CN106217730A - A kind of polytetrafluoroethylproducts products near-net-shape method and mould - Google Patents

Abstract

The invention discloses a polytetrafluoroethylene product near-net shape method and a mold. In this method, the raw material is formed in the forming hole section of the die sleeve through the opposite extrusion of the big end and the small end pressure head, that is, through the opposite extrusion of the big end and the small end pressure head, the material originally filled in the filler hole section is formed. The raw material in the forming hole is extruded into the forming hole section, and is pressed together with the raw material originally in the forming hole section to form a blank product, and in this process, the stepped hole wall surface of the forming hole section and the large end pressure head The large end of the product is directly produced during the pressing process, thereby avoiding material waste and energy loss caused by machining on the bar blank. Therefore, the near-net shape method in the present invention has the advantages of reducing raw material loss, The advantages of improving production efficiency and product quality.

Description

A near-net-shaping method and mold for polytetrafluoroethylene products

technical field

The invention relates to a near-net-shaping method and mold for polytetrafluoroethylene products.

Background technique

At present, in the manufacture of PTFE molded products of rotary bodies at home and abroad, the molding method of overturning pressure and pressure die forging is usually used, especially in the manufacture of PTFE nozzles, which is widely used. There are mainly three types of existing PTFE nozzles, namely:

As shown in Figure 1, the first type of PTFE nozzle includes a casing with a small left and a large right, and the transition between the large diameter section 101 and the small diameter section 103 of the casing is through a tapering section 102 that gradually tapers from right to left , the outer peripheral surface and the inner wall surface of the variable diameter section 102 are both smooth curved surfaces;

As shown in Figure 2, the second polytetrafluoroethylene nozzle includes a sleeve body with a small left and a large right, and the large-diameter section 201 of the right section of the sleeve body is a flared shape that gradually expands outward from left to right, and the left section of the sleeve body The small-diameter section 202 is a bell-mouth shape that gradually opens from right to left to the left. The large-diameter section 201 and the small-diameter section 202 of the casing are transitioned through a throat 203 that is small on the left and large on the right. The inner wall and outer peripheral surface of the throat 203 are smooth surfaces;

As shown in Figure 3, the third polytetrafluoroethylene spout comprises a sleeve body with a large right side and a small left side, the small diameter section 302 of the right section of the sleeve body and the large diameter section 301 of the left section are straight cylinder sections, and the large diameter section 301 and The small-diameter sections 302 transition through the variable-diameter section 303 that expands gradually to the left freely, and the inner wall surface and the outer peripheral surface of the variable-diameter section 303 are both conical surfaces.

The production process of the PTFE spout is: mixing materials - molding - sintering - cutting processing - cleaning and packaging, among which the molding, sintering and cutting processes are more important. The mold used in compression molding is composed of a mold sleeve, a mandrel and two indenters. The inner wall of the mold sleeve is an inner cylindrical surface, and the two indenters move along the axial direction and are assembled in the middle of the mold sleeve. The cavity is a forming cavity for molding raw materials, and the opposite faces of the two indenters are planar forming end faces. The molding process is a double-sided pressing forming method, which includes nine process steps. The pressed product is a hollow cylindrical PTFE molded rotary blank with a weight of 6.3kg. The specific molding process is as follows: loading (20 minutes) , the pressure is raised from 0kN to 400kN at a constant speed for 5 minutes, kept for 20 minutes, released to 0kN at a constant speed after 5 minutes, turned over 180° (about 20 minutes), the pressure is raised from 0kN to 400kN at a constant speed for 5 minutes, kept for 20 minutes, and kept at a constant speed for 5 minutes The pressure is released to 0kN, and demoulding (8 minutes) is completed, and the total time is 2h8min; then sintering and cutting are carried out. This forming process not only consumes a lot of raw materials, but also has low efficiency in product forming and cutting. In addition, in the compression molding stage, the method of extrusion molding from both ends of the blank will cause the problem of structural damage in the middle of the blank, so that after sintering and cutting, the tapered sleeve section of the finished PTFE product There will be problems of insufficient strength and lower product quality.

Contents of the invention

The purpose of the present invention is to provide a near-net shape method for polytetrafluoroethylene products that reduces the loss of raw materials. At the same time, the present invention also provides a polytetrafluoroethylene product forming method that is specially used to implement the near-net shape method for polytetrafluoroethylene products. mold.

