A combined cap type thermoplastic composite end cover hot stamping forming die

Abstract

The application discloses a combined cap type thermoplastic composite end cover hot stamping forming die and belongs to the technical field of high-performance thermoplastic composite manufacturing. The die comprises a matched upper die and lower die. The upper die is provided with at least two interval distributed cap type bosses. A retractable ejection mechanism is arranged between the bosses and extends the working plane of the upper die in the open die state. The lower die is provided with a cavity matched with the target part and a thickness limiting step. When the die is closed, the ejection mechanism first contacts the molten composite material and forms clamping with the lower die, and finally forms a continuous closed forming space with the upper die. The application solves the problem of bridge phenomenon of the cap type feature in the forming process, can prepare the combined cap type thermoplastic composite end cover meeting the use requirements in shape and size, and effectively improves the qualified rate of the parts.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-performance thermoplastic composite material manufacturing, and particularly relates to a combined cap type thermoplastic composite material end cover hot stamping forming die. BACKGROUND

[0002] Thermoplastic resin-based composite materials have high toughness and damage tolerance, excellent impact resistance, unlimited prepreg storage period, short molding cycle, high production efficiency, secondary molding and welding, recycling and other advantages, and have become the focus of research and development in the field of high-end composite materials in various countries. Thermoplastic composite materials have excellent processing flexibility due to the characteristics of the resin matrix that can be repeatedly heated, melted and cooled to form. The hot stamping forming process can fully utilize the advantages of rapid forming of thermoplastic composite materials, and relatively complex thermoplastic composite parts can be prepared.

[0003] The hot stamping forming process of thermoplastic composite materials is a process of changing two-dimensional thermoplastic composite material laminates into three-dimensional thermoplastic composite material parts, which specifically includes: heating the composite material or preform to above the melting temperature of the resin matrix through an infrared furnace, then rapidly transferring the composite material in a molten state to a hot stamping forming die with a certain temperature, then rapidly closing the mold to shape through the die, and finally cooling to open the mold to form a composite material part with a specific shape.

[0004] At present, the most mature thermoplastic composite parts prepared by the hot stamping forming process are angle pieces and bracket parts. The forming process of such parts mainly involves bending of the composite material, and the deformation process is relatively simple. Therefore, the hot stamping forming die used is also relatively simple, which is usually an upper and lower combined die conforming to the configuration of the part. For parts with combined cap type features, if a simple die is used for hot stamping forming, the bosses on the die will simultaneously contact the molten thermoplastic composite material during the forming process, causing the thermoplastic composite material to rapidly cool and form a hard skin or even completely solidify, thereby losing the ability to deform, resulting in bridging between multiple cap features or shear fracture, and the part cannot meet the shape requirements. Therefore, in order to solve the bridging and fracture problems that easily occur during the hot stamping forming process of the above-mentioned thermoplastic composite parts with combined cap type features, a new hot stamping forming die needs to be designed to improve the hot stamping forming yield of complex configuration thermoplastic composite parts. SUMMARY

[0005] The purpose of the present application is to provide a combined cap type thermoplastic composite material end cover hot stamping forming die, which has the advantages of realizing material ordered sliding, uniform filling of the forming space, avoiding bridging and shear fracture, and improving the uniformity of the part wall thickness and the surface quality.

[0006] The technical scheme adopted by the present application to achieve the above-mentioned purpose is:

[0007] A combined cap-shaped thermoplastic composite end cover hot stamping forming die comprises a matched upper die and lower die, the upper die is provided with at least two spaced cap-shaped bosses, a retractable ejection mechanism is arranged between the bosses and extends out of the working plane of the upper die in the open die state, the lower die is provided with a cavity matched with the target part and a thickness limiting step, wherein when the die is closed, the ejection mechanism first contacts the molten composite material and forms clamping with the lower die, and finally forms a continuous closed forming space with the upper die.

[0008] Preferably, the ejection mechanism comprises: a flat template whose profile matches the gap between the bosses; at least two guide columns, one end of which is fixed to the flat template and the other end of which penetrates the upper die; and an elastic element sleeved on the guide column to provide a pre-tightening force in the open die direction.

[0009] Preferably, the ejection mechanism further comprises: an adjusting nut threadedly matched with the guide column to control the extension amount of the guide column.

