Multi-gradient composite forming method and system

Abstract

The invention relates to a multi-gradient composite forming method and system. The method comprises the steps that a to-be-printed three-dimensional model is manufactured, the to-be-printed three-dimensional model is subjected to parting treatment, and a parting three-dimensional model is obtained; loading and identifying the three-dimensional model after parting, slicing to obtain two-dimensional contour data of each layer of sand mold, and generating a pattern of the printing sand mold of the corresponding layer; the method comprises the following steps: uniformly stirring a predetermined mass of multi-type and multi-mesh powder material and a predetermined amount of a curing agent through a pretreatment process; conveying the molding sand particles of the curing agent into a multi-material laying system; the multi-material laying system is controlled to lay different powder materials on the forming platform, and a laying layer is obtained; and the printing system is controlled to complete ink-jet printing on the current laying layer, and the laying step and the printing step are repeated until printing forming of the whole model is completed. The problems of difficult accurate shape regulation and control, raw material waste, high cost and the like of alloy castings with different complex structures and different wall thicknesses are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a multi-gradient composite forming method and system. Background Art

[0002] Additive manufacturing technology is a technology that uses a cumulative superposition method to manufacture parts. Compared with traditional cutting processing technology, it is a "bottom-up" manufacturing method. In the past two decades, additive manufacturing technology has achieved rapid development, and there are different expressions such as "rapid prototyping" and "three-dimensional printing". In recent years, the research and development of additive manufacturing technology has been rapid. As one of the additive manufacturing technologies, sand mold 3D printing technology has significantly increased its development speed and its development momentum is getting better and better.

[0003] Sand mold additive technology is particularly suitable for high-performance manufacturing of single-piece, small-batch, personalized and large-scale complex metal components. It has the advantages of strong flexible production capacity, high molding efficiency, good sand mold performance and reusable raw materials, saving molding cycle, reducing manufacturing costs and reducing material waste. It is widely used in aerospace, automobile, shipbuilding and energy and power fields. At present, most of the research on the additive manufacturing process of a single material in the market is less involved in the research of multi-material additive manufacturing in terms of materials, processes, technologies and equipment, and the application level is weak. With the gradual increase in the performance requirements for complex castings, the concepts of composite materials, composite processes and functional composite sand molds have emerged, and sand mold additive manufacturing technology has gradually developed towards green, flexible and high-performance manufacturing. In terms of forming equipment, domestic and foreign research institutions and enterprises are constantly optimizing and innovating. Among them, ExOne in the United States and Voxeljet in Germany have developed a series of sand mold printing and forming equipment, which have significant advantages in equipment stability, forming accuracy and performance. Ningxia Gongxiang, Fenghua Zhuoli, China Machinery General Academy and China Southern Airlines have conducted innovative research on processes and devices such as array nozzles, interlayer heating and compaction, and two-way sand printing. However, there is little research on multi-material composite forming methods and systems in additive manufacturing at home and abroad.

[0004] The casting properties of different sand materials vary greatly. A single material sand mold cannot have high strength, good air permeability, low gas emission, and excellent thermal properties. Multi-material composite molds can meet good casting properties, regulate the solidification process of castings, and produce high-quality castings. However, there are also shortcomings: (1) It is difficult to realize the automation of coplanar forming and sand laying of multiple sand materials, and the flexibility is weak; (2) Multifunctional gradient spraying of different types of adhesives and different adhesive contents cannot be performed on the same working surface; (3) The degree of control over the collaborative forming of additive manufacturing is low, and the solidification sequence of the casting cannot be controlled.

[0005] The multifunctional and multi-gradient composite sand mold can effectively reduce the multi-domain flow and complex mass and energy transfer during alloy pouring, long solidification time and large cooling rate differences, which lead to serious defects such as uneven grains and composition, inclusions, etc., improve the performance of castings, and manufacture high-quality castings. Summary of the invention

[0006] To this end, the present invention provides a multi-gradient composite forming method and system, which can complete the variable gradient composite sand mold forming of different types of powder materials, different mesh sizes, and different resin adhesive contents. The composite sand mold has the advantages of low cost, greenness, and excellent casting performance, and effectively solves the problems of difficult precise control of the shape of alloy castings with different complex structures and different wall thicknesses, waste of raw materials, and high cost.

