Isostatic pressing forming die and method for ceramic long pipe

Abstract

The invention discloses an isostatic pressing forming die and method for a ceramic long pipe, and aims to overcome the defect that the straightness of a product cannot be guaranteed when the ceramic pipe which is relatively long and relatively large in length-diameter ratio is machined. The forming die comprises a hard core rod and an elastic die sleeve, the two ends of the die sleeve are connected with end covers, the core rod is connected between the two end covers, the core rod is arranged in the die sleeve, a forming die cavity is formed between the core rod and the die sleeve, and the die sleeve is sleeved with a hard porous supporting pipe. In the isostatic pressing forming process of the long ceramic tube, the geometric stability of a mold in the initial stage of isostatic pressing can be improved through the porous supporting tube additionally arranged on the outer layer, pressure is more evenly distributed in the axial direction and the radial direction of a formed body in the initial stage of densification, and guarantee is provided for good straightness and even density of the subsequent formed body.

Description

Technical Field

[0001] This invention relates to the field of ceramic product processing technology, and more specifically, to a ceramic long tube isostatic pressing mold and method. Background Technology

[0002] Currently, special ceramic tubes are widely used in many fields due to their excellent high-temperature resistance, chemical inertness, hardness, wear resistance, and electrical insulation. Traditional ceramic tube processing methods mainly include the following: 1. Forming using an extrusion molding machine. This method is suitable for rapid mass production, but it has certain requirements for powder materials, and new extrusion dies need to be replaced when the product size changes, resulting in high equipment and die costs. 2. Forming solid ceramic green bodies using a cylindrical elastic die in an isostatic press, and then machining the inner and outer diameters on a machine tool. This method is time-consuming, unsuitable for mass production, and only suitable for short tubes. For longer tubes, processing is required at both ends or even impossible. 3. Based on method 2, adding an internal mandrel to the elastic isostatic press die for forming the inner cavity of long tubes. This method can basically eliminate the need for inner diameter machining, and the mandrel provides radial and axial support when machining the outer diameter, allowing for the processing of thinner-walled products. However, when the length is long and the length-to-diameter ratio is large, the mandrel is prone to bending, which can lead to poor straightness of the formed body or even breakage of the formed body, resulting in the scrapping of both the product and the mandrel. Chinese patent application number 2011205075383 discloses an isostatic pressing mold for manufacturing ceramic tube shells, comprising an inner mold and an outer mold. The inner mold is a metal cylindrical tube fitted inside a rubber tubular outer mold, and the inner and outer molds are assembled into one piece by rubber plugs at both ends. This type of mold cannot guarantee the straightness of the product when processing ceramic tubes with long lengths and large length-to-diameter ratios. Summary of the Invention

[0003] To overcome the above shortcomings, the present invention provides an isostatic pressing mold and method for ceramic long tubes, which can achieve stable forming of ceramic long tubes and produce ceramic long tubes with good straightness.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a ceramic long tube isostatic pressing mold, comprising a rigid mandrel and an elastic mold sleeve, both ends of the mold sleeve are connected to end caps, the mandrel is connected between the two end caps, the mandrel is placed inside the mold sleeve, and a forming cavity is formed between the mandrel and the mold sleeve, and a rigid porous support tube is fitted outside the mold sleeve.

[0005] In the isostatic pressing process of ceramic long tubes, the porous support tube added to the outer layer can increase the geometric stability of the mold in the initial stage of isostatic pressing, and make the pressure more evenly distributed in the axial and radial directions of the molded body in the early stage of densification, thus ensuring good straightness and uniform density of the molded body in the subsequent process. This mold can produce special ceramic long tubes with a large length-to-diameter ratio, and the molded body has good internal cavity straightness and smooth surface. Multiple products can be batched in one operation, balancing production efficiency and product quality.

[0006] Preferably, a countersunk hole is provided on the end cap, and the end of the mandrel is inserted into the countersunk hole.

[0007] The mandrel is inserted into the countersunk hole on the end cap, which facilitates assembly and ensures the accuracy of the mandrel's position.

[0008] Preferably, the end caps and the mold sleeve are made of the same material.

[0009] The end caps and the mold sleeve are made of the same material, making the connection between the two more reliable.

[0010] As a preferred option, the mandrel material is tungsten steel or high-speed steel.

[0011] The mandrel can be made of high-speed steel or tungsten steel. For target products with an aspect ratio of more than 25 or an inner diameter of less than 8 mm, it is recommended to choose tungsten steel. In other cases, high-speed steel can be chosen. The mandrel does not shrink during the molding process, so the diameter of the mandrel is the inner diameter of the target product.

[0012] As a preferred option, the end cap and the mold sleeve are interference fit.

[0013] The interference fit connection method ensures convenient and reliable connection.

[0014] As a preferred option, the mandrel surface is polished.

[0015] The mandrel surface is polished to ensure the smoothness of the inner wall of the molded product and to ensure smooth demolding.

[0016] Preferably, the porous support tube has a wall thickness of 1-3mm.

[0017] The wall thickness of the porous support tube is controlled within a certain range to ensure its structural strength.

[0018] Preferably, a storage chamber is provided inside one end cap, and a discharge hole communicating with the storage chamber is provided on the end face of the end cap. The discharge hole is adapted to connect a lifting and moving stopper rod, one end of which blocks the discharge hole, and the other end of which extends to the outer end of the end cap.

