Long pipe type ceramic product forming machining device and machining method

Abstract

The invention discloses a long pipe ceramic product forming processing device and method, and the method comprises the steps: S1, preparing a processing device which comprises a rubber pipe, an upper cover, a lower cover, a split core rod and an integrated core rod; s2, selecting steps according to the fact that the product is an eccentric ceramic tube or a concentric ceramic tube, and if the product is the eccentric ceramic tube, entering S3; if the ceramic tube is a concentric ceramic tube, entering S7; s3, preliminarily assembling the device, and entering S4; s4, filling the periphery of the core rod in the rubber pipe with ceramic powder, and entering S5; s5, the device is completely assembled and sealed, and the step S6 is executed; and S6, the assembled device is placed in cold isostatic pressing equipment to be subjected to compression molding, and machining is completed. And S7, the integrated core rod is installed on the upper cover or the lower cover, the upper cover / the lower cover with the integrated core rod is installed at the end of the rubber pipe, and the step S4 is executed. By adopting the rubber pipe as the outer contour and adopting the detachable core rod design, efficient forming of ceramic pipes of different sizes and shapes is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing, and in particular to a molding and processing device and a processing method for long tube ceramic products. Background Art

[0002] With the continuous development of the semiconductor industry, the demand for the size of ceramic tube products has gradually increased, and the types and demands have also increased. The inner diameter of traditional tube products is completed by GC processing. For products with longer lengths, both ends are processed, resulting in cutting marks at the joints of the products. Subsequent fine finishing requires more manpower and material resources, and the processing efficiency is low.

[0003] For example, the "forming press and processing method for pressing long tubular powder" disclosed in Chinese patent literature, with application number "CN202410959652.1", includes a mold assembly, which forms a cavity; a pressing assembly connected to the mold assembly, which includes a servo hydraulic press, which performs telescopic movement along the length direction of the cavity; and a control system electrically connected to the servo hydraulic press, which can control the movement state of the servo hydraulic press.

[0004] Although the above scheme controls the upper mold to reciprocate along the inner wall of the middle mold through the servo hydraulic press, so that the length of the cavity can be accurately increased or decreased, and the length of the powder placed in the cavity can be accurately reduced, so that the powder pressing process is a controllable process, and the density change of the powder is predictable. When the powder is pressed multiple times, the compression rate of the powder is known, and the pressed state of the powder is also known, which makes the powder density change known, and the powder can still be pressed multiple times to obtain a tubular powder that meets the production requirements. However, when applied to the field of ceramic product processing, there are still problems such as unsatisfactory accuracy during deep hole processing, or difficulty in processing ceramic products with complex shapes and high dimensional accuracy. Summary of the invention

[0005] In order to overcome the challenges of size control and shape complexity in the current production process of long ceramic tubes, the present invention solves the problems of low precision and low efficiency in traditional ceramic tube processing by adopting cold isostatic pressing technology combined with a split mandrel and a rubber tube fixture, thereby achieving efficient and accurate ceramic tube forming effects and significantly improving the processing efficiency and quality of the products.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A long tube ceramic forming processing device, comprising: Rubber tube, jig outer contour, cold isostatic pressing uses liquid pressure to squeeze ceramic powder into shape; The upper and lower covers are used to install and seal the two ends of the rubber tube to prevent liquid from leaking into the fixture during cold isostatic pressing. The core rod is set in the rubber tube to form the internal contour of the ceramic tube.

[0007] The core of the long-tube ceramic forming processing device is to use the cold isostatic pressing principle to achieve uniform forming of ceramic powder. The rubber tube in the device serves as a deformable mold shell. Under the action of hydraulic pressure, it will be evenly compressed inward, thereby exerting all-round pressure on the internal ceramic powder. According to Pascal's law, the liquid pressure in a closed container is equal in all directions, which ensures that the ceramic powder is evenly stressed. The sealing design of the upper and lower covers cleverly utilizes the elastic deformation characteristics of the rubber material, and can fit tightly with the rubber tube under high pressure to effectively prevent liquid leakage. The setting of the core rod is to form the inner cavity of the ceramic tube. Its size needs to consider the sintering shrinkage rate of the ceramic material, which is usually 3-20% larger than the final product size. This scheme has significant advantages over the traditional turning method: first, it can form a complex inner cavity structure at one time, avoiding the joint problem caused by segmented processing; second, cold isostatic pressing can achieve nearly 100% of the theoretical density, greatly improving the mechanical strength and performance stability of the product; third, this method is suitable for various difficult-to-process ceramic materials, such as alumina and zirconia. In addition, those skilled in the art may further improve the pressure resistance and life of the rubber tube by improving the material and structure of the rubber tube, such as using multiple layers of composite rubber or adding fiber reinforcement.

