A thermal-mechanical synergistic regulation device and method in thin film hot pressing

Abstract

The application discloses a kind of heat-power synergic regulation and control device and method in thin film hot pressing processing, it includes: upper die and lower die, upper die and lower die are all provided with pressure melting boss, two pressure melting bosses are contacted and form the pressure melting area of thin film;Membrane tensioning mechanism, it includes four elastic loading mechanisms set to the periphery of lower die, and controllable pre-tension is applied to the four peripheral edges of thin film by elastic loading mechanism;Cooling guard ring, it surrounds on the side wall of pressure melting boss, cooling guard ring is internally provided with cooling liquid circulation channel for actively cooling the film area outside the boundary of pressure melting area in hot pressing process;The scheme is effectively overcome by double constraint of mechanics and thermodynamics The inherent defects that the strength and modulus of PTFE model significantly reduce at high temperature and are extremely easy to deform, make the pressure melting area boundary clear, size fidelity is high, to completely inhibit film necking, realize high conformal processing.

Description

Technical Field

[0001] This invention relates to the field of thin film thermal processing technology, and specifically to a thermo-mechanical synergistic control device and method for thin film hot pressing processing. Background Technology

[0002] Polytetrafluoroethylene (PTFE) membranes are widely used in medical filters, fuel cell membrane electrodes, high-frequency copper-clad laminates, and aerospace seals due to their excellent chemical resistance, high and low temperature resistance, low coefficient of friction, and dielectric properties. In practical applications, it is often necessary to perform localized hot-pressing processing on PTFE membranes, such as sealing the edges of two PTFE membranes to form a bag-like structure, selectively bonding PTFE membranes with functional layers, or planarizing and shaping localized areas of a single-layer PTFE membrane.

[0003] However, PTFE membranes enter a highly elastic state at temperatures close to their melting point (327°C) (typical melt-sealing temperatures of 280~320°C), where molecular chain mobility significantly increases and tensile strength decreases sharply. When pressure and heat are applied only to a localized area of ​​the membrane, a series of serious problems arise: 1. Necking effect: The material softens in the heated local area and shrinks in the plane under compressive stress or residual stress, resulting in a smaller width and shape distortion of the weld zone, i.e., "necking". Due to its extremely high melt viscosity and low surface energy, PTFE is particularly prone to necking.

[0004] 2. Overall deformation and displacement: The large difference in thermal expansion between the unpressed area and the pressurized area makes the entire film prone to sliding, wrinkling or warping within the mold cavity, causing the target melt position to shift and the product dimensions to fail.

[0005] 3. Positioning difficulties: Traditional mechanical positioning methods (such as pins and pressure frames) cannot effectively restrain the shrinkage trend of PTFE membranes at high temperatures, and instead cause membrane tearing due to stress concentration. The high lubricity of PTFE membranes makes positioning even more difficult.

[0006] Existing technologies mostly employ methods such as full-area pressure melting or adding heat insulation plates, but they cannot solve the problem of heat-induced deformation unique to local hot pressing. Therefore, there is an urgent need for a device and method that can coordinate and control from both thermal and mechanical dimensions to achieve stable dimensional maintenance of PTFE membranes during local hot pressing. Summary of the Invention

[0007] To address the aforementioned shortcomings of the prior art, this invention provides a thermo-mechanical synergistic control device and method for thin film hot pressing, which solves the problems of necking, deformation, and positioning failure caused by high temperature during local hot pressing of PTFE films in the prior art.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, a thermo-mechanical coordinated control device for thin film hot pressing is provided, comprising: The upper die and the lower die are both provided with melting protrusions. The two melting protrusions are aligned and in contact to form the melting area of ​​the thin film. The membrane tensioning mechanism includes four elastic loading mechanisms disposed around the lower die, and applies controllable pretension to the periphery of the membrane through the elastic loading mechanisms; A cooling retaining ring surrounds the side wall of the pressing protrusion, and the cooling retaining ring is provided with a coolant circulation channel inside for actively cooling the film area outside the boundary of the pressing area during the hot pressing process.

[0009] Furthermore, the elastic loading mechanism includes a base disposed around the lower die, a telescopic cylinder disposed on the base, and the telescopic end of the telescopic cylinder is connected to a movable seat slidably disposed on the base. The movable seat is fixedly connected to one end of a pull rod, and the other end of the pull rod is provided with a clamping member for clamping the edge of the film.

