CN112371999B - Powder feeding system for 3d printing of large-size electron beam - Google Patents
Powder feeding system for 3d printing of large-size electron beam Download PDFInfo
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- CN112371999B CN112371999B CN202011044006.0A CN202011044006A CN112371999B CN 112371999 B CN112371999 B CN 112371999B CN 202011044006 A CN202011044006 A CN 202011044006A CN 112371999 B CN112371999 B CN 112371999B
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- 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
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Abstract
The invention provides a powder feeding system for large-size electron beam 3d printing, which solves the problems that the existing powder feeding system is low in efficiency, large in occupied space and overflow of powder, and uniform powder feeding cannot be realized. The system comprises a powder feeding device and a powder paving device; the powder feeding device comprises a powder feeding shell, a powder wheel assembly and a driving assembly; a powder feeding cavity is arranged in the powder feeding shell, a powder inlet is formed in the top of the powder feeding shell, and a powder outlet channel is formed in the bottom of the powder feeding shell; the powder wheel assembly comprises a transmission shaft, a powder feeding wheel and two side leakage prevention wheels, and the driving assembly is used for driving the transmission shaft to rotate; the powder spreading device is arranged below the powder feeding device and comprises a powder falling box and a powder scraping assembly; a plurality of powder falling cavities are arranged in the powder falling box, and a plurality of scattering plates are arranged in the powder falling cavities; the top of the powder dropping box is provided with a plurality of powder inlets communicated with the powder dropping cavity, the powder inlets are communicated with the powder outlet channel, and the bottom of the powder dropping box is provided with a plurality of powder outlets communicated with the powder dropping cavity; the powder scraping component comprises a soft scraping plate, a hard scraping plate and a compaction plate.
Description
Technical Field
The invention belongs to the field of additive manufacturing, and particularly relates to a powder feeding system for large-size electron beam 3d printing.
Background
Electron Beam Selective Melting (EBSM) metal additive manufacturing techniques use an electron beam as an energy source to manufacture solid parts by melting metal powder layer by layer in a high vacuum environment. Because the power of the electron beam is high, and the material has high energy absorption rate to the electron beam, the finished piece has the characteristics of high density, low oxygen content, low thermal stress, difficult deformation and cracking, high printing efficiency, high material utilization rate and the like, and is widely applied to the fields of medical treatment, aerospace and the like.
The process of Electron Beam Selective Melting (EBSM) metal additive manufacturing comprises the following steps: firstly, spreading a layer of powder on the surface of a powder bed, and preheating and insulating the powder by using an electron beam to meet the requirements of printing process parameters; secondly, selectively melting the electron beams under the control of a computer according to the cross section profile information, melting the metal powder under the bombardment of the electron beams, and bonding the metal powder with the formed part below to realize layer-by-layer accumulation until the whole part is completely melted; and finally, removing redundant powder to obtain the required three-dimensional product. In the 3D metal printing process, the density of the powder and whether the powder is spread flatly directly determine the density, strength, precision and quality of a formed part, so that the problem of improving the density of the powder is an urgent need to be solved.
At present, the electron beam selective melting forming technology is gradually matured, the forming efficiency and the forming precision are gradually improved, the maximum forming size of the device reaches phi 350 multiplied by 380mm, and the forming size precision reaches +/-0.3 mm. However, this technique cannot meet the production requirements for large members and cannot form large-sized members. Therefore, the method breaks through the technical bottleneck of continuously manufacturing large-size components, and is a key technology for improving the forming efficiency of large-size electron beam forming equipment.
If the manufacturing requirement of a large component is to be met, an annular continuous forming technology needs to be realized, and spiral scanning is the basis of annular electron beam continuous forming. If helical scanning is implemented, an effective continuous powder feeding system is required. The existing powder feeding system generally adopts a horizontal linear movement powder feeding mode, and if the powder feeding mode is used on large-size electron beam selective melting equipment, the printing efficiency is low, uniform powder feeding cannot be realized, and metal powder waste can be caused. Simultaneously, current shop's powder device has following problem: 1) The powder spreading mode is low in efficiency by adopting a roller powder spreading mode or a scraper powder scraping mode; 2) When the powder spreading roller spreads the powder into the forming cylinder, a large amount of powder is accumulated at the front end of the powder spreading roller, and when the accumulation amount is large, the powder overflows to the rear of the powder spreading roller, so that the powder which is spread is damaged, and the resistance is increased; 3) When the powder is scraped by adopting the scraper, the density of the powder is reduced because the paved powder is not compacted, so that the density of a formed part is reduced, and the porosity is improved; 4) The existing spiral powder laying mechanism needs to move up and down, and is complex and large in occupied space.
Disclosure of Invention
The invention aims to solve the problems that the existing powder feeding system is low in powder feeding efficiency, cannot realize uniform powder feeding, occupies a large space, and causes powder waste due to powder overflow, and provides a powder feeding system for large-size electron beam 3d printing.