[0007] In order to solve the above technical problems, the present invention provides a multi-gradient composite forming method, comprising: Making a three-dimensional model to be printed, and performing a parting process on the three-dimensional model to be printed according to the casting size, the casting wall thickness and the gradient field to obtain a parted three-dimensional model; The three-dimensional model after the parting is loaded and identified, and sliced ​​to obtain two-dimensional contour data of each layer of the sand mold, and based on the two-dimensional contour data of each layer of the sand mold, a pattern of the printed sand mold of the corresponding layer is generated; The predetermined mass of powder materials of various types and mesh sizes are uniformly stirred with a predetermined amount of curing agent through a pretreatment process to obtain molding sand particles mixed with the curing agent; conveying the molding sand particles of the curing agent to a multi-material laying system; Controlling the multi-material laying system to lay different powder materials on the forming platform to obtain a laying layer; Controlling the printing system to complete inkjet printing of different areas and different resin contents in the current laying layer; It is determined whether to perform single-layer sand-laying printing or multi-layer sand-laying printing, and the laying step and the printing step are repeated until the printing of the entire model is completed.

[0008] In one embodiment of the present invention, the three-dimensional model to be printed is subjected to a parting process according to the casting size, the casting wall thickness and the gradient field, including: The casting size is expressed as length×width, and the casting wall thickness is determined according to different casting sizes and different casting materials; The casting is divided into functional areas and supporting areas, and the grayscale levels of different resin contents are determined according to different areas of the casting to achieve gradient field changes.

[0009] In one embodiment of the present invention, according to different casting sizes and different casting materials, the size of the casting wall thickness is determined, including: When the casting material is aluminum alloy: When Td≤200mm×200mm, Tc≥3mm; When 200mm×200mm≤Td≤500mm×500mm, Tc≥4mm; When Td≥500mm×500mm, Tc≥5mm; When the casting material is magnesium alloy: When 200mm×200mm≤Td≤500mm×500mm, Tc≥3mm; When the casting material is gray cast iron: When Td≤200mm×200mm, Tc≥5mm; When 200mm×200mm≤Td≤500mm×500mm, Tc≥6mm; When Td≥500mm×500mm, Tc≥15mm; When the casting material is cast steel: When Td≤200mm×200mm, Tc≥6mm; When 200mm×200mm≤Td≤500mm×500mm, Tc≥10mm; When Td≥500mm×500mm, Tc≥18mm; Where, Td is the casting size; Tc is the casting wall thickness.

[0010] In one embodiment of the present invention, different gray levels of resin content are determined according to different regions of the casting to achieve gradient field changes, including: The resin content in the gradient field close to the sand mold functional area is set to gray levels 1, 2, and 3 in sequence, using chromite sand and / or zircon sand; the resin content in the gradient field away from the sand mold support area is set to gray levels 4, 5, and 6 in sequence, using silica sand; Among them, gray levels 1-6 represent different resin contents, and the larger the number, the higher the content.

[0011] In one embodiment of the present invention, when manufacturing an aluminum alloy casting, wherein Td≤200mm×200mm, Tc≥3mm, the resin content of the sand mold functional area close to the casting by the gradient field Ts is set to gray levels 1, 2, and 3, and chromite sand and / or zircon sand are used; the resin content of the sand mold support area away from the casting is set to gray levels 4, 5, and 6, and silica sand is used; when 200mm×200mm≤Td≤500mm×500mm, 4mm≤Tc, the resin content of the sand mold functional area close to the casting by the gradient field Ts is set to gray levels 1, 2, and 3, and chromite sand and / or zircon sand are used; the resin content of the sand mold support area away from the casting is set to gray levels 4, 5, and 6, and silica sand is used.

