Sand-box-free forming method based on sand mold 3D printing

Abstract

The invention relates to a molding method without a sand box based on sand mold 3D printing, and relates to the technical field of casting molding, a 3D printing sand mold is longitudinally split into a plurality of parts, the outer side wall of a bottom sand mold is thickened, locking grooves are designed in the thickened parts of the two symmetrical outer side walls of the bottom sand mold, and each locking groove comprises a vertical section penetrating through the top surface of the bottom sand mold; the middle part of the limiting section is connected with the bottom end of the bottom sand mold; a box tightening rod of which the bottom end is matched with the shape of the locking groove is arranged in each locking groove, and a box tightening frame is arranged above the top sand mold; and the top ends of all box tightening rods penetrate through a box tightening frame and then are screwed with box tightening nuts in a threaded mode, the bottom sand mold, the top sand mold and all the middle sand molds are locked into a combined casting mold, and therefore the problems that under the scene that a sand box capable of completely covering the sand mold does not exist, the 3D printing sand mold is difficult to assemble, the sand box capable of completely covering the sand mold can increase the sand mold manufacturing cost, and the sand mold manufacturing cost is reduced are solved. And the manufacturing period is prolonged.

Description

Technical Field

[0001] This invention relates to the field of casting and molding technology, and in particular to a sandless box molding method based on sand mold 3D printing. Background Technology

[0002] 3D printing, a type of rapid prototyping technology, is a technique that uses digital model files as a basis and employs powdered metals or plastics and other bondable materials to construct objects layer by layer. 3D printing technology is primarily used for printing plastic products and certain metal materials, but its application in casting sand mold making is still in its infancy. Traditional sand mold making involves first creating a wooden or metal mold of the part, and then using that mold as a prototype to create the sand mold. This means that if changes to the process or shape are needed during early production, the wooden or metal mold must be modified or remade. This process of repeated verification is necessary before mass production of sand molds, resulting in a lengthy development cycle. 3D printing sand molds eliminates the need for processing wooden or metal molds, directly producing the sand mold and significantly shortening the development cycle.

[0003] In the fabrication of casting sand molds, due to the large weight and volume of castings, and the large amount of sand consumed during sand printing, 3D printing equipment often cannot achieve one-piece printing of the sand mold. Instead, the sand mold must be disassembled into multiple parts, printed separately, and then assembled into a single unit. Currently, the assembly of 3D printed sand molds typically requires the use of a sand box, which necessitates the manufacture of an additional sand box capable of completely enclosing the sand mold. This increases the manufacturing cost of casting sand molds and extends their production cycle. Summary of the Invention

[0004] To address the shortcomings of related technologies, this invention provides a sand-free mold forming method based on sand mold 3D printing. The 3D-printed sand mold is longitudinally divided into multiple parts. The outer wall of the bottom sand mold is thickened, and locking grooves are designed on the thickened portions of the two symmetrical outer walls of the bottom sand mold to connect clamping rods. The clamping rods, clamping frame, and clamping nuts work together to lock the multiple parts of the 3D-printed sand mold into a combined casting mold. This solves the problem of difficult assembly of 3D-printed sand molds in scenarios where a sand box that can completely cover the sand mold is unavailable, and addresses the issue that a sand box that completely covers the sand mold increases manufacturing costs and extends the manufacturing cycle.

[0005] This invention provides a sand-free box forming method based on sand mold 3D printing, comprising: S1. Model Design: The three-dimensional model of the sand mold is divided into a bottom sand mold, a top sand mold, multiple middle sand molds, and a sand core. The outer side wall of the bottom sand mold is thickened. Locking grooves are designed in the thickened parts of the two symmetrical outer side walls of the bottom sand mold. The locking grooves include a vertical section that penetrates the top surface of the bottom sand mold and a limiting section that connects to the bottom end of the bottom sand mold in the middle. S2. Assembly preparation: 3D print the bottom sand mold, the top sand mold, the middle sand mold, and the sand core; prefabricate the clamping rod, the clamping frame, and the clamping nut; the bottom end of the clamping rod matches the shape of the locking groove; S3. Assemble the sand mold: Place the bottom sand mold on the molding base plate and apply box-fitting adhesive to the upper surface of the bottom sand mold; The intermediate sand mold is stacked onto the bottom sand mold. During the stacking process, the sand core is positioned inside the intermediate sand mold, and a bonding adhesive is applied to the parting surface of two adjacent intermediate sand molds. Apply sealing adhesive to the upper surface of the top sand mold and close the top sand mold; One of the clamping rods is installed in each locking groove, and the clamping frame is placed on the upper surface of the top sand mold; the top ends of all the clamping rods pass through the clamping frame and are screwed into the clamping nut to lock the bottom sand mold, the top sand mold and all the middle sand molds into a combined casting mold.

