Method of additive manufacturing of irregularly shaped articles
By reducing internal friction and vibration fluidization compaction technology, the labor intensity and cost problems of complex shape casting mold manufacturing in the prior art are solved, productivity and product accuracy are improved, and a more efficient casting process is achieved.
Patent Information
- Application Number
- CN202380037229.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-04-29
- Filing Date
- 2023-04-19
- Publication Date
- 2024-12-10
AI Technical Summary
The prior art when manufacturing casting molds and rods of complex shapes, the labor intensity is high, the cost is high, and the material limitations and process complexity are high, resulting in low production efficiency and reduced product accuracy.
By reducing the internal friction of the applied material and the friction of the leveling device on the molding material, the vibration fluidization and vibration compaction technology are used to vibrate the mixture in the front area of the leveling device, and the multi-nozzle piezoelectric print head is used to send the mixture The adhesive is added to improve the application quality and speed of the layer.
This significantly reduces defects in the formation process of the layer, improves product accuracy and strength, reduces internal friction, improves process productivity and application speed, and reduces waste generation.
Smart Images
Figure CN119110768A_ABST
Abstract
Description
[0001] The present invention relates to metallurgy and more particularly to the technique of synthesizing complex casting molds layer by layer from a mixture of refractory forming materials and binder components and can be used to manufacture unique casting molds and bars of particularly complex configurations for use in aircraft, automotive, shipbuilding and other industries.
[0002] Nowadays, rapid prototyping technology for complex-shaped products is of great significance because it can produce casting molds and bars of any structure in the shortest time, greatly speeding up the time it takes to bring products to market, improving the degree of personalization of production, and accelerating the response to new market and engineering requirements.
[0003] Thus, RU 2532753 C1 (published on October 11, 2014, B22C 9 / 04) in the prior art discloses a process for manufacturing a multilayer shell mold for investment casting, comprising applying a refractory suspension in layers starting from the second shell to a melt mold block, using oxygen-containing substances and boric acid, sprinkling with granular material, melting, drying and calcining the mold, wherein oxygen-containing substances are introduced into the composition of the refractory suspension, boric acid is added in an amount of 3-4% by weight. As an oxygen-containing substance, a semi-finished product processed from nitrate bath sludge is used in the heat treatment workshop in the tempering operation, and its amount is 2-4% by weight of the suspension.
[0004] The known solutions have the disadvantage of being labour-intensive and costly, since, when implementing the known methods, the product model is first made manually on a numerically controlled (CNC) machine or made from plastic using additive technologies: a wax copy is obtained, on which the shell mould is applied layer by layer, according to the SLA, SLS and DLP methods. The wax model is then removed and the metal is cast into the mould. This prolongs the manufacturing time and the technological chain. The use of the technology is also limited when there are grooves and cavities inside the casting, due to the high labour intensity or the impossibility of removing the mould material from the casting.
[0005] Thus, RU 2680168 C2 (published on February 18, 2019 as B22C 9 / 02, B33Y 10 / 00) in the prior art discloses a method for manufacturing a three-dimensional complex-shaped product from a sand-polymer mixture, comprising creating a three-dimensional computer model of the product to be manufactured layer by layer, preparing sand so that its dispersion does not exceed half the thickness of a single layer, mixing the sand with a polymer or oligomer composition in a sand preparation hopper, applying the sand layer by layer on a substrate according to the cross-section of the three-dimensional computer model until a predetermined shape of the product is formed, and selectively curing each layer of the sand-polymer mixture layer by layer until it hardens, wherein the selective curing of each layer of the sand-polymer mixture until it hardens is carried out in two stages at the depth of the layer, firstly, a chemical agent as a curing agent is injected into each applied sand-polymer layer by a chemical agent application device, and then, each layer is heat-treated at a temperature below the ignition temperature of the composition and not exceeding 200° C. by an infrared emitter or a laser.