[0019] The powder required for processing the product is loaded into the storage chamber. The powder is then poured into the molding cavity and vibrated to compact it. The end cap with the storage chamber is then installed onto the other end of the mold sleeve. First, the stopper rod is raised to disengage from the discharge hole. Then, the mold sleeve continues to be vibrated. During vibration, the powder in the storage chamber is replenished into the molding cavity through the discharge hole, ensuring the molding cavity is fully filled and compacted, thus guaranteeing the product's molding quality. Afterward, the stopper rod is moved downward and inserted into the discharge hole to block it.

[0020] A method for isostatic pressing of ceramic long tubes, using a ceramic long tube isostatic pressing mold, includes the following steps: S1, fitting a porous support tube onto the outside of the mold sleeve; S2, inserting one end of a mandrel into an end cap and connecting the end cap to one end of the mold sleeve; S3, filling the molding cavity with powder and vibrating to compact it; S4, connecting the other end cap to the other end of the mold sleeve; S5, placing the mold sleeve into a cold isostatic press for pressing; S6, demolding.

[0021] After the powder used for product molding is poured into the molding cavity, it is vibrated and compacted to ensure product quality. During the cold isostatic pressing process, the porous support tube added to the outer layer can increase the geometric stability of the mold in the early stage of isostatic pressing, and make the pressure more evenly distributed in the axial and radial directions of the molded body in the early stage of densification, thus ensuring good straightness and uniform density of the molded body in the later stage.

[0022] Preferably, in step S2, wax liquid is first applied to the outer wall of the mandrel, and after cooling, a wax layer is formed on the outer wall of the mandrel. Then, the mandrel is connected to the end cap. In step S6, the wax layer is heated to melt it before the mandrel is demolded.

[0023] The wax liquid is applied to the surface of the mandrel and forms a wax layer after cooling. After the product is cooled and pressed, the mandrel is heated to melt the wax layer before demolding. The melting of the wax layer reduces the friction between the outer wall of the mandrel and the inner wall of the product, making demolding easier.

[0024] Compared with the prior art, the beneficial effects of the present invention are: (1) The isostatic pressing mold for ceramic long tubes realizes the stable molding of ceramic long tubes. The porous support tube plays a positioning role for the mold sleeve, which provides a guarantee for the good straightness and uniform density of the product, and makes the straightness of the ceramic long tube after molding good; (2) During the process of compacting the powder in the molding cavity, the powder in the storage cavity is supplemented into the molding cavity through the discharge hole, ensuring that the powder in the molding cavity is filled and compacted, and ensuring the molding quality of the product; (3) The wax liquid is applied to the surface of the mandrel and forms a wax layer after cooling. After the product is completed by static pressing molding, the mandrel is heated so that the wax layer is heated and melted, and then demolding is performed. Since the wax layer is heated and melted, the friction between the outer wall of the mandrel and the inner wall of the product is reduced, which facilitates demolding. Attached Figure Description

[0025] Figure 1This is a cross-sectional view of the present invention.

[0026] Figure 2 This is an exploded view of the present invention.

[0027] Figure 3 These are structural diagrams of the end caps in embodiments 2, 4, and 5 of the present invention.

[0028] Figure 4 This is a structural diagram of the demolding mechanism of Embodiment 5 of the present invention.

[0029] In the diagram: 1. Mandrel, 2. Mold sleeve, 3. End cap, 4. Countersunk hole, 5. Molding cavity, 6. Perforated support tube, 7. Storage cavity, 8. Discharge hole, 9. Plug rod, 10. Drive plate, 11. Push guide groove, 12. Cover plate, 13. Push column, 14. Upper support section, 15. Inclined section, 16. Lower support section, 17. Demolding seat, 18. Top support slide, 19. Demolding piston cylinder, 20. Positioning groove, 21. Support groove, 22. Push rod, 23. Preload spring. Detailed Implementation

[0030] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings: Example 1: A ceramic long tube isostatic pressing mold (see...) Figure 1 , Figure 2 The system comprises a rigid mandrel 1 and a flexible mold sleeve 2. Both ends of the mold sleeve 2 are connected to end caps 3, which are interference-fitted with the mold sleeve 2. The mold sleeve 2 is made of rubber or PU material with a hardness of A45±5°. The inner diameter of the mold sleeve 2 can be designed as 1.25 times the outer diameter of the target product. The thickness of the mold sleeve 2 can be designed as 3-5mm. The length of the mold sleeve 2 can be designed as 1.18 times the length of the target product plus the insertion depth of the end caps 3. The end caps 3 and the mold sleeve 2 are made of the same material. The mandrel 1 is connected between the two end caps 3. A countersunk hole 4 is provided on the end cap 3, and the end of the mandrel 1 is inserted into the countersunk hole 4. The insertion connection between the mandrel 1 and the countersunk hole 4 on the end cap 3 facilitates assembly and ensures the accuracy of the mandrel 1's position. The mandrel 1 is placed inside the mold sleeve 2, forming a molding cavity 5 between the mandrel 1 and the mold sleeve 2. A rigid porous support tube 6 is fitted onto the outside of the mold sleeve 2.

[0031] The porous support tube 6 can be made of stainless steel. The inner diameter of the porous support tube 6 needs to be 1-1.5mm larger than the outer diameter of the mold sleeve 2. The wall thickness of the porous support tube 6 is 1-3mm. For products with a target product diameter of less than 30mm, a porous support tube 6 with a thickness of 1mm can be used. The length is the length of the internal forming cavity 5 after the mold is assembled.

