A method for forming a sand core mold with a large aspect ratio
By using quartz sand and hollow glass microspheres as fillers, combined with the design of metal parts, the structure of the large aspect ratio sand core mold was optimized, solving the problems of lightweight and high strength. This achieved both lightweighting and strength improvement of the core mold, making it suitable for the production of shells with large aspect ratios.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUBEI SANJIANG HANGTIAN JIANGBEI MASCH ENG CO LTD
- Filing Date
- 2022-10-28
- Publication Date
- 2026-05-26
AI Technical Summary
Existing technologies make it difficult to manufacture lightweight, high-strength sand core molds with large aspect ratios, which leads to problems such as deflection deformation, cracking of splice seams, and unstable winding tension during the use of the core molds.
Quartz sand and hollow glass microspheres are used as fillers. Lightweight sand cakes are formed by curing polyvinyl alcohol solution. Combined with the design of metal parts, the core mold structure is optimized to ensure strength and lightweight.
It achieves lightweighting and strength improvement of sand core molds with large aspect ratios, avoids mandrel deflection and core mold surface fracture, and is suitable for the production of shells with large aspect ratios.
Smart Images
Figure CN115674653B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of sand core winding mold materials, specifically relating to a method for forming a sand core mold with a large aspect ratio. Background Technology
[0002] Due to its advantages such as high strength, water solubility, and ease of processing, sand core molds are widely used as core molds for small-opening winding shells. It is made by mixing polyvinyl alcohol solution and inorganic materials in a certain proportion and solidifying them. The sand cake is assembled for winding shells. After solidification, the shell is demolded by water solubility. It has the advantages of fast assembly time and convenient demolding. Polyvinyl alcohol solution and quartz sand are widely used as raw materials to make water-soluble sand core molds at home and abroad (Wang Xinling, Fu Chenglong, Li Cailin, Xie Jimin, Research on the performance of high temperature resistant water-soluble sand core molds for polymer-based composite materials [J], Plastics Industry, 2019, 47(4), 105-109). Currently, most studies focus on the properties of raw materials for sand core molds, with few studies specifically on the structure of the sand core mold itself. Ma Juan et al. (Chinese patent "Lightweight Structure Sand Core Mold Forming Method", CN112405959A) designed a lightweight sand core mold by designing a sand cake to reduce weight, but their design resulted in a small core mold size and short length, and the shell opening size was not considered. The core mold strength issue was not further demonstrated, making it difficult to adapt to shells with large length-to-diameter ratios.
[0003] Due to the large size of the high aspect ratio sand core mold, if existing sand cake raw materials and weight-reduction designs are used, the large weight of the core mold will lead to significant mandrel deflection and deformation, resulting in cracking of the sand cake joints or the sand cake itself, causing defects in the internal insulation of the shell, and also leading to unstable winding tension. Zhuo Aibao et al. (Chinese patent "A method for forming a lightweight high-strength sand core mold", CN112872298A) produced a lightweight high-strength sand core mold by adding short-cut glass fibers to the core sand, but the patent did not clearly explain the density before and after modification. Theoretically, the short-cut fibers have a small volume and can fill the gaps in the core sand, so the weight reduction is not significant. Therefore, it is necessary to find a lighter core mold material and optimize the core mold design to meet the requirements of using high aspect ratio sand core molds for winding shells. Summary of the Invention
[0004] In view of the problems existing in the background technology, the purpose of this invention is to provide a large aspect ratio sand core mold forming method that ensures lighter weight and lower cost while maintaining the same strength.
[0005] To achieve the above objectives, the present invention provides a method for forming a large aspect ratio sand core mold, comprising the following steps:
[0006] S1, Tooling Design: Determine the outer diameter and shortest length of the mandrel based on the product dimensions and the support position of the winding machine; Design the segment size of the sand cake based on the outer diameter and length of the mandrel.
[0007] S2, Machining: Machining metal parts according to design drawings; the metal parts include mandrels, bushings, etc.
[0008] S3, Sand cake production: Using quartz sand and hollow glass microspheres in a certain proportion as fillers, polyvinyl alcohol water-soluble lightweight sand cakes are prepared.