[0006] Disadvantages of the known methods include mixing the sand with the polymer or oligomer component before application, which greatly increases the complexity of the applied layer or makes it impossible to apply the layer without defects and / or requires a considerable time. In this case, the method requires thermal treatment of the sand layer. Another disadvantage is the limitation of the materials used, since only silica sand can be used to implement the method.
[0007] RU 2707372 C1 (published on November 26, 2019 as B22C 9 / 02, B33Y10 / 00) in the prior art discloses a method for manufacturing a casting mold of complex geometry from a sand-polymer mixture, comprising creating a three-dimensional computer model of the casting mold to be manufactured layer by layer, preparing the sand so that its dispersion does not exceed one-third of the thickness of the applied layer, mixing the sand with a catalyst in a sand preparation hopper, applying the obtained mixture to a substrate layer by layer, and selectively curing the depth of each layer layer by layer in two stages, wherein first a polymer binder is introduced into the sand layer with the catalyst, and after completion of the binder treatment, each layer is laser processed along the contour of the manufactured part.
[0008] One of the disadvantages of the known solution is that the implementation of this method requires the sand to be prepared to a dispersion not exceeding one third of the thickness of the applied layer. In addition, each layer is laser machined along the contour of the created part, which increases the complexity and cost of the process.
[0009] RU 2742095 C1 (publication date: February 2, 2021 B22C 9 / 02, B33Y 10 / 00) in the prior art discloses a method for manufacturing a complex-shaped product from a sand-polymer mixture, comprising modeling the product layer by layer using computer software on a 3D printing device, preparing sand, laying the sand layer by layer on a substrate and applying a polymer adhesive thereon, selectively processing each layer layer by layer according to a computer cross-sectional view of the model to form the programmed shape of the product, so that after each layer is applied, the quality of the sand laying is controlled with the help of a surface quality scanner installed in the 3D printing device opposite the printing area, and the application of the adhesive is controlled using a remote vision system.
[0010] Since there is no vibration effect in this method, the sand is laid loosely, which can damage the layer during the laying process. In addition, a surface quality scanner is required in the 3D printer opposite the printing area to adjust the quality of the sand placement, and a remote vision system is used to adjust the application of the adhesive.
[0011] RU 2695084 C2 (published on July 19, 2019 as B22C 9 / 02, B33Y 10 / 00) in the prior art discloses a method for manufacturing complex-shaped products from a sand-polymer mixture. The invention states that the sand should be prepared so that it can be dispersed to half the thickness of the single layer to be applied. The sand is mixed with the polymer mixture in a hopper using a chemical catalyst such as p-toluenesulfonic acid. The mixture with a dispersion of 50-200 microns is applied to the substrate, and during the application of each layer of sand, a vibration effect is produced on the entire volume of the sand mixture in the hopper. Then, a chemical component application device injects a furfuryl alcohol-based chemical component into the sand layer according to a computer program of a single cross-sectional three-dimensional model of the product to be manufactured, so that the sand-polymer mixture is cured to the depth of the sand layer. The proportion of the chemical component is 0.5% to 1% of the mass of the sand, and the content of the chemical catalyst is 5% to 10% of the mass of the chemical component. The distance between the chemical application device and the layer to be treated does not exceed 20 mm. Then, a thermal treatment device acts on the cured area of the layer to intensify the curing process of the sand-polymer mixture. After the first layer is selectively treated chemically and thermally, the substrate is weighed down by the amount of the next layer of powder. During this process, the powder feeding and application device applies a new layer of powder material through vibration, and then the chemical and thermal treatment process is repeated until the product is manufactured.
[0012] According to the description, the technical solution uses a combination of chemical and thermal treatment technologies to treat the sand-polymer mixture to produce castings with arbitrarily complex structures, high strength characteristics, low gas volatility and high gas permeability in the best sequence, thereby producing metal castings accurately and without defects in the shortest time.