[0032] Mandrel 1 is made of tungsten carbide or high-speed steel. The surface of mandrel 1 is polished to a surface roughness of approximately Ra 0.2-0.4. Mandrel 1 can be made of either high-speed steel or tungsten carbide. For target products with a length-to-diameter ratio greater than 25 or an inner diameter less than 8mm, tungsten carbide is recommended. In other cases, high-speed steel can be used. Mandrel 1 does not shrink during the molding process; therefore, the diameter of mandrel 1 is the inner diameter of the target product. The polishing treatment of mandrel 1 ensures the smoothness of the inner wall of the molded product and facilitates easy demolding.

[0033] A method for isostatic pressing of ceramic long tubes is used to process ceramic long tubes using an isostatic pressing mold. The plan is to form an alumina ceramic green body with an inner diameter of 4.8 mm, an outer diameter of 16 mm, and a length of 410 mm. The calculation is based on an outer diameter shrinkage rate of 0.8 and a length shrinkage rate of 1.0. The method includes the following steps: S1, fitting a porous support tube 6 onto a mold sleeve 2; the mold sleeve 2 is made of PU material with a hardness of A50°, a thickness of 3 mm, a length of 465 mm, and an inner diameter of 20 mm. The porous support tube 6 has an inner diameter of 27 mm, a thickness of 1 mm, and a length of 412 mm. A series of through holes with a diameter of 5 mm are machined on the tube to form a porous support tube 6 with multiple holes.

[0034] S2, insert one end of the mandrel 1 into the countersunk hole 4 on the end cap 3, and connect the end cap 3 to one end of the mold sleeve 2; the mandrel 1 is made of tungsten steel, with a diameter of 4.8mm, a mirror-polished surface, and a length of 435mm; the end cap 3 is embedded to a depth of 25mm and a diameter of 23mm to ensure a tight fit with the mold sleeve 2 after assembly.

[0035] S3, Powder is poured into the molding cavity 5 and compacted by vibration.

[0036] S4, connect the other end cap 3 to the other end of the mold sleeve 2; be careful to insert the other end of the mandrel 1 into the countersunk hole 4 on the finally assembled end cap 3. Use warning tape to seal the seam between the end cap 3 and the mold sleeve 2, making sure the tape does not come into contact with the porous support tube 6.

[0037] S5, insert mold sleeve 2 into a cold isostatic press for pressing; the pressure is 120 MPa.

[0038] S6, Demolding. After pressing according to the program, demold. The final molded body dimensions are: outer diameter 14.75mm, inner diameter 4.8mm, and length 410mm.

[0039] After the powder used for product molding is poured into the molding cavity, it is vibrated and compacted to ensure product quality. During the cold isostatic pressing process, the porous support tube 6 added to the outer layer can increase the geometric stability of the mold in the early stage of isostatic pressing, and make the pressure more evenly distributed in the axial and radial directions of the molded body in the early stage of densification, thus ensuring good straightness and uniform density of the molded body in the later stage.

[0040] Example 2: A ceramic long tube isostatic pressing mold (see...) Figure 3 The system comprises a rigid mandrel 1 and a flexible mold sleeve 2. Both ends of the mold sleeve 2 are connected to end caps 3, which are interference-fitted with the mold sleeve 2. The mold sleeve 2 is made of rubber or PU material with a hardness of A45±5°. The inner diameter of the mold sleeve 2 can be designed as 1.25 times the outer diameter of the target product. The thickness of the mold sleeve 2 can be designed as 3-5mm. The length of the mold sleeve 2 can be designed as 1.18 times the length of the target product plus the insertion depth of the end caps 3. The end caps 3 and the mold sleeve 2 are made of the same material. The mandrel 1 is connected between the two end caps 3. A countersunk hole 4 is provided on the end cap 3, and the end of the mandrel 1 is inserted into the countersunk hole 4. The insertion connection between the mandrel 1 and the countersunk hole 4 on the end cap 3 facilitates assembly and ensures the accuracy of the mandrel 1's position. The mandrel 1 is placed inside the mold sleeve 2, forming a molding cavity 5 between the mandrel 1 and the mold sleeve 2. A rigid porous support tube 6 is fitted onto the outside of the mold sleeve 2.

[0041] The porous support tube 6 can be made of stainless steel. The inner diameter of the porous support tube 6 needs to be 1-1.5mm larger than the outer diameter of the mold sleeve 2. The wall thickness of the porous support tube 6 is 1-3mm. For products with a target product diameter of less than 30mm, a porous support tube 6 with a thickness of 1mm can be used. The length is the length of the internal forming cavity 5 after the mold is assembled.

[0042] Mandrel 1 is made of tungsten carbide or high-speed steel. The surface of mandrel 1 is polished to a surface roughness of approximately Ra 0.2-0.4. Mandrel 1 can be made of either high-speed steel or tungsten carbide. For target products with a length-to-diameter ratio greater than 25 or an inner diameter less than 8mm, tungsten carbide is recommended. In other cases, high-speed steel can be used. Mandrel 1 does not shrink during the molding process; therefore, the diameter of mandrel 1 is the inner diameter of the target product. The polishing treatment of mandrel 1 ensures the smoothness of the inner wall of the molded product and facilitates easy demolding.