[0009] S4, Core Mold Assembly: The sand cakes are machined to the required dimensions and then installed one by one onto the core shaft in a vertical manner;
[0010] S5, Core mold machining: Machining the outer core surface of the core mold according to the inner shape of the product.
[0011] Preferably, in step S1, the mandrel is solid, and the outer diameter of the mandrel is close to the opening size of the product, and the shortest length meets the support and clamping requirements of the winding machine.
[0012] More preferably, the outer diameter of the front and rear ends of the mandrel is close to the opening size, and after passing the front opening, it becomes the outer diameter of the mandrel that is close to the size of the rear opening.
[0013] More preferably, the mandrel and the housing have a clamping length of not less than 700 mm between their adjacent end faces, and the mandrel has holes on its front and rear end faces for hoisting and extension.
[0014] Preferably, in step S1, the sand cake includes a front section, a rear section, and multiple cylindrical sections located between the front and rear sections; the number of cylindrical sections is odd, and the height of the cylindrical sand cake is 300-500mm.
[0015] Preferably, in step S3, the steps for making the sand cake include:
[0016] S301, Mold release agent application: Apply a layer of room temperature vulcanizing silicone rubber mold release agent evenly to the inner surface of the sand core mold forming tool, and cure at room temperature for more than 24 hours.
[0017] S302, Polyvinyl alcohol solution preparation: Weigh out water at a mass ratio of 3 to 5:1, pour it into a stainless steel container, and stir it evenly in a 100°C water bath until the polyvinyl alcohol is completely dissolved. Then cool it to room temperature and store it for later use.
[0018] S303, Mortar Mixing: Dry quartz sand and hollow glass microspheres are mixed with the polyvinyl alcohol solution prepared in S302 at a mass ratio of 7-9:4-6:1 into a mechanical sand mixer and mixed evenly.
[0019] S304, filling and curing: Pour the mixed mortar prepared in S303 into the sand core mold forming tooling. It is required to pour in batches and compact them pneumatically in batches. Finally, fill it to the open end face of the forming tooling. Then put it in the oven and heat it to 140°C at room temperature for 20 hours to cure. Then cool it to room temperature with the oven.
[0020] S305, Demolding and Machining: The cooled sand core mold is removed from the sand core mold forming fixture and then machined into a sand cake.
[0021] In a further preferred embodiment, in step S303, 50-80 mesh quartz sand is selected.
[0022] For further optimization, hollow glass microspheres of 0.4–0.6 mm are selected.
[0023] Compared with the prior art, the present invention has the following main advantages:
[0024] The large aspect ratio sand core mold produced by this invention has the characteristics of high strength, lightweight and simple manufacturing process, avoiding the risk of core mold surface breakage caused by mandrel deflection deformation, and is suitable for the production of large aspect ratio shells. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the large aspect ratio sand core mold structure of the present invention. Detailed Implementation
[0026] The technical solutions (including preferred technical solutions) of the present invention will be further described in detail below with reference to the accompanying drawings and by way of listing some optional embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0027] The large aspect ratio sand core mold forming method designed in this invention includes the following steps:
[0028] S1, Tooling Design: Determine the outer diameter and shortest length of the mandrel based on the product dimensions and the support position of the winding machine; Design the segment size of the sand cake based on the outer diameter and length of the mandrel.
[0029] S2, Machining: Machining metal parts according to design drawings;
[0030] S3, Sand cake production: Water-soluble quartz sand and hollow glass microspheres are used as fillers in a certain proportion to prepare polyvinyl alcohol water-soluble sand cakes and lightweight sand cakes.
[0031] S4, Core mold assembly: The sand cake is machined to the required size and the flat end face sand cake is installed vertically;
[0032] S5, Core mold machining: Machining the outer core surface of the core mold according to the inner shape of the product.
[0033] The steps for making sand cakes include:
[0034] S301, Mold release agent application: Apply a layer of room temperature vulcanizing silicone rubber mold release agent evenly to the inner surface of the sand core mold forming tool, and cure at room temperature for more than 24 hours.
