Process method for preparing soft chaplet of ceramic core

Abstract

The invention discloses a preparation process method of a soft chaplet of a ceramic core, and belongs to the field of additive manufacturing. The method comprises the steps of soft chaplet modeling and thickness definition; curved surface layering and path planning are carried out, layered slicing is carried out on the theoretical three-dimensional model of the soft core support, and a mixed layering method based on Boolean operation and a spiral slicing algorithm is adopted for layered slicing; according to a slicing result, a Zigzag path is adopted for filling, and an initial printing path of the soft core support is generated; technological parameters are optimized; and conformal printing. According to the method, the precise geometric processing capacity of Boolean operation and the continuous path generation concept of spiral slicing are combined, a mixed layering strategy is formed, and on the premise that the printing precision is guaranteed, the printing paths can be connected to the maximum extent, the idle stroke is reduced, and efficient and continuous printing is achieved.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing, specifically relating to a process for preparing ceramic core soft core supports. Background Technology

[0002] The wall thickness accuracy of hollow turbine blades directly determines the engine's performance and service safety. In the investment casting process, the spatial position of the ceramic core in the wax pattern mold is positioned and supported by a wax soft core support. Its fitting accuracy and dimensional consistency are key to controlling the wall thickness of the blade wax pattern.

[0003] The existing methods for preparing ceramic core soft core supports mainly have the following limitations and challenges: Traditional manual application method: Relying on the operator's experience, pre-made wax sheets of equal thickness are pasted onto the surface of the ceramic core. This method has problems such as poor consistency between the soft core support and the free-form surface of the ceramic core, low positioning accuracy, and low production efficiency. Moreover, it cannot meet the requirements of variable thickness soft core support for variable wall thickness blade design.

[0004] Early 3D printing methods: Existing publicly available technologies, although using 3D printing to prepare soft core supports and improving the level of automation, are essentially cylinders of fixed diameter cut from curved surfaces. The resulting soft core supports have a single geometric shape and fail to fundamentally achieve adaptive variable thickness design based on the gap between the ceramic core and the mold cavity. Their ability to compensate for individual manufacturing errors of the ceramic core is limited.

[0005] Existing printing path planning methods: While publicly available technologies focus on generating printing paths on freeform surfaces, their methods mostly follow the trajectory generation logic of traditional subtractive manufacturing (CAM), or are only applicable to single-layer printing. For multi-layer, variable-thickness conformal printing on complex freeform surfaces, there are problems such as path redundancy, long non-printing strokes, and low efficiency. Furthermore, they lack systematic coupling with material properties and process parameters.

[0006] Additive and subtractive composite processing methods: Existing technologies that combine additive and subtractive processes to improve final accuracy. However, the technical focus is on the integration of the physical platform and the subsequent subtractive finishing. There is a lack of in-depth and systematic solutions for the front-end additive manufacturing process, especially on how to improve the dimensional accuracy and surface quality of the printed blank directly from the source through optimized printing paths and precise process parameter control. This results in an over-reliance on subtractive processing and a long overall preparation cycle.

[0007] In summary, existing technologies have not yet provided a comprehensive process solution that can simultaneously address a series of interconnected technical challenges, including "accurate geometric modeling of variable-thickness soft core supports on freeform surfaces," "efficient and continuous conformal printing path planning without redundancy," and "systematic optimization of printing process parameters for high dimensional accuracy." Therefore, a novel and systematic method for fabricating soft core supports is urgently needed. Summary of the Invention

[0008] The technical problem to be solved: To overcome the shortcomings of existing technologies, this invention provides a method for preparing a ceramic core soft core support, ensuring that its upper and lower surfaces are precisely fitted to the mold cavity and the ceramic core surface, respectively. This achieves true adaptive variable thickness, guaranteeing positioning accuracy from a geometric perspective. This method combines the precise geometric processing capabilities of Boolean operations with the concept of continuous path generation for spiral slicing, forming a hybrid layering strategy. This strategy maximizes the connection of printing paths, reduces empty strokes, and achieves efficient continuous printing while ensuring printing accuracy.

