing and opening of the spray holes by controlling the rotation of the built-in valve body, thereby controlling the outflow and stop of the powder. The selective separation forming technology mentioned in this article requires inserting the S powder nozzle into the B powder. Therefore, the pneumatic nozzle may blow away the already deposited B powder, which may lead to the problem of low precision of the formed part; because the required outlet diameter range of the nozzle is 0.26 mm to 1 mm, the small outlet diameter causes the compressed gas to be unable to blow away the powder blockage formed at the outlet.

[0004] Since the powder particle size range required by the selective separation forming technology is 50 μm to 100 μm, and it is required that the S powder separation line be as thin as possible, that is, the nozzle outlet be thin, the powder is extremely easy to form blockage at the nozzle outlet. Therefore, to improve the precision of the selective separation forming printed part, it is necessary to solve the problem of accurately controlling the outflow and stop of the powder. Summary of the Invention

[0005] The object of the present invention is to provide an ultrasonic vibration type micro powder feeding nozzle for 3D printing in view of the above deficiencies of the prior art.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] An ultrasonic vibration type micro powder feeding nozzle for 3D printing provided by the present invention includes a special bolt, a rear cover plate, a piezoelectric ceramic, a front cover plate, a conical horn and a needle. The piezoelectric ceramic is arranged between the rear cover plate and the front cover plate. The special bolt is threadedly connected to the front cover plate, so that the rear cover plate and the piezoelectric ceramic are clamped in the middle to form a sandwich type ultrasonic transducer. The large end of the conical horn is connected to the front cover plate, and the small end of the conical horn is connected to the needle. The special bolt includes a feeding nozzle, a first powder flow channel and a thread structure. The feeding nozzle is arranged at the top of the special bolt. The first powder flow channel is arranged inside the special bolt. The feeding nozzle is communicated with the first powder flow channel. The thread structure is arranged on the outer surface of the lower end of the special bolt. A second powder flow channel is arranged inside the front cover plate. A third powder flow channel is arranged inside the conical horn. The needle includes a fourth powder flow channel, a curved hopper and a needle tube. The curved hopper is arranged at the discharging end of the fourth powder flow channel. The needle tube is arranged at the discharging port of the curved hopper. The generatrix of the curved hopper is a hyperbola. The first powder flow channel, the second powder flow channel, the third powder flow channel, the fourth powder flow channel, the curved hopper and the needle tube are sequentially communicated. The powder enters from the feeding nozzle and forms a blockage when flowing to the curved hopper in the natural state. After the sandwich type ultrasonic transducer provides ultrasonic vibration, the blockage is broken, and the powder flows out from the needle tube.

[0008] Further, the equation of the hyperbola is as follows:

[0009]

[0010] Where D r is the orifice diameter of the curved hopper; C0 is the shrinkage rate of the curved hopper.

[0011] Further, the rear cover plate includes a rear cover plate body and a first cylindrical through hole arranged on the rear cover plate body. The first cylindrical through hole sleeves the special bolt.

[0012] Further, the piezoelectric ceramic includes four annular piezoelectric ceramic sheets. The four annular piezoelectric ceramic sheets are arranged in sequence from top to bottom. A plurality of rings form a second cylindrical through hole. The second cylindrical through hole is communicated with the first cylindrical through hole. The second cylindrical through hole sleeves the special bolt.

[0013] Further, the front cover plate includes a front cover plate body and a cup-shaped flange disposed at the upper end of the front cover plate body. The cup-shaped flange is provided with a connecting key and a threaded hole for fixing the nozzle and realizing rotation around the central axis of the nozzle. The front cover plate body includes a first cover plate and a second cover plate. The second cover plate is disposed below the first cover plate. The first cover plate is provided with a first internal threaded hole corresponding to the threaded structure. Both side portions of the first cover plate are provided with first flat positions. The second cover plate is provided with the second powder flow channel. The second powder flow channel is disposed below the first internal threaded hole and communicated with the first powder flow channel. The outer surface of the second cover plate is provided with a horn connecting thread for connecting the conical horn.

