A method and die apparatus for profile core powder replication

Abstract

The application discloses a special-shaped core powder profiling pressing method and a mold device, relates to the field of workpiece machining, and comprises the following steps: raw material pretreatment, ingredient and raw material, mold preparation and information input, profiling regulation, core pressing, demolding and sintering setting. Differentiation position adjustment is performed on multiple independent lower mold punches to adjust the content of mixed raw materials in different areas in the mold cavity, so that the distribution of the mixed raw materials is matched with the shape of the special-shaped core to be pressed, sintering deformation, delamination or cracks caused by uneven density are effectively avoided, the overall density uniformity of the blank is ensured, the method is suitable for complex core structures, and the forming quality of the complex core structure is improved.

Description

Technical Field

[0001] This invention relates to the field of workpiece processing technology, and more specifically, to a method for conformal pressing of irregularly shaped core powder. Furthermore, this invention also relates to a mold apparatus for implementing the above-described method for conformal pressing of irregularly shaped core powder. Background Technology

[0002] Currently, the rapid growth of the automotive and avionics industries is also placing enormous pressure on my country's energy conservation and environmental protection. Lightweighting of automobiles and aircraft is of great significance for energy conservation, emission reduction, and industrial transformation and upgrading. In some precision castings for automobiles and aerospace, due to the practical requirements of assembly and working conditions, it is necessary to design a variety of small and complex cavities and holes of varying numbers and shapes. Traditional machining methods are difficult to use for manufacturing complex and small thin-walled parts; industrially, casting is often used for direct forming. It is against the backdrop of the rapid development of lightweight alloys, represented by aluminum alloys, and the practical needs of complex structural parts that casting technology has become increasingly stringent.

[0003] Therefore, the key to forming high-precision, complex cavity structures in thin-walled parts or channels lies in developing core materials suitable for integral, zero-margin molding of castings. The performance of the core directly determines the performance and quality of the casting. Currently, the biggest advantage of water-soluble cores is that the materials used are water-soluble, requiring only soaking in water or rinsing with a pressure water gun for cleaning, making the process simple and quick. Compared to other core materials that can only be removed through chemical corrosion or mechanical removal, this not only effectively reduces core cleaning time and shortens the casting production cycle but also avoids potential damage to the casting caused by chemical corrosives and mechanical stress.

[0004] Currently, the main industrial methods for core production are unidirectional and bidirectional pressing. However, these methods are difficult to apply to high-strength water-soluble salt cores or complex irregular core structures. Because irregular core powder parts have varying heights and complex cross-sections, unidirectional or bidirectional pressing cannot achieve comprehensive control over powder uniformity, weight, displacement, and pressing force during the pressing process. This makes it difficult to guarantee the density uniformity and stability of the pressed parts. Furthermore, it is difficult to match the pressing process to the size and shape of the object, resulting in uneven density, significant density differences in all directions, and a large amount of blank allowance. Additionally, irregular powder molded parts cannot be machined and can only be manually polished, affecting product quality and making it difficult to meet the requirements for consistent product performance.

[0005] In conclusion, improving the molding quality and consistency of irregularly shaped cores is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a method for conformal pressing of irregular core powder. The conformal pre-distribution makes the powder dosage more accurate and reduces waste. The uniform pressing ensures the isotropic nature of the irregular core blank, which is suitable for complex core structures and improves the consistency of core forming.

[0007] Another object of the present invention is to provide a mold device for implementing the above-described irregular core powder conformal pressing method.

[0008] To achieve the above objectives, the present invention provides the following technical solution:

[0009] A method for conformal pressing of irregularly shaped core powder, comprising:

[0010] Prepare the types of raw materials required for the irregularly shaped core to be pressed, and dry all raw materials separately.

[0011] Weigh all the individual ingredients according to the preset ratio and mix them to obtain the mixed ingredients;

[0012] Install the pressing mold and dry it. Input the three-dimensional model information of the irregular core to be pressed and the powder quantitative information into the mold's control system.

[0013] The control system controls multiple independent lower die punches in the mold to perform differentiated position adjustments based on the three-dimensional model information, so as to adjust the content of mixed raw materials in different areas of the mold cavity and make its distribution match the shape of the irregular core to be pressed.

[0014] The control system controls the upper die punch and multiple lower die punches to move in a preset order and speed until the upper die punch and lower die punches come into contact, so that a closed pressing cavity is formed between the upper die punch and lower die punches, and pressure holding and heating are performed for a preset time.

[0015] The upper die punch is raised and the lower die punch is driven to eject the shaped core part.

[0016] The shaped core is sintered and fixed to obtain the finished shaped core.

[0017] Furthermore, in this invention, the required types of single raw materials for preparing the irregularly shaped core to be pressed are prepared, and all single raw materials are dried separately.

[0018] The drying temperature is 185℃~225℃, and the drying time is 1.8h~2.5h;

[0019] The process involves weighing all individual raw materials according to a preset ratio and mixing them together to obtain a mixed raw material.

[0020] All raw materials were mixed using a ball mill for 65–89 minutes, with a ball-to-material ratio of 1.2–2.3.