[0006] In some embodiments, the bottom sand mold is designed with a riser, a horizontal runner and a first sprue from bottom to top; the bottom middle sand mold is designed with a second sprue that connects to the first sprue; the remaining middle sand molds are designed with a sprue that connects to the second sprue and a cavity that connects to the sprue; the bottom surface of the top sand mold is designed with a riser that connects to the sprue.

[0007] In some embodiments, the upper surface of the bottom sand mold is provided with an installation groove for accommodating a filter screen, the filter screen being located at the junction of the first sprue and the second sprue; after the filter screen is placed in the installation groove, a sealing adhesive is then applied to the upper surface of the bottom sand mold.

[0008] In some embodiments, in step S2, a top-opening tray is prefabricated based on the model designed in S1. Hooks are provided on both sides of the tray, and a liquid-lifting through hole is provided on the bottom plate of the tray. In step S3, the bottom of the combined mold is placed inside the tray, and a first sealing layer is provided between the bottom surface of the combined mold and the bottom plate of the tray. The liquid-lifting through hole is connected to the liquid-lifting port. Sand and binder are filled between the tray and the combined mold. After the sand and binder harden, they form a sealing sand mold. The top surface of the sealing sand mold is higher than half the height of the bottommost middle sand mold.

[0009] In some embodiments, the bottom surface of the sand core in step S1 is designed with a limiting boss, and the upper surface of the lowest intermediate sand mold is designed with a limiting groove that matches the limiting boss. In step S3, after applying the sealing adhesive into the limiting groove, the limiting boss is then inserted into the limiting groove.

[0010] In some embodiments, in step S1, the parting surfaces of two adjacent medium sand molds are designed with frame-shaped sealing grooves, and the portions of the medium sand molds used for flowing liquid metal are all located inside the sealing grooves. The prefabricated metal sealing strip in S2; In step S3, when stacking the medium sand mold, a box-fitting adhesive is applied to the surface of the metal sealing strip. Multiple metal sealing strips are inserted end-to-end into the sealing groove below the parting surface of the medium sand mold. The medium sand mold with the box-fitting adhesive on its lower surface is stacked onto the medium sand mold with the metal sealing strip embedded in it, so that the remaining part of the metal sealing strip is embedded in the sealing groove above the parting surface of the medium sand mold.

[0011] In some embodiments, in step S1, the upper surface of the uppermost middle sand mold is designed with a first boss, and the bottom surface of the top sand mold is designed with a first groove matching the first boss; the bottom surface of the lowermost middle sand mold is designed with a second boss, and the upper surface of the bottom sand mold is designed with a second groove matching the second boss.

[0012] In some embodiments, two locking grooves symmetrically located on both sides of the bottom sand mold are a group, and multiple groups of locking grooves are provided, with each locking groove in the same group corresponding to one locking groove; a limiting groove is provided at each end of the locking groove, and the two symmetrically installed clamping rods move towards each other and enter the limiting grooves at both ends of the clamping frame and are then threadedly tightened with the clamping nut.

[0013] In some embodiments, the clamping frame includes a base plate and two upright plates formed on the upper surface of the base plate, the two upright plates being located on opposite sides of the base plate, and the limiting groove being disposed on the base plate.

[0014] In some embodiments, in step S1, two lifting lugs are symmetrically designed on the outer side of the bottom sand mold, and the lifting lugs and the tight box groove are respectively designed on different sides of the bottom sand mold; two lifting lugs are symmetrically designed on the outer side of the top sand mold; and two lifting lugs are symmetrically designed on the outer side of the middle sand mold. In step S3, the lifting lugs and the clamping rods are respectively assembled on different sides of the combined casting mold.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention vertically divides a 3D-printed sand mold into multiple parts. The outer wall of the bottom sand mold is thickened, and locking grooves are designed in the thickened portions of the two symmetrical outer walls of the bottom sand mold. Each locking groove includes a vertical section penetrating the top surface of the bottom sand mold and a limiting section connecting to the bottom end of the bottom sand mold in the middle. A clamping rod with its bottom end matching the shape of the locking groove is installed in each locking groove, and a clamping frame is installed above the top sand mold. The top ends of all clamping rods pass through the clamping frame and are threadedly tightened with clamping nuts, locking the bottom sand mold, the top sand mold, and all the intermediate sand molds into a combined casting mold. This solves the problem of difficult assembly of 3D-printed sand molds in scenarios where a sand box that can completely cover the sand mold is unavailable, and addresses the issue that a sand box that completely covers the sand mold increases manufacturing costs and extends the manufacturing cycle. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a three-dimensional view of a combined casting mold made by a sand-free box forming method based on sand mold 3D printing in a specific embodiment of the present invention. Figure 2 for Figure 1 Enlarged view of region A in the middle; Figure 3 This is a cross-sectional view of a combined mold made by a sand-free box forming method based on sand mold 3D printing in a specific embodiment of the present invention. Figure 4 This is a schematic diagram of the clamping rod in a specific embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the second boss in a specific embodiment of the present invention; Figure 6 A schematic diagram illustrating the metal sealing strip in a specific embodiment of the present invention; Figure 7 This is a schematic diagram illustrating the limiting groove in a specific embodiment of the present invention; Figure 8 This is a schematic diagram of the bottom sand mold in a specific embodiment of the present invention; Figure 9 This is an assembly cross-sectional view of the combined mold and tray manufactured by the sandless box forming method based on sand mold 3D printing in a specific embodiment of the present invention. Figure 10 This is a top view of the assembled combined mold and tray made by a sandless box forming method based on sand mold 3D printing in a specific embodiment of the present invention.

