Manufacturing method of 3DP sand core capable of avoiding fin defect of middle blade of impeller

Abstract

The invention relates to the technical field of impeller casting, in particular to a manufacturing method of a 3DP sand core capable of avoiding the fin defect of middle blades of an impeller, the sand core comprises an upper skin core, a shaft hole runner core and a lower skin core, the upper skin core is connected to the top face of the lower skin core, and the shaft hole runner core is connected between the upper skin core and the lower skin core. The shaft hole runner core comprises a runner core and a shaft hole core, the shaft hole core is fixedly connected in a runner core center hole, and a connecting cylinder is fixedly connected between the outer wall of the shaft hole core and the inner wall of the runner core center hole; the runner core is not segmented any more, a parting surface does not exist, and the fin defect is fundamentally avoided; the runner core and the shaft hole core are fixedly connected through the connecting cylinder to form the integral shaft hole runner core, printing and carrying are convenient, and the number of sand cores is reduced; the size of the produced impeller is accurate, no fin defect exists in the blades and the shaft hole, the use performance is good, and the dynamic balance performance and the static balance performance are excellent.

Description

Technical Field

[0001] The invention relates to the technical field of impeller casting, and in particular to a method for manufacturing a 3DP sand core for avoiding the defect of a seam on a middle blade of an impeller. Background Art

[0002] The impeller is a rotating body with blades that transfer energy to the liquid. Most impeller blades are twisted and backward curved, with large wall thickness deviation and very complex shape. They need to be directly cast and have high requirements for dynamic balance. It is necessary to ensure that the blades have no casting defects.

[0003] In the impeller casting process of the prior art, since the sand core needs to be demolded, the flow channel core and the shaft hole core of the impeller cannot be made as a whole. Generally, a parting surface is set in the middle of the flow channel, which is divided into three sand cores. The three sand cores are flow channel core 1#, flow channel core 2# and shaft hole core. After these sand cores are made separately, they are combined and packed in the order of flow channel core 1# to shaft hole core to flow channel core 2#. The combination of the three sand cores in the prior art will result in a parting surface on the outer wall of the flow channel core. During pouring, molten iron will inevitably invade from the parting surface to form a seam defect. Since the impeller blade structure extends from the outer cylindrical surface to the center of the impeller, the seams attached to the blades are extremely difficult to clean, and the remaining seams will have an adverse effect on the performance of the impeller such as dynamic balance. Summary of the invention

[0004] The purpose of the present invention is to provide a method for manufacturing a 3DP sand core that avoids the gap defects of the middle blades of an impeller, eliminates the parting surface formed on the outer wall of the flow channel core caused by the combination of three sand cores, and prevents the gap defects of the impeller shaft hole and the blades caused by the parting surface.

[0005] The present invention discloses a method for manufacturing a 3DP sand core for avoiding the seam defect of an impeller middle blade. The sand core comprises an upper skin core, an axial hole flow channel core and a lower skin core. The upper skin core is laid on the top surface of the lower skin core, the axial hole flow channel core is connected between the upper skin core and the lower skin core, the axial hole flow channel core comprises a flow channel core and an axial hole core, the axial hole core is fixedly connected in a center hole of the flow channel core, and a connecting cylinder is fixedly connected between an outer wall of the axial hole core and an inner wall of the center hole of the flow channel core.

[0006] Furthermore, the connecting cylinder is provided with two layers, and the two layers of connecting cylinders are arranged at the upper and lower parts of the shaft hole core along the height direction of the shaft hole core. Each layer of connecting cylinders includes multiple connecting cylinders, and the multiple connecting cylinders of each layer are evenly distributed around the circumference with the axis of the shaft hole core as the center.

[0007] Furthermore, a positioning protrusion is provided on the edge of the bottom surface of the flow channel core, and a positioning groove I is provided on the inner bottom surface of the lower skin core, and the positioning protrusion is connected in the positioning groove I; Furthermore, there are two positioning protrusions, which are symmetrical, and there are two positioning grooves I, which are respectively connected to the two positioning grooves I.

[0008] Furthermore, a positioning column extends from the bottom surface of the shaft hole core, the positioning column is coaxial with the shaft hole core, and a positioning groove II is provided at the center of the inner bottom surface of the lower skin core, and the positioning column is connected in the positioning groove II.

