A reusable split-insert type mortise and tenon forming die for microwave sintering

Abstract

The present application relates to a kind of reusable split mortise and tenon forming die for microwave sintering, it relates to the field of thermoforming, including the base mould made of ceramic material with dielectric loss factor less than or equal to 0.003, sleeve mould and insert, several inserts are inserted into base mould to form cavity, sleeve mould is covered with the other end of several inserts and base mould completely covers insert, non-metallic mould closing piece is arranged outside base mould and sleeve mould to make base mould and sleeve mould closely adhere;Powder is injected into the cavity of insert from sleeve mould and 30-50MPa forming pressure is applied, it is sent into microwave oven and sintered according to process curve, the present application has the advantages that a set of mould can form various mortise and tenon components by replacing insert, and split structure can also realize non-destructive demolding, and the mould can be repeatedly used.

Description

Technical Field

[0001] This invention relates to the field of thermoforming technology, and more particularly to a reusable modular tenon-and-mortise forming mold for microwave sintering. Background Technology

[0002] Traditional mortise and tenon structures come in many varieties, each differing in force direction, assembly method, and application scenarios. With the expanding applications of ceramic-based mortise and tenon components in aerospace, high-temperature structural parts, and lunar base construction, there is an urgent need for a mold capable of mass-producing reusable mortise and tenon components of various specifications.

[0003] Existing microwave sintering molds are mostly monolithic structures, suitable only for simple, regularly shaped blocks. When preparing components with tenons, mortises, or other protruding features, the cured component forms a mechanical interlock with the mold's inner wall, resulting in a high breakage rate when forcibly demolded. More importantly, the methods used for demolding—such as hammering, prying, or even damaging the mold—mean that the mold is only usable once and then scrapped, completely failing to meet the needs of mass production. To cover all types of mortise and tenon structures, mold making would be extremely labor-intensive, with very high manufacturing costs and long process conversion cycles.

[0004] Therefore, to address the above shortcomings, there is a need to provide a reusable modular mortise and tenon forming mold for microwave sintering. Summary of the Invention

[0005] (a) Technical problems to be solved The technical problem to be solved by this invention is to address the issue that a single mold cannot be compatible with multiple mortise and tenon specifications.

[0006] (II) Technical Solution To address the aforementioned technical problems, this invention provides a reusable modular mortise and tenon molding die for microwave sintering, comprising a base mold, a sleeve mold, and inserts made of ceramic material with a dielectric loss factor of less than or equal to 0.003. Several inserts are inserted into the base mold at one end to form a cavity, and the sleeve mold is fitted over the other end of several inserts, completely covering the inserts with the base mold. Non-metallic fitting components are provided outside the base mold and the sleeve mold to ensure a tight fit between the base mold and the sleeve mold. Powder is injected from the sleeve mold into the cavity of the inserts and a molding pressure of 30-50 MPa is applied. The mixture is then placed in a microwave oven and sintered according to the process curve.

[0007] As a further explanation of the present invention, preferably, both the base mold and the sleeve mold are square shells, and both the base mold and the sleeve mold have a single-sided open mounting cavity in the middle. The mounting cavity has a circular or polygonal cross-section, and several inserts are embedded in the mounting cavity.

[0008] As a further explanation of the present invention, preferably, a plurality of circular or polygonal slots are provided in the mounting cavity, and circular or polygonal bosses are fixed to both ends of the insert along its length direction. The bosses are embedded in the slots so that the insert is connected to the base mold and the sleeve mold.

[0009] As a further explanation of the present invention, preferably, the number of slots is greater than or equal to the number of inserts.

[0010] As a further explanation of the present invention, preferably, a positioning platform with a polygonal cross-section is provided in the center of the slot; a square positioning hole is provided in the boss, and the positioning platform is embedded in the positioning hole to fix the position of the insert relative to the base mold and the sleeve mold.

[0011] As a further explanation of the present invention, preferably, the positioning platform is provided with a draft angle of 1° to 3°.

[0012] As a further explanation of the present invention, preferably, the plurality of inserts are one or more of the following: straight tenon inserts, dovetail tenon inserts, wedge tenon inserts, or mortise and tenon inserts.

[0013] As a further explanation of the present invention, preferably, the mold assembly includes a connecting rod, a hook, a protruding plate, and a bolt. The hook is fixed to one end of the connecting rod along its length. Hook grooves are provided on both sides of the outer wall of the base mold, and the hook is inserted into the hook grooves. The protruding plate is fixed to the other end of the connecting rod along its length, and the bolt is threaded onto the protruding plate. Locking rods are fixed to both sides of the sleeve mold, and the bolts abut against the locking rods to push the sleeve mold toward the base mold.