[0010] Furthermore, the clamping component includes a mounting plate, the middle of which is fixedly connected to the end of the pull rod. Several sliding rods arranged at intervals are movably passed through the mounting plate. A miniature electric gripper is provided at one end of the sliding rod near the lower die, and a retaining ring is provided at the other end of the sliding rod. A compression spring is sleeved on the sliding rod located between the retaining ring and the mounting plate, and a pressure sensor is provided between the compression spring and the retaining ring.

[0011] Furthermore, asbestos heat insulation pads are provided on the lower surface of the upper mold and the upper surface of the lower mold.

[0012] Furthermore, there are two coolant circulation channels, and the two coolant circulation channels flow in opposite directions. Both coolant circulation channels are connected in a closed loop to an external coolant circulation supply device.

[0013] Furthermore, the upper die has several pin holes around its perimeter, and the lower die has several cylindrical pins around its perimeter for engaging with the pin holes and positioning the upper and lower dies.

[0014] Secondly, a control method for a thermo-mechanical synergistic control device in thin film hot pressing is provided, comprising the following steps: S1: Place the film on the lower die and apply controllable pretension to the four edges of the film through four elastic loading mechanisms until the film is taut and laid flat on the upper surface of the melt-forming bumps of the lower die. S2: Align and close the upper and lower molds until both melting protrusions are in contact with the melting area of ​​the film; S3: Apply a predetermined pressure to the film through the melting bump of the upper die and heat the melting bump to perform hot pressing on the melting area of ​​the film; at the same time, open the cooling guard ring to cool the film outside the boundary of the melting area. S4: Maintain the predetermined pressure of the melt-melting bump and cool it to the preset temperature. Then, release the elastic loading mechanism, depressurize, demold, and remove the PTFE film.

[0015] Furthermore, the surfaces of the upper die, lower die, and fused bump are all chrome-plated, and the surface roughness Ra≤0.4μm.

[0016] Furthermore, the control method is applied to the local planarization of monolayer films, the edge sealing of multilayer films, and the selective composite of films and functional layers.

[0017] The beneficial effects of this invention are as follows: 1. This solution effectively overcomes the inherent defects of PTFE molds, such as significant reduction in strength and modulus and easy deformation at high temperatures, through dual constraints of mechanics and thermodynamics. A controllable pretension is applied to the perimeter of the film using an elastic loading mechanism to provide mechanical constraints against shrinkage. A cooling retaining ring forms a thermal barrier, ensuring that only the melt-forming area is heated and compressed, while the remaining areas of the film remain at a low temperature and are in non-contact with both the upper and lower molds, thus preserving the overall mechanical properties of the PTFE film. The synergistic effect of these two mechanisms results in clear boundaries and high dimensional fidelity of the melt-forming area, thereby completely suppressing film necking and achieving high conformal processing.

[0018] 2. This solution uses an elastic loading mechanism to tighten and position the film, thus eliminating the need to perforate the film and avoiding damage. The cooperation between the cylindrical pin and the pin hole ensures the mold closing accuracy, so that the two pressing protrusions are precisely aligned and form the pressing area of ​​the film.

[0019] 3. This solution uses several spaced-apart miniature electric grippers to achieve uniform clamping at multiple points around the edges of the film. Through the cooperation of sliding rods, mounting plates, retaining rings and compression springs, when the telescopic cylinder drives the moving seat to slide outward, the compression springs are gradually compressed, and their elastic tension drives the retaining rings, sliding rods and miniature electric grippers to slide outward, thereby achieving flexible loading of the film edges to avoid irreversible damage to the film caused by rigid loading.

[0020] 4. This solution can be used in various scenarios such as local flattening / stress relief of single-layer PTFE membranes, selective edge sealing of multi-layer PTFE membranes, and selective composite of PTFE membranes with functional layers, and has a wide range of applications. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The above and other objects, features, and advantages of the present invention will become clearer through the accompanying drawings. The same reference numerals indicate the same parts in all the drawings. The drawings are not intentionally drawn to scale to actual dimensions; the focus is on illustrating the main points of the invention.

[0022] Figure 1 This is a cross-sectional view of the upper and lower die.

[0023] Figure 2 This is a top view of the lower die and the membrane tensioning mechanism.

[0024] Figure 3 This is a side view of the elastic loading mechanism.