In order to achieve the above object, the technical scheme of the near-net shape method of polytetrafluoroethylene products in the present invention is as follows:

A near-net shape method for polytetrafluoroethylene products, comprising the following steps:

Step 1: Fill the raw material in the mold sleeve. The inner hole of the mold sleeve has a coaxially connected forming hole section and a filling hole section. The forming hole section is a stepped hole, and the filling hole section is a straight hole. The raw material is filled with the filling hole section and The forming hole section, and the small end indenter at the small hole end of the forming hole section and the large end indenter at the small hole end of the forming hole section are provided at both ends of the mold sleeve, and the compression end of the large end indenter is provided with The large-end truncated cone is coaxially spaced from the inner wall of the mold casing, and the large-end pressure head and/or the small-end pressure head are dynamic pressure heads that can seal and slide in the inner hole of the mold casing;

Step 2: Press the dynamic indenter so that the compression end of the big-end indenter and the compression end of the small-end indenter move relative to each other in the mold sleeve until the large-end indenter reaches the large port of the forming hole section, and the small-end indenter The end pressure head reaches the small port of the forming hole section, and the raw material in the filling hole section is completely pressed into the forming hole section, so that the raw material is extruded into a rough product in the forming hole section by the big end and small end pressure head.

In step one, one of the large end pressure head and the small end pressure head is a dynamic pressure head, and the other is a constant pressure head in the corresponding port of the forming hole section; in step two, by moving the dynamic pressure head closer to the fixed pressure head Pressing in the direction of the indenter makes the big end and small end indenter move relative to each other.

The technical scheme of polytetrafluoroethylene product near-net shape mold among the present invention is as follows:

A mold dedicated to implementing the near-net shape method of PTFE products, including a mold sleeve for containing raw materials, the inner hole of the mold sleeve has a coaxially connected forming hole section and a filling hole section, the forming hole section is a stepped hole, and the filler The hole section is a straight hole; it also includes the small end indenter used to compress the raw material at the small hole end of the self-forming hole section and the large end indenter used to compress the raw material at the large hole end of the self-forming hole section. And/or the small end pressure head is a dynamic pressure head that can seal and slide in the inner hole of the die sleeve, and the big end and the small end pressure head both have a compression end for compressing the raw material, and the compression of the large end pressure head The end is protrudingly provided with a large end cone for coaxial spaced insertion in the inner hole of the die sleeve.

The filling hole section is at one end of the forming hole section, and one of the big end pressure head and the small end pressure head is a dynamic pressure head for sealing and sliding from the filling hole section to the corresponding port of the forming hole section, and the other is for maintaining Constant head in the corresponding port of the bore section.

The filling hole section is located at the big end of the forming hole section, the big end pressure head is a dynamic pressure head capable of sealing and sliding in the filling hole section, and the small end pressure head is a constant pressure head.

The filling hole section is located at the small end of the forming hole section, the pressure head at the small end is a dynamic pressure head that can seal and slide in the filling hole section, and the pressure head at the big end is a constant pressure head.

A small-end cone is protruded from the pressing end of the small-end pressure head and is used for coaxially spaced inserting in the inner hole of the die sleeve.

It also includes a core rod coaxially installed in the die sleeve, and coaxially arranged guide holes for the core rod to guide and seal in the axial direction are arranged on the big end and the small end pressure head.

The core rod is formed by sequentially butt jointing of more than two sub-rod bodies from top to bottom.

The mold casing includes more than two coaxial butt joint sleeves, the forming hole section is located in one of the sleeves, and the filling hole section is formed by combining the inner holes of the other sleeves.

In the present invention, the raw material is formed in the forming hole section of the die sleeve through the opposite extrusion of the big end and the small end pressure head, that is, through the opposite extrusion of the big end and the small end pressure head, the original filling hole section is filled. The raw material in the forming hole is extruded into the forming hole section, and is pressed together with the raw material originally in the forming hole section to form a blank product, and in this process, the stepped hole wall surface of the forming hole section and the large pressure head The large end of the product is directly produced in the pressing process through the cooperation of the end cone and the frustum, thereby avoiding the material waste and energy loss caused by machining on the bar blank. Therefore, the near-net shape method in the present invention has the advantages of reducing raw material loss, The advantages of improving production efficiency and product quality.

