Elevation control and precise regulation and control method for frozen sand mold additive manufacturing in time sequence space

Abstract

The invention relates to an elevation control and precise regulation and control method for frozen sand mold additive manufacturing in a time sequence space. According to the method, a mathematical model that the thickness of floating sand changes along with time due to moisture heat exchange of the frozen sand mold in air is established, and the thickness of the floating sand of frozen sand molds with different curved surfaces under the parameter conditions of different environment temperatures, time scales, sand mold materials, moisture contents and the like is predicted and fed back; and in the freezing printing process, real-time adhesive and height compensation is carried out on sand molds at different wall thicknesses, and the dimensional precision and geometric precision of the frozen sand molds are protected to a certain extent. According to the method, the problem of dimensional accuracy error caused by floating sand generated by heat exchange in air in the manufacturing and subsequent placing processes of the frozen sand mold is effectively solved, and the dimensional accuracy of the sand mold during casting is ensured.

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, and specifically to a method for accurately controlling the elevation in a frozen sand mold additive manufacturing process in a temporal space. Background Art

[0002] As an emerging casting mold manufacturing method, frozen sand mold additive manufacturing technology adopts the principle of phase change freezing of water-based adhesives at low temperatures, and forms sand molds by spraying, consolidating and stacking layer by layer. It has high precision and the ability to manufacture complex geometric shapes. However, during the manufacturing process of frozen sand molds, due to the influence of factors such as ambient temperature, sand mold material, and adhesive content, the adhesive of the frozen sand mold will gradually sublimate and disappear over time, and the bonding strength of the sand mold surface will decrease until the sand particles can no longer agglomerate together and become loose sand, the 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 even causes the frozen sand mold to no longer have the ability to be cast. Therefore, how to accurately control the elevation of the frozen sand mold and compensate for the change in floating sand thickness during the frozen sand mold additive manufacturing process is a problem that needs to be solved urgently. 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 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 comprises 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 features, 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 body 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 multiple 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 the inner cavity respectively, A and B are compensation multiple factors for the outer wall and the 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 slice 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 the time, but also optimizes the floating sand peeling speed according to the geometric shape of the curved surface, so that the floating sand peeling process is smoother and more uniform, and ultimately a more precise sand mold forming effect is achieved.

[0014] Further, the variation law of the floating sand height of the flat sand mold and the complex curved surface is shown in the following equation:

[0015] S1=Mt

[0016] S2=Nlogft+n

[0017] Wherein, S1 is the variation law of floating sand height of plane sand mold over time; S2 is the variation law of floating sand height of curved sand mold over time; M and N are the floating sand height multipliers of plane and curved sand mold respectively; t is the storage time of frozen sand mold; f is the base factor related to curvature; n is the floating sand height deviation compensation constant.

[0018] Furthermore, the minimum wall thickness of each part in step 1 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 body 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 riser and pouring system design, the exhaust system design and the cooling system design, etc.

[0020] When the structure of the sand mold is further inverted in step 2, the change law of the floating sand is pre-calculated through a digital analysis model according to the change characteristics of the floating sand height generated in different curvature areas of the sand mold over time, 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 with 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] Further, in step 5, the 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 realize the compensation of the adhesive content.

[0024] Further, in step 6, the printed frozen sand mold is placed in a cold storage and is best used within a specified time, preferably within 12 hours before and after the deviation.

[0025] The present invention mainly solves the technical problem that floating sand is caused by sublimation of adhesive during the production process of frozen sand molds, thereby affecting the accuracy and performance of the sand molds, and has the following advantages:

[0026] 1. Accurately compensate for the floating sand problem: 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, and maintain 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 when the adhesive is partially lost, thus avoiding defects in the casting due to deformation of the 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 the use period.

[0029] 4. Optimize the manufacturing process: In the manufacturing process, combined with slicing technology, the amount of adhesive injection can be accurately 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 It 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 is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the accompanying drawings, and the words "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively. Figure 1 and Figure 2 The figure is only for illustration. The casting mold is divided into unit grids according to the set requirements. When performing compensation operation, the unit grids of each outer wall surface and the unit grid close to the casting cavity are mainly concerned.