[0013] The application of vibration shocks to the full sand mixture in the hopper, which leads to product damage, poor adhesion of the sand layer and reduced product precision, are also disadvantages of this method. In addition, this method requires subsequent heat treatment, which increases the difficulty and cost of the operation. The applicability of known solutions to restricted sand-polymer mixtures and the need for additional refractory materials, which are not provided for in this method, are two other disadvantages.
[0014] The closest prior art is considered to be this solution.
[0015] The object of the invention is to provide a method that eliminates the disadvantages of the prior art and at the same time improves the quality of the received product, reduces waste and increases the productivity of the process. This problem is solved by reducing the internal friction of the applied material and the friction of the leveling device on the formed material, vibrating and fluidizing the mixture to the depth of the layer at the leveling point, and vibrating and compacting the layer, which results in a higher quality of application of the layer and significantly reduces defects during the formation of the layer.
[0016] In solving the above problems, the technical achievements of the present invention include: in the process of layering, the internal friction of the molding material and the friction between the leveling device and the molding material are reduced, and the packing density of the mixture particles is increased.
[0017] Reducing the internal friction and the friction between the leveling device and the molding material can improve the application quality of the refractory molding material layer, thereby reducing casting scraps, and can also increase the application speed of the refractory molding material.
[0018] The technical result is achieved due to the additive manufacturing of irregularly shaped products, including mixing at least one refractory molding material and at least one catalyst to obtain a catalyst-impregnated mixture based on the molding material, applying the mixture layer by layer on the working surface, introducing a binder material in the area where the mixture layer is applied, lowering the working platform to the size of the layer, repeating the process until the desired product shape is formed, it is recommended to vibrate fluidize the mixture of the applied layer to the depth of the applied layer at the leveling of the mixture, and vibrate compact the mixture of the applied layer, while feeding the mixture in the front area of the leveling device to apply a new layer on the previous layer, and feeding the binder through a multi-nozzle piezoelectric print head.
[0019] The applied layer thickness of the mixture impregnated with the catalyst-based molding material is 1 to 10 particle diameters of the refractory molding material, preferably 1 to 5 particle diameters of the refractory molding material, particularly preferably 1 to 3 particle diameters of the refractory molding material.
[0020] The refractory molding material is selected from quartz sand, zirconium oxide sand, chromite sand, olivine, vermiculite, alumina, fire clay, glass beads, granular glass, hollow aluminum silicate microspheres and mixtures thereof. The average particle diameter of the refractory molding material measured by sieve analysis is 50 to 600 μm, preferably 100 to 300 μm.
[0021] The catalyst is selected from basic and acidic catalysts.
[0022] The binder is selected from organic binders including urea-formaldehyde binders, furan binders, phenol-formaldehyde binders and inorganic binders.
[0023] The binder accounts for 0.5% to 10% of the weight of the molding material. The chemical catalyst accounts for 10% to 60% of the weight of the binder.
[0024] The adhesive is applied using a multi-nozzle piezoelectric print head, with the print head no closer than 3 mm to the layer to be treated.
[0025] Vibratory fluidization and vibratory compaction are achieved by vibrating the feed and / or leveling device of the mixture and / or vibrators on the leveling device, such as ultrasonic, electromechanical, pneumatic or other methods that reduce internal friction and compact the particles.
[0026] The mixture is added in batches, evenly and dispersedly so that a new application layer is applied on top.
[0027] The droplet size (volume) of the adhesive composition delivered by the multi-nozzle piezoelectric print head is between 5 and 200 pL, with the droplet distribution density ranging from 100-900 dots per inch (dpi).
[0028] Complex shapes can be understood as objects with multiple geometric figures on their base. More complex objects are often called composite objects, which means that the object in question is basically the sum of geometric figures.