[0014] Further, the conical horn includes a horn body and a second internal threaded hole, a third powder flow channel and a third internal threaded hole disposed in the horn body. The second internal threaded hole is disposed at the top and corresponds to the horn connecting thread. The third powder flow channel is disposed below the second internal threaded hole and communicated with the second powder flow channel. The third internal threaded hole is disposed at the bottom and connected to the needle. Both side portions of the upper end of the horn body are provided with second flat positions.

[0015] Further, the needle further includes a needle body and a needle external thread disposed on the outer surface of the upper end of the needle body. The needle external thread corresponds to the third internal threaded hole. The needle body is provided with the fourth powder flow channel, the curved hopper and the needle tube.

[0016] Further, a notch is provided at the tail of the needle tube.

[0017] Further, the inner diameter of the needle tube is the same as the diameter of the discharge port of the curved hopper.

[0018]

[0019] The lower end is in the shape of an inverted fillet.

[0020] Compared with the prior art, the beneficial effects brought by the technical solution provided by the present invention are as follows:

[0021] (1) An ultrasonic vibration type micro powder feeding nozzle for 3D printing provided by the present invention includes a special bolt, a rear cover plate, a piezoelectric ceramic, a front cover plate, a conical horn and a needle. The piezoelectric ceramic is disposed between the rear cover plate and the front cover plate. The special bolt is threadedly connected to the front cover plate, so that the rear cover plate and the piezoelectric ceramic are clamped in the middle to form a sandwich type ultrasonic transducer. The powder outflow is controlled by ultrasonic vibration. The amplitude of the ultrasonic vibration is small, which reduces the influence when the nozzle needle tube inserts into the B powder layer and is beneficial to improving the precision of the part.

[0022] (2) The mechanism of using ultrasonic vibration to break the powder arching in the curved hopper is utilized to control the flow and stop of S powder. The principle is simple and the operation is convenient, which is beneficial to cost savings.

[0023] (3) The bus bar used in the present invention is a curved hopper with a hyperbolic shape, which has the characteristic of a constant shrinkage rate. Therefore, when the powder flows in this hopper, the flow rate is stable, which is beneficial to improving the uniformity of the S powder isolation line and further improving the accuracy of the formed parts.

[0024] (4) In the present invention, the length of the syringe needle is relatively short compared to the length of the entire nozzle, and the connection between the syringe needle and the needle head body is set as a chamfered corner, which is beneficial to reducing stress concentration and reducing the possibility of the syringe needle breaking under high-frequency vibration. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of an ultrasonic vibration type micro powder feeding nozzle for 3D printing according to the present invention;

[0026] Figure 2 is a sectional view of a special bolt of an ultrasonic vibration type micro powder feeding nozzle for 3D printing according to the present invention;

[0027] Figure 3 is a schematic structural diagram of the rear cover plate of an ultrasonic vibration type micro powder feeding nozzle for 3D printing according to the present invention;

[0028] Figure 4 is a schematic structural diagram of a piezoelectric ceramic of an ultrasonic vibration type micro powder feeding nozzle for 3D printing according to the present invention;

[0029] Figure 5 is a schematic structural diagram of the front cover plate of an ultrasonic vibration type micro powder feeding nozzle for 3D printing according to the present invention;

[0030] Figure 6 is a schematic structural diagram of a conical horn of an ultrasonic vibration type micro powder feeding nozzle for 3D printing according to the present invention;

[0031] Figure 7 is a schematic structural diagram of a needle head of an ultrasonic vibration type micro powder feeding nozzle for 3D printing according to the present invention;

[0032] Figure 8 is a mechanical diagram of the hopper wall when the S powder particles flow out through the curved hopper.