[0017] In the diagram: 11. Bottom sand mold; 111. Lifting port; 112. Horizontal sprue; 113. First vertical sprue; 114. Mounting groove; 115. First groove; 116. Locking groove; 1161. Vertical section; 1162. Limiting section; 12. Top sand mold; 121. Riser; 13. Middle sand mold; 131. Second vertical sprue; 132. Limiting groove; 133. Second boss; 134. Slot sprue; 135. Cavity; 136. Sealing groove; 14. Sand core; 15. Lifting lug; 16. Blind hole; 21. Tightening rod; 22. Tightening frame; 221. Base plate; 2211. Limiting groove; 222. Vertical plate; 23. Tightening nut; 24. Gasket; 3. Metal sealing strip; 4. Support box; 41. Lifting hook; 42. Lifting through hole; 5. Sealing sand mold. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0020] The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] like Figure 1-10The diagram shown is a schematic representation of a composite mold manufactured using a sand-free mold forming method based on sand mold 3D printing in a preferred embodiment of the present invention. In an illustrative embodiment of the sand-free mold forming method based on sand mold 3D printing of the present invention, the sand-free mold forming method based on sand mold 3D printing includes at least: S1. Model Design: Multiple parting surfaces are set on the three-dimensional model of the sand mold to divide the three-dimensional model of the sand mold into a bottom sand mold 11, a top sand mold 12, multiple middle sand molds 13 and a sand core 14; the outer side wall of the bottom sand mold 11 is thickened, and locking grooves 116 are designed on the thickened part of the two symmetrical outer side walls of the bottom sand mold 11. The locking groove 116 includes a vertical section 1161 that penetrates the top surface of the bottom sand mold 11 and a limiting section 1162 that connects to the bottom end of the bottom sand mold 11 in the middle. S2. Assembly preparation: 3D print the bottom sand mold 11, the top sand mold 12, the middle sand mold 13 and the sand core 14; prefabricate the clamping rod 21, the clamping frame 22 and the clamping nut 23; the bottom end of the clamping rod 21 matches the shape of the locking groove 116; S3. Assemble the sand mold: Place the bottom sand mold 11 on the molding base plate 221, and apply box-fitting adhesive to the upper surface of the bottom sand mold 11. The intermediate sand mold 13 is stacked onto the bottom sand mold 11. During the stacking process, the sand core 14 is positioned inside the intermediate sand mold 13, and the parting surfaces of two adjacent intermediate sand molds 13 are coated with bonding adhesive. Apply sealing adhesive to the upper surface of the uppermost middle sand mold 13, and then close the top sand mold 12; One of the clamping rods 21 is installed in each locking groove 116, and the clamping frame 22 is placed on the upper surface of the top sand mold 12; the top ends of all the clamping rods 21 pass through the clamping frame 22 and are threadedly tightened with the clamping nut 23 to lock the bottom sand mold 11, the top sand mold 12 and all the middle sand molds 13 into a combined casting mold.

[0023] The aforementioned sandless box forming method based on sand mold 3D printing involves longitudinally dividing the 3D printed sand mold into multiple parts. A thickening design is made on the outer wall of the bottom sand mold 11. Locking grooves 116 are designed on the thickened portions of the two symmetrical outer walls of the bottom sand mold 11. Each locking groove 116 includes a vertical section 1161 penetrating the top surface of the bottom sand mold 11 and a limiting section 1162 connecting the bottom end of the bottom sand mold 11 in the middle. Each locking groove 116 contains a bottom end that matches the shape of the locking groove 116. Matching clamping rods 21, and clamping frame 22 set above top sand mold 12; the top ends of all clamping rods 21 pass through clamping frame 22 and are threadedly tightened with clamping nut 23, locking the bottom sand mold 11, the top sand mold 12 and all the middle sand molds 13 into a combined casting mold, so as to solve the problem of difficult assembly of 3D printed sand mold in the scenario where there is no sand box that can completely cover the sand mold, and the problem that a sand box that completely covers the sand mold will increase the sand mold manufacturing cost and extend the manufacturing cycle.