[0029] During the leveling process, the internal friction of the refractory molding mixture and the friction between the leveling device and the molding material can be reduced due to the increase in local fluidity and the reduction in the effective viscosity of the molding mixture, that is, the vibration fluidization of the molding mixture. In order to prevent damage to the previous layer and to minimize the time that the unleveled molding material is in contact with the previous layer, another requirement for achieving the technical result is to feed the mixture for applying the new layer from a feeder into the previous layer in the area before the leveling device.
[0030] These features reduce the internal friction between the layers of applied material and the friction between the leveling device and the molding material during the layer-by-layer application of the refractory molding material.
[0031] The essence of the present invention is illustrated by the following description and schematic diagram showing an embodiment of the method of the present invention, which includes
[0032] 1-Mixture based on refractory molding materials
[0033] 2-bar flat device
[0034] 3-Working platform
[0035] 4-Rod / Mold Components
[0036] 5- New Layer
[0037] 6-Working chamber
[0038] 7-Uncured mixture
[0039] 8-Print head
[0040] 9- Adhesive
[0041] 10- Adhesive Application Process
[0042] 11-Feeding device
[0043] 12-Working surface
[0044] In the first stage, a refractory molding material selected from silica sand, zirconium oxide sand, chromite sand, olivine, vermiculite, alumina, fire clay, glass beads, granular glass, hollow aluminum silicate microspheres and mixtures thereof is mixed with a catalyst (activator, curing agent) selected from acidic catalysts, alkaline catalysts. For this purpose, a refractory molding material with an average particle size of 50 to 600 μm, preferably 100 to 300 μm, determined by sieve analysis, is used. In this way, a catalyst-impregnated mixture based on the molding material is obtained.
[0045] The resulting mixture is then applied to the working surface 3, the refractory material having a thickness of 1 to 10 grain diameters, preferably the refractory material having a thickness of 1 to 5 grain diameters, more preferably the refractory material having a thickness of 1 to 3 grain diameters.
[0046] With regard to the interval value characterizing the thickness of the applied layer made of the catalyst impregnation mixture based on the molding material, which is equal to 1 to 10 particle diameters of the refractory molding material, preferably 1 to 5 particle diameters of the refractory molding material, particularly preferably 1 to 3 particle diameters of the refractory molding material, it can be noted that since the claimed technical solution is intended to produce casting molds and rods of arbitrary design and geometry, i.e., essentially complex molds, the catalyst impregnation mixture can be used during the production of the molds and rods. Therefore, to produce complex molds, it is necessary to use a high-resolution production process, which can be compared to traditional printing processes.
[0047] Because only high resolution, especially in the claimed invention, makes it possible to manufacture casting molds and bars with complex shapes to ensure casting accuracy, when applying the concept of resolution to additive manufacturing, it is necessary to use the thickness of the applied layer (which should be minimal in this case) to improve the resolution.
[0048] It is therefore obvious to the person skilled in the art that in order to ensure accurate transfer of complex shapes and geometries in casting, the mould must have a high manufacturing accuracy, which can only be achieved through a manufacturing stage with minimum layer thickness.
[0049] In the present invention, these are determined by the capabilities of the production equipment.
[0050] In order to bond the particles of the applied layer mixture, an adhesive material is introduced into the applied layer portion according to the cross-section of the product digital model. The adhesive can be selected from the group of organic adhesives, including urea-formaldehyde adhesives, furan adhesives, phenolic adhesives and inorganic adhesives. The adhesive accounts for 0.5% to 10% of the weight of the molding material. The proportion of the chemical catalyst is 10% to 60% by weight of the adhesive. The droplet size (volume) of the adhesive component fed through the multi-nozzle piezoelectric print head is between 5 and 200 pL, and the droplet distribution density is in the range of 100-900 dots / inch (dpi).
[0051] The adhesive material is fed through a multi-nozzle piezoelectric print head 8. The distance between the print head 8 and the layer to be treated does not exceed 3 mm.