[0008] Preferably, the rubber tube has at least one concave or convex profile to meet the molding requirements of ceramic products of different shapes. The rubber tube with irregular profile can produce uneven pressure distribution during cold isostatic pressing, thereby achieving directional compression of ceramic powder. According to the theory of elastic mechanics, when the rubber tube is subjected to external hydraulic pressure, its concave or convex part will produce stress concentration, resulting in different degrees of local deformation. This deformation difference can accurately control the density and shape of ceramic powder in a specific area. This solution can meet the market demand for ceramic products with complex shapes, such as special-shaped tubes, reducers or pipe fittings with local protrusions. In general, this solution can form complex shapes at one time, reduce subsequent machining processes; improve the dimensional accuracy and surface quality of the product; reduce material waste and production costs. Compared with the common straight rubber tube, this design significantly improves the flexibility and scope of application of the molding device. In addition, it can be considered to use smart materials to make rubber tubes, such as shape memory polymers, to achieve dynamic adjustment of the rubber tube profile through temperature or electric field control, so as to achieve switching production of products of various shapes on a set of equipment. Technical personnel in this field can combine computer-aided design and finite element analysis to optimize the concave and convex structure of the rubber tube to achieve the best pressure distribution and molding effect. Further application also provides new possibilities for the functionalization of ceramic products, such as forming sensor mounting grooves or fluid channels at specific locations.

[0009] Preferably, the mandrel is a split mandrel, which includes at least two detachably connected parts, and can flexibly adjust the total length and eccentricity of the mandrel to meet the processing requirements of eccentric ceramic tubes of different lengths. In the cold isostatic pressing process, the pressure gradient in the length direction may lead to uneven molding of long tube products. The split mandrel can effectively compensate for this pressure unevenness by adjusting the length and connection method of each part, adapt to the processing requirements of ceramic tubes of different lengths and eccentricities, and improve the versatility and flexibility of the device. The adoption of this scheme can accurately control the inner cavity shape and eccentricity of long tube products; facilitate product demoulding and reduce the risk of damage during demoulding; and realize the processing of products of various specifications by the same set of equipment, thereby reducing the equipment investment cost. Compared with the traditional one-piece mandrel, the split design significantly improves the adaptability and production efficiency of the device. The connection method between the parts of the mandrel can adopt a magnetic connection or a quick locking mechanism to improve the assembly and disassembly efficiency. In addition, by setting a temperature control system inside the mandrel, the local temperature during the molding process can be accurately controlled, further improving the product quality.

[0010] Preferably, the mandrel is an integrated mandrel, and the integrated mandrel is completely matched with the inner surface of the rubber tube. It can provide stable inner cavity molding support during cold isostatic pressing. Considering the Saint-Venant principle, when the length of the mandrel is much larger than its diameter, its deformation is mainly affected by the axial force, which ensures the stability of the inner cavity size during the molding process, and the purpose is to improve the processing accuracy and efficiency of the concentric ceramic tube. Compared with the split mandrel, the integrated design reduces the connection parts, avoids possible stress concentration and deformation, thereby improving the dimensional accuracy and surface quality of the product, can achieve higher molding pressure, improve product density and strength; reduce assembly and disassembly time, improve production efficiency; reduce the risk of deformation during processing, and improve product qualification rate. Compared with traditional mechanical processing methods, this design significantly improves the production efficiency and quality consistency of long tube concentric ceramic products. Furthermore, by designing a cooling channel inside the mandrel, the temperature during the molding process can be accurately controlled, further improving product quality. Or consider integrating sensors such as pressure sensors or temperature sensors on the surface of the mandrel to monitor key parameters in the molding process in real time, and provide data support for process optimization and quality control.

[0011] Preferably, the one-piece mandrel can be extended and retracted along its length to adapt to the molding of ceramic products of different lengths. When the length of the mandrel changes, its deflection and deformation characteristics during the cold isostatic pressing process will also change accordingly. By accurately controlling the length of the mandrel, the problem of uneven stress distribution that may occur during the molding process of products of different lengths can be compensated. In order to improve the adaptability of the device, the same set of equipment can be adapted to the processing requirements of ceramic products of different lengths, which significantly improves the versatility of the equipment and reduces the switching time between products of different specifications; it can accurately control the product length and improve dimensional accuracy; by adjusting the length of the mandrel, the molding pressure distribution of products of different lengths can be optimized to improve product quality consistency. Compared with fixed-length mandrels, this retractable design greatly improves production flexibility and equipment utilization. In addition, by integrating a force sensor in the mandrel telescopic mechanism, the axial stress distribution during the molding process can be monitored in real time, providing a basis for optimizing process parameters.

