CN112893878A - Gradient material powder mixing device and method thereof - Google Patents
Gradient material powder mixing device and method thereof Download PDFInfo
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- CN112893878A CN112893878A CN202110063292.3A CN202110063292A CN112893878A CN 112893878 A CN112893878 A CN 112893878A CN 202110063292 A CN202110063292 A CN 202110063292A CN 112893878 A CN112893878 A CN 112893878A
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- 238000002156 mixing Methods 0.000 title claims abstract description 307
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- B22F1/0003—
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
- B33Y40/10—Pre-treatment
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/25—Process efficiency
Abstract
A gradient material powder mixing device and method, its apparatus includes mixing the powder unit mainly, its entrance is a large opening, the exit is a small opening, can realize the mixed effect of three kinds of near synchronous powder discharge impact mixing, bottom of double funnels in the main powder unit of mixing, bottom air current impact mixing sequentially; the powder supply and near-synchronous powder discharge impact mixing unit is arranged on the large opening side of the main powder mixing unit and comprises a powder supply cavity with a powder supply space, a powder supply shaft for controlling the powder in the powder supply cavity to be discharged into the main powder mixing unit, an inclined powder collecting plate and a vertical plate; and the uniformly-distributed mixing unit comprises two dispersing cavities and a powder collecting cavity which is clamped between the two dispersing cavities and communicated with the two dispersing cavities, and the powder can be dispersed, mixed and redispersed through the radial flow channels on the dispersing cavities and the collecting cavity arranged in an inverted trapezoid, so that the powder is further mixed and uniformly distributed to be in a proper width. Compared with the prior art, the invention can shorten the mixing time and improve the mixing effect.
Description
Technical Field
The invention relates to the technical field of gradient materials, in particular to a gradient material powder mixing device and a method thereof.
Background
In the prior art, metal parts are produced by a 3D printing method, such as a laser cladding manufacturing method, a selective laser melting method, and an electron beam melting deposition method, and these techniques are currently applied to the fields of aerospace, medical parts, automobile manufacturing, and the like. However, these techniques are currently used for the formation of a single metal material. With the continuous maturation of technology, 3D printing using only a single metal material has not been satisfied. The 3D printing technology of multi-material metal parts including gradient material parts is increasingly gaining attention.
The gradient material part is a novel composite material part which is continuously changed in composition or structure along the thickness or diameter direction by different materials. Different materials or structures are arranged on different positions of the gradient material part, so that different parts of the part have different properties or functions. And the material components or structural features in the parts are in continuous transition, so that different materials or structures are well combined, and the parts cannot be damaged due to performance mismatch under severe use conditions. Therefore, the gradient material part has great application potential in industry and daily life. At present, most of the forming methods of gradient material parts are to obtain a thin gradient material layer on the surface of a base part by methods such as spraying or vapor deposition, and the process is complex and the efficiency is low. Compared with the traditional part manufacturing method, the 3D printing (also called additive manufacturing) has the advantages of high automation degree, easiness in realizing complex structure forming, high forming efficiency and the like, and after the 3D printing technology comes out, the 3D printing process capable of realizing the manufacturing of the gradient material parts gradually appears.
A3D printing process of Selective Laser Melting (SLM) is one of the current 3D printing processes of metal parts with the highest printing precision, and powder needs to be paved layer by adopting a scraper blade or a roller shaft during forming, namely, powder with one layer of thickness can be paved every time. The process technology is generally used for the forming of single material parts, limited by the principle that one layer of powder needs to be laid each time, and in order to realize the SLM forming of the gradient material, materials with required components need to be laid in a selected area through a scraper blade or a roller shaft before the selective laser melting is carried out. For this purpose, the following two methods are often used to obtain powder materials of different compositions: one is a pre-blending method, which is to load pre-mixed powder into different funnels according to the material components of each part, and which gradient component is required in the molding process, corresponding gradient component powder is discharged from the corresponding funnel, but for gradient material parts, a plurality of gradient component areas may be present, so that a plurality of funnels are required correspondingly, and the construction cost and the volume of the equipment are increased; the other method is a real-time blending method, which mixes a plurality of different powders in real time according to the proportion, and the method only needs to arrange a funnel for containing the original powder according to the component types of the basic composition materials and blend the powders in time according to the proportion during molding, does not need to arrange different funnels according to the proportion, and has the advantages of reducing the volume of molding equipment and obtaining various different gradient material components.
Although the real-time blending method has certain advantages over the pre-blending method, certain disadvantages still exist, including the following aspects:
(1) the powder needs to be mixed in real time in the forming process, so that the assembly time can be prolonged, and the traditional mechanical turnover type powder mixing device, such as a V-shaped mixer and a double-cone type mixer, generally needs more than 5 minutes for powder mixing time, and for 3D printing of gradient material parts, due to the fact that different powder materials are used, an independent real-time powder mixing process is needed before different types of powder materials are paved at each time, the 3D printing efficiency is inevitably greatly reduced, and the advantages compared with other technologies are lost.
(2) Because protective gas must be introduced to prevent the material from being oxidized in the forming process when the metal material SLM is formed, the real-time powder mixing process needs to be carried out in the protective gas, and meanwhile, the powder mixing process cannot directly spray the powder which is not mixed onto the forming platform. However, the device for mixing powder in real time also needs to be integrated with the SLM forming chamber and the hoppers and communicated with each other, and a traditional turnover type powder mixing device, such as a V-shaped mixer, is difficult to achieve without powder scattering in the turnover mixing process because the turning radius is large and powder discharged from the two hoppers in proportion needs to be connected before powder mixing, and is also difficult to integrate the powder mixing device into SLM equipment.
(3) Because different materials are involved in the SLM forming process of the gradient material part, and the different materials may enter the powder mixing device in different amounts at a certain forming moment, after a certain material area is formed, residual powder in the powder mixing device must be cleaned, and the problem cannot be well solved by the conventional powder mixing device.
(4) Also there are some powder air current mixed's device to appear at present, nevertheless do not print real-time whitewashed demand of mixing to 3D, and only can mix the powder through the air current, still can not well satisfy 3D in the aspect of mixing powder efficiency and print the demand, also can not adapt to the demand that mixes the powder device and need link into an organic whole design with the shaping room.
Disclosure of Invention
Based on this, the invention aims to provide a gradient material powder mixing device capable of quickly and uniformly mixing powder.