[0052] When applying a layer of binder, the mixture of the applied layer is simultaneously subjected to vibratory fluidization and vibratory compaction, but unlike the closest similar solution, in which the vibration action is carried out on the entire volume of the sand mixture in the hopper, in the proposed solution the vibration action is carried out on the mixture of the applied layer up to the depth of the applied layer where the mixture is leveled by the leveling device.
[0053] Vibratory fluidization and vibratory compaction are achieved by vibration of the feed mechanism 1 and / or leveling of the mixture. Alternatively, the vibrator on the material leveling device 2 performs vibratory fluidization and vibratory compaction by ultrasonic, electromechanical, pneumatic or other technologies that can reduce internal friction and particle compaction.
[0054] The steps of applying multiple layers of the catalyst impregnated mixture and introducing the binder material are repeated several times according to the molding material until the desired shape of the product 4 is achieved. In the front end area of the leveling device (element) 2, the mixture is uniformly added in a discrete manner, and the amount of mixture per unit time is sufficient to form a layer from the adding device to the previous layer.
[0055] Since only the mixture of the application layer is vibrated and vibrated, the internal friction in the applied material is reduced, thus improving product accuracy, strength and uniformity of the placement of the formed material, while having no effect on the remaining amount of mixture in the hopper and without damaging the formed layer. In addition, due to the reduction of internal friction, the speed of refractory application can be increased, thereby increasing the productivity of the entire process.
[0056] The refractory material is fed from the feeding device into the previous layer in the area before the device (element). This minimizes the time that the unleveled molding material is in contact with the previous layer and only affects it before the leveling device. In addition, progressive feeding (uniform or uneven) can reduce the impact on the previous layer.
Claims
1. A method for additive manufacturing of irregularly shaped articles, comprising mixing at least one refractory shaping material with at least one catalyst to obtain a catalyst-impregnated mixture based on the shaping material, applying the mixture layer by layer on a working surface, introducing a binder material in the area where the mixture layer is applied, lowering the working platform to the size of the layer, repeating the process until an article of a given shape is formed, characterized in that The mixture for applying a new layer is fed in front of the leveling device area. During the application of each layer, the mixture for the applied layer is vibrated and compacted to the depth of the applied layer at the mixture leveling point. The mixture for the applied layer is vibrated and compacted, and the binder material is fed in through a multi-nozzle piezoelectric print head.
2. The method according to claim 1, characterized in that The refractory molding material is selected from quartz sand, zirconium oxide sand, chromite sand, olivine, vermiculite, bauxite, fire clay, glass beads, granular glass, hollow aluminum silicate microspheres and mixtures thereof.
3. The method according to claim 1, characterized in that: The average particle size of the refractory molding material measured by sieve analysis is 50 to 600 μm, preferably 100 to 300 μm.
4. The method according to claim 1, characterized in that: The catalyst is selected from an acid catalyst and a basic catalyst.
5. The method according to claim 1, characterized in that The binder is selected from the group consisting of organic binders including furan binders, phenolic binders, carbonyl formaldehyde binders, or inorganic binders.
6. The method according to claim 1, characterized in that The binder content is 0.5 to 10% by weight of the sand.
7. The method according to claim 1, characterized in that The catalyst content is 10 to 60% by weight of the binder.
8. The method according to claim 1, characterized in that A multi-nozzle piezoelectric print head for applying the adhesive material is positioned at a distance of no more than 3 mm from the layer to be treated.
9. The method according to claim 1, characterized in that: Vibratory fluidization and vibratory compaction are carried out by vibration of the mixture feeding and / or leveling mechanism.
10. The method according to claim 1, characterized in that The vibrating action is performed by a vibrator mounted on the leveling device.
11. The method according to claim 1, characterized in that: The droplet size of the adhesive component supplied by the multi-nozzle piezoelectric print head is between 5 and 200 pL, wherein the droplet distribution density is in the range of 100 to 900 dots per inch.