In order to realize the purpose, the technical scheme adopted by the invention is as follows:
a powder feeding system for large-size electron beam 3d printing comprises a powder feeding device and a powder spreading device; the powder feeding device comprises a powder feeding shell, a plurality of groups of powder wheel assemblies and a plurality of groups of driving assemblies, wherein the length direction of the powder feeding shell is set to be the X direction, the width direction of the powder feeding shell is set to be the Y direction, and the height direction of the powder feeding shell is set to be the Z direction; a powder feeding cavity is arranged in the powder feeding shell, at least one powder inlet is formed in the top of the powder feeding shell and communicated with the powder feeding cavity, a plurality of powder discharging channels communicated with the powder feeding cavity are formed in the bottom of the powder feeding shell along the X direction, and the number of the powder discharging channels is the same as that of the powder wheel assemblies and the driving assemblies; the powder wheel assembly comprises a transmission shaft, a powder feeding wheel and two side leakage prevention wheels, the transmission shaft is arranged in the powder outlet channel, and the axis of the transmission shaft is parallel to the Y direction; the powder feeding wheel and the side leakage prevention wheel are sleeved on the transmission shaft, the powder feeding wheel is positioned between the two side leakage prevention wheels, a plurality of wheel grooves of the powder feeding wheel are uniformly distributed along the circumferential direction of the powder feeding wheel, and a plurality of annular wheel grooves of the side leakage prevention wheel are arranged along the axial direction of the side leakage prevention wheel and are arranged at an angle of 90 degrees with the wheel grooves of the powder feeding wheel; the driving assembly is arranged outside the powder feeding shell, and the output end of the driving assembly is connected with the transmission shaft and used for driving the transmission shaft to rotate; the powder spreading device is arranged below the powder feeding device and comprises a powder dropping box and a plurality of groups of powder scraping components which are arranged at the bottom of the powder dropping box; a plurality of powder falling cavities which are arranged along the X direction are arranged in the powder falling box, and a plurality of scattering plates are arranged in the powder falling cavities and used for scattering powder falling into the powder falling cavities; the powder feeding device comprises a powder feeding shell, a powder falling cavity, a powder feeding cavity, a powder discharging cavity and a powder discharging box, wherein the powder feeding cavity is communicated with the powder falling cavity; the powder scraping component comprises a soft scraping plate, a hard scraping plate and a compacting plate, and the powder outlet, the soft scraping plate, the hard scraping plate and the compacting plate are sequentially arranged along the Y direction; the soft scraping plate is of a comb-tooth-shaped structure and comprises a plurality of scraping strips arranged along the X direction; the powder scraping end face of the hard scraper is equal to the powder scraping end face of the soft scraper in the Z direction; and the powder pressing end face of the compacting plate is lower than the powder scraping end face of the hard scraper plate in the Z direction.
Furthermore, the powder outlet channel comprises a first channel, a second channel and a third channel which are sequentially communicated along the Z direction; the first channel is a trapezoid channel, the large end of the first channel is communicated with the powder feeding cavity, the small end of the first channel is communicated with the second channel, the second channel is obliquely arranged with the XY plane, the central line of the second channel and the central line of the first channel are arranged at a certain angle when viewed from the XZ plane, and the central line of the third channel is parallel to the central line of the first channel.
Further, the powder wheel assembly is arranged in the second channel, and the gap between the powder feeding wheel and the second channel is larger than the maximum size of the powder particles, so that the powder particles can pass through smoothly.
Further, the angle between the central line of the second channel and the central line of the first channel is 100-160 degrees.
Furthermore, the width of the small end of the first channel is the same as that of the powder feeding wheel, and the width of the third channel is the same as the sum of the widths of the powder feeding wheel and the wheel grooves of the two side leakage prevention wheels.
Furthermore, the multiple groups of driving assemblies are arranged on two sides of the powder feeding shell in a staggered mode, each driving assembly comprises a servo motor, the transmission shaft is connected with a driving shaft of each servo motor through a coupler, and the transmission shaft is arranged on the powder feeding shell through a bearing assembly.
Further, the scattering plates are arranged on a front side plate and a rear side plate of the powder falling box, which are opposite to each other along the Y direction, and the scattering plates arranged on the front side plate and the scattering plates arranged on the rear side plate are arranged in a staggered mode in the X direction and the Z direction.
Furthermore, the scattering plate is a triangular flat plate, and the inclined side edge of the triangular flat plate is used for scattering the powder falling into the powder falling cavity.
Furthermore, the powder pressing end face of the compacting plate is an arc-shaped face.
Furthermore, a plurality of partition plates are arranged between the hard scraping plate and the compacting plate.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
1. the powder feeding device of the powder feeding system can realize active automatic powder feeding, multi-motor multi-point driving, the powder feeding efficiency is improved, the powder feeding is automatic, continuous and efficient production can be realized, the powder feeding device can meet different powder feeding quantity requirements of different areas by controlling the rotating speed of each motor, and then the requirement of uniform powder spreading thickness on a rotary worktable is met, so that high-precision forming manufacturing is completed.
