Device and method for 3D printing clay sand casting mold

Abstract

A device and method for 3D printing clay sand casting, comprising: a computer and control system, a forming system, a powder spreading system, and a clay sand casting; the computer and control system are connected to the forming system and the powder spreading system, the forming system is arranged on the upper part of the powder spreading system, and the clay sand casting is arranged in the middle of the powder spreading system. In the forming system, the solution injection system and the solvent injection system are connected to the solution injection system moving device, and the solution injection system, the solution injection system moving device and the drying system are connected to the forming system moving device. In the powder spreading system, the powder is located above the bottom plate of the forming area and the bottom plate of the powder replenishing area, the bottom plate lifting device of the forming area is connected to the bottom plate of the forming area, the bottom plate lifting device of the powder replenishing area is connected to the bottom plate of the powder replenishing area, and the powder spreading device is installed between the solution injection system and the drying system, and is connected to the forming system moving device. The method adopted by the casting can maintain the characteristics of low air permeability and low gas emission, and reduce the possibility of pores in the casting.

Description

Technical Field

[0001] The invention belongs to the technical field of casting, and relates to a device and method for 3D printing clay sand casting molds. Background Art

[0002] At present, in the existing technology, the common method for quickly manufacturing castings based on 3D printing (layered manufacturing technology) is basically to spray resin binder and curing agent, and then bond the molding sand together to form a resin sand casting.

[0003] The specific method of layered manufacturing of this resin sand casting mold is to decompose the object to be processed into multiple parallel thin layers, manufacture these thin layers layer by layer and stack them to complete the manufacturing process of the entire casting mold. There are two common manufacturing methods: one is to selectively sinter the resin coated sand with a laser. The basic method adopted is: lay a layer of resin coated sand on the workbench, heat it to a temperature slightly lower than the melting point of the resin film, and then use a laser beam to scan according to the shape of the thin layer. The resin film on the surface of the scanned coated sand is first melted and then solidified, and the coated sand is bonded into one body, thereby forming a thin layer entity consistent with the scanned shape. Then, another layer of coated sand is laid on top of the entity, with a thickness consistent with the thickness of the thin layer, and then the laser selective sintering of the next thin layer is performed. The newly formed thin layer is also bonded to the previous thin layer through the sintering process, and the manufacturing of the entire resin sand casting is completed by thin layer by layer. The disadvantages of this method are that the resin sand casting has a large amount of gas generation, high manufacturing cost, low manufacturing efficiency, high difficulty in cleaning and sand removal of castings, and the resin will cause solid and gas pollution to the environment.

[0004] The other method is to use a nozzle to spray the curing agent or resin on the molding sand covered with resin or curing agent, and then selectively solidify and form it. The basic method is: lay a layer of molding sand covered with resin or curing agent on the workbench, use a nozzle to spray the curing agent or resin on the molding sand surface according to the shape of the thin layer, and the mold sand sprayed will undergo a curing reaction and bond into one body, thereby forming a thin layer entity consistent with the scanned shape. Then, lay another layer of molding sand covered with resin or curing agent on top of the entity, and its thickness is consistent with the thickness of the thin layer, and then selectively spray the next thin layer. The newly formed thin layer is also bonded to the previous thin layer through the curing action, and the thin layer is manufactured layer by layer until the entire resin sand casting is completed. The disadvantages of this method are that the resin sand casting has a large amount of gas emission, high raw material cost, high difficulty in cleaning and removing sand from the casting, and the resin will cause solid and gas pollution to the environment.

[0005] Since the above method uses resin to manufacture the casting, there are problems such as high raw material cost, poor disintegration and difficulty in cleaning the casting. In addition, for castings with higher surface quality requirements, it is often required to use finer molding sand in the casting process, and more resin needs to be added. The fine sand casting has a high resin content, which not only further increases the difficulty of cleaning the casting, but also the poor air permeability of this casting. The resin inside will decompose to produce more gas. These gases enter the liquid metal to form pore defects. The problem of scrapping castings due to pore defects is very prominent.

[0006] Clay sand castings are currently manufactured by mold making methods, which have the advantages of low gas emission and low raw material cost. Fine sand is used to make castings with high surface quality, which can maintain the characteristics of low permeability and low gas emission, and reduce the possibility of pores in castings. The method of making clay sand castings by molds requires mixing molding sand, clay and water and then curing them into shape. The currently disclosed resin sand 3D printing equipment is only for resin sand castings, and the curing means uses resin and curing agent instead of clay and water. Using resin sand 3D printing equipment to replace resin and curing agent with clay and water to print clay sand castings cannot meet the normal curing process, and the strength of the printed casting will be very low. In addition to the inadequacy of the equipment, there is also a lack of clay sand casting 3D printing forming methods. Summary of the invention

[0007] In view of the problems existing in 3D printing of resin sand castings, the present invention aims to provide a device for 3D printing of clay sand castings, and a method for using 3D printing of clay sand castings.