[0024] In some embodiments, due to the large filling area of ​​the horizontal sprue 112, a parting surface is provided above the horizontal sprue 112 to prevent the alloy liquid from overflowing from the parting surface under pressure. The bottom sand mold 11 is designed with a riser 111, a horizontal sprue 112, and a first sprue 113 from bottom to top. The bottom middle sand mold 13 is designed with a second sprue 131 connected to the first sprue 113; the remaining middle sand molds 13 are designed with a sprue 134 connected to the second sprue 131, and a cavity 135 connected to the sprue 134; the bottom surface of the top sand mold 12 is designed with a riser 121 connected to the sprue 134 to disperse the filling pressure of the top parting surface.

[0025] In some embodiments, the upper surface of the bottom sand mold 11 is provided with a mounting groove 114 for accommodating a filter screen. The filter screen is located at the junction of the first sprue 113 and the second sprue 131, so that the weight of the lowermost middle sand mold 13 can fix the filter screen between the bottom sand mold 11 and the middle sand mold 13. The filter screen is used to intercept non-metallic impurities such as oxides, slag, and bubbles in the alloy liquid, reducing defects such as porosity and slag holes in the casting, and improving the density and surface quality of the casting. After the filter screen is placed in the mounting groove 114, the upper surface of the bottom sand mold 11 is coated with bonding adhesive to enhance the connection strength between the filter screen and the bottom sand mold 11.

[0026] In some embodiments, in step S2, a top-opening tray 4 is prefabricated based on the model designed in S1, and the bottom plate of the tray 4 is provided with a liquid-lifting through hole 42; in step S3, the bottom of the combined mold is placed inside the tray 4, and the liquid-lifting through hole 42 is connected to the liquid-lifting port 111; sand and binder are filled between the tray 4 and the combined mold, and the sand and binder harden to form a sealing sand mold 5, the top surface of which is higher than half the height of the bottom middle sand mold 13. The bottom sand mold 11 has the most channels and the most complex stress. Setting the sealing sand mold 5 can significantly reduce the structural reliability of the bottom sand mold 11, improve the sealing effect of the parting surface between the bottom sand mold 11 and the bottom middle sand mold 13, and ensure the structural strength and sealing performance of the combined mold during the casting process.

[0027] Furthermore, hooks 41 are provided on both sides of the pallet 4 to connect to lifting equipment for hoisting the pallet 4.

[0028] Furthermore, the box body of the tray 4 is constructed by welding steel plates, and the hook 41 is welded to the box body.

[0029] Furthermore, a first sealing layer is provided between the bottom surface of the combined casting mold and the bottom plate of the tray 4, and the liquid lifting through hole 42 is connected to the liquid lifting port 111.

[0030] Furthermore, the thickness of the first sealing layer is less than or equal to 1 mm. The first sealing layer is made of asbestos.

[0031] Furthermore, the first sealing layer is made of asbestos rope.

[0032] A composite mold, manufactured using a sand-based 3D printing method without a sandbox, is used for differential pressure casting or low-pressure casting. Its pouring gate is located at the bottom of the mold, and molten metal is introduced into the mold through a riser pipe. Gravity allows the molten metal to evenly fill the cavity, facilitating subsequent feeding operations. A second sealing layer, 1mm to 2mm thick, is installed between the bottom surface of the tray 4 and the partition plate in the differential pressure or low-pressure casting equipment. The second sealing layer is made of asbestos.

[0033] In some embodiments, the bottom surface of the sand core 14 in step S1 is designed with a limiting boss, and the upper surface of the lowest sand mold 13 is designed with a limiting groove 132 that matches the limiting boss. In step S3, after applying the sealing adhesive into the limiting groove 132, the limiting boss is then inserted into the limiting groove 132. The positioning of the sand core 14 on the lowest middle sand mold 13 is achieved by the cooperation of the limiting boss and the limiting groove 132.

[0034] Furthermore, the bottom edge of the sidewall of the limiting boss is inclined towards the center of the limiting boss and fits against the sidewall of the limiting groove 132. The inclined sidewall helps guide the limiting boss into the limiting groove 132. When the sand core 14 is a body of revolution, the limiting boss is preferably designed as a truncated cone that is wider at the top and narrower at the bottom, so as to facilitate the insertion of the limiting boss into the limiting groove 132. If the horizontal cross-section of the limiting boss is polygonal, the side edges of the limiting boss are rounded to facilitate the insertion of the limiting boss into the limiting groove 132.

[0035] In some embodiments, in step S1, the parting surfaces of two adjacent medium sand molds 13 are designed with frame-shaped sealing grooves 136, and the portions of the medium sand molds 13 used for flowing liquid metal are all located inside the sealing grooves 136. The prefabricated metal sealing strip 3 in S2; In step S3, when stacking the intermediate sand molds 13, a sealing adhesive is applied to the surface of the metal sealing strips 3. Multiple metal sealing strips 3 are then partially inserted into the sealing grooves 136 below the parting surface of the intermediate sand molds 13, with the sealing adhesive applied to their lower surfaces. The intermediate sand molds 13 with the sealing adhesive applied are then stacked onto the intermediate sand molds 13 containing the metal sealing strips 3, so that the remaining portions of the metal sealing strips 3 are embedded in the sealing grooves 136 above the parting surface of the intermediate sand molds 13. The cooperation between the metal sealing strips 3 and the upper and lower sealing grooves 136 improves the sealing performance between adjacent intermediate sand molds 13, further reducing the possibility of molten alloy overflowing from the parting surfaces of adjacent intermediate sand molds 13 under pressure.