[0025] Among them, 1. Upper die, 2. Lower die, 3. Press-melting protrusion, 4. Elastic loading mechanism, 5. Cooling guard ring, 6. Base, 7. Telescopic cylinder, 8. Moving seat, 9. Tie rod, 10. Mounting plate, 11. Sliding rod, 12. Miniature electric gripper, 13. Retaining ring, 14. Compression spring, 15. Pressure sensor, 16. Asbestos heat insulation pad, 17. Pin hole, 18. Cylindrical pin. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0028] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0029] Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0030] like Figures 1 to 3 As shown, the thermo-mechanical coordinated control device in the film hot pressing process of this scheme includes: upper mold 1, lower mold 2, film tensioning mechanism and cooling retaining ring 5.

[0031] Both the upper mold 1 and the lower mold 2 are provided with melting protrusions 3. The two melting protrusions 3 are aligned and contact each other to form the melting area of ​​the PTFE film. Specifically, the upper mold 1 and the lower mold 2 are connected to their respective pressure plates by a stacking welding process. The pressure plates are used to contact the pressing surface of the press, but do not directly contact the PTFE film during hot pressing to avoid heat absorption by the pressure plates and damage to the PTFE film by surface defects. The upper mold 1 is provided with four pin holes 17 around its perimeter, and the lower mold 2 is provided with four cylindrical pins 18 around its perimeter for socketing with the pin holes 17 and positioning the upper mold 1 and the lower mold 2. This allows for repeated positioning when the upper mold 1 and the lower mold 2 are closed, with a repeat positioning accuracy of ≤0.02mm, so that the two melting protrusions 3 are accurately aligned and form the melting area of ​​the film. Asbestos heat insulation pads 16 are provided on the lower surface of the upper mold 1 and the upper surface of the lower mold 2.

[0032] The membrane tensioning mechanism of this solution includes four elastic loading mechanisms 4 arranged around the lower mold 2, and the elastic loading mechanisms 4 apply controllable pretension to the periphery of the PTFE membrane. The elastic loading mechanism 4 includes a base 6 arranged around the lower mold 2, a telescopic cylinder 7 arranged on the base 6, and the telescopic end of the telescopic cylinder 7 is connected to a movable seat 8 slidably arranged on the base 6. The movable seat 8 is fixedly connected to one end of the pull rod 9, and the other end of the pull rod 9 is provided with a clamping member for clamping the edge of the membrane.

[0033] The clamping component includes a mounting plate 10, the middle of which is fixedly connected to the end of the pull rod 9. Several sliding rods 11 are movably inserted through the mounting plate 10 at intervals. A miniature electric gripper 12 is provided at one end of the sliding rod 11 near the lower mold 2, and a flexible lip is provided on the contact surface between the miniature electric gripper 12 and the PTFE membrane. A retaining ring 13 is provided at the other end of the sliding rod 11. A compression spring 14 is sleeved on the sliding rod 11 located between the retaining ring 13 and the mounting plate 10. A pressure sensor 15 can be provided between the compression spring 14 and the retaining ring 13 to detect the elastic tension of the compression spring 14.

[0034] This solution uses several spaced-apart miniature electric grippers 12 to achieve uniform clamping at multiple points around the edges of the film. Through the cooperation of the sliding rod 11, mounting plate 10, retaining ring 13 and compression spring 14, when the telescopic cylinder 7 drives the moving seat 8 to slide outward, the compression spring 14 is gradually compressed, and its elastic tension drives the retaining ring 13, sliding rod 11 and miniature electric grippers 12 to slide outward, thereby achieving flexible loading of the film edge to avoid irreversible damage to the film caused by rigid loading.

[0035] The cooling ring 5 surrounds the side wall of the pressing protrusion 3. The cooling ring 5 is provided with a coolant circulation channel inside for actively cooling the film area outside the boundary of the pressing area during the hot pressing process. There are two coolant circulation channels, and the two coolant circulation channels flow in opposite directions. Both coolant circulation channels are connected in a closed loop to the external coolant circulation supply equipment to eliminate the difference in cooling effect between the upstream and downstream of the coolant circulation channels.