[0012] The present application also discloses a long tube ceramic forming processing method using the long tube ceramic forming processing device, comprising the following steps: S1: preparing a processing device, the device comprising a rubber tube, an upper cover, a lower cover, a split mandrel and an integrated mandrel; S2: Select a step based on whether the product is an eccentric ceramic tube or a concentric ceramic tube. If it is an eccentric ceramic tube, go to S3; if it is a concentric ceramic tube, go to S7; S3: Install the two parts of the split mandrel onto the upper cover and the lower cover respectively, and install the upper cover / lower cover at both ends of the rubber tube, and enter S4; S4: Fill ceramic powder around the core rod in the rubber tube and enter S5; S5: Install the lower cover / upper cover that is not installed to both ends of the rubber tube and seal it with sealing tape, and then proceed to S6; S6: placing the assembled device in a cold isostatic pressing device for pressing and forming, and the processing is completed; S7: Install the integrated mandrel to the upper cover or the lower cover, and install the upper cover / lower cover with the integrated mandrel on the end of the rubber tube, and proceed to S4.

[0013] This method cleverly combines the characteristics of the aforementioned devices and embodies a systematic process design idea. From the working principle, this method is based on the cold isostatic pressing principle and realizes the differentiated processing of eccentric and concentric ceramic tubes through steps S1 to S7, mainly to improve processing efficiency and product quality, while increasing production flexibility.

[0014] Steps S1 and S2 embody the modular design concept. By preparing different types of core rods, the adaptability of the same set of equipment to different products is achieved. S3 to S6 are aimed at the processing of eccentric ceramic tubes. The characteristics of the split core rod are used to solve the problem of uneven pressure distribution that may occur in the molding process of long tube products. S7 is aimed at concentric ceramic tubes. The use of an integrated core rod simplifies the processing process and improves efficiency. The flexibility of the production line is significantly improved, and the production of different types of products can be quickly switched; by accurately controlling the installation position of the core rod, the precise control of the inner cavity shape of the product is achieved; the use of sealing tape effectively prevents liquid leakage and improves the product qualification rate. Compared with traditional mechanical processing methods, this cold isostatic pressing method can complete the molding of complex inner cavities at one time, greatly reducing subsequent processing steps. In practical applications, it is possible to consider introducing automation technology, such as using a robot system to realize the automatic installation of the core rod and the precise filling of powder. In addition, it is possible to consider introducing ultrasonic vibration assistance during the cold isostatic pressing process to improve the filling density and uniformity of the powder.

[0015] Preferably, in S3, the eccentricity of the final product can be controlled by adjusting the eccentricity of the split mandrel. This method utilizes the adjustable characteristics of the split mandrel and realizes precise control of the eccentricity by changing the relative positions of the various parts of the mandrel. The eccentricity of the mandrel directly determines the eccentricity of the inner cavity of the final product. This solution can achieve sub-millimeter eccentricity control and meet high-precision requirements; different eccentricities can be switched through simple mechanical adjustment, which improves production flexibility; reduces product scrapping due to unqualified eccentricity, and improves material utilization and production efficiency. Compared with traditional mechanical processing methods, this method of cold isostatic pressing combined with an adjustable mandrel can accurately control the eccentricity in the forming stage, avoiding subsequent complex processing procedures. It can be considered to introduce precision measurement technology, such as laser interferometers or high-precision displacement sensors, to achieve real-time monitoring and automatic adjustment of the mandrel eccentricity. Combined with computer-aided design (CAD) technology, a mathematical model between eccentricity and mandrel adjustment parameters can be established to achieve fast and accurate parameter setting.

[0016] Preferably, a demoulding step is also included after S6, in which the product is smoothly demoulded by disassembling the core rod. This demoulding method utilizes the detachable characteristics of the core rod, and reduces the contact area with the molded product by disassembling the core rod, thereby reducing the friction and stress concentration during the demoulding process. When the contact area is reduced, the local stress will be reduced accordingly, which helps to avoid product damage during the demoulding process. The risk of product breakage during the demoulding process is significantly reduced, and the product qualification rate is improved; the demoulding operation is simplified, the human operation error is reduced, and the production efficiency is improved; by reducing the demoulding force, the damage to the product surface is reduced, and the product surface quality is improved. Compared with the traditional overall demoulding method, this method of disassembling the core rod in steps can better adapt to the characteristics of long tubes and complex inner cavity products.