[0036] Furthermore, the metal sealing strip 3 is linear, with a simple shape that is easy to process. The horizontal cross-section of the sealing groove 136 is a square frame, which easily matches the linear metal sealing strip 3.

[0037] In other embodiments, if a metal sealing strip 3 is unavailable on-site, matching sealing bosses and sealing grooves can be provided on the parting surfaces of two adjacent medium sand molds 13. The positioning between the two adjacent medium sand molds 13 is achieved by the cooperation of the sealing bosses and sealing grooves. At the same time, the contact area between the two adjacent medium sand molds 13 is increased, improving the sealing effect between them and further reducing the possibility of molten alloy overflowing from the parting surface between them under pressure.

[0038] Furthermore, the sidewall of the sealing boss slopes towards the center of the sealing boss from the edge away from the sand mold 13, and fits against the sidewall of the sealing groove. The sloped sidewall helps guide the sealing boss into the sealing groove. The horizontal cross-section of the sealing boss is polygonal, and the side edges of the sealing boss are rounded to facilitate the insertion of the sealing boss into the sealing groove.

[0039] In some embodiments, the uppermost intermediate sand mold 13 in step S1 has a first boss on its upper surface, and the bottom surface of the top sand mold 12 has a first groove 115 that matches the first boss. The engagement of the first boss and the first groove 115 positions the intermediate sand mold 13 on the bottom sand mold 11. This also increases the contact area between the intermediate sand mold 13 and the bottom sand mold 11, improving the sealing effect and further reducing the possibility of molten alloy overflowing from the parting surface under pressure. The lowermost intermediate sand mold 13 has a second boss 133 on its bottom surface, and the upper surface of the bottom sand mold 11 has a second groove that matches the second boss 133. The engagement of the second boss 133 and the second groove positions the top sand mold 12 on the intermediate sand mold 13. This also increases the contact area between the intermediate sand mold 13 and the top sand mold 12, improving the sealing effect and further reducing the possibility of molten alloy overflowing from the parting surface under pressure.

[0040] Furthermore, the bottom edge of the sidewall of the first boss slopes towards the center of the first boss and fits against the sidewall of the first groove 115. The sloped sidewall helps guide the first boss into the first groove 115. The horizontal cross-section of the first boss is polygonal, and the side edges of the first boss are rounded to facilitate insertion into the first groove 115. The bottom edge of the sidewall of the second boss 133 slopes towards the center of the second boss 133 and fits against the sidewall of the second groove. The sloped sidewall helps guide the second boss 133 into the second groove. The horizontal cross-section of the second boss 133 is polygonal, and the side edges of the second boss 133 are rounded to facilitate insertion into the second groove.

[0041] In some embodiments, two locking grooves 116 symmetrically located on both sides of the bottom sand mold 11 form a group, and multiple groups of locking grooves 116 are provided, with each group of locking grooves 116 corresponding to one locking groove 116; each end of the locking groove 116 is provided with a limiting groove 2211, and the two symmetrically installed clamping rods 21 move towards each other and enter the limiting grooves 2211 at both ends of the clamping frame 22, and are then threadedly tightened with the clamping nut 23. The clamping rods 21 can quickly enter and exit the clamping frame 22 from the horizontal slot of the limiting groove 2211, thereby improving the installation efficiency of the clamping rods 21 on the clamping frame 22.

[0042] In some embodiments, the clamping frame 22 includes a base plate 221 and two upright plates 222 formed on the upper surface of the base plate 221. The structure is simple, easy to process, and inexpensive. The two upright plates 222 are located on opposite sides of the base plate 221 to improve the structural strength of the clamping frame 22. The limiting groove 2211 is provided on the base plate 221.

[0043] In some embodiments, the top end of the clamping rod 21 passes sequentially through the clamping frame 22 and the washer 24 before being tightened with the clamping nut 23.

[0044] In some embodiments, the axis of the limiting segment 1162 in S1 is a horizontal straight line. The top and bottom surfaces of the limiting segment 1162 are both horizontal and fit against the clamping rod 21. After the clamping rod 21 passes through the clamping frame 22 and is tightened with the clamping nut 23, the cooperation between the top and bottom surfaces of the limiting segment 1162 and the clamping rod 21 can effectively reduce the possibility of the clamping rod 21 disengaging from the locking groove 116. When prefabricating the clamping rod 21 in S2, the clamping rod 21 is designed and manufactured based on the depth of the locking groove 116 to ensure that the bottom end of the clamping rod 21 is completely submerged in the locking groove 116 in the horizontal direction.