The gradient material powder mixing device is realized by the following scheme:
the longitudinal section of the main powder mixing unit is an inverted trapezoid with openings at two ends, and the inlet of the main powder mixing unit is a large opening while the outlet of the main powder mixing unit is a small opening; the powder supply and near-synchronous powder discharge impact mixing unit is arranged on the large opening side of the main powder mixing unit; the powder supply and near-synchronous powder discharge impact mixing unit comprises a powder supply cavity provided with two powder supply spaces and a powder supply shaft arranged between the powder supply cavity and the main powder mixing unit to control the powder in the powder supply cavity to be discharged into the main powder mixing unit; the uniformly distributed mixing unit comprises two dispersing cavities and a powder collecting cavity which is clamped between the two dispersing cavities and communicated with the two dispersing cavities; the longitudinal sections of the dispersing cavity and the powder collecting cavity are inverted trapezoids with openings at two ends, and the small opening side of one dispersing cavity is communicated with the small opening side of the main powder mixing unit; more than two sub-channels radiating from the small opening to the large opening are arranged in the dispersion cavity; along the powder leakage direction, the cross sectional area of the dispersion cavity is gradually increased, and the cross sectional area of the powder collection cavity is gradually decreased.
Compared with the prior art, the gradient material powder mixing device disclosed by the invention can be used for mixing the powder in the process of naturally leaking the powder to the forming chamber under the action of gravity, so that the time for mixing the powder is shortened, the forming efficiency is improved, the mixing is repeated for multiple times, and the effect of fully mixing the powder is greatly improved.
Furthermore, the powder supply and near-synchronous powder discharge impact mixing unit also comprises a first oblique powder collecting plate, a second oblique powder collecting plate and a vertical plate; the first oblique powder collecting plate and the second oblique powder collecting plate are respectively oppositely arranged between the powder supply shaft and the main powder mixing unit and are inclined towards the main powder mixing unit; a gap is reserved between the first oblique powder collecting plate and the second oblique powder collecting plate; the vertical plate is arranged between the two powder supply cavities of the powder supply and near-synchronous powder discharge impact mixing unit and below the powder supply shaft and extends out of the main powder mixing unit, and two sides of the lower part of the vertical plate are chamfered so that two chamfered surfaces are respectively parallel to the first oblique powder collecting plate and the second oblique powder collecting plate to form two powder conveying channels; the powder discharged from the corresponding powder supply cavity is collected to the corresponding powder conveying channel by the V-shaped groove formed by the first oblique powder collecting plate and the vertical plate, the powder discharged from the corresponding powder supply cavity is collected to the corresponding other powder conveying channel by the other V-shaped groove formed by the second oblique powder collecting plate and the vertical plate, and the two powder flow beams are mixed in a gap formed by the first oblique powder collecting plate and the second oblique powder collecting plate. Through setting up two defeated powder passageways that the vertical plate obtained, can effectively prevent that two kinds of powders from because of the too big powder that causes of factors such as density difference, supply quantity difference in clearance department flow difference.
Further, the device also comprises a gas mixing unit; the gas mixing unit comprises a gas pump, a gas inlet pipe and a gas outlet pipe; the air inlet pipe is connected with an air outlet of the air pump; the air outlet pipe is connected with an air inlet of the air pump; the air pump is positioned outside the main powder mixing unit and is communicated with the side wall of the main powder mixing unit through the air inlet pipe and the air outlet pipe; the communicating port of the air inlet pipe is arranged at one side close to the uniformly distributed mixing units; and the communicating port of the air outlet pipe is arranged at one side close to the powder supply and near synchronous powder discharge impact mixing unit. The gas mixing can further improve the mixing effect.
Further, the main powder mixing unit also comprises an electric control valve; the electric control valve is arranged near the outlet of the main powder mixing unit. The electric control valve can ensure the mixing time and ensure the mixing to be more sufficient.
Further, the main powder mixing unit is provided with a powder gathering part; the powder converging part is a channel which is arranged at the small opening side of the main powder mixing unit and communicated with the uniformly distributed mixing units; the electric control valve is arranged at the outlet of the powder converging part close to the main powder mixing unit. The powder is converged and remixed by arranging the powder converging part, so that the mixing effect is improved.
Further, the ultrasonic vibration block is also included; the ultrasonic vibration block is arranged on the outer side wall of the main powder mixing unit. The ultrasonic vibration is beneficial to preventing powder particles from being adhered to the inner walls of all parts in the device and ensuring that the powder discharged from the funnel can be completely discharged out of the device.
Further, the device also comprises a control unit; the powder supply and near-synchronous powder discharge impact mixing unit also comprises a powder supply motor, and the powder supply motor drives the powder supply shaft to rotate; the control unit is respectively electrically connected with the powder supply motor, the electric control valve, the air pump and the ultrasonic vibration block and controls the switch of the ultrasonic vibration block. The control unit is arranged to implement an automated operation.
In addition, the invention also provides a gradient material powder mixing method, which comprises the following steps:
(1) near-synchronous powder discharging impact mixing, wherein when the near-synchronous powder discharging impact mixing is carried out, two beams of powder flow impact and mix with each other;
(2) bottom convergence-airflow impact multiple-cycle mixing: the mixed powder flow obtained in the step (1) is discharged and converged in a space with the gradually reduced cross section area, so that bottom convergence and mixing are realized; the mixed powder is converged at the bottom and is thrown upwards under the action of airflow, and powder particles are collided and mixed with each other in space to realize airflow impact mixing; the powder is subjected to bottom convergence and mixing again in the falling process; the above steps are repeated, so that bottom convergence and airflow impact are circularly mixed for multiple times;
(3) uniformly distributing and mixing, wherein when uniformly distributing and mixing are carried out, powder materials are dispersed and uniformly distributed through a radial flow passage, powder mixing is realized through a cavity arranged in an inverted trapezoid, and the powder is further mixed and uniformly distributed to be in a proper width according to more than one flow of dispersing, uniformly distributing, collecting and dispersing and uniformly distributing.
Compared with the prior art, the gradient material powder mixing method provided by the invention combines airflow impact to realize multiple times of mixing in the process that the powder naturally falls under the action of gravity, and improves the mixing efficiency and the mixing effect.
Further, the gas flow in the gas flow impact mixing step is from the gas in the forming chamber of the selective laser melting additive manufacturing equipment, and external air is not introduced.
For a better understanding and practice, the invention is described in detail below with reference to the accompanying drawings.
Drawings
FIG. 1 is a schematic view of the overall structure of a longitudinal section of a gradient material powder mixing apparatus according to the present invention;
FIG. 2 is a schematic structural diagram of a powder supply and near-synchronous powder discharge impact mixing unit according to the present invention;
FIG. 3 is a schematic structural diagram of a powder mixing unit according to the present invention;
FIG. 4 is a schematic three-dimensional structure of the main powder mixing unit according to the present invention;
FIG. 5 is a schematic structural view of a longitudinal section of a uniformly distributed mixing unit according to the present invention;
FIG. 6 is a flow chart of a gradient material powder mixing method according to the present invention;
FIG. 7 is a schematic diagram of a material structure of one layer in a gradient material part structure according to an embodiment of the present invention.