[0014] As a further explanation of the present invention, preferably, the locking rod has a semi-circular cross-section, and the flat end of the locking rod abuts against the bolt.

[0015] As a further explanation of the present invention, preferably, all mold parts are made of silicon nitride ceramic material.

[0016] (III) Beneficial Effects The above-described technical solution of the present invention has the following advantages: This invention features a standardized design for the mounting slot interface, with uniform insert dimensions and variations only in the cavity contour. This allows a single mold base to accommodate multiple sets of different insert types, covering the molding requirements of various mortise and tenon components. The demolding process avoids destructive loads such as ejection forces and impact forces, resulting in zero damage to the mold base and no wear on the insert surfaces. Furthermore, operators only need to open the mold, replace the insert, and reclose the mold to switch product specifications, a process highly consistent with mature mold-changing techniques in the injection molding industry, resulting in low learning costs. This concept enables the mold to be launched to the moon under low launch load conditions in the future, and a single mold can produce hundreds of components. Even if inserts are damaged due to repeated use of the mold, only the damaged inserts need to be replaced, eliminating the need to replace the entire mold, further reducing the cost of future lunar base construction. Attached Figure Description

[0017] Figure 1 This is a diagram showing the separation state of the sleeve mold and the base mold according to the present invention; Figure 2 This is an assembly effect diagram of the inserts of the present invention; Figure 3 This is a schematic diagram of the basic model of the present invention; Figure 4 This is a schematic diagram of the connection between the insert and the base mold of the present invention; Figure 5 This is a molding effect diagram of the present invention.

[0018] In the diagram: 1. Base mold; 11. Mounting cavity; 12. Slot; 13. Positioning platform; 14. Hook groove; 2. Mold sleeve; 21. Sprue; 22. Locking rod; 3. Insert; 31. Cavity; 32. Boss; 33. Positioning hole; 34. Flow port; 4. Mold assembly; 41. Connecting rod; 42. Hook; 43. Protruding plate; 44. Bolt; 45. Slide groove. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0020] A reusable modular mortise and tenon molding die for microwave sintering, such as Figure 1 As shown, the system includes a base mold 1, a sleeve mold 2, and inserts 3. Several inserts 3 are inserted into the base mold 1 at one end to form a cavity 31. The sleeve mold 2 is fitted over the inserts 3 at the other end, completely covering the inserts 3. A non-metallic fitting 4 is provided around the base mold 1 and sleeve mold 2 to ensure a tight fit. The base mold 1, sleeve mold 2, and inserts 3 are all integrally sintered from high-purity alumina ceramic. The material has a relative permittivity factor ≤0.003 and exhibits extremely low self-heating in the 2.45GHz industrial microwave band, demonstrating excellent microwave compatibility. According to the microwave volume power density formula: In the formula: Volumetric power density; It is the angular frequency, specifically , It is a microwave frequency; It is the vacuum permittivity; The relative permittivity of the material is ≤0.003 in this invention; denoted as the root mean square value of the electric field strength.

[0021] In this invention, the ceramic blank to be sintered is such as a lunar soil simulant. The purity is between 0.1 and 0.5, and the base mold 1, sleeve mold 2, and insert 3 of this invention are made of high-purity alumina ceramic. The difference between the two is ≤0.003, which is 30 to 150 times. In the same microwave electric field, the heating power per unit volume of the billet is much higher than that of the mold. The microwave energy can be mainly deposited inside the billet, and the mold itself absorbs very little energy, which not only avoids the overheating of the substrate, but also greatly improves the energy utilization efficiency.

[0022] Combination Figure 3 , Figure 4 The base mold 1 and the sleeve mold 2 are standard square shells with uniform and standardized external dimensions, which can be adapted to the tooling station of a general microwave sintering furnace without the need for changes or adjustments based on product specifications. Both the base mold 1 and the sleeve mold 2 are open on one side, with an installation cavity 11 inside. The cross-section of the installation cavity 11 can be designed as a circle, a regular hexagon, a regular octagon, or other polygonal shapes. The inner wall surface is precision machined to form a clearance fit with the outer wall surface of the insert 3. The clearance is controlled within 0.02 to 0.05 mm to ensure smooth assembly of the insert and to avoid the insert offset and misalignment caused by excessive clearance.