[0012] The present invention also provides a multi-gradient composite forming system, comprising: A parting processing system is used to prepare a three-dimensional model to be printed, and to perform parting processing on the three-dimensional model to be printed according to the casting size, casting wall thickness and gradient field to obtain a three-dimensional model after parting; A printing sand mold pattern generation system is used to load and identify the three-dimensional model after the parting, and perform slicing processing to obtain two-dimensional contour data of each layer of the sand mold, and generate a printing sand mold pattern of the corresponding layer based on the two-dimensional contour data of each layer of the sand mold; A raw material storage system is used to uniformly mix powder materials of various types and mesh sizes of predetermined mass and a predetermined amount of curing agent through a pretreatment process to obtain molding sand particles mixed with the curing agent; An automatic feeding system for conveying the molding sand particles of the curing agent; A multi-material laying system is used to lay different powder materials on a forming platform to obtain a laying layer; The printing system is used to complete inkjet printing of different areas and different resin contents in the current laying layer.

[0013] In one embodiment of the present invention, the material laid by the multi-material paving system is one or more of quartz sand, expanded clay sand, chromite sand, zircon sand, magnesia sand, olivine sand, ceramic powder, metal powder, gypsum powder, and short fibers, and the particle size distribution is 70~1000 mesh.

[0014] In one embodiment of the present invention, the multi-material laying system includes a main laying device and an auxiliary laying device which are movably arranged on the upper side of the forming platform, and the opening size of the sand laying openings of the main laying device and the auxiliary laying device are adjustable; the main laying device is used for laying molding sand particles of various materials, and the auxiliary laying device is used for laying special powder materials.

[0015] In one embodiment of the present invention, the printing system includes a first printing system and a second printing system arranged on both sides of the forming platform, the first printing system and the second printing system each include a plurality of printing heads, each of the printing heads includes a one-position three-way connector, and each access port of the one-position three-way connector is equipped with a solenoid valve, and the type and concentration of the adhesive can be changed by controlling the connection and locking of the solenoid valve.

[0016] In one embodiment of the present invention, a waste sand recovery circulation system is also included, which is used to collect waste materials generated during the forming process, recycle different materials and different types of sand, and return them to the raw material storage system.

[0017] The above technical solution of the present invention has the following advantages compared with the prior art: The multi-gradient composite forming method and system described in the present invention can complete the forming of variable gradient composite sand molds with different types of powder materials, different mesh sizes, and different resin adhesive contents. The composite sand mold has the advantages of low cost, greenness, and excellent casting performance, and effectively solves the problems of difficult precise control of the shape of alloy castings with different complex structures and different wall thicknesses, waste of raw materials, and high cost. It realizes the automated and flexible sand laying of coplanar forming of multiple molding sand materials, and simultaneously sprays different types of adhesives and adhesives with different contents on the same working surface, thereby improving the degree of control over the collaborative shape forming of additive manufacturing, regulating the solidification sequence of castings, and improving the quality of castings.

[0018] The present invention can optimize the performance distribution of sand mold materials according to the functional requirements of different areas through the mold separation process, improve the overall performance of the sand mold and the quality of the casting. Select appropriate sand mold materials and resin content, and optimize the performance of the functional area and the support area through gradient control to balance thermal conductivity, air permeability and cost. The gradient field is close to the grayscale level 1-3 of the functional area, and the resin content increases step by step. Chromite sand and zircon sand with excellent thermal conductivity are used to accelerate the solidification of the alloy and refine the grain structure. The gradient field is away from the grayscale level 4-6 of the support area, and the resin content increases step by step. Silica sand with good air permeability, high strength and low cost is used to improve air permeability and reduce overall cost.

[0019] The present invention can effectively reduce the multi-domain flow and complex mass and energy transfer during alloy pouring, long solidification time, large cooling rate difference, resulting in serious defects such as uneven grains and components, inclusions, etc., improve the performance of castings, and manufacture high-quality castings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0021] Figure 1 It is a flow chart of the multi-gradient composite forming method of the present invention.

[0022] Figure 2 It is a schematic diagram of the layout of the multi-gradient composite forming system of the present invention.

[0023] Figure 3 It is a structural schematic diagram of the multi-gradient composite forming system of the present invention.

[0024] Figure 4 It is a structural diagram of the main laying device of the present invention.

[0025] Figure 5 It is a linkage structure diagram of the main laying device of the present invention.

[0026] Figure 6 It is a main structural diagram of the main laying device of the present invention.

[0027] Figure 7 It is a schematic diagram of the structure of the three-way atomizing nozzle of the present invention.

[0028] Figure 8 It is a schematic diagram of one side of the three-way atomizing nozzle of the present invention.

