Precision casting shell modeling and positioning device and using method

Abstract

The invention relates to the field of metal investment precision casting, in particular to a precision casting shell modeling and positioning device and a using method. The positioning device is of a semicircular structure composed of an inner positioning layer and an outer positioning layer, the outer positioning layer and the inner side of a sand box are positioned in a contact mode, the outer positioning layer is matched with the inner side of the sand box in shape and tightly attached to the inner side of the sand box, the outer positioning layer and the inner positioning layer are fixedly connected, and the inner positioning layer and the fixed position of the outer side of a shell are positioned in a contact mode. And the shape is consistent with that of the outer side of the shell positioning part. After the shell is put into the sand box by using the positioning device, the position of the shell in the sand box can be determined, the relative height of outer layer positioning and inner layer positioning in the positioning device can be adjusted according to the molding requirement of the shell, and then the spatial position of the shell in the sand box is fixed; and the purpose of unifying the spatial positions of all the shells in the sand box is achieved. The positioning device is simple in structure, low in cost, high in practicability and remarkable in economic benefit.

Description

Technical Field

[0001] This invention relates to the field of metal investment casting, specifically to a precision casting mold positioning device and its usage method, which is particularly suitable for ensuring the uniform spatial position of the mold shell within the sand box during batch production, thereby stabilizing the casting qualification rate. Background Technology

[0002] Currently, my country's casting level is not high, and there is still a significant gap compared with some developed countries, especially in investment casting for complex structural castings. During batch production, even with consistent key process parameters (such as casting assembly method, shell preheating temperature, alloy refining time and temperature, and alloy pouring temperature), the pass rate of different batches often fluctuates significantly. For example, the average pass rate of a certain casting might be 60%, with a normal fluctuation range of 50% to 70%, but frequently it can be as low as 20% to 50%. Checking the preparation process records reveals no obvious abnormalities. This introduces considerable uncertainty into the cost and cycle time of batch casting preparation and also affects the stability of casting quality. The impact of molds, especially on aerospace castings such as engine blades, is significant. These castings have extremely high requirements for quality and stability, and cannot tolerate large fluctuations in the yield rate or other uncertainties during batch production. Research has found that although the same specifications of sand box and molding sand are used in the shell molding process, the spatial placement of each shell within the sand box varies considerably. This leads to significant differences in the filling sequence and flow state of the molten metal in different locations of the shell during pouring, even when the molten metal enters at the same angle and flow rate. Consequently, this results in large fluctuations in the yield rate of the castings. To stabilize the yield rate of batch-produced castings, it is urgent to control the shell molding process to ensure the stability of batch-produced casting quality.

[0003] Patent CN221246856U discloses a positioning mechanism for precision casting shell making. During shell transfer or processing, it uses a hook and positioning component to prevent falling. However, this only addresses the transfer stage and does not address the spatial positioning within the sand box during the shell molding stage, thus failing to solve the problem of yield fluctuations caused by differences in molding position. Patent CN222133377U discloses a core positioning device for precision casting. While it achieves coaxial positioning of the upper and lower positioning seats through a centering mechanism, it relies on complex transmission structures such as drive motors and gear rings, resulting in high costs and complex operation. Furthermore, its positioning object is the core assembly box, not the molding positioning of the shell within the sand box, making it unsuitable for sand-filled molding scenarios and unable to meet the rapid positioning requirements of mass production. Patent CN118080842A discloses a pre-positioned precision control device and method for large-module casting shells, targeting the transfer and positioning of 50kg-class large-module casting shells. However, this relies on bulky equipment such as transfer tracks, lifting mechanisms, and pushing mechanisms, making it only suitable for large-module transfers and unsuitable for the molding and positioning of conventional small and medium-sized casting shells within sand boxes. Patent CN119016684A discloses a casting method for investment casting based on a casting shell positioning fixture. While it involves casting shell positioning, its core method relies on an adjustable positioning plate to achieve three-dimensional positioning of the casting shell during the casting stage. Adjusting the positioning plate requires disassembling positioning pins or tightening threads. Furthermore, its fixture is only compatible with the main shaft tray of the melting furnace and cannot be used with sand boxes for positioning during the molding stage. The patent with publication number CN118809589A proposes a target positioning control method, system, equipment and medium for precision casting shell making. It relies on visual positioning technology that uses camera reference coordinates and robotic arm coordinate calibration. It requires the pre-establishment of a complex coordinate system and is designed for wax mold grasping and positioning, rather than fixing the spatial position of the shell in the sand box. It is not suitable for small and medium batch or low-cost mass production.

