CN109604596B - Additive manufacturing dynamic powder laying system - Google Patents

Additive manufacturing dynamic powder laying system Download PDF

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Publication number
CN109604596B
CN109604596B CN201811563473.7A CN201811563473A CN109604596B CN 109604596 B CN109604596 B CN 109604596B CN 201811563473 A CN201811563473 A CN 201811563473A CN 109604596 B CN109604596 B CN 109604596B
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powder
local
protective cover
bed protective
powder bed
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CN109604596A (en
Inventor
卢秉恒
陈祯
张丽娟
魏培
张树哲
邹亚桐
王博文
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National Institute Corp of Additive Manufacturing Xian
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National Institute Corp of Additive Manufacturing Xian
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER
    • B22F12/00Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER
    • B22F10/00Additive manufacturing of workpieces or articles from metallic powder
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER
    • B22F10/00Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/10Formation of a green body
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B22CASTING; POWDER METALLURGY
    • B22FWORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER
    • B22F10/00Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/20Direct sintering or melting
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B33ADDITIVE MANUFACTURING TECHNOLOGY
    • B33YADDITIVE 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
    • B33Y30/00Apparatus for additive manufacturing; Details thereof or accessories therefor
    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02PCLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00Technologies related to metal processing
    • Y02P10/25Process efficiency

Abstract

The invention provides an additive manufacturing dynamic powder laying system, which can realize the miniaturization of a powder feeding and laying device and can realize the quantitative supply of powder according to requirements. The additive manufacturing dynamic powder laying system comprises a powder cylinder, a powder feeding pipeline, a powder laying device, a local powder bed protective cover and a guide movement mechanism; the cross section outline of the powder cylinder is matched with the maximum cross section outline size of a part to be formed, and a powder laying area is formed between the first side wall and the second side wall of the powder cylinder; the lower end face of the local powder bed protective cover is hollow, and the width of the local powder bed protective cover is larger than the distance between the first side wall and the second side wall; a buffer bin of the powder spreading device is fixed on the front side surface of the local powder bed protective cover and is close to the lower end surface; and the guide movement mechanism is used for driving the local powder bed protective cover and the powder spreading device to synchronously run to the next local powder spreading area according to a preset track after the corresponding local powder spreading at the local powder bed protective cover and the laser processing of the local powder spreading area are completed according to a process instruction.

Description

Additive manufacturing dynamic powder laying system
Technical Field
The invention belongs to the technical field of additive manufacturing, and relates to a powder laying system required by an additive manufacturing process, which is particularly suitable for processing large-size complex components.
Background
Additive Manufacturing (AM), also called "3D printing", is a method of performing accumulated manufacturing point by point on a two-dimensional section by a three-dimensional entity by reducing the manufacturing order of a three-dimensional entity into two-dimensional sections on the basis of digital CAD model data by using a superposition method manufacturing principle similar to mathematical integration, thereby realizing dimension-reduced forming of a three-dimensional part, being not limited by the complexity of the shape, and being capable of realizing rapid, high-quality, efficient, economical, fully-intelligent and fully-flexible manufacturing of parts with arbitrary complex shapes. The additive manufacturing is an important component of the advanced manufacturing industry, is a high-end digital manufacturing technology which is rapidly developed in the last three decades, is a manufacturing method for material accumulation forming from bottom to top relative to the traditional equal material manufacturing (casting, forging and the like with the delta M being 0 in the manufacturing process) and the material reduction manufacturing (the delta M being 0, turning, milling, grinding and drilling and the like), embodies the close combination of the information network technology, the advanced material technology and the digital manufacturing technology, realizes the important transition of the manufacturing mode from equal material, material reduction to additive manufacturing, and changes the concept and mode of the traditional manufacturing.
Metal additive manufacturing is the leading and most potential additive manufacturing technology and is an important development direction of advanced manufacturing technology. Selective Laser Melting (SLM) and near Net Shaping (LENS) Laser techniques in metal additive manufacturing have been rapidly developed in recent years. The SLM process can form any complex metal part because the powder can be self-supporting, but the formable part size is small (typically less than 500 mm). The LENS process has large spot diameter and can form large-scale components, but the precision of the formed components is low, and the complicated metal components are difficult to form directly. The Fused Deposition Modeling (FDM) is one of the most developed mature non-metal additive manufacturing technologies, and has the greatest characteristics of low cost, high efficiency, low precision, relatively low forming speed and unsuitability for constructing large-size complex parts.