[0043] A storage chamber 7 is provided inside one end cap 3. A discharge hole 8 communicating with the storage chamber 7 is provided on the end face of the end cap 3. The discharge hole 8 is adapted to connect a lifting and moving stop rod 9. One end of the stop rod 9 blocks the discharge hole 8, and the other end of the stop rod 9 extends to the outer end of the end cap 3. A drive plate 10 that moves laterally is connected to the outer end of the end cap 3. A push guide groove 11 is provided on the drive plate 10. The outer end of the stop rod 9 is connected to a cover plate 12. The cover plate 12 is connected to a push column 13. The push column 13 is movably inserted into the push guide groove 11. The push guide groove 11 includes an upper support section 14, an inclined section 15, and a lower support section 16. A trapezoidal groove is provided on the end cap 3. The lower part of the drive plate 10 has a trapezoidal structure. The lower part of the drive plate 10 is movably inserted into the trapezoidal groove. The movement of the drive plate 10 causes the push column 13 to slide from the lower support section 16 through the inclined section 15 to the upper support section 14, thereby pushing the stop rod 9 upward, causing the lower end of the stop rod 9 to disengage from the discharge hole 8, and the discharge hole 8 to open. The drive plate 10 moves in the opposite direction, causing the lower end of the stopper rod 9 to block the discharge hole 8.

[0044] A method for isostatic pressing of ceramic long tubes is used to process ceramic long tubes using an isostatic pressing mold. The plan is to form an alumina ceramic green body with an inner diameter of 4.8 mm, an outer diameter of 16 mm, and a length of 410 mm. The calculation is based on an outer diameter shrinkage rate of 0.8 and a length shrinkage rate of 1.0. The method includes the following steps: S1, fitting a porous support tube 6 onto a mold sleeve 2; the mold sleeve 2 is made of PU material with a hardness of A50°, a thickness of 3 mm, a length of 465 mm, and an inner diameter of 20 mm. The porous support tube 6 has an inner diameter of 27 mm, a thickness of 1 mm, and a length of 412 mm. A series of through holes with a diameter of 5 mm are machined on the tube to form a porous support tube 6 with multiple holes.

[0045] S2, insert one end of the mandrel 1 into the countersunk hole 4 on the end cap 3, and connect the end cap 3 to one end of the mold sleeve 2; the mandrel 1 is made of tungsten steel, with a diameter of 4.8mm, a mirror-polished surface, and a length of 435mm; the end cap 3 is embedded to a depth of 25mm and a diameter of 23mm to ensure a tight fit with the mold sleeve 2 after assembly.

[0046] S3, Powder is poured into the molding cavity 5 and compacted by vibration.

[0047] S4, fill the storage cavity 7 of the other end cap 3 with the powder required for processing the product, and connect the other end cap 3 to the other end of the mold sleeve 2; note that the other end of the mandrel 1 should be inserted into the countersunk hole 4 on the last assembled end cap 3. Move the drive plate 10 to raise the plug rod 9 away from the discharge hole 8, and then continue to vibrate the mold sleeve 2. During the vibration, the powder in the storage cavity 7 is replenished into the molding cavity 5 through the discharge hole 8, ensuring that the powder in the molding cavity 5 is filled and vibrated, thus ensuring the molding quality of the product. Afterwards, move the drive plate 10 in the opposite direction to move the plug rod 9 downward and insert it into the discharge hole 8 to block the discharge hole 8. Use warning tape to seal the joint between the end cap 3 and the mold sleeve 2, ensuring that the tape does not come into contact with the porous support tube 6.

[0048] S5, insert mold sleeve 2 into a cold isostatic press for pressing; the pressure is 120 MPa.

[0049] S6, Demolding. After pressing according to the program, demold. The final molded body dimensions are: outer diameter 14.75mm, inner diameter 4.8mm, and length 410mm.

[0050] After the powder used for product molding is poured into the molding cavity, it is vibrated and compacted to ensure product quality. During the cold isostatic pressing process, the porous support tube 6 added to the outer layer can increase the geometric stability of the mold in the early stage of isostatic pressing, and make the pressure more evenly distributed in the axial and radial directions of the molded body in the early stage of densification, thus ensuring good straightness and uniform density of the molded body in the later stage.

[0051] Example 3: A ceramic long tube isostatic pressing mold (see Figure 1 , Figure 2 The system comprises a rigid mandrel 1 and a flexible mold sleeve 2. Both ends of the mold sleeve 2 are connected to end caps 3, which are interference-fitted with the mold sleeve 2. The mold sleeve 2 is made of rubber or PU material with a hardness of A45±5°. The inner diameter of the mold sleeve 2 can be designed as 1.25 times the outer diameter of the target product. The thickness of the mold sleeve 2 can be designed as 3-5mm. The length of the mold sleeve 2 can be designed as 1.18 times the length of the target product plus the insertion depth of the end caps 3. The end caps 3 and the mold sleeve 2 are made of the same material. The mandrel 1 is connected between the two end caps 3. A countersunk hole 4 is provided on the end cap 3, and the end of the mandrel 1 is inserted into the countersunk hole 4. The insertion connection between the mandrel 1 and the countersunk hole 4 on the end cap 3 facilitates assembly and ensures the accuracy of the mandrel 1's position. The mandrel 1 is placed inside the mold sleeve 2, forming a molding cavity 5 between the mandrel 1 and the mold sleeve 2. A rigid porous support tube 6 is fitted onto the outside of the mold sleeve 2.

