Casting head system wax mold designing and processing method based on photocuring forming

Abstract

The invention relates to a casting head system wax mold design and processing method based on photocuring molding, which comprises the following steps: constructing an annular riser wax mold three-dimensional model and a sprue wax mold three-dimensional model based on a casting process construction drawing of a closed impeller structure casting; designing a three-dimensional model of an annular riser wax mold and a three-dimensional model of a sprue wax mold corresponding to the constructed three-dimensional model of the annular riser wax mold and the three-dimensional model of the sprue wax mold on the basis of the structural characteristics of rotary bodies of the annular riser wax mold and the sprue wax mold; setting structural parameters of the three-dimensional models of the annular riser wax pattern mold and the sprue wax pattern mold, namely sequentially determining a bottom supporting structure, determining an internal supporting structure, setting an inclined printing angle and setting slicing parameters of the three-dimensional models, and finally forming a model which can be used for printing; and importing the model into a photocuring forming machine, and arranging and printing the model according to the spatial size of the photocuring forming machine.

Description

Technical Field

[0001] The invention relates to a design and processing method of a wax mold for a pouring and riser system based on photocuring molding, and belongs to the technical field of casting molds. Background Art

[0002] Investment casting technology offers numerous advantages, including low manufacturing costs, high dimensional accuracy, and low surface roughness, making it widely used in the production of aerospace components. With the significant increases in thrust and thrust-to-weight ratio of liquid rocket engines, the service environments they face are becoming increasingly demanding. Consequently, investment casting of high-temperature alloys and high-strength stainless steels is increasingly being used. This typically requires multiple rounds of process design and optimization. The gating and riser system (risers and runners) is essential tooling for investment casting process optimization and casting production. In actual production, mass-produced wax patterns for these systems require die pressing, typically made of metal materials such as steel or aluminum alloy. However, the long production cycles and high costs associated with metal die casting make them suitable only for mass-produced products and unsuitable for new structural high-temperature alloys and high-strength stainless steel castings. Before the process plan for new structural high-temperature alloys and high-strength stainless steel castings is finalized, it is necessary to continuously optimize and adjust the process plan and process parameters based on the non-destructive testing results of the castings (including X-ray testing results and fluorescent penetrant testing results). Accordingly, it is necessary to manufacture wax molds of the pouring and riser system (risers and runners) with different shapes or sizes multiple times.

[0003] Typically, wax patterns for the gating and riser systems (risers and sprues) are often made using wooden or putty molds, or using SLS (selective laser sintering) to directly fire wax patterns for risers and sprues made from PSB powder. Wooden molds are traditionally handcrafted, requiring years of experience by professional foundry mold technicians to create relatively successful molds. However, these molds are subject to long production cycles, relatively poor dimensional consistency, easy deformation, low surface roughness, and poor heat dissipation. Consequently, production efficiency is low when using wooden molds for wax pattern preparation. Putty molds require a wooden counter-mold, which requires high manual skill. Furthermore, the finished putty molds are heavy and laborious to operate. Wax patterns pressed using the molds cool slowly, resulting in long demolding times and low production efficiency. Using SLS (selective laser sintering) to directly fire PSB powder wax patterns for risers and sprues results in higher production costs. In view of the above problems, there is an urgent need for a method for quickly making a wax mold mold for a pouring and riser system (riser and runner) for investment precision castings to solve this production process problem.

[0004] SLA (stereolithography) is based on the principle of photopolymerization of liquid photosensitive resin. Using the CAD model of the part being manufactured as the foundation, the model is discretized into layered data using layering software. This data is then input into a stereolithography machine, where a UV laser beam with a controlled trajectory irradiates the surface of the liquid photosensitive resin, causing it to photocured and cross-link from point to line, and then from line to surface. After completing the drawing of one layer, the molding table moves vertically by one layer height to solidify another layer. This cycle repeats, layer by layer, ultimately forming a three-dimensional solid. Photosensitive resin molds prepared using SLA (stereolithography) boast high dimensional accuracy and excellent dimensional stability. Summary of the Invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the existing technology, and to propose a wax mold design and processing method for a pouring and riser system based on photocuring molding, which can accelerate the cooling speed of the wax mold, improve the surface quality of the wax mold, make the demoulding operation simpler and smoother, reduce the labor intensity of the operator, and can significantly improve production efficiency, and has great promotion and application value.