The manufacturing of large-size metal components is a technical bottleneck which is difficult to break through in the SLM technology for a long time, because the technological characteristics of SLM layer-by-layer accumulative powder spreading determine that the size of a forming cylinder body is necessarily larger than the section size of a formed part, and no matter how large the formed part is, powder is spread layer-by-layer laser scanning forming is needed. At present, units such as German EOS, Fraunhofer research institute, SLM Solution, Concept laser and the like, China university of science and technology, Suzhou Xidi Mo and the like, sequentially develop SLM equipment with the forming size of 500mm or slightly larger by adopting a multi-beam splicing mode, but the size is not reasonable for parts with larger sizes.
The traditional upper powder falling and lower powder feeding type structural design needs to store a large amount of powder, determines that the size of the powder feeding and spreading device is larger, not only increases the power consumption, but also avoids waste.
Disclosure of Invention
The invention aims to solve the problems that a powder paving system needs to store a large amount of powder in the existing additive manufacturing process, so that the device is large in size and the like, and provides a dynamic powder paving system for additive manufacturing, which can realize the miniaturization of a powder feeding and powder paving device and the quantitative supply of powder according to requirements.
The technical scheme of the invention is as follows:
this vibration material disk developments shop powder system, including powder jar, send powder pipeline and shop's powder device, it is different from prior art: the powder bed protective cover and the guide movement mechanism are arranged on the outer side of the powder bed;
the cross section outline of the powder cylinder is matched with the maximum cross section outline size of a part to be formed; the two side walls of the powder recording cylinder are respectively a first side wall and a second side wall corresponding to the two sides of the section of the part to be formed; the first side wall and the second side wall are finally closed in the horizontal direction to form the cross section profile of the powder cylinder; a powder spreading area is formed between the first side wall and the second side wall of the powder cylinder;
the lower end face of the local powder bed protective cover is hollow, and the width of the local powder bed protective cover is larger than the distance between the first side wall and the second side wall, so that the local powder bed protective cover can be directly erected on the upper surfaces of the first side wall and the second side wall of the powder cylinder;
the powder spreading device comprises a buffer bin and a scraper, the buffer bin is fixed on the front side surface of the local powder bed protective cover and is close to the lower end surface, the powder feeding pipeline is introduced into the buffer bin, the lower end of the buffer bin is provided with a powder outlet corresponding to the powder spreading area, the scraper is fixed on the lower portion of the buffer bin, the working surface of the scraper is flush with the lower end surface (equivalent to the upper surface of the powder cylinder) of the local powder bed protective cover or slightly lower than the lower end surface (slightly lower than the upper surface of the powder cylinder) of the local powder bed protective cover, equivalent to the fact that the powder bed formed by powder spreading is slightly lower than the upper surface of the powder cylinder, and partial powder can be prevented from being swept;
and the guide movement mechanism is used for driving the local powder bed protective cover and the powder spreading device to synchronously run to the next local powder spreading area according to a preset track after the corresponding local powder spreading at the local powder bed protective cover and the laser processing of the local powder spreading area are completed according to a process instruction.
Based on the above scheme, the invention further optimizes as follows:
the guide motion mechanisms are provided with precise grating rulers in three-dimensional directions, and closed-loop feedback is provided for guide motion so as to ensure the positioning precision and the repeated positioning precision of operation.
In order to better adapt to the section shape of the powder cylinder determined by the contour of a complex part, scrapers with various sizes can be arranged, and the scrapers are detachably arranged and fixed at the lower part of the buffer bin.
And a powder recovery device is also arranged at the periphery of the powder cylinder and used for sucking the unfused powder away in time.
For laser printing, a light-passing area corresponding to the upper laser printing optical path system can be arranged on the upper end face of the partial powder bed protective cover.
The special local atmosphere protection can be performed in the local powder bed protective cover, the upper parts of the front side and the rear side of the local powder bed protective cover are provided with an air inlet pipe and an air outlet pipe, the air inlet pipe is used for introducing inert gas into a powder spreading area in the local powder bed protective cover, and the air inlet pipe and the air outlet pipe form a circulating pipeline.
Furthermore, the inner walls of the front side and the rear side of the local powder bed protective cover are respectively provided with a coanda cavity, the air inlets of the coanda cavities are correspondingly arranged at the upper parts of the front side surface and the rear side surface of the local powder bed protective cover, and the air guide slits are positioned on the lower end surface of the local powder bed protective cover; the area between the front coanda cavity and the rear coanda cavity is a powder spreading area in the local powder bed protective cover; the coanda cavity is spaced from the outer edges of the first and second sidewalls to leave a flue gas flow passage.