Description of drawings

Fig. 1 is the structural representation of the first polytetrafluoroethylene product in the prior art;

Fig. 2 is the structural representation of the second polytetrafluoroethylene product in the prior art;

Fig. 3 is the structural representation of the third polytetrafluoroethylene product in the prior art;

Fig. 4 is the structural representation of mold embodiment 1 of the present invention;

Fig. 5 is a schematic diagram of product sampling points in an embodiment of the near-net shape method corresponding to the mold in Fig. 4;

Figure 6 is a comparison of the density of the product in Figure 5 and the traditional product at the sampling point (the horizontal axis represents the sampling point, and the vertical axis represents the density);

Figure 7 is a comparison diagram of the tensile strength of the product in Figure 5 and the traditional product at the sampling point (the horizontal axis represents the sampling point, and the vertical axis represents the tensile strength);

Figure 8 is a comparison of the breakdown strength of the product in Figure 5 and the traditional product at the sampling point (the horizontal axis represents the sampling point, and the vertical axis represents the breakdown strength);

Fig. 9 is the structural representation of mold embodiment 2 of the present invention;

Fig. 10 is a schematic structural view of the mold embodiment 3 of the present invention.

detailed description

Embodiment 1 of the near-net shape mold for polytetrafluoroethylene products in the present invention: the mold is mainly suitable for preparing the first polytetrafluoroethylene products, as shown in Figure 4, the mold is mainly composed of die sleeve, small end pressure head 4 , Big-end indenter 1 and core rod.

The mold casing is composed of an upper sleeve 9 , a middle sleeve 7 and a lower sleeve 3 coaxially butted from top to bottom. In the upper sleeve 9, the middle sleeve 7, and the lower sleeve 3, an annular lower butt joint is provided on the outer circumference of the lower end of the two adjacent butt ends, and an annular lower butt joint is provided on the inner wall of the upper end. Insert the upper butt joint to cooperate with the socket of the upper butt joint and the lower butt joint to realize the detachable butt joint of the upper sleeve 9, the middle sleeve 7 and the lower sleeve 3 in the axial direction. The outer circumferences of the upper sleeve 9 , the middle sleeve 7 and the lower sleeve 3 are all welded and fixed with handles 11 arranged symmetrically on opposite sides thereof. The lower sleeve 3 is the end sleeve at the bottom of each sleeve, and the inner diameters of the remaining sleeves are equal to the inner diameter of the large end of the lower sleeve 3, and the inner hole of the lower sleeve 3 is complementary to the shape of the blank. The forming hole section is a stepped hole with a large upper part and a smaller lower part. The transition between the small hole section and the large hole section of the stepped hole is through a tapered hole section whose diameter gradually decreases from top to bottom. The hole wall surface of the tapered hole section It is an arc-shaped wall surface protruding inward, the tapered hole section and the small hole section are all in the lower sleeve 3, and the tapered hole section is in the middle of the lower sleeve 3, and the part of the lower sleeve 3 above the tapered hole section is The lower part of the large hole segment. The forming hole section is composed of a large-end indenter accommodation section, a forming section, and a small-end indenter accommodation section arranged sequentially from top to bottom, wherein the large-end indenter accommodation section is used to accommodate the large-end indenter 1 and the small-end indenter The accommodating section is used for accommodating the small end indenter 4, and the hole wall surface of the forming section is used for matching with the outer peripheral surface of the rough product 2. The inner holes of the middle sleeve 7 and the lower sleeve 3 are combined to form a filling hole section, which is a straight hole with the same diameter as the large hole section of the forming hole section. The material outside the forming hole section is equivalent to containing the material to be pressed into the forming hole section.

The core rod is formed by docking the guide head 10, the upper sub-rod body 8, the middle sub-rod body 6 and the lower sub-rod body 5 sequentially from top to bottom. Two adjacent opposite ends of the guide head 10, the upper sub-rod body 8, the middle sub-rod body 6 and the lower sub-rod body 5 are respectively coaxially provided with a shaft-end plug at the upper end and a shaft-end jack at the lower end, and the shaft-end plug The threaded connection is in the socket of the shaft end to realize the detachable and fixed connection between the rod joints. The rod length of last sub-rod body 8 equals the length of upper sleeve 9, the rod length of middle sub-rod body 6 equals the length of middle sleeve 7, and the rod length of lower sub-rod body 5 equals the length of lower sleeve 3. The core rod is coaxially installed in the center of the mold sleeve, and the core rod is used to provide positioning and guidance for the small end pressure head 4, the large end pressure head 1 and the pressure head of the press.