[0008] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solution:

[0009] A device for 3D printing clay sand casting molds comprises: a computer and control system, a forming system, a powder spreading system, and a clay sand casting mold; the computer and the control system are respectively connected to the forming system and the powder spreading system, the forming system is arranged on the upper part of the powder spreading system, the forming system can move along the powder spreading direction of the powder spreading system, and the clay sand casting mold is arranged in the middle of the powder spreading system.

[0010] The forming system includes: a solution injection system, a solution injection system mobile device, a drying system and a forming system mobile device; the solution injection system is filled with an aqueous solution, the solution injection system is connected to the solution injection system mobile device, two drying systems are installed on both sides of the solution injection system, and the solution injection system, the solution injection system mobile device and the drying system are all connected to the forming system mobile device.

[0011] The powder spreading system comprises: a forming area bottom plate lifting device, a forming area bottom plate, powder, a powder replenishing area bottom plate lifting device, a powder replenishing area bottom plate and a powder spreading device; the powder is located above the forming area bottom plate and the powder replenishing area bottom plate, the forming area bottom plate lifting device is connected to the forming area bottom plate, the powder replenishing area bottom plate lifting device is connected to the powder replenishing area bottom plate, and the powder spreading device is installed between the solution spraying system and the drying system, and is connected to the forming system moving device.

[0012] 3D printing method of clay sand casting: the powder for making clay sand casting is loaded into the powder spreading system of the equipment for standby use. The powder can be a coated sand powder made by coating a layer of clay film on the surface of the molding sand and then drying it, or it can be a mixed powder made by mixing molding sand and clay. The casting information model to be manufactured is processed by computer sectioning and layering. Using the powder spreading system in the equipment, a layer of powder is first spread on the workbench, and then the computer drives the injection system of the equipment to spray water or water solvent according to the data information of the casting section shape. During this process, the drying system of the equipment quickly dries the surface of the powder layer, and forms the first layer of the casting model in the area where water or aqueous solution is sprayed; after the first layer is formed, the workbench is lowered by one layer height, and then the second layer of powder spreading and injection is carried out. Repeat the above steps until all the slice layers are finally completed. After taking out the entire stack and removing the unsolidified powder, heat curing and dehydration are performed to obtain the desired casting. The specific steps are as follows:

[0013] Step 1: Spread the base powder on the bottom; first, control the lifting device of the bottom plate of the forming area through the computer and control system, lift the bottom plate of the forming area to the top, and the top of the bottom plate of the forming area is located below the bottom of the powder spreading device, and then move the bottom plate of the forming area down by more than 5mm. After the bottom plate of the powder replenishing area at one end of the powder spreading system moves up under the action of the lifting device of the powder replenishing area, the powder spreading device moves to the other end driven by the moving device of the forming system, and spreads the excess powder above the bottom plate of the powder replenishing area to the top of the bottom plate of the forming area. The height of the bottom plate of the powder replenishing area moving up must ensure that the powder spreading device can spread the powder above the bottom plate of the powder replenishing area and the bottom plate of the forming area into a plane;

[0014] Step 2: Spread a single layer of powder; move the bottom plate of the forming area down by 0.2-2 mm, and use the same method as step 1 to spread the powder on the bottom plate of the forming area and the bottom plate of the powder replenishing area into a plane using a powder spreading device. Preferably, the thickness of the powder layer is 0.2-1 mm;

[0015] Step 3: forming a single layer; under the control of a computer and a control system, the solution spraying system moving device and the forming system moving device move in the front-to-back direction and the left-to-right direction respectively, and the solution spraying system sprays the aqueous solution to the casting area according to the cross-sectional shape data information of the layer of the clay casting, and the powder is formed under the solidification effect of water or aqueous solution;

[0016] Step 4: Strengthening of the single layer; the drying system is used to quickly dry the powder surface, and the powder is bonded together during the solidification process of the aqueous solution, and the first single layer is formed under the strengthening of the drying effect; the drying system in this step can dry the aqueous solution sprayed by the mobile device of the solution spraying system in time;

[0017] Step 5: Multi-layer manufacturing; repeat steps 2 to 4 to spread the powder of the next layer, spray water or aqueous solution to solidify and shape, and dry and strengthen the single layer until the stacking is finally completed to form a formed clay sand casting mold;

[0018] Step 6: Take out the formed clay sand casting mold and remove the unsolidified powder. The removed powder can be reused. Put the formed clay sand casting mold in an oven for further heating, solidification and dehydration to obtain the desired casting mold. The preferred heating temperature can be set to 110°C.