[0021] Furthermore, in this invention, the installation and drying of the pressing mold, and the input of the three-dimensional model information of the irregular core to be pressed and the powder quantitative information into the mold's control system;

[0022] After drying the pressing mold, apply a parting agent to the contact area between the pressing mold and the mixed raw materials.

[0023] Furthermore, the present invention involves sintering and shaping the irregularly shaped core to obtain the finished irregularly shaped core;

[0024] The sintering and shaping temperature is first raised to 650℃~700℃ and held for 2.5~4.5h, then cooled with the furnace at a rate of 2~5℃ / min.

[0025] Furthermore, in this invention, the required types of single raw materials for preparing the irregularly shaped core to be pressed are prepared, and all single raw materials are dried separately.

[0026] The required single raw materials include potassium chloride, molybdenum disulfide powder, potassium titanate whiskers, talc, sodium bentonite, water glass, and sodium chloride. Further, in this invention, all single raw materials are weighed according to a preset ratio, and all single raw materials are mixed to obtain a mixed raw material:

[0027] The preset ratio is as follows by mass fraction: potassium chloride 15.4-19.3, molybdenum disulfide powder 4.3-6.8, potassium titanate whiskers 1.3-2.7, talc powder 0.3-1.7, sodium bentonite 1.1-4.4, water glass 4.6-6.7, and the balance is sodium chloride.

[0028] A mold-making device for the irregular core powder conformal pressing method, comprising:

[0029] Frame, powder feeding hopper, feeding pipe, feeding cart and quantitative feeding device;

[0030] The powder feeding hopper and the quantitative feeding device are both fixed to the frame. The two ends of the feeding pipe are respectively used to connect the discharge port of the powder feeding hopper and the inlet of the quantitative feeding device. The pressing mold is installed on the frame. The feeding cart receives the mixed raw materials conveyed by the quantitative feeding device and sends the mixed raw materials into the pressing mold.

[0031] Furthermore, the pressing mold of the present invention includes:

[0032] The upper mold assembly includes an upper mold head, an upper mold ejector rod, and an upper mold hydraulic cylinder. The upper mold ejector rod is slidably mounted on the machine frame. The upper mold head is fixed to the end of the upper mold ejector rod. The upper mold hydraulic cylinder is fixedly mounted on the machine frame and is used to control the sliding of the upper mold ejector rod.

[0033] The lower mold assembly includes at least two lower mold heads, at least two lower mold ejector rods, at least two lower hydraulic cylinders, and a lower mold fixing plate. The lower mold fixing plate is fixed to the frame. The at least two lower mold heads are slidably engaged with the lower mold fixing plate. The at least two lower mold ejector rods are respectively fixedly connected to their corresponding lower mold heads. The at least two lower hydraulic cylinders are respectively connected to their corresponding lower mold ejector rods, so that the at least two lower mold heads can move independently. This enables the control system to control multiple independent lower mold punches in the mold to perform differentiated position adjustments based on the three-dimensional model information.

[0034] A mold temperature controller is installed on the frame and electrically connected to the control system. The upper mold head, the lower mold head, and the lower mold fixing plate are all equipped with temperature control pipelines, which are connected to the mold temperature controller.

[0035] Furthermore, the upper mold assembly further includes:

[0036] The upper mold sleeve is fixedly connected to the upper mold ejector rod, and the upper mold head is detachably connected to the upper mold sleeve.

[0037] Furthermore, the lower mold assembly further includes:

[0038] A positioning plate is installed on the frame, and at least two lower mold ejector rods are slidably engaged with the positioning plate. The lower mold head is detachably connected to the lower mold ejector rod.

[0039] The irregular core powder conformal pressing method provided by this invention involves placing the raw materials required for the irregular core part into the mold. The control system 8 then controls multiple independent lower die punches in the mold to perform differentiated position adjustments based on the three-dimensional model information. This adjusts the content of mixed raw materials in different areas of the mold cavity, ensuring that their distribution matches the shape of the irregular core part to be pressed. Therefore, by conformal control of the pre-distributed powder, the density gradient problem caused by uneven filling of the irregular part is solved. Through the relative movement and cooperation of multiple die punches, the geometric accuracy of the core part is high, and the blank allowance is extremely small, which can save a lot of machining processes. It is particularly suitable for complex internal cavity shapes that cannot be machined.

[0040] The present invention also provides a mold device for implementing the above-mentioned irregular core powder conformal pressing method. Through three independent control points, the upper mold with independent control can more accurately simulate and pre-compensate the cross-sectional changes of the product in the radial direction (from the center to the edge). The differentiated pressure settings can actively balance the pressure loss gradient of the powder caused by friction and shape during the pressing process, thereby ensuring the overall density uniformity of the blank and effectively avoiding sintering deformation, delamination or cracks caused by uneven density. Furthermore, the conformal pre-distribution makes the powder dosage more accurate and reduces waste. Uniform pressing ensures the isotropy of the irregular core blank, resulting in high dimensional accuracy and uniform thermal expansion after sintering, achieving near-net-shape forming and saving a lot of subsequent processing. It is especially suitable for complex core structures. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of the method steps provided by the present invention;

[0043] Figure 2 This is a schematic diagram of the overall structure of the pressing mold provided by the present invention;

[0044] Figure 3 This is a partially enlarged structural diagram of the upper and lower molds provided by the present invention;