Detailed Description
The gradient material powder mixing device realizes the mixing of four steps of near-synchronous powder discharging impact mixing, bottom convergence mixing, airflow impact mixing and uniform powder discharging and mixing of the double funnels. Except for the air flow impact mixing, the other steps occur in the gravity flowing process of the powder, so that the assembly time is not additionally increased, and the powder materials can be quickly and uniformly mixed.
Referring to fig. 1, the gradient material powder mixing apparatus of the present invention includes a powder supply and near-synchronous powder discharge impact mixing unit 10, a main powder mixing unit 20, a gas mixing unit 30, an even distribution mixing unit 40, and control units (not shown) electrically connected to the mixing units respectively. Supply powder and nearly synchronous powder impact mixing unit 10 setting to be in the top of main powder unit 20 that mixes, gas mixing unit 30 with main powder unit 20 intercommunication that mixes, equipartition mixing unit 40 sets up the bottom of main powder unit 20 that mixes and be connected with the shaping room (not shown) that 3D printed. Under the control of the control unit, the powder material is subjected to near-synchronous powder discharging impact mixing in the powder discharging process of the powder supplying and near-synchronous powder discharging impact mixing unit 10, bottom convergence mixing is performed in the main powder mixing unit 20, meanwhile, the gas mixing unit 30 is subjected to gas flow impact mixing, the execution time of the gas flow mixing unit 30 is set, and the gas flow impact mixing-bottom convergence mixing can be alternately and repeatedly performed. After the execution time of the air flow mixing unit 30 is reached, the powder material is discharged and uniformly mixed in the uniform distribution mixing unit 40, discharged out of the gradient material powder mixing device and enters the forming chamber for powder laying so as to prepare for selective laser melting forming.
Referring to fig. 2, the powder supply and near-synchronous powder discharge impact mixing unit 10 includes a powder supply chamber 110, a powder supply motor 120, a powder supply shaft 130, a first inclined powder collecting plate 140, a second inclined powder collecting plate 150, and a vertical plate 160. The powder supply chamber 110 is provided with a partition 113 to divide the chamber into a first powder supply space 111 and a second powder supply space 112 for receiving powder materials of different compositions, and the powder materials are received from an inlet of the powder supply space and discharged from an outlet near one side of the main powder mixing unit 20. The powder supply motor 120 is fixed on the sidewall of the powder supply chamber 110 and electrically connected to the control unit, and the control unit controls the on/off of the control unit. The powder supplying shaft 130 is erected at the outlet of each powder supplying space, the first powder supplying space 111 is provided with a first powder supplying shaft 131 and is controlled to rotate by a first powder supplying motor 121, the second powder supplying space 112 is provided with a second powder supplying shaft 132 and is controlled to rotate by a second powder supplying motor 122, each powder supplying shaft is provided with more than 1 groove for loading powder leaked from the powder supplying space, the control unit controls the two powder supplying shafts to be started simultaneously and can rotate at different speeds, the powder leakage with a certain volume ratio is completed in the same time, and then the powder in the two powder supplying spaces is close to and synchronously leaked.
When the groove of the powder supplying shaft 130 faces the powder supplying cavity 110 during the rotation of the powder supplying shaft 130, powder falls into the groove of the powder supplying shaft 130; when the groove of the powder supplying shaft 130 faces the main powder mixing unit 20, the powder falls from the groove of the powder supplying shaft 130 to the main powder mixing unit 20; when the powder supplying shaft 130 stops rotating, the powder material stops leaking from the powder supplying cavity 110; a first inclined powder collecting plate 140 is installed below the first powder supplying space 111 and inclined toward the main powder mixing unit 20; the second inclined powder collecting plate 150 is installed below the second powder supplying space 112 and is inclined toward the main powder mixing unit 20; the two oblique powder collecting plates are combined into a V-shaped space with a gap in the middle, and the gap forms an opening 170 used for communicating with the main powder mixing unit 20; preferably, the included angle between the first oblique powder collecting plate 140 and the second oblique powder collecting plate 150 is more than 90 ° and less than 130 ° to increase the discharging speed and increase the collision force; the vertical plate 160 is installed at the lower end of the partition 113, and divides the V-shaped space formed by the two oblique powder collecting plates into two smaller V-shaped spaces, and two sides of the lower part of the vertical plate 160 are chamfered, so that two chamfered surfaces are respectively parallel to the first oblique powder collecting plate 140 and the second oblique powder collecting plate 150, so as to form a first powder conveying channel 180 and a second powder conveying channel 190; the small V-shaped space formed by the first oblique powder collecting plate 140 and the vertical plate 160 collects the powder discharged from the corresponding first powder supplying space 111 to the first powder conveying channel 180, the other small V-shaped space formed by the second oblique powder collecting plate 150 and the vertical plate 160 collects the powder discharged from the corresponding second powder supplying space 112 to the corresponding second powder conveying channel 190, and the two powder flow bundles are constrained by the two powder conveying channels, discharged in a nearly equal flow manner, and collided, impacted and mixed at the opening 170. Through setting up two defeated powder passageways that vertical plate obtained, can effectively prevent that two kinds of powders from because of the too big powder that causes of factors such as density difference, supply quantity difference in clearance department flow difference.
Referring to fig. 3 and 4, the longitudinal section of the main powder mixing unit 20 is an inverted trapezoid with two open ends, the inlet is a large opening, and the outlet is a small opening. Supply powder and nearly synchronous powder that lets to blow and strike mixing unit 10 and set up in its big opening side, equipartition mixing unit 40 with the little opening side intercommunication of main powder unit 20 that mixes is keeping away from supply powder and nearly synchronous powder that lets to blow and strike mixing unit 10 orientation, the main cross sectional area who mixes powder unit 20 reduces gradually. Preferably, the cross section of the main powder mixing unit 20 is rectangular, and the length and width of the upper end opening of the main powder mixing unit 20 are the same as those of the powder supply and near-synchronous powder discharge impact mixing unit 10, so as to improve the sealing performance of the transition position between the powder supply and near-synchronous powder discharge impact mixing unit 10 and the main powder mixing unit 20. An electric control valve 220 is arranged between the main powder mixing unit 20 and the uniform distribution mixing unit 40, and the electric control valve 220 is electrically connected with the control unit and is controlled by the control unit to be opened and closed. Further, the little opening side of main powder mixing unit 20 even has powder portion 210 that converges, equipartition mixing unit 40 with powder portion 210 intercommunication converges, just electrical control valve 220 sets up equipartition mixing unit 40 with powder portion 210 between with control intercommunication between the two or turn-off. The powder materials falling from the openings 170 of the powder supply and near-synchronous powder discharge impact mixing unit 10 are converged and mixed in the powder converging part 210; preferably, the hollow channel of the powder collector 210 has a square cross-section.