[0009] Furthermore, a slope I is provided on the outer wall of the positioning column, and the slope I is inclined toward the axis side of the positioning column. A slope II is provided on the outer wall of the positioning groove II, and the slope II is inclined toward the axis side of the positioning groove II. The slope I is connected to the slope II.

[0010] Furthermore, a through hole is provided at the center of the positioning column, and a through hole is provided at the center of the bottom surface of the positioning groove II. The through hole at the center of the positioning column is coaxial with the through hole at the center of the bottom surface of the positioning groove II.

[0011] Furthermore, the outer wall of the positioning protrusion is provided with an inward drafting, and the inner wall of the positioning groove I is provided with an inward drafting, and the drafting angle of the outer wall of the positioning protrusion is the same as the drafting angle of the inner wall of the positioning groove I.

[0012] Furthermore, the outer wall of the positioning column is provided with an inward drafting, and the inner wall of the positioning groove II is provided with an inward drafting, and the drafting angle of the outer wall of the positioning column is the same as the drafting angle of the inner wall of the positioning groove II.

[0013] The present invention provides a method for manufacturing a 3DP sand core for avoiding the gap defect of the middle blade of an impeller, comprising the following steps: S1. Establish a three-dimensional model of the impeller according to the design parameters, and add conventional casting components such as runners and risers to form a casting process model; S2. Design the overall sand box model, the sand box minus the casting process model formed in step S1 to obtain a hollow sand mold; S3. Split the sand mold into an upper skin core, an axial hole flow channel core and a lower skin core; S4. The outer diameter of the connecting cylinder is designed to be 5mm-10mm, and the flow channel core, the shaft hole core and the connecting cylinder form an integral shaft hole flow channel core; S5. Design a draft surface at the buckle position of the sand mold. The draft surface is located at the parting surface between the upper skin core and the lower skin core, and the draft surface angle is 15°; S6. Design the inner diameter of the through hole at the center of the positioning column and the inner diameter of the through hole at the bottom of the positioning groove II to be 12 mm; S7. Sand mold printing: 100-140 mesh ceramsite sand is used, and the printing layer thickness is 0.28 mm. The upper skin core, shaft hole flow channel core and lower skin core of steps S1-S6 are printed. After printing, compressed air is used to purge the sand inside each sand core, and the shaft hole flow channel core is cleaned in particular; S8. Core coating: Use water-based paint for flow coating, use paint to control the Baume degree 55-80, ensure that there is no flow mark on the surface, the coating thickness is 0.3mm-0.5mm, and place it in a drying kiln for drying after painting, the drying time is 1 hour, and the drying temperature is 150℃-200℃; S9. Assemble the core and close the box: Place the lower skin core on a horizontal ground, take out the axial hole runner core, remove the connecting cylinder in the axial hole runner core, and after the connecting cylinder is removed, the axial hole runner core is divided into a separate runner core and an axial hole core. Connect the separated runner core and the axial hole core in the lower skin core. When connecting the runner core to the lower skin core, ensure that the positioning protrusion is connected to the positioning groove Ⅰ. When connecting the axial hole core to the lower skin core, ensure that the positioning column is connected to the positioning groove Ⅱ. Lift the lower skin core, use an M10 screw and nut to pass through the through hole in the center of the positioning column and the through hole in the center of the bottom surface of the positioning groove Ⅱ, so that the axial hole core and the lower skin core are assembled, and finally connect the upper skin core and the lower skin core to complete the core assembly; S10. After the box is assembled, the mold is dried with a hot air blower. The outlet temperature of the hot air blower is 150℃ and the baking time is 3 hours. Ensure that the temperature in the mold cavity is greater than 100℃ before pouring. Blow argon gas into the mold cavity before pouring. The temperature of the molten iron out of the furnace is 1520℃ and the pouring temperature is 1420℃±10℃.