The top of the local powder bed protective cover can also be provided with an air blowing inclined hole for introducing inert gas.
The left side and the right side of the lower part of the local powder bed protective cover are provided with channels for discharging smoke dust.
Furthermore, the channel for discharging the smoke dust is specifically a porous air inlet and a porous air outlet which are respectively arranged on the left side surface and the right side surface of the lower part of the local powder bed protective cover, wherein the porous air inlet is used for introducing inert gas, and the porous air outlet is connected with an air extraction device so as to discharge the smoke dust by utilizing negative pressure.
The above "front", "rear", "left" and "right" are for distinguishing relative orientations, and the traveling direction of the laser printing optical path system and the partial powder bed protective cover in actual operation is taken as "front", thereby giving the above relative orientations.
The invention has the following beneficial effects:
1. by designing the powder cylinder matched with the interface contour size of a required forming part, a powder spreading area is formed between the first side wall and the second side wall of the powder cylinder, the local powder bed protective cover is directly erected on the upper surfaces of the first side wall and the second side wall of the powder cylinder, and powder is dynamically spread along the track determined by the powder cylinder for printing, so that the miniaturization of a powder feeding and spreading device is realized, the powder consumption is greatly saved, and the size limit of manufacturing large-size complex parts by using an SLM (selective laser melting) is broken through.
2. The synchronous powder feeding and spreading is realized. After the powder is partially paved, the powder is formed on the surface of a local powder bed in time, redundant powder is not required to be recycled in the powder paving process, the powder can be paved continuously and in a follow-up mode, the traditional structural design of an upward powder falling mode and a downward powder conveying mode is broken through, a large amount of powder is not required to be stored in the powder paving process, the powder can be conveyed through the real-time external part, the structure of the powder conveying and powder paving device is greatly simplified, the operation power consumption is reduced, and meanwhile, the powder can be recycled. And continuously conveying the metal powder required by forming to a local powder paving area according to the powder paving amount, and quantitatively supplying according to the requirement.
3. The forming of the powder cylinder has low requirements on process precision, can be realized by adopting various technologies (such as CMT, LENS, FDM and the like), and fully exerts the advantages of various additive manufacturing technologies.
4. The local gas protection is designed on the local powder bed protective cover, so that a large-scale closed chamber can be prevented from being additionally arranged, Ar consumed in the forming process is saved to a certain extent, and the cost is saved. Particularly, the coanda cavity is adopted, and gas (argon or air) is introduced into the coanda cavity, so that negative pressure is generated in the process of guiding the gas along the surface of the coanda, on one hand, smoke and dust generated inside the local powder bed protective cover are quickly sucked away, and on the other hand, because an inert 'air curtain' is formed under the action of the coanda guide plate, surrounding air cannot enter the local powder bed protective cover, and the atmosphere protection effect on the forming process is also realized.
5. By arranging the air blowing inclined holes around the light passing area of the glass at the top of the local powder bed protective cover, the inert protective gas can generate vortex in the process of entering the local powder bed protective cover through the air blowing inclined holes, so that the smoke dust generated in the SLM forming process is prevented from being deposited on the light passing glass (shielding laser light); meanwhile, the air flow formed by the air blowing inclined hole does not face the surface of the powder bed, so that the powder spreading process and the powder bed are not influenced.
6. The mode of a dynamic powder cylinder can also be adopted, namely the powder cylinders are printed and formed layer by layer, local powder paving and printing are sequentially carried out on a plurality of areas along the track determined by the powder cylinders on the basis of each layer of powder cylinder, all areas of one layer are finished to obtain part slices, the part slices are obtained until the last layer of powder cylinder and the corresponding part slices, and the whole part is finally obtained.
7. The invention can be applied to SLM process forming parts and other additive manufacturing processes related to powder laying.
8. The invention has remarkable advantages especially when the parts with large length-width ratio (including annular, long-strip-shaped, irregular bent parts and the like) are manufactured in an additive mode.
Drawings
Fig. 1 is a schematic diagram of the operation of one embodiment of the present invention.
Fig. 2 is a simplified schematic diagram of the main equipment involved in laser printing and forming.
Fig. 3 is a partial cross-sectional detail view based on fig. 2.
Fig. 4 is a schematic view of a section of a coanda cavity.
Fig. 5 is a schematic diagram of the present invention using a coanda cavity.