[0045] Furthermore, after the clamping rod 21 passes through the clamping frame 22 and is tightened with the clamping nut 23, in the normal direction of the side wall of the bottom sand mold 11 where the locking groove 116 is located, the horizontal distance between the side wall of the clamping rod 21 away from the sand core 14 and the groove of the locking groove 116 on the side wall of the bottom sand mold 11 is greater than or equal to half the width of the bottom end of the clamping rod 21, so as to further reduce the possibility of the clamping rod 21 disengaging from the locking groove 116.

[0046] In some embodiments, in step S1, two lifting lugs 15 are symmetrically designed on the outer side of the bottom sand mold 11, and the lifting lugs 15 and the clamping groove are respectively designed on different sides of the bottom sand mold 11. Two lifting lugs 15 are symmetrically designed on the outer side of the top sand mold 12, and two lifting lugs 15 are symmetrically designed on the outer side of the middle sand mold 13. In step S3, the hook of the hoisting equipment can hook the two symmetrical lifting lugs 15 to help move and stack the bottom sand mold 11, the middle sand mold 13 and the top sand mold 12, thereby improving the assembly efficiency of the combined mold.

[0047] In step S3, the lifting lug 15 and the clamping rod 21 are respectively assembled on different sides of the combined casting to avoid the lifting lug 15 interfering with the installation of the clamping rod 21.

[0048] Furthermore, the lifting lug 15 includes a limiting part and a connecting part. The connecting part is designed on the side wall of the combined casting, and the limiting part is designed at the end of the connecting part away from the combined casting. The connecting part is used to hook the hook of the lifting equipment, and the limiting part is used to prevent the hook from disengaging from the connecting part.

[0049] In some embodiments, in step S3, each parting surface of the sand mold is embedded with multiple locating pins to align the various parts of the sand mold during stacking.

[0050] During the stacking process, the lower half of the positioning pin is buried in the bottom sand mold 11 or the corresponding middle sand mold 13. Then, the corresponding middle sand mold 13 or the top sand mold 12 is stacked on the positioning pin. With the help of the gravity of the sand mold, the upper half of the positioning pin is inserted into the corresponding middle sand mold 13 or the top sand mold 12.

[0051] Furthermore, the step of applying the sealing adhesive precedes the step of embedding the lower half of the positioning pin into the bottom sand mold 11 or the corresponding middle sand mold 13, in order to enhance the connection strength between the positioning pin and the combined mold.

[0052] In some embodiments, a third sealing layer is provided on the parting surface of the sand mold to improve the sealing effect between the various parts of the sand mold.

[0053] Furthermore, the thickness of the third sealing layer is less than or equal to 1 mm to reduce the impact of the third sealing layer on the shape accuracy of cavity 135.

[0054] Furthermore, the third sealing layer is made of asbestos.

[0055] Furthermore, the third sealing layer is made of asbestos rope.

[0056] In some embodiments, the thickness of the sealing adhesive does not exceed 0.3 mm to avoid affecting the sealing effect.

[0057] In some embodiments, a chill is also provided on the medium sand mold 13 in step S3.

[0058] In some embodiments, after the bottom sand mold 11, the top sand mold 12 and all the middle sand molds 13 are locked into a combined mold, a ballast iron can be provided on the top surface of the top sand mold 12 to increase the weight of the top of the combined mold and improve the overall sealing of the sand mold.

[0059] like Figure 1-10 The diagram shown is a schematic of a combined casting mold made by a sandless box forming method based on sand mold 3D printing in a preferred embodiment of the present invention, wherein the bottom sand mold 11, the top sand mold 12 and the middle sand mold 13 each have four outer sides.

[0060] This sand-free box forming method based on sand mold 3D printing has all the technical features described in the above embodiments except for the sealing boss and sealing groove, and its steps include: S1. Model Design: Multiple parting surfaces are set on the 3D model of the sand mold to divide the 3D model of the sand mold into a bottom sand mold 11, a top sand mold 12, multiple middle sand molds 13, and a sand core 14. The bottom sand mold 11 has a riser 111, a horizontal runner 112, and a first sprue 113. The bottom middle sand mold 13 has a second sprue 131 connected to the first sprue 113. The remaining middle sand molds 13 have a sprue 134 connected to the second sprue 131, and a cavity 135 connected to the sprue 134. The bottom surface of the top sand mold 12 has a riser 121 connected to the sprue 134. Then, the mounting groove 114, the limiting boss, the limiting groove 132, the sealing groove 136, the first boss, the first groove 115, the second boss 133, the second groove, the lifting lug 15, and the blind hole 16 for matching positioning pins are designed for 3D printing. The outer wall of the bottom sand mold 11 is thickened, and locking grooves 116 are designed in the thickened part of the two symmetrical outer walls of the bottom sand mold 11.