[0017] Preferably, a demoulding step is also included after S6, in which the product is smoothly demoulded by removing the core rod. The ultrasonic mechanism can be activated during demoulding to apply micro-vibration during the demoulding process. This solution is intended to solve the difficulties that may be encountered when demoulding complex-shaped or high-precision ceramic tube products. By combining core rod removal and ultrasonic micro-vibration technology, this method can significantly reduce friction and stress concentration during the demoulding process, thereby reducing the risk of product damage and improving the demoulding success rate and efficiency. This not only increases the integrity and quality of the product, but also provides a flexible demoulding solution for different types of products.

[0018] Preferably, the rubber tube has the characteristic of adjustable inner diameter to adapt to the molding of ceramic products with different diameters.

[0019] This rubber tube with adjustable inner diameter adopts a multi-layer structure or a special material formula, which can achieve radial expansion and contraction within a certain range. In order to improve the versatility and adaptability of the molding device, so that the same set of equipment can meet the processing needs of ceramic products with different diameters, the rubber material will undergo elastic deformation under the action of external force, and through special structural design, this deformation can be made more significant and controllable in the radial direction.

[0020] This solution has the following beneficial effects: 1. By adopting rubber tube as the outer contour and detachable mandrel design, the present invention realizes efficient forming of ceramic tubes of different sizes and shapes, significantly improves production flexibility and equipment utilization, and reduces product switching time and cost.

[0021] 2. By utilizing the adjustable characteristics of the split core rod, the present invention can accurately control the inner cavity shape and eccentricity of the eccentric ceramic tube, meeting the high-precision requirements and improving the product qualification rate and material utilization efficiency.

[0022] 3. The cold isostatic pressing method combined with the detachable core rod design enables the present invention to complete the molding of complex inner cavities in one go, greatly reducing subsequent processing steps and improving production efficiency and product quality consistency.

[0023] 4. By introducing the ultrasonic mechanism, the present invention improves the uniformity of the ceramic powder when filling the powder and reduces the static friction during demoulding, thereby improving the product quality and demoulding effect and reducing the risk of product damage.

[0024] 5. The design of the rubber tube with adjustable inner diameter enables the present invention to adapt to the processing requirements of ceramic products with different diameters, optimizes the molding pressure distribution, improves the product dimensional accuracy and quality consistency, and enhances the versatility of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the device structure of Example 1 of the present invention.

[0026] Figure 2 Schematic diagram of the structure of the integrated core rod in Example 2 of the present invention.

[0027] In the figure: a rubber tube 1, an upper cover 2, a lower cover 3, a core rod 4, a split core rod 5, an integrated core rod 6, a main rod 61, and a movable rod 62. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions.

[0029] Example 1 like Figure 1As shown, this embodiment proposes a method for processing eccentric ceramic tubes using a split mandrel. The method is based on the principle of cold isostatic pressing and realizes efficient production of high-precision eccentric ceramic tubes through the processing device structure. The entire device is mainly composed of a rubber tube 1, a split mandrel 5, an upper cover 2, a lower cover 3 and a hydraulic system. The rubber tube is a deformable mold shell, and its elastic properties enable it to deform evenly under high pressure, thereby exerting all-round pressure on the internal ceramic powder. The split mandrel consists of at least two detachably connected parts, and the total length and eccentricity can be flexibly adjusted. Precision threaded connections are used between the parts of the mandrel to ensure stability and accuracy after assembly. The upper and lower end covers not only play a sealing role, but also are tightly combined with the rubber tube through a special locking mechanism to prevent leakage under high pressure. The hydraulic system is responsible for providing the high-pressure liquid required for cold isostatic pressing, and the pressure is accurately adjusted through a precision control valve. When working, the length and eccentricity of the split mandrel are first adjusted according to the specifications of the target product, and then placed in the center of the rubber tube. Then, the ceramic powder is evenly filled around the mandrel. The selection and pretreatment of the powder directly affect the performance of the final product. After filling, the rubber tube is sealed by the upper and lower end caps and connected to the hydraulic system. After the hydraulic system is started, the high-pressure liquid will squeeze the rubber tube evenly. According to Pascal's law, this pressure will be evenly transmitted to the ceramic powder in all directions. In this process, the design of the split mandrel plays a key role. Since long tube products may have a pressure gradient in the length direction during the cold isostatic pressing process, the split mandrel can effectively compensate for this pressure unevenness by adjusting the length and connection method of each part. At the same time, the eccentricity of the mandrel directly determines the eccentricity of the inner cavity of the final product. In theory, sub-millimeter eccentricity control can be achieved by precisely controlling the relative position of each part of the mandrel. This high-precision control has important applications in semiconductor equipment, optical instruments and other fields. After molding is completed, demolding is carried out by slowly releasing the pressure. The detachable nature of the split mandrel once again shows its advantages at this stage. By gradually disassembling the mandrel, the contact area with the molded product can be significantly reduced, the friction and stress concentration during demolding can be reduced, and product damage can be effectively avoided. When the contact area is reduced, the local stress will be reduced accordingly, which helps to protect the more brittle ceramic products. This method has significant advantages over traditional mechanical processing methods: first, it can form complex inner cavity structures in one go, avoiding the joint problems caused by segmented processing; second, cold isostatic pressing can achieve nearly 100% of the theoretical density, greatly improving the mechanical strength and performance stability of the product; third, this method is suitable for various difficult-to-process ceramic materials, such as alumina, zirconia, etc. Combined with computer simulation technology, the pressure distribution and time curve of cold isostatic pressing can be optimized to further improve the forming accuracy and efficiency. In terms of materials science, we can explore the use of smart materials to make core rods, such as shape memory alloys, and achieve precise adjustment of the core rod shape through temperature control.In addition, the introduction of automation technology, such as the use of robotic systems to achieve automatic installation of core rods and precise filling of powder, can further improve production efficiency and consistency. Combined with computer vision technology, real-time monitoring and quality inspection of the assembly process can be achieved. In the demolding process, ultrasonic auxiliary technology can be considered to reduce static friction through micro-vibration and further improve the demolding effect.