[0045] Figure 4 This is a structural schematic diagram of the upper and lower molds during material feeding provided by the present invention;

[0046] Figure 5 This is a structural schematic diagram of the upper and lower molds during the contouring adjustment process provided by the present invention;

[0047] Figure 6 A schematic diagram of the structure of the upper and lower molds in their initial pressing state provided by the present invention;

[0048] Figure 7 A schematic diagram of the structure of the upper and lower molds under pressing and holding pressure as provided in this invention;

[0049] Figure 8 This is a structural schematic diagram of the upper and lower molds in the state of ejection provided by the present invention;

[0050] Figure 9 A schematic diagram of the cross-section of the irregular core structure provided by the present invention;

[0051] Figure 10 This is a top view of the irregular core structure provided by the present invention;

[0052] Figure 11 This is a schematic diagram of the pressurization process of the upper die punch provided by the present invention;

[0053] Figure 12 This is a schematic diagram of the pressurization process of the first lower die punch provided by the present invention;

[0054] Figure 13 This is a schematic diagram of the pressurization process of the second lower die punch provided by the present invention;

[0055] Figure 14 This is a schematic diagram of the pressurization process of the third lower die punch provided by the present invention.

[0056] Figures 1 to 14 In the accompanying drawings, the reference numerals include:

[0057] 1. Rack;

[0058] 2. Powder delivery hopper;

[0059] 3. Feeding tube;

[0060] 4. Quantitative feeding device;

[0061] 5. Feeding cart;

[0062] 6. Pressing mold;

[0063] 61. Install the mold assembly;

[0064] 611. Upper mold hydraulic cylinder; 612. Upper mold ejector pin; 613. Upper mold head; 614. Upper mold sleeve;

[0065] 62. Lower mold assembly;

[0066] 621. Lower die fixing plate; 622. Third lower die punch; 623. First lower die punch; 624. Second lower die punch; 625. Positioning plate; 626. Lower hydraulic cylinder; 627. Lower die ejector pin;

[0067] 7. Mold temperature controller;

[0068] 8. Control system;

[0069] 9. Temperature control piping. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] The core of this invention is to provide a method for conformal pressing of irregular core powder. The conformal pre-distribution makes the powder dosage more accurate and reduces waste. Uniform pressing ensures the isotropic nature of the irregular core blank, which is suitable for complex core structures.

[0072] Another object of the present invention is to provide a mold device for implementing the above-described irregular core powder conformal pressing method.

[0073] Please refer to Figure 2 A method for conformal pressing of irregularly shaped core powder, comprising:

[0074] S1. Raw material pretreatment: Prepare the types of single raw materials required for the irregular core to be pressed, and dry all the single raw materials separately. That is, dry the various single raw materials required for manufacturing the irregular core separately to remove the moisture adsorbed by the raw materials and prevent bubbles or cracks from being generated during subsequent pressing and sintering.

[0075] S2. Ingredients and Raw Materials: Weigh all the single raw materials according to the preset ratio and mix them to obtain the mixed raw materials. That is, according to the optimized preset ratio, accurately weigh each dried single raw material and put them into the mixing equipment for thorough mixing to obtain a mixed raw material with uniform composition.

[0076] S3. Mold preparation and information input: Install the pressing mold 6 and dry it. Input the three-dimensional model information of the irregular core to be pressed and the powder quantitative information into the mold control system 8. That is, install the powder pressing mold 6 for irregular cores and dry it. Then input the three-dimensional digital model of the irregular core to be pressed (including its precise geometry) and the calculated powder quantitative information (total weight and possible local weight distribution and loss, etc.) into the mold control system 8.

[0077] S4. Contouring Control: The control system 8 controls multiple independent lower die punches in the mold to perform differentiated position adjustments based on the three-dimensional model information, so as to adjust the content of mixed raw materials in different areas of the mold cavity and make its distribution match the shape of the irregular core to be pressed. That is, the control system 8 of the mold analyzes the three-dimensional model and identifies the thickness changes of different sections of the irregular core. Then, it independently and differentiates the multiple lower die punches to perform precise position adjustments, so as to achieve the "pre-distribution" of powder in the mold cavity to match the product shape. The goal is to ensure that the compression ratio of powder in each part tends to be consistent during pressing. For example, in the area where the cross section of the irregular core is thicker, the corresponding lower die punch moves slightly downward to reserve more powder filling space in that area. In the area where the cross section is thinner, the reserved space is reduced.

[0078] S5. Core Pressing: The control system 8 controls the upper die punch and multiple lower die punches to move in a preset order and speed until the upper die punch and lower die punches contact each other, so that a closed pressing cavity is formed between the upper die punch and lower die punches. The pressure is held and heated for a preset time. That is, the upper die punch moves downward under the drive of the control system 8, while each lower die punch moves in coordination according to a preset program, so that the upper and lower die punches close and form a closed pressing cavity corresponding to the shape of the product. In this state, the system heats the mold (e.g., to 150-180°C) and applies a preset pressure to each punch for pressure holding. Heating softens the binder and promotes the bonding between powder particles. Pressure holding ensures that the pressure is fully transmitted, causing the powder particles to undergo plastic deformation and rearrangement, and densification.