2. The powder feeding device of the powder feeding system adopts a sectional powder feeding mode, the powder output amount is controlled by the rotating speed of the powder feeding wheel, when a small part is printed, the powder feeding motor with a larger diameter can be controlled to stop rotating, the powder feeding is stopped at the excircle, the diameter of the spread powder is reduced along the radial direction, and the powder waste is avoided.
3. Each powder wheel component of the powder feeding device of the powder feeding system mainly comprises a powder feeding wheel and two side leakage prevention wheels (symmetrically arranged on two sides of the powder feeding wheel), the clearance between the powder feeding wheel and a powder wheel cavity fully considers that powder can pass through without blockage, and the side leakage prevention wheels can prevent blockage and introduce side leakage powder particles into an outlet.
4. The powder feeding device of the powder feeding system can be arranged outside the vacuum forming chamber, the working environment of the motor and the mechanism is good, and meanwhile, the structure is simple, and the use and the disassembly and the assembly are convenient.
5. According to the powder paving device of the powder feeding system, the soft scraper, the hard scraper and the compacting plate are sequentially arranged at the powder outlet, the powder paving quality is ensured by a powder scraping and compacting mode, the compacting effect is good, and the quality of a formed part is increased; meanwhile, the powder spreading device can work in cooperation with a rotary workbench, continuous spreading and scraping compaction is achieved, and working efficiency is improved.
6. The soft scraper is arranged in front of the hard scraper of the powder spreading device of the powder feeding system, and pre-pushes the powder uniformly by the soft scraper, so that the stress of the hard scraper is reduced, the soft scraper pushes the redundant powder to the side of the rotary powder bed, and finally the powder bed is pushed out, and the problem that the powder can overflow is avoided.
7. The powder spreading device of the powder feeding system is internally provided with the scattering plate for scattering the powder falling into the powder falling cavity, so that uniform powder falling is realized.
8. The powder spreading device of the powder feeding system does not need a lifting device, and does not need devices such as a powder feeding cylinder, a powder recovery cylinder and the like, so that the space of a vacuum chamber is saved, and the processing can be realized through a smaller vacuum chamber. Meanwhile, the powder paving device is small in weight and size, manufacturing cost is greatly reduced, and installation, adjustment, replacement and improvement are facilitated.
Drawings
FIG. 1 is a schematic structural diagram of a large-size electron beam 3d printing apparatus according to the present invention;
FIG. 2 is a schematic view of the powder feeder of the present invention;
FIG. 3 isbase:Sub>A cross-sectional view A-A of FIG. 2;
FIG. 4 is a schematic view of a powder outlet channel of the powder feeding device of the present invention;
FIG. 5 is a schematic structural view of the impeller assembly of the present invention;
FIG. 6 is a schematic view of the mounting of the inventive impeller assembly;
FIG. 7 is a schematic sectional view of the powder spreading section of the powder feeder of the present invention;
FIG. 8 is a schematic structural view of the powder laying device of the present invention;
FIG. 9 isbase:Sub>A cross-sectional view A-A of FIG. 8;
FIG. 10 is an enlarged view of a portion of FIG. 9;
FIG. 11 is a schematic view of the construction of the soft squeegee of the present invention;
FIG. 12 is a schematic view of the powder end face of the compacting plate according to the present invention;
FIG. 13 is a schematic view of the installation of the powder spreading device of the present invention;
FIG. 14 is a schematic view of the position relationship between the work table and the powder spreading device according to the present invention;
FIG. 15 is a schematic diagram of the position relationship between the stage and the scanning area according to the present invention.
Reference numerals: 1-powder feeding device, 2-powder spreading device, 3-electron gun, 4-printing chamber, 5-workbench unit, 7-workpiece, 8-follow-up powder cylinder, 11-powder feeding shell, 12-powder wheel assembly, 13-driving assembly, 111-powder feeding cavity, 112-powder inlet, 113-powder outlet channel, 1131-first channel, 1132-second channel, 1133-third channel, 121-transmission shaft, 122-powder feeding wheel, 123-side leakage prevention wheel, 131-servo motor and 132-coupler. 21-powder dropping box, 22-powder scraping component, 211-powder dropping cavity, 212-dispersing plate, 213-powder inlet, 214-powder outlet, 221-soft scraper, 222-hard scraper, 223-compacting plate, 224-separating plate, 2211-scraper bar, 2212-powder scraping end face and 2231-powder compacting end face.
Detailed Description
The invention is described in further detail below with reference to the figures and specific embodiments.
The invention provides a powder feeding system for 3d printing of a large-size electron beam, which is suitable for large-size Electron Beam Selective Melting (EBSM) equipment. Based on the design, the powder supply box, the powder flow, the powder dropping pipeline and the powder feeding uniformity are designed, so that the dynamic powder feeding system with adjustable powder feeding amount is realized, the problems of waste and low efficiency of large-size SEBM powder feeding are solved, and the processing efficiency is improved. The powder feeding system is matched with the rotary workbench to work, and continuous and uninterrupted powder feeding work can be realized, so that efficient printing of large-size complex parts is realized. Meanwhile, the powder feeding structure is compact, the occupied space is small, the space of a printing chamber is reduced, and the equipment cost and the vacuumizing time are saved.
