Height control and precise control method for frozen sand additive manufacturing in temporal space

Abstract

The present invention relates to a method for height control and precise regulation of frozen sand mold additive manufacturing in a temporal space. This method establishes a mathematical model for the time-varying thickness of floating sand generated by heat exchange between frozen sand molds and air. This model predicts and provides feedback on the floating sand thickness of frozen sand molds with different curved surfaces under varying parameters such as ambient temperature, time scale, sand mold material, and moisture content. Furthermore, during the frozen printing process, real-time adhesive and height compensation are applied to the sand mold at different wall thicknesses, thereby providing a certain degree of protection for the dimensional and geometric accuracy of the frozen sand mold. This method effectively solves the problem of dimensional accuracy errors caused by floating sand generated by heat exchange in the air during the manufacturing and subsequent placement of frozen sand molds, ensuring dimensional accuracy during sand mold casting.

Description

Technical Field

[0001] The present invention relates to the field of sand mold additive manufacturing, and in particular to the precision manufacturing and control of frozen sand molds. Specifically, it relates to a method for accurately controlling the elevation during the frozen sand mold additive manufacturing process in a temporal space. Background Art

[0002] As an emerging method for making casting molds, frozen sand additive manufacturing technology uses the principle of phase change freezing of water-based adhesives at low temperatures to form sand molds through layer-by-layer spray consolidation and superposition. This technology has the potential to achieve high precision and the ability to manufacture complex geometric shapes. However, during the frozen sand mold manufacturing process, due to factors such as ambient temperature, sand mold material, and adhesive content, the frozen sand mold's adhesive will gradually sublime and dissipate over time, reducing the bonding strength of the sand mold surface until the sand particles can no longer agglomerate together, resulting in loose sand, or so-called floating sand. The generation of floating sand seriously affects the size and geometric accuracy of the frozen sand mold, and in severe cases, it can even cause the frozen sand mold to lose its castability. Therefore, how to accurately control the elevation of the frozen sand mold and compensate for changes in floating sand thickness during the frozen sand additive manufacturing process is an urgent problem that needs to be solved. Summary of the Invention

[0003] To solve the above problems, the present invention discloses a method for height control and precise regulation of frozen sand mold additive manufacturing in time-series space, which realizes adhesive compensation in the frozen sand mold additive manufacturing process, solves the problems of frozen sand mold structural damage and function loss caused by floating sand, and improves casting accuracy.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention includes the following steps:

[0005] Step 1: Calculate the minimum wall thickness required for each part of the frozen sand mold based on the input casting model characteristics, ensure the strength of the frozen sand mold, and select the appropriate size of the three-dimensional contour inclusion body.

[0006] Step 2: Inversely calculate the frozen sand mold based on the selected inclusion size to generate a three-dimensional data model of the frozen sand mold.

[0007] Step 3: Perform traversal analysis on the generated frozen sand mold 3D data model to extract the location information of each point.

[0008] Step 4: Based on the point information obtained from the analysis, perform adhesive compensation according to the following equation:

[0009] c=Ae -(x+a)t +Be -(y+b)t +Ce (h-H)t

[0010] In the formula, c is the multiplication factor of the basic spray adhesive content, x is the distance from the point to the outer wall, y is the distance from the point to the inner cavity, a and b are compensation constants for compensating the outer wall and inner cavity respectively, A and B are compensation multiplication factors for the outer wall and inner cavity respectively, C is the height compensation constant, h is the height of the point from the bottom surface, H is the height of the sand mold, t is the required storage time in hours, and e is the base of the natural logarithm.

[0011] Step 5: Combine the obtained adhesive compensation results with the slicing information to adjust the content of the sprayed adhesive in real time during the printing process.

[0012] Step 6: Store the printed sand mold in a cold storage.

[0013] Furthermore, the precise control of the height of the frozen sand mold is achieved by proposing a floating sand peeling control technology based on curvature analysis. The floating sand height change of the flat sand mold presents a linear change trend, and the floating sand height change of the complex curved surface presents a nonlinear trend. The compensation height not only considers time, but also optimizes the floating sand peeling speed according to the geometric shape of the curved surface, making the floating sand peeling process more smooth and uniform, and ultimately achieving a more precise sand mold forming effect.

[0014] Furthermore, the change rules of the floating sand height of the flat sand mold and the complex curved surface are shown in the following equations:

[0015] S1=Mt

[0016] S2=Nlogft+n

[0017] Where S1 is the time-varying law of the floating sand height of the flat sand mold; S2 is the time-varying law of the floating sand height of the curved sand mold; M and N are the floating sand height multiplication factors of the flat and curved sand molds, respectively; t is the storage time of the frozen sand mold; f is the base factor related to the curvature; and n is the floating sand height deviation compensation constant.

