A method for 3D printing volute sand core

Abstract

The present invention relates to the field of casting technology, and in particular to a method for rapid prototyping of volute castings. The present invention provides a method for overcoming the problems of 3D printing of volute sand cores, which adopts 3D printing modeling technology, and provides a parting surface one and a parting surface two within a certain range above and below the horizontal plane where the maximum curvature point of the diffuser tube cross section is located. The parting surface one and the parting surface two divide the volute sand core into a cover core, an intermediate core and a bottom core. The cover core is provided with a cavity for forming the air inlet portion of the volute, the intermediate core is provided with a cavity for forming the diffuser tube, and the bottom core is provided with a cavity for forming the volute rotor. The present invention overcomes the quality problems of easy scratching, sand inclusion and the influence on the parting surface when producing volutes by the casting process, simplifies the core assembly process, and makes it unnecessary to core the diffuser tube core separately, thereby avoiding quality problems such as sand scratching and easy damage to the pipe core, while ensuring the uniform wall thickness of the volute pipe and improving the quality of volute production products.

Description

Technical Field

[0001] The invention relates to the technical field of casting, in particular to a casting method for rapid prototyping of a volute casting. Background Art

[0002] The volute is one of the important parts of the turbocharger. The function of the volute is to collect the airflow coming out of the diffuser and lead it out of the machine. In the process of the volute collecting the airflow, it relies on the gradual expansion of the outer diameter and flow cross-section of the volute to play a role in speed reduction and pressure expansion in the turbocharger. Since the flow cross-section of the inner cavity diffuser pipe of the volute body is in the shape of a variable diameter spiral, the traditional casting process often adopts the method of parting along the ridge plane of the volute and casting the diffuser pipe separately with the core. Since this casting method requires the diffuser core to be placed separately, the wall thickness of the diffuser pipe is difficult to guarantee, and defects such as sand inclusions may occur when the core is placed due to reasons such as sand rubbing; at the same time, due to the structure of the diffuser pipe, the cross-section of the diffuser pipe close to the rotor is relatively small, which makes the diffuser pipe core here relatively weak and easy to be damaged during traditional molding. Summary of the Invention

[0003] The present invention overcomes the quality problems of scuffing, sand inclusion and the impact on the parting surface that are easily occurred in the production of volutes by traditional casting processes. By providing a 3D printed volute sand core, the traditional volute casting wooden mold casting process is changed to use the diffuser pipe ridge plane as the parting surface as the casting method, so that the diffuser pipe core and the outer skin sand core are connected into the same module, simplifying the core assembly process, so that the diffuser pipe core does not need to be cored separately, thereby avoiding quality problems such as sand scuffing and easy damage of the pipe core, while ensuring the uniformity of the volute pipe wall thickness and improving the quality of volute production products.

[0004] A 3D-printed volute sand core employs 3D printing technology. Parting surfaces 1 and 2 are provided within a certain range above and below the horizontal plane of the maximum curvature of the diffuser cross-section. These parting surfaces divide the volute sand core into a cover core, an intermediate core, and a bottom core. The cover core is provided with a cavity for forming the volute air inlet, the intermediate core is provided with a cavity for forming the diffuser, and the bottom core is provided with a cavity for forming the volute rotor. This is achieved specifically by:

[0005] 1) Select a suitable parting surface. Select a suitable parting surface based on the cross-sectional curvature of the volute casting diffuser tube. This parting surface should neither interfere with the assembly of the upper and lower sand cores nor hinder the removal of surface loose sand by the 3D-printed sand cores. Since the diffuser tube sand core of the bottom outer mold core and the outer mother sand core form a single module, the parting surface should be selected within a certain range above and below the horizontal plane where the diffuser tube cross-sectional curvature is at its maximum, forming two upper and lower parting surfaces, namely, parting surface one and parting surface two. This range above and below the horizontal plane contains the mold cavity of the diffuser tube with the intermediate core.

[0006] 2) Provide reasonable support for the diffuser cavity. Based on the volute structure, to ensure sufficient support for the diffuser cavity, the center core also features a cavity structure for the air inlet at the center of the volute. This cavity structure is connected to the diffuser cavity. The side core head on the diffuser cavity is formed by connecting the exhaust core head to the outer mold. The tension of the air inlet cavity at the center of the volute and the support of the side core head at the exhaust end effectively secure the diffuser sand core, ensuring a uniform diffuser wall thickness.

[0007] 3) Design and cut the sand core. The sand core is carefully designed and cut into three sections: a bottom core for casting the volute rotor mounting end, an intermediate core with the diffuser duct, and a cover core with the volute air inlet. Simultaneously, a gating system is constructed at the parting surface between the bottom core and the intermediate mold, and a riser and sprue are constructed for the cover core. Finally, matching steps are created along the outer edge of the sand core at both parting surfaces. These steps not only help position the core assembly but also prevent loose sand from flowing into the mold when the surrounding sand is tightened.