FIG. 6 is a schematic diagram of a multi-energy field (FDM, SLM and milling process) system architecture apparatus designed according to the present invention.
Fig. 7 is a Y-direction side view of fig. 6.
Fig. 8 is a top view of fig. 6.
The reference numbers illustrate:
1-a rotary table; a 2-X direction horizontal guide rail system (a lead screw guide rail translation table); a 3-Y direction horizontal guide rail system; a 4-Z direction lifting guide rail system; 5-laser printing optical path system; a 6-FDM printing system; 7-milling and material reducing processing system; 8-local powder bed protective cover; 9. a powder spreading and feeding device; 10-powder jar; 11-a shaped part; 12-powder;
101-a first side wall; 102-a second sidewall;
501-galvanometer; 502-f-theta field lens; 503-QBH joint and collimation and beam expansion module;
801-clear glass; 802-porous air intake at the lower part; 803-porous gas outlets in the lower part; 804-an air inlet pipe located at the upper part; 805-an outlet duct located at the upper part; 806-air-blowing inclined holes; 807-coanda cavity; 8071-coanda cavity air directing slit;
901-powder feeding pipeline; 902-a surge bin; 903-scraper.
Detailed Description
As shown in fig. 1, the powder cylinder is composed of a first side wall and a second side wall, the overall shape and size of which are determined according to the external shape characteristics of the part to be processed, and the size of the powder cylinder is slightly larger than the maximum cross-sectional size of the part to be formed (the first side wall and the second side wall and the forming base plate as the bottom surface constitute a part forming area).
As shown in fig. 1 and 3, the local powder bed protective cover is provided with a local powder spreading device at the bottom along the circumferential direction of the powder cylinder, and the bottom of the local powder bed protective cover is provided with a scraper which is a flexible scraper or a hard scraper. The scraper is positioned between the first side wall and the second side wall of the powder cylinder and can be slightly lower than the lower end surface of the local powder bed protective cover (a certain gap is reserved between the first side wall and the second side wall to prevent scraping). The doctor blade can be replaced during operation. The local powder spreading device can be connected with the powder feeding device through a powder feeding pipeline, the powder feeding device continuously conveys powder required by forming into the local powder spreading device according to the powder spreading amount, and the powder is quantitatively supplied according to needs, so that the problem of large-scale storage of traditional powder is solved, and the movement and power consumption caused by the fact that the local powder spreading device drives a large amount of powder to move are also avoided; the laser printing light path system drives the local powder bed protective cover and the local powder spreading device to move along the movement process of the horizontal guide rail system, the operation of the rotary workbench is matched, the powder can be spread on the surface of the powder cylinder by the local powder spreading device according to the cross section contour track direction of the powder cylinder, the movement track of the local powder spreading device is consistent with the cross section contour appearance of the powder cylinder (the local powder spreading device is always positioned between the first side wall and the second side wall of the upper surface of the powder cylinder in the movement process), redundant powder cannot overflow out of the powder cylinder, meanwhile, the local powder spreading device continuously moves according to the cross section contour track of the powder cylinder along the surface of the powder cylinder, the process that the redundant powder needs to be recovered in the traditional SLM powder spreading process is saved, and the structure is simplified.
Taking laser printing forming as an example, as shown in fig. 2 and 3, in order to keep the powder spreading and laser printing forming processes in an inert atmosphere protection environment all the time, a local powder bed protective cover is fixedly arranged below a laser printing light path system and synchronously moves along with the powder spreading and the laser printing. A glass light through hole is formed above the local powder bed protective cover, quartz glass is installed on the glass light through hole, smooth light through of 1064nm laser can be guaranteed through the quartz glass, and the quartz glass and the local powder bed protective cover are completely sealed.
As shown in fig. 2, 3 and 5, a coanda cavity may be respectively disposed on the front and rear inner walls of the local powder bed protective cover, and a gas (not shown with a gas inlet) introduced into the coanda cavity from the upper portion is pressed along the gas guide surface at the bottom of the coanda cavity to form a gas curtain along the first and second side wall surfaces of the powder cylinder, so as to prevent the air in the surrounding environment from entering the local powder bed protective cover and oxidizing the SLM-formed high-temperature powder; meanwhile, the dust generated in the local powder bed protective cover is guided to be quickly discharged due to the coanda effect. It should be noted that the coanda chambers shown in fig. 4 and 5 are only schematic (for simplicity of the operation), and the actual product can be matched according to the sizes of the sections of the partial powder bed protective cover and the powder cylinder.