[0023] Combination Figure 3 , Figure 4The bottom surface of the mounting cavity 11 has several circular or polygonal slots 12. Circular or polygonal bosses 32 are fixed to both ends of the insert 3 along its length. The bosses 32 are embedded in the slots 12 to connect the insert 3 with the base mold 1 and the sleeve mold 2. The depth of the slots 12 is set to 5-10mm, and their main function is to radially limit the insert 3, preventing it from expanding outwards during pressurization. The number of slots 12 is not less than the number of inserts 3. Taking the attached diagram as an example, if there are 10 slots 12, then 6 inserts 3 are needed if the dovetail tenon has a trapezoidal cross-section, and at least 4 inserts 3 covering the four corners. If the dovetail tenon has a polygonal cross-section, then 10 inserts 3 are needed. Each insert 3 should ideally cover a corner or flat area to reduce the processing difficulty of the insert 3, and adding inserts 3 to the flat areas facilitates demolding. A polygonal positioning platform 13 is provided in the center of the slot 12, with a demolding slope of 1°-3° to facilitate the replacement of the insert 3. A square positioning hole 33 is provided inside the boss 32. The positioning platform 13 is embedded in the positioning hole 33 to achieve circumferential positioning of the insert 3, preventing the insert 3 from rotating during the loading and pressurization process and ensuring the accuracy of the cavity contour. Preferably, after simulation optimization, the positioning platform 13 is designed with a 1.5° draft angle, which can reduce the pull-out resistance of the insert 3 by more than 70% while ensuring a circumferential positioning accuracy of ±0.01mm, thus balancing accuracy and lifespan.

[0024] Combination Figure 1 , Figure 2 The opening faces of the base mold 1 and the sleeve mold 2 are the mold closing faces. After the molds are closed, they fit tightly without any visible gaps, which can effectively prevent the powder from overflowing from the mold closing faces during the pressurization process. The top center of the sleeve mold 2 is provided with a sprue 21, and a runner 34 is provided on a certain part of the cavity that is a flat part. The sprue 21 and the runner 34 are connected and used for powder filling and the insertion of the pressurizing punch.

[0025] Combination Figure 2 , Figure 4 The insert 3 is a columnar structure, with its total length matching the depth of the mounting cavity 11. The outer wall of the insert 3 serves as a standardized reference surface, while the inner wall serves as the forming working surface. Together, they form the cavity 31. Precision machining is performed according to the contour of the target tenon and mortise component, allowing for flexible design of any tenon and mortise form, such as straight tenons, dovetail tenons, wedge tenons, and mortise and tenon joints, and adapting to different sizes. All protruding and concave features of the insert 3 are demolded along the radial splitting direction, without axial undercuts or mechanical interlocks. For example, simple straight tenon components can be split into two halves, dovetail tenons with undercuts can be split into four or six halves, and complex mortise and tenon joints can be split into eight or ten halves. Through proper splitting, after sintering, the inserts 3 can be removed one by one radially, completely releasing the mechanical interlock between the cavity 31 and the component, achieving zero-force, damage-free demolding.

[0026] Combination Figure 1 , Figure 2All mold components 4 are made of silicon nitride ceramic material, specifically including a connecting rod 41, a hook 42, a protruding plate 43, and a bolt 44. The hook 42 is fixed to one end of the connecting rod 41 along its length. Hook grooves 14 are provided on both sides of the outer wall of the base mold 1, and the hook 42 is inserted into the hook grooves 14. The protruding plate 43 is fixed to the other end of the connecting rod 41 along its length, and the direction of the protruding plate 43 is opposite to that of the hook 42, so that the connecting rod 41 can abut against the outer wall of the base mold 1 and the sleeve mold 2. The bolt 44 is threaded onto the protruding plate 43. A long strip-shaped sliding groove 45 is provided on the end face of the connecting rod 41 near the protruding plate 43. Locking rods 22 are fixed to both sides of the sleeve mold 2, and the locking rods 22 extend into the sliding grooves 45. The cross-section of the locking rod 22 is designed to be semi-circular, with the flat side facing the end of the bolt 44, which can increase the contact area with the end face of the bolt 44 and avoid stress concentration at the end of the bolt 44, causing damage to the surface of the locking rod 22. When bolt 44 is rotated, the end of bolt 44 axially pushes locking rod 22 towards base mold 1, thereby causing sleeve mold 2 to fit tightly against base mold 1, achieving mold closing and locking. Each mold set is equipped with 2 to 4 combined mold parts, symmetrically arranged on both sides of the mold to ensure uniform distribution of mold closing force and consistent contact pressure at all points on the mold closing surface. Furthermore, the mold closing and locking force can be precisely adjusted by the tightening torque of bolt 44, typically controlled within 5 to 10 N. m. This locking force range can ensure that there is no mold expansion or powder leakage under molding pressure of 30-50MPa, and can also avoid stress concentration and cracking of the base material corners due to excessive locking force.