[0009] The technical solution of this invention is: a process for preparing a ceramic core soft core support, comprising the following steps: Step 1: Soft core support modeling and thickness definition: Obtain the 3D model of the ceramic core and the cavity model of the wax mold. Construct the base model of the soft core support at a preset position on the free surface of the ceramic core model. Project the base model onto the cavity model along the normal direction. Define the theoretical 3D model and variable thickness of the soft core support using the adaptive spatial structure between the two models. Step 2, Surface Layering and Path Planning: The theoretical 3D model of the soft core support is sliced ​​into layers. The layering is done using a hybrid layering method that combines Boolean operations and spiral slicing algorithms. Based on the slicing results, Zigzag paths are used to fill the layers and generate the initial printing path for the soft core support. Step 3: Optimization of process parameters: Using orthogonal experimental design, combined experiments were conducted on four process parameters: printing temperature, extrusion pressure, printing layer height, and printing speed. Based on range analysis, the optimal combination of process parameters that achieves the best dimensional accuracy of the soft core support was determined. Step 4, Conformal Printing: Input the optimized initial printing path and the optimal process parameters into the conformal printing equipment to perform additive manufacturing of the soft core support on the free-form surface of the ceramic core. A further technical solution of the present invention is: the specific steps of projecting the base model onto the cavity model along the normal direction include: S11. Discretize the contour of the base model into several points. , ; S12, each point Projecting along the normal vector direction of the ceramic core surface onto the cavity model yields the corresponding projection point. ; S13, All projection points The spline curve is fitted to the surface of the cavity, which is the top surface of the soft core support. The spatial structure between the base model and the top surface is the theoretical three-dimensional model of the soft core support. A further technical solution of the present invention is: the specific method for performing layered slicing on the theoretical three-dimensional model of the soft core support is as follows: First, Boolean operations are used to determine the contact area between the printed model and the substrate ceramic core surface, and an offset is made along the normal of the contact surface to generate layered cut surfaces. On this basis, a spiral slicing algorithm is used to connect the printing paths of two consecutive layers end to end, forming a continuous spiral upward printing trajectory.

[0010] A further technical solution of the present invention is: a continuous spiral path is used in the region of gentle curvature of the surface, and in the region of abrupt curvature of the surface or steep features, a hybrid path combining spiral and inclination at an angle of less than 30° is switched. A further technical solution of the present invention is: after step 1 and before step 2, printing thickness compensation is performed. The upper surface of the theoretical three-dimensional model of the soft core support is offset along the normal by a compensation thickness to form a printed model for additive manufacturing, the compensation thickness being determined based on the allowance for subsequent subtractive processing. A further technical solution of the present invention is that the compensation thickness is 0.4 mm.

[0011] A further technical solution of the present invention is: the combination of process parameters that optimizes the printing dimensional accuracy of the soft core support is: printing temperature 70℃, extrusion pressure 0.016MPa, printing layer height 0.4mm, and printing speed 1000mm / min. A further technical solution of the present invention includes step 5, molding dimension detection and evaluation. The printed soft core support was measured at multiple points using a point laser measuring instrument. Its average thickness was calculated and compared with the thickness of the theoretical three-dimensional model to evaluate its dimensional accuracy. A further technical solution of the present invention is: the multi-point measurement involves selecting 9 points on each soft core support surface for measurement and taking the average value.

[0012] A ceramic core soft core support fabrication system, comprising: The modeling definition module is used to obtain the three-dimensional model of the ceramic core and the cavity model of the wax mold. At a preset position on the free surface of the ceramic core model, the adaptive variable thickness theoretical three-dimensional model of the soft core support is constructed by projecting the base model along the normal direction onto the cavity model. The path planning module, which is communicatively connected to the modeling definition module, is used to perform layer slicing and printing path planning on the adaptive variable thickness theoretical 3D model. The path planning module integrates a hybrid layering unit based on Boolean operations and spiral slicing algorithm, as well as a path generation unit that uses Zigzag to fill the path. The parameter optimization module stores the optimal combination of process parameters determined through orthogonal experiments and range analysis. The process parameters include at least printing temperature, extrusion pressure, printing layer height, and printing speed. The conformal printing execution module is communicatively connected to the path planning module and the parameter optimization module, respectively. It is used to receive the planned printing path and optimal process parameters, and drive the printing equipment to perform additive manufacturing of soft core support on the free-form surface of the ceramic core clamped on the fixture.

[0013] Beneficial effects The beneficial effects of this invention are as follows: The ceramic core soft core support preparation process and system provided by this invention, through the synergistic innovation of adaptive geometric modeling, intelligent path planning, and process parameter system optimization, bring the following significant beneficial effects: 1. This invention achieves true "tailor-made" variable thickness design by projecting the soft core support substrate onto the mold cavity using a geometric definition method. This makes the upper and lower surfaces of the soft core support the "negative shapes" of the ceramic core surface and the mold cavity, respectively. This effectively compensates for the manufacturing errors of the ceramic core itself and meets the requirements of the variable wall thickness structure of the blade, greatly improving the wall thickness accuracy of the precision casting wax pattern and the final blade parts from the source.