The upper parts of the front side and the rear side of the local powder bed protective cover are provided with an air inlet pipe and an air outlet pipe, the air inlet pipe penetrates through the coanda cavity and is communicated with the powder spreading area, and the air inlet pipe is used for introducing inert gas and forms a circulating pipeline with the air outlet pipe.
Since the density of the inert gas (usually argon) is higher than that of air, the air in the local powder bed protective cover is compressed to the bottom of the local powder bed protective cover, one part of the air is exhausted to the outside of the local powder bed protective cover through the air exhausting devices on two sides of the local powder bed protective cover in the radial direction, and the other part of the air flows to the coanda air guide surfaces on the bottoms of the coanda cavities on two sides due to the negative pressure effect of the coanda effect and is exhausted to the outside of the local powder bed protective cover. The air pressure balance and the lower oxygen content in the local powder bed protective cover are realized by adjusting the inert gas entering through the air blowing inclined hole, the inert gas circulating through the air inlet pipe and the air outlet pipe on the upper part of the local powder bed protective cover, the inert gas circulating through the air inlet and the air outlet on the lower part of the local powder bed protective cover and the gas flow and pressure introduced into the coanda cavity, so that a stable inert gas protection environment is provided for the SLM forming process, and the powder is prevented from being oxidized in the forming process.
In addition, it is also possible to provide the rotary table directly with a closed chamber that provides an inert atmosphere (or even to place the entire apparatus in the closed chamber).
A porous air inlet and a porous air outlet (which can form a circulating air path) are respectively arranged on two sides of the local powder bed protective cover close to the bottom in the radial direction of the powder cylinder, so that smoke produced in the SLM forming process can be timely removed, and the balance of pressure and air flow in the local powder bed protective cover is ensured.
The periphery of the glass light through hole is provided with an air blowing inclined hole, the air blowing inclined hole is positioned on a flange plate for fixing the light through glass, and the flange plate is fixed on the local powder bed protective cover for positioning and ensuring sealing. Argon enters the local powder bed protective cover through the air blowing inclined holes around the glass light through holes, an inert atmosphere environment is formed in the local powder bed protective cover, and powder is prevented from being oxidized at high temperature in the laser SLM forming process. The inclination angle of the air blowing inclined hole is preferably 5-25 degrees, on one hand, the inert protective gas can generate vortex flow in the process of entering the local powder bed protective cover through the air blowing inclined hole, so that the dust generated in the SLM forming process is prevented from depositing on the glass light through hole, and the laser is prevented from being shielded; on the other hand, the air blowing inclined holes with the inclination angle of 5-25 degrees are adopted, so that the adverse effects of airflow on the powder bed surface on the powder spreading process and the powder bed can be avoided.
The invention is explained in more detail below with reference to a preferred application example (dynamic powder jar).
The specific working process of the invention is as follows:
1) firstly, designing a three-dimensional model of a large-size annular part to be processed, carrying out data processing, generating an SLM forming process file comprising a section, a support, a scanning path, process parameters, a scanning strategy and the like, importing information such as process file data, equipment parameters, material parameters and the like into process numerical simulation software, carrying out numerical simulation on the whole forming process, obtaining results such as deformation, stress buckling deformation and the like in the forming process, generating an inverse deformation prediction model of the SLM forming process by adding stress deformation prevention, heat conduction auxiliary support and support structure optimization, and regenerating the SLM forming process file for the obtained inverse deformation prediction model; meanwhile, according to the interface contour shape of the large part to be formed, a three-dimensional model of the dynamic powder cylinder is designed, and an FDM forming process file comprising slicing, supporting, scanning paths, process parameters, scanning strategies and the like is generated; and simultaneously importing the optimized SLM forming process file and the optimized FDM forming process file data into SLM forming equipment to prepare for printing.