As shown in fig. 2 and 3, the powder feeding device 1 of the present invention includes a powder feeding housing 11, a plurality of sets of powder wheel assemblies 12, and a plurality of sets of driving assemblies 13, and for convenience of description of the structure of the powder feeding device, the length direction of the powder feeding housing 11 is set as X direction, the width direction is set as Y direction, and the height direction is set as Z direction. The powder feeding shell 11 is internally provided with a powder feeding cavity 111, the top of the powder feeding shell is provided with at least one powder inlet 112, the powder inlet 112 is communicated with the powder feeding cavity 111, the bottom of the powder feeding shell is provided with a plurality of powder outlet channels 113 communicated with the powder feeding cavity 111 along the X direction, and the number of the powder outlet channels 113 is the same as that of the powder wheel assemblies 12 and the driving assembly 13. A plurality of sets of the powder wheel assemblies 12 are arranged in the powder outlet channel 113, and the driving assembly 13 is used for driving the powder wheel assemblies 12.
As shown in fig. 4, in an embodiment of the present invention, the powder discharging channel 113 may be configured as a structure including a first channel 1131, a second channel 1132 and a third channel 1133 which are sequentially connected from top to bottom (i.e., along the Z direction); the first channel 1131 is a trapezoidal channel, a large end of the first channel is communicated with the powder feeding cavity 111, a small end of the first channel is communicated with the second channel 1132, the second channel 1132 is obliquely arranged along the horizontal direction (namely obliquely arranged with an XY plane), when viewed from an XZ plane, a center line of the second channel 1132 and a center line of the first channel 1131 are arranged at a certain angle, and a center line of the third channel 1133 is parallel to a center line of the first channel 1131. The angle β between the centerline of the second channel 1132 and the centerline of the first channel 1131 is 100 ° to 160 °, and specifically may be 145 °. A powder feeding wheel is arranged in the second channel 1132, the powder feeding wheel is equivalent to a control valve for controlling the powder flow, the powder feeding wheel rotates by 45 degrees to bring the powder from the first channel 1131 to the third channel 1133, and the powder passing amount is calibrated through the rotation speed of the powder feeding wheel.
As shown in fig. 3 and 5, the powder wheel assembly 12 of the present invention is disposed in the powder outlet channel 113, and includes a transmission shaft 121, a powder feeding wheel 122 and two side leakage prevention wheels 123, wherein the transmission shaft 121 is disposed in a second channel 1132 of the powder outlet channel 113, and the axis thereof is parallel to the Y direction; powder feeding wheel 122 and side leakage prevention wheel 123 are sleeved on transmission shaft 121, powder feeding wheel 122 is located between two side leakage prevention wheels 123, a plurality of wheel grooves of powder feeding wheel 122 are uniformly distributed along the circumferential direction of powder feeding wheel 122, a plurality of annular wheel grooves of side leakage prevention wheel 123 are arranged along the axial direction of side leakage prevention wheel 123, and the wheel grooves and the powder feeding wheel 122 are arranged at 90 degrees. The powder feeding wheel 122 is similar to a gear in structure, powder is quantitatively transferred into a lower straight channel through a gear groove on the powder wheel, the powder discharging amount is controlled by the rotating speed of the powder feeding wheel 122, each powder feeding wheel 122 is independently driven by a motor, and the speed of the motor is adjustable and controllable, so that the flexible control of the powder amount is realized, and the accurate powder feeding can be realized.
As shown in fig. 6, the invention has the side leakage prevention wheels 123 arranged on the transmission shaft 121, and the side leakage prevention wheels 123 are arranged on both sides of the powder feeding wheel 122, so as to prevent the powder particles from leaking laterally from the axial direction, and to make the powder feeding amount of the powder paving device accurately controllable, thereby achieving the purpose of accurately controlling the powder feeding amount. Meanwhile, the width of the first channel 1131 is the same as the width of the powder feeding wheel 122, the width of the third channel 1133 is the same as the sum of the widths of the wheel grooves of the powder feeding wheel 122 and the two side leakage prevention wheels 123, that is, the width of the inner cavity of the shell at the upper part of the powder wheel cavity is the same as the width of the powder feeding wheel 122, and the width of the inner cavity at the lower part of the powder wheel cavity contains the side leakage groove, so that the side leakage powder particles have a dredging space, and the powder particles are prevented from being extruded into the side gap to cause the mechanism to be clamped.
In the embodiment of the present invention, the top of the powder feeding housing 11 is provided with two powder inlets 112, the bottom is provided with 110 powder outlets 113, and the upper space of the housing inner cavity is large, which is beneficial for smooth powder entry and fully receives and stores the powder entering from the two powder inlets 112. The powder wheel assembly 12 is arranged in the powder wheel cavity (namely, the second channel 1132) of the powder outlet channel 113, and a through outlet is arranged below the powder wheel cavity. The gap between the powder feeding wheel 122 and the powder wheel cavity is specific, that is, the gap between the powder feeding wheel 122 and the second channel 1132 is larger than the maximum size of the powder particles, so as to meet the requirement that the powder particles can not be blocked and can pass through smoothly.