[0033] In the figure: 1. Special bolt; 11. Feed nozzle; 12. First powder flow channel; 13. Thread structure; 2. Rear cover plate; 21. First cylindrical through hole; 22. Rear cover plate body; 3. Piezoelectric ceramic; 31. Annular piezoelectric ceramic sheet; 32. Second cylindrical through hole; 4. Front cover plate; 41. Front cover plate body; 411. First cover plate; 412. Second cover plate; 42. Cup-shaped flange; 43. Connecting key; 44. Threaded hole; 45. First internal threaded hole; 46. Second powder flow channel; 47. First flat position; 48. Horn connecting thread; 5. Conical horn; 51. Horn body; 52. Second internal threaded hole; 53. Third powder flow channel; 54. Third internal threaded hole; 55. Second flat position; 6. Needle; 61. Needle body; 62. Fourth powder flow channel; 63. Curved hopper; 64. Syringe; 641. Notch; 65. External thread of needle. Detailed implementation manners

[0034] To make the objectives, technical solutions and advantages of the present invention clearer, the following will further describe the embodiments of the present invention with reference to the accompanying drawings. What is introduced below is a relatively optimal one among multiple possible embodiments of the present invention, aiming to provide a basic understanding of the present invention, but not aiming to identify the key or decisive elements of the present invention or limit the scope to be protected.

[0035] Please refer to Figure 1 and Figure 2, an embodiment of the present invention provides an ultrasonic vibration type micro powder feeding nozzle for 3D printing, which includes a special bolt 1, a rear cover plate 2, a piezoelectric ceramic 3, a front cover plate 4, a conical horn 5 and a needle 6. The piezoelectric ceramic 3 is arranged between the rear cover plate 2 and the front cover plate 4. The special bolt 1 is threadedly connected to the front cover plate 4, so that the rear cover plate 2 and the piezoelectric ceramic 3 are clamped in the middle to form a sandwich type ultrasonic transducer. The large end of the conical horn 5 is connected to the front cover plate 4, and the small end of the conical horn 5 is connected to the needle 6. The special bolt 1 includes a feeding nozzle 11, a first powder flow channel 12 and a thread structure 13. The feeding nozzle 11 is arranged at the top of the special bolt 1. The first powder flow channel 12 is arranged inside the special bolt 1. The feeding nozzle 11 is communicated with the first powder flow channel 12. The thread structure 13 is arranged on the outer surface of the lower end of the special bolt 1. A second powder flow channel 46 is arranged inside the front cover plate 4. A third powder flow channel 53 is arranged inside the conical horn 5. The needle 6 includes a fourth powder flow channel 62, a curved hopper 63 and a needle tube 64. The curved hopper 63 is arranged at the discharging end of the fourth powder flow channel 62. The needle tube 64 is arranged at the discharging port of the curved hopper 63; the generatrix of the curved hopper 63 is a hyperbola; the first powder flow channel 12, the second powder flow channel 46, the third powder flow channel 53, the fourth powder flow channel 62, the curved hopper 63 and the needle tube 64 are sequentially communicated. The powder enters from the feeding nozzle 11 and forms a blockage when flowing to the curved hopper 63 in the natural state. After the sandwich type ultrasonic transducer provides ultrasonic vibration, the blockage is broken, and the powder flows out from the needle tube 64. Using ultrasonic vibration to control the powder outflow, the amplitude of the ultrasonic vibration is small, which reduces the influence when the nozzle needle tube inserts into the B powder layer and is beneficial to improving the precision of the part; using ultrasonic vibration to break the mechanism of powder arching in the curved hopper to control the flow and stop of the S powder, the principle is simple and the operation is convenient, which is beneficial to cost saving; moreover, using a curved hopper with a hyperbola generatrix has the characteristic of a constant shrinkage rate, so the powder flow rate is stable when flowing in the hopper, which is beneficial to improving the uniformity of the S powder isolation line and further improving the precision of the formed part.

[0036] In some embodiments, the material of the special bolt 1 can be stainless steel. A thin-walled feeding nozzle 11 is designed at the upper end, and a first powder flow channel 12 is designed in the middle of the bolt, which is a through-hole structure. The diameter of the through-hole does not exceed half of the nominal diameter of the bolt. The external thread structure 13 of the special bolt is connected to the first internal thread 45 of the front cover plate to compress the sandwich structure of the front and rear cover plates 2 and the piezoelectric ceramic 3.

[0037] In some embodiments, in order to improve the uniformity of the S powder isolation line, the hyperbola should satisfy the following functional formula:

[0038]

[0039] where D ris the orifice diameter of the bending hopper, and specific values are designed according to actual requirements and experimental verification; C0 is the shrinkage rate of the bending hopper, and specific values are designed according to actual requirements and experimental verification.