[0008] 4) 3D printing and core assembly: The three parts of the sand core are 3D printed separately. The bottom core, middle core, and cover core are assembled from bottom to top. After the core assembly is completed, the core is placed in a sand box, filled with resin sand, and tightened to prevent expansion. Finally, molten iron is poured and after solidification, the volute casting that meets the requirements is obtained by unpacking.

[0009] By using 3D printing technology to change the parting surface and core removal method in the volute casting process, compared with the previous traditional volute casting process, the core assembly process is simplified, and the core assembly process is simplified, so that the diffuser core does not need to be cored separately, thereby avoiding casting process problems such as core rubbing and easy damage to the pipe core. At the same time, it ensures the uniform wall thickness of the volute pipe, expands the new idea of ​​sand core parting of volute castings, and improves the quality and production efficiency of volute products. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic diagram of the parting surface of the traditional volute

[0011] Figure 2 Schematic diagram of the parting surface of the volute of the present invention

[0012] Figure 3 Schematic diagram of the structure of the diffuser tube sand core and the intermediate core

[0013] Figure 4 Schematic diagram of sand core assembly in volute casting process

[0014] 1- traditional process parting surface, 5-parting surface one, 6-parting surface two, 7-air inlet cavity, 8-diffuser cavity, 9-exhaust hole core head, 10-cover core, 11-middle core, 12-bottom core. DETAILED DESCRIPTION

[0015] In order to more clearly illustrate the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific embodiments. Please note that the embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0016] Figure 1 It is a schematic diagram of the parting surface when producing the volute by traditional technology. The parting surface 1 of the traditional technology is formed by parting along the ridge plane of the volute. The diffuser pipe is cast by a separate core-out method. The core assembly is to lower the diffuser pipe core into the bottom core through the core nose connected to the internal core bone. After lowering, the diffuser pipe core must be lifted out for repair. At the same time, in addition to preventing sand from being rubbed during the core lowering process, a special clamping plate is also required to locate whether the wall thickness of the lower core of the diffuser pipe is uniform. The operation is relatively troublesome and has high requirements for the implementer.

[0017] The present invention provides a 3D printed volute sand core. According to the cross-sectional curvature of the volute casting diffuser tube, a suitable parting surface is selected. The parting surface is selected to form two upper and lower parting surfaces within a certain range above and below the horizontal plane where the maximum cross-sectional curvature of the diffuser tube is located. That is, the original process of parting along the plane of the volute diffuser tube ridge is changed to parting with two upper and lower parting surfaces, that is, forming parting surface 1 5 and parting surface 2 6. The diffuser tube cavity 8 is contained within a certain range above and below the horizontal plane. Figure 2 As shown, parting surface 5 is the parting surface between the top outer mold core and the middle core of the diffuser tube, and parting surface 2 6 is the parting surface between the bottom outer mold core and the middle core of the diffuser tube.

[0018] Reasonable cavity support for the diffuser tube sand is set. According to the structure of the volute, in order to ensure sufficient support force to ensure the diffuser tube sand core. The middle core is also provided with a cavity structure of the air inlet in the center of the volute, and the structure of the air inlet cavity 7 is connected to the diffuser tube cavity 8. The side core head on the diffuser tube cavity is formed by the exhaust hole core head 9 connected to the outer mold. The tension of the air inlet cavity in the center of the volute and the support force of the side core head at the exhaust hole end can effectively fix the diffuser tube sand core and ensure that the diffuser tube wall thickness is uniform.

[0019] Design and cut sand cores. Detailed design and cutting of sand cores, such as Figure 4 As shown, three sand cores are cast: a bottom core 12 for the bottom outer mold and the volute rotor mounting end; an intermediate core 11 for the diffuser duct; and a cover core 10 for the top outer mold and the volute air inlet. A gating system is constructed at the parting surface between the bottom core and the intermediate mold, while a riser and sprue are constructed for the cover core. Furthermore, a 30mm-wide step is created along the outer edge of the sand core at both parting surfaces. This not only helps position the core assembly but also prevents loose sand from flowing into the mold when the surrounding sand is tightened.

Claims

1. A 3D printed volute sand core, characterized in that: A parting surface one and a parting surface two are provided within a certain range above and below the horizontal plane where the point of maximum curvature of the diffuser tube cross section is located. The parting surface one and the parting surface two divide the volute sand core into a cover core, an intermediate core and a bottom core. Matching steps are respectively made along the outer edge of the sand core at the two parting surfaces. The cover core is provided with a cavity for forming the air inlet part of the volute, the intermediate core is provided with a cavity for forming the diffuser tube, the intermediate core is also provided with a cavity structure for the air inlet hole in the center of the volute, the cavity structure of the air inlet hole is connected to the cavity of the diffuser tube, the cavity of the diffuser tube is also provided with a side core head formed by an exhaust hole core head connected to the outer mold, the bottom core is provided with a cavity for forming the volute rotor, and the diffuser tube core and the outer skin sand core are connected to form the same module.

2. A 3D printed volute sand core according to claim 1, characterized in that: A pouring system is provided at the parting surface between the bottom core and the middle core.

3. A 3D printed volute sand core according to claim 1, characterized in that: The cover core is provided with a riser and a sprue.

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