[0052] The porous support tube 6 can be made of stainless steel. The inner diameter of the porous support tube 6 needs to be 1-1.5mm larger than the outer diameter of the mold sleeve 2. The wall thickness of the porous support tube 6 is 1-3mm. For products with a target product diameter of less than 30mm, a porous support tube 6 with a thickness of 1mm can be used. The length is the length of the internal forming cavity 5 after the mold is assembled.

[0053] Mandrel 1 is made of tungsten carbide or high-speed steel. The surface of mandrel 1 is polished to a surface roughness of approximately Ra 0.2-0.4. Mandrel 1 can be made of either high-speed steel or tungsten carbide. For target products with a length-to-diameter ratio greater than 25 or an inner diameter less than 8mm, tungsten carbide is recommended. In other cases, high-speed steel can be used. Mandrel 1 does not shrink during the molding process; therefore, the diameter of mandrel 1 is the inner diameter of the target product. The polishing treatment of mandrel 1 ensures the smoothness of the inner wall of the molded product and facilitates easy demolding.

[0054] A method for isostatic pressing of ceramic long tubes is used to process ceramic long tubes using an isostatic pressing mold. The plan is to form an alumina ceramic green body with an inner diameter of 4.8 mm, an outer diameter of 16 mm, and a length of 410 mm. The calculation is based on an outer diameter shrinkage rate of 0.8 and a length shrinkage rate of 1.0. The method includes the following steps: S1, fitting a porous support tube 6 onto a mold sleeve 2; the mold sleeve 2 is made of PU material with a hardness of A50°, a thickness of 3 mm, a length of 465 mm, and an inner diameter of 20 mm. The porous support tube 6 has an inner diameter of 27 mm, a thickness of 1 mm, and a length of 412 mm. A series of through holes with a diameter of 5 mm are machined on the tube to form a porous support tube 6 with multiple holes.

[0055] S2, first apply wax liquid to the outer wall of the mandrel 1, and after cooling, a wax layer is formed on the outer wall of the mandrel 1. Then connect the mandrel 1 to the end cap 3. Insert one end of the mandrel 1 into the countersunk hole 4 on the end cap 3, and connect the end cap 3 to one end of the mold sleeve 2. The mandrel 1 is made of tungsten steel, with a diameter of 4.8mm after the wax layer is applied, a mirror polished surface, and a length of 435mm. The end cap 3 is embedded to a depth of 25mm and a diameter of 23mm to ensure a tight fit with the mold sleeve 2 after assembly.

[0056] S3, Powder is poured into the molding cavity 5 and compacted by vibration.

[0057] S4, connect the other end cap 3 to the other end of the mold sleeve 2; be careful to insert the other end of the mandrel 1 into the countersunk hole 4 on the finally assembled end cap 3. Use warning tape to seal the seam between the end cap 3 and the mold sleeve 2, making sure the tape does not come into contact with the porous support tube 6.

[0058] S5, insert mold sleeve 2 into a cold isostatic press for pressing; the pressure is 120 MPa.

[0059] S6, heat the mandrel 1 to melt the wax layer, and then demold the mandrel 1. After pressing according to the program, demold the final molded body with an outer diameter of 14.75mm, an inner diameter of 4.8mm, and a length of 410mm.

[0060] After the powder used for product molding is poured into the molding cavity, it is vibrated and compacted to ensure product quality. During the cold isostatic pressing process, the porous support tube 6 added to the outer layer can increase the geometric stability of the mold in the early stage of isostatic pressing, and make the pressure more evenly distributed in the axial and radial directions of the molded body in the early stage of densification, thus ensuring good straightness and uniform density of the molded body in the later stage.

[0061] Example 4: A ceramic long tube isostatic pressing mold (see Figure 3 The system comprises a rigid mandrel 1 and a flexible mold sleeve 2. Both ends of the mold sleeve 2 are connected to end caps 3, which are interference-fitted with the mold sleeve 2. The mold sleeve 2 is made of rubber or PU material with a hardness of A45±5°. The inner diameter of the mold sleeve 2 can be designed as 1.25 times the outer diameter of the target product. The thickness of the mold sleeve 2 can be designed as 3-5mm. The length of the mold sleeve 2 can be designed as 1.18 times the length of the target product plus the insertion depth of the end caps 3. The end caps 3 and the mold sleeve 2 are made of the same material. The mandrel 1 is connected between the two end caps 3. A countersunk hole 4 is provided on the end cap 3, and the end of the mandrel 1 is inserted into the countersunk hole 4. The insertion connection between the mandrel 1 and the countersunk hole 4 on the end cap 3 facilitates assembly and ensures the accuracy of the mandrel 1's position. The mandrel 1 is placed inside the mold sleeve 2, forming a molding cavity 5 between the mandrel 1 and the mold sleeve 2. A rigid porous support tube 6 is fitted onto the outside of the mold sleeve 2.

[0062] The porous support tube 6 can be made of stainless steel. The inner diameter of the porous support tube 6 needs to be 1-1.5mm larger than the outer diameter of the mold sleeve 2. The wall thickness of the porous support tube 6 is 1-3mm. For products with a target product diameter of less than 30mm, a porous support tube 6 with a thickness of 1mm can be used. The length is the length of the internal forming cavity 5 after the mold is assembled.