[0006] The technical solution of the present invention is: a design and processing method of a wax mold for a pouring and riser system based on photocuring molding, comprising:

[0007] Based on the casting process construction drawings of the closed impeller structure casting, a 3D wax mold model of the annular riser and a 3D wax mold model of the sprue were constructed;

[0008] Based on the rotary structure characteristics of the annular riser wax mold and the sprue wax mold, the 3D models of the annular riser wax mold and the sprue wax mold corresponding to the 3D models of the annular riser wax mold and the sprue wax mold are designed and constructed;

[0009] Set the structural parameters of the 3D models of the annular riser wax mold and the sprue wax mold, that is, determine the bottom support structure, determine the internal support structure, set the tilt printing angle, and set the 3D model slicing parameters in sequence, and finally form a model that can be used for printing;

[0010] The model is imported into the stereolithography machine, and the model is arranged and printed according to the spatial dimensions of the stereolithography machine.

[0011] The annular riser wax mold is a split structure, assembled from a center column, an outer ring, and a base. The three parts are assembled to ensure spatial positioning. The center column and the outer ring are assembled on the lower end face of the center column to ensure positioning, and the outer ring and the base are assembled on the lower end face of the outer ring to ensure positioning.

[0012] The straight runner wax mold is an integral structure with two water injection cooling holes on the upper end surface, which also serve as discharge holes for the residual photosensitive resin in the inner cavity of the photosensitive resin mold, and are used to pour out the residual resin in the mold cavity after the photosensitive resin mold is printed.

[0013] The center column is set to have an inclined printing angle of 30°, the outer ring is set to have an inclined printing angle of 15-20°, and the base is not set to have an inclined printing angle.

[0014] The bottom support heights of the central column, outer ring, and base are all 9-10 mm, and the internal support structure is a honeycomb structure.

[0015] The bottom support height of the sprue wax mold 3D model is 9-10mm, the internal support structure is a honeycomb structure, and no tilt printing angle is set.

[0016] The printing material used is C-UV9400A photosensitive resin, and the printing layer thickness is 0.1mm.

[0017] After printing, the surfaces of the annular riser wax mold and the sprue wax mold are cleaned of residual photosensitive resin, support removed, secondary cured, and surface polished.

[0018] The secondary curing time is 20-40 minutes; when the secondary curing is completed and the polishing operation is performed, fine sandpaper with a mesh size of 150-400 mesh is used.

[0019] The beneficial effects of the present invention compared with the prior art are:

[0020] (1) The present invention provides a method for making a wax mold for a sprue system of an investment casting based on photocuring molding. By adopting an efficient digital processing and manufacturing process, a wax mold for an annular riser and a wax mold for a sprue made of a photosensitive resin material are made using a photocuring molding machine. The wax molds have smooth surfaces, high dimensional accuracy, and good dimensional stability, which can greatly shorten the production time of the wax molds for the annular riser and the sprue.

[0021] (2) The present invention provides a method for making a wax mold for a pouring and riser system of an investment casting based on photocuring molding. The annular riser wax mold and the straight runner wax mold made by using the wax mold have low surface roughness and good dimensional consistency. Moreover, compared with the wax mold made by using traditional wooden molds or putty molds, the wax mold demoulding operation is simpler and smoother, which can significantly improve production efficiency. The method can be widely used in the design of process solutions for new structural high-temperature alloys and high-strength stainless steel castings, and has good promotion and application value.

[0022] (3) The present invention provides a method for manufacturing a wax mold for a sprue system of an investment casting based on photocuring. By arranging an internal support structure and a water injection cooling port on the annular riser wax mold and the sprue wax mold, not only can the strength of the annular riser wax mold and the sprue wax mold be enhanced, but they can also serve as a water storage cavity, which can significantly increase the cooling rate of the annular riser wax mold and the sprue wax mold, and greatly shorten the demoulding time and production cycle of the annular riser wax mold and the sprue wax mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of the annular riser wax mold and sprue wax mold implemented in the present invention;

[0024] Figure 2 This is a schematic structural diagram of the annular riser wax mold implemented in the present invention;

[0025] Figure 3 Schematic diagram of the sprue wax mold structure implemented in the present invention, wherein (a) is an overall schematic diagram, and (b) is a cross-sectional schematic diagram; DETAILED DESCRIPTION