2) And the formed substrate is arranged on a rotary worktable for leveling, the surface is ensured to be flat, and the error of the flatness is less than 20 mu m. Printing a first side wall and a second side wall of an initial dynamic powder cylinder by adopting an FDM (frequency division multiplexing) process, installing a local powder bed protective cover and a powder spreading device, adjusting the position between a scraper and the powder cylinder, and sealing; continuously conveying metal powder required by SLM forming into a local powder paving device through a synchronous powder feeding device according to the powder paving amount, and quantitatively supplying according to the requirement; the powder paving device is used for locally paving powder between a first side wall and a second side wall of the dynamic powder cylinder according to the cross section profile shape of the dynamic powder cylinder of the large part to be processed and the cross section profile track of the dynamic powder cylinder (paving powder in the local powder bed protective cover area); then stopping the movement of the powder spreading device and the local powder bed protective cover, starting a laser printing light path system, and selectively melting the powder on the surface of the powder bed according to a pre-introduced process file scanning track and process parameters; the powder in the scanning area is in the inert gas protection environment in the whole forming process, and the internal gas pressure balance and the lower oxygen content of the local protection gas device are maintained. After scanning of a coverage area below the local powder bed protective cover is completed, the local powder bed protective cover and the powder spreading device continue to move and spread powder according to the outline track of the section of the dynamic powder cylinder, scanning and printing are performed when one area is spread, then moving, spreading powder, scanning and printing are performed, and the operation is repeated until the scanning of the whole layer of the dynamic powder cylinder area is completed, and the powder spreading device and the local powder bed protective cover integrally move upwards for a distance of a powder spreading layer thickness along the guide column.
3) After the first layer is formed, the milling and material reducing processing system performs finish machining on the side face of the part formed by the SLM, and simultaneously performs milling processing on the upper surfaces of the first side wall and the second side wall of the dynamic powder cylinder formed by the FDM, so that the surface is smooth, and the smooth and uniform powder laying for the second time is ensured; and then printing a second layer of powder cylinder is started, and the related operation of the step 2) is repeated until the integral part is formed.
4) After the whole part is formed, the gas circulation system is closed, the powder circulation recovery system is started, redundant powder in the dynamic powder cylinder is automatically cleaned, sieved and circulated, and finally the part is cut off from the substrate by utilizing linear cutting to complete the machining process of the whole part.
In the laser scanning and printing process, the technology of adjusting the large and small light spots can be adopted, the large light spot can be used for scanning and preheating, the small light spot can be used for focusing and forming, the large light spot can also be used for filling and scanning, the small light spot can be used for scanning the outline, and the SLM forming efficiency and precision can be improved; the real-time online preheating-scanning-heat treatment of the formed part is realized by matching the large light spot and the small light spot; by regulating and controlling the scanning process parameters and scanning strategies of different scanning areas and different powder layers, the residual stress and stress deformation in the forming process are greatly reduced.
The dynamic powder cylinder can be formed in various ways, and the following describes configurable related hardware equipment by taking FDM printing of dynamic powder cylinder + SLM printing of formed parts as an example. As shown in fig. 6, 7, and 8, the infrastructure includes a rotary table, an X-direction horizontal guide rail system (a lead screw guide rail translation table), a Y-direction horizontal guide rail system, a Z-direction lifting guide rail system, a laser printing optical path system, an FDM printing system, and a milling material reduction processing system.
The rotary worktable is arranged on the lead screw guide rail translation table, can move left and right (X direction) along the lead screw guide rail translation table, and can rotate at any angle within the range of 360 degrees.
The lead screw guide rail translation platform is provided with lifting guide rail systems (Z direction) on two sides, the lifting guide rail systems are provided with a plurality of sets of horizontal guide rail systems (Y direction), and the horizontal guide rail systems in the Y direction are provided with a plurality of sets of FDM printing systems, milling material reduction processing systems and a plurality of sets of laser printing light path systems.
The multiple sets of horizontal guide rail systems drive the multiple sets of FDM printing systems, the milling material reduction processing system and the multiple sets of laser printing optical path systems, and the whole system can move up and down along the lifting guide rail system.
And precise grating rulers are arranged on the X-direction horizontal guide rail system, the multiple sets of Z-direction lifting guide rail systems and the multiple sets of Y-direction horizontal guide rail systems, so that closed-loop feedback is provided for movement, and the running positioning precision and repeated positioning precision of the system are ensured.
The FDM printing system is used for printing a follow-up beating dynamic powder cylinder corresponding to a part needing to be formed on a rotary worktable in the forming process. The milling material reduction processing system is used for milling the upper surfaces of the first side wall and the second side wall of the dynamic powder cylinder of the FDM printing system, so that the surface of the dynamic powder cylinder is smooth and flat, and scraper powder spreading in the SLM forming process is facilitated; the milling material cutting processing system can also finish the surface of a part formed by the SLM of the laser printing light path system, so that the surface quality is improved; milling and reducing a material processing system and an FDM printing system, wherein the milling and reducing material processing system and the FDM printing system are installed on the same horizontal guide rail system, and the milling and reducing material processing system is installed at the rear position of the FDM printing system, so that milling processing can be timely performed on the upper surface of the dynamic powder cylinder after FDM printing is facilitated.