[0014] The beneficial effects of the present invention are: 1. The runner core of the present invention is no longer divided, and there is no parting surface, which fundamentally avoids the occurrence of seam defects; 2. The present invention uses a connecting cylinder to fix the flow channel core and the shaft hole core to form an integral shaft hole flow channel core, which is convenient for printing and transportation and reduces the number of sand cores; 3. The present invention ensures that the impeller produced has accurate dimensions, no gap defects inside the blades and shaft holes, good performance, and excellent dynamic and static balance performance; 4. The present invention does not require mold production, shortens the production cycle, has high process design flexibility, is not limited by mold processing technology, and is easy to modify and optimize the process, greatly reducing the trial production cost of new product development; 5. The present invention adopts a high-precision industrial-grade printer to print sand molds, and the surface finish and dimensional accuracy of the sand molds are better than those of traditional mold modeling processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is an exploded view of the structure of the present invention; Figure 2 It is a structural schematic diagram of the axial hole flow channel core of the present invention; Figure 3 The top view of the structure of the axial hole flow channel core of the present invention Figure 4 It is a structural schematic diagram of the flow channel core of the present invention; Figure 5 It is a structural schematic diagram of the shaft hole core of the present invention; Figure 6 It is a schematic structural diagram of the lower skin core of the present invention.

[0016] In the figure: 1. upper epidermis core; 2. axial hole flow channel core; 3. lower epidermis core; 4. flow channel core; 5. axial hole core; 6. connecting cylinder; 7. positioning protrusion; 8. positioning column; 801. inclined surface Ⅰ; 9. positioning groove Ⅰ; 10. positioning groove Ⅱ; 1001. inclined surface Ⅱ. DETAILED DESCRIPTION

[0017] like Figure 1-Figure 6 As shown, the sand core in the method for making a 3DP sand core for avoiding the seam defect of the middle blade of an impeller of the present invention includes an upper skin core 1, an axial hole flow channel core 2 and a lower skin core 3, the upper skin core 1 is placed on the top surface of the lower skin core 3, the axial hole flow channel core 2 is connected between the upper skin core 1 and the lower skin core 3, the axial hole flow channel core 2 includes a flow channel core 4 and an axial hole core 5, the axial hole core 5 is fixedly connected in the center hole of the flow channel core 4, and a connecting cylinder 6 is fixedly connected between the outer wall of the axial hole core 5 and the inner wall of the center hole of the flow channel core 4.

[0018] The runner core 4 and the axial hole core 5 of the prior art are designed separately, and the runner core 4 is evenly divided into runner core 1# and runner core 2# along the thickness direction, so a parting surface will appear after the runner core 1# and the runner core 2# are connected together, which will inevitably cause molten iron to invade from the parting surface during pouring, forming a seam defect.

[0019] The runner core 4 in the present invention is no longer divided, and there is no parting surface, which fundamentally avoids the occurrence of seam defects. At the same time, the present invention fixes the runner core 4 and the axial hole core 5 together through the connecting cylinder 6 to form an integral axial hole runner core 2, which is convenient for printing and transportation.

[0020] The connecting cylinder 6 is provided with two layers, and the two layers of connecting cylinders 6 are arranged at the upper and lower parts of the shaft hole core 5 along the height direction of the shaft hole core 5. Each layer of connecting cylinders 6 includes multiple connecting cylinders 6, and the multiple connecting cylinders 6 of each layer are evenly distributed around the circumference with the axis of the shaft hole core 5 as the center.

[0021] The arrangement of two layers of connecting cylinders 6 and the arrangement in which each layer of connecting cylinders 6 includes multiple connecting cylinders 6 improve the connection stability between the flow channel core 4 and the axial hole core 5. In addition, the two layers of connecting cylinders 6 are arranged at the upper and lower parts of the axial hole core 5 along the height direction of the axial hole core 5, so that the connecting cylinders 6 can be removed later when the flow channel core 4 and the axial hole core 5 are separated.

[0022] A positioning protrusion 7 is provided on the bottom edge of the flow channel core 4, and a positioning groove Ⅰ9 is provided on the inner bottom surface of the lower epidermal core 3, and the positioning protrusion 7 is connected in the positioning groove Ⅰ9; there are two positioning protrusions 7, and the two positioning protrusions 7 are symmetrical, and there are two positioning grooves Ⅰ9, and the two positioning protrusions 7 are respectively connected in the two positioning grooves Ⅰ9.