[0019] The present invention adopts the above-mentioned technical solution to achieve the following beneficial effects:

[0020] 1. Compared with 3D printed resin sand castings, the clay sand castings remove gas-generating substances such as moisture and volatiles in the binder, so that no gas is generated during the pouring of liquid metal, avoiding the possibility of pores in the castings and significantly improving the yield of complex castings;

[0021] 2. Compared with 3D printed resin sand castings, clay sand castings use clay as a binder and water as a dispersion medium, which is harmless to the human body and environmentally friendly;

[0022] 3. Compared with 3D printed resin sand castings, the raw material clay used as the binder of clay sand castings is cheap and can reduce production costs;

[0023] 4. Compared with the resin sand casting mold of 3D printing, the clay sand casting mold is a clay sand fine sand sand mold made of fine sand, which has the characteristics of high surface quality and low gas emission of the casting mold;

[0024] 5. Compared with 3D printed resin sand castings, clay sand castings have better collapsibility and castings are easy to clean;

[0025] 6. When manufacturing in small batches, compared with the method of making clay sand casting molds by mold making, 3D printed clay sand casting molds do not require molds, so the manufacturing cycle is short and the cost is low;

[0026] 7. When manufacturing in small batches, compared with the method of making clay sand castings by mold making, 3D printed clay sand castings have high precision, no draft angle, and a small number of parting molds in the design process, which can achieve the overall forming of multiple castings. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the working state structure of a device for 3D printing clay sand casting molds of the present invention;

[0028] Figure 2 It is a schematic diagram of the top view of a device for 3D printing clay sand casting molds of the present invention;

[0029] Figure 3 yes Figure 2 Schematic diagram of the AA cross-section structure.

[0030] In the figure: 1. Computer and control system; 2. Forming system; 2-1. Solution injection system; 2-2. Solution injection system moving device; 2-3. Drying system; 2-4. Forming system moving device; 3. Powder spreading system; 3-1. Forming area bottom plate lifting device; 3-2. Forming area bottom plate; 3-3. Powder; 3-4. Powder replenishing area bottom plate lifting device; 3-5. Powder replenishing area bottom plate; 3-6 Powder spreading device; 4. Clay sand casting mold. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0032] like Figures 1 to 3 As shown, a device for 3D printing clay sand casting molds includes: a computer and control system 1, a forming system 2, a powder spreading system 3, and a clay sand casting mold 4; the computer and control system 1 are respectively connected to the forming system 2 and the powder spreading system 3, the forming system 2 is arranged on the upper part of the powder spreading system 3, and the clay sand casting mold 4 is arranged in the middle part of the powder spreading system 3.

[0033] The forming system 2 includes: a solution injection system 2-1, a solution injection system mobile device 2-2, a drying system 2-3 and a forming system mobile device 2-4; the solution injection system 2-1 is filled with water or an aqueous solution, the solution injection system 2-1 is connected to the solution injection system mobile device 2-2, two drying systems 2-3 are installed on both sides of the solution injection system 2-1, and the solution injection system 2-1, the solution injection system mobile device 2-2 and the drying system 2-3 are all connected to the forming system mobile device 2-4.

[0034] The powder spreading system 3 includes: a forming area bottom plate lifting device 3-1, a forming area bottom plate 3-2, powder 3-3, a powder replenishing area bottom plate lifting device 3-4, a powder replenishing area bottom plate 3-5 and a powder spreading device 3-6; the powder 3-3 is located above the forming area bottom plate 3-2 and the powder replenishing area bottom plate 3-5, the forming area bottom plate lifting device 3-1 is connected to the forming area bottom plate 3-2, the powder replenishing area bottom plate lifting device 3-4 is connected to the powder replenishing area bottom plate 3-5, the powder spreading device 3-6 is installed between the solution injection system 2-1 and the drying system 2-3, and is connected to the forming system moving device 2-4, preferably, the powder spreading device 3-6 can use a powder spreading roller or a scraper.