The FDM printing system and the milling material-reducing processing system can move up and down along the lifting guide rail system so as to adjust the distances of the upper surfaces of the rest dynamic powder cylinders in the processes of printing and milling the dynamic powder cylinders and ensure the printing precision and the cutting precision; FDM printing system and mill cut material and install on horizontal guide rail system, can install many sets to improve the efficiency of printing dynamic powder jar and milling dynamic powder jar. The milling cutter of the milling material cutting processing system can be arranged to rotate outwards along the surface of the dynamic powder cylinder, so that cutting generated in the processing process can be discharged outwards in time without influencing the forming process of the SLM.
A plurality of sets of laser printing light path systems are installed on the horizontal guide rail system, as shown in fig. 3, each laser printing light path system consists of a QBH joint, a collimation and beam expansion module, a galvanometer and an f-theta field lens/dynamic focusing lens, and is connected with a laser through an optical fiber, and the laser printing light path system is used for realizing the track scanning of the SLM forming process on the surface of the powder bed; the laser printing light path system can run along the front and back (Y direction) of the horizontal guide rail system, and a precise grating ruler is arranged along the horizontal guide rail system, so that the positioning precision and the repeated positioning precision of the movement of the laser printing light path system are ensured; the laser printing light path system is integrally sealed in the optical system protective cover, so that the smoke dust and metal powder metal generated in the forming process are prevented from entering the laser light path system, and the adverse effect on the transmission of laser is avoided.
In the SLM forming process of the part, through the movement of an FDM printing system and a rotary worktable which are arranged on a horizontal guide rail system (Y direction), the FDM printing system prints a first side wall and a second side wall of a dynamic powder cylinder on the rotary worktable according to the profile cross section shape of the part to be processed; the milling material cutting system mills and smoothes the upper surfaces of the first side wall and the second side wall of the dynamic powder cylinder, so that a powder laying plane and the upper surface of the dynamic powder cylinder can be ensured to be in the same plane; the local powder paving device moves along the upper surface of the dynamic powder cylinder, and metal powder which is sent into the local powder paving device by the synchronous powder feeding device through the powder feeding pipe is paved into a cavity between a first side wall and a second side wall of the dynamic powder cylinder along the outline track of the part; after the local powder paving device paves powder, stopping moving, starting a laser printing light path system to work, and melting and solidifying metal powder on the surface of the dynamic powder cylinder into the cross section shape of the part to be formed according to the outline cross section shape of the part to be processed by controlling the technological parameters and scanning strategies of laser beam scanning; the whole forming process is carried out under the protection of inert gas; after the complete layer scanning is finished, the FDM printing system, the milling and material reducing processing system and the laser printing light path system integrally move upwards along the guide upright column by a distance (20-100 mu m) of the powder layer thickness, and the layer thickness is determined according to the section data of the model; the FDM printing system continuously prints the first side wall and the second side wall of the dynamic powder cylinder according to the profile cross section shape of the part to be machined on the upper surfaces of the first side wall and the second side wall of the dynamic powder cylinder which are milled previously; then, forming parts according to the sequence of milling, local powder spreading and laser printing forming in sequence, and repeatedly circulating to manufacture the parts finally required; and a powder recovery device (an explosion-proof dust collector sucks unfused powder) is arranged around the powder cylinder and used for collecting redundant powder in the formed annular powder cylinder, and the powder recovery device can automatically recover and screen the powder and circularly enter the powder feeder to realize the recycling of the powder.
The side of the local powder bed protective cover can be provided with a plurality of observation windows so as to observe the SLM forming process in real time. The local powder bed protective cover can be provided with a camera, the real-time powder laying process is intelligently monitored through the camera, and the powder can be laid for multiple times through data analysis; by monitoring the fluctuation conditions of current and voltage of the optical path system, the real-time monitoring of the laser power stability can be realized; intelligently monitoring parameters of a forming process through a pressure sensor, a flow sensor, a water oxygen content monitoring sensor and a temperature sensor; carrying out real-time online monitoring on the temperature field of the molten pool in the forming process by adopting a thermal infrared imager and the like; the method adopts app or WeChat small program remote monitoring, fault intelligent analysis and prompting, and people do not need to stare at the site all the time; by acquiring, mining and analyzing all data in the forming process in real time on line, large data sample support is provided for ensuring the forming quality of parts for a long time and optimizing subsequent processes.