[0023] A positioning column 8 extends from the bottom surface of the shaft hole core 5, and the positioning column 8 is coaxial with the shaft hole core 5. A positioning groove Ⅱ10 is provided at the center of the inner bottom surface of the lower epidermis core 3, and the positioning column 8 is connected in the positioning groove Ⅱ10; a slope Ⅰ801 is provided on the outer wall of the positioning column 8, and the slope Ⅰ801 is inclined toward the axis side of the positioning column 8. A slope Ⅱ1001 is provided on the outer wall of the positioning groove Ⅱ10, and the slope Ⅱ1001 is inclined toward the axis side of the positioning groove Ⅱ10, and the slope Ⅰ801 is connected to the slope Ⅱ1001.

[0024] The arrangement of the positioning protrusion 7 and the positioning groove Ⅰ9 and the arrangement of the positioning column 8 and the positioning groove Ⅱ10 are all for ensuring the accurate positioning of the axial hole flow channel core 2 and the lower skin core 3. The arrangement of the inclined surface Ⅰ801 and the inclined surface Ⅱ1001 further improves the positioning accuracy and also ensures the positioning angle.

[0025] The outer wall of the positioning protrusion 7 is provided with a draft facing inward, and the inner wall of the positioning groove I9 ​​is ​​provided with a draft facing inward, and the draft angle of the outer wall of the positioning protrusion 7 is the same as the draft angle of the inner wall of the positioning groove I9; the outer wall of the positioning column 8 is provided with a draft facing inward, and the inner wall of the positioning groove II10 is provided with a draft facing inward, and the draft angle of the outer wall of the positioning column 8 is the same as the draft angle of the inner wall of the positioning groove II10.

[0026] The setting of the draft plate ensures the convenience of loading and unloading of each positioning component.

[0027] A through hole is provided at the center of the positioning column 8 , and a through hole is provided at the center of the bottom surface of the positioning groove II 10 . The through hole at the center of the positioning column 8 is coaxial with the through hole at the center of the bottom surface of the positioning groove II 10 .

[0028] The arrangement of the through hole at the center of the positioning column 8 and the through hole at the center of the bottom surface of the positioning groove II 10 facilitates the fixing and connection of the shaft hole core 5 and the lower skin core 3 by screws or nuts in subsequent operations.

[0029] The present invention provides a method for manufacturing a 3DP sand core for avoiding the gap defect of the middle blade of an impeller, comprising the following steps: S1. Establish a three-dimensional model of the impeller according to the design parameters, and add conventional casting components such as runners and risers to form a casting process model; S2. Design the overall sand box model, the sand box minus the casting process model formed in step S1 to obtain a hollow sand mold; S3. The sand mold is split and designed into an upper skin core 1, an axial hole flow channel core 2 and a lower skin core 3; S4. Design the outer diameter of the connecting cylinder 6 to be 5mm-10mm, the flow channel core 4, the axial hole core 5 and the connecting cylinder 6 to form an integral axial hole flow channel core 2; S5. Design the draft surface at the sand mold buckle position, the draft surface is located at the parting surface of the upper skin core 1 and the lower skin core 3, and the draft surface angle is 15 °; S6. The inner diameter of the through hole designed for the positioning column 8 and the inner diameter of the through hole at the bottom center of the positioning groove Ⅱ10 are both 12mm; S7. Sand mold printing: 100-140 mesh ceramsite sand is used, and the printing layer thickness is 0.28 mm. The upper skin core 1, the shaft hole flow channel core 2 and the lower skin core 3 of steps S1-S6 are printed. After printing, compressed air is used to purge the loose sand inside each sand core, and the shaft hole flow channel core 2 is cleaned in particular; S8. Core coating: Use water-based paint for flow coating, use paint to control the Baume degree 55-80, ensure that there is no flow mark on the surface, the coating thickness is 0.3mm-0.5mm, and place it in a drying kiln for drying after painting, the drying time is 1 hour, and the drying temperature is 150℃-200℃; S9. Assemble the cores and close the box: place the lower skin core 3 on a horizontal ground, take out the axial hole flow channel core 2, remove the connecting cylinder 6 in the axial hole flow channel core 2, and after the connecting cylinder 6 is removed, the axial hole flow channel core 2 is divided into a separated flow channel core 4 and an axial hole core 5, and the separated flow channel core 4 and the axial hole core 5 are connected to the lower skin core 1. When the flow channel core 4 is connected to the lower skin core 1, it is necessary to ensure that the positioning protrusion 7 is connected to the positioning groove Ⅰ9, and when the axial hole core 5 is connected to the lower skin core 1, it is necessary to ensure that the positioning column 8 is connected to the positioning groove Ⅱ10, and the lower skin core 1 is lifted, and an M10 screw and nut are passed through the through hole in the center of the positioning column 8 and the through hole in the center of the bottom surface of the positioning groove Ⅱ10, so that the axial hole core 5 and the lower skin core 1 are assembled, and finally the upper skin core 1 and the lower skin core 3 are connected to complete the core assembly and close the box; S10. After the box is assembled, the mold is dried with a hot air blower. The outlet temperature of the hot air blower is 150℃ and the baking time is 3 hours. Ensure that the temperature in the mold cavity is greater than 100℃ before pouring. Blow argon gas into the mold cavity before pouring. The temperature of the molten iron out of the furnace is 1520℃ and the pouring temperature is 1420℃±10℃.