Referring to fig. 1, the gas mixing unit 30 includes a gas pump 310, a gas inlet pipe 320, and a gas outlet pipe 330. The air pump 310 is disposed outside the main powder mixing unit 20 and electrically connected to the control unit, and the control unit controls the on/off of the main powder mixing unit. One end of the air inlet pipe 320 is connected with the air outlet of the air pump 310, and the other end of the air inlet pipe is communicated with the side wall of the main powder mixing unit 20, and the communicating port of the air inlet pipe is close to the electric control valve 220 and is positioned above the electric control valve 220. Preferably, the air inlet pipe 320 communicates with a sidewall of the powder convergence portion 210. One end of the air outlet pipe 330 is connected to the air inlet of the air pump 310, the other end of the air outlet pipe is communicated with the side wall of the main powder mixing unit 20, and the communication port of the air outlet pipe is close to the powder supply and near-synchronous powder discharge impact mixing unit 10, so that external air is prevented from entering the main powder mixing unit 20 at the bottom air flow impact mixing stage to reduce the oxidation of powder materials.
Referring to FIG. 5, the equipartition mixing unit 40 includes a first dispersion chamber 410, a powder collection chamber 420, and a second dispersion chamber 430. The longitudinal sections of the first dispersing cavity 410, the powder collecting cavity 420 and the second dispersing cavity 430 are all trapezoidal with two open ends, and the powder collecting cavity 420 is between the first dispersing cavity 410 and the second dispersing cavity 430 and is communicated with the first dispersing cavity and the second dispersing cavity 430. The small opening side of the first dispersion chamber 410 is fixed on the powder converging portion 210 and is communicated with the powder converging portion 210 through a screw or the like, the large opening side of the first dispersion chamber 410 is connected with the large opening side of the powder collecting chamber 420, the small opening side of the second dispersion chamber 430 is connected with the small opening side of the powder collecting chamber 420, the cross sectional areas of the first dispersion chamber 410 and the second dispersion chamber 430 are gradually increased along the powder leakage direction, and the cross sectional area of the powder collecting chamber 420 is gradually reduced, so that an internal cavity structure with a 'widening-narrowing-widening' type space size regularly changed is formed. A plurality of flow channel plates 411 are arranged in each of the first dispersion cavity 410 and the second dispersion cavity 430, and the flow channel plates 411 are radially arranged from the small opening side of the first dispersion cavity 410 to the large opening side of the second dispersion cavity to form a plurality of radial sub-flow channels 412. The powder material discharged from the powder converging portion 210 flows along the first dispersing chamber 410, the powder collecting chamber 420 and the second dispersing chamber 430, and is uniformly dispersed and mixed when passing through the branch passage 412 and is collected and mixed when passing through the powder collecting chamber 420. The powder material discharged from the powder converging portion 210 is further mixed by the process of dispersing, uniformly distributing, converging, dispersing and uniformly distributing through the internal structure of the uniformly distributing and mixing unit 40. Preferably, more than two uniformly distributed mixing units 40 are connected in series, the two adjacent uniformly distributed mixing units 40 are connected in series through the mutual communication of the large opening side of one uniformly distributed mixing unit 40 and the small opening side of the other uniformly distributed mixing unit 40, and the mixing effect is improved through the series connection of the uniformly distributed mixing units 40. Further, the large opening of the second dispersion cavity 430 is used as the powder material outlet of the uniform mixing unit 40, and the width of the large opening of the second dispersion cavity 430 is the same as that of the scraper in the SLM forming chamber (not shown), so that the powder is uniformly dispersed into a powder beam with the same width as that of the scraper through the second dispersion cavity 430, and the powder can be fully spread by one layer on the forming platform through the scraper.
Further, more than one ultrasonic vibration block 230 is arranged on the outer side wall of the main powder mixing unit 20 through screws and the like, the ultrasonic vibration block 230 is driven by an ultrasonic generator electrically connected with the control unit, and the ultrasonic vibration block 230 keeps vibrating in the powder material mixing stage and 2 seconds to 10 seconds after the powder material is mixed, so that the powder material cannot be adhered to the inner walls of all parts in the device in the mixing and flowing processes, and the powder discharged from the hopper can be completely discharged out of the device.
Referring to fig. 6, a gradient material powder mixing method according to the present invention is described based on the structure of the gradient material powder mixing apparatus, and the gradient material powder mixing method according to the present invention includes the following steps:
step S10: and (3) a near-synchronous powder discharging impact mixing stage of powder materials with different components.
Powder materials with different basic components are respectively placed into different powder supply spaces, the control unit respectively controls the powder supply shafts 130 arranged at the outlets of the two powder supply spaces to discharge powder at different rotation speeds within the same time according to the components of the gradient material part, so that the powder of the two powder supply spaces is discharged approximately synchronously, the powder materials with different components respectively discharge from the two powder supply spaces and then move downwards along the first inclined powder collecting plate 140 and the second inclined powder collecting plate 150, and are respectively collected at the opening 170 through the first powder conveying channel 180 and the second powder conveying channel 190, so that two powder flow beams collide with each other, and the first powder mixing is realized.
Step S20: bottom convergence-airflow impact multiple circulation mixing stage.
The powder material flowing into the main powder mixing unit 20 from the opening 170 falls downward by gravity and falls directly or along the inner wall of the main powder mixing unit 20 to the bottom of the main powder mixing unit 20, i.e., the powder converging portion 210, and the powder material is converged and mixed again at the bottom of the main powder mixing unit 20 because the inner wall of the main powder mixing unit 20 becomes gradually smaller. At this time, the control unit controls the electrically controlled valve 220 to be in a closed state.
