A combined mold design method for multi-cavity thin-walled castings

Abstract

This invention relates to a method for designing a combined mold for multi-cavity thin-walled castings, belonging to the field of sand casting technology. It solves the problems of existing traditional casting techniques, such as the large number of sand cores, difficulty in positioning, and easy deformation leading to insufficient dimensional accuracy and poor casting quality. The invention provides a method for designing a combined mold for multi-cavity thin-walled castings, comprising the following steps: S1: Determining the preset number of risers and the number of sand mold partings; S2: Designing the sand mold partings according to the number of risers and the modulus, with each sand mold parting containing a "double-row comb-type" venting unit; S3: Designing a wooden main mold based on the overall shape of the sand mold. The combined mold designed by this method significantly reduces the number of partings compared to traditional sand cores, thereby simplifying operation, ensuring accurate positioning, reducing errors, improving venting performance, reducing porosity in the casting, and achieving high precision in the inner surface of the sand mold, resulting in accurate casting dimensions and good surface quality.

Description

Technical Field

[0001] This invention relates to the field of casting sand mold technology, and in particular to a method for designing a combined mold for multi-cavity thin-walled castings. Background Technology

[0002] The forecastle is one of the most important components of a ship. Located at the very front of the hull, it is the first part to be impacted by water, bearing the force of water pressure, wave impact, and external collisions. Therefore, it has strict requirements for structure, strength, shape, and lifespan. Cast steel forecastles are generally slender, variable-section rod-like components, typically reaching about 7 meters in length, with some large ships even reaching 21 meters. They often exhibit a "C"-shaped structure or a "V"-shaped cross-section. Based on manufacturing methods, they can be classified into forged steel forecastles, cast steel forecastles, plate steel forecastles, and hybrid forecastles. Among these, cast steel forecastles are widely used due to their ability to be manufactured into more complex cross-sectional shapes and bending configurations.

[0003] Cast steel bows are a typical type of multi-cavity thin-walled casting. Currently, the casting method for similar castings is as follows: first, a partial model and a core box are made of wood; then, the model is hammered in a sand pit; then, according to the core-laying sequence, the cores are placed in the core box and hammered to obtain sand cores; finally, the cores are assembled in a sand box or pit to form the cavity of the cast steel bow / multi-cavity thin-walled casting.

[0004] Existing casting technology has the following drawbacks: Firstly, as ship sizes increase, the length of the cast steel bow increases, requiring more sand cores and extending the production cycle. Furthermore, the use of wooden molds increases costs, intensifies labor intensity for workers, and causes environmental pollution. Secondly, the positioning of the core box during compaction is difficult to control, resulting in large gaps between cores and easy deformation, which severely affects the dimensional accuracy of the cast steel bow. In addition, existing general-purpose venting systems for casting sand molds are relatively simple, leading to poor venting during the pouring of multi-cavity thin-walled castings, easily causing defects such as porosity in the castings. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a combined mold design method for multi-cavity thin-walled castings, in order to solve at least one of the following problems in the prior art: excessive sand mold components / sand cores in casting multi-cavity thin-walled castings, resulting in difficulty in controlling the positioning of the core box during the compaction process, large core gaps, easy deformation affecting the dimensional accuracy of the casting, and poor venting effect during the casting pouring process.

[0006] This invention provides a method for designing a combined mold for multi-cavity thin-walled castings. The combined mold includes a 3D-printed sand mold and a wooden master mold, and includes the following steps:

[0007] S1: Based on the size and shape of the multi-cavity thin-walled casting and the hot spots during the casting process, determine the number of preset risers 1 and the number of sand molds; the sand mold is divided into upper and lower layers, and each layer of sand mold consists of several molds;

[0008] S2: The sand mold is designed according to the number of risers 1 and the module. Each sand mold is equipped with a "double-row comb-type" venting unit inside the mold.

[0009] S3: Design a wooden master mold according to the overall shape of the sand mold. The wooden master mold is used to pre-shape grooves in the sand box for setting the sand mold.