[0014] 2. The "Boolean operation + spiral slicing" hybrid layering algorithm adopted in this invention forms a continuous spiral upward printing trajectory by connecting the beginning and end of the paths between consecutive printing layers, thereby minimizing the non-printing empty travel between layers (such as lifting the blade and moving and positioning).

[0015] 3. This invention utilizes a systems engineering approach combining orthogonal experiments and range analysis to clarify the order of influence of four key parameters—temperature, air pressure, layer height, and speed—on printing dimensional accuracy, and obtains the optimal combination of process parameters (e.g., temperature 70℃, air pressure 0.016MPa, layer height 0.4mm, and speed 1000mm / min). This transforms the printing process of the soft core support from an experience-dependent "skill" into a quantifiable, predictable, and reproducible precision process, effectively suppressing dimensional deviations (such as bulging and material shortages) caused by parameter fluctuations, and fundamentally ensuring batch consistency and pass rate.

[0016] 4. The "printing thickness compensation" strategy proposed in this invention ensures that the dimensions of the printed soft core support blank are close to the final requirements to reduce milling allowance, while also reserving a stable and uniform finishing allowance. This lays a good foundation for subsequent efficient subtractive finishing, realizes seamless integration and complementary advantages between additive and subtractive processes, and forms a complete, reliable, and efficient digital manufacturing solution from digital model to high-precision entity.

[0017] In summary, through the synergistic effect of the above-mentioned technical features, this invention has successfully solved a series of key technical problems in preparing high-precision variable-thickness soft core supports on complex free-form surfaces. It has achieved breakthrough progress in terms of bonding accuracy, manufacturing efficiency, molding stability and process integration, which is of great significance for improving the manufacturing quality and yield of hollow turbine blades for aero-engines. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the conformal printing process in an embodiment of the present invention; Figure 2 This is a schematic diagram of the conformal printing slicing strategy in an embodiment of the present invention; Figure 3 This is a schematic diagram of the spiral slicing algorithm in an embodiment of the present invention; Figure 4 This is a schematic diagram of the Zigzag filling method in an embodiment of the present invention; Figure 5 This is a schematic diagram of the soft core support model in an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the calculation of the soft core support surface dimensions in an embodiment of the present invention; Figure 7 This is a schematic diagram of the printed soft core support model in an embodiment of the present invention; Figure 8 This is a schematic diagram of the soft core support preparation equipment in an embodiment of the present invention; Figure 9 This is a schematic diagram of the thickness definition points of the soft core support printing model in an embodiment of the present invention; Figure 10 This is a schematic diagram of the soft core support printing process in an embodiment of the present invention; Figure 11 This is a statistical chart of the average thickness of the soft core support in the experimental group in this embodiment of the invention; Figure 12 This is a comparison chart of the printed results of two sets of parameters after an orthogonal experiment. Detailed Implementation