[0030] In actual operation, the process of machining eccentric ceramic tubes with a split mandrel needs to strictly follow the following steps: First, according to the specifications of the target product, select an appropriate split mandrel assembly. Usually, the mandrel assembly includes at least two detachably connected parts, and the diameter and length of each part need to be accurately calculated. Considering the shrinkage rate of ceramic materials during sintering (usually between 10% and 20%), the size of the mandrel should be slightly larger than the final product size. For example, for a product with a target inner diameter of 50mm, assuming a shrinkage rate of 15%, the mandrel diameter should be designed to be approximately 58.8mm. Next, use precision measuring tools (such as a micrometer or a three-dimensional coordinate measuring machine) to check the dimensional accuracy of each part of the mandrel to ensure that the error is controlled within ±0.01mm. Then, adjust the relative position of each part of the mandrel according to the required eccentricity. This step can use a precision positioning device such as a fine-tuning slide or an angle adjuster, and the accuracy should reach 0.1 degrees or 0.01mm. After the adjustment is completed, use a torque wrench to tighten the various parts of the mandrel. The torque value should be accurately controlled according to the material properties and thread specifications, usually within the range of 20-30 N·m.

[0031] After the mandrel 4 is prepared, the next step is to select a suitable rubber tube. The inner diameter of the rubber tube should be slightly larger than the maximum outer diameter of the mandrel, and a gap of 0.5-1mm is usually reserved for easy installation and demoulding. The rubber material should be high-pressure resistant and elastic, such as natural rubber or fluororubber, and its hardness is usually between 60-70 Shore A. Before installing the rubber tube, it is necessary to carefully check whether there are scratches or defects on its surface, because these tiny defects may cause the rubber tube to rupture under high pressure. During installation, a small amount of silicone oil can be used for lubrication to reduce friction and prevent damage to the rubber tube.

[0032] Next is the preparation and filling of ceramic powder. The selection and pretreatment of powder directly affect the performance of the final product. High-purity ceramic powder with a particle size of 0.1-10μm, such as α-Al2O3 or Y-TZP, is usually used. To improve the fluidity and uniformity of the powder, 1-3wt% of organic binder (such as polyvinyl alcohol) and 0.5-1wt% of dispersant (such as ammonium polyacrylate) can be added. The powder should be ball-milled to break up agglomerates and improve uniformity. When filling, the vibration-assisted filling method is used to control the vibration frequency between 50-100Hz, which can significantly increase the filling density. During the filling process, care should be taken to keep the center position of the core rod, and a temporary support device can be used to fix the core rod.

[0033] After filling, install the upper and lower end caps. The seal between the end cap and the rubber tube is very important. Usually, an O-ring is used for sealing. The oil-resistant and pressure-resistant fluororubber material is selected with a hardness between 75-85 Shore A. During installation, pressure should be applied evenly to ensure that the sealing ring is not twisted or damaged. The connection between the end cap and the rubber tube can be threaded. The thread should be finely processed with a surface roughness Ra not exceeding 0.8μm to ensure the sealing effect under high pressure.