[0010] Specifically, the design principle for the number of risers 1 in step S1 is to set one riser 1 at each end along the length of the multi-cavity thin-walled casting, and the number of risers 1 in the middle position needs to meet the continuity of 45-55%; the cross-sectional shape of the riser 1 is one of ellipse, square, rectangle or irregular polygon; the riser 1 is also provided with reinforcing ribs 7.

[0011] Specifically, the number of risers 1, the size and shape of the multi-cavity thin-walled casting, and the strength of the printing material used are determined to determine the number of sand molds to be separated in each layer; the number of risers 1 contained in a single sand mold separation shall not exceed 3, and the length-to-width ratio shall not exceed 2.

[0012] Specifically, the "double-row comb-type" exhaust unit includes an air collection channel 2, an air guide channel 3, and an exhaust channel 4;

[0013] The air guide channel 3 is set according to the shape of the inner cavity of the sand mold;

[0014] One end of the air collecting channel 2 is connected to the air guiding channel 3, and the other end points to the inner cavity and maintains a certain distance from the surface of the inner cavity.

[0015] One end of the exhaust duct 4 is connected to the air guide duct 3, and the other end points to the outer surface of the sand mold and is open to the atmosphere;

[0016] The interconnected air collection channel 2, air guide channel 3 and exhaust channel 4 constitute a complete "double-row comb-type" exhaust unit; at least one "double-row comb-type" exhaust unit is provided in a single sand mold.

[0017] Specifically, the total cross-sectional area of ​​the air collection channel 2 in each "double-row comb-type" exhaust unit is S1, the total cross-sectional area of ​​the air guide channel 3 is S2, and the total cross-sectional area of ​​the exhaust channel 4 is S3, with S1:S2:S3 = (1.25~2.5):1:(2.0~3.0).

[0018] Specifically, the end of the air collection channel 2 closest to the cavity is 150-250 mm away from the surface of the inner cavity.

[0019] Preferably, the sand mold parting also includes a chill reserved cavity 5 and a fixing through hole 6; the chill reserved cavity 5 is located on the inner cavity surface between adjacent risers 1, and the chill reserved cavity 5 is connected to the outer surface of the sand mold parting through the fixing through hole 6.

[0020] Specifically, the shape of the wooden main mold is the same as the lower half of the overall sand mold in the assembled state; the height of the wooden main mold is 1 / 5 to 1 / 3 of the height of the overall sand mold.

[0021] The present invention also discloses a combined mold, which includes a 3D printed sand mold and a wooden master mold designed by the design method.

[0022] The present invention also discloses a casting method for a multi-cavity thin-walled casting, characterized in that the casting method uses the aforementioned combined mold, and the multi-cavity thin-walled casting is obtained after molding, pouring, and demolding.

[0023] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0024] 1. This invention creatively adopts a combination of "wooden master mold + 3D printed sand mold" for casting multi-cavity thin-walled castings, especially large castings (cast steel bows). This significantly reduces the number of sand cores, lowers the difficulty of operation and improves the efficiency of operation, while greatly improving the positioning accuracy and the surface quality inside the cavity, thereby improving the accuracy and surface quality of the castings.

[0025] Current 3D printing technology is mainly used for the rapid manufacturing of small to medium-sized complex castings. In general, sand casting is primarily used for small castings such as engine blocks, and medium-sized castings such as mixed-flow turbines weighing over 2 tons. Its application in large cast steel parts is relatively limited. Cast steel bows are characterized by numerous cavities, long lengths, and thin walls. If sand molds were entirely manufactured using 3D printing, the sand cores forming the outer surface of the bow would also need to be printed, resulting in long production times and high costs. Current technology combines traditional wooden master molds with sand core boxes, where each cavity is formed by a separate sand core. This leads to a large number of sand cores and a long core-making time.

[0026] This invention uses 3D printed sand molds to form complex areas of cast steel bows, while the main mold is made using traditional wooden molds. The combination of these two methods can significantly improve the molding efficiency of cast steel bows and greatly enhance positioning accuracy and casting quality.