[0036] This solution also provides a control method for a thermo-mechanical synergistic control device in thin film hot pressing, which includes the following steps: S1: Place the PTFE film on the lower mold 2, and apply controllable pretension to the four edges of the film through four elastic loading mechanisms 4 until the film is taut and laid flat on the upper surface of the pressing protrusions 3 of the lower mold 2. S2: The upper die 1 and the lower die 2 are aligned and closed by the socketing of the cylindrical pin 18 and the pin hole 17 until both pressing protrusions 3 are in contact with the pressing area of ​​the PTFE film, while the remaining area of ​​the PTFE film is separated from the upper die 1 and the lower die 2; the cooling guard ring 5 is in contact with the surface of the PTFE film or maintains a gap of 0.1mm. S3: Apply a predetermined pressure to the PTFE film through the melting bump 3 of the upper mold 1, and heat the melting bump 3 to perform hot pressing on the melting area of ​​the film; at the same time, open the cooling guard ring 5 to cool the film outside the boundary of the melting area. S4: After maintaining the predetermined pressure of the pressing and melting bump 3 and cooling it to the preset temperature, release the elastic loading mechanism 4, depressurize, demold, and remove the PTFE film.

[0037] The surfaces of the upper die 1, lower die 2, and fusion protrusion 3 in this design are all chrome-plated, and the surface roughness Ra≤0.4μm; in order to keep the surface smooth and prevent the PTFE film from adhering or being scratched.

[0038] The control method presented in this scheme can be applied to the local planarization of single-layer films, edge sealing of multilayer films, and selective lamination of films with functional layers. Its applications are wide-ranging, and specific application examples are given below: Example 1: Annular sealing of a double-layer PTFE membrane.

[0039] Device parameters: The pressure-melting protrusion 3 is a circular ring with an outer diameter of 10cm and a ring width of 1.5cm; the elastic loading mechanism 4 applies a pretension of 2 N / cm (uniform on all four sides); the cooling guard ring 5 is circulated with 20℃ water; In practice: two layers of PTFE film are stacked on the lower mold 2, and the elastic loading mechanism 4 clamps the periphery and applies pretension; after the mold is closed, the pressing protrusion 3 presses the annular area, and the gap in the remaining area is 0.8mm; the pressing protrusion 3 is heated to 310℃, the predetermined pressure is 10MPa, and the pressure is held for 30 seconds; at the same time, the cooling guard ring 5 is turned on; heating is stopped, the pressure is maintained, and cooling water is circulated to reduce the pressing zone to 80℃ at about 40℃ / min; the pressure is released, the elastic loading mechanism 4 is released, and the mold is demolded.

[0040] Results: The annular weld band is clear and continuous, with a width of 1.50±0.02cm; there is no necking deformation or membrane displacement; the two PTFE membranes can be easily separated in the outer area of ​​the ring to form a complete bag-like structure; after 100 repetitions, the dimensional deviation is less than 0.03mm.

[0041] Example 2: Local flattening and stress relief of a single-layer PTFE membrane.

[0042] Device parameters: The pressing and melting bump 3 is a 20cm×20cm square; the pretension is 1 N / cm; the cooling guard ring 5 has a water temperature of 25℃; in specific implementation: the rolled PTFE membrane is stretched, locally heated to 300℃, the predetermined pressure is 5MPa, the pressure is held for 2 minutes, and then rapidly cooled.

[0043] Results: The flatness of the flattened area is ≤0.05mm, and the surrounding unflattened areas remain in their original state without necking or wrinkling.

[0044] Example 3: Straight edge sealing of PTFE double-layer film.

[0045] Device parameters: The pressing and melting bump 3 is a straight line with a width of 2cm and a length of 50cm; the pretension is 1.5 N / cm; the water temperature of the cooling guard ring 5 is 20℃; in specific implementation: stack two layers of PTFE membrane, heat the pressing and melting bump 3 to 310℃, set the predetermined pressure to 8MPa, and hold the pressure for 45 seconds.

[0046] Results: The straight edge sealing width was 2.02±0.02mm, with no necking, and the edge sealing strength test reached the membrane body failure strength.

[0047] Comparative example: When the thermal-mechanical synergistic control of this solution is not available, the same PTFE membrane and the same annular mold are used, but no pretension is applied and no cooling retainer ring 5 is used; after pressing and melting at 310℃ and 10MPa for 30 seconds: the outer edge of the annular weld zone shows obvious necking, and the width is reduced from 1.5mm to 0.9mm; the entire membrane shows wavy warping, and the product is scrapped.