[0079] S6. Demolding: Raise the upper die punch and drive the lower die punch to eject the molded irregular core part;

[0080] S7. Sintering and Shaping: The shaped irregular core is sintered and shaped to obtain the finished irregular core. In other words, the green blank is sent into the sintering furnace for sintering and shaping. The binder is cured by high temperature, and metallurgical bonding or sintering neck is generated between the particles, thereby obtaining a finished irregular core with sufficient strength.

[0081] In a specific implementation of this invention, after the raw materials required for the irregular core part are placed in the mold, the control system 8 controls multiple independent lower die punches in the mold to perform differentiated position adjustments based on the three-dimensional model information, so as to adjust the content of mixed raw materials in different areas of the mold cavity and make its distribution match the shape of the irregular core part to be pressed. Therefore, by controlling the pre-distributed powder through contouring, the density gradient problem caused by uneven filling of the irregular part is solved. Through the relative movement and cooperation of multiple die punches, the geometric accuracy of the core part is high and the blank allowance is extremely small, which can save a lot of machining processes and is particularly suitable for complex internal cavity shapes that cannot be machined.

[0082] In one embodiment, in the step of preparing the types of single raw materials required for pressing the irregular core parts and drying all the single raw materials separately, the drying temperature is 185℃~225℃ and the drying time is 1.8h~2.5h. That is, the drying temperature is strictly controlled within 185℃~225℃ and the time is controlled within 1.8h~2.5h. Within this temperature range, the crystal water and adsorbed water in the raw materials can be effectively removed, while avoiding the premature melting or decomposition of some low melting point components (such as some chlorides). The time range ensures a balance between the thoroughness of drying and production efficiency.

[0083] In one embodiment, in the step of preparing the types of single raw materials required for the irregular core to be pressed and drying all single raw materials separately, a ball mill is used to mix all single raw materials for a mixing time of 65 to 89 minutes and a ball-to-material ratio of 1.2 to 2.3. That is, in this step, the raw materials are mixed using a ball mill for a mixing time of 65 to 89 minutes and a ball-to-material ratio (mass ratio of grinding balls to raw materials) of 1.2 to 2.3. In addition, the rotation speed range is 238 to 459 rpm, which ensures that the components can be fully mixed.

[0084] In one embodiment, in the step of installing and drying the pressing mold 6, and inputting the three-dimensional model information of the irregular core to be pressed and the powder quantitative information into the mold control system 8, after drying the pressing mold 6, a parting agent is applied to the contact position between the pressing mold 6 and the mixed raw material. The parting agent is generally an organic solvent that does not dissolve inorganic salts, such as silicone oil, to facilitate demolding. That is, after drying the mold, a thin layer of parting agent is evenly coated on all possible contact positions with the mixed raw material, such as the mold cavity wall, the end face of the upper mold punch, and the end face of the lower mold punch, using a brush or spraying equipment. This prevents the green blank from being damaged or sticking to the mold during ejection, especially for cores with complex shapes, undercuts, or thin-walled structures. It can also reduce the wear and corrosion of the mold surface by powder, extend the service life of the mold, and help obtain a smooth, scratch-free irregular core blank surface.

[0085] In the above embodiments, the separating agent is preferably an organic solvent that does not dissolve inorganic salts, most typically silicone oil. Silicone oil has excellent high temperature resistance, chemical inertness and demolding performance. It can form a stable isolation film during high temperature pressing, effectively preventing salt powder from sticking to the mold, ensuring a smooth demolding process, and not contaminating the product.

[0086] In other embodiments, the release agent may also be a special release wax, a polytetrafluoroethylene suspension, or an alcoholic solution of stearate.

[0087] In one embodiment, in the step of sintering and shaping the irregularly shaped core to obtain the finished irregularly shaped core, the sintering and shaping temperature is first raised to 650℃~700℃ and held for 2.5~4.5h, then cooled in the furnace at a rate of 2~5℃ / min. That is, the irregularly shaped core blank after demolding is heated to 650℃~700℃ in the furnace and held at this temperature for 2.5~4.5 hours. The high temperature range is sufficient for the silicate binder such as water glass to fully melt, flow and wet the powder particles. The potassium titanate whiskers are coated with sodium chloride and potassium chloride to form potassium titanate whisker aggregates. Subsequently, during the cooling process, they vitrify to form a strong network structure that firmly binds the particles. At the same time, this process can further remove residual volatiles and promote diffusion bonding between particles. After the holding time is completed, the slow cooling in the furnace can effectively reduce product cracking or deformation caused by uneven thermal stress. Through sufficient holding time and slow transition between high and low temperatures, the internal stress of compression is released, making the product dimensions more stable and the thermal expansion rate lower.

[0088] In one embodiment, in the step of preparing the types of single raw materials required for pressing the irregularly shaped core and drying all the single raw materials separately, the required types of single raw materials include potassium chloride, molybdenum disulfide powder, potassium titanate whiskers, talc, sodium bentonite, water glass, and sodium chloride, and their mass fraction ratio is as follows: potassium chloride 15.4-19.3, molybdenum disulfide powder 4.3-6.8, potassium titanate whiskers 1.3-2.7, talc 0.3-1.7, sodium bentonite 1.1-4.4, water glass 4.6-6.7, and the balance is sodium chloride.