[0019] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Since the surface of ceramic cores is mostly irregular curved, conformal printing technology can achieve uniform coating on surfaces with arbitrary curvature. Furthermore, conformal printing can achieve in-situ bonding between functional layers and substrates, avoiding problems such as stress concentration caused by bonding processes. Therefore, after adjusting the spatial orientation, conformal printing technology is used, taking into account the characteristics of the printing substrate itself, the matching issues between the printing trajectory and the substrate. To perform additive manufacturing on curved parts, the first step is to solve the forming problem of the parts. Therefore, it is necessary to perform reasonable layering of the curved parts to reduce the step effect and strengthen the internal structural strength of the parts. After comparing several common surface layering methods, Boolean operations are finally selected to perform surface layering on the parts. Since processing efficiency and processing time need to be considered in the actual processing process, it is necessary to optimize the printing path. After setting various printing parameters, the printing path is optimized, with a focus on optimizing the interlayer movement path to improve processing efficiency. To address the issues of density and structural strength in additively manufactured workpieces, a suitable infill path is required. Compared to other common infill paths, the Zigzag path stands out due to its simple printing path, good contour coverage, and high printing accuracy maintained by its straight path and single axis of motion during printing. Since the thickness of the soft core support varies at different locations, and the upper surface of the soft core support is based on the wax pattern surface and the lower surface is based on the ceramic core surface, both of which are free planes, it is difficult to define an accurate height value. Therefore, it is necessary to use the method of taking the average of nine points to define the thickness of the soft core support. To address the dimensional accuracy issues in the fabrication of soft core supports, it is necessary to consider the impact of various process parameters on workpiece forming during additive manufacturing. The process parameters are optimized through orthogonal experiments. Finally, point laser measurements are performed on the workpieces fabricated under various combinations of process parameters. After analyzing each process parameter based on the range method, the optimal level and optimal combination are obtained. Based on the above problems, this invention explores suitable printing technologies, printing path planning methods, workpiece thickness definition methods, and combinations of process parameters, thereby obtaining a reasonable soft core support fabrication process. Its main advantages are improved dimensional accuracy in soft core support additive manufacturing by controlling process parameters, and increased processing efficiency by optimizing the printing path. Existing research mainly focuses on conformal printing principles and 3D printing path planning, lacking exploration of process parameters during the printing process and insufficient detail and practicality in the specific printing process. Based on existing research, this invention proposes a practical soft core support fabrication process, including the following steps: Step 1: Soft core support modeling and thickness definition: Obtain the 3D model of the ceramic core and the cavity model of the wax mold. Construct the base model of the soft core support at a preset position on the free surface of the ceramic core model. Project the base model onto the cavity model along the normal direction. Define the theoretical 3D model and variable thickness of the soft core support using the adaptive spatial structure between the two models. Step 2, Surface Layering and Path Planning: The theoretical 3D model of the soft core support is sliced ​​into layers. The layering is done using a hybrid layering method that combines Boolean operations and spiral slicing algorithms. Based on the slicing results, Zigzag paths are used to fill the layers and generate the initial printing path for the soft core support. Step 3: Optimization of process parameters: Using orthogonal experimental design, combined experiments were conducted on four process parameters: printing temperature, extrusion pressure, printing layer height, and printing speed. Based on range analysis, the optimal combination of process parameters that achieves the best dimensional accuracy of the soft core support was determined. Step 4, Conformal Printing: Input the optimized initial printing path and the optimal process parameters into the conformal printing equipment to perform additive manufacturing of the soft core support on the free-form surface of the ceramic core.

[0022] This invention also proposes a ceramic core soft core support preparation system, comprising: The modeling definition module is used to obtain the three-dimensional model of the ceramic core and the cavity model of the wax mold. At a preset position on the free surface of the ceramic core model, the adaptive variable thickness theoretical three-dimensional model of the soft core support is constructed by projecting the base model along the normal direction onto the cavity model. The path planning module, which is communicatively connected to the modeling definition module, is used to perform layer slicing and printing path planning on the adaptive variable thickness theoretical 3D model. The path planning module integrates a hybrid layering unit based on Boolean operations and spiral slicing algorithm, as well as a path generation unit that uses Zigzag to fill the path. The parameter optimization module stores the optimal combination of process parameters determined through orthogonal experiments and range analysis. The process parameters include at least printing temperature, extrusion pressure, printing layer height, and printing speed. The conformal printing execution module is communicatively connected to the path planning module and the parameter optimization module, respectively. It is used to receive the planned printing path and optimal process parameters, and drive the printing equipment to perform additive manufacturing of soft core support on the free-form surface of the ceramic core clamped on the fixture.

[0023] The above technical solution will be further explained below with reference to the accompanying drawings: In one embodiment, the optimization process of the preparation method involved in this invention mainly includes the following steps: Step 1: Adaptive geometric modeling and thickness definition of the soft core support: First, obtain the 3D model of the ceramic core to be processed and the cavity model of the wax mold. Since both the ceramic core surface and the wax model surface are complex free-form surfaces, the thickness of the soft core support is variable and cannot be defined by a single value. The milling thickness of the soft core support can be determined by its positioning action in the mold. Assuming that the initial and final positions of the soft core support positioning points are square on the projection plane, its thickness should be the spatial distance between the selected areas of the two surfaces—the ceramic core surface and the wax model surface. Therefore, this embodiment uses the projection method to accurately calculate the geometry and thickness of the soft core support. The specific steps are as follows (see...). Figure 6 ): Step 1: Project the final position area of ​​the soft core support onto the ceramic core blade profile along the projection direction to obtain the lower surface of the soft core support; Step 2: Shape the ceramic core surface curve Discretized into several points Project the image onto the mold cavity surface along the normal direction of the ceramic core surface at each point. The projection point is... ; Step 3: Project the points Fit to spline curve The cavity surfaces they enclose are the top surfaces of the soft core support. Thus, the hexahedron formed by the lower surface (ceramic core surface), the upper surface (mold cavity surface), and the four side surfaces constitutes the three-dimensional model of the adaptive variable thickness theory of the soft core support (see...). Figure 5 ).