[0040] In some embodiments, to ensure the function of the sandwich ultrasonic transducer, such as Figure 3 As shown, the rear cover plate 2 may include a rear cover plate body 22 and a first cylindrical through hole 21 provided on the rear cover plate body 22, and the first cylindrical through hole 21 sleeved with a special bolt 1. The rear cover plate 2 may be a cylindrical part with a middle through hole made of stainless steel.

[0041] In some embodiments, to better generate high-frequency vibrations, such as Figure 4 As shown, the piezoelectric ceramic 3 may include four annular piezoelectric ceramic sheets 31, and the four annular piezoelectric ceramic sheets 31 are arranged in sequence from top to bottom. A plurality of rings form a second cylindrical through hole 32, and the second cylindrical through hole 32 communicates with the first cylindrical through hole 21, and the second cylindrical through hole 32 sleeved with a special bolt 1.

[0042] In some embodiments, to compress the sandwich structure of the rear cover plate and the piezoelectric ceramic, such as Figure 5 As shown, the front cover plate 4 may include a front cover plate body 41 and a cup-shaped flange 42 provided at the upper end of the front cover plate body 41. The cup-shaped flange 42 is provided with a connecting key 43 and a threaded hole 44 for fixing the nozzle and realizing rotation around the central axis of the nozzle; the front cover plate body 41 includes a first cover plate 411 and a second cover plate 412, and the second cover plate 412 is arranged below the first cover plate 411. The first cover plate 411 is provided with a first internal threaded hole 45, and the first internal threaded hole 45 corresponds to the threaded structure 13. Both side portions of the first cover plate 411 are provided with a first flat position 47; the second cover plate 412 is provided with a second powder flow channel 46, and the second powder flow channel 46 is arranged below the first internal threaded hole 45 and communicates with the first powder flow channel 12. The outer surface of the second cover plate 412 is provided with a horn connecting thread 48 for connecting the conical horn 5. The front cover plate body 41 may be made of titanium alloy. The inner diameter of the cup-shaped flange 42 is larger than the outer diameter of the front cover plate body 41, and there is a connecting key 43 on the outer edge for connecting transmission structures such as gears. There is a threaded hole 44 at the bottom of the cup-shaped flange 42 for fixing the nozzle; the front cover plate body 41 is a cylinder with a middle through hole, and there is a section of the first internal threaded hole 45 in the through hole part for bolt connection with the threaded structure 13. There is a section of the horn connecting thread 48 extending from the lower end of the front cover plate body 41 for connecting the conical horn 5.

[0043] In some embodiments, to ensure that the S powder smoothly enters the bending hopper without clogging, such as Figure 6As shown, the conical horn 5 may include a horn body 51, a second internal threaded hole 52, a third powder flow channel 53, and a third internal threaded hole 54 provided inside the horn body 51. The second internal threaded hole 52 is provided at the top and corresponds to the horn connection thread 48. Below the second internal threaded hole 52 is provided the third powder flow channel 53, and the third powder flow channel 53 communicates with the second powder flow channel 46. The third internal threaded hole 54 is provided at the bottom and is connected to the needle 6. On both side parts of the upper end of the horn body 51 are provided second flat positions 55. The material of the conical horn 5 may be titanium alloy.

[0044] In some embodiments, in order to cause stable arching blockage of the S powder, as Figure 7 shown, the needle 6 further includes a needle body 61 and a needle external thread 65 provided on the outer surface of the upper end of the needle body 61, and the needle external thread 65 corresponds to the third internal threaded hole 54; inside the needle body 61 are provided a fourth powder flow channel 62, a curved hopper 63, and a needle tube 64.

[0045] In some embodiments, in order to, a notch 641 may be provided at the tail of the needle tube 64. The notch 641 may be square.

[0046] In some embodiments, in order to, the inner diameter of the needle tube 64 is the same as the outlet diameter of the curved hopper 63.