[0089] Specifications, models and chemical formulas of each component raw material

[0090] Raw material name Specifications, models and chemical formulas Potassium chloride powder Purity ≥ 99%, main component is KCl Sodium chloride powder Purity ≥ 99%, main component is NaCl Potassium titanate whiskers <![CDATA[K2O-6TiO2, with a diameter of 0.2 - 0.5 um and a length of 10 - 20 um. 2O·6TiO2]]> Molybdenum disulfide powder <![CDATA[Purity ≥ 99%, the main component is MoS2]]> talcum powder <![CDATA[Hydrous magnesium silicate, 63 wt% SiO2 and 2 wt% MgO, the rest being water; 100 - 300 mesh]]> Sodium bentonite <![CDATA[The main components are 50 - 70wt% SiO2, 10 - 15wt% Al2O3 and 1 - 5wt% Na2O, and the rest is water]]> Water glass <![CDATA[The main components are 8 - 13.5% Na2O and 24 - 28% SiO2, and the rest is water. The pH value is 10 - 13, and the solid content is 35 - 45%]]>

[0091] Sodium chloride and potassium chloride form a water-soluble matrix, while potassium titanate whiskers act as a reinforcing agent. Due to their high heat resistance (melting point of 1370℃, far exceeding that of the matrix NaCl and KCl), potassium titanate whiskers are very stable in molten salt. Furthermore, the potassium titanate whiskers are extremely small (0.2–0.5 μm in diameter and 10–20 μm in length). After dispersing in the molten salt, they are encapsulated by the matrix phase. The potassium titanate whiskers inside the melt can serve as nuclei for internal equiaxed crystals. The more effective nucleation sites formed by the potassium titanate whiskers, the smaller the equiaxed crystal size, effectively improving the salt core strength, toughness, heat resistance, and wear resistance.

[0092] Furthermore, molybdenum disulfide powder serves as a key forming lubricant, talc and sodium bentonite serve as auxiliary binders and plasticizers, and water glass serves as the main high-temperature binder. By introducing an appropriate amount of low surface energy molybdenum disulfide powder (surface energy of about 40-50 mJ / m²), they play a friction-reducing role between particles, making the powder flow more uniformly and the particles rearrange more fully during conformal filling and pressing, thus obtaining a high-density and high-uniformity green body even under complex shapes.

[0093] A mold-making device for implementing a method of conformal pressing of irregularly shaped core powder, comprising:

[0094] Frame 1, powder feeding bin 2, feeding pipe 3, feeding cart 5, and quantitative feeding device 4;

[0095] The frame 1 provides overall structural support and installation reference. The powder feeding bin 2 and the quantitative feeding device 4 are both fixed to the frame 1. The powder feeding bin 2 is fixed to the upper part of the frame 1 and is used to store the mixed raw materials. At the same time, a vibrator or agitator is provided at its bottom to prevent powder bridging. The two ends of the feeding pipe 3 are used to connect the discharge port of the powder feeding bin 2 and the inlet of the quantitative feeding device 4, respectively. The pressing mold 6 is installed on the frame 1. The feeding cart 5 receives the mixed raw materials conveyed by the quantitative feeding device 4 and delivers the mixed raw materials into the pressing mold 6. That is, the feeding cart 5 receives the raw materials accurately measured by the quantitative feeding device 4 and moves along the guide rail to pour the raw materials into the mold cavity of the pressing mold 6 below. Automated feeding reduces manual operation links and errors, and accurate quantitative feeding is conducive to controlling product uniformity.

[0096] Please refer to Figure 2 In some embodiments, the pressing mold 6 includes an upper mold assembly 61 and a lower mold assembly 62. The upper mold assembly 61 includes an upper mold head 613, an upper mold ejector rod 612, and an upper mold hydraulic cylinder 611. The upper mold ejector rod 612 is slidably mounted on the frame 1. The upper mold head 613 is fixed to the end of the upper mold ejector rod 612 and is used to directly contact the powder. The upper mold hydraulic cylinder 611 is fixedly mounted on the frame 1 and is used to provide downward pressing power. The upper mold ejector rod 612 is connected to the piston rod of the hydraulic cylinder and is slidably mounted on the frame 1 on a precision guide rail to transmit pressure and displacement.

[0097] The lower mold assembly 62 includes at least two lower mold heads, at least two lower mold ejector rods 627, at least two lower hydraulic cylinders 626, and a lower mold fixing plate 621. The lower mold fixing plate 621 is fixed to the frame 1. The at least two lower mold heads are slidably engaged with the lower mold fixing plate 621, that is, the at least two lower mold heads are slidably engaged with the fixing plate through guide pillars and guide sleeves, and can move independently vertically. Therefore, each lower mold head is responsible for forming different areas of the core. The at least two lower mold ejector rods 627 are fixedly connected to the corresponding lower mold heads, and the at least two lower hydraulic cylinders 626 are connected to the corresponding lower mold ejector rods 627, so that the at least two lower mold heads can move independently. This enables the control system 8 to control multiple independent lower mold punches in the mold to perform differentiated position adjustments based on the three-dimensional model information. The position, speed, and pressure of each punch can be independently controlled in a closed loop with high precision.