[0029] Fig. 9 It is a schematic diagram of the other side of the three-way atomizing nozzle of the present invention.

[0030] Description of the Figures in the Specification: 1. Main laying device; 2. Auxiliary laying device; 3. First printing system; 4. Second printing system II. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0032] In the present invention, if directions (up, down, left, right, front and back) are described, it is only for the convenience of describing the technical solution of the present invention, and does not indicate or imply that the technical features referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, it cannot be understood as a limitation of the present invention.

[0033] In the present invention, "several" means one or more, "multiple" means more than two, "greater than", "less than", "exceed" and the like are understood to exclude the number itself; "above", "below", "within" and the like are understood to include the number itself. In the description of the present invention, if there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0034] In the present invention, unless otherwise clearly defined, the words "set", "install", "connect" and the like should be understood in a broad sense, for example, they can be directly connected or indirectly connected through an intermediate medium; they can be fixedly connected or detachably connected or integrally formed; they can be mechanically connected or electrically connected or able to communicate with each other; they can be the internal connection of two elements or the interaction relationship between two elements. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0035] Example 1 Reference Figure 1 As shown, a multi-gradient composite forming method of the present invention comprises: S1. Prepare a three-dimensional model to be printed, and perform parting processing on the three-dimensional model to be printed according to the casting size, casting wall thickness and gradient field to obtain a three-dimensional model after parting; CAD software (such as SolidWorks, AutoCAD, etc.) can be used to design the three-dimensional model of the casting to ensure that the model meets engineering requirements and manufacturing specifications.

[0036] S2, loading and identifying the three-dimensional model after the parting, and performing slicing processing to obtain the two-dimensional contour data of each layer of the sand mold, and generating a pattern of the printed sand mold of the corresponding layer based on the two-dimensional contour data of each layer of the sand mold.

[0037] S3, uniformly stirring a predetermined mass of powder materials of various types and mesh sizes with a predetermined amount of a curing agent through a pretreatment process to obtain molding sand particles mixed with a curing agent; S4, conveying the molding sand particles of the curing agent to the multi-material laying system; pneumatic conveying, mechanical conveying, etc. may be used; S5, controlling the multi-material laying system to lay different powder materials on the forming platform to obtain a laying layer; S6. Control the printing system to complete inkjet printing of different areas and different resin contents in the current laying layer; each powder material is equipped with an independent laying nozzle, and the opening and closing of each nozzle is independently controlled by the control system to achieve synchronous laying of multiple materials, and the laying amount and density of different materials are controlled by adjusting the opening size and laying speed of the nozzle.

[0038] S7, determining whether to perform single-layer sand-laying printing or multi-layer sand-laying printing, and repeating the laying step and the printing step until the printing of the entire model is completed.

[0039] Specifically, according to the casting size, casting wall thickness and gradient field, the three-dimensional model to be printed is subjected to type division processing, including: The casting size is expressed as length×width, and the casting wall thickness is determined according to different casting sizes and different casting materials; The casting is divided into functional areas and supporting areas, and the grayscale levels of different resin contents are determined according to different areas of the casting to achieve gradient field changes.

[0040] Specifically, according to different casting sizes and different casting materials, the size of the casting wall thickness is determined, including: When the casting material is aluminum alloy: When Td≤200mm×200mm, Tc≥3mm; When 200mm×200mm≤Td≤500mm×500mm, Tc≥4mm; When Td≥500mm×500mm, Tc≥5mm; When the casting material is magnesium alloy: When 200mm×200mm≤Td≤500mm×500mm, Tc≥3mm; When the casting material is gray cast iron: When Td≤200mm×200mm, Tc≥5mm; When 200mm×200mm≤Td≤500mm×500mm, Tc≥6mm; When Td≥500mm×500mm, Tc≥15mm; When the casting material is cast steel: When Td≤200mm×200mm, Tc≥6mm; When 200mm×200mm≤Td≤500mm×500mm, Tc≥10mm; When Td≥500mm×500mm, Tc≥18mm; Where, Td is the casting size; Tc is the casting wall thickness.