[0027] 2. The 3D printing sand mold parting system designed in this invention features a "double-row comb-type" exhaust system (composed of multiple exhaust units), resulting in excellent exhaust performance. Based on the characteristics of cast steel bow columns, such as multiple cavities, long lengths, and thin walls, this invention creatively designs a "double-row comb-type" exhaust unit / system consisting of a gas collecting channel, a gas guiding channel, and an exhaust channel. One end of the gas collecting channel is close to the inner cavity, efficiently collecting gases generated during the casting and setting process. After being collected, the exhaust gas enters the gas guiding channel, which is integrated into the mold, and is finally discharged into the external atmosphere through the exhaust channel. The exhaust efficiency of this system is significantly improved compared to existing general-purpose exhaust systems, reducing or even eliminating the generation of porosity defects in the casting.

[0028] Furthermore, when the cross-sectional area relationship between the gas collecting channel, the gas guiding channel, and the exhaust channel satisfies S1:S2:S3=(1.25~2.5):1:(2.0~3.0), the exhaust effect is better, which can avoid gas congestion and poor exhaust when a large amount of gas is discharged.

[0029] 3. The 3D printing sand mold designed in this invention also has a reserved cavity for chills and a through hole for fixing. In actual implementation, the chills can be connected to the reinforcing bars by spot welding and fixed in the preset position of the inner cavity through the through hole. In this way, it can accelerate the solidification speed of the casting, refine the grain structure, and improve the mechanical properties of the casting during the pouring process. The chill fixing method is simple and easy to implement, the fixing is firm and the heat conduction effect is good.

[0030] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0031] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0032] Figure 1 A schematic diagram of the cast steel bow column structure;

[0033] Figure 2 The sand core parting process diagrams for cast steel bow castings in the existing technology (a total of 34 pieces);

[0034] Figure 3 This is a schematic diagram of a single exhaust unit structure;

[0035] Figure 4 This is the parting line design drawing for the 3D printed sand mold in Example 1;

[0036] Figure 5 This is an enlarged view (perspective rendering) of parting line a in the 3D printing sand mold parting line of Example 1;

[0037] Figure 6 This is an enlarged view (perspective line drawing) of parting line a in the 3D printing sand mold parting line of Example 1;

[0038] Figure 7 This is a schematic diagram of a 3D printed sand mold and a wooden main structure.

[0039] Figure label:

[0040] 1. Riser; 2. Gas collecting channel; 3. Gas guiding channel; 4. Gas exhaust channel; 5. Chip reserved cavity; 6. Through hole for fixing; 7. Reinforcing rib plate. Detailed Implementation

[0041] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0042] The following problems exist in the casting process of existing cast steel bow pillar castings (a type of large, multi-cavity, thin-walled casting):

[0043] 1. Currently, cast steel bow castings are produced by creating the main mold and core box using wooden models to form the cavity. When the bow length is long, the number of sand cores increases, making the process cumbersome and resulting in numerous core gaps, which makes dimensional control difficult. Furthermore, because cast steel bows are prone to bending and deformation, dimensional issues may cause deformation during later processing.

[0044] 2. Currently, there are still many problems with using 3D printed sand molds for large, multi-cavity, thin-walled castings, such as: how to perform sand mold parting and design, how to achieve venting, and how to place chills. In addition, if the entire manufacturing process is done using 3D printing, it is difficult to pre-fabricate the gating system and chills into the 3D printed sand core, and improper handling may even lead to sparking. Moreover, if the sand mold is entirely made using 3D printed sand cores, the sand core forming the outer surface of the bow also needs to be printed, which will result in long production time and high costs.

[0045] Based on the shortcomings of existing technologies, the researchers of this invention, after extensive research, theoretical analysis and experimental adjustments, proposed a casting method for large multi-cavity thin-walled castings that combines a "wooden master mold + 3D printed sand mold". This method achieves efficient, high-precision and cost-controllable production of large multi-cavity thin-walled castings. The core of the casting method lies in the design of the 3D printed sand mold.

[0046] This invention provides a method for designing a combined mold for multi-cavity thin-walled castings. The combined mold includes a 3D-printed sand mold and a wooden master mold, and includes the following steps:

[0047] S1: Based on the size and shape of the multi-cavity thin-walled casting and the hot spots during the casting process, determine the number of preset risers 1 and the number of sand molds; the sand mold is divided into upper and lower layers, and each layer of sand mold consists of several molds;

[0048] S2: The sand mold is designed according to the number of risers 1 and the module. Each sand mold is equipped with a "double-row comb-type" venting unit inside the mold.