[0061] S2. Assembly preparation: 3D print the bottom sand mold 11, the top sand mold 12, the middle sand mold 13 and the sand core 14; pre-install positioning pins, metal sealing strips 3, gaskets 24, clamping rods 21, clamping frame 22, clamping nuts 23 and support boxes 4; S3. Assemble the sand mold: The hoisting equipment hooks the lifting lug 15 of the bottom sand mold 11, places the bottom sand mold 11 on the molding base plate, places the filter screen in the mounting groove 114, applies box-fitting adhesive to the upper surface of the bottom sand mold 11, inserts the positioning pin into the blind hole 16 on the top surface of the bottom sand mold 11, and places a sealing layer made of asbestos rope. Apply sealing adhesive to the bottom surface of the lowest medium sand mold 13. The hoisting equipment hooks onto the lifting lug 15 of the lowest medium sand mold 13 and stacks it onto the bottom sand mold 11. Insert the limiting protrusion into the limiting groove 132.

[0062] The stacking steps for the remaining medium sand molds 13 are as follows: Apply sealing adhesive to the top surface of the lower medium sand mold 13, install the metal sealing strip 3 and positioning pins, place a sealing layer made of asbestos rope, apply sealing adhesive to the bottom surface of the next medium sand mold 13, and use lifting equipment to hook the lifting lugs 15 of the next medium sand mold 13 for stacking. During the stacking process, chills are bonded to the medium sand molds 13.

[0063] The upper surface of the middle sand mold 13 is coated with box-closing adhesive, a positioning pin is installed, and a sealing layer made of asbestos rope is placed. The bottom surface of the top sand mold 12 is coated with box-closing adhesive, and the hoisting equipment hooks the lifting lug 15 of the top sand mold 12 to close the box. One clamping rod 21 is installed in each locking groove 116, and the clamping frame 22 is placed on the upper surface of the top sand mold 12; the top ends of all the clamping rods 21 pass through the clamping frame 22 and are threadedly tightened with the clamping nut 23 to lock the bottom sand mold 11, the top sand mold 12, and all the middle sand molds 13 into a combined casting mold. Subsequently, a ballast is placed on the top surface of the top sand mold 12.

[0064] The iron slab, the chiller, the positioning pin, the box fitting adhesive, the first sealing layer, the second sealing layer, and the third sealing layer are not shown in the figure, but are described in the text.

[0065] Based on the bottom shape of the combined mold, a positioning frame is drawn on the bottom surface of the inner side of the tray 4. A first sealing layer is laid inside the positioning frame. The hoisting equipment hooks the clamping rod 21 or the clamping frame 22, and places the combined mold inside the tray 4, aligning it with the positioning frame so that the liquid lifting through hole 42 connects to the liquid lifting port 111. Sand and adhesive are filled between the tray 4 and the combined mold. After the sand and adhesive harden, they form a sealing sand mold 5. The top surface of the sealing sand mold 5 is higher than half the height of the lowest intermediate sand mold 13. A second sealing layer is provided between the bottom surface of the tray 4 and the partition plate in the differential pressure casting equipment or low-pressure casting equipment.

[0066] Through the description of several embodiments of the sandless box forming method based on sand mold 3D printing of the present invention, it can be seen that the embodiments of the sandless box forming method based on sand mold 3D printing of the present invention have at least the following advantages: This invention vertically divides a 3D-printed sand mold into multiple parts. The outer wall of the bottom sand mold is thickened, and locking grooves are designed in the thickened portions of the two symmetrical outer walls of the bottom sand mold. Each locking groove includes a vertical section penetrating the top surface of the bottom sand mold and a limiting section connecting to the bottom end of the bottom sand mold in the middle. A clamping rod with its bottom end matching the shape of the locking groove is installed in each locking groove, and a clamping frame is installed above the top sand mold. The top ends of all clamping rods pass through the clamping frame and are threadedly tightened with clamping nuts, locking the bottom sand mold, the top sand mold, and all the intermediate sand molds into a combined casting mold. This solves the problem of difficult assembly of 3D-printed sand molds in scenarios where a sand box that can completely cover the sand mold is unavailable, and addresses the issue that a sand box that completely covers the sand mold increases manufacturing costs and extends the manufacturing cycle.

[0067] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A sand-free box forming method based on sand mold 3D printing, characterized in that, include: S1. Model Design: The three-dimensional model of the sand mold is divided into a bottom sand mold, a top sand mold, multiple middle sand molds, and a sand core. The outer side wall of the bottom sand mold is thickened. Locking grooves are designed in the thickened parts of the two symmetrical outer side walls of the bottom sand mold. The locking grooves include a vertical section that penetrates the top surface of the bottom sand mold and a limiting section that connects to the bottom end of the bottom sand mold in the middle. S2. Assembly preparation: 3D print the bottom sand mold, the top sand mold, the middle sand mold, and the sand core; prefabricate the clamping rod, the clamping frame, and the clamping nut; the bottom end of the clamping rod matches the shape of the locking groove; S3. Assemble the sand mold: Place the bottom sand mold on the molding base plate and apply box-fitting adhesive to the upper surface of the bottom sand mold; The intermediate sand mold is stacked onto the bottom sand mold. During the stacking process, the sand core is positioned inside the intermediate sand mold, and a bonding adhesive is applied to the parting surface of two adjacent intermediate sand molds. Apply sealing adhesive to the upper surface of the top sand mold and close the top sand mold; One of the clamping rods is installed in each locking groove, and the clamping frame is placed on the upper surface of the top sand mold; the top ends of all the clamping rods pass through the clamping frame and are screwed into the clamping nut to lock the bottom sand mold, the top sand mold and all the middle sand molds into a combined casting mold.