[0035] 3D printing clay sand casting method: the powder 3-3 used to make the clay sand casting 4 is loaded into the powder spreading system 3 in the equipment for standby use. The powder 3-3 can be a coated sand powder made by covering the surface of the molding sand with a layer of clay film and then drying it, or it can be a mixed powder made by mixing the molding sand and clay. The casting information model to be manufactured is subjected to computer sectioning and layering processing. Using the powder spreading system 3 in the equipment, a layer of powder 3-3 is first spread on the workbench, and then the computer and control system 1 drives the solution injection system 2-1 in the equipment to spray water or aqueous solution according to the casting section shape data information. During this process, the drying system 2-3 in the equipment quickly dries the surface of the powder layer, and forms the first layer of the clay sand casting 4 model in the area where the water or aqueous solution is sprayed; after the first layer is formed, the workbench is lowered by one layer height, and then the second layer of powder spreading and injection is carried out. Repeat the above steps until all the slice layers are finally completed. After the entire stack is taken out and the uncured powder is removed, it is heated, cured and dehydrated to obtain the desired casting. The specific steps are as follows:

[0036] Step 1: Spread the base powder on the bottom. First, control the forming area bottom plate lifting device 3-1 through the computer and control system 1, lift the forming area bottom plate 3-2 to the top, and the top of the forming area bottom plate 3-2 is located below the bottom of the powder spreading device 3-6. Then move the forming area bottom plate 3-2 down by more than 5mm. After the powder replenishing area bottom plate 3-5 located at one end of the powder spreading system 3 is moved up to a certain height under the action of the powder replenishing area lifting device 3-4, the powder spreading device 3-6 moves to the other end driven by the forming system moving device 2-4, and spreads the excess powder 3-3 above the powder replenishing area bottom plate 3-5 to the top of the forming area bottom plate 3-2. The height of the powder replenishing area bottom plate 3-5 must ensure that the powder spreading device 3-6 can spread the powder 3-3 above the powder replenishing area bottom plate 3-5 and the forming area bottom plate 3-2 into a plane;

[0037] Step 2: Spread a single layer of powder. The bottom plate 3-2 of the forming area is moved down by 0.2~2mm. The powder 3-3 above the bottom plate 3-2 of the forming area and the bottom plate 3-5 of the powder replenishing area are spread into a plane by the powder spreading device 3-6 in the same way as step 1. Preferably, the thickness of the powder 3-3 layer is 0.2~1mm.

[0038] Step 3: Single-layer forming. Under the control of the computer and control system 1, the solution spraying system moving device 2-2 and the forming system moving device 2-4 move in the front-to-back direction and the left-to-right direction respectively, and the solution spraying system 2-1 sprays water or aqueous solution to the casting area according to the cross-sectional shape data information of the layer of the clay sand casting 4, and the powder 3-3 is formed under the solidification effect of the water or aqueous solution;

[0039] Step 4: Strengthening of the single layer. The drying system 2-3 quickly dries the surface of the powder 3-3, and the powder 3-3 is bonded together during the solidification process of the water or aqueous solution, and the first single layer is formed under the strengthening of the drying effect; the drying system in this step can dry the water or aqueous solution sprayed by the solution spraying system moving device 2-2 in time, and can improve the strength of the mold after forming, while the traditional resin sand casting 3D printing forming process does not require the drying of the resin;

[0040] Step 5: Multi-layer manufacturing. Repeat steps 2 to 4 to spread the powder of the next layer, spray water or aqueous solution to solidify and shape, and dry and strengthen the single layer until the stacking is finally completed to form a formed clay sand casting mold 4;

[0041] Step 6: Take out the formed clay sand casting mold 4 and remove the unsolidified powder 3-3. The removed powder 3-3 can be reused. Put the formed clay sand casting mold 4 in an oven for further heating, solidification and dehydration to obtain the desired casting mold. The preferred heating temperature can be set to 110°C.

[0042] The method for 3D printing clay sand casting, the powder 3-3 is a clay powder covered with refractory sand for casting or a mechanically mixed powder of refractory sand for casting and clay. The refractory sand for casting is quartz sand, ceramsite sand, chromite sand or olivine sand, etc., and the preferred sand particle size is 70 / 140 mesh.

[0043] A method for 3D printing a clay sand casting mold, wherein the liquid used for the injection system is water or a solution mainly composed of water.

[0044] The above technical scheme can directly print out clay sand castings, using clay and aqueous solution as raw materials, and using a drying system to dry the water to achieve solidification and molding and casting strengthening. Compared with the 3D printing resin sand casting method in the background technology, the produced clay sand casting has the advantages of small gas emission and low raw material cost. The process of using fine sand to manufacture high surface quality castings can maintain the characteristics of low permeability and low gas emission, and reduce the possibility of pores in the casting.