[0004] In summary, existing technologies cannot meet the requirement of uniform spatial position of the shell within the sandbox during the shell molding stage. Therefore, it is necessary to develop a shell molding positioning solution that is simple in structure, low in cost, and can guarantee consistent positioning. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a precision casting mold shell molding and positioning device and its usage method, which solves the problems of yield fluctuation caused by the difference in the molding position of the existing positioning technology and the difficulty in ensuring the consistency of the spatial positioning of the mold shell during batch production.

[0006] The technical solution adopted in this invention is: A precision casting mold shell molding and positioning device is a semi-circular structure composed of inner and outer double positioning layers. The outer positioning layer is in contact with the inner side of the sand box, and its shape matches and fits tightly with the inner side of the sand box. The outer positioning layer is fixedly connected to the inner positioning layer, and the inner positioning layer is in contact with a fixed position on the outer side of the mold shell, and its shape is consistent with the outer shape of the positioning position on the mold shell.

[0007] The precision casting mold positioning device has an outer positioning dimension that matches the inner dimension of the sand box used for the molding, and is used to fit against the inner side of the sand box to limit the horizontal position of the positioning device within the sand box.

[0008] The precision casting mold shell molding and positioning device has an inner layer positioning that contacts and positions a fixed position on the outside of the mold shell. Its shape is consistent with the outer shape of the positioning point of the mold shell. In use, the positioning point of the mold shell is placed into the corresponding position of the inner layer positioning to define the horizontal position and height reference of the mold shell.

[0009] The precision casting mold positioning device has an outer positioning upper end with a positioning auxiliary component that matches the upper edge of the sand box. The positioning auxiliary component is fixed to the upper edge of the sand box, and the matching of the positioning auxiliary component with the upper edge of the sand box limits the height position, vertical displacement and horizontal offset of the positioning device in the sand box.

[0010] The positioning auxiliary components of the precision casting shell molding and positioning device are positioning hooks, positioning buckles, or positioning pins.

[0011] The precision casting shell molding and positioning device has an outer layer positioning and an inner layer positioning reinforced and connected into an integrated structure by inner and outer layer connecting parts. The connection between the inner and outer layer connecting parts and the outer and inner layer positioning is a bolted connection, welding or mortise and tenon structure.

[0012] The precision casting mold shell positioning device is divided into inner and outer layers. The outer layer is used to determine the positional relationship between the positioning device and the sand box, and the inner layer is used to determine the spatial position of the mold shell in the sand box.

[0013] The method of using the precision casting shell molding and positioning device includes the following steps: (1) Determine the shape and size of the outer positioning according to the shape and size of the inner side of the sand box to ensure that the outer positioning matches the inner side of the sand box; determine the shape and size of the inner positioning according to the shape and size of the outer side of the fixed position of the shell to ensure that the inner positioning matches the outer side of the positioning position of the shell; determine the positional relationship between the inner positioning and the outer positioning according to the spatial position of the shell in the sand box and fix them with inner and outer connecting parts; after installing the positioning auxiliary parts on the outer positioning, the positioning device is completed. (2) Insert the inner positioning clip of the positioning device into the outer side of the positioning position of the shell, and then put the positioning device and the shell into the sand box together, so that the outer positioning clip fits into the inner side of the sand box, and use positioning auxiliary parts to fix it to the sand box. (3) Fill the sand box with molding material to the specified height, and remove the positioning device to complete the shell molding.

[0014] The method of using the precision casting mold shell positioning device, in step (3), the molding material is molding sand, cotton wrapping or single shell material, and the position of the mold shell in the sand box is fixed by filling or wrapping the molding material.