[0026] A closed impeller casting consists of a hub, a front cover, a rear cover, a front shoulder, a rear shoulder, and several three-dimensional twisted blades. The casting process adopts a top-injection casting system, and the pouring and riser system (risers and runners) consists of straight runners and ring risers. Since the process plan and process parameters need to be continuously adjusted and optimized according to the product non-destructive testing results (X-ray test results, fluorescent penetrant test results) in the later stage, the structural shape and size of the straight runner and ring riser also need to be optimized and adjusted multiple times. First, based on the casting process construction drawing of the closed impeller structure casting (a graphic to express the casting process plan), a three-dimensional model of the pouring and riser system (risers and runners) is constructed, and finally the pouring and riser system (risers and runners) used is determined.

[0027] The wax molds are the annular riser wax mold 5 and the sprue wax mold 6, both of which are rotating body structures. The schematic diagram of the three-dimensional model structure is shown in Figure 1 shown.

[0028] The present invention proposes a method for designing and processing a wax mold for a pouring and riser system based on photocuring. The method specifically includes the following steps:

[0029] Based on the rotary structure characteristics of the annular riser wax mold and the sprue wax mold, the corresponding annular riser wax mold and sprue wax mold are designed. This process requires full consideration of many factors such as the structure, shape, angle and size of the annular riser wax mold and the sprue wax mold.

[0030] Since both the ring riser wax mold and the sprue wax mold are rotating body structures, but the shape and structure of the ring riser wax mold are relatively complex, the ring riser wax mold is designed as a split structure, and the ring riser wax mold is formed by combining multiple block molds. At the same time, a certain draft angle needs to be added inside the ring riser wax mold to facilitate the smooth removal of the ring riser wax mold during the later production of the ring riser wax mold. Because the shape and structure of the sprue wax mold are relatively simple, the sprue wax mold is finally designed as an integral structure. At the same time, a certain draft angle needs to be added inside the sprue wax mold to facilitate the smooth removal of the sprue wax mold during the later production of the sprue wax mold. Ring grooves are used to assemble and position the multiple block molds of the ring riser wax mold.

[0031] In order to increase the cooling speed of the ring riser wax mold and the sprue wax mold and shorten the wax mold production time, cooling water needs to be injected into the inner cavity before using the ring riser wax mold and the sprue wax mold. The water injection cooling holes are all on the upper end surface of the wax mold.

[0032] The final schematic diagram of the three-dimensional model of the annular riser wax mold is shown in Figure 2 As shown, it is assembled by the middle column 1, the outer ring 2, and the base 3. Two Φ20mm water-injected cooling holes are set on the upper end faces of the middle column, the outer ring and the base. The spatial positioning relationship between the three parts is ensured by assembly, the positioning between the middle column and the outer ring is ensured by assembly on the lower end face of the middle column, and the positioning between the outer ring and the base is ensured by assembly on the annular groove 4 structure on the lower end face of the outer ring. In addition, there are two square groove structures with a size of 103*30*10mm on the outside of the outer ring part of the annular riser wax mold, which facilitates the assembly and positioning of the outer ring and the base of the annular riser wax mold. The schematic diagram of the structure of the 3D model of the sprue wax mold that was finally established is shown in Figure 3 As shown, it is an integral structure with two Φ20mm water cooling holes set on the upper end surface.

[0033] The 3D models of the annular riser wax mold and the sprue wax mold are processed. First, the 3D models of the annular riser wax mold and the sprue wax mold in prt format are exported to stl format. The stl dimensional models are checked and repaired for model errors, the bottom support structure and internal support structure of the annular riser wax mold and the sprue wax mold are determined, the tilted printing angle is set, the slicing parameters are set, and finally a CLI layer format file that can be used for stereolithography is generated.

[0034] Add bottom supports to the center column of the annular riser wax mold with a bottom support height of 9-10mm. Then add the internal support structure. The internal support structure is a honeycomb structure. Set the tilt printing angle to 30°. Finally, set the 3D model slicing parameters in the Z-axis direction of the 3D model with bottom supports, and set the slicing parameters to 0.1mm, and finally form a CLI layer format file that can be used for stereolithography. Add bottom supports to the outer ring and base of the annular riser wax mold with a bottom support height of 9-10mm. Then add the internal support structure, which is a honeycomb structure. Set the tilt printing angle to 15-20°. Set the slicing parameters to 0.1mm, and finally form a CLI layer format file that can be used for stereolithography. The CLI layer format files of the three parts of the sprue wax mold, including the center column, outer ring, and base, of the annular riser wax mold were imported into the stereolithography machine. The printing models were arranged according to the spatial dimensions of the stereolithography machine and then printed in sequence. The material used in the printing process was C-UV9400A photosensitive resin.