As shown in fig. 2, the driving assembly 13 of the present invention is disposed outside the powder feeding housing 11, and the output end thereof is connected to the transmission shaft 121 for driving the transmission shaft 121 to rotate. In order to save installation space and make the powder feeding device compact, a plurality of groups of driving assemblies 13 can be arranged on two sides of the powder feeding shell 1 in a staggered mode. At this time, the powder wheel assembly 12 is specifically disposed on the powder feeding housing 11 by the following structure, the driving device adopts a servo motor 131, the transmission shaft 121 is connected with a driving shaft of the servo motor 131 through a coupling 132, and the transmission shaft 121 is disposed on the powder feeding housing 11 through a bearing assembly. The bearing assembly mainly comprises a bearing, a spacer bush, a bearing seat, an end cover, a sealing ring and the like, and power transmission between the driving motor and the transmission shaft 121 is guaranteed. Because the powder falling amount of the powder in the radial direction is different, and the powder falling amount of each section is determined by the rotating speed of the servo motor 131, the rotating speed of each servo motor 131 is respectively controlled in the printing process, so that when smaller parts are printed, the powder feeding motor in the large diameter position can be controlled to stop rotating, the powder feeding is stopped at the excircle position, the powder spreading is directly reduced along the radial direction, and the powder waste is avoided.
As shown in fig. 7, the powder feeding device of the present invention can be applied to an annular spiral powder-spreading manner, in which the powder falls along an annular radial line, and at this time, the annular table rotates and falls, so that the powder spreads on the table along a spiral track. Therefore, the system of the invention adopts a sectional powder falling structure along the radial direction of the circular ring, in order to save powder, powder is not spread in the central diameter of 350mm of the annular powder spreading platform, and the part from the diameter of 350mm to the outermost 1500mm of the circular ring is divided into two groups, and 10 sections of each group are used for powder feeding.
As shown in fig. 8, 9 and 10, the powder spreading device of the present invention includes a powder dropping box 21 and a plurality of powder scraping assemblies 22, wherein the powder scraping assemblies 22 are fixed at the bottom of the powder dropping box 1 through bolts; a plurality of powder falling cavities 211 arranged along the X direction are arranged in the powder falling box 21, and a plurality of scattering plates 212 are arranged in each powder falling cavity 211 and are used for scattering powder falling into the powder falling cavities 211; the top of the powder dropping box 21 is provided with a plurality of powder inlets 213 communicated with the powder dropping cavity 211, and the bottom is provided with powder outlets 214 communicated with the powder dropping cavity 211 and arranged in a row along the x direction; each powder inlet 213 is in one-to-one correspondence communication with the powder outlet channel 113 of the powder feeder 1 (disposed above the device and outside the forming chamber) to receive the metal powder fed by the powder feeder, and a precise amount of the metal powder falls from the powder inlet 213, is uniformly dispersed by the impact of each scattering plate 212, and then uniformly falls from the powder outlet onto the powder bed of the annular workbench. In the embodiment of the present invention, the scattering plates 212 are disposed on the front side plate and the rear side plate of the powder dropping box 21 opposite to each other in the Y direction, and the plurality of scattering plates 212 disposed on the front side plate and the plurality of scattering plates 212 disposed on the rear side plate are arranged in a staggered manner in both the X direction and the Z direction, so that no dead angle scattering is realized for the falling powder, and the metal powder is scattered uniformly. The scattering plate 212 may be a triangular plate, and the inclined side of the triangular plate may scatter the powder falling into the powder falling chamber 211.
As shown in fig. 9 and 10, the powder scraping assembly 22 of the present invention includes a soft scraping plate 221, a hard scraping plate 222, and a compacting plate 223, and the powder outlet 214, the soft scraping plate 221, the hard scraping plate 222, and the compacting plate 223 are arranged in this order in the Y direction; the soft scraper 221 has a comb-shaped structure, and includes a plurality of scrapers 2211 arranged along the X direction; the powder scraping end face of the hard scraper 222 is as high as the powder scraping end face 2212 of the soft scraper 221 in the Z-axis direction; the powder end surface 2231 of the compacting plate 223 is lower than the powder scraping end surface of the hard scraper 222 in the Z-axis direction, i.e. the lowest points of the soft scraper 221 and the hard scraper 222 have the same height, and the difference between the hard scraper 222 and the lowest point of the compacting plate 223 is the compacting amount of the powder. A plurality of partition plates 224 are further provided between the hard blade 222 and the compacting plate 223 such that the soft blade 221, the hard blade 222, and the compacting plate 223 are parallel to and spaced apart from each other.