[0041] Specifically, different gray levels of resin content are determined according to different areas of the casting to achieve gradient field changes, including: The resin content in the gradient field close to the sand mold functional area is set to gray levels 1, 2, and 3 in sequence, and chromite sand and zircon sand with excellent thermal conductivity are used to accelerate alloy solidification and refine the structure; the resin content in the gradient field away from the sand mold support area is set to gray levels 4, 5, and 6 in sequence, and silica sand is used to improve air permeability and reduce overall costs; Among them, gray levels 1-6 represent different resin contents, and the larger the number, the higher the content.

[0042] It should be noted that the sand mold functional area is the area in the sand mold that is in direct contact with the casting, responsible for transferring heat, supporting the shape of the casting, and plays a key role in the solidification process of the casting. The sand mold support area is located outside the functional area and is mainly responsible for providing structural support and enhancing the overall stability and air permeability of the sand mold.

[0043] Taking aluminum alloy castings as an example, when manufacturing aluminum alloy castings, where Td≤200mm×200mm, Tc≥3mm, the resin content of the sand mold functional area close to the casting in the gradient field Ts is set to gray levels 1, 2, and 3, and chromite sand and zircon sand with excellent thermal conductivity are used to increase the thermal properties of the sand mold; the resin content of the sand mold support area away from the casting is set to gray levels 4, 5, and 6, and silica sand with good air permeability, high strength, and low cost is used. When 200mm×200mm≤Td≤500mm×500mm, 4mm≤Tc, the resin content of the sand mold functional area close to the casting in the gradient field Ts is set to gray levels 1, 2, and 3, and chromite sand and zircon sand with excellent thermal conductivity are used to increase the thermal properties of the sand mold; the resin content of the sand mold support area away from the casting is set to gray levels 4, 5, and 6, and silica sand with good air permeability, high strength, and low cost is used.

[0044] According to the requirements of sand mold size and casting wall thickness, select the appropriate gradient field Ts ratio (1:1, 1:2, 1:3) to divide the functional area and the support area. According to the actual size of the sand mold, the ratio of the functional area to the support area is reasonably divided. By setting different gradient field Ts ratios, the physical properties of the sand mold, the forming quality of the casting, and the production cost and resource utilization can be optimized.

[0045] Therefore, the resin content of the functional area of ​​the sand mold is low to increase thermal conductivity, and chromite sand and zircon sand with excellent thermal conductivity are selected to accelerate the solidification of the alloy, refine the grain structure, and improve the quality of castings. The resin content of the support area of ​​the sand mold is high to enhance the air permeability and support of the sand mold. Silica sand with good air permeability, high strength and low cost is selected to ensure the stability and economy of the sand mold.

[0046] Specifically, in step S2, the three-dimensional model after parting can be imported into a dedicated slicing software or forming control software (such as Materialise Magics, Siemens NX, etc.). Automatic identification of functional areas and support areas: The software automatically identifies the functional areas and support areas in the model and marks them according to the pre-set parting rules. Corresponding grayscale levels and material properties are assigned to different areas to ensure correct application in subsequent slicing and printing processes.

[0047] The thickness of each layer is set (usually between 0.1mm and 1mm) according to the precision requirements of sand mold forming and material properties.

[0048] Determine the direction and angle of the slices to optimize the forming quality of the sand mold and the molding effect of the casting.

[0049] The software cuts the model into several layers based on the 3D model and slicing parameters, and generates 2D contour data for each layer.

[0050] Optimize 2D contour data, eliminate overlaps, correct errors, etc. to ensure data accuracy and printability.

[0051] According to the 2D contour data, the path of sand mold laying and resin injection is planned to ensure accurate laying and bonding of materials. Combined with the grayscale information, the resin injection mode of different areas is designed to achieve multi-gradient composite sand molds.

[0052] Convert the designed pattern into machine-readable printing instructions to control the actions of the laying system and printing system.

[0053] Preview and verify the pattern through the software, and submit it to the forming system for execution after ensuring it is correct.

[0054] Specifically, in step S3, according to the requirements of the mold processing, quartz sand, ceramsite sand, chromite sand, zircon sand, magnesia sand, olivine sand, ceramic powder, metal powder, gypsum powder, short fiber, etc. are selected. According to the detailed requirements of the sand mold, powder materials with different particle sizes (70-1000 mesh) are selected to meet the forming requirements of different regions. A suitable resin is selected as a curing agent, and the type and concentration of the resin are adjusted according to the gray level requirements.