[0035] After the ring riser wax mold and the sprue wax mold are printed, use a scraper to scrape them off the bottom support, and then use scissors or other tools to remove the inner cavity support structure. After the inner cavity support structure is removed, use alcohol to scrub it to remove the residual photosensitive resin on the surface and inside. Then use an air gun to blow off the residual alcohol and photosensitive resin on the surface of the ring riser wax mold and the sprue wax mold. Finally, place the ring riser wax mold and the sprue wax mold in a secondary curing box for secondary curing by ultraviolet light. The secondary curing time is 20-40 minutes. After the secondary curing is completed, use 150-400 mesh fine sandpaper to smooth the remaining support residue and printing texture on the surface of the ring riser wax mold and the sprue wax mold.

[0036] The examples described above are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A design and processing method for a wax mold of a pouring and riser system based on photocuring, characterized in that: include: Based on the casting process construction drawings of the closed impeller structure casting, a 3D wax model of the annular riser and a 3D wax model of the sprue were constructed; Based on the rotary structure characteristics of the annular riser wax mold and the sprue wax mold, the 3D models of the annular riser wax mold and the sprue wax mold corresponding to the 3D models of the annular riser wax mold and the sprue wax mold are designed and constructed; Setting the structural parameters of the 3D models of the annular riser wax mold and the sprue wax mold, i.e., determining the bottom support structure, determining the internal support structure, setting the tilted printing angle, and setting the 3D model slicing parameters, ultimately forming a model that can be used for printing; The model is imported into the stereolithography machine, and the model is arranged and printed according to the spatial dimensions of the stereolithography machine.

2. A method for designing and processing a wax mold for a pouring and riser system based on stereolithography according to claim 1, characterized in that: The annular riser wax mold is a split structure, assembled from a center column, an outer ring, and a base. The three parts are assembled to ensure spatial positioning. The center column and the outer ring are assembled on the lower end face of the center column to ensure positioning, and the outer ring and the base are assembled on the lower end face of the outer ring to ensure positioning.

3. A method for designing and processing a wax mold for a pouring and riser system based on stereolithography according to claim 1, characterized in that: The straight runner wax mold is an integral structure with two water injection cooling holes on the upper end surface, which also serve as discharge holes for the residual photosensitive resin in the inner cavity of the photosensitive resin mold, and are used to pour out the residual resin in the mold cavity after the photosensitive resin mold is printed.

4. A method for designing and processing a wax mold for a pouring and riser system based on stereolithography according to claim 2, characterized in that: The center column is set to have an inclined printing angle of 30°, the outer ring is set to have an inclined printing angle of 15-20°, and the base is not set to have an inclined printing angle.

5. The method for designing and processing a wax mold for a pouring and riser system based on stereolithography according to claim 2, characterized in that: The bottom support heights of the central column, outer ring, and base are all 9-10 mm, and the internal support structure is a honeycomb structure.

6. A method for designing and processing a wax mold for a pouring and riser system based on stereolithography according to claim 3, characterized in that: The bottom support height of the sprue wax mold 3D model is 9-10mm, the internal support structure is a honeycomb structure, and no tilt printing angle is set.

7. The method for designing and processing a wax mold for a pouring and riser system based on stereolithography according to claim 1, characterized in that: The printing material used is C-UV9400A photosensitive resin, and the printing layer thickness is 0.1mm.

8. A method for designing and processing a wax mold for a pouring and riser system based on stereolithography according to any one of claims 1 to 7, characterized in that: After printing, the surfaces of the annular riser wax mold and the sprue wax mold are cleaned of residual photosensitive resin, support removed, secondary cured, and surface polished.

9. A method for designing and processing a wax mold for a pouring and riser system based on stereolithography according to claim 8, characterized in that: The secondary curing time is 20-40 minutes; when the secondary curing is completed and the polishing operation is performed, fine sandpaper with a mesh size of 150-400 mesh is used.

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