[0047] In some embodiments, in order to reduce the risk of the needle tube breaking under high-frequency vibration, the length of the needle tube 64 is The lower end of the needle body 61 is in a rounded corner shape. The connection between the needle tube and the needle body is set in a rounded corner shape.

[0048] In addition to providing vibration, the sandwich-type ultrasonic transducer provided by the present invention has connection keys 43 and threaded holes 44 designed on its cup-shaped flange 42 for the overall fixation of the nozzle and to achieve the function of rotating around the Z axis; its bolt feed nozzle 11 can fix the feed hose, and then continuously supply powder through the middle powder flow channel.

[0049] The function of the conical horn 5 is to connect the sandwich-type ultrasonic transducer and the needle; the middle cylindrical through-hole, i.e., the third powder flow channel 53, can ensure that the S powder smoothly enters the curved hopper without blockage; the conical horn 5 can concentrate the vibration energy of the ultrasonic transducer at the needle.

[0050] The cylindrical flow channel of the needle 6, i.e., the fourth powder flow channel 62, is used for continuous powder supply without clogging; the curved hopper 63 inside the needle 6 is used to cause stable arching and clogging of the S powder, and applying ultrasonic vibration can break the clogging. The outlet diameter of the curved hopper 63 is related to the diameter of the S powder particles, the friction coefficient between the powder and the hopper wall, the bulk density of the powder, the acceleration due to gravity, and the shrinkage rate of the hopper, and is limited by the width of the separation line in the B powder; the shrinkage rate is limited by the overall size of the needle.

[0051] It should be noted that the orifice diameter D of the lower end outlet of the powder curved hopper 63 of the present invention r needs to be less than the critical orifice size D m . The orifice diameter D r is the inner diameter of the outlet of the curved hopper 63, and the meaning of the critical orifice size D m is the maximum outlet diameter at which the powder can form a clog at the outlet of the curved hopper. Therefore, when designing the curved hopper, it is necessary to satisfy D r < D m . The maximum value of this orifice diameter is limited by the conditions for forming a stable arch and the conditions of the separation line width, and the minimum value is limited by the conditions for whether applying ultrasonic vibration can break the arch and allow the powder to flow out smoothly and the conditions of the existing processing technology. The specific range of the outlet diameter is obtained through calculation and experiments.

[0052] As Figure 8 shown, the determination formula for the outlet diameter D r of the curved hopper 63 is as follows:

[0053]

[0054] where ε, a, b, and c are constant coefficients; C is the shrinkage rate of the curved hopper; σ c is the critical base stress, which belongs to the characteristics of the powder; ρ b is the bulk density of the powder; K m is the ratio of the critical orifice diameter D m to the particle diameter k, and the formula is as follows:

[0055] D m = K m k

[0056] The critical orifice diameter D m calculated by the above formula, its meaning is that if the outlet diameter D r of the curved hopper is greater than this critical orifice diameter, then the hopper will definitely not form arching and clogging. Since the mechanism of the present invention needs to utilize the stable arching of the curved hopper to stop the powder flow, it is necessary to determine the range of the outlet diameter at which different-sized particles can form a stable arch.

[0057] The material of the annular piezoelectric ceramic sheet is PZT-8. Its outer diameter is equal to that of the front cover plate, and its inner diameter needs to be slightly larger than the major diameter of the bolt to avoid contact leakage. The polarization direction is along the thickness direction. Copper electrode sheets are sandwiched between the piezoelectric ceramic sheets and between the piezoelectric ceramic sheet and the front cover plate, and their positive and negative electrodes are respectively connected to the ultrasonic power supply. The ultrasonic power supply can apply excitation pulses with different powers and frequencies to the transducer.

[0058] Connect four annular piezoelectric ceramics to the ultrasonic power supply. The operating frequency of the piezoelectric ceramics is 20 kHz to 50 kHz, and the electrode polarization direction is the same as the powder flow path direction. In this direction, the annular piezoelectric ceramic sheet generates high-frequency vibration under a pulsed voltage of 20 kHz to 50 kHz. Thus, by controlling the vibration and stop of the piezoelectric ceramic sheet through the pulsed voltage signal, the feeding and blocking of the powder can be achieved.