[0035] S302, Polyvinyl alcohol solution preparation: Weigh out water and polyvinyl alcohol at a mass ratio of 4:1, pour into a stainless steel container, and stir evenly in a 100℃ water bath until the polyvinyl alcohol is completely dissolved. Then cool to room temperature and store for later use.
[0036] S303, Mortar Mixing: Dry quartz sand and hollow glass microspheres are mixed with the polyvinyl alcohol solution prepared in S302 at a mass ratio of 7-9:4-6:1 into a mechanical sand mixer and mixed evenly.
[0037] S304, Filling and Curing: Pour the mixed mortar prepared in S303 into the sand core mold forming fixture. It is required to pour in batches and compact them pneumatically in batches. Finally, fill it to the open end face of the forming fixture, and then put it into the oven for curing at room temperature → 140℃ / 20h. That is, after raising the temperature from room temperature to 140℃, keep it at that temperature for 20h, and then cool it to room temperature with the oven.
[0038] S305, Demolding and Machining: The cooled sand core mold is removed from the sand core mold forming fixture, and then the whole material is machined into a sand cake.
[0039] In short, the present invention provides a method for forming a sand core mold with a large aspect ratio, comprising the following steps: (1) Tooling design: designing the diameter and length of the solid core shaft according to the size of the product opening and the self-weight of the core mold; (2) Machining: machining a set of metal parts according to the design drawings; (3) Sand cake making: preparing polyvinyl alcohol water-soluble sand cake using water-soluble quartz sand / hollow glass microspheres as filler; (4) Core mold assembly: installing the flat end face sand cake in a vertical manner; (5) Core mold machining: machining the outer core surface of the core mold according to the inner shape of the product.
[0040] To achieve better results, multiple tests can be conducted on the molding material:
[0041] Sample Example 1:
[0042] A high aspect ratio sand core mold molding material is obtained by the following method:
[0043] (1) Applying release agent: Apply a layer of room temperature vulcanizing silicone rubber release agent evenly to the inner surface of the sand core mold forming tool and cure at room temperature for more than 24 hours;
[0044] (2) Preparation of polyvinyl alcohol solution: Weigh out tap water and polyvinyl alcohol in a mass ratio of 4:1 and pour it into a stainless steel bucket. Stir mechanically in a 100°C water bath until the polyvinyl alcohol is completely dissolved. Then cool to room temperature and store for later use.
[0045] (3) Mortar mixing: Dry 50-80 mesh quartz sand and 0.4-0.6 mm hollow glass microspheres are poured into a mechanical sand mixer at a mass ratio of 8:5:1 with the above polyvinyl alcohol, and mixed evenly for 20 minutes.
[0046] (4) Filling and curing: Pour the above-mentioned mixed mortar into the above-mentioned sand core mold forming tooling. It is required to pour in batches and compact the mortar pneumatically in batches. Finally, fill the molding tooling to the open end face, and then put it into the oven and cure it at room temperature → 140℃ / 20h. Then cool it to room temperature with the oven.
[0047] (5) Demolding and machining: Remove the cooled sand core mold from the sand core mold forming tooling, and then machine the whole material into a compression sample. The sample size is 40mm×40mm×62mm, and the quantity is 5.
[0048] Its average compressive strength at room temperature was measured to be 21.9 MPa, its average compressive strength at 150℃ was 10.5 MPa, and its average density was 1.41 g / cm³. 3 The dissolution time in room temperature water is 5 minutes.
[0049] Sample Example 2:
[0050] A high aspect ratio sand core mold molding material is obtained by the following method:
[0051] (1) Applying release agent: Apply a layer of room temperature vulcanizing silicone rubber release agent evenly to the inner surface of the sand core mold forming tool and cure at room temperature for more than 24 hours;
[0052] (2) Preparation of polyvinyl alcohol solution: Weigh out tap water and polyvinyl alcohol in a mass ratio of 4:1 and pour into a stainless steel bucket. Stir mechanically in a 100°C water bath until the polyvinyl alcohol is completely dissolved. Then cool to room temperature and store for later use.