Claims

1. A method for manufacturing a 3DP sand core to avoid the gap defect of the middle blade of an impeller, characterized in that: The sand core comprises an upper skin core (1), an axial hole flow channel core (2) and a lower skin core (3); the upper skin core (1) is placed on the top surface of the lower skin core (3); the axial hole flow channel core (2) is connected between the upper skin core (1) and the lower skin core (3); the axial hole flow channel core (2) comprises a flow channel core (4) and an axial hole core (5); the axial hole core (5) is fixedly connected in the center hole of the flow channel core (4); and a connecting cylinder (6) is fixedly connected between the outer wall of the axial hole core (5) and the inner wall of the center hole of the flow channel core (4).

2. A method for manufacturing a 3DP sand core to avoid the gap defect of the middle blade of an impeller according to claim 1, characterized in that: The connecting cylinder (6) is provided with two layers, and the two layers of connecting cylinders (6) are arranged at the upper and lower parts of the shaft hole core (5) along the height direction of the shaft hole core (5), and each layer of connecting cylinders (6) includes a plurality of connecting cylinders (6), and the plurality of connecting cylinders (6) in each layer are evenly distributed around the circumference with the axis of the shaft hole core (5) as the center.

3. The method for manufacturing a 3DP sand core for avoiding the gap defect of the middle blade of an impeller according to claim 2, characterized in that: The bottom edge of the flow channel core (4) is provided with a positioning protrusion (7), the inner bottom surface of the lower skin core (3) is provided with a positioning groove I (9), and the positioning protrusion (7) is connected to the positioning groove I (9).

4. The method for manufacturing a 3DP sand core for avoiding the gap defect of the middle blade of an impeller according to claim 3, characterized in that: There are two positioning protrusions (7), the two positioning protrusions (7) are symmetrical, there are two positioning grooves I (9), and the two positioning protrusions (7) are respectively connected to the two positioning grooves I (9).

5. The method for manufacturing a 3DP sand core for avoiding the gap defect of the middle blade of an impeller according to claim 4, characterized in that: A positioning column (8) extends from the bottom surface of the shaft hole core (5), and the positioning column (8) is coaxial with the shaft hole core (5). A positioning groove II (10) is provided at the center of the inner bottom surface of the lower skin core (3), and the positioning column (8) is connected to the positioning groove II (10).

6. The method for manufacturing a 3DP sand core for avoiding the gap defect of the middle blade of an impeller according to claim 5, characterized in that: The outer wall of the positioning column (8) is provided with an inclined surface I (801), which is inclined toward the axis side of the positioning column (8); the outer wall of the positioning groove II (10) is provided with an inclined surface II (1001), which is inclined toward the axis side of the positioning groove II (10); the inclined surface I (801) is connected to the inclined surface II (1001).