[0024] After calculating the milling thickness of the soft core support, its printing thickness should be adjusted based on the milling thickness. However, in order to improve milling efficiency, it is necessary to ensure that the height of the soft core support is as close as possible to the final required size. Therefore, the printing thickness of the soft core support should be based on the upper surface of the milled soft core support offset by 0.4mm (the theoretical layer height of the 0.05mm nozzle is recommended not to exceed 80% of the nozzle diameter) as a new printing model, which can be approximated as a cube.

[0025] Step 2: Trajectory planning based on hybrid hierarchical and optimized paths: Based on the spatial pose of the ceramic core, conformal printing trajectory planning is performed to precisely control the printing position and printing gap during the printing process. Conformal printing needs to consider the characteristics of the printing substrate itself and the matching between the printing trajectory and the substrate. Toolpaths need to be generated after parameters such as printing layer height, printing gap, and printing speed are selected.

[0026] Secondly, additive manufacturing requires careful consideration of part forming, necessitating the selection of a suitable surface layering method. Comparing various layering methods, Boolean operations are chosen. Existing research lacks Boolean-guided spiral algorithm path planning. This invention aims to combine Boolean operations with the spiral algorithm to optimize the printing path and improve printing efficiency. Based on existing surfaces and the model to be layered, Boolean operations are performed to obtain the surface layers, primarily including the following: First, assuming the base surface is a parametric surface S(u,v), the contact area between the bottom surface of the printed model and the base is determined by the Boolean intersection operation between the two. In UG, the contact surface can be extracted using a discrete mesh intersection algorithm, and its mathematical description is as follows: (1) in: —M represents the printed model; —B is the base surface; —D is the parameter field; —Ω represents the contact surface parameter region; Secondly, UG's geometry engines (such as Parasolid) typically use voxel rasterization to extract contact surfaces. Let the voxel resolution be Δ, and the contact surface be discretized into a point set { }, the normal vector of each point Calculated using the local differential of the base surface S(u,v): (2) Offset along the normal direction to generate layered sectional surfaces is essentially the construction of equidistant surfaces on the base surface. For the parametric surface S(u,v), the k-th layer sectional surface... The mathematical expression is: (3) in: —d(u,v) is an adaptive layer thickness function, which is determined by curvature constraints and process parameters; —k is the layer number (k=0 is the contact surface); To avoid self-intersection and geometric distortion during the biasing process, the layer thickness d(u,v) must satisfy curvature constraints. According to the curvature limit criterion in differential geometry, the maximum permissible layer thickness is: (4) Where k1 and k2 are the principal curvatures of the printed surface.

[0027] Based on Boolean operations, a surface layering algorithm is used to slice the soft core support. To reduce non-printing paths and improve printing efficiency, a spiral slicing algorithm is incorporated. Layers are constructed using continuous spiral paths along the Z-axis or other directions, avoiding the obvious seams between layers found in traditional slicing, resulting in a smoother surface during printing. Since spiral slicing requires continuous inclined paths, but Boolean operations can generate local steep features (such as vertical surfaces), the curvature of the spiral line needs frequent adjustments, affecting speed stability. Continuous spiral paths are used in gentle areas, while steep areas switch to a hybrid path of "spiral + small-angle inclination" to avoid abrupt curvature changes. This also maintains as many continuous printing segments as possible, reducing transition paths between different printing layers. The spiral slicing algorithm is suitable for single-pass, multi-layer, thin-walled parts. For the soft core support, which is fabricated on a ceramic core surface through multi-layer, multi-pass printing, a Boolean-based surface layering algorithm is used for slicing. During the process, the beginning and end of two consecutive layers are connected sequentially to form a continuous trajectory. That is, the slice ends are connected only during trajectory planning between layers, directly moving up one layer.

[0028] After completing the surface layer slicing, set the fill path according to the slice data. Select the Zigzag path, which is simple and direct, has good contour area coverage, and improves printing accuracy because the travel path is straight and only a single motion axis moves during the printing process.

[0029] The soft core support model is built as a 5×5 block. Since both the ceramic core surface and the wax model surface are free-form surfaces, the specific thickness of the soft core support cannot be measured by a definite value. Furthermore, the final size of the soft core support is guaranteed by subtractive material processing. It is sufficient to print the size as long as it exceeds the size after milling to initially meet the requirements.