[0053] (3) Mortar mixing: Dry 50-80 mesh quartz sand and 0.4-0.6 mm hollow glass microspheres are poured into a mechanical sand mixer at a mass ratio of 7:4:1 with the above polyvinyl alcohol, and mixed evenly for 20 minutes.
[0054] (4) Filling and curing: Pour the above-mentioned mixed mortar into the above-mentioned sand core mold forming tooling. It is required to pour in batches and compact the mortar pneumatically in batches. Finally, fill the molding tooling to the open end face, and then put it into the oven and cure it at room temperature → 140℃ / 20h. Then cool it to room temperature with the oven.
[0055] (5) Demolding and machining: Remove the cooled sand core mold from the sand core mold forming tooling, and then machine the whole material into a compression sample. The sample size is 40mm×40mm×62mm, and the quantity is 5.
[0056] Its average compressive strength at room temperature was measured to be 22.1 MPa, its average compressive strength at 150℃ was 11.8 MPa, and its average density was 1.55 g / cm³. 3 The dissolution time in room temperature water is 7 minutes.
[0057] Sample Example 3:
[0058] A high aspect ratio sand core mold molding material is obtained by the following method:
[0059] (1) Applying release agent: Apply a layer of room temperature vulcanizing silicone rubber release agent evenly to the inner surface of the sand core mold forming tool and cure at room temperature for more than 24 hours;
[0060] (2) Preparation of polyvinyl alcohol solution: Weigh out tap water and polyvinyl alcohol in a mass ratio of 4:1 and pour into a stainless steel bucket. Stir mechanically in a 100°C water bath until the polyvinyl alcohol is completely dissolved. Then cool to room temperature and store for later use.
[0061] (3) Mortar mixing: Dry 50-80 mesh quartz sand and 0.4-0.6 mm hollow glass microspheres are poured into a mechanical sand mixer at a mass ratio of 7:6:1 with the above polyvinyl alcohol, and mixed evenly for 20 minutes.
[0062] (4) Filling and curing: Pour the above-mentioned mixed mortar into the above-mentioned sand core mold forming tooling. It is required to pour in batches and compact the mortar pneumatically in batches. Finally, fill the molding tooling to the open end face, and then put it into the oven and cure it at room temperature → 140℃ / 20h. Then cool it to room temperature with the oven.
[0063] (5) Demolding and machining: Remove the cooled sand core mold from the sand core mold forming tooling, and then machine the whole material into a compression sample. The sample size is 40mm×40mm×62mm, and the quantity is 5.
[0064] Its average compressive strength at room temperature was measured to be 17.2 MPa, its average compressive strength at 150℃ was 7.5 MPa, and its average density was 1.34 g / cm³. 3 The dissolution time in room temperature water is 5 minutes.
[0065] Sample Example 4:
[0066] A high aspect ratio sand core mold molding material is obtained by the following method:
[0067] (1) Applying release agent: Apply a layer of room temperature vulcanizing silicone rubber release agent evenly to the inner surface of the sand core mold forming tool and cure at room temperature for more than 24 hours;
[0068] (2) Preparation of polyvinyl alcohol solution: Weigh out tap water and polyvinyl alcohol in a mass ratio of 4:1 and pour into a stainless steel bucket. Stir mechanically in a 100°C water bath until the polyvinyl alcohol is completely dissolved. Then cool to room temperature and store for later use.
[0069] (3) Mortar mixing: Dry 50-80 mesh quartz sand and 0.4-0.6 mm hollow glass microspheres are poured into a mechanical sand mixer at a mass ratio of 8:4:1 with the above polyvinyl alcohol, and mixed evenly for 20 minutes.
[0070] (4) Filling and curing: Pour the above-mentioned mixed mortar into the above-mentioned sand core mold forming tooling. It is required to pour in batches and compact the mortar pneumatically in batches. Finally, fill the molding tooling to the open end face, and then put it into the oven and cure it at room temperature → 140℃ / 20h. Then cool it to room temperature with the oven.
[0071] (5) Demolding and machining: Remove the cooled sand core mold from the sand core mold forming tooling, and then machine the whole material into a compression sample. The sample size is 40mm×40mm×62mm, and the quantity is 5.