A water cooling device, an eddy current heating device, an electromagnetic system, an ultrasonic system and the like can be arranged around the dynamic powder cylinder, the heat and mass transfer characteristics, the melt flow characteristics, the temperature field and the cooling speed of a molten pool in the forming process are changed, the solidification characteristics of the structure are changed, the grain refinement is realized, and the structure and the mechanical properties required by the forming part are customized by adjusting the process parameters and the external access means through process research.

Claims (9)

1. The utility model provides a vibration material disk developments shop powder system, includes powder jar, send the powder pipeline and spread powder device, its characterized in that: the powder bed protective cover and the guide movement mechanism are arranged on the outer side of the powder bed; the upper end surface of the local powder bed protective cover is provided with a light-passing area corresponding to the upper laser printing light path system;
the cross section outline of the powder cylinder is matched with the maximum cross section outline size of a part to be formed; the two side walls of the powder recording cylinder are respectively a first side wall and a second side wall corresponding to the two sides of the section of the part to be formed; the first side wall and the second side wall are finally closed in the horizontal direction to form the cross section profile of the powder cylinder; a powder spreading area is formed between the first side wall and the second side wall of the powder cylinder;
the lower end face of the local powder bed protective cover is hollow, and the width of the local powder bed protective cover is larger than the distance between the first side wall and the second side wall, so that the local powder bed protective cover can be directly erected on the upper surfaces of the first side wall and the second side wall of the powder cylinder;
the powder spreading device comprises a buffer bin and a scraper, the buffer bin is fixed on the front side surface of the local powder bed protective cover and is close to the lower end surface, the powder feeding pipeline is introduced into the buffer bin, the lower end of the buffer bin is provided with a powder outlet corresponding to the powder spreading area, the scraper is fixed on the lower part of the buffer bin, and the working surface of the scraper is flush with or slightly lower than the lower end surface of the local powder bed protective cover;
and the guide movement mechanism is used for driving the local powder bed protective cover and the powder spreading device to synchronously run to the next local powder spreading area according to a preset track after the corresponding local powder spreading at the local powder bed protective cover and the laser processing of the local powder spreading area are completed according to a process instruction.
2. The additive manufacturing dynamic dusting system of claim 1 wherein: the guide motion mechanisms are provided with precise grating rulers in three-dimensional directions, and closed-loop feedback is provided for guide motion so as to ensure the positioning precision and the repeated positioning precision of operation.
3. The additive manufacturing dynamic dusting system of claim 1 wherein: and scrapers with various sizes are arranged and fixed at the lower part of the buffer bin in a detachable mode.
4. The additive manufacturing dynamic dusting system of claim 1 wherein: and a powder recovery device is also arranged at the periphery of the powder cylinder and used for sucking the unfused powder away in time.
5. The additive manufacturing dynamic dusting system of claim 1 wherein: the upper parts of the front side and the rear side of the local powder bed protective cover are provided with an air inlet pipe and an air outlet pipe, the air inlet pipe is used for introducing inert gas into a powder paving area in the local powder bed protective cover, and the air inlet pipe and the air outlet pipe form a circulating pipeline.
6. The additive manufacturing dynamic dusting system of claim 1 or 5, wherein: the inner walls of the front side and the rear side of the local powder bed protective cover are respectively provided with a coanda cavity, the air inlets of the coanda cavities are correspondingly arranged on the upper parts of the front side surface and the rear side surface of the local powder bed protective cover, and the air guide slits are positioned on the lower end surface of the local powder bed protective cover; the area between the front coanda cavity and the rear coanda cavity is a powder spreading area in the local powder bed protective cover; the coanda cavity is spaced from the outer edges of the first and second sidewalls to leave a flue gas flow passage.
7. The additive manufacturing dynamic dusting system of claim 1 wherein: and the top of the local powder bed protective cover is provided with an air blowing inclined hole for introducing inert gas.
8. The additive manufacturing dynamic dusting system of claim 1 wherein: and the left side surface and the right side surface of the lower part of the local powder bed protective cover are provided with channels for discharging smoke dust.
9. The additive manufacturing dynamic dusting system of claim 8 wherein: the channel for discharging the smoke dust is specifically a porous air inlet and a porous air outlet which are respectively arranged on the left side surface and the right side surface of the lower part of the local powder bed protective cover, wherein the porous air inlet is used for introducing inert gas, and the porous air outlet is connected with an air extractor so as to discharge the smoke dust by utilizing negative pressure.
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