[0018] Furthermore, in step 1, the minimum wall thickness of each part is a safety value obtained according to different sand mold materials and sand mold sizes to ensure the strength of the sand mold, and the generated inclusion is a solid cylinder or cuboid with a maximum safety value.

[0019] Further, in step 2, when inversely analyzing the structure of the sand mold, it is necessary to consider the design of the riser and pouring system, the design of the exhaust system, and the design of the cooling system.

[0020] Furthermore, when inverting the structure of the sand mold in step 2, the floating sand height change characteristics generated in different curvature areas of the sand mold over time are used to pre-calculate the change law of the floating sand through a digital analysis model, and different degrees of height compensation are performed on different curvature areas, so that the initial shape of the printed sand mold has different degrees of expansion at the corresponding position compared to the digital model.

[0021] Furthermore, the point information of step 3 is gridded according to the unit body defined by the slice thickness to reduce the amount of data and correspond to the slice information. The position information includes the height and the distance between the position and the outer wall and the inner cavity.

[0022] Furthermore, the c value obtained in step 4 is multiplied by increasing the driving voltage value and grayscale value of the nozzle during inkjet, thereby increasing the inkjet amount.

[0023] Furthermore, in step 5, a corresponding matrix of each slice layer is formed according to the slice result by waiting for the c value, and the matrix is ​​loaded into the parameter control of the print head and combined with the slice information to achieve compensation of the adhesive content.

[0024] Furthermore, in step 6, the printed frozen sand mold is placed in a cold storage and is best used within a specified time, with the deviation preferably not exceeding 12 hours.

[0025] The present invention mainly solves the technical problem of floating sand caused by adhesive sublimation during the production process of frozen sand molds, which in turn affects the accuracy and performance of the sand molds. It has the following advantages:

[0026] 1. Accurately compensate for floating sand: Through the adhesive compensation model in the time-series space, the adhesive injection amount is adjusted in real time to compensate for the adhesive loss problem caused by floating sand in the sand mold, maintaining the structural strength and geometric accuracy of the sand mold.

[0027] 2. Improve casting accuracy: Dynamic compensation of adhesive is adopted, so that the frozen sand mold can maintain good geometric shape and dimensional accuracy even in the case of partial loss of adhesive, thus avoiding defects in castings due to deformation of sand mold.

[0028] 3. Extend the use time of sand molds: This method can effectively control the adhesive loss rate of frozen sand molds, extend their shelf life and maintain high precision and stability during their use period.

[0029] 4. Optimize the manufacturing process: During the manufacturing process, combined with slicing technology, the amount of adhesive injection can be precisely controlled to ensure the material usage and forming quality of each layer of the sand mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a process flow chart of the present invention;

[0031] Figure 2 This is a schematic diagram of the grid division of the frozen sand mold unit of the present invention;

[0032] Figure 3 This is a front view of the grid division of the frozen sand mold unit of the present invention.

[0033] List of reference numerals:

[0034] 1-Unit grid; 2-Casting cavity. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inward" and "outward" refer to directions toward or away from the geometric center of a particular component, respectively. Figure 1 and Figure 2 The figure is for illustration only. The mold is divided into unit grids according to the set requirements. When performing compensation operations, the main focus is on the unit grids of each outer wall surface and the unit grid close to the casting cavity.

[0036] First, based on the structural characteristics of the frozen sand mold, the riser and pouring system, exhaust system, and cooling system are designed. For example, in practical applications, when casting large, complex parts, the main runner, cross runner, and ingates are considered, and different structural dimensions are designed to ensure that the molten metal flows smoothly into the mold cavity. At the same time, the exhaust system ensures the smooth discharge of gas to avoid the occurrence of pore defects, while the cooling system helps control the temperature and ensure the quality of the molded part. The height variation of the floating sand in the frozen sand mold is calculated and analyzed. Taking into account the storage time and surface geometry, different degrees of height compensation are applied to different curvature areas, so that the initial shape of the printed sand mold has different degrees of expansion compared to the corresponding position of the digital model.

[0037] According to different sand mold materials and sand mold sizes, a safe value of the minimum wall thickness of each part is obtained to ensure the strength of the sand mold and generate a solid cylindrical or rectangular inclusion with the maximum safety value.

[0038] The grid is divided according to the unit body defined by the slice thickness to obtain the point information of each grid area to reduce the amount of data and correspond to the slice information. The point information includes the height and the distance between the position and the outer wall and the inner cavity.