7. A method for manufacturing a 3DP sand core to avoid the gap defect of the middle blade of an impeller according to claim 6, characterized in that: A through hole is provided at the center of the positioning column (8), and a through hole is provided at the center of the bottom surface of the positioning groove II (10). The through hole at the center of the positioning column (8) is coaxial with the through hole at the center of the bottom surface of the positioning groove II (10).

8. A method for manufacturing a 3DP sand core for avoiding the gap defect of the middle blade of an impeller according to any one of claims 3-4, characterized in that: The outer wall of the positioning protrusion (7) is provided with a draft mold facing inwards, and the inner wall of the positioning groove I (9) is provided with a draft mold facing inwards. The draft angle of the outer wall of the positioning protrusion (7) is the same as the draft angle of the inner wall of the positioning groove I (9).

9. A method for manufacturing a 3DP sand core for avoiding the gap defect of the middle blade of an impeller according to any one of claims 5 to 7, characterized in that: The outer wall of the positioning column (8) is provided with a draft pattern facing inwards, and the inner wall of the positioning groove II (10) is provided with a draft pattern facing inwards, and the draft angle of the outer wall of the positioning column (8) is the same as the draft angle of the inner wall of the positioning groove II (10).

10. The method for manufacturing a 3DP sand core for avoiding the gap defect of the middle blade of an impeller according to claim 7, characterized in that: The steps include: S1. Establish a three-dimensional model of the impeller according to the design parameters, and add conventional casting components such as runners and risers to form a casting process model; S2. Design the overall sand box model, the sand box minus the casting process model formed in step S1 to obtain a hollow sand mold; S3. The sand mold is split and designed into an upper skin core (1), an axial hole flow channel core (2) and a lower skin core (3); S4. The outer diameter of the connecting cylinder (6) is designed to be 5 mm to 10 mm, and the flow channel core (4), the shaft hole core (5) and the connecting cylinder (6) form an integral shaft hole flow channel core (2); S5. Design a draft surface at the sand mold buckle position, the draft surface is located at the parting surface of the upper skin core (1) and the lower skin core (3), and the draft surface angle is 15°; S6. The inner diameter of the through hole at the center of the positioning column (8) and the inner diameter of the through hole at the bottom center of the positioning groove II (10) are both 12 mm; S7. Sand mold printing: using 100-140 mesh ceramsite sand, with a printing layer thickness of 0.28 mm, the upper skin core (1), the axial hole flow channel core (2) and the lower skin core (3) of steps S1-S6 are printed. After printing is completed, compressed air is used to blow away the loose sand inside each sand core, with a focus on cleaning the axial hole flow channel core (2); S8. Core coating: Use water-based paint for flow coating, use paint to control the Baume degree 55-80, ensure that there is no flow mark on the surface, the coating thickness is 0.3mm-0.5mm, and place it in a drying kiln for drying after flow coating, the drying time is 1 hour, and the drying temperature is 150℃-200℃; S9. Assemble the cores and close the box: Place the lower skin core (3) on a horizontal surface, take out the axial hole flow channel core (2), and remove the connecting cylinder (6) in the axial hole flow channel core (2). After the connecting cylinder (6) is removed, the axial hole flow channel core (2) is divided into a separate flow channel core (4) and an axial hole core (5). Connect the separated flow channel core (4) and the axial hole core (5) in the lower skin core (1). When connecting the flow channel core (4) and the lower skin core (1), ensure that the positioning protrusion (7) is connected. Connect it to the positioning groove Ⅰ (9). When connecting the shaft hole core (5) and the lower skin core (1), ensure that the positioning column (8) is connected to the positioning groove Ⅱ (10). Lift the lower skin core (1). Use an M10 screw and nut to pass through the through hole in the center of the positioning column (8) and the through hole in the center of the bottom surface of the positioning groove Ⅱ (10) to make the shaft hole core (5) and the lower skin core (1) fit together. Finally, connect the upper skin core (1) and the lower skin core (3) to complete the core assembly and box assembly. S10. After the box is assembled, the mold is dried with a hot air blower. The outlet temperature of the hot air blower is 150℃ and the baking time is 3 hours. Ensure that the temperature in the mold cavity is greater than 100℃ before pouring. Blow argon gas into the mold cavity before pouring. The temperature of the molten iron out of the furnace is 1520℃ and the pouring temperature is 1420℃±10℃.

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