[0098] In one embodiment, the pressing mold 6 also includes a mold temperature controller 7, which is mounted on the frame 1 and electrically connected to the control system 8. The upper mold head 613, the lower mold head, and the lower mold fixing plate 621 are all provided with temperature control pipes 9, which are connected to the mold temperature controller 7. That is, the temperature of the mold is controlled by the temperature control pipes 9, and the heating and cooling of the mold is controlled by the mold temperature controller 7. The ends of the temperature control pipes 9 on the mold are all provided with quick-release connectors to facilitate the quick connection of the control pipes when changing different molds.

[0099] In one embodiment, the upper mold assembly 61 further includes an upper mold sleeve 614, which is fixedly connected to the upper mold ejector rod 612. The upper mold head 613 is detachably connected to the upper mold sleeve 614. That is, the upper mold sleeve 614 is a cylindrical or frame-shaped structure that is fixedly connected to the upper mold ejector rod 612. The upper mold head 613 is detachably connected to the upper mold sleeve 614 by means of screws, quick-change connectors, etc. When different products need to be produced, only the upper mold head 613 of the corresponding shape needs to be replaced, without disassembling the entire upper mold assembly 61, which greatly shortens the mold change time. Damaged or worn mold heads can be replaced quickly and individually, reducing maintenance costs. Moreover, the mold change is fast and suitable for small-batch, multi-variety irregular-shaped cores.

[0100] In one embodiment, the lower mold assembly 62 further includes a positioning plate 625, which is mounted on the frame 1. At least two lower mold ejector rods 627 are slidably engaged with the positioning plate 625. The lower mold head is detachably connected to the lower mold ejector rods 627. That is, the positioning plate 625 is mounted on the frame 1 and located above the lower mold fixing plate 621. The positioning plate 625 is machined with high-precision guide holes. All lower mold ejector rods 627 pass through these guide holes and form a sliding engagement with the positioning plate 625, providing precise and consistent vertical movement guidance for multiple lower mold ejector rods 627. This ensures the coaxiality and synchronization accuracy of multiple lower mold heads under complex movements. Furthermore, the mold head and its ejector rods are detachably connected (such as by threaded connection or flange connection), which allows for the replacement of lower mold heads with different profiles according to the product shape, and facilitates the grinding, repair, or replacement of individual mold heads.

[0101] Please refer to Figure 9 As shown in the irregular core structure, in this embodiment, one upper die punch and three lower die punches are used as the pressing mold 6. The three lower die punches are located at the first lower die punch 623, the second lower die punch 624, and the third lower die punch 622, respectively. The third lower die punch 622 is cylindrical, while the first lower die punch 623 and the second lower die punch 624 are both annular structures and are arranged coaxially with the third lower die punch 622. The first lower die punch 623 is located on the outermost side, and the first lower die punch 623... The second lower die punch 624 and the third lower die punch 622 slide and seal, while the outer side of the first lower die punch 623 slides and engages with the lower die fixing plate. The upper die punch, the first lower die punch 623, the second lower die punch 624 and the third lower die punch 622 are respectively provided with grooves corresponding to the irregular core structure on their respective sides that are close to each other. Therefore, when the upper die punch, the first lower die punch 623, the second lower die punch 624 and the third lower die punch 622 are completely closed, a cavity matching the irregular core structure can be formed.

[0102] In use, the first lower die punch 623, the second lower die punch 624, and the third lower die punch 622 are all rigidly connected to the piston rod of an independent lower hydraulic cylinder 626 (or an electric servo cylinder) via a robust lower die ejector rod 627, and can receive independent commands from the control system. Furthermore, because the first lower die punch 623, the second lower die punch 624, and the third lower die punch 622 each have a groove structure corresponding to the irregular core structure, the three punches divide the bottom area of ​​the mold cavity into three independent controllable areas, enabling the control system 8 to control the cross-section of the core. The powder filling amount, pressing speed, and pressure at different radial positions (from the center to the edge) are independently and precisely controlled. Therefore, in the shaping step, the first lower die punch 623, the second lower die punch 624, and the third lower die punch 622 form a stepped or curved surface that matches the product cross-section in the vertical direction. That is, in the thicker area of ​​the final core design, the corresponding punch moves down more, leaving more powder space and being able to retain more powder material. In the thinner area, the reserved space is smaller. The purpose is to make the powder compression ratio of each area tend to be consistent during subsequent pressing.

[0103] During the pressing process, the upper die punch begins to descend, while the three lower punches do not remain stationary. Instead, they move in coordination according to a preset program. The three lower punches retract slightly or remain stationary at different speeds to ensure that the powder can be evenly filled during the mold closing process, avoiding "bridging" or the formation of voids. Finally, when the upper die punch reaches the predetermined position, the three lower punches also reach their final "pressing position," forming a completely closed, precision cavity with a shape consistent with the product together with the upper die punch and the die sleeve.

[0104] Specifically, in the embodiment employing one upper die punch and three lower die punches, the specific implementation methods of the upper die punch and lower die punches are as follows:

[0105] The upper die punch pressurization is mainly divided into the following three stages, namely L1 to L3. Please also refer to... Figure 11 The diagram shows the pressure application process of the upper die punch:

[0106] In stage L1, the pressure is 0–256 kN, the pressing time is 2.5–7.5 s, and the pressing speed is 0–3.5 mm / s. This allows the loose powder to slowly slide and fill the gaps with powder, which is the powder filling stage.