2. The sand-free box forming method based on sand mold 3D printing according to claim 1, characterized in that, The bottom sand mold is designed with a riser, a horizontal runner, and a first sprue from bottom to top; the bottom middle sand mold is designed with a second sprue that connects to the first sprue; the remaining middle sand molds are designed with a sprue that connects to the second sprue, and a cavity that connects to the sprue; the bottom surface of the top sand mold is designed with a riser that connects to the sprue.

3. The sand-free box forming method based on sand mold 3D printing according to claim 2, characterized in that, The upper surface of the bottom sand mold is provided with an installation groove for accommodating the filter screen, which is located at the junction of the first sprue and the second sprue; after the filter screen is placed in the installation groove, the upper surface of the bottom sand mold is then coated with a sealing adhesive.

4. The sand-free box forming method based on sand mold 3D printing according to claim 2, characterized in that, In step S2, a top-opening tray is prefabricated based on the model designed in S1. Hooks are provided on both sides of the tray, and a liquid-lifting through hole is provided on the bottom plate of the tray. In step S3, the bottom of the combined mold is placed inside the tray. A first sealing layer is provided between the bottom surface of the combined mold and the bottom plate of the tray. The liquid-lifting through hole is connected to the liquid-lifting port. Sand and binder are filled between the tray and the combined mold. After the sand and binder harden, they form a sealing sand mold. The top surface of the sealing sand mold is higher than half the height of the bottommost middle sand mold.

5. The sandless box forming method based on sand mold 3D printing according to any one of claims 1-4, characterized in that, In step S1, the bottom surface of the sand core is designed with a limiting boss, and the upper surface of the bottommost medium sand mold is designed with a limiting groove that matches the limiting boss. In step S3, after applying the sealing adhesive into the limiting groove, the limiting boss is then inserted into the limiting groove.

6. The sandless box forming method based on sand mold 3D printing according to any one of claims 1-4, characterized in that, In step S1, the parting surfaces of two adjacent medium sand molds are designed with frame-shaped sealing grooves, and the part of the medium sand mold used for flowing liquid metal is located inside the sealing groove. The prefabricated metal sealing strip in S2; In step S3, when stacking the medium sand mold, a box-fitting adhesive is applied to the surface of the metal sealing strip. Multiple metal sealing strips are inserted end-to-end into the sealing groove below the parting surface of the medium sand mold. The medium sand mold with the box-fitting adhesive on its lower surface is stacked onto the medium sand mold with the metal sealing strip embedded in it, so that the remaining part of the metal sealing strip is embedded in the sealing groove above the parting surface of the medium sand mold.

7. The sandless box forming method based on sand mold 3D printing according to claim 6, characterized in that, In step S1, the uppermost middle sand mold has a first protrusion on its upper surface, and the bottom surface of the top sand mold has a first groove that matches the first protrusion; the bottom surface of the lowest middle sand mold has a second protrusion, and the upper surface of the bottom sand mold has a second groove that matches the second protrusion.

8. The sandless box forming method based on sand mold 3D printing according to any one of claims 1-4, characterized in that, Two locking grooves symmetrically located on both sides of the bottom sand mold form a group, and multiple groups of locking grooves are provided. Each locking groove in the same group corresponds to one locking groove. A limiting groove is provided at each end of the locking groove. After the two symmetrically installed clamping rods move towards each other and enter the limiting grooves at both ends of the clamping frame, they are screwed tightly with the clamping nut.

9. The sand-free box forming method based on sand mold 3D printing according to claim 8, characterized in that, The clamping frame includes a base plate and two upright plates formed on the upper surface of the base plate. The two upright plates are respectively located on both sides of the base plate, and the limiting groove is provided on the base plate.

10. The sandless box forming method based on sand mold 3D printing according to any one of claims 1-4, characterized in that, In step S1, two lifting lugs are symmetrically designed on the outer side of the bottom sand mold, and the lifting lugs and the tight box groove are respectively designed on different sides of the bottom sand mold. Two lifting lugs are symmetrically designed on the outer side of the top sand mold, and two lifting lugs are symmetrically designed on the outer side of the middle sand mold. In step S3, the lifting lugs and the clamping rods are respectively assembled on different sides of the combined casting mold.

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