[0072] Its average compressive strength at room temperature was measured to be 21.5 MPa, its average compressive strength at 150℃ was 10.9 MPa, and its average density was 1.51 g / cm³. 3 The dissolution time in room temperature water is 5 minutes.
[0073] Sample Example 5:
[0074] A high aspect ratio sand core mold molding material is obtained by the following method:
[0075] (1) Applying release agent: Apply a layer of room temperature vulcanizing silicone rubber release agent evenly to the inner surface of the sand core mold forming tool and cure at room temperature for more than 24 hours;
[0076] (2) Preparation of polyvinyl alcohol solution: Weigh out tap water and polyvinyl alcohol in a mass ratio of 4:1 and pour into a stainless steel bucket. Stir mechanically in a 100°C water bath until the polyvinyl alcohol is completely dissolved. Then cool to room temperature and store for later use.
[0077] (3) Mortar mixing: Dry 50-80 mesh quartz sand and 0.4-0.6 mm hollow glass microspheres are poured into a mechanical sand mixer at a mass ratio of 8:6:1 with the above polyvinyl alcohol, and mixed evenly for 20 minutes.
[0078] (4) Filling and curing: Pour the above-mentioned mixed mortar into the above-mentioned sand core mold forming tooling. It is required to pour in batches and compact the mortar pneumatically in batches. Finally, fill the molding tooling to the open end face, and then put it into the oven and cure it at room temperature → 140℃ / 20h. Then cool it to room temperature with the oven.
[0079] (5) Demolding and machining: Remove the cooled sand core mold from the sand core mold forming tooling, and then machine the whole material into a compression sample. The sample size is 40mm×40mm×62mm, and the quantity is 5.
[0080] Its average compressive strength at room temperature was measured to be 18.1 MPa, its average compressive strength at 150℃ was 9.4 MPa, and its average density was 1.38 g / cm³. 3 The dissolution time in room temperature water is 5 minutes.
[0081] Comparative Examples of Samples:
[0082] A high aspect ratio sand core mold molding material is obtained by the following method:
[0083] (1) Applying release agent: Apply a layer of room temperature vulcanizing silicone rubber release agent evenly to the inner surface of the sand core mold forming tool and cure at room temperature for more than 24 hours;
[0084] (2) Preparation of polyvinyl alcohol solution: Weigh out tap water and polyvinyl alcohol in a mass ratio of 4:1 and pour into a stainless steel bucket. Stir mechanically in a 100°C water bath until the polyvinyl alcohol is completely dissolved. Then cool to room temperature and store for later use.
[0085] (3) Mortar mixing: Pour the dry 50-80 mesh quartz sand and the above polyvinyl alcohol into a mechanical sand mixer at a mass ratio of 13:1, mix evenly, and stir for 20 minutes.
[0086] (4) Filling and curing: Pour the above-mentioned mixed mortar into the above-mentioned sand core mold forming tooling. It is required to pour in batches and compact the mortar pneumatically in batches. Finally, fill the molding tooling to the open end face, and then put it into the oven and cure it at room temperature → 140℃ / 20h. Then cool it to room temperature with the oven.
[0087] (5) Demolding and machining: Remove the cooled sand core mold from the sand core mold forming tooling, and then machine the whole material into a compression sample. The sample size is 40mm×40mm×62mm, and the quantity is 5.
[0088] Its average compressive strength at room temperature was measured to be 23.9 MPa, its average compressive strength at 150℃ was 11.2 MPa, and its average density was 1.78 g / cm³. 3 The dissolution time in room temperature water is 5 minutes.
[0089] Example of a high aspect ratio sand core mold forming method:
[0090] S1, Tooling Design: Based on the product dimensions and the support position of the winding machine, the outer diameter of the front thin shaft part of the solid mandrel is determined to be φ166mm, the outer diameter of the rear mandrel is φ285mm, the total length is 5120mm, the length of the front and rear clamping positions is 700mm, the sand cake segment size is designed to be 500mm, and M75 threaded holes are reserved on the front and rear end faces for mandrel hoisting and extended use;
[0091] S2, Machining: Machining a set of 30CrMnSi metal parts according to the design drawings.