[0049] S3: Design a wooden master mold according to the overall shape of the sand mold. The wooden master mold is used to pre-shape grooves in the sand box for setting the sand mold.

[0050] Specifically, the cast steel bow is a typical large, multi-cavity, thin-walled casting. Traditional core-splitting methods divide the main body cavity structure into multiple sand cores. The sand core splitting interface is generally the mid-section of the intermediate stiffener. This increases the number of sand cores, complicates the molding process, and easily causes dimensional deviations during core setting. This leads to problems such as one side being thickened while the other side is undersized during the later cleaning process, requiring finishing through welding and carbon planing. Due to the narrow cavity space, welding is difficult, and large-area welding can easily cause deformation of the bow body. The 3D-printed sand mold (composed of multiple sand mold splitting pieces) in the combined mold designed in this invention significantly reduces the number of sand cores compared to traditional methods (in the example, from the traditional 34 sand cores to 6 sand mold splitting pieces), effectively avoiding the aforementioned problems.

[0051] Specifically, since the hot spots of different castings are closely related to the casting shape, molten steel composition, and the angle of the cavity inside the mold, it is not possible to generalize. The hot spot information can be obtained by computer simulation or by referring to casting experience, and the number and location of risers can be determined based on the hot spot information. Furthermore, this invention proposes a universal riser design principle that is applicable to the internal cavity / mold design of most multi-cavity thin-walled castings.

[0052] Specifically, the design principle for the number of risers in step S1 is as follows: one riser is set at each end along the length of the multi-cavity thin-walled casting, and the number of risers in the middle position needs to meet the continuity requirement of 45-55% (the continuity of the riser is the ratio of the sum of the lengths of the riser roots to the circumference of the wheel shape, which is called the continuity of the riser); the cross-sectional shape of the riser is one of ellipse, square, rectangle or irregular polygon; the riser is also provided with reinforcing ribs (such as...). Figure 1(As shown). The above design principles can meet the feeding requirements of the multi-cavity thin-walled casting, and avoid insufficient strength of the sand mold due to too many risers. The function of the reinforcing ribs is to further improve the structural strength and avoid structural defects in the casting during the shaping and demolding process. In specific implementation, the setting of the reinforcing ribs can be carried out with reference to the existing technology. The final product will have the excess parts such as risers and ribs cut off and ground. Riser and ribs are not part of the final product.

[0053] Specifically, the number of sand mold splits per layer is determined based on the number of risers, the size and shape of the multi-cavity thin-walled casting, and the strength of the printing material used.

[0054] First, determine the number of sand mold sub-types based on the determined number of risers. The number of risers in a single sand mold sub-type is no more than 3, for example, 1, 2, 3, and the aspect ratio is no more than 2. As shown in Example 1, the number of risers is 6, each sand mold sub-type is set to contain 2 risers, the aspect ratio is 1.8, and the sand mold is divided into two layers. The final number of sand mold sub-types is 6.

[0055] It is worth noting that the structural dividing surface of a single sand mold is closely related to the shape of the specific casting. After determining the approximate number of sand molds based on the number of risers, the dividing surface of the sand mold naturally extends along the structural dividing surface of the casting. For example, it is divided along the extension surface of a certain rib of a multi-cavity thin-walled casting. For instance, in Example 1, the dividing surfaces of sand molds d, e, and f are formed by naturally extending the shape of the protruding parts. However, the upper sand molds a, b, and c, since their inner cavities are hollow and have no protruding structures, can be directly cut vertically. Furthermore, the dividing surfaces of the upper and lower sand molds can be determined according to the shape of the inner cavity / casting (e.g., Figure 4 (As shown).