After the powder material is gathered in the powder gathering portion 210, the control unit controls the air pump 310 to start for more than 2 seconds and less than 20 seconds, air enters the powder gathering portion 210 from the air inlet pipe 320 to impact the powder material from the bottom of the main powder mixing unit 20 upwards, powder particles are collided and mixed with each other in space, air flow impact mixing is achieved, the powder material drops into the powder gathering portion 210 again under the action of gravity after being thrown to a certain degree, and gaps formed by the powder which is just flushed away by the air are filled. The circulation lasts for 2-20s, the powder particles are fully mixed, the falling process of the thrown powder is also influenced by the main powder mixing unit 20 with gradually reduced cross section area, the falling process is gradually converged and further mixed with other powder particles, and the circulation is repeated, so that the bottom convergence and the air flow impact multiple times of circulation mixing are realized. Preferably, the ultrasonic vibration block 230 is controlled to continuously vibrate at this stage to prevent powder from staying on the inner wall of the main powder mixing unit 20.
Step S30: and (3) uniformly mixing the powder materials.
After the air flow impact mixing is completed, the electric control valve 220 is opened, the powder material flows into the uniform distribution mixing unit 40 from the powder convergence part 210, passes through the first dispersion chamber 410, the powder collection chamber 420 and the second dispersion chamber 430 respectively, and is discharged out of the gradient material powder mixing device after undergoing a mixing process of dispersion, uniform distribution, collection, dispersion and uniform distribution under the action of the branch flow passage 412. During this process and within 2-10 seconds after substantially no powder particles are discharged from the apparatus, the control unit controls the ultrasonic vibration block 230 to maintain vibration to ensure that all the powder particles in the gradient powder mixing apparatus are discharged. The uniform distribution mixing unit 40 further mixes the powder discharged downwards, and arranges the powder flow into the same width of the scraper in the SLM forming chamber so that the scraper can fully spread the powder on a layer on a forming platform, the uniform distribution mixing unit 40 is composed of a powder collecting cavity 420 sandwiched between a first dispersing cavity 410 and a second dispersing cavity 430 which are provided with radial branch channels 412, the first dispersing cavity 410 and the second dispersing cavity 430 with the radial branch channels can disperse and uniformly distribute the powder from the radial branch channels in a dot-lump shape, the powder collecting cavity 420 with the gradually reduced cross-sectional area can collect the uniformly dispersed powder, and the further mixing of the powder is realized through the uniform distribution, collection and uniform distribution. By sequentially arranging a plurality of groups of dispersing cavities, powder collecting cavities and dispersing cavities, a better mixing effect can be obtained.
Compared with the prior art, the gradient material powder mixing method provided by the invention combines airflow impact to realize multiple times of mixing in the process that the powder naturally falls under the action of gravity, and improves the mixing efficiency and the mixing effect.
Further, the gas flow in the gas flow impact mixing step is from the gas in the forming chamber of the selective laser melting additive manufacturing equipment, and external air is not introduced.
Example (b):
in this embodiment, the gradient material powder mixing method provided by the present invention is combined with the gradient material powder mixing apparatus provided by the present invention to manufacture a gradient material component.
In the gradient material powder mixing device, the powder supply and near-synchronous powder discharge impact mixing unit 10 is divided into a first powder supply space 111 and a second powder supply space 112 by a partition 113, and the first inclined powder collecting plate 140 is installed below the first powder supply space 111 and inclined toward the main powder mixing unit 20; the second inclined powder collecting plate 150 is installed below the second powder supplying space 112 and is inclined toward the main powder mixing unit 20; the two oblique powder collecting plates are combined into a V-shaped space with a gap in the middle, and the gap forms an opening 170 used for communicating with the main powder mixing unit 20; the partition plate 113 is positioned right above the opening 170, the vertical plate 160 is installed at the lower end of the partition plate 113, so as to divide the V-shaped space formed by the two oblique powder collecting plates into two smaller small V-shaped spaces, and two sides of the lower part of the vertical plate 160 are chamfered, so that two chamfered surfaces are respectively parallel to the first oblique powder collecting plate 140 and the second oblique powder collecting plate 150, so as to form a first powder conveying channel 180 and a second powder conveying channel 190; the small V-shaped space formed by the first oblique powder collecting plate 140 and the vertical plate 160 collects the powder discharged from the corresponding first powder supplying space 111 to the first powder conveying channel 180, the other small V-shaped space formed by the second oblique powder collecting plate 150 and the vertical plate 160 collects the powder discharged from the corresponding second powder supplying space 112 to the corresponding second powder conveying channel 190, and the two powder flow bundles are constrained by the two powder conveying channels, discharged in a nearly equal flow manner, and collided, impacted and mixed at the opening 170. A first powder supplying shaft 131 is arranged between the first powder supplying space 111 and the first inclined powder collecting plate 140, a second powder supplying shaft 132 is arranged between the second powder supplying space 112 and the second inclined powder collecting plate 150, the first powder supplying motor 121 drives the first powder supplying shaft 131 to rotate, and the second powder supplying motor 122 drives the second powder supplying shaft 132 to rotate. The first powder supply shaft 131 and the second powder supply shaft 132 are both spline shafts, the powder supply amount is determined by the rotation time and speed of the spline shafts, the starting time and duration of the rotation of the first powder supply shaft 131 and the second powder supply shaft 132 are the same, but the speed can be adjusted by the control unit according to different gradient component ratios, so as to ensure that the powder can be discharged approximately synchronously. The first powder supply motor 121 and the second powder supply motor 122 are stepping motors. The main powder mixing unit 20 is an integrated structure manufactured by casting or 3D printing and matching machine processing. The electrically controlled valve 220 includes a valve plate 221 and a control motor 222. The control motor 222 is a stepping motor, and a motor shaft passes through a sidewall of the powder convergence part 210, and the valve plate 221 is fixed at a distal end of the motor shaft of the control motor 222. The valve plate 221 is a block body having a cross section identical to the cross sectional area of the hollow passage of the powder convergence part 210, and has a height smaller than the length and width of the cross section, and one end of the valve plate is fixed to a motor shaft of a control motor 222 located inside the powder convergence part 210. When the cross section of the valve plate 221 faces the powder supply and near-synchronous powder discharge impact mixing unit 10, the electric control valve 220 is in a closed state; when the control motor 222 drives the valve plate 221 to rotate 90 degrees around the motor shaft of the control motor 222 from the cross section of the valve plate 221 toward the powder supply and near-synchronous powder discharge impact mixing unit 10, the electric control valve 220 is in a fully open state, and the powder material is discharged. Preferably, a sealing rubber strip for preventing powder leakage when the electrically controlled valve 220 is closed is arranged on the valve plate 221. A proximity switch 223 installed on the motor mounting seat 225 perpendicularly to the horizontal direction, an induction iron 224 installed on the motor shaft of the control motor 222 and located outside the powder convergence part 210, and allowing the induction iron 224 to be coaxial with the proximity switch 223 when the valve plate 221 is in the closed state; the proximity switch 223 is electrically connected to the control unit. When the valve plate 221 needs to be closed, when the motor shaft rotates until the induction iron 224 and the proximity switch 223 are coaxial, the proximity switch 223 feeds back a position signal to the control unit, and the control unit controls the control motor 222 to stop rotating, so that the valve plate is closed in position; when the valve plate 221 needs to be opened, the control unit controls the control motor 222 to take the position of the proximity switch 223 as a position zero point, rotate 90 degrees and then stop, and then the valve plate 221 reaches an opening state.