The small end indenter 4 is installed in the lower end opening of the small hole section of the lower sleeve 3, and the center of the small end indenter 4 is provided with a lower guide perforation for the core rod to be inserted in the axial direction. The hole wall surfaces of the small hole section fit together to ensure that the small end indenter 4 is axially guided and assembled in the lower end opening of the small hole section of the lower sleeve 3 . The lower ring end face of the small end indenter 4 is flush with the ring end face of the lower end of the mold sleeve, and the pressing end face of the small end indenter 4 is the plane used to form the ring end face of the lower end of the blank product 2, that is, the small end indenter 4 The upper end of is used for the flat extruding end that is set toward the big end pressure head 1 after being loaded into the die sleeve.

The big-end indenter 1 is installed in the large-hole section of the die sleeve, and the center of the big-end indenter 1 is provided with an upper guide perforation for the core rod to move along the axial direction. The big-end indenter 1 is divided into a guide seat, a tail handle section and a large-end conical truncated sequentially from top to bottom according to its shape, wherein the outer peripheral surface of the guide seat coincides with the hole wall surface of the large hole section to ensure that the guide seat Move along the axial direction and assemble in the large hole section; the tail handle section is coaxially protruded at the lower end of the guide seat, the tail handle section is a cylinder thinner than the guide seat, and the tail handle section is used to insert into the upper end of the raw material, while in the The upper end of the blank product 2 forms a cylindrical upper port; the large end cone is located at the pressing end of the large end indenter 1, and the large end cone is a cone whose outer diameter gradually decreases from top to bottom, and the large end cone The outer peripheral surface of the pedestal is an outwardly convex arc surface, and the outer peripheral surface of the large-end cone truncated is matched with the hole wall surface of the tapered hole section to ensure that the variable diameter section of the blank product 2 is consistent with the product.

The working principle of the mold in this embodiment is as follows: a near net shape method for polytetrafluoroethylene products.

Embodiment 1 of the polytetrafluoroethylene product near net shape method of the present invention: the method is in order to prepare the blank part of the first polytetrafluoroethylene product, and the mold adopted is the mold in the mold embodiment 1, and the method includes the following step:

1. Put the raw materials into the mold. The structure of the mold is the same as that of the near-net shape mold for PTFE products in the above examples. After the raw materials are loaded, the small end pressure head is positioned on the worktable of the press so that the small The end pressure head and the mold sleeve remain relatively fixed, and the large end pressure head of the mold is fixed on the pressure head of the press;

2. Start the press, and when the small-end indenter and the mold sleeve remain stationary on the workbench, the pressure head drives the large-end indenter to press the raw material downward until it reaches the gap between the large-end indenter and the small-end indenter The raw material is pressed into a blank product, which has a large diameter section, a variable diameter section and a small diameter section arranged in sequence from top to bottom, the outer diameter of the large diameter section is larger than that of the small diameter section, and the variable diameter section The outer diameter gradually decreases from the large diameter section to the small diameter section;

3. After the blank is taken out of the mold, the blank is sintered and cut in sequence until the blank is processed into a product.

Taking 4.4kg of raw material as an example, the process duration of the above process steps is: in step 1, the time for loading is 10mi; After 5 minutes, the pressure was released to 0MPa at a constant speed, and the demoulding (5 minutes) was completed, and the total time was 45 minutes. This process step is more convenient for loading materials, saves the time for turning over and pressing the other side, and is convenient for demoulding, so the production efficiency of pressing is greatly improved.

The key performance detection and comparison of the product made by the method in this example and the product made by the traditional process, as shown in Figure 5 to Figure 8, wherein A represents the product made by the traditional process, and B represents the method in this embodiment The produced product. Measure the density uniformity of each part of the PTFE products obtained by two different methods and molds, the tensile strength of the disintegrated structure, the electrical strength of the disintegrated structure, and conduct the power frequency withstand voltage test of the PTFE products.

① Density uniformity: 5 samples were selected from the upper, middle and lower parts of the PTFE molded product respectively, and one test was carried out for each, and the test was carried out according to the method described in 5.1 of GB/T 1033.1-2008. The liquid is water, the test temperature is 23±2°C, the density of the sample is calculated according to the Chinese formula 2 of GB/T 1033.1-2008, and the average value is taken;

②Tensile strength: Tested according to Article 5.1 of GB/T 2567-2008, the test temperature is 23±2°C, the tensile rate is 5mm/min, test 5 samples, and take the average value;

③Electrical strength: The test is carried out according to the method described in 10.1 of GB/T 1408-2006, the sample diameter is 100mm, the thickness is 1mm, the test temperature is 23±2°C, it is carried out in 0.4MPa SF6 gas, the boost rate is 500V/s, use Two symmetrical flat electrodes, test 5 samples, and take the average value.