[0056] Furthermore, the number of sand mold parts per layer is also related to the strength of the printing material used. If the printing material has high strength, the number of sand mold parts can be appropriately reduced based on the number of risers, and the aspect ratio of a single sand mold part can be appropriately increased, for example, to 1.5–2. If the material strength is low, to prevent sand mold collapse, the number of sand mold parts should be appropriately increased based on the number of risers, and the aspect ratio of a single sand mold part should be appropriately reduced, for example, to 1.0–1.5. It is worth noting that unless there are special requirements for the casting material, such as appropriately reducing material strength to pursue shear resistance, most common high-temperature resistant materials used in 3D printing are suitable for aspect ratios below 2, and sand mold collapse will not occur.

[0057] For example, common high-temperature resistant printing materials include high-temperature alloys such as nickel-based alloys and cobalt-based alloys. These alloys have extremely high creep resistance and oxidation resistance, making them suitable for extreme high-temperature environments. In addition, there are ceramic materials such as alumina and silicon nitride, which not only have high-temperature resistance but also good electrical insulation and wear resistance. In practical implementation, suitable high-temperature resistant printing materials can be selected based on factors such as casting temperature, surface quality requirements of the casting, and cost control.

[0058] Specifically, the "double-row comb-type" exhaust unit includes an air collection channel, an air guide channel, and an exhaust channel;

[0059] The air guide channel is set according to the shape of the inner cavity of the sand mold;

[0060] One end of the air collection channel is connected to the air guide channel, and the other end points to the inner cavity and maintains a certain distance from the surface of the inner cavity.

[0061] One end of the exhaust duct is connected to the air guide duct, and the other end points to the outer surface of the sand mold and is open to the atmosphere;

[0062] The interconnected air collection channel, air guide channel and exhaust channel constitute a complete "double-row comb-type" exhaust unit; at least one "double-row comb-type" exhaust unit is set in a single sand mold.

[0063] Specifically, one end of the gas collecting channel is close to the surface of the inner cavity, which helps to collect the gas generated during casting and solidification. After being collected by the gas guiding channel, the gas is finally discharged into the outside atmosphere through the exhaust channel. It is worth noting that the gas collecting channel and the exhaust channel should not be connected to the gas guiding channel at the same node, but should be staggered to avoid structural defects.

[0064] It is worth noting that after the 3D printed sand mold is assembled, if the exhaust port corresponding to the exhaust channel is located on the upper surface of the sand mold, no additional treatment is required to achieve exhaust; if the exhaust port corresponding to the exhaust channel is located inside the sand box (for example, the exhaust hole of the lower sand mold is generally located on the side), it is necessary to directly puncture the air hole during the sand box filling process or place a hollow nylon rope to connect the exhaust hole with the external atmosphere.

[0065] Specifically, the total cross-sectional area of ​​the air collection channel in each "comb-type" exhaust unit is S1, the total cross-sectional area of ​​the air guide channel is S2, and the total cross-sectional area of ​​the exhaust channel is S3, with S1:S2:S3 = (1.25~2.5):1:(2.0~3.0). When the above relationship is satisfied, the exhaust effect of the exhaust unit is optimal, and problems such as poor gas discharge are less likely to occur. On this basis, the total cross-sectional area of ​​the exhaust system (which may contain multiple exhaust units) should not be too large, otherwise it may lead to a decrease in the structural strength of the sand mold.

[0066] It is worth emphasizing that, in actual implementation, to further improve the venting effect, different venting units can be connected (with the same specifications as the guide duct), allowing multiple venting units within a single sand mold to be interconnected. This improves the venting effect when gas production in the inner cavity is uneven. However, it is important to note that during the design process, the multiple connected venting units must still individually meet the aforementioned cross-sectional area ratio relationship, rather than being calculated as a whole. Furthermore, the connecting duct itself can be an independent complete venting unit (i.e., including a gas collecting duct, a guide duct, and an exhaust duct) or simply used as a connecting duct (including a guide duct, which may include a gas collecting duct or an exhaust duct). The specific configuration can be flexibly determined based on the shape of the casting / inner cavity.

[0067] Specifically, the end of the gas collecting channel closest to the mold cavity is 150-250 mm away from the surface of the inner mold cavity. The purpose of placing one end of the gas collecting channel close to the surface of the inner mold cavity is to collect the gas generated during the casting process more efficiently, but the end face should not be too close to the surface of the inner mold cavity to avoid molten metal overflowing into the gas collecting channel.