[0045] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the scope of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A method for 3D printing a clay sand casting mold, which uses a device for 3D printing a clay sand casting mold, the device comprising: A computer and control system (1), a forming system (2), a powder spreading system (3), and a clay sand casting mold (4); the characteristics are as follows: the computer and control system (1) are connected to the forming system (2) and the powder spreading system (3), respectively; the forming system (2) is arranged on the upper part of the powder spreading system (3); the forming system (2) can move along the powder spreading direction of the powder spreading system (3); the clay sand casting mold (4) is arranged in the middle of the powder spreading system (3); the forming system (2) comprises: a solution injection system (2-1), a solution injection system moving device (2-2), a drying system (2-3) and a forming system moving device (2-4); the solution injection system (2-1) is filled with a solution, the solution injection system (2-1) is connected to the solution injection system moving device (2-2), two drying systems (2-3) are installed on both sides of the solution injection system (2-1), and the solution injection system (2-4) is connected to the solution injection system moving device (2-2). 2-1), the solution injection system moving device (2-2) and the drying system (2-3) are all connected to the forming system moving device (2-4); the powder spreading system (3) comprises: a forming area bottom plate lifting device (3-1), a forming area bottom plate (3-2), powder (3-3), a powder replenishing area bottom plate lifting device (3-4), a powder replenishing area bottom plate (3-5) and a powder spreading device (3-6); the powder (3-3) is located above the forming area bottom plate (3-2) and the powder replenishing area bottom plate (3-5), the forming area bottom plate lifting device (3-1) is connected to the forming area bottom plate (3-2), the powder replenishing area bottom plate lifting device (3-4) is connected to the powder replenishing area bottom plate (3-5), and the powder spreading device (3-6) is installed between the solution injection system (2-1) and the drying system (2-3), and is connected to the forming system moving device (2-4); the specific steps of the method for 3D printing clay sand casting are as follows: Step 1: Spreading base powder on the bottom; first, the forming area bottom plate lifting device (3-1) is controlled by a computer and control system (1) to lift the forming area bottom plate (3-2) to the top, so that the top of the forming area bottom plate (3-2) is located below the bottom of the powder spreading device (3-6), and then the forming area bottom plate (3-2) is moved down by more than 5 mm. After the powder replenishing area bottom plate (3-5) located at one end of the powder spreading system (3) is moved up by the powder replenishing area lifting device (3-4), the powder spreading device (3-6) is moved to the other end driven by the forming system moving device (2-4) to spread the excess powder (3-3) above the powder replenishing area bottom plate (3-5) onto the top of the forming area bottom plate (3-2). The height of the upward movement of the powder replenishing area bottom plate (3-5) must ensure that the powder spreading device (3-6) can spread the powder (3-3) above the powder replenishing area bottom plate (3-5) and the forming area bottom plate (3-2) into a flat surface; Step 2: Spread a single layer of powder; move the bottom plate (3-2) of the forming area downward by 0.2 to 2 mm, and use the same method as step 1 to spread the powder (3-3) above the bottom plate (3-2) of the forming area and the bottom plate (3-5) of the powder replenishing area into a flat surface using a powder spreading device (3-6). The thickness of the powder (3-3) layer is 0.2 ~ 1mm;. Step 3: forming a single layer; under the control of the computer and control system (1), the solution spraying system moving device (2-2) and the forming system moving device (2-4) move in the front-back direction and the left-right direction respectively, and the solution spraying system (2-1) sprays the aqueous solution to the casting area according to the cross-sectional shape data information of the layer of the clay sand casting mold (4), and the powder (3-3) is formed under the solidification effect of the aqueous solution; Step 4: strengthening the single layer; the drying system (2-3) quickly dries the surface of the powder (3-3), and the powder (3-3) is bonded together during the solidification process of the aqueous solution, and the first single layer is formed under the strengthening of the drying effect; the drying system in this step can dry the aqueous solution sprayed by the solution spraying system moving device (2-2) in a timely manner; Step 5: multi-layer manufacturing; repeating steps 2 to 4, spreading the powder of the next layer, spraying the aqueous solution to solidify the mold, and drying and strengthening the single layer, until the stacking is finally completed to form a formed clay sand casting mold (4); Step 6: Take out the formed clay sand casting mold (4), remove the unsolidified powder (3-3), and reuse the removed powder (3-3). Place the formed clay sand casting mold (4) in an oven for further heating, solidification and dehydration to obtain the desired casting mold. The heating temperature is set to 110°C.

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