④Power frequency withstand voltage test: 750kV/1min withstand voltage test is carried out on PTFE molded products, requiring no flashover and breakdown during the process.

Experimental results:

Density uniformity comparison: see Figure 6;

Tensile strength comparison: see Figure 7;

Comparison of breakdown strength; see Figure 8.

It can be seen that the density uniformity, electrical properties and mechanical properties of PTFE molded products obtained by using the near net shape pressing method and mold are basically the same as those obtained by using the traditional pressing method, but the material utilization rate and production efficiency are greatly improved. The cost was saved by 6.834 million yuan. At the same time, the production efficiency of the molding process was increased by 183.99%, and the production efficiency of the cutting process was increased by 75%. This type of near-net shape method can also be extended and applied to other non-metal parts manufacturing fields (such as thermoplastic engineering plastics, etc.), resulting in greater economic benefits.

Embodiment 2 of the near-net shape mold for polytetrafluoroethylene products in the present invention: the difference between this embodiment and embodiment 1 is that, as shown in Figure 9, the mold is mainly suitable for preparing the second polytetrafluoroethylene The blank part of the product, the pressing end of the small end pressure head 24 is protruded with a small end cone 24 coaxially inserted in the inner hole of the lower sleeve 23, and the function of the small end cone 24 is to extrude the blank. The small end of the piece 22 is flared.

Embodiment 2 of the near-net shape method for polytetrafluoroethylene products of the present invention: the difference between this embodiment and embodiment 1 is that this method is mainly suitable for preparing the blank parts of the second polytetrafluoroethylene products, and the mold used It is the mold in the mold embodiment 2, and the steps of using the mold are the same as those in the embodiment 1, and will not be repeated here.

Embodiment 3 of the near-net shape mold for polytetrafluoroethylene products in the present invention: the difference between this embodiment and embodiment 1 is that, as shown in Figure 10, the mold is mainly suitable for preparing the third polytetrafluoroethylene For the blank part 32 of the product, the lower sleeve 33 is turned upside down so that the small end of the forming hole section in the lower sleeve 33 is on the top and the big end is on the bottom. The corresponding big end pressure head 31 is a constant pressure head at the bottom of the mold sleeve. The small end indenter 34 is a dynamic indenter located above the large end indenter 31; at the same time, the cylinder diameters of the middle sleeve 37 and the upper sleeve 39 are reduced, so that the inner diameters of the middle sleeve 37 and the upper sleeve 39 are equal to the forming hole section small end aperture.

Embodiment 3 of the near-net shape method for polytetrafluoroethylene products of the present invention: the difference between this embodiment and embodiment 1 is that this method is mainly suitable for preparing the third kind of blank parts of polytetrafluoroethylene products, and the mold used It is the mold in the mold embodiment 3, and the use steps of the mold are also adopted to press the dynamic pressure head from top to bottom while the constant pressure head remains still, and will not be repeated here.

Other embodiments of the near-net-shape mold for polytetrafluoroethylene products in the present invention: the mold sleeve can also adopt a split or integral structure. In addition, the tapered hole section in the die set can be at the bottom, or in the middle and topmost, so that the raw material can be shaped at the tapered hole section by changing the movement form of the die set and the two indenters.

Other embodiments of the near-net-shape method for polytetrafluoroethylene products in the present invention: the process of compression molding from the top can also be changed to simultaneous molding from the bottom or from both sides, or even adopt the method of molding on both sides after turning over.

As can be seen from other above-mentioned embodiments, the polytetrafluoroethylene product near-net shape method among the present invention can be implemented according to the following steps:

Step 1: Fill the raw material in the mold sleeve. The inner hole of the mold sleeve has a coaxially connected forming hole section and a filling hole section. The forming hole section is a stepped hole, and the filling hole section is a straight hole. The raw material is filled with the filling hole section and The forming hole section, and the small end indenter at the small hole end of the forming hole section and the large end indenter at the small hole end of the forming hole section are provided at both ends of the mold sleeve, and the compression end of the large end indenter is provided with The large-end truncated cone is coaxially spaced from the inner wall of the mold casing, and the large-end pressure head and/or the small-end pressure head are dynamic pressure heads that can seal and slide in the inner hole of the mold casing;

Step 2: Press the dynamic indenter so that the compression end of the big-end indenter and the compression end of the small-end indenter move relative to each other in the mold sleeve until the large-end indenter reaches the large port of the forming hole section, and the small-end indenter The end pressure head reaches the small port of the forming hole section, and the raw material in the filling hole section is completely pressed into the forming hole section, so that the raw material is extruded into a rough product in the forming hole section by the big end and small end pressure head.