[0063] Mandrel 1 is made of tungsten carbide or high-speed steel. The surface of mandrel 1 is polished to a surface roughness of approximately Ra 0.2-0.4. Mandrel 1 can be made of either high-speed steel or tungsten carbide. For target products with a length-to-diameter ratio greater than 25 or an inner diameter less than 8mm, tungsten carbide is recommended. In other cases, high-speed steel can be used. Mandrel 1 does not shrink during the molding process; therefore, the diameter of mandrel 1 is the inner diameter of the target product. The polishing treatment of mandrel 1 ensures the smoothness of the inner wall of the molded product and facilitates easy demolding.

[0064] A storage chamber 7 is provided inside one end cap 3. A discharge hole 8 communicating with the storage chamber 7 is provided on the end face of the end cap 3. The discharge hole 8 is adapted to connect a lifting and moving stop rod 9. One end of the stop rod 9 blocks the discharge hole 8, and the other end of the stop rod 9 extends to the outer end of the end cap 3. A drive plate 10 that moves laterally is connected to the outer end of the end cap 3. A push guide groove 11 is provided on the drive plate 10. The outer end of the stop rod 9 is connected to a cover plate 12. The cover plate 12 is connected to a push column 13. The push column 13 is movably inserted into the push guide groove 11. The push guide groove 11 includes an upper support section 14, an inclined section 15, and a lower support section 16. A trapezoidal groove is provided on the end cap 3. The lower part of the drive plate 10 has a trapezoidal structure. The lower part of the drive plate 10 is movably inserted into the trapezoidal groove. The movement of the drive plate 10 causes the push column 13 to slide from the lower support section 16 through the inclined section 15 to the upper support section 14, thereby pushing the stop rod 9 upward, causing the lower end of the stop rod 9 to disengage from the discharge hole 8, and the discharge hole 8 to open. The drive plate 10 moves in the opposite direction, causing the lower end of the stopper rod 9 to block the discharge hole 8.

[0065] A method for isostatic pressing of ceramic long tubes is used to process ceramic long tubes using an isostatic pressing mold. The plan is to form an alumina ceramic green body with an inner diameter of 4.8 mm, an outer diameter of 16 mm, and a length of 410 mm. The calculation is based on an outer diameter shrinkage rate of 0.8 and a length shrinkage rate of 1.0. The method includes the following steps: S1, fitting a porous support tube 6 onto a mold sleeve 2; the mold sleeve 2 is made of PU material with a hardness of A50°, a thickness of 3 mm, a length of 465 mm, and an inner diameter of 20 mm. The porous support tube 6 has an inner diameter of 27 mm, a thickness of 1 mm, and a length of 412 mm. A series of through holes with a diameter of 5 mm are machined on the tube to form a porous support tube 6 with multiple holes.

[0066] S2, first apply wax liquid to the outer wall of the mandrel 1, and after cooling, a wax layer is formed on the outer wall of the mandrel 1. Then connect the mandrel 1 to the end cap 3, insert one end of the mandrel 1 into the countersunk hole 4 on the end cap 3, and connect the end cap 3 to one end of the mold sleeve 2. The mandrel 1 is made of tungsten steel, with a diameter of 4.8mm after the wax layer is applied, a mirror polished surface, and a length of 435mm. The end cap 3 is embedded to a depth of 25mm and a diameter of 23mm to ensure a tight fit with the mold sleeve 2 after assembly.

[0067] S3, Powder is poured into the molding cavity 5 and compacted by vibration.

[0068] S4, fill the storage cavity 7 of the other end cap 3 with the powder required for processing the product, and connect the other end cap 3 to the other end of the mold sleeve 2; note that the other end of the mandrel 1 should be inserted into the countersunk hole 4 on the last assembled end cap 3. Move the drive plate 10 to raise the plug rod 9 away from the discharge hole 8, and then continue to vibrate the mold sleeve 2. During the vibration, the powder in the storage cavity 7 is replenished into the molding cavity 5 through the discharge hole 8, ensuring that the powder in the molding cavity 5 is filled and vibrated, thus ensuring the molding quality of the product. Afterwards, move the drive plate 10 in the opposite direction to move the plug rod 9 downward and insert it into the discharge hole 8 to block the discharge hole 8. Use warning tape to seal the joint between the end cap 3 and the mold sleeve 2, ensuring that the tape does not come into contact with the porous support tube 6.

[0069] S5, insert mold sleeve 2 into a cold isostatic press for pressing; the pressure is 120 MPa.

[0070] S6, heat the mandrel 1 to melt the wax layer, and then demold the mandrel 1. After pressing according to the program, demold the final molded body with an outer diameter of 14.75mm, an inner diameter of 4.8mm, and a length of 410mm.

[0071] After the powder used for product molding is poured into the molding cavity, it is vibrated and compacted to ensure product quality. During the cold isostatic pressing process, the porous support tube 6 added to the outer layer can increase the geometric stability of the mold in the early stage of isostatic pressing, and make the pressure more evenly distributed in the axial and radial directions of the molded body in the early stage of densification, thus ensuring good straightness and uniform density of the molded body in the later stage.