[0059] The cup-shaped flange 42 is connected to a bearing that can rotate the ultrasonic nozzle around the central axis. At the same time, the ultrasonic nozzle can move along the X, Y, and Z axes. Since the needle tube 64 part of the nozzle needs to be inserted into the B powder layer for the transportation of S powder, and powder needs to be fed for each powder layer, the height of the square notch 641 at the tail of the needle tube needs to be equal to the thickness of each layer of powder laid by the selective separation and forming printer. After the ultrasonic nozzle is inserted into the B powder layer, it moves in the opposite direction of the square notch 641. At this time, ultrasonic vibration is applied, and the S powder can smoothly flow out from the square notch 641 of the needle tube. The S powder is fed through a hose connected to the feeding nozzle 11 at the head of the special bolt 1. Experiments on this example show that using the method of ultrasonic vibration to control the feeding and blocking of powder has high precision.

[0060] Compared with the traditional conical hopper, the advantage of the curved hopper is that the shape of its hopper wall can ensure the continuity of the powder during the outflow process. The following explains this phenomenon using the force situation of a single particle. The force exerted on the S powder particle by the hopper wall during the outflow process is as Figure 8 shown. The calculation formula for its normal force is as follows:

[0061] F n =-Gcosa

[0062] In the formula, F n is the normal force; G is the gravity; α is the angle between the tangential force (F r ) and the horizontal direction. As the powder flows towards the outlet, α continuously increases, and then the normal force F n constantly decreases. Since a large normal force will compress the powder and cause an arch to form, blocking the hopper outlet, using an S powder nozzle with a curved hopper design can ensure the continuity of the powder during the powder outflow process, which is beneficial to improving the forming accuracy of the part boundary. For a conical hopper, the α angle remains constant, so the normal force on the particle remains unchanged, and the S powder is more likely to be blocked closer to the outlet.

[0063] In summary, in the case where ultrasonic vibration continuously breaks the arch, the curved hopper improves the separation of B powder sintered parts due to having a more continuous powder flow, and improves the forming accuracy of the parts.

[0064] In the case of no conflict, the above-mentioned embodiments and the features in the embodiments in this article may be combined with each other.

[0065] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An ultrasonic vibration type micro powder feeding nozzle for 3D printing, characterized in that, It includes a special bolt (1), a rear cover plate (2), a piezoelectric ceramic (3), a front cover plate (4), a conical horn (5) and a needle head (6). The piezoelectric ceramic (3) is arranged between the rear cover plate (2) and the front cover plate (4). The special bolt (1) is threadedly connected to the front cover plate (4), so that the rear cover plate (2) and the piezoelectric ceramic (3) are sandwiched in the middle to form a sandwich-type ultrasonic transducer. The large end of the conical horn (5) is connected to the front cover plate (4), and the small end of the conical horn (5) is connected to the needle head (6). The special bolt (1) includes a feed nozzle (11), a first powder flow channel (12) and a thread structure (13). The feed nozzle (11) is arranged at the top of the special bolt (1). The first powder flow channel (12) is arranged inside the special bolt (1). The feed nozzle (11) is communicated with the first powder flow channel (12). The thread structure (13) is arranged on the outer surface of the lower end of the special bolt (1). The front cover plate (4) is provided with a second powder flow channel (46) inside. The conical horn (5) is provided with a third powder flow channel (53) inside. The needle head (6) includes a fourth powder flow channel (62), a curved hopper (63) and a needle tube (64). The curved hopper (63) is arranged at the discharging end of the fourth powder flow channel (62). The needle tube (64) is arranged at the discharging port of the curved hopper (63). The generatrix of the curved hopper (63) is a hyperbola. The first powder flow channel (12), the second powder flow channel (46), the third powder flow channel (53), the fourth powder flow channel (62), the curved hopper (63) and the needle tube (64) are sequentially communicated. The powder enters from the feed nozzle (11) and flows to the curved hopper (63) in the natural state to form a blockage. After the sandwich-type ultrasonic transducer provides ultrasonic vibration, the blockage is destroyed, and the powder flows out from the needle tube (64). The orifice diameter of the lower end outlet of the curved hopper (63) needs to be smaller than the critical orifice diameter ; The equation of the hyperbola is as follows: ， Among them is the orifice diameter of the bending hopper; is the shrinkage rate of the bending hopper; The calculation formula is as follows: Among them, , , , are constant coefficients, is the shrinkage rate of the curved hopper; is the critical pedestal stress, which belongs to the characteristics of the powder; is the bulk density of the powder; is the critical orifice diameter and the particle diameter The ratio is as follows: 。 2. The ultrasonic vibration type micro powder feeding nozzle for 3D printing according to claim 1, characterized in that, The rear cover plate (2) includes a rear cover plate body (22) and a first cylindrical through hole (21) provided on the rear cover plate body (22), and the first cylindrical through hole (21) sleeves the special bolt (1).