[0030] For the repaired soft core support model, surface layer slicing based on Boolean operations is used to obtain slice data, Zigzag filling method is used to complete the soft core support trajectory planning, and conformal printing equipment modeling and trajectory generation verification are completed based on the surface additive manufacturing module in UG / CAM: First, a printhead envelope block model is created based on the actual printhead size, and then imported into the fixture model to facilitate interference checks later.

[0031] Next, set the necessary printing parameters such as layer height and infill density to generate the soft core support tool rail, and check for interference based on the previous model's running trajectory.

[0032] Since the soft core support is prepared using granular wax as the printing material and needs to be printed on the surface of the ceramic core, and the surface of the ceramic core is a free-form surface, the mainstream printers on the market cannot meet the printing requirements. Therefore, this experiment uses a self-developed 3D printing equipment: a turbine blade ceramic core soft core support additive and subtractive manufacturing platform. The stroke of the 3D printing equipment X / Y / Z is 600mm / 500mm / 400mm.

[0033] The soft core support conformal printing uses a special fixture with a core positioning design. Its unique structure requires consideration of the fixture structure to prevent interference during trajectory planning. The printing nozzle uses a pneumatic principle, using air pressure to extrude molten wax from the nozzle.

[0034] Since the thickness of the soft core support at different locations is determined by both the ceramic core surface and the wax pattern surface, the thickness of the soft core support varies at different locations. Furthermore, the bottom surface of the soft core support is based on the ceramic core surface, and the top surface is based on the wax pattern surface. Both of these are free-form surfaces, making it difficult to define a specific height value.

[0035] In the experiment, nine points were planned on the upper surface of the ceramic core based on point laser measurement. The distance from each point to the edge was 1.5 mm, and the spacing between the points was 1 mm. The average distance from each point to the surface of the ceramic core was measured and taken as the theoretical thickness value of the printed ceramic core. This value was compared with the actual thickness value of the printed model obtained by actually marking points at the same locations to define the thickness of the soft core support.

[0036] In the printing experiment, since there are twelve soft core supports on the surface of the ceramic core, the thickness at different positions cannot be uniform. Therefore, a total of 108 sets of data were measured at all soft core support measurement points as the reference theoretical value for each set of experimental parameters. Finally, 1.4964mm was taken as the theoretical reference value for printing soft core supports.

[0037] Step 3: Optimization of process parameters based on orthogonal experiments: Based on the experimental equipment and trajectory generation method, the main process parameters affecting the soft core support fabrication process are temperature, air pressure, layer height, and printing speed. Therefore, four factors were selected in the experiment: temperature, air pressure, layer height, and printing speed. A four-level orthogonal experiment was conducted to explore the soft core support printing process. A total of 16 experiments were required, and L16 (4) was selected. 4 Orthogonal experimental table; Step 4: Conformal printing execution: Other printing parameters set in the printing gap test experiment were: temperature 70℃, air pressure 0.016MPa, layer height 0.4mm, printing speed 1000mm / min, filling algorithm "zigzag", and the experimental equipment was a ceramic core soft core support additive and subtractive material processing platform. After printing the soft core supports for 16 sets of experiments, and waiting for them to cool to room temperature, nine points on the surface of each printed soft core support were measured using a point laser. A total of 108 sets of data were measured for each soft core support at different positions for each set of processing parameters, and the average height of the printed soft core support was calculated. The dimensional accuracy analysis of orthogonal experiments based on the range method is divided into three steps: First, calculate the mean value of each factor level; second, calculate the range of each factor level; and finally, obtain the order of influence of the factors based on the range value, and obtain the optimal combination of the optimal levels based on the mean value of each factor. The optimal combination of process parameters obtained from orthogonal experiments was compared with the worst combination of process parameters obtained from height error analysis. The comparison results showed that under the optimal combination of process parameters, the overall size of the soft core support was regular and the control precision was high, with an average height of 1.6056 mm for the printed soft core support. However, under the worst combination of process parameters, filament accumulation caused bulging on the surface, resulting in an excessively thick soft core support, with an average height of 1.8988 mm for the printed soft core support. This process utilizes conformal printing technology based on theoretical spatial pose and employs a Boolean operation-spiral slicing algorithm to optimize the movement path between layers, reduce non-printing paths, and increase printing efficiency. It completes layered slicing based on freeform ceramic core surfaces and uses the Zigzag filling algorithm to perform path planning for each layer after slicing to generate soft core support printing trajectories. This process proposes a soft core support thickness definition model. Based on the generated printing trajectory, it analyzes the influence of temperature, air pressure, layer height, and printing speed parameters on the soft core support thickness. An orthogonal experimental group is set up, and the results are analyzed using the range method to obtain the order of importance of the influence accuracy of each parameter and the optimal combination method.