[0072] Example 5: A ceramic long tube isostatic pressing mold (see Figure 3 , Figure 4The system comprises a rigid mandrel 1 and a flexible mold sleeve 2. Both ends of the mold sleeve 2 are connected to end caps 3, which are interference-fitted with the mold sleeve 2. The mold sleeve 2 is made of rubber or PU material with a hardness of A45±5°. The inner diameter of the mold sleeve 2 can be designed as 1.25 times the outer diameter of the target product. The thickness of the mold sleeve 2 can be designed as 3-5mm. The length of the mold sleeve 2 can be designed as 1.18 times the length of the target product plus the insertion depth of the end caps 3. The end caps 3 and the mold sleeve 2 are made of the same material. The mandrel 1 is connected between the two end caps 3. A countersunk hole 4 is provided on the end cap 3, and the end of the mandrel 1 is inserted into the countersunk hole 4. The insertion connection between the mandrel 1 and the countersunk hole 4 on the end cap 3 facilitates assembly and ensures the accuracy of the mandrel 1's position. The mandrel 1 is placed inside the mold sleeve 2, forming a molding cavity 5 between the mandrel 1 and the mold sleeve 2. A rigid porous support tube 6 is fitted onto the outside of the mold sleeve 2.

[0073] The porous support tube 6 can be made of stainless steel. The inner diameter of the porous support tube 6 needs to be 1-1.5mm larger than the outer diameter of the mold sleeve 2. The wall thickness of the porous support tube 6 is 1-3mm. For products with a target product diameter of less than 30mm, a porous support tube 6 with a thickness of 1mm can be used. The length is the length of the internal forming cavity 5 after the mold is assembled.

[0074] Mandrel 1 is made of tungsten carbide or high-speed steel. The surface of mandrel 1 is polished to a surface roughness of approximately Ra 0.2-0.4. Mandrel 1 can be made of either high-speed steel or tungsten carbide. For target products with a length-to-diameter ratio greater than 25 or an inner diameter less than 8mm, tungsten carbide is recommended. In other cases, high-speed steel can be used. Mandrel 1 does not shrink during the molding process; therefore, the diameter of mandrel 1 is the inner diameter of the target product. The polishing treatment of mandrel 1 ensures the smoothness of the inner wall of the molded product and facilitates easy demolding.

[0075] A storage chamber 7 is provided inside one end cap 3. A discharge hole 8 communicating with the storage chamber 7 is provided on the end face of the end cap 3. The discharge hole 8 is adapted to connect a lifting and moving stop rod 9. One end of the stop rod 9 blocks the discharge hole 8, and the other end of the stop rod 9 extends to the outer end of the end cap 3. A drive plate 10 that moves laterally is connected to the outer end of the end cap 3. A push guide groove 11 is provided on the drive plate 10. The outer end of the stop rod 9 is connected to a cover plate 12. The cover plate 12 is connected to a push column 13. The push column 13 is movably inserted into the push guide groove 11. The push guide groove 11 includes an upper support section 14, an inclined section 15, and a lower support section 16. A trapezoidal groove is provided on the end cap 3. The lower part of the drive plate 10 has a trapezoidal structure. The lower part of the drive plate 10 is movably inserted into the trapezoidal groove. The movement of the drive plate 10 causes the push column 13 to slide from the lower support section 16 through the inclined section 15 to the upper support section 14, thereby pushing the stop rod 9 upward, causing the lower end of the stop rod 9 to disengage from the discharge hole 8, and the discharge hole 8 to open. The drive plate 10 moves in the opposite direction, causing the lower end of the stopper rod 9 to block the discharge hole 8.

[0076] A method for isostatic pressing of ceramic long tubes is used to process ceramic long tubes using an isostatic pressing mold. The plan is to form an alumina ceramic green body with an inner diameter of 4.8 mm, an outer diameter of 16 mm, and a length of 410 mm. The calculation is based on an outer diameter shrinkage rate of 0.8 and a length shrinkage rate of 1.0. The method includes the following steps: S1, fitting a porous support tube 6 onto a mold sleeve 2; the mold sleeve 2 is made of PU material with a hardness of A50°, a thickness of 3 mm, a length of 465 mm, and an inner diameter of 20 mm. The porous support tube 6 has an inner diameter of 27 mm, a thickness of 1 mm, and a length of 412 mm. A series of through holes with a diameter of 5 mm are machined on the tube to form a porous support tube 6 with multiple holes.

[0077] S2, first apply wax liquid to the outer wall of the mandrel 1, and after cooling, a wax layer is formed on the outer wall of the mandrel 1. Then connect the mandrel 1 to the end cap 3, insert one end of the mandrel 1 into the countersunk hole 4 on the end cap 3, and connect the end cap 3 to one end of the mold sleeve 2. The mandrel 1 is made of tungsten steel, with a diameter of 4.8mm after the wax layer is applied, a mirror polished surface, and a length of 435mm. The end cap 3 is embedded to a depth of 25mm and a diameter of 23mm to ensure a tight fit with the mold sleeve 2 after assembly.

[0078] S3, Powder is poured into the molding cavity 5 and compacted by vibration.