[0055] Exemplarily, the pretreatment process includes uniform stirring, screening (removing unqualified particles through a vibrating screen or airflow screening equipment to ensure that the particle size distribution of the powder material meets the requirements), sampling and analysis (regular sampling to test the uniformity of the powder mixture to ensure that the ratio of various types of powders and curing agents is consistent), storage, etc.

[0056] In step S7, different materials are laid layer by layer according to the slice data and gradient field requirements to ensure the gradient performance and structural stability of the sand mold. The laying process is monitored in real time by a high-definition camera or scanner to detect the uniformity and coverage of the material laying. According to the monitoring data, the laying parameters (such as laying speed, material flow, etc.) are dynamically adjusted to ensure the laying quality; when abnormal conditions (such as material blockage, laying error, etc.) are detected, an alarm is triggered and the laying is automatically adjusted or stopped to prevent further quality problems.

[0057] Example 2 Reference Figure 2 As shown, this embodiment provides a multi-gradient composite forming system, including: A parting processing system is used to prepare a three-dimensional model to be printed, and to perform parting processing on the three-dimensional model to be printed according to the casting size, casting wall thickness and gradient field to obtain a three-dimensional model after parting; A printing sand mold pattern generation system is used to load and identify the three-dimensional model after the parting, and perform slicing processing to obtain two-dimensional contour data of each layer of the sand mold, and generate a printing sand mold pattern of the corresponding layer based on the two-dimensional contour data of each layer of the sand mold; A raw material storage system is used to uniformly mix powder materials of various types and mesh sizes of predetermined mass and a predetermined amount of curing agent through a pretreatment process to obtain molding sand particles mixed with the curing agent; The automatic feeding system is used to convey the molding sand particles of the curing agent; it can perform color and mesh screening and vacuum feeding; the raw material storage system quantitatively outputs or quantitatively conveys various powder materials and conveys them to the automatic feeding system for further screening or vacuum feeding; A multi-material laying system is used to lay different powder materials on a forming platform to obtain a laying layer; The printing system is used to complete inkjet printing of different areas and different resin contents in the current laying layer.

[0058] Specifically, the material laid by the multi-material laying system is one or more of quartz sand, ceramsite sand, chromite sand, zircon sand, magnesia sand, olivine sand, ceramic powder, metal powder, gypsum powder, and short fibers, and the particle size distribution is 70-1000 meshes. It is ensured that different materials maintain a stable physical and chemical state (such as particle size distribution, dryness, uniformity of mixing with curing agent, etc.) before use, providing raw materials with good consistency for subsequent laying and printing.

[0059] Reference Figure 3 As shown, specifically, the multi-material laying system includes a main laying device 1 and an auxiliary laying device 2 which are movably arranged on the upper side of the forming platform. A dual-axis motion platform (such as ball screw drive or servo motor control) can be used to achieve precise two-dimensional laying, and a multi-layer stacking mechanism: used to stack different materials layer by layer to achieve a complex three-dimensional structure.

[0060] Reference Figures 4 to 6 As shown, the opening sizes of the sand laying openings of the main laying device 1 and the auxiliary laying device 2 are adjustable; the amount of sand falling from each sand laying opening can be controlled by connecting the cylinder and the baffle plate, so as to control the amount of sand falling of different powder materials; the main laying device 1 is used for laying molding sand particles of multiple (more than six) materials, and the auxiliary laying device 2 is used for laying special powder materials, such as metal powder, ceramic powder, etc., to improve the flexibility and personalization of laying.

[0061] Exemplarily, the raw material storage system includes multiple silos, and each material is equipped with an independent storage container, such as a vertical silo and a horizontal storage tank. The vertical silo is suitable for bulk storage, such as quartz sand, ceramsite sand, etc., and the materials are transported to the laying system by gravity or pneumatic conveying system; the horizontal storage tank is suitable for materials with poor fluidity, and the materials are transported by mechanical vibration or screw conveyor. In order to ensure the uniformity and fluidity of the materials before laying, a stirring device (such as a horizontal storage tank, a mechanical stirrer) is equipped to evenly mix the powder material and the curing agent to prevent the materials from settling or agglomerating during storage.