[0039] Based on the obtained point information, the adhesive injection amount is compensated by changing the drive voltage value and grayscale value of the nozzle. The slicing information is combined with the inkjet compensation amount for printing. After printing is completed, the frozen sand mold is placed in a cold storage and must be used within the specified time. The deviation should not exceed 12 hours.

[0040] The specific steps are as follows:

[0041] Step 1: Calculate the minimum wall thickness required for each part of the sand mold based on the pump casing casting model characteristics in the embodiment, ensure the strength of the sand mold, and select the appropriate size of the inclusion body.

[0042] Step 2: Inversely calculate the sand mold based on the selected inclusion size to generate a three-dimensional data model of the sand mold.

[0043] Step 3: Traverse and analyze the generated sand mold 3D data model to extract the location information of each point.

[0044] Step 4: Based on the point information obtained from the analysis, perform adhesive compensation according to the following equation:

[0045] c=Ae -(x+a)t +Be -(y+b)t +Ce (h-H)t

[0046] In the formula, c is the multiplication factor of the basic spray adhesive content, x is the distance from the point to the outer wall, y is the distance from the point to the inner cavity, a and b are compensation constants for compensating the outer wall and inner cavity respectively, A and B are compensation multiplication factors for the outer wall and inner cavity respectively, C is the height compensation constant, h is the height of the point from the bottom surface, H is the height of the sand mold, t is the required storage time in hours, and e is the base of the natural logarithm.

[0047] Step 5: Combine the obtained adhesive compensation results with the slicing information to adjust the content of the sprayed adhesive in real time during the printing process.

[0048] Step 6: Store the printed sand mold in a cold storage.

[0049] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above-mentioned embodiment, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A method for height control and precise regulation of frozen sand additive manufacturing in time sequence space, characterized in that The following steps are involved: Step 1: Calculate the minimum wall thickness required for each part of the sand mold based on the input casting model characteristics to ensure the strength of the frozen sand mold and select the appropriate size of the three-dimensional contour inclusion body; the minimum wall thickness of each part in step 1 is a safety value obtained based on different sand mold materials and sand mold sizes to ensure the strength of the sand mold, and the generated inclusion body is a solid cylinder or cuboid with the maximum safety value; Step 2: Inversely calculate the frozen sand mold shape based on the selected inclusion size to generate a three-dimensional data model of the frozen sand mold. When inversely calculating the shape, perform elevation compensation according to the following equation: S1=Mt S2=Nlog f t+n Wherein, S1 is the time-varying law of the floating sand height of the flat sand mold; S2 is the time-varying law of the floating sand height of the curved sand mold; M and N are the floating sand height multipliers of the flat and curved sand molds, respectively; t is the storage time of the frozen sand mold; f is the base factor related to the curvature; and n is the floating sand height deviation compensation constant. In step 2, when inversely calculating the frozen sand mold shape, the floating sand peeling control technology based on curvature analysis is used to compensate for the floating sand peeling elevation according to the geometric shape of the curved surface, so that the obtained frozen sand mold shape is larger than the actual shape, effectively preventing the size deviation caused by floating sand during storage, and ultimately achieving a more accurate sand mold forming effect. Step 3: traverse and analyze the generated frozen sand mold three-dimensional data model to extract the location information of each point; the point information in step 3 is gridded according to the unit body defined by the slice thickness to reduce the amount of data and correspond to the slice information. The location information includes height, distance from the outer wall and inner cavity; Step 4: Based on the point information obtained from the analysis, perform adhesive compensation according to the following equation: c=Ae -（x+a）t +Be -（y+b）t +This （h-H）t Wherein, c is the multiplication factor of the basic spray adhesive content, x is the distance between the point and the outer wall, y is the distance between the point and the inner cavity, a and b are compensation constants for compensating the outer wall and the inner cavity, A and B are compensation multiplication factors for the outer wall and the inner cavity, C is the height compensation constant, h is the height of the point from the bottom surface, H is the height of the sand mold, t is the required storage time in hours, and e is the base of the natural logarithm; the c value obtained in step 4 is obtained by multiplying the driving voltage value and grayscale value of the nozzle during inkjet, thereby increasing the inkjet amount; Step 5: Combining the obtained adhesive compensation result with the slicing information, and adjusting the content of the sprayed adhesive in real time during the printing process; Step 5 forms a corresponding matrix for each slice layer based on the slicing result using the obtained c value, and loads the matrix into the parameter control of the print head and combines it with the slicing information to achieve adhesive content compensation; Step 6: Store the printed sand mold in a cold storage.

2. The method for height control and precise regulation of frozen sand mold additive manufacturing in temporal space according to claim 1 is characterized by: In step 6, the printed frozen sand mold is placed in a cold storage for storage, and the usage time should not exceed 12 hours before or after the specified time.

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