[0038] Table 1 Factor Level Values

[0039] Table 2 Orthogonal Experimental Scheme

[0040] In one embodiment, refer to Figure 1 As shown, the conformal printing process for preparing ceramic core soft core supports in this technology includes the following steps; Step 1: Based on the Boolean operation-based surface layering algorithm, complete the layering and slicing of the soft core support, such as... Figure 2 As shown, in order to reduce non-printing paths in the trajectory and improve printing efficiency, a spiral slicing algorithm is combined, such as... Figure 3As shown, its core idea is to design the slicing layers as spirals, rather than traditional planar slices. The main feature of the spiral slicing algorithm is that it builds layers by creating a continuous spiral path along the Z-axis or other directions, avoiding the obvious seams between layers that exist in traditional slicing, thus achieving a smoother surface during printing; Step two: After completing the surface layer slicing in step one, set the fill path based on the slice data, selecting the Zigzag path as the fill path, such as... Figure 4 As shown; Step 3: Determine the theoretical model of the soft core support, which is a 5×5 block, such as... Figure 5 As shown; Step four: Define the milling thickness of the soft core support. Assume that the initial and final locations of the soft core support positioning points are square on the projection plane, and its thickness should be the spatial distance between the selected areas of the ceramic core surface and the wax model surface. Therefore, the dimensions of the soft core support can be calculated using the following method: Figure 6 As shown.

[0041] (1) Project the final position area of ​​the soft core support onto the ceramic core blade surface along the projection direction to obtain the lower surface of the soft core support.

[0042] (2) The ceramic core surface curve Discretized into several points Project the image onto the mold cavity surface along the normal direction of the ceramic core surface at each point. The projection point is... .

[0043] (3) Project the point Fit to spline curve The cavity surfaces they enclose are the top surfaces of the soft core support. (Cube) It refers to the actual size of the soft core support.

[0044] Step 5: After calculating the milling thickness of the soft core support, its printing thickness should be adjusted based on the milling thickness. However, to improve milling efficiency, it is necessary to ensure that the height of the soft core support is as close as possible to the final required size. Therefore, the printing thickness of the soft core support should be based on a 0.4mm offset from the upper surface of the milled soft core support (the theoretical layer height of a 0.05mm nozzle is recommended not to exceed 80% of the nozzle diameter) as the new printing model. The adjusted printing soft core support model is as follows: Figure 7 As shown, it can be approximated as a cube; Step Six: Because the soft core support preparation uses granular wax as the printing material and needs to be printed on the surface of a ceramic core, and the surface of the ceramic core is a free-form surface, mainstream printers on the market cannot meet the printing requirements. Therefore, a self-developed 3D printing device was used in the experiment, such as... Figure 8As shown, the average distance from the point of measurement to the surface of the ceramic core is taken as the theoretical thickness value of the printed ceramic core. This is compared with the actual thickness value of the printed model obtained by actual dot measurement at the same location. The thickness of the soft core support is defined as follows: Figure 9 As shown; Step 7: Conduct soft core support preparation experiments. Orthogonal experiments on the soft core support process parameters are performed on a ceramic core / soft core support additive / subtractive material integration platform. The printing process is as follows: Figure 10 As shown in Table 1. This experiment selected four factors: temperature, air pressure, layer height, and printing speed. A four-level orthogonal experiment was conducted to explore the soft core support printing process. The level values ​​of each factor are shown in Table 1. A total of 16 experiments need to be completed, using L16 (4 4 The orthogonal experimental tables are shown in Table 2.

[0045] Step 8: After printing the soft core supports for 16 sets of experiments, wait for them to cool to room temperature, and then use a point laser to measure nine points on the surface of each printed soft core support, such as... Figure 2 As shown, a total of 108 sets of data were measured for the soft core support at different positions for each set of processing parameters. The average height of the printed soft core support was calculated, and the measurement results are as follows. Figure 11 As shown.

[0046] Step nine: Compare the optimal process parameter combination A3B1C2D3 obtained from the orthogonal experiment with the worst process parameter combination A4B4C4D1 obtained from the height error analysis again. Figure 12 As shown in the comparison results, under the optimal process parameter set, the overall size of the soft core support is regular and the control precision is high. However, under the worst process combination, the soft core support exhibits obvious stacking. The experiment shows that the process parameter set obtained by orthogonal experiment matches the experimental results.