Referring to fig. 7, a is a 316L stainless steel single material area, b is a gradient material area formed by mixing 80% of 316L stainless steel and 20% of bronze material by volume ratio, c is a gradient material area formed by mixing 50% of 316L stainless steel and 50% of bronze material by volume ratio, d is a gradient material area formed by 20% of 316L stainless steel and 80% of bronze material by volume ratio, and e is a bronze single material area. In the SLM forming process, the thickness of each layer is generally 30-50 microns, and since the powder spreading device adopted in the SLM additive manufacturing process is based on the principle that the scraper of the powder bed spreads a layer of powder onto the forming platform to realize powder presetting, the powder supply amount in each time is at least a single-layer powder amount. Assuming that the first powder supply shaft 131 and the second powder supply shaft 132 have the same structure, each shaft is provided with 6 spline grooves, and the volume of each 4 spline grooves corresponds to one layer of powder amount, that is, when the number of the spline grooves crossing right below the powder supply space when the first powder supply shaft 131 or the second powder supply shaft 132 rotates is greater than or equal to 4, one layer of powder can be fully paved. Before the gradient material powder mixing device is started to mix the powder materials, bronze powder is placed in the first powder supply space 111, 316L stainless steel powder is placed in the second powder supply space 112, and the powder materials are mixed and paved according to the molding sequence of a region a- > a region b- > a region c- > a region d- > a region e, wherein the process comprises the following steps:
the first step is as follows: and (c) paving the area a.
After the current material area a is judged to be a single material area adopting 316L stainless steel powder, powder can be directly spread without powder mixing. Under the control of the control unit, the ultrasonic vibration powder block 230 vibrates and enables the electric control valve 220 to be in an open state, the second powder supply shaft 132 rotates to enable 4 spline grooves on the shaft to sequentially cross right below a powder supply space, 4 units of 316L stainless steel powder are discharged into the main powder mixing unit 20 and enter the uniformly-distributed mixing unit 40 through the powder gathering part 210, the uniformly-distributed mixing unit 40 finally disperses and uniformly distributes the powder into powder flow beams with the width equal to that of a scraper in the SLM forming chamber and finally discharges the powder flow beams into the forming chamber, and required powder materials are provided for powder laying operation before laser scanning forming of the material region a. Within 2-10 seconds after no powder particles are discharged from the device, the control unit controls the ultrasonic vibration block 230 to keep vibrating, so as to ensure that all the powder discharged from the hopper can be discharged out of the gradient powder mixing device.
The second step is that: and (c) paving the area b.
The material composition of the current material area b is judged to be formed by mixing 80% of 316L stainless steel and 20% of bronze material by volume ratio. Under the control of the control unit, the ultrasonic vibration powder block 230 vibrates and enables the electric control valve 220 to be in a closed state, while the first powder supply shaft 131 rotates to allow 1 spline groove on the shaft to cross right below the powder supply space to leak out 1 unit of bronze powder, the second powder supply shaft 132 rotates to make 4 spline grooves on the shaft cross right below the powder supply space to leak 4 units of 316L stainless steel, 4 units of 316L stainless steel powder and 1 unit of bronze powder leak into the main powder mixing unit 20 almost simultaneously, the rotation speed of the second powder supply shaft 132 is controlled by the control unit to be 4 times of the rotation speed of the first powder supply shaft 131, so that the two powder supply shafts complete the approximately synchronous discharge of the two powders in the same time, and meet at the opening 170 in the main powder mixing unit 20 for counter-impact mixing to achieve preliminary mixing of the powders. When the primarily mixed powder continuously falls into the powder converging part 210 under the action of gravity, the primarily mixed powder is converged and mixed at the bottom, at this time, the air pump 310 is started, the air flow output by the air pump 310 through the air inlet pipe 320 enters the powder converging part 210, the powder impacts the powder from bottom to top, the powder in the powder converging part 210 moves upwards, the powder particles collide and mix with each other in the air, the powder particles always rise to a certain distance and then deviate from the original position in the horizontal direction, the upward impact force of the air flow in the new horizontal direction position is insufficient to support the powder particles in the air, therefore, the powder particles fall under the action of gravity, fill the gap formed by the powder which is just flushed away, and then are thrown up, the circulation lasts for 2-20s, the powder particles are fully mixed, and in the falling process of the thrown-up powder, the influence of the gradual reduction of the cross-sectional area of the main powder mixing unit 20, the falling process is gradually converged and further mixed with other powder particles, namely, bottom convergence mixing and air flow impact mixing are carried out repeatedly and synchronously. After the air pump 310 is started for 2-20s, the air pump 310 is stopped, the powder falls into the powder converging portion 210 again under the action of gravity, and at this time, the electronic control valve 220 is controlled to be opened, and the powder is discharged into the uniform distribution mixing unit 40. The first dispersing cavity 410 with the radial flow channels can disperse and uniformly distribute powder from a point-to-point shape into the radial flow channels, the powder collecting cavity 420 can gather the dispersed and uniformly distributed powder together, then the dispersed and uniformly distributed powder is dispersed and uniformly distributed through the second dispersing cavity 430, and further mixing of the powder is realized through the dispersed and uniformly distributed-collected-dispersed and uniformly distributed, and finally the powder is dispersed and uniformly distributed into a powder flow beam with the same width as a scraper in the SLM forming chamber. Finally, after the powder is further mixed, dispersed and uniformly distributed by the uniformly-distributed mixing unit 40, the powder is poured into a forming chamber, so that required powder materials are provided for the powder laying operation before the laser scanning forming of the layer material area b. In the whole powder mixing process and within 2-10 seconds after no powder particles are discharged from the device, the ultrasonic vibration powder block 230 keeps vibrating, so that the powder cannot be adhered to the inner walls of all parts in the device in the mixing and flowing processes, and the powder discharged from the hopper can be completely discharged out of the device.
The third step: and (c) paving the area c.