[0068] Preferably, the sand mold parting also includes a chill reserved cavity and a fixing through hole; the chill reserved cavity is located on the inner cavity surface between adjacent risers, and the chill reserved cavity communicates with the outer surface of the sand mold parting through the fixing through hole.

[0069] Specifically, the edge dimension of the chill's reserved cavity is 2-3mm larger than the edge of the chill to facilitate subsequent chill installation; the diameter of the fixing through hole is 10-20mm, used for passing through the fixing reinforcing bar; corresponding positions on the fixing through hole of the sand mold parting surface are also provided with clamp clearance holes with a diameter of 100-350mm and a depth of 100-150mm. In actual implementation, the sand mold / sand mold parting is first printed, and then the fixing reinforcing bar is passed through the fixing through hole. One end of the fixing reinforcing bar is spot welded to the chill, and the other end is spot welded to a clamp (e.g., a short reinforcing bar or a rectangular iron sheet of suitable thickness). This fixing method is simple, easy to implement, and low in cost.

[0070] Specifically, the shape of the wooden main mold is the same as the lower half of the overall sand mold in the assembled state (e.g., Figure 7 (As shown); the height of the wooden master mold is 1 / 5 to 1 / 3 of the overall sand mold height. The function of the wooden master mold is to pre-press grooves in the sand box to match the sand mold, facilitating the insertion of the 3D printed sand mold / sand mold parting, and helping to improve the accuracy of sand mold assembly and positioning.

[0071] Preferably, the outer surface of the lower sand mold parting layer is provided with a positioning slope, specifically a slope of 1:8 to 12. The wooden main mold matches the outer surface of the lower sand mold parting layer. The positioning slope facilitates the insertion and assembly of the 3D printed sand mold / sand mold parting layer, and makes the positioning more accurate and stable.

[0072] The present invention also discloses a casting mold assembly, which includes a 3D printed sand mold and a wooden master mold designed by the design method.

[0073] The present invention also discloses a casting method for a multi-cavity thin-walled casting, wherein the casting method uses the casting mold combination to obtain the multi-cavity thin-walled casting after molding, pouring, and demolding.

[0074] Example 1

[0075] This embodiment provides a 3D printing sand mold design process and casting process for multi-cavity thin-walled castings, including:

[0076] S1: Based on the thermal points of the multi-cavity thin-walled cast steel bow (obtained through computer simulation and experience), a waist-shaped riser with a diameter of 300mm is set. According to the riser design principle, one riser is set at each end of the length direction. The total length of the cast steel bow is 6014mm. Calculated with a continuity of 50%, 6014×50%÷500=6.014≈6. Therefore, 6 φ300mm waist-shaped risers are placed evenly in the middle position. A single sand mold parting includes 2 waist-shaped risers and the sand mold includes upper and lower layers, for a total of 6 sand mold partsings. After the 6 sand mold partsings are combined, the inner cavity is the shape of the casting (including risers and auxiliary components such as ribs). The upper sand mold parting can be vertically cut, and the lower sand mold parting extends naturally along the shape of the protruding part to form a cutting surface / parting surface. The length-to-width ratio of a single sand mold parting is 1.8.

[0077] S2: After determining the number of risers, chills should be installed between every two risers for zoned feeding. The wall thickness of the cast steel bow is 80mm, and the thickness of the chills should be 0.5 to 0.85 times that, which is 40mm.

[0078] S3: The sand mold parting position should be as close as possible to one side of the cavity rib plate. There are 2 sand mold parting layers. The inner cavity structure is located in the lower sand mold parting layer. The positioning slope of each lower sand mold parting layer is 1:10 and the height is 120mm. There are a total of 6 sand molds (3 in the upper layer and 3 in the lower layer).

[0079] S4: When printing the sand mold, a chill cavity needs to be reserved. The gap between the chill cavity and the chill is 2mm. Print a 20mm hole after the chill cavity, which leads directly to the back of the sand mold. Reserve a clamp clearance hole with a diameter of 250mm and a depth of 150mm after the sand mold. After the sand mold is printed, first pass a φ12 steel bar through the small hole and spot weld it to the chill. Then break it at the clamp clearance hole and spot weld a short steel bar with a diameter of 30mm and a length of 220mm to fix the chill.