[0047] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A process for the preparation of a ceramic core soft core former, characterized in that The method comprises the following steps: Step 1, soft core modeling and thickness definition: obtaining a three-dimensional model of a ceramic core and a cavity model of a wax mold, constructing a base model of a soft core at a preset position on a free surface of the ceramic core model, projecting the base model along a normal direction to the cavity model, and defining a theoretical three-dimensional model and a variable-thickness size of the soft core based on an adaptive space structure between the two models; Step 2, curved surface layering and path planning: layering and slicing the theoretical three-dimensional model of the soft core, wherein the layering and slicing adopts a hybrid layering method based on Boolean operation combined with spiral slicing algorithm; According to the slicing result, Zigzag path is used for filling to generate the initial printing path of the soft core; Step 3, process parameter optimization: combining experiments of four process parameters of printing temperature, extrusion air pressure, printing layer height and printing speed by orthogonal experiment method; and determining the process parameter combination that optimizes the printing size precision of the soft core based on range analysis method; Step 4, conformal printing: inputting the optimized initial printing path and the optimal process parameter combination into a conformal printing equipment to perform additive manufacturing of the soft core on the free surface of the ceramic core.

2. The process of claim 1 wherein: The specific steps of projecting the base model along the normal direction to the cavity model comprise: S11, discretizing the contour of the base model into a number of points , ; S12, projecting each point along the normal vector direction of the ceramic core surface where the point is located to the cavity model to obtain the corresponding projection point ; S13, all the projection points fitting into a spline curve, the spline curve enveloping the cavity surface is the top surface of the soft core, and the space structure between the base model and the top surface is the theoretical three-dimensional model of the soft core.

3. The process of claim 1 wherein: The specific method for layering and slicing the theoretical three-dimensional model of the soft core comprises: First, the contact area of the printing model and the base ceramic core surface is determined by Boolean operation, and the contact surface normal is offset to generate a layered surface; on this basis, the spiral slicing algorithm is adopted to connect the printing paths of two continuous layers, forming a continuous spiral ascending printing track.

4. The process of claim 3 wherein: In the area with gentle curvature of the curved surface, the continuous spiral path is adopted, and in the area with sudden change of curvature or steep features of the curved surface, the hybrid path combining spiral and inclination less than 30° is switched.

5. The process of claim 1 wherein: After step 1 and before step 2, printing thickness compensation is performed: The upper surface of the theoretical three-dimensional model of the soft core is offset by a compensation thickness along the normal direction to form a printing model for additive manufacturing, and the compensation thickness is determined based on the allowance of subsequent subtractive machining.

6. The process of claim 5 wherein: The compensation thickness is 0.4 mm.

7. The process of claim 1 wherein: the ceramic core is a soft core. The process parameter combination that optimizes the printing size precision of the soft core is: printing temperature 70℃, extrusion air pressure 0.016MPa, printing layer height 0.4mm, and printing speed 1000mm / min.

8. The process of claim 1 wherein: the ceramic core is a soft core. 5 It further comprises step 5, forming size detection and evaluation: A point laser measuring instrument is used to measure the printed soft core at multiple points, calculate the average thickness, and compare it with the thickness of the theoretical three-dimensional model to evaluate the size precision.

9. The process of claim 8 wherein: The multiple point measurement is to select 9 points on each surface of the soft core for measurement and take the average value.

10. A system for making a ceramic core soft core former, for carrying out the method of making a ceramic core soft core former according to any one of claims 1 to 9; characterized by It comprises: A modeling definition module is configured to obtain a three-dimensional model of a ceramic core and a cavity model of a wax mold, construct an adaptive variable-thickness theoretical three-dimensional model of a soft core by projecting a base model along a normal direction to the cavity model at a preset position on a free surface of the ceramic core model; The path planning module is connected in communication with the modeling definition module, and is used for layering and slicing and printing path planning of the adaptive variable-thickness theoretical three-dimensional model; the path planning module is integrated with a hybrid layering unit based on Boolean operation and spiral slicing algorithm, and a path generation unit using Zigzag filling path; The parameter optimization module stores an optimal process parameter combination determined through orthogonal experiment and range analysis, and the process parameters at least include printing temperature, extrusion gas pressure, printing layer height and printing speed; The conformal printing execution module is connected in communication with the path planning module and the parameter optimization module respectively, and is used for receiving the planned printing path and the optimal process parameter, and driving the printing equipment to perform soft core support additive manufacturing on the ceramic core free-form surface clamped on the clamp.

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