The material composition of the current material area c is judged to be formed by mixing the 316L stainless steel with the 50% bronze material in the volume ratio. Under the control of the control unit, the ultrasonic vibration powder block 230 vibrates and makes the electric control valve 220 in a closed state, while the first powder supply shaft 131 rotates to make 2 spline grooves on the shaft cross right below the powder supply space to leak 2 units of bronze powder, the second powder supply shaft 132 makes 2 spline grooves on the shaft cross right below the powder supply space to leak 2 units of 316L stainless steel, the control unit controls the rotation speed of the second powder supply shaft 132 to be the same as that of the first powder supply shaft 131, so that the two powder supply shafts complete approximately synchronous discharge of the two powders in the same time, and meet at the opening 170 in the main powder mixing unit 20 to realize opposite flushing mixing of the powders, thereby realizing primary mixing of the powders. When the primarily mixed powder continuously falls into the powder gathering part 210 under the action of gravity, the primarily mixed powder is gathered and mixed at the bottom, the air pump 310 is started, the air flow output by the air pump 310 through the air inlet pipe 320 flows into the main powder mixing unit 20 and impacts the powder from the bottom upwards, the powder in the powder gathering part 210 moves upwards, the powder particles collide and mix with each other in mid-air, the powder particles always rise to a certain distance and then deviate from the original position in the horizontal direction, the upward impact force of the air flow in the new horizontal direction position is insufficient to support the powder particles in the air, and therefore the powder particles fall under the action of gravity, fill the gaps formed by the powder which is just washed away and then are thrown up, the circulation lasts for 2-20s, the powder particles are fully mixed, and the influence of the gradual reduction of the cross section area of the main powder mixing unit 20 is also applied in the process of the falling of the thrown-up powder, the falling process is gradually converged and further mixed with other powder particles, namely, bottom convergence mixing and air flow impact mixing are carried out repeatedly and synchronously. After the air pump 310 is started for 2-20s, the air pump 310 is stopped, the powder falls into the powder converging portion 210 again under the action of gravity, and at this time, the electronic control valve 220 is controlled to be opened, and the powder is discharged into the uniform distribution mixing unit 40. The first dispersing cavity 410 with the radial flow channels can disperse and uniformly distribute powder from a point-to-point shape into the radial flow channels, the powder collecting cavity 420 can gather the dispersed and uniformly distributed powder together, then the dispersed and uniformly distributed powder is dispersed and uniformly distributed through the second dispersing cavity 430, and further mixing of the powder is realized through the dispersed and uniformly distributed-collected-dispersed and uniformly distributed, and finally the powder is dispersed and uniformly distributed into a powder flow beam with the same width as a scraper in the SLM forming chamber. Finally, after the powder is further mixed, dispersed and uniformly distributed by the uniformly-distributed mixing unit 40, the powder is poured into a forming chamber, so that required powder materials are provided for the powder laying operation before the laser scanning forming of the layer material area c. In the whole powder mixing process and within 2-10 seconds after no powder particles are discharged from the device, the ultrasonic vibration powder block 230 keeps vibrating, so that the powder cannot be adhered to the inner walls of all parts in the device in the mixing and flowing processes, and the powder discharged from the hopper can be completely discharged out of the device.
The fourth step: and d, paving the area.
The material composition of the current material area d is determined to be formed by mixing 20% of 316L stainless steel and 80% of bronze material by volume ratio. Under the control of the control unit, the ultrasonic vibration powder block 230 vibrates and makes the electric control valve 220 in a closed state, when the first powder supply shaft 131 rotates to make 4 spline grooves on the shaft cross right below the powder supply space to leak 4 units of bronze powder, the second powder supply shaft 132 makes 1 spline groove on the shaft cross right below the powder supply space to leak 1 unit of 316L stainless steel, 1 unit of 316L stainless steel powder and 4 units of bronze powder are simultaneously leaked into the main powder mixing unit 20, the control unit controls the rotation speed of the first powder supply shaft 131 to be 4 times of the rotation speed of the second powder supply shaft 132, so that the two powder supply shafts complete approximately synchronous discharge of the two powders in the same time, and meet, flush and mix at the opening 170 in the main powder mixing unit 20, and primary mixing of the powders is realized. When the primarily mixed powder continuously falls into the powder gathering part 210 under the action of gravity, primary powder gathering and mixing are realized, the air pump 310 is started, the air flow output by the air pump 310 through the air inlet pipe 320 flows into the main powder mixing unit 20 and impacts the powder from the bottom upwards, the powder in the powder gathering part 210 moves upwards, powder particles collide and mix with each other in mid-air, all the powder particles rise to a certain distance and then deviate from the original position in the horizontal direction, so that the upward impact force of the air flow in the new horizontal direction position is insufficient to support the powder particles in the air, the powder particles fall under the action of gravity, gaps formed by the powder which is just flushed are filled, and then the powder particles are thrown, the circulation lasts for 2-20s, the powder particles are fully mixed, and the influence of the gradual reduction of the cross section area of the main powder mixing unit 20 in the falling process of the upward thrown powder is realized, the falling process is gradually converged and further mixed with other powder particles, namely, bottom convergence mixing and air flow impact mixing are carried out repeatedly and synchronously. After the air pump 310 is started for 2-20s, the air pump 310 is stopped, the powder falls into the powder converging portion 210 again under the action of gravity, and at this time, the electronic control valve 220 is controlled to be opened, and the powder is discharged into the uniform distribution mixing unit 40. The first dispersing cavity 410 with the radial flow channels can disperse and uniformly distribute powder from a point-to-point shape into the radial flow channels, the powder collecting cavity 420 can gather the dispersed and uniformly distributed powder together, then the dispersed and uniformly distributed powder is dispersed and uniformly distributed through the second dispersing cavity 430, and further mixing of the powder is realized through the dispersed and uniformly distributed-collected-dispersed and uniformly distributed, and finally the powder is dispersed and uniformly distributed into a powder flow beam with the same width as a scraper in the SLM forming chamber. Finally, after the powder is further mixed, dispersed and uniformly distributed by the uniformly-distributed mixing unit 40, the powder is poured into a forming chamber, and a required powder material is provided for the powder laying operation before the laser scanning forming of the layer material area d. In the whole powder mixing process and within 2-10 seconds after no powder particles are discharged from the device, the ultrasonic vibration powder block 230 keeps vibrating, so that the powder cannot be adhered to the inner walls of all parts in the device in the mixing and flowing processes, and the powder discharged from the hopper can be completely discharged out of the device.
The fifth step: and (5) paving an area e.