[0048] In summary, this solution effectively overcomes the inherent defects of PTFE molds, such as significant reduction in strength and modulus and easy deformation at high temperatures, through dual constraints of mechanics and thermodynamics. The elastic loading mechanism 4 applies controllable pretension to the edges of the film to provide mechanical constraints against shrinkage. The cooling retaining ring 5 forms a thermal barrier, ensuring that only the melting zone is heated and compressed, while the remaining areas of the film remain at a low temperature and are in non-contact with both the upper and lower molds, thus preserving the overall mechanical properties of the PTFE film. The synergistic effect of these two mechanisms results in clear boundaries and high dimensional fidelity of the melting zone, thereby completely suppressing film necking and achieving high conformability processing.

[0049] Although the specific embodiments of the invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent; various modifications and variations that can be made by a person skilled in the art without inventive effort within the scope described in the claims are still within the scope of protection of this patent.

Claims

1. A thermo-mechanical synergistic control device for thin film hot pressing, characterized in that, include: The upper die and the lower die are provided with pressing protrusions on the lower surface of the upper die and the upper surface of the lower die. The two pressing protrusions are aligned and contact each other to form a pressing area of ​​the film. The membrane tensioning mechanism includes four elastic loading mechanisms disposed around the lower die, and applies controllable pretension to the periphery of the membrane through the elastic loading mechanisms; A cooling retaining ring surrounds the sidewall of the pressing and melting protrusion, and the cooling retaining ring is provided with a coolant circulation channel inside for actively cooling the film area outside the boundary of the pressing and melting area during the hot pressing process.

2. The thermo-mechanical coordinated control device for thin film hot pressing according to claim 1, characterized in that, The elastic loading mechanism includes a base arranged around the lower die, a telescopic cylinder is provided on the base, and the telescopic end of the telescopic cylinder is connected to a movable seat slidably arranged on the base. The movable seat is fixedly connected to one end of a pull rod, and the other end of the pull rod is provided with a clamping member for clamping the edge of the film.

3. The thermo-mechanical coordinated control device for thin film hot pressing according to claim 2, characterized in that, The clamping component includes a mounting plate, the middle of which is fixedly connected to the end of the pull rod. Several sliding rods arranged at intervals are movably passed through the mounting plate. A miniature electric gripper is provided at one end of the sliding rod near the lower die. A retaining ring is provided at the other end of the sliding rod. A compression spring is sleeved on the sliding rod located between the retaining ring and the mounting plate, and a pressure sensor is provided between the compression spring and the retaining ring.

4. The thermo-mechanical coordinated control device for thin film hot pressing according to claim 3, characterized in that, Both the lower surface of the upper mold and the upper surface of the lower mold are provided with asbestos heat insulation pads.

5. The thermo-mechanical coordinated control device for thin film hot pressing according to claim 1, characterized in that, The coolant circulation channel has two sections, and the two coolant circulation channels flow in opposite directions. Both coolant circulation channels are connected in a closed loop to an external coolant circulation supply device.

6. The thermo-mechanical coordinated control device for thin film hot pressing according to claim 1, characterized in that, The upper die has several pin holes around its perimeter, and the lower die has several cylindrical pins around its perimeter for engaging with the pin holes and positioning the upper and lower dies.

7. A control method using the thermo-mechanical synergistic control device in thin film hot pressing as described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Place the film on the lower die and apply controllable pretension to the four edges of the film through four elastic loading mechanisms until the film is taut and laid flat on the upper surface of the melt-forming bumps of the lower die. S2: Align and close the upper and lower molds until both melting protrusions are in contact with the melting area of ​​the film; S3: Apply a predetermined pressure to the film through the melting bump of the upper die and heat the melting bump to perform hot pressing on the melting area of ​​the film; at the same time, open the cooling guard ring to cool the film outside the boundary of the melting area. S4: Maintain the predetermined pressure of the melt-melting bump and cool it to the preset temperature. Then, release the elastic loading mechanism, depressurize, demold, and remove the PTFE film.

8. The control method of the thermo-mechanical synergistic control device in thin film hot pressing according to claim 7, characterized in that, The surfaces of the upper die, lower die, and fused protrusion are all chrome-plated, and the surface roughness Ra≤0.4μm.

9. The control method of the thermo-mechanical synergistic control device in thin film hot pressing according to claim 7, characterized in that, The control method is applied to the local planarization of single-layer films, the edge sealing of multilayer films, and the selective composite of films and functional layers.

Images