As shown in fig. 11, the soft scraper 221 is similar to a plate-type comb in structure, the plate thickness is 0.1mm, the comb width is 0.85mm, the comb pitch is 0.15mm, and the soft scraper 221 has the function of pre-pushing the powder uniformly, when the powder resistance is large, individual comb teeth can be bent to release pressure and then rebound to the original shape, and the soft scraper 221 cannot be damaged. After the soft scraper 221 is pre-scraped, the force applied to the hard scraper 222 is relatively reduced, and the hard scraper 222 acts to push the powder.
As shown in fig. 12, the compacting plate 223 only plays a role of compacting powder in the x-axis (i.e., on the radius of the circular ring) but not playing a role of pushing powder, and the powder end surface 2231 of the compacting plate 223 may be configured as an arc-shaped surface, which is designed to have a certain pressing angle and the pressing angle is smoothly transited. The size of the arc-shaped surface is ensured to ensure that the fixation difference between the highest point and the lowest point is larger than the diameter of the powder particles, so that the particles are not scraped.
The soft scraper 221 and the hard scraper 222 of the powder spreading device 23 are parallel to the radius of the rotary worktable and have a certain distance t, the distance enables powder to be effectively and uniformly spread on a powder bed of the rotary worktable, the soft scraper 221 pre-pushes the powder, the stress of the hard scraper 222 is reduced, the soft scraper 221 pushes redundant powder to the edge of the rotary powder bed, finally the powder bed is pushed out, and the compacting plate 223 has a radial side pressing effect on the powder, so that the powder is higher in density. The compacting plate 23 of the powder spreading device 3 is positioned on an X axis, the soft scraper 21 has a certain distance t (the distance is related to the rotating speed of the workbench and the powder spreading area responsible for each powder dropping point and is 40mm in the embodiment of the invention) with the X axis, and the distance t can ensure that the positive thrust of the soft scraper 21 to the powder does not follow the circumferential tangential direction and has a component outward along the radial direction, thereby playing a certain role in uniformly spreading the powder in a local fan-shaped area. Similarly, the hard scraper 22 is also located at a distance from the x-axis (this distance is related to the rotational speed of the table and the powder-spreading area for each powder-dropping point, in the embodiment of the invention, 36 mm) such that the positive thrust of the hard scraper 22 on the powder is not tangential to the circumference, but has a radially outward component, which contributes to the uniform spreading of the powder in the local sectors.
The height position of the powder spreading device in the vacuum chamber is fixed, a lifting device is not needed, and the relative position of the powder spreading device and the rotary worktable 25 is determined by the rotation and the lifting of the worktable 25. Meanwhile, the powder spreading device is simple in structure, a powder feeding cylinder and a powder recovery cylinder are not needed (as the powder feeding in the previous powder feeding process is accurate, no redundant powder needs to be recovered basically), and the space of a vacuum chamber is saved.
As shown in fig. 1, the present invention further provides a large-size electron beam 3d printing apparatus, which mainly comprises an electron gun 3, a printing chamber 4, a workbench unit 5, a powder feeding device 1 and a powder spreading device 2, wherein the electron gun 3 is arranged outside the printing chamber 4 and is used for providing an electron beam for printing, and the workbench unit 5 is arranged in the printing chamber 4 and comprises a workbench and a workbench support driving assembly; the worktable supporting and driving component can drive the worktable to rotate in the plane of the worktable surface, namely the XY plane, and can move along the Z direction. The equipment can realize continuous and fault-free printing and forming of a plurality of large-size parts, and the maximum printing size can reach D1500 multiplied by 1500. The large-size electron beam 3d printing equipment is spiral printing equipment, an annular continuous dynamic powder spreading mode needs to be adopted, if a large amount of powder is placed in a powder box, the weight of the powder can deform a structure for bearing the powder on the upper portion, and the powder falling quality and the forming quality are affected, so that the segmented powder adding mode is adopted. Meanwhile, in the annular powder spreading process, the powder cannot be uniformly spread along the radial direction, so the powder falling uniformity structural design is needed. In the process of spirally spreading the powder, the powder dropping amount in the radial direction of the powder is different, and the powder dropping amount in the direction from the circle center to the outside is gradually increased, so that the powder on the workbench is ensured to be uniform and equal in thickness.
Based on the requirements, the powder feeding system comprises two groups of powder feeding devices 1 and two groups of powder paving devices 2, wherein the two groups of powder feeding devices 1 are respectively arranged above the powder paving devices 2, and powder outlet channels of the powder feeding devices 1 are communicated with powder inlet ports of the powder paving devices 2. Two sets of powder paving devices 2 are respectively arranged on the workbench along the X direction and are symmetrically arranged at the center of the annular workbench, powder passing through the powder feeding device 1 falls into the powder paving devices 2, the powder is paved on the rotary workbench in a manner of sweeping along the circumference by the radius, and after the powder is continuously paved and compacted, continuous printing work is realized through an electron beam scanning area. Each powder feeding device is provided with two inlets and 10 outlets, the 10 outlets are communicated with 10 holes on the vacuum forming box body and respectively correspond to 10 sections in the powder paving subsection, and the powder output of each outlet is independently controlled by a respective motor, so that the powder feeding amount of each area is different.