[0079] S4, fill the storage cavity 7 of the other end cap 3 with the powder required for processing the product, and connect the other end cap 3 to the other end of the mold sleeve 2; note that the other end of the mandrel 1 should be inserted into the countersunk hole 4 on the last assembled end cap 3. Move the drive plate 10 to raise the plug rod 9 away from the discharge hole 8, and then continue to vibrate the mold sleeve 2. During the vibration, the powder in the storage cavity 7 is replenished into the molding cavity 5 through the discharge hole 8, ensuring that the powder in the molding cavity 5 is filled and vibrated, thus ensuring the molding quality of the product. Afterwards, move the drive plate 10 in the opposite direction to move the plug rod 9 downward and insert it into the discharge hole 8 to block the discharge hole 8. Use warning tape to seal the joint between the end cap 3 and the mold sleeve 2, ensuring that the tape does not come into contact with the porous support tube 6.

[0080] S5, insert mold sleeve 2 into a cold isostatic press for pressing; the pressure is 120 MPa.

[0081] S6, heat the mandrel 1 to melt the wax layer, and then demold the mandrel 1. After pressing according to the program, demold the final molded body with an outer diameter of 14.75mm, an inner diameter of 4.8mm, and a length of 410mm.

[0082] Demolding is performed on a demolding mechanism, which includes a demolding base 17. A top support slide 18 and a demolding piston cylinder 19 are mounted on the demolding base 17. The top support slide 18 and the demolding piston cylinder 19 are arranged opposite to each other. A positioning groove 20 is provided on the demolding base 17. Support grooves 21 are provided at both ends of the positioning groove 20. The molded body is fitted and installed in the positioning groove 20. The two ends of the mandrel 1 are respectively supported in the two support grooves 21. The top support slide 18 is slidably arranged. A push rod 22 is mounted on the top support slide 18. A preload spring 23 is installed between the push rod 22 and the top support slide 18. The telescopic rod of the demolding piston cylinder 19 and the push rod 22 are respectively arranged opposite to the two ends of the mandrel 1. The demolding piston cylinder 19 extends its telescopic rod outward to push the mandrel 1 to move and demold. This process is divided into a pre-demolding stage and a complete demolding stage. During the pre-demolding stage, the telescopic rod of the demolding piston cylinder 19 reciprocates, with each extension being longer than the previous one. When the telescopic rod returns to its original position, the ejector rod 22 presses against the mandrel 1. As the telescopic rod continuously pushes the mandrel 1, it loosens. In the complete demolding stage, the sliding support slide 18 misaligns the mandrel 1, and the telescopic rod of the demolding piston cylinder 19 fully extends, pushing the mandrel 1 away from the molded body, thus completing the demolding. Demolding is convenient and reliable, and will not damage the molded body.

[0083] After the powder used for product molding is poured into the molding cavity, it is vibrated and compacted to ensure product quality. During the cold isostatic pressing process, the porous support tube 6 added to the outer layer can increase the geometric stability of the mold in the early stage of isostatic pressing, and make the pressure more evenly distributed in the axial and radial directions of the molded body in the early stage of densification, thus ensuring good straightness and uniform density of the molded body in the later stage.

[0084] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Other variations and modifications may be made without departing from the technical solutions described in the claims.

Claims

1. A ceramic long tube isostatic pressing mold, characterized in that, It includes a rigid mandrel and a flexible mold sleeve. Both ends of the mold sleeve are connected to end caps. The mandrel is connected between the two end caps and placed inside the mold sleeve. A forming cavity is formed between the mandrel and the mold sleeve. A rigid porous support tube is fitted outside the mold sleeve.

2. The isostatic pressing mold for ceramic long tubes according to claim 1, characterized in that, The end cap is provided with a countersunk hole, and the end of the mandrel is inserted into the countersunk hole for connection.

3. The isostatic pressing mold for ceramic long tubes according to claim 1, characterized in that, The end caps and the mold sleeve are made of the same material.

4. The isostatic pressing mold for ceramic long tubes according to claim 1, characterized in that, The mandrel is made of tungsten steel or high-speed steel.

5. The isostatic pressing mold for ceramic long tubes according to claim 1, characterized in that, The end cap and the mold sleeve are interference fit.

6. The isostatic pressing mold for ceramic long tubes according to claim 1, characterized in that, The mandrel surface is polished.

7. The isostatic pressing mold for ceramic long tubes according to claim 1, characterized in that, The wall thickness of the porous support tube is 1-3mm.

8. A ceramic long tube isostatic pressing mold according to any one of claims 1 to 7, characterized in that, A storage chamber is provided inside one end cap, and a discharge hole communicating with the storage chamber is provided on the end face of the end cap. The discharge hole is adapted to connect a lifting and moving stopper rod. One end of the stopper rod blocks the discharge hole, and the other end of the stopper rod extends to the outer end of the end cap.

9. A method for isostatic pressing of ceramic long tubes, characterized in that, The ceramic long tube isostatic pressing molding die according to any one of claims 1 to 8 is used for processing, including the following steps: S1, fitting the porous support tube onto the outside of the die sleeve; S2, inserting one end of the mandrel into the end cap and connecting the end cap to one end of the die sleeve; S3, filling the molding cavity with powder and vibrating to compact it; S4, connecting the other end cap to the other end of the die sleeve; S5, placing the die sleeve into a cold isostatic press for pressing; S6, demolding.

10. The isostatic pressing method for ceramic long tubes according to claim 9, characterized in that, In step S2, wax liquid is first applied to the outer wall of the mandrel. After cooling, a wax layer is formed on the outer wall of the mandrel. Then, the mandrel is connected to the end cap. In step S6, the wax layer is heated to melt it before the mandrel is demolded.

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