[0034] After assembly, the entire device is connected to the hydraulic system. The hydraulic system should be able to provide stable high pressure, usually 200-300MPa. The pressure should be applied slowly and evenly, with a typical pressurization rate of 10-20MPa / min. During the pressurization process, the pressure change curve needs to be closely monitored. If there is an abnormal fluctuation, it may mean that the rubber tube is leaking or deforming. The pressure holding time depends on the product size and the required density, and is generally between 5-15 minutes. When releasing the pressure, it also needs to be done slowly, with a rate controlled at 15-25MPa / min to avoid cracking of the product due to rapid decompression.

[0035] Finally, demoulding is performed. First, slowly remove the upper and lower end caps, taking care not to apply excessive stress to the formed ceramic body. Then, gradually disassemble the split mandrel starting from one end. This process should be very slow and careful, removing only a small section at a time to minimize the contact area with the body. If severe adhesion is encountered, consider using low-frequency (20-40kHz), low-power (50-100W) ultrasonic assisted demoulding. The micro-vibration of ultrasonic waves can effectively reduce static friction. During the demoulding process, the body should always be kept in a supported state to avoid deformation or damage due to its own weight.

[0036] In this embodiment, the following directions can be considered in terms of technical optimization: First, introduce an intelligent control system to automatically adjust the pressure curve by real-time monitoring of parameters such as pressure and displacement to achieve more precise molding control. Second, explore the application of new materials in the production of core rods, such as using carbon fiber reinforced composite materials, which can reduce weight while ensuring strength and facilitate operation.

[0037] In summary, in practical applications, this embodiment is more suitable for the production of high-precision, complex-shaped ceramic pipes, such as insulating components in semiconductor equipment, support structures for precision optical devices, etc. By precisely controlling the eccentricity and the shape of the inner cavity, ceramic tubes with specific functions can be designed, such as special inner cavity structure ceramic tubes for acoustic filters, or high-efficiency heat dissipation ceramic tubes for thermal management. In addition, this method also provides the possibility of developing new composite ceramic materials. For example, by adding powders of different components in layers during the filling step, the one-piece molding of gradient functional ceramics can be achieved, which has broad application prospects in the fields of aerospace and energy.

[0038] Example 2 like Figure 2As shown, this embodiment proposes a method for processing concentric ceramic tubes using an integrated mandrel, which is based on the principle of cold isostatic pressing and realizes efficient production of high-quality concentric ceramic tubes through a carefully designed device structure. The entire device is mainly composed of a rubber tube, an integrated retractable mandrel, upper and lower end covers, and a hydraulic system. The rubber tube serves as a flexible mold shell, and its high elasticity enables it to deform evenly under high pressure, thereby exerting all-round pressure on the internal ceramic powder. The integrated retractable mandrel 6 includes a main rod 61 and a movable rod 62, which adopts a precision mechanical structure design and can be continuously adjusted in the length direction. The telescopic mechanism of the mandrel adopts a precision ball screw drive, coupled with a high-precision stepper motor drive, to achieve micron-level length adjustment. The surface of the mandrel adopts a special polishing treatment, and the surface roughness Ra is controlled within 0.2μm to ensure the smoothness of the inner wall of the molded product. The upper and lower end covers not only play a sealing role, but also form a precisely centered overall structure with the rubber tube and the mandrel through a special locking mechanism to prevent leakage and deformation under high pressure. The hydraulic system is responsible for providing the high-pressure liquid required for cold isostatic pressing, and the pressure is precisely adjusted through the precision control valve, with a pressure control accuracy of ±0.1MPa. When working, the length of the one-piece mandrel is first adjusted according to the specifications of the target product, and then it is accurately positioned in the center of the rubber tube. The centering process of the mandrel uses laser centering technology to ensure that the coaxiality error is controlled within 0.01mm. Then the ceramic powder is evenly filled around the mandrel. The selection and pretreatment of the powder directly affect the performance of the final product. After the filling is completed, the rubber tube is sealed by the upper and lower end caps and connected to the hydraulic system. After starting the hydraulic system, the high-pressure liquid will squeeze the rubber tube evenly. According to Pascal's law, this pressure will be evenly transmitted to the ceramic powder in all directions. In this process, the design of the one-piece retractable mandrel plays a key role. Since long tube products may have a pressure gradient in the length direction during the cold isostatic pressing process, the retractable mandrel can effectively compensate for this pressure unevenness by accurately adjusting the length. In theory, by precisely controlling the mandrel length, sub-millimeter product length control and inner diameter consistency can be achieved. This high-precision control has important applications in the fields of precision instruments, medical equipment, etc. After molding is completed, demolding is carried out by slowly releasing the pressure. The design of the one-piece retractable mandrel once again shows its advantages at this stage. By fine-tuning the length of the mandrel, the contact area with the molded product can be reduced, the friction and stress concentration during the demolding process can be reduced, and product damage can be effectively avoided. When the contact area is reduced, the local stress will be reduced accordingly, which helps to protect ceramic products with higher brittleness. This method has significant advantages over traditional mechanical processing methods: first, it can form concentric ceramic tubes of uniform length at one time, avoiding the joint problem caused by segmented processing; second, cold isostatic pressing can achieve nearly 100% of the theoretical density, greatly improving the mechanical strength and performance stability of the product; third, this method is suitable for various difficult-to-process ceramic materials, such as alumina, silicon nitride, etc.