[0027] This invention also provides a set of examples for preparing tenon-and-mortise bricks of lunar soil simulants, mainly composed of silicate minerals, glass phase, ilmenite, and oxides, with the specific schemes as follows: Specifications of base mold 1 and sleeve mold 2: 150mm (length) × 100mm (width) × 60mm (height); Inlay 3: Dovetail joint, cross-section dimensions 80mm × 30mm; Dovetail inserts 3 pairs are respectively installed into the mounting cavity 11 of the base mold 1, and the positioning boss 32 is embedded into the positioning hole of the insert 3. The mold sleeve 2 and the base mold 1 are closed by the mold closing component 4, the positioning structure is automatically centered, and the cavity is completely formed. Lunar soil simulation material is filled into the cavity through the sprue 21, and the press is controlled to apply a pressure of 30MPa and hold the pressure for 30s. Then the mold is placed in a vacuum microwave sintering furnace and sintered according to the process curve, preferably heated to 1000℃ at 8℃ / min, heated to 1550℃ at 5℃ / min, held for 20min, and then cooled to room temperature naturally with the furnace. The mold is then removed. The mold closing component 4 is removed, and the mold sleeve 2 is opened along the parting surface. Then all the inserts 3 are removed from the mounting cavity 11, and the inserts 3 are peeled off from the flat part. The component can be freely separated from the insert 3 or can be removed with slight shaking. Figure 5 As shown, the mortise and tenon joint outline is complete. After cleaning the mounting cavity 11 and checking for any residue, replace it with another set of inserts, and the next round of forming work can begin immediately.

[0028] The ratio of the power absorbed by the billet to the total incident power is: In the formula: This refers to the volume of the billet. This is the microwave input power.

[0029] As shown in the above formula, if a traditional integral mold is used to form lunar soil simulants, the mold will be large, have relatively high dielectric loss, and absorb a large amount of microwave power, resulting in low effective coupling efficiency. This will inevitably lead to a situation where the mold gets hot while the billet temperature remains low, making it difficult to reach the sintering temperature. In contrast, this invention uses a split-block 3-type architecture, where the substrate only serves a load-bearing and positioning function. The total material volume of the mold is only 1 / 3 to 1 / 5 of that of a traditional integral mold, and its weight is also low, reducing the launch payload and lowering the cost of transporting it to the moon. Furthermore, all materials used are extremely low dielectric loss materials, resulting in a very low percentage of power absorbed by the mold itself. The vast majority of the incident microwave power is absorbed by the billet, thus significantly increasing the coupling efficiency compared to traditional integral molds. In this example, the microwave coupling efficiency is 64.2%, an improvement of 41.5% compared to traditional integral molds. Product changeover time is 8 minutes, the substrate is completely reusable, and the production cost of multiple product types is significantly reduced.

[0030] In summary, this invention, through its non-destructive demolding design using separate inserts 3, possesses high versatility. Different types of mortise and tenon components can be produced simply by replacing insert 3, eliminating the need to reprocess the entire mold. Mold development costs are reduced by over 70%, and the development cycle is shortened from 2-3 weeks to 3-5 days, resulting in significant economic benefits. Furthermore, the separate insert structure significantly reduces the total material volume of the mold, and combined with the selection of materials with extremely low dielectric loss, the microwave power absorbed by the mold itself is greatly reduced. Sintering energy consumption for producing the same components is reduced by approximately 30%, and the single-furnace sintering cycle can be shortened by over 15%, aligning with the development direction of green manufacturing and low-carbon production. Moreover, the mold demolding process of this invention does not require hammering, prying, or other violent operations; insert disassembly and component removal can be completed by hand or with the aid of simple tweezers, simplifying the operation and avoiding the risk of component and mold damage during demolding. It exhibits strong process compatibility and is easy to promote and implement.