[0015] The design concept of this invention is: To address the problem of existing technologies failing to fix the position of the mold shell within the sand box, this invention employs an inner layer positioning device whose shape matches the outer side of the mold shell's positioning position, an outer layer positioning device whose shape matches the inner side of the sand box, and a positioning auxiliary component for fixation. Specifically: the inner layer, by matching the outer side of the mold shell's positioning position, directly limits the horizontal radial position of the mold shell, preventing lateral displacement within the sand box; the outer layer, by matching the dimensions of the inner side of the sand box, fixes the positioning device itself at a preset horizontal position within the sand box, indirectly providing a horizontal reference for the mold shell; the upper positioning hook engages with the upper edge of the sand box, further limiting the vertical displacement and horizontal movement of the positioning device, ensuring that the height position of the mold shell does not change during sand filling. The combination of these three components achieves horizontal and vertical positioning of the mold shell, fundamentally eliminating fluctuations in the filling and solidification sequence of molten metal caused by positional differences. Furthermore, this invention allows for adjustment of the outer layer shape according to different sand boxes and the inner layer shape according to different mold shell shapes.

[0016] To address the issues of high cost and cumbersome operation of existing complex positioning technologies and equipment, this invention adopts a purely mechanical positioning design. Through only inner and outer layer structures and hooks, manufacturing costs are significantly reduced, and the operation process is simplified to embedding the mold positioning device into the mold shell, placing it in the sand box, filling with sand, and then removing it, thus avoiding the maintenance costs of complex equipment. After the positioning device is removed, the position of the mold shell within the sand box is fixed by the sand filling, ultimately achieving a small fluctuation range in the casting yield rate and meeting the requirements for high-stability batch production.

[0017] The advantages and positive effects of this invention are: 1. This invention ensures the consistency of the spatial position of the mold shell in the sand box when the same type of mold shell is repeatedly molded during batch production. On the one hand, it reduces the difference in the landing point of the molten metal in the mold shell during different pouring cycles, thereby improving the consistency of the molten metal flow state in the mold shell and reducing the differences in the molten metal flow state during different pouring cycles. On the other hand, it improves the consistency of the sand filling state during mold shell molding, ensuring that the heat storage at the same position of the mold shell is basically the same in different pouring cycles, thereby ensuring the consistency of the solidification sequence of the castings. This greatly improves the stability of the casting pouring process, significantly reduces the fluctuation of the casting qualification rate in different pouring cycles, and ensures the smooth progress of batch production. The positioning device of this invention has a simple structure, low cost, strong practicality, and significant economic benefits.

[0018] 2. The present invention, through the positioning structure of inner positioning shell, outer positioning sand box and hook fixation, can ensure that the spatial position (such as horizontal coordinates and height) of each shell in the sand box is completely uniform during the batch production process, avoiding performance differences caused by position differences.

[0019] 3. The improved positioning consistency of this invention can reduce the difference in the landing point of molten metal in the mold shell during different furnace pours, reduce the fluctuation of molten metal flow state, and at the same time ensure that the heat storage in the same position of the mold shell is basically consistent, thereby ensuring the uniform solidification sequence of the castings, significantly reducing the fluctuation of the casting qualification rate of different furnaces, and ensuring the smooth progress of batch production. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the precision casting mold positioning device of the present invention. In the figure, 1-outer layer positioning (shape matches the inner side of the sand box), 2-positioning hook, 3-inner and outer layer connecting parts, 4-inner layer positioning (shape matches the lower part of the mold pouring cup).

[0021] Figures 2-3 This is a schematic diagram illustrating the usage of a precision casting shell molding and positioning device. Figure 2 For three dimensions Figure 1 , Figure 3 For three dimensions Figure 2 In the diagram, 5 is the sand box, 6 is the casting cup of the molded shell, 7 is the positioning device, and 8 is the molded shell. Detailed Implementation

[0022] The method of using this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments and methods of use obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] like Figures 1-3As shown, this invention proposes a precision casting mold shell molding and positioning device and its usage method. The sand box 5 used is cylindrical. A special mold shell molding and positioning device is made according to the shape and size of the sand box 5 and the mold shell 8. The positioning device 7 is a semi-circular structure composed of an outer positioning layer 1 and an inner positioning layer 4, divided into inner and outer layers. The outer layer is used to determine the positional relationship between the positioning device 7 and the sand box 5, and the inner layer is used to determine the spatial position of the mold shell 8 in the sand box 5. The outer positioning layer 1 is a semi-cylindrical structure whose shape matches the inner side of the sand box 5 and fits tightly against the inner side of the sand box. The inner positioning layer 4 is a semi-circular disc structure with a semi-circular hole in the center. The inner positioning layer 4 matches the lower part of the mold shell pouring cup 6 through the semi-circular hole. The semi-circular end faces of the outer positioning layer 1 and the inner positioning layer 4 are reinforced and connected into an integral structure by the inner and outer layer connecting parts 3, which are two triangular ribs.