[0039] In actual operation, the process of machining concentric ceramic tubes with an integrated retractable mandrel requires strict adherence to the following steps: First, adjust the length of the integrated retractable mandrel according to the specifications of the target product. This step is usually achieved using a precision control system such as a PLC or industrial computer, with a stepper motor driving a ball screw. The adjustment accuracy can reach 0.01mm. Considering the shrinkage rate of ceramic materials during sintering (usually between 10% and 20%), the length of the mandrel should be slightly longer than the final product length. For example, for a product with a target length of 500mm, assuming a shrinkage rate of 15%, the mandrel length should be set to approximately 588mm. After the adjustment is completed, the mandrel length is verified using a laser interferometer to ensure that the error is controlled within ±0.05mm. Next, the diameter uniformity of the mandrel is checked using a precision measuring tool (such as a three-dimensional coordinate measuring machine) to ensure that the diameter variation along the length direction does not exceed 0.02mm. Then, the mandrel is mounted on a positioning device, which usually uses a V-block and a precision angle adjuster to achieve a 0.001 degree inclination adjustment. Use a laser alignment instrument to ensure the coaxiality of the core rod and the rubber tube. The error should be controlled within 0.01mm.

[0040] After the mandrel is prepared, the next step is to choose a suitable rubber tube. The inner diameter of the rubber tube should be slightly larger than the maximum outer diameter of the mandrel, and a gap of 0.5-1mm is usually reserved for easy installation and demoulding. The rubber material should be high-pressure resistant and elastic, such as nitrile rubber or fluororubber, and its hardness is usually between 65-75 Shore A. Before installing the rubber tube, it is necessary to use a precision internal diameter gauge to measure the uniformity of its inner diameter to ensure that the inner diameter variation along the length does not exceed 0.1mm. During installation, a vacuum adsorption device can be used to assist in ensuring that the rubber tube is evenly sleeved on the mandrel to avoid local stress concentration.

[0041] Next is the preparation and filling of ceramic powder. The selection and pretreatment of powder directly affect the performance of the final product. High-purity ceramic powder with a particle size of 0.1-5μm is usually used, such as high-purity α-Al2O3 (purity ≥99.99%). In order to improve the fluidity and uniformity of the powder, 2-4wt% of organic binder (such as polyvinyl alcohol) and 0.5-1.5wt% of dispersant (such as ammonium polyacrylate) can be added. The powder should be spray-dried to control the sphericity of the particles, and the sphericity coefficient is usually required to be greater than 0.9. When filling, the vibration-assisted filling method is used to control the vibration frequency between 60-120Hz and the amplitude between 0.1-0.5mm, which can significantly increase the filling density. During the filling process, a vacuum degassing device should be used to minimize the bubbles in the powder, and the porosity is usually required to be less than 0.5%.

[0042] After filling, install the upper and lower end caps. The seal between the end cap and the rubber tube is very important. Usually, double O-ring seals are used. The oil-resistant and pressure-resistant fluororubber material is selected with a hardness between 80-90 Shore A. During installation, a torque wrench should be used to apply pressure evenly. The torque value is usually between 30-40 N·m to ensure that the sealing ring is not twisted or damaged. The connection between the end cap and the rubber tube can be connected with a hydraulic quick locking device, which can be locked within 10 seconds to improve production efficiency.