[0062] Reference Figures 7 to 9 As shown, specifically, the printing system includes a first printing system 3 and a second printing system arranged on both sides of the forming platform, the first printing system 3 and the second printing system each include a plurality of printing heads, each of the printing heads includes a one-position three-way connector, and each access port of the one-position three-way connector is equipped with a solenoid valve, and the type and concentration of the adhesive can be changed by controlling the connection and locking of the solenoid valve.

[0063] In this embodiment, six print heads are formed, and the six print heads can respectively spray different contents of resin, and perform resin spraying in different areas according to the slice information. The print heads spray multi-gradient resin contents, and use electrical signals to control the connection and locking of the electromagnetic valve, so as to change the type and concentration of the adhesive.

[0064] The computer controls the multi-material laying system to move from one side of the forming platform to the other side. The combined printing system performs inkjet printing in different areas as needed. Through online detection feedback and intelligent recognition system, it determines whether to execute single-layer sand laying printing or multi-layer sand laying printing. The laying and printing process is repeated until the model is printed and formed.

[0065] The computer's built-in slicing software has the functions of horizontal cutting, vertical cutting, feedback, recognition, and allocation. Its slicing information has a grading function. It can load, recognize, and slice the printed three-dimensional geometric model according to the classification principle, and generate the pattern of each layer of printed sand mold according to the two-dimensional contour data of each layer of sand mold.

[0066] Specifically, it also includes a waste sand recovery circulation system. After cleaning the waste sand and taking out the sand mold, the waste materials generated during the forming process are collected through the waste sand recovery circulation system, and different materials and different types of sand are recycled and processed, and then sent back to the raw material storage system. Exemplarily, the waste sand recovery circulation system includes: a waste sand collection device, which collects the generated waste sand and waste materials to ensure that the waste sand is effectively transmitted to the recovery system, and an automatic conveyor belt system, a pneumatic conveying system, etc. can be used; a waste sand preliminary treatment device, which performs preliminary screening and impurity removal on the collected waste sand, removes large-particle impurities and non-sand materials, and a vibrating screener, a gravity separator, etc. can be used; a waste sand cleaning and drying device, which removes resin, oil and other pollutants in the waste sand, restores the purity and reusability of the sand particles, and a spray device, a cyclone and a filtration system can be used to clean the sand particles with water or solvents.

[0067] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0068] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0069] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0070] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0071] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A multi-gradient composite forming method, characterized in that: include: Making a three-dimensional model to be printed, and performing a parting process on the three-dimensional model to be printed according to the casting size, the casting wall thickness and the gradient field to obtain a parted three-dimensional model; The three-dimensional model after the parting is loaded and identified, and sliced ​​to obtain two-dimensional contour data of each layer of the sand mold, and based on the two-dimensional contour data of each layer of the sand mold, a pattern of the printed sand mold of the corresponding layer is generated; The predetermined mass of powder materials of various types and mesh sizes are uniformly stirred with a predetermined amount of curing agent through a pretreatment process to obtain molding sand particles mixed with the curing agent; conveying the molding sand particles of the curing agent to a multi-material laying system; Controlling the multi-material laying system to lay different powder materials on the forming platform to obtain a laying layer; Controlling the printing system to complete inkjet printing of different areas and different resin contents in the current laying layer; It is determined whether to perform single-layer sand-laying printing or multi-layer sand-laying printing, and the laying step and the printing step are repeated until the printing of the entire model is completed.

2. A multi-gradient composite forming method according to claim 1, characterized in that: According to the casting size, casting wall thickness and gradient field, the three-dimensional model to be printed is subjected to type-parting processing, including: The casting size is expressed as length×width, and the casting wall thickness is determined according to different casting sizes and different casting materials; The casting is divided into functional areas and supporting areas, and the grayscale levels of different resin contents are determined according to different areas of the casting to achieve gradient field changes.