[0031] Furthermore, the standardized design of the equal-wall-thickness insert 3 can further ensure highly consistent circumferential thermal boundary conditions in the billet. Since heat conduction within the billet follows Fourier's law, and the temperature field evolution can be described by the transient heat conduction equation, it can be calculated that the maximum internal temperature difference of the equal-wall-thickness insert 3 can be reduced from over 30℃ in traditional molds to less than 2℃, improving temperature uniformity by over 90%. The uniform temperature field effectively eliminates thermal stress concentration, and the component's thermal stress cracking rate is expected to decrease from 20%–30% in traditional processes to below 1%, increasing the yield to over 98%. Simultaneously, the uniform sintering temperature ensures synchronous grain growth throughout the component, significantly improving the uniformity of mechanical properties and enhancing product quality stability. In the future, it will no longer be necessary to transport the already mature hot-pressing system from Earth to the Moon multiple times, reducing transportation, installation, and subsequent maintenance costs while ensuring the required yield is met.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reusable modular tenon-and-mortise molding die for microwave sintering, characterized in that: The system includes a base mold (1), a sleeve mold (2), and inserts (3) made of ceramic material with a dielectric loss factor of less than or equal to 0.

003. Several inserts (3) are inserted into the base mold (1) at one end to form a cavity (31). The sleeve mold (2) is fitted over the other end of the several inserts (3) and completely covers the inserts (3) with the base mold (1). Non-metallic mold fittings (4) are provided on the outside of the base mold (1) and the sleeve mold (2) to make the base mold (1) and the sleeve mold (2) fit tightly together. Powder is injected from the sleeve mold (2) into the cavity (31) of the insert (3) and a molding pressure of 30-50 MPa is applied. The material is then sent into a microwave oven and heated and sintered according to the process curve.

2. The reusable modular tenon-and-mortise forming mold for microwave sintering according to claim 1, characterized in that: Both the base mold (1) and the sleeve mold (2) are square shells. Both the base mold (1) and the sleeve mold (2) have a single-sided open mounting cavity (11) in the middle. The mounting cavity (11) has a circular or polygonal cross section, and several inserts (3) are embedded in the mounting cavity (11).

3. A reusable modular tenon-and-mortise forming mold for microwave sintering according to claim 2, characterized in that: The mounting cavity (11) has several circular or polygonal slots (12). The two ends of the insert (3) along the length direction are fixed with circular or polygonal bosses (32). The bosses (32) are embedded in the slots (12) so that the insert (3) is connected to the base mold (1) and the sleeve mold (2).

4. A reusable modular tenon-and-mortise forming mold for microwave sintering according to claim 3, characterized in that: The number of slots (12) is greater than or equal to the number of inserts (3).

5. A reusable modular tenon-and-mortise forming mold for microwave sintering according to claim 4, characterized in that: The slot (12) has a positioning platform (13) with a polygonal cross section in the middle; the boss (32) has a square positioning hole (33) in the middle, and the positioning platform (13) is embedded in the positioning hole (33) so that the position of the insert (3) relative to the base mold (1) and the sleeve mold (2) is fixed.

6. A reusable modular tenon-and-mortise forming mold for microwave sintering according to claim 5, characterized in that: The positioning table (13) has a draft angle of 1° to 3°.

7. A reusable modular tenon-and-mortise forming mold for microwave sintering according to claim 1, characterized in that: Several inlays (3) are one or more of the following: straight tenon inlay, dovetail tenon inlay, wedge tenon inlay or mortise and tenon inlay.

8. A reusable modular tenon-and-mortise forming mold for microwave sintering according to claim 1, characterized in that: The mold assembly (4) includes a connecting rod (41), a hook (42), a protruding plate (43), and a bolt (44). The hook (42) is fixed to one end of the connecting rod (41) along its length. The outer wall of the base mold (1) has hook grooves (14) on both sides. The hook (42) is inserted into the hook grooves (14). The protruding plate (43) is fixed to the other end of the connecting rod (41) along its length. The bolt (44) is threaded onto the protruding plate (43). The sleeve mold (2) has locking rods (22) fixed to both sides. The bolt (44) abuts against the locking rods (22) to push the sleeve mold (2) toward the base mold (1).

9. A reusable modular tenon-and-mortise forming mold for microwave sintering according to claim 8, characterized in that: The locking rod (22) has a semi-circular cross section, and the flat end of the locking rod (22) abuts against the bolt (44).

10. A reusable modular tenon-and-mortise forming mold for microwave sintering according to claim 9, characterized in that: All mold parts (4) are made of silicon nitride ceramic material.

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