[0080] S5: When printing sand molds, directly print "double-layer comb-type" venting channels. The sand intake of the adjacent casting surface of the gas collecting channel is 200mm. Each part of the upper sand mold is equipped with two venting units. The cross-section of the gas collecting channel is φ6mm, and each is connected to a φ10mm guide channel. It is connected to the external atmosphere through a φ15mm venting channel. The three are staggered. In each venting unit, S1:S2:S3 = 1.8:1:2.5. The venting system of the lower sand mold (composed of venting units) has the same size as the upper sand mold and its shape is set according to the casting surface / inner cavity (the two venting units in sand molds a and c are connected by connecting channels). Alumina ceramic material is used for 3D printing and a matching wooden main mold is prepared. The height of the wooden main mold is 1 / 5 of the total height of the sand mold.

[0081] S6: Flatten the wooden sand box containing the main mold, flip the box over, remove the main mold, and then place the 3D printed sand mold / sand mold parting in sequence. Then flatten the sand mold with furan resin sand. The entire molding process takes 2 days (the existing molding process takes 7 days). After that, pour the casting to obtain a multi-cavity thin-walled cast steel bow column.

[0082] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for designing a combined mold for multi-cavity thin-walled castings, characterized in that, The combined mold includes a 3D printed sand mold and a wooden master mold, and includes the following steps: S1: Based on the size, shape, and hot spots of the multi-cavity thin-walled casting, determine the number of preset risers (1) and the number of sand molds; the sand mold is divided into upper and lower layers, and each layer of sand mold consists of several molds; S2: The sand mold is designed according to the number of risers (1) and the module. Each sand mold is equipped with a "double-row comb-type" venting unit. S3: Design a wooden main mold according to the overall shape of the sand mold. The wooden main mold is used to pre-shape a groove in the sand box for setting the sand mold. The number of sand molds for each layer is determined based on the number of risers (1), the size and shape of the multi-cavity thin-walled casting, and the strength of the printing material used. The "double-row comb-type" exhaust unit includes multiple air collection channels (2), air guide channels (3), and multiple exhaust channels (4); the air guide channels (3) are set according to the shape of the inner cavity of the sand mold; one end of the air collection channel (2) is connected to the air guide channel (3), and the other end points to the inner cavity and maintains a certain distance from the surface of the inner cavity; one end of the exhaust channel (4) is connected to the air guide channel (3), and the other end points to the outer surface of the sand mold and is connected to the atmosphere; the interconnected air collection channels (2), air guide channels (3), and exhaust channels (4) constitute a complete "double-row comb-type" exhaust unit; at least one "double-row comb-type" exhaust unit is provided in a single sand mold.

2. The design method according to claim 1, characterized in that, The design principle for the number of risers (1) in step S1 is to set one riser (1) at each end along the length of the multi-cavity thin-walled casting, and the number of risers (1) in the middle position should meet the continuity of 45-55%.

3. The design method according to claim 1, characterized in that, The total cross-sectional area of ​​the air collection channel (2) in each "double-row comb-type" exhaust unit is S1, the total cross-sectional area of ​​the air guide channel (3) is S2, and the total cross-sectional area of ​​the exhaust channel (4) is S3, S1:S2:S3 = (1.25~2.5):1:(2.0~3.0).

4. The design method according to claim 1, characterized in that, The end of the gas collecting channel (2) near the inner cavity is 150-250 mm away from the surface of the inner cavity.

5. The design method according to claim 1, characterized in that, The sand mold parting also includes a chilled iron reserved cavity (5) and a fixing through hole (6); the chilled iron reserved cavity (5) is located on the inner cavity surface between adjacent risers (1), and the chilled iron reserved cavity (5) is connected to the outer surface of the sand mold parting through the fixing through hole (6).

6. The design method according to claim 1, characterized in that, The shape of the wooden main mold is the same as the lower half of the overall sand mold in the assembled state; the height of the wooden main mold is 1 / 5 to 1 / 3 of the height of the overall sand mold.

Images