3. A multi-gradient composite forming method according to claim 2, characterized in that: According to different casting sizes and different casting materials, determine the size of the casting wall thickness, including: When the casting material is aluminum alloy: When Td≤200mm×200mm, Tc≥3mm; When 200mm×200mm≤Td≤500mm×500mm, Tc≥4mm; When Td≥500mm×500mm, Tc≥5mm; When the casting material is magnesium alloy: When 200mm×200mm≤Td≤500mm×500mm, Tc≥3mm; When the casting material is gray cast iron: When Td≤200mm×200mm, Tc≥5mm; When 200mm×200mm≤Td≤500mm×500mm, Tc≥6mm; When Td≥500mm×500mm, Tc≥15mm; When the casting material is cast steel: When Td≤200mm×200mm, Tc≥6mm; When 200mm×200mm≤Td≤500mm×500mm, Tc≥10mm; When Td≥500mm×500mm, Tc≥18mm; Where, Td is the casting size; Tc is the casting wall thickness.

4. A multi-gradient composite forming method according to claim 2, characterized in that: Determine the grayscale level of different resin content according to different areas of the casting to achieve gradient field changes, including: The resin content in the gradient field close to the sand mold functional area is set to gray levels 1, 2, and 3 in sequence, using chromite sand and / or zircon sand; the resin content in the gradient field away from the sand mold support area is set to gray levels 4, 5, and 6 in sequence, using silica sand; Among them, gray levels 1-6 represent different resin contents, and the larger the number, the higher the content.

5. The multi-gradient composite forming method according to claim 2, characterized in that: When manufacturing aluminum alloy castings, T d ≤200mm×200mm, Tc≥3mm, gradient field T s The resin content of the sand mold functional area close to the casting is set to grayscale 1, 2, and 3, using chromite sand and / or zircon sand; the resin content of the sand mold support area away from the casting is set to grayscale 4, 5, and 6, using silica sand; when 200mm×200mm≤T d ≤500mm×500mm, 4mm≤T c , gradient field T s The resin content of the sand mold functional area close to the casting is set to gray levels 1, 2, and 3, and chromite sand and / or zircon sand are used; the resin content of the sand mold support area away from the casting is set to gray levels 4, 5, and 6, and silica sand is used.

6. A multi-gradient composite forming system, characterized in that: include: A parting processing system is used to prepare a three-dimensional model to be printed, and to perform parting processing on the three-dimensional model to be printed according to the casting size, casting wall thickness and gradient field to obtain a three-dimensional model after parting; A printing sand mold pattern generation system is used to load and identify the three-dimensional model after the parting, and perform slicing processing to obtain two-dimensional contour data of each layer of the sand mold, and generate a printing sand mold pattern of the corresponding layer based on the two-dimensional contour data of each layer of the sand mold; A raw material storage system is used to uniformly mix powder materials of various types and mesh sizes of predetermined mass and a predetermined amount of curing agent through a pretreatment process to obtain molding sand particles mixed with the curing agent; An automatic feeding system for conveying the molding sand particles of the curing agent; A multi-material laying system is used to lay different powder materials on a forming platform to obtain a laying layer; The printing system is used to complete inkjet printing of different areas and different resin contents in the current laying layer.

7. A multi-gradient composite forming system according to claim 6, characterized in that: The material laid by the multi-material paving system is one or more of quartz sand, ceramsite sand, chromite sand, zircon sand, magnesia sand, olivine sand, ceramic powder, metal powder, gypsum powder, and short fibers, and the particle size distribution is 70-1000 meshes.

8. The multi-gradient composite forming system according to claim 6, characterized in that: The multi-material laying system includes a main laying device and an auxiliary laying device which are movably arranged on the upper side of the forming platform, and the opening size of the sand laying openings of the main laying device and the auxiliary laying device are adjustable; the main laying device is used for laying molding sand particles of various materials, and the auxiliary laying device is used for laying special powder materials.

9. A multi-gradient composite forming method and system according to claim 6, characterized in that: The printing system includes a first printing system and a second printing system arranged on both sides of the forming platform. The first printing system and the second printing system are both composed of multiple printing heads. Each of the printing heads includes a one-position three-way connector. Each access port of the one-position three-way connector is equipped with a solenoid valve. The type and concentration of the adhesive can be changed by controlling the connection and locking of the solenoid valve.

10. A multi-gradient composite forming method and system according to claim 6, characterized in that: It also includes a waste sand recovery and circulation system, which is used to collect waste materials generated during the forming process, recover different materials and different types of sand, and return them to the raw material storage system.

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