[0036] First, according to the structural characteristics of the frozen sand mold, the frozen sand mold riser and pouring system, exhaust system and cooling system are designed. For example, in practical applications, when casting large and complex parts, the main runner, cross runner and inner runner are considered, and different structural dimensions are designed respectively so that the metal liquid can flow smoothly into the mold cavity. At the same time, the exhaust system ensures that the gas is discharged smoothly to avoid the generation of pore defects, while the cooling system helps to control the temperature and ensure the quality of the molded parts. The height change law of the floating sand of the frozen sand mold is calculated and analyzed, and different degrees of height compensation are performed on different curvature areas considering the storage time and the surface geometry, so that the initial shape of the printed sand mold has different degrees of expansion at the corresponding position compared with 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 body with a 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 location and the outer wall and the inner cavity.

[0039] According to the obtained point information, the adhesive injection amount is compensated by changing the driving voltage value and grayscale value of the nozzle, and the slicing information is combined with the inkjet compensation amount for printing. After printing, 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 according to 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: Reverse 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 multiple 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 the inner cavity respectively, A and B are compensation multiple factors for the outer wall and the 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 slice 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 scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above technical features.

Claims

1. A method for height control and precise regulation of frozen sand mold 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, ensure the strength of the frozen sand mold, and select the appropriate three-dimensional contour inclusion size; Step 2: According to the selected inclusion body size, reverse the frozen sand mold modeling to generate a three-dimensional data model of the frozen sand mold. When reversely resolving the modeling, perform elevation compensation according to the following equation: S1=Mt S2=Nlog f t+n Where, S1 is the variation law of floating sand height of flat sand mold over time; S2 is the variation law of floating sand height of curved sand mold over time; M and N are the floating sand height multipliers of flat and curved sand molds respectively; t is the storage time of frozen sand mold; f is the base factor related to curvature; n is the floating sand height deviation compensation constant; Step 3: traverse and analyze the generated frozen sand mold three-dimensional data model to extract the location information of each point; 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 In the formula, c is the multiple 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 the inner cavity respectively, A and B are compensation multiple factors for the outer wall and the 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; Step 5: Combining the obtained adhesive compensation result with the slice information, and adjusting the content of the sprayed adhesive in real time during the printing process; 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 time sequence space according to claim 1 is characterized in that: In step 2, when inversely calculating the frozen sand mold shape, the floating sand peeling control technology based on curvature analysis compensates 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 the floating sand in storage, and finally achieving a more accurate sand mold forming effect.

3. The method for height control and precise regulation of frozen sand mold additive manufacturing in time sequence space according to claim 1 is characterized in that: The minimum wall thickness of each part in step 1 is a safety value obtained according to different sand mold materials and sand mold sizes to ensure the strength of the sand mold. The generated inclusion body is a solid cylinder or cuboid with a maximum safety value.

4. The method for height control and precise regulation of frozen sand mold additive manufacturing in time sequence space according to claim 1 is characterized in that: 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, the distance between the position and the outer wall and the inner cavity.

5. The method for height control and precise regulation of frozen sand mold additive manufacturing in time sequence space according to claim 1 is characterized in that: 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.

6. The method for altitude control and precise regulation of frozen sand mold additive manufacturing in time sequence space according to claim 1 is characterized in that: In step 5, the corresponding matrix of each slice layer is formed according to the slice result by using the obtained c value, and the matrix is ​​loaded into the parameter control of the print head and combined with the slice information to realize the compensation of the adhesive content.

7. The method for height control and precise regulation of frozen sand mold additive manufacturing in time sequence space according to claim 1 is characterized in that: The step 6 is to store the printed frozen sand mold in a cold storage and it is best to use it within the specified time, and the usage time should not exceed 12 hours before or after the specified time.

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