Claims (10)

1. The near net shape method of polytetrafluoroethylene product is characterized in that, comprises the following steps: Step 1: Fill the raw material in the mold sleeve. The inner hole of the mold sleeve has a coaxially connected forming hole section and a filling hole section. The forming hole section is a stepped hole, and the filling hole section is a straight hole. The raw material is filled with the filling hole section and The forming hole section, and the small end indenter at the small hole end of the forming hole section and the large end indenter at the small hole end of the forming hole section are provided at both ends of the mold sleeve, and the compression end of the large end indenter is provided with The large-end truncated cone is coaxially spaced from the inner wall of the mold casing, and the large-end pressure head and/or the small-end pressure head are dynamic pressure heads that can seal and slide in the inner hole of the mold casing; Step 2: Press the dynamic indenter so that the compression end of the big-end indenter and the compression end of the small-end indenter move relative to each other in the mold sleeve until the large-end indenter reaches the large port of the forming hole section, and the small-end indenter The end pressure head reaches the small port of the forming hole section, and the raw material in the filling hole section is completely pressed into the forming hole section, so that the raw material is extruded into a rough product in the forming hole section by the big end and small end pressure head. 2. The near net shape method of polytetrafluoroethylene products according to claim 1, characterized in that, in step 1, one of the large-end indenter and the small-end indenter is a dynamic indenter, and the other is in the forming hole The constant pressure head in the corresponding port of the segment; in step 2, by pressing the dynamic pressure head in the direction close to the constant pressure head, the large end and small end pressure heads move relative to each other. 3. The mold that is specially used in implementing the near-net shaping method of polytetrafluoroethylene products as claimed in claim 1 includes a mold cover for containing raw materials, and the inner hole of the mold cover has a coaxially connected forming hole section and a filler hole section, the forming hole section is a stepped hole, and the filling hole section is a straight hole; it also includes a small end pressure head for the small hole end of the self-forming hole section to compress the raw material and a large hole end for the self-forming hole section to compress the raw material The big-end pressure head, the big-end pressure head and/or the small-end pressure head are dynamic pressure heads that can seal and slide in the inner hole of the die sleeve, and the big-end and small-end pressure heads both have pressure points for compressing raw materials. On the tight end, the pressing end of the big end pressure head protrudes from the big end conical frustum for coaxial spaced insertion in the inner hole of the mold sleeve. 4. The mold according to claim 3, wherein the filling hole section is at one end of the forming hole section, and one of the big end indenter and the small end indenter is used for sealing and sliding from the filling hole section to the forming hole section One is the dynamic pressure head in the corresponding port, and the other is the constant pressure head for holding in the corresponding port of the type hole segment. 5. The mold according to claim 4, wherein the filling hole section is at the big end of the forming hole section, the big end pressure head is a dynamic pressure head that can seal and slide in the filling hole section, and the small end pressure head For the constant pressure head. 6. The mold according to claim 4, wherein the filling hole section is at the small end of the forming hole section, the small end pressure head is a dynamic pressure head that can seal and slide in the filling hole section, and the big end pressure head For the constant pressure head. 7 . The mold according to claim 6 , wherein a small-end truncated cone is protruded from the pressing end of the small-end indenter for coaxially spaced insertion into the inner hole of the mold sleeve. 7 . 8. The mold according to any one of claims 3 to 6, characterized in that it also includes a core rod coaxially installed in the die sleeve, and the big end and small end pressure head are provided with the same The shaft is provided with a guide hole for the core rod to guide and seal in the axial direction. 9. The mold according to claim 8, characterized in that, the core rod is formed by butt jointing of more than two sub-rod bodies sequentially from top to bottom. 10. The mold according to any one of claims 3 to 6, characterized in that, the mold casing comprises more than two coaxial butt-joint sleeves, the forming hole section is located in one of the sleeves, and the filling hole section It is composed of the inner holes of the remaining sleeves.