[0024] The outer positioning 1 has dimensions consistent with the inner dimensions of the sand box 5 used for molding, and has two or more positioning hooks 2 at its upper end that match the upper edge of the sand box 5. These hooks are engaged and fixed to the upper edge of the sand box 5. The semi-circular hole on the inner positioning 4 has dimensions consistent with the lower side of the molded shell pouring cup 6 to be molded and positioned. During use, the lower part of the molded shell pouring cup 6 is placed into the corresponding position of the semi-circular hole for positioning. After the positioning device 7 and the molded shell 8 are placed in the sand box 5, the position of the positioning device 7 in the sand box 5 can be determined. The relative height between the outer positioning 1 and the inner positioning 4 in the positioning device 7 can be adjusted according to the molded shell molding requirements, thereby fixing the spatial position of the molded shell 8 in the sand box 5. During continuous molded shell molding in batch production, this achieves the goal of uniform spatial position of all molded shells 8 in the sand box 5.

[0025] In use, first place the positioning device 7 in the sand box 5, position the positioning hook 2 in contact with the upper edge of the sand box 5, and ensure that the outer positioning 1 is in full contact with the inner surface of the sand box 5 to ensure that the position of the positioning device 7 in the sand box 5 is fixed. Then, place the lower part of the shell pouring cup 6 into the inner positioning 4. The positioning device 7 can be used to accurately position the shell 8 in the sand box 5. Fill the sand box 5 with molding sand to complete the entire shell positioning and molding process.

[0026] The present invention will be further described in detail below through embodiments.

[0027] Example

[0028] like Figures 1-3 As shown, taking the precision casting mold shell of K417G alloy ingot as an example, the sand box 5 used is cylindrical (inner diameter 300mm, height 400mm), the mold shell pouring cup 6 is located at the top of the mold shell 8 and coincides with the central axis of the mold shell 8, the lower part of the mold shell pouring cup 6 is frustum shaped, the central axis of the mold shell 8 in the sand box 5 coincides with the central axis of the sand box 5, and the top of the mold shell pouring cup 6 is 30mm away from the upper edge of the sand box 5.

[0029] In this embodiment, the manufacturing process of the positioning device is as follows: 1. Outer positioning structure: Based on the inner dimensions of the sand box, the outer positioning 1 of the positioning device 7 is made into a semi-cylindrical structure with an outer diameter of 300mm to ensure that the outer layer fits tightly against the inner side of the sand box; 2. Inner positioning structure: According to the lower size of the shell pouring cup 6, at the bottom of the outer positioning 1, the inner positioning 4 of the positioning device 7 is made into a semi-circular ring structure that is perpendicularly connected to the outer positioning 1. The center of the inner positioning 4 is provided with a semi-circular hole that matches the lower part of the shell pouring cup 6, so as to ensure that the lower part of the shell pouring cup 6 can be fully embedded. 3. Connectors and hooks: The outer positioning 1 and the inner positioning 4 are reinforced and connected into an integral structure at their semi-circular end faces by the inner and outer connecting parts 3. The inner and outer connecting parts 3 are two triangular stiffeners. Two positioning hooks 2 are evenly arranged on the upper outer side of the outer positioning 1, corresponding to the upper edge of the sand box 5. The positioning hooks 2 are engaged and fixed with the upper edge of the sand box 5.

[0030] In this embodiment, the steps for using the positioning device are as follows: 1. Assembly of the mold shell and positioning device: Align the inner positioning 4 of the positioning device 7 with the lower part of the mold shell sprue cup 6, and slowly insert it so that the lower part of the mold shell sprue cup 6 is completely embedded in the semi-circular hole of the inner positioning 4, ensuring that there is no relative displacement between the mold shell 8 and the positioning device. 2. Place the entire assembly into the sand box: Place the assembled shell 8 and positioning device 7 into the sand box 5, ensuring that the outer layer of the positioning device 7 fits tightly against the inner side of the sand box 5. At the same time, engage the two positioning hooks 2 at the upper end of the positioning device 7 with the corresponding positions on the upper edge of the sand box 5 to ensure that the positioning device 7 does not shift horizontally or vertically within the sand box. 3. Sand filling and removal device: Fill the sand box 5 with molding sand to the specified height (after filling the bottom of the shell 8 with sand, place the shell 8 on the corresponding position of the molding sand to determine the spatial position of the shell 8 in the sand box 5). Then, slowly lift the positioning device 7 upward along the inner wall of the sand box 5 (the shell 8 can be tilted appropriately, and after lifting the positioning device 7, return it to its original position) to separate the positioning device 7 from the shell 8 and the sand box 5. After the positioning device is removed, the position of the shell 8 in the sand box is fixed by the filling of sand. Continue to fill the sand box 5 with molding sand until the shell molding is completed.