[0107] The L2 stage involves applying pressure of 256–986 kN, a pressing time of 7.5–13.5 s, and a pressing speed of 3.5–6.5 mm / s, which compacts the powder and rapidly increases the contact area between powder particles, belonging to the powder plastic compaction stage.

[0108] In stage L3, a short, rapid pressurization is applied, reaching its maximum pressure. The pressurization time is 13.5–14.3 seconds, the pressure is 986–1301 kN, and the pressing speed is 7.9–12.5 mm / s. Simultaneously, after reaching the maximum pressure, the pressure is held at 1301 kN for 14.3–30 seconds. This process compacts the powder, dramatically increasing the contact area between powder particles, representing the plastic compaction stage. Therefore, this three-stage pressurization method densifies the powder, bringing the powder molded part close to its theoretical density. Elastic compression within the crystals between particles forms the powder, representing the powder densification stage. This step is therefore crucial for ensuring the density of the pressed powder.

[0109] The first pressurization of the lower die punch 623 is mainly divided into the following three stages, namely P1 to P3. Please also refer to... Figure 12 The diagram shows the pressure application process of the first lower die punch 623:

[0110] In stage P1, the pressure is 0–123 kN, the pressurization time is 3.5–8.5 s, and the pressing speed is 0–2.5 mm / s.

[0111] In stage P2, the pressurization pressure is 123–456 kN, the pressurization time is 8.5–14.3 s, and the pressing speed is 2.5–5.5 mm / s.

[0112] In stage P3, the pressure is 456–501 kN, the pressing time is 14.3–30 s, and the pressing speed is 0–1.5 mm / s. This stage mainly works in conjunction with the pressing force applied by the upper die punch to densify the powder.

[0113] The second lower die punch 624 pressurization is mainly divided into the following three stages, namely D1 to D3. Please also refer to... Figure 13 The diagram shows the pressure application process of the second lower die punch 624:

[0114] In stage D1, the pressure is 52–123 kN, the pressurization time is 0–8.5 s, and the pressing speed is 0–2.0 mm / s.

[0115] In stage D2, the pressure is 123–502 kN, the pressurization time is 8.5–14.3 s, and the pressing speed is 2.5–5.5 mm / s. Among them, the pressurization pressure is 267 kN, the pressure is held for 2 s, and the pressing speed is 0–4.5 mm / s.

[0116] In stage D3, the pressure is 502–718 KN, the pressing time is 14.3–30 s, and the pressing speed is 0–3.5 mm / s. This stage mainly works in conjunction with the reverse pressing force applied by the upper die punch to densify the powder.

[0117] The third lower die punch 622 pressurization is mainly divided into the following three stages, namely P1 to P3. Please also refer to... Figure 14The diagram shows the pressure application process of the first lower die punch 623:

[0118] In the E1 stage, the pressurization pressure is 0–98 kN, the pressurization time is 3.5–10.5 s, and the pressing speed is 0–2.5 mm / s.

[0119] The E2 stage pressurization pressure is 98KN, the pressurization time is 10.5~15.9s, and the pressing speed is 2.5~5.5mm / s;

[0120] In stage E3, the pressure is 98 kN, the pressing time is 15.9–21.5 s, and the pressing speed is 0–1.5 mm / s. This stage mainly involves the pressing force applied by the upper die punch to densify the powder.

[0121] Therefore, the lower mold, through three independent control points, in conjunction with the independently controlled upper mold, can more accurately simulate and pre-compensate for the radial cross-sectional changes of the product (from the center to the edge). This solves the fatal flaw of traditional unidirectional or bidirectional pressing, which can only control the overall height but cannot control the uniform distribution of cross-sectional density. Differentiated pressure settings can actively balance the pressure loss gradient of powder caused by friction and shape during pressing, thereby ensuring the overall density uniformity of the blank. This effectively avoids sintering deformation, delamination, or cracks caused by uneven density. Furthermore, the conformal pre-distribution makes the powder dosage more precise, reducing waste. Uniform pressing ensures the isotropy of irregular core blanks, resulting in high dimensional accuracy and uniform thermal expansion after sintering, achieving near-net-shape forming and saving a lot of subsequent processing. It is especially suitable for complex core structures.

[0122] In addition to the irregular core powder conformal pressing method disclosed in the above embodiments, the present invention also provides a mold equipment for implementing the above irregular core powder conformal pressing method. The structure of other parts of the mold equipment is described in the prior art and will not be repeated here.

[0123] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0124] The foregoing has provided a detailed description of the irregular core powder conformal pressing method and mold equipment provided by the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are merely for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A method for conformal pressing of irregularly shaped core powder, characterized in that, include: Prepare the types of raw materials required for the irregularly shaped core to be pressed, and dry all raw materials separately. Weigh all the individual ingredients according to the preset ratio and mix them to obtain the mixed ingredients; Install the pressing mold (6), dry the pressing mold (6), and input the three-dimensional model information of the irregular core to be pressed and the powder quantitative information into the mold control system (8). The control system (8) controls multiple independent lower die punches in the mold to perform differentiated position adjustments based on the three-dimensional model information, so as to adjust the content of mixed raw materials in different areas of the mold cavity and make its distribution match the shape of the irregular core to be pressed. The control system (8) controls the upper die punch and multiple lower die punches to move in a preset order and speed until the upper die punch and the lower die punches come into contact, so that a closed pressing cavity is formed between the upper die punch and the lower die punch, and pressure holding and heating are performed for a preset time. The upper die punch is raised and the lower die punch is driven to eject the shaped core part. The shaped core is sintered and fixed to obtain the finished shaped core.