As shown in fig. 13, 14 and 15, the printing area (also called as the electron beam scanning area) of the large-size electron beam 3d printing apparatus of the present invention has two positions, which are respectively located on two radii of the y-axis of the ring-shaped stage and are symmetrically arranged along the x-axis. In fig. 13, a plane a is a print horizontal plane and a plane B is a table surface. The lower surface (surface B) of the follow-up powder cylinder 8 is seated on the table surface of the workbench. The workbench can move up and down along the guide rail on the upright post of the sliding table through a screw rod mechanism, and the lower part of the sliding table is connected with an electric horizontal moving mechanism which can move the sliding table horizontally. The ring worktable can rotate around the center of the ring through the electric slewing device. Be provided with the electric stove of preheating in the above-mentioned workstation, preheat the electric stove and can preheat the powder, make the powder of laying compaction reduce mobility, produce the blowing phenomenon when avoiding printing. The soft scraper 21, the hard scraper 22 and the compacting plate 23 are sequentially arranged on the side surface of the powder outlet 14 and descend along with the rotation of the workbench, so that the powder on the upper surface of the powder cylinder 8 is continuously and spirally spread and compacted.
The specific working process for the large-size electron beam 3d printing equipment provided by the invention is as follows:
1) The equipment returns to zero, and simultaneously the automatic powder feeding device, the rotary workbench and the electric furnace in the workbench are started, the automatic powder feeding device quantitatively feeds powder to the powder paving device (positioned on an x axis), and the powder paving device drops the powder to the workbench to pave the powder uniformly and compact the powder; opening a high-power electronic gun (the maximum power reaches 3 KW), melting powder in the cross section of the model under scanning according to a scanning path input by a computer, solidifying and depositing the powder to form a part cross section and simultaneously forming a follow-up powder cylinder 8 cross section;
2) When the workbench rotates for a circle from the 0 position, the workbench is lowered by one layer thickness under the action of the electric lifting mechanism;
3) Performing second-layer spiral powder laying printing;
4) And (3) repeating the steps 1), 2) and 3) until the workpiece 7 and the follow-up powder cylinder 8 are completed, and adjusting the height difference of the soft scraper 21, the hard scraper 22 and the compacting plate 23 according to different kinds of powder in actual operation.
Claims (9)
1. A powder feeding system for large-size electron beam 3d printing is characterized in that: comprises a powder feeding device (1) and a powder spreading device (2);
the powder feeding device (1) comprises a powder feeding shell (11), a plurality of groups of powder wheel assemblies (12) and a plurality of groups of driving assemblies (13), wherein the length direction of the powder feeding shell (11) is set to be the X direction, the width direction is the Y direction, and the height direction is the Z direction;
a powder feeding cavity (111) is arranged in the powder feeding shell (11), at least one powder inlet (112) is formed in the top of the powder feeding shell, the powder inlet (112) is communicated with the powder feeding cavity (111), a plurality of powder outlet channels (113) communicated with the powder feeding cavity (111) are formed in the bottom of the powder feeding shell along the X direction, and the number of the powder outlet channels (113) is the same as that of the powder wheel assemblies (12) and the driving assemblies (13);
the powder wheel assembly (12) comprises a transmission shaft (121), a powder feeding wheel (122) and two side leakage prevention wheels (123), wherein the transmission shaft (121) is arranged in the powder outlet channel (113), and the axis of the transmission shaft is parallel to the Y direction; the powder feeding wheel (122) and the side leakage prevention wheel (123) are sleeved on the transmission shaft (121), the powder feeding wheel (122) is positioned between the two side leakage prevention wheels (123), a plurality of wheel grooves of the powder feeding wheel (122) are uniformly distributed along the circumferential direction of the powder feeding wheel (122), a plurality of annular wheel grooves of the side leakage prevention wheel (123) are arranged along the axial direction of the side leakage prevention wheel (123) and are arranged at an angle of 90 degrees with the wheel grooves of the powder feeding wheel (122);
the driving assembly (13) is arranged outside the powder feeding shell (11), and the output end of the driving assembly is connected with the transmission shaft (121) and used for driving the transmission shaft (121) to rotate;
the powder spreading device (2) is arranged below the powder feeding device (1) and comprises powder falling boxes (21) and powder scraping assemblies (22), wherein the powder scraping assemblies (22) are arranged in multiple groups and are all arranged at the bottoms of the powder falling boxes (21);
a plurality of powder falling cavities (211) which are arranged along the X direction are arranged in the powder falling box (21), and a plurality of scattering plates (212) are arranged in the powder falling cavities (211) and are used for scattering powder falling into the powder falling cavities (211); the top of the powder falling box (21) is provided with a plurality of powder inlets (213) communicated with the powder falling cavity (211), the powder inlets (213) are communicated with the powder outlet channels (113) of the powder feeding shell (11) in a one-to-one correspondence manner, and the bottom of the powder falling box is provided with a plurality of powder outlet (214) communicated with the powder falling cavity (211);
the powder scraping assembly (22) comprises a soft scraping plate (221), a hard scraping plate (222) and a compacting plate (223), and the powder outlet (214), the soft scraping plate (221), the hard scraping plate (222) and the compacting plate (223) are sequentially arranged along the Y direction; the soft scraper (221) is of a comb-tooth-shaped structure and comprises a plurality of scraping strips (2211) arranged along the X direction; the powder scraping end face of the hard scraper blade (222) and the powder scraping end face (2212) of the soft scraper blade (221) have the same height in the Z direction; the powder pressing end surface (2231) of the compacting plate (223) is lower than the powder scraping end surface of the hard scraping plate (222) in the Z direction; the powder outlet channel (113) comprises a first channel (1131), a second channel (1132) and a third channel (1133) which are sequentially communicated along the Z direction; the powder feeding device is characterized in that the first channel (1131) is a trapezoidal channel, the large end of the first channel is communicated with the powder feeding cavity (111), the small end of the first channel is communicated with the second channel (1132), the second channel (1132) is obliquely arranged with the XY plane, the central line of the second channel (1132) and the central line of the first channel (1131) are arranged at a certain angle when seen from the XZ plane, and the central line of the third channel (1133) is parallel to the central line of the first channel (1131).