[0031] Table 1 Tensile property test results of K417G alloy cast rod

[0032] The results show that in the precision casting and pouring of 10 consecutive heats of K417G alloy ingots, the position of the mold shell within the sand box was consistent. The tensile property test results of the 10 heats of ingots (see Table 1) were also consistent, with tensile strength stable at 640~685MPa, fluctuation within ±4% of the median, and a pass rate of 100%. Therefore, the positioning device of this invention has low manufacturing cost, simple operation, and significant effect.

Claims

1. A precision casting mold shell shaping and positioning device, characterized in that, The positioning device is a semi-circular structure composed of inner and outer double positioning layers. The outer positioning layer is in contact with the inner side of the sand box, and its shape matches the inner side of the sand box and fits tightly against the inner side of the sand box. The outer positioning layer is fixedly connected to the inner positioning layer, and the inner positioning layer is in contact with the fixed position on the outside of the shell, and its shape is consistent with the shape of the outer side of the positioning position on the shell.

2. The precision casting mold shell shaping and positioning device according to claim 1, characterized in that, The outer positioning dimensions are consistent with the inner dimensions of the sandbox of the desired shape, and are used to fit against the inner side of the sandbox to define the horizontal position of the positioning device within the sandbox.

3. The precision casting mold shell molding and positioning device according to claim 1, characterized in that, The inner layer positioning is contacted and positioned with the fixed position on the outside of the shell. Its shape is consistent with the outer shape of the shell positioning point. In use, the shell positioning point is placed into the corresponding position of the inner layer positioning to define the horizontal position and height reference of the shell.

4. The precision casting mold shell molding and positioning device according to claim 1, characterized in that, The upper end of the outer positioning layer has a positioning auxiliary component that matches the upper edge of the sand box. The positioning auxiliary component is fixed to the upper edge of the sand box, and the matching of the positioning auxiliary component with the upper edge of the sand box limits the height position, vertical displacement and horizontal offset of the positioning device in the sand box.

5. The precision casting mold shell shaping and positioning device according to claim 4, characterized in that, Positioning accessories include positioning hooks, positioning buckles, or positioning pins.

6. The precision casting mold shell shaping and positioning device according to claim 1, characterized in that, The outer and inner positioning layers are reinforced and connected into an integrated structure through inner and outer layer connectors. The connection between the inner and outer layer connectors and the outer and inner positioning layers is a bolted connection, welded connection, or mortise and tenon connection.

7. The precision casting shell molding and positioning device according to claim 1, characterized in that, The positioning device consists of two layers: the outer layer is used to determine the positional relationship between the positioning device and the sand box, and the inner layer is used to determine the spatial position of the shell in the sand box.

8. A method of using the precision casting mold shell molding and positioning device according to any one of claims 1 to 7, characterized in that, Includes the following steps: (1) Determine the shape and size of the outer positioning according to the shape and size of the inner side of the sand box to ensure that the outer positioning matches the inner side of the sand box; determine the shape and size of the inner positioning according to the shape and size of the outer side of the fixed position of the shell to ensure that the inner positioning matches the outer side of the positioning position of the shell; determine the positional relationship between the inner positioning and the outer positioning according to the spatial position of the shell in the sand box and fix them with inner and outer connecting parts; after installing the positioning auxiliary parts on the outer positioning, the positioning device is completed. (2) Insert the inner positioning clip of the positioning device into the outer side of the positioning position of the shell, and then put the positioning device and the shell into the sand box together, so that the outer positioning clip fits into the inner side of the sand box, and use positioning auxiliary parts to fix it to the sand box. (3) Fill the sand box with molding material to the specified height, and remove the positioning device to complete the shell molding.

9. The method of using the precision casting mold shell molding and positioning device according to claim 8, characterized in that, In step (3), the molding material is molding sand, cotton wrapping or single shell material. The position of the shell in the sand box is fixed by filling or wrapping the molding material.

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