2. The irregular core powder conformal pressing method according to claim 1, characterized in that, The process involves preparing the types of single raw materials required for the irregularly shaped core to be pressed, and drying all single raw materials separately. The drying temperature is 185℃~225℃, and the drying time is 1.8h~2.5h; all the single raw materials are weighed according to the preset ratio and mixed to obtain a mixed raw material; All raw materials were mixed using a ball mill for 65–89 minutes, with a ball-to-material ratio of 1.2–2.

3.

3. The irregular core powder conformal pressing method according to claim 2, characterized in that, The installation of the pressing mold (6) is carried out, and the pressing mold (6) is dried. The three-dimensional model information of the irregular core to be pressed and the powder quantitative information are input into the control system (8) of the mold. After drying the pressing mold (6), apply a parting agent to the contact area between the pressing mold (6) and the mixed raw materials.

4. The irregular core powder conformal pressing method according to claim 3, characterized in that, The shaped irregular core is sintered and shaped to obtain the finished irregular core; The sintering and shaping temperature is first raised to 650℃~700℃ and held for 2.5~4.5h, then cooled with the furnace at a rate of 2~5℃ / min.

5. The irregular core powder conformal pressing method according to claim 4, characterized in that, The process involves preparing the types of single raw materials required for the irregularly shaped core to be pressed, and drying all single raw materials separately. The required raw materials include potassium chloride, molybdenum disulfide powder, potassium titanate whiskers, talc, sodium bentonite, water glass, and sodium chloride.

6. The irregular core powder conformal pressing method according to claim 5, characterized in that, The steps involve weighing all individual raw materials according to a preset ratio and mixing them to obtain a mixed raw material: The preset ratio is as follows by mass fraction: potassium chloride 15.4-19.3, molybdenum disulfide powder 4.3-6.8, potassium titanate whiskers 1.3-2.7, talc powder 0.3-1.7, sodium bentonite 1.1-4.4, water glass 4.6-6.7, and the balance is sodium chloride.

7. A mold-making device, characterized in that, The method for implementing the irregular core powder conformal pressing method according to any one of claims 1 to 6 is characterized by comprising: The frame (1), powder feeding bin (2), feeding pipe (3), feeding cart (5) and quantitative feeding device (4); The powder feeding bin (2) and the quantitative feeding device (4) are both fixed to the frame (1). The two ends of the feeding pipe (3) are respectively used to connect the outlet of the powder feeding bin (2) and the inlet of the quantitative feeding device (4). The pressing mold (6) is installed on the frame (1). The feeding cart (5) receives the mixed raw materials conveyed by the quantitative feeding device (4) and sends the mixed raw materials into the pressing mold (6).

8. The mold equipment according to claim 7, characterized in that, The pressing mold (6) includes: The upper mold assembly (61) includes an upper mold head (613), an upper mold ejector rod (612), and an upper mold hydraulic cylinder (611). The upper mold ejector rod (612) is slidably mounted on the frame (1). The upper mold head (613) is fixed to the end of the upper mold ejector rod (612). The upper mold hydraulic cylinder (611) is fixedly mounted on the frame (1) and is used to control the sliding of the upper mold ejector rod (612). The lower mold assembly (62) includes at least two lower mold heads, at least two lower mold ejector rods (627), at least two lower hydraulic cylinders (626), and a lower mold fixing plate (621). The lower mold fixing plate (621) is fixed to the frame (1). At least two of the lower mold heads are slidably engaged with the lower mold fixing plate (621). At least two of the lower mold ejector rods (627) are respectively fixedly connected to the corresponding lower mold heads. At least two of the lower hydraulic cylinders (626) are respectively connected to the corresponding lower mold ejector rods (627), so that at least two of the lower mold heads can move independently, thereby realizing the function of the control system (8) to control multiple independent lower mold punches in the mold to perform differentiated position adjustment according to the three-dimensional model information. A mold temperature controller (7) is installed on the frame (1) and electrically connected to the control system (8). The upper mold head (613), the lower mold head and the lower mold fixing plate (621) are all provided with temperature control pipelines (9), and the temperature control pipelines (9) are connected to the mold temperature controller (7).

9. The mold equipment according to claim 8, characterized in that, The upper mold assembly (61) also includes: The upper mold sleeve (614) is fixedly connected to the upper mold push rod (612), and the upper mold head (613) is detachably connected to the upper mold sleeve (614).

10. The mold equipment according to claim 9, characterized in that, The lower mold assembly (62) also includes: Positioning plate (625) is installed on the frame (1). At least two lower mold push rods (627) are slidably engaged with the positioning plate (625). The lower mold head is detachably connected to the lower mold push rods (627).

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