After the current material area e is judged to be a single material area adopting bronze powder, powder can be directly spread without powder mixing. Under the control of the control unit, the ultrasonic vibration powder block 230 vibrates and enables the electric control valve 220 to be in an open state, the first powder supply shaft 131 rotates to enable 4 spline grooves on the shaft to cross right below a powder supply space, 4 units of bronze powder are discharged into the main powder mixing unit 20 and enter the uniformly-distributed mixing unit 40 through the powder gathering part 210, the uniformly-distributed mixing unit 40 finally disperses and uniformly distributes the powder into powder flow beams with the width equal to that of a scraper in the SLM forming chamber and finally discharges the powder flow beams into the forming chamber, and required powder materials are provided for powder paving operation before laser scanning forming of the material region e of the layer. Within 2-10 seconds after no powder particles are discharged from the device, the control unit controls the ultrasonic vibration block 230 to keep vibrating, so as to ensure that all the powder discharged from the hopper can be discharged out of the gradient powder mixing device.
To this end, a layer of material is printed. And repeating the first step to the fifth step until the 3D printing work of the whole part is completed.
The above-described embodiments of the present invention are merely illustrative of several embodiments of the present invention, which are described in detail and specific, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (9)
1. A gradient material powder mixing arrangement which characterized in that: comprises that
The longitudinal section of the main powder mixing unit is an inverted trapezoid with openings at two ends, and the inlet of the main powder mixing unit is a large opening while the outlet of the main powder mixing unit is a small opening;
the powder supply and near-synchronous powder discharge impact mixing unit is arranged on the large opening side of the main powder mixing unit; the powder supply and near-synchronous powder discharge impact mixing unit comprises a powder supply cavity provided with at least two powder supply spaces and a powder supply shaft arranged between the powder supply cavity and the main powder mixing unit to control the powder in the powder supply cavity to be discharged into the main powder mixing unit; and
the uniform distribution mixing unit comprises two dispersion cavities and a powder collection cavity which is clamped between the two dispersion cavities and communicated with the two dispersion cavities; the longitudinal sections of the dispersing cavity and the powder collecting cavity are inverted trapezoids with openings at two ends, and the small opening side of one dispersing cavity is communicated with the small opening side of the main powder mixing unit; more than two sub-channels radiating from the small opening to the large opening are arranged in the dispersion cavity; along the powder leakage direction, the cross sectional area of the dispersion cavity is gradually increased, and the cross sectional area of the powder collection cavity is gradually decreased.
2. The gradient material powder mixing device according to claim 1, wherein: the powder supply and near-synchronous powder discharge impact mixing unit also comprises a first inclined powder collecting plate, a second inclined powder collecting plate and a vertical plate; the first oblique powder collecting plate and the second oblique powder collecting plate are respectively oppositely arranged between the powder supply shaft and the main powder mixing unit and are inclined towards the main powder mixing unit; a gap is reserved between the first oblique powder collecting plate and the second oblique powder collecting plate; the vertical plate is arranged between the two powder supply cavities of the powder supply and near-synchronous powder discharge impact mixing unit and below the powder supply shaft, extends out of the main powder mixing unit, divides a V-shaped space formed by the two oblique powder collecting plates into two small V-shaped spaces, and chamfers are arranged on two sides of the lower part of the vertical plate, so that two chamfered surfaces are respectively parallel to the first oblique powder collecting plate and the second oblique powder collecting plate to form two powder conveying channels; the small V-shaped space formed by the first oblique powder collecting plate and the vertical plate collects powder discharged from the corresponding powder supply cavity to the corresponding powder conveying channel, the other small V-shaped space formed by the second oblique powder collecting plate and the vertical plate collects powder discharged from the other powder supply cavity to the corresponding other powder conveying channel, and the two powder flow beams are mixed in a gap formed by the first oblique powder collecting plate and the second oblique powder collecting plate.
3. The gradient material powder mixing device according to claim 2, wherein: also comprises a gas mixing unit; the gas mixing unit comprises a gas pump, a gas inlet pipe and a gas outlet pipe; the air inlet pipe is connected with an air outlet of the air pump; the air outlet pipe is connected with an air inlet of the air pump; the air pump is positioned outside the main powder mixing unit and is communicated with the side wall of the main powder mixing unit through the air inlet pipe and the air outlet pipe; the communicating port of the air inlet pipe is arranged at one side close to the uniformly distributed mixing units; and the communicating port of the air outlet pipe is arranged at one side close to the powder supply and near synchronous powder discharge impact mixing unit.
4. The gradient material powder mixing device according to claim 3, wherein: the main powder mixing unit also comprises an electric control valve; the electric control valve is arranged near the outlet of the main powder mixing unit.
5. The gradient material powder mixing device according to claim 4, wherein: the main powder mixing unit is provided with a powder gathering part; the powder converging part is a channel which is arranged at the small opening side of the main powder mixing unit and communicated with the uniformly distributed mixing units; the electric control valve is arranged at the outlet of the powder converging part close to the main powder mixing unit.
6. The gradient material powder mixing device according to claim 5, wherein: the ultrasonic vibration block is also included; the ultrasonic vibration block is arranged on the outer side wall of the main powder mixing unit.
7. The gradient material powder mixing device according to claim 6, wherein: also includes a control unit; the powder supply and near-synchronous powder discharge impact mixing unit also comprises a powder supply motor, and the powder supply motor drives the powder supply shaft to rotate; the control unit is respectively electrically connected with the powder supply motor, the electric control valve, the air pump and the ultrasonic vibration block and controls the switch of the ultrasonic vibration block.
8. A gradient material powder mixing method, characterized by comprising the steps of:
(1) near-synchronous powder discharging impact mixing, wherein when the near-synchronous powder discharging impact mixing is carried out, two beams of powder flow impact and mix with each other;
(2) bottom convergence-airflow impact multiple-cycle mixing: the mixed powder flow obtained in the step (1) is discharged and converged in a space with the gradually reduced cross section area, so that bottom convergence and mixing are realized; the mixed powder is converged at the bottom and is thrown upwards under the action of airflow, and powder particles are collided and mixed with each other in space to realize airflow impact mixing; the powder is subjected to bottom convergence and mixing again in the falling process; the above steps are repeated, so that bottom convergence and airflow impact are circularly mixed for multiple times;
(3) uniformly distributing and mixing, wherein when uniformly distributing and mixing are carried out, powder materials are dispersed and uniformly distributed through radial runners, powder mixing is realized through cavities arranged in an inverted trapezoid, and the powder is further mixed and uniformly distributed to be in a proper width according to more than one dispersing-converging-dispersing flow.
9. The gradient material powder mixing method according to claim 8, characterized in that: the gas flow in the gas flow impact mixing step is from the gas in the forming chamber of the selective laser melting additive manufacturing equipment, and external air is not introduced.
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