3. The ultrasonic vibration type micro powder feeding nozzle for 3D printing according to claim 2, wherein, The piezoelectric ceramic (3) includes four annular piezoelectric ceramic sheets (31), and the four annular piezoelectric ceramic sheets (31) are arranged in sequence from top to bottom. A plurality of rings form a second cylindrical through hole (32), and the second cylindrical through hole (32) communicates with the first cylindrical through hole (21), and the second cylindrical through hole (32) sleeves the special bolt (1).

4. The ultrasonic vibration type micro powder feeding nozzle for 3D printing according to claim 3, characterized in that, The front cover plate (4) includes a front cover plate body (41) and a cup-shaped flange (42) provided at the upper end of the front cover plate body (41). A connection key (43) and a threaded hole (44) are provided on the cup-shaped flange (42) for fixing the nozzle and realizing rotation around the central axis of the nozzle; the front cover plate body (41) includes a first cover plate (411) and a second cover plate (412), the second cover plate (412) is arranged below the first cover plate (411), a first internal threaded hole (45) is provided in the first cover plate (411), and the first internal threaded hole (45) corresponds to the threaded structure (13). First flat positions (47) are provided on both sides of the first cover plate (411); a second powder flow channel (46) is provided in the second cover plate (412), the second powder flow channel (46) is arranged below the first internal threaded hole (45) and communicates with the first powder flow channel (12), and a horn connecting thread (48) is provided on the outer surface of the second cover plate (412) for connecting the conical horn (5).

5. The ultrasonic vibration type micro powder feeding nozzle for 3D printing according to claim 4, characterized in that, The conical horn (5) includes a horn body (51) and a second internal threaded hole (52), a third powder flow channel (53) and a third internal threaded hole (54) provided in the horn body (51). The second internal threaded hole (52) is provided at the top and corresponds to the horn connecting thread (48). The third powder flow channel (53) is provided below the second internal threaded hole (52), and the third powder flow channel (53) communicates with the second powder flow channel (46). The third internal threaded hole (54) is provided at the bottom and is connected to the needle head (6). Second flat positions (55) are provided on both sides of the upper end of the horn body (51).

6. The ultrasonic vibration type micro powder feeding nozzle for 3D printing according to claim 5, characterized in that, The needle head (6) further includes a needle head body (61) and a needle head external thread (65) provided on the outer surface of the upper end of the needle head body (61), and the needle head external thread (65) corresponds to the third internal threaded hole (54); a fourth powder flow channel (62), a curved hopper (63) and a needle tube (64) are provided in the needle head body (61).

7. The ultrasonic vibration type micro powder feeding nozzle for 3D printing according to claim 6, characterized in that, A notch (641) is provided at the tail of the needle tube (64).

8. The ultrasonic vibration type micro powder feeding nozzle for 3D printing according to claim 7, characterized in that, The inner diameter of the needle tube (64) is the same as the outlet diameter of the curved hopper (63).

9. The ultrasonic vibration type micro powder feeding nozzle for 3D printing according to claim 8, characterized in that, The length of the needle tube (64) is 1 / 7 to 1 / 8 of the length of the needle head body (61).

10. The ultrasonic vibration type micro powder feeding nozzle for 3D printing according to claim 8, characterized in that, The lower end of the needle body (61) is in the shape of a rounded corner facing downwards.

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