[0043] After assembly, connect the entire device to the hydraulic system. The hydraulic system should be able to provide stable high pressure, usually 250-350MPa. The pressure should be applied slowly and evenly, with a typical pressurization rate of 15-25MPa / min. During the pressurization process, a high-precision pressure sensor (accuracy ≤0.1%FS) is required to monitor the pressure change curve in real time. If abnormal fluctuations occur, the system should automatically stop pressurization and alarm. The pressure holding time depends on the product size and the required density, generally between 10-20 minutes. The pressure should also be released slowly, with a rate controlled at 20-30MPa / min to avoid cracking of the product due to rapid decompression.

[0044] Demolding is one of the most critical steps in the whole process. First, slowly remove the upper and lower end caps, taking care not to apply excessive stress to the formed ceramic body. Then, slowly shrink the length of the core rod by 0.1-0.2mm each time through a precision control system, while monitoring the change in demoulding force. If the demoulding force suddenly increases, the shrinkage should be stopped immediately and the core rod should be slightly extended. This process should be very slow and careful, and the entire demoulding process may take 30-60 minutes. If you encounter severe adhesion, you can consider using low-frequency (30-50kHz), low-power (100-200W) ultrasonic assisted demoulding. The micro-vibration of ultrasonic waves can effectively reduce static friction. During the demoulding process, a flexible support device (such as an air cushion) should be used to support the body throughout the process to avoid deformation or damage due to its own weight.

[0045] In practical applications, this method is particularly suitable for producing high-precision, high-length-diameter-ratio ceramic pipes, such as support structures for precision optical devices, pipes for high-temperature heat exchangers, etc. By precisely controlling the inner diameter and length, ceramic tubes with specific functions can be designed, such as microchannel ceramic tubes for precision flow control, or high thermal conductivity ceramic tubes for electronic packaging.

Claims

1. A long tube ceramic product forming and processing device, characterized in that: include: Rubber tube, jig outer contour, cold isostatic pressing uses liquid pressure to squeeze ceramic powder into shape; The upper and lower covers are used to install and seal the two ends of the rubber tube to prevent liquid from leaking into the fixture during cold isostatic pressing. The core rod is set in the rubber tube to form the internal contour of the ceramic tube.

2. The device according to claim 1, characterized in that The rubber tube has at least one concave or convex profile to meet the molding requirements of ceramic products of different shapes.

3. The device according to claim 1 or 2, characterized in that: The core rod is a split core rod, and the split core rod includes at least two detachably connected parts to meet the processing requirements of eccentric ceramic tubes of different lengths.

4. The device according to claim 1 or 2, characterized in that: The core rod is an integrated core rod, and the integrated core rod is completely matched with the inner surface of the rubber tube.

5. The device according to claim 4, characterized in that The one-piece core rod can be extended and retracted along its length direction to adapt to the molding of ceramic products of different lengths.

6. The device according to claim 1, characterized in that It also includes an ultrasonic mechanism, including: an ultrasonic generator and a transducer electrically connected to the ultrasonic generator, wherein the transducer converts a high-frequency electrical signal into mechanical vibration; a waveguide rod is provided on the transducer, and a vibration head is provided at the end of the waveguide rod, which can contact the rubber tube or the core rod; wherein the ultrasonic mechanism can be selectively started when filling ceramic powder and during demolding operation.

7. A method for forming a long tube ceramic product, using the device according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: preparing a processing device, the device comprising a rubber tube, an upper cover, a lower cover, a split mandrel and an integrated mandrel; S2: Select a step based on whether the product is an eccentric ceramic tube or a concentric ceramic tube. If it is an eccentric ceramic tube, go to S3; if it is a concentric ceramic tube, go to S7; S3: Install the two parts of the split mandrel onto the upper cover and the lower cover respectively, and install the upper cover / lower cover at both ends of the rubber tube, and enter S4; S4: Fill ceramic powder around the core rod in the rubber tube and enter S5; S5: Install the lower cover / upper cover that is not installed to both ends of the rubber tube and seal it with sealing tape, and then proceed to S6; S6: placing the assembled device in a cold isostatic pressing device for pressing and forming, and the processing is completed; S7: Install the integrated mandrel to the upper cover or the lower cover, and install the upper cover / lower cover with the integrated mandrel on the end of the rubber tube, and proceed to S4.

8. The processing method according to claim 7, characterized in that: In S3, the eccentricity of the final product can be controlled by adjusting the eccentricity of the split mandrel.

9. The processing method according to claim 7, characterized in that: It also includes a demoulding step after S6, in which the product is smoothly demoulded by removing the core rod. The ultrasonic mechanism can be activated during demoulding to apply micro-vibration during the demoulding process.

10. The method according to claim 7, characterized in that The rubber tube has the characteristic of adjustable inner diameter to adapt to the molding of ceramic products with different diameters.

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