[0092] S3, Sand cake preparation: Water-soluble quartz sand / hollow glass microspheres were used as filler in Example 1 of the sample to prepare lightweight polyvinyl alcohol water-soluble sand cake.
[0093] S4, Core mold assembly: Machin the sand cake to the required height and install the flat end face sand cake vertically. After installation, flip the sand cake to the horizontal position and then turn it to the machining position.
[0094] S5, Core mold machining: Machining is performed on the outer core surface of the core mold according to the inner shape of the product.
[0095] It will be readily understood by those skilled in the art that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, combinations, substitutions, improvements, etc., made under the spirit and principles of the present invention are included within the protection scope of the present invention.
Claims
1. A method for forming a sand core mold with a large aspect ratio, characterized in that, Includes the following steps: S1, Tooling Design: Determine the outer diameter and shortest length of the mandrel based on the product dimensions and the support position of the winding machine. Design the sand cake segment dimensions based on the outer diameter and length of the mandrel. The mandrel is solid, and its outer diameter is close to the product opening size. The shortest length meets the support and clamping requirements of the winding machine. S2, Machining: Machining metal parts according to design drawings; S3, Sand cake production: Using quartz sand and hollow glass microspheres in a certain proportion as fillers, polyvinyl alcohol water-soluble lightweight sand cakes are prepared. S4, Core Mold Assembly: Machine the sand cakes to the required dimensions, and install them one by one onto the mandrel in a vertical manner. After installation, flip the sand cakes to a horizontal position and then turn them to the machining center. S5, Core mold machining: Machining the outer core surface of the core mold according to the inner shape of the product.
2. The method for forming a large aspect ratio sand core mold according to claim 1, characterized in that: The outer diameter of the front and rear ends of the mandrel is close to the size of the opening, and after passing the front opening, it becomes the outer diameter of the mandrel that is close to the size of the rear opening.
3. The method for forming a large aspect ratio sand core mold according to claim 1, characterized in that: The mandrel and the housing have a clamping length of not less than 700 mm between their adjacent end faces, and holes for mandrel hoisting and extension are provided on the front and rear end faces of the mandrel.
4. The method for forming a large aspect ratio sand core mold according to claim 1, characterized in that: In step S1, the sand cake includes a front section, a rear section, and multiple cylindrical sections located between the front and rear sections; the number of cylindrical sections is odd, and the height of the cylindrical sand cake is guaranteed to be 300-500mm.
5. The method for forming a large aspect ratio sand core mold according to claim 1, characterized in that: In step S3, the steps for making the sand cake include: S301, Mold release agent application: Apply a layer of room temperature vulcanizing silicone rubber mold release agent evenly to the inner surface of the sand core mold forming tool, and cure at room temperature for more than 24 hours. S302, Polyvinyl alcohol solution preparation: Weigh out water at a mass ratio of 3 to 5:1, pour it into a stainless steel container, and stir it evenly in a 100°C water bath until the polyvinyl alcohol is completely dissolved. Then cool it to room temperature and store it for later use. S303, Mortar Mixing: Dry quartz sand and hollow glass microspheres are mixed with the polyvinyl alcohol solution prepared in S302 at a mass ratio of 7-9:4-6:1 into a mechanical sand mixer and mixed evenly. S304, filling and curing: Pour the mixed mortar prepared in S303 into the sand core mold forming tooling. It is required to pour in batches and compact them pneumatically in batches. Finally, fill it to the open end face of the forming tooling. Then put it in the oven and heat it to 140°C at room temperature for 20 hours to cure. Then cool it to room temperature with the oven. S305, Demolding and Machining: The cooled sand core mold is removed from the sand core mold forming fixture and then machined into a sand cake.
6. The method for forming a large aspect ratio sand core mold according to claim 5, characterized in that: In step S303, 50-80 mesh quartz sand is selected.
7. The method for forming a large aspect ratio sand core mold according to claim 5, characterized in that: In step S303, hollow glass microspheres of 0.4-0.6 mm are selected.