2. The powder feed system for large-size electron beam 3d printing according to claim 1, wherein: powder wheel subassembly (12) set up in second passageway (1132), and send the clearance of powder wheel (122) and second passageway (1132) to be greater than the maximum size of powder granule for the powder granule can pass through smoothly.
3. The powder feed system for large-size electron beam 3d printing according to claim 2, wherein: the angle between the central line of the second channel (1132) and the central line of the first channel (1131) is 100-160 degrees.
4. The powder feed system for large-size electron beam 3d printing according to claim 3, wherein: the width of the small end of the first channel (1131) is the same as that of the powder feeding wheel (122), and the width of the third channel (1133) is the same as the sum of the widths of the powder feeding wheel (122) and the wheel grooves of the two side leakage prevention wheels (123).
5. The powder feed system for large-size electron beam 3d printing according to any one of claims 1 to 4, wherein: the powder feeding device is characterized in that multiple groups of driving assemblies (13) are arranged on two sides of the powder feeding shell (11) in a staggered mode, each driving assembly (13) comprises a servo motor (131), the transmission shaft (121) is connected with a driving shaft of the servo motor (131) through a coupler (132), and the transmission shaft (121) is arranged on the powder feeding shell (11) through a bearing assembly.
6. The powder feed system for large-size electron beam 3d printing according to claim 5, wherein: the scattering plates (212) are arranged on the front side plate and the rear side plate of the powder falling box (21) opposite to each other in the Y direction, and the scattering plates (212) arranged on the front side plate and the scattering plates (212) arranged on the rear side plate are arranged in a staggered mode in the X direction and the Z direction.
7. The powder feed system for large-size electron beam 3d printing according to claim 6, wherein: the scattering plate (212) is a triangular flat plate, and the inclined side edge of the triangular flat plate is used for scattering powder falling into the powder falling cavity (211).
8. The powder feed system for large-size electron beam 3d printing according to claim 7, wherein: the powder pressing end surface (2231) of the compacting plate (223) is an arc-shaped surface.
9. The powder feed system for large-size electron beam 3d printing according to claim 8, wherein: and a plurality of partition plates (224) are arranged between the hard scraper (222) and the compacting plate (223).
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| CN105436501B (en) * | 2016-01-08 | 2017-10-03 | 江苏永年激光成形技术有限公司 | SLM band compacting functions scraper plates |
| CN111163881B (en) * | 2017-10-06 | 2022-04-05 | 株式会社Ihi | Powder supply device and three-dimensional lamination molding device |
| JP2020536768A (en) * | 2017-10-10 | 2020-12-17 | アプライド マテリアルズ インコーポレイテッドＡｐｐｌｉｅｄ Ｍａｔｅｒｉａｌｓ，Ｉｎｃｏｒｐｏｒａｔｅｄ | Selective powder supply for additive manufacturing |
| CN108215176A (en) * | 2018-01-30 | 2018-06-29 | 华侨大学 | It is a kind of to scrape compound power spreading device suitable for selective laser sintering |
| US10828832B2 (en) * | 2018-09-28 | 2020-11-10 | The Boeing Company | Powder dispensing unit, powder spreading unit, and a vibratory compaction system of an additive manufacturing system and methods therefor |
| US11065815B2 (en) * | 2018-12-18 | 2021-07-20 | General Electric Company | Powder dispensing assembly for an additive manufacturing machine |
| CN210132767U (en) * | 2019-03-27 | 2020-03-10 | 苏州西帝摩三维打印科技有限公司 | Powder laying device for additive manufacturing equipment |
| CN210545573U (en) * | 2019-08-09 | 2020-05-19 | 安徽金星钛白（集团）有限公司 | Titanium white powder outlet device with break up structure |
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