[0010] Preferably, the upper die is provided with a stepped hole, the hole diameter change forms a stroke limiting of the guide column; the flat template is provided with a positioning structure matched with the shape of the end of the elastic element, and the positioning structure comprises a spring positioning recess and a threaded blind hole.

[0011] Preferably, the boss has a gradually decreasing cross-sectional dimension from the bottom to the top, and the side surface and the bottom surface are transitioned by a smooth curved surface, and the distance L1 between adjacent bosses is greater than or equal to 0.5 times the minimum width W1 of the boss.

[0012] Preferably, the side wall of the cavity is transitioned with the bottom surface by a continuous curved surface, the profile of which forms an equal gap matching with the boss, the working surface of the thickness limiting step is parallel to the parting surface of the upper die, and a material sliding guide slope is arranged between the cavity and the thickness limiting step.

[0013] Preferably, the upper die is provided with a heating channel perpendicular to the main stress direction of the die, and the lower die is provided with a temperature monitoring channel corresponding to the position of the boss, and the detection end of the temperature monitoring channel is close to the surface of the cavity, and the upper die and the lower die are respectively provided with symmetrically distributed die fixing structures at the edges of the respective parting surfaces.

[0014] Preferably, the heating channel and the temperature monitoring channel are respectively provided with at least two electric heating pipes and thermocouples in the upper die, and the thermocouples and the electric heating pipes are installed in the upper die through the heating channel.

[0015] Preferably, a thermoplastic composite end cover preparation method comprises: a) a pre-adjustment stage: setting the height difference between the ejection mechanism working plane and the upper die forming surface; b) a mold closing initialization stage: the ejection mechanism first contacts the material and forms a regional pre-clamping; c) a main forming stage: the boss intervention makes the material slide along the preset path to the inside of the cavity; d) a cavity closing stage: the ejection mechanism resets to make the material completely fill the forming space; e) a pressure maintaining and shaping stage: maintaining the mold closing force until the material completes solidification.

[0016] Preferably, in step b), the pre-clamping force formed by the ejection mechanism and the lower die is less than the final mold closing pressure; in step c), the sliding direction of the material forms an angle with the tapering direction of the boss; in step d), the ejection mechanism reset speed is coordinated with the material cooling rate.

[0017] As can be seen from the above, the present application provides a combined cap type thermoplastic composite end cover hot stamping forming die and its preparation method, which forms pre-clamping and guides the material to slide orderly in the early stage of mold closing through the ejection mechanism, cooperates with the tapered boss structure and the guide cavity design, effectively solves the bridging and shear fracture problems in the forming process of multi-cap type parts, and has the advantages of realizing material orderly sliding, uniform filling of forming space, avoiding bridging phenomenon and shear fracture, improving part wall thickness uniformity and surface quality.

[0018] Compared with the prior art, the present application has the following beneficial effects: through the pre-clamping design of the ejection mechanism, the material is prevented from cooling and solidifying in advance due to early contact with the boss, a time window is created for sliding, the sliding conflict, bridging and shear fracture problems caused by multi-point pressure of traditional molds are solved; the boss adopts a tapered draft structure and optimized spacing, promotes the radial expansion of the material, avoids corner shear fracture, eliminates bridging and accumulation defects, and ensures contour accuracy and wall thickness uniformity; the continuous curved surface transition of the cavity cooperates with the thickness limiting step to avoid shear fracture, guide the material to slide orderly, constrain the thickness uniformity, and solve the uneven sliding problem; multiple heating and temperature monitoring channels dynamically regulate the temperature field to avoid local overcooling and overheating, improve the consistency of material sliding, and prevent resin degradation or premature solidification; the guide column and adjusting nut realize accurate control of the height of the ejection mechanism, adapt to different material thicknesses, and avoid rapid cooling and cracking caused by excessive local pressure. The above-mentioned design synergies significantly improve the forming qualification rate, contour accuracy and wall thickness uniformity of the combined cap type end cover, and systematically solve the bridging, fracture and uneven sliding problems in the hot stamping forming of composite materials. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Figure 1 is a sectional view of a combined cap type thermoplastic composite end cover hot stamping forming die according to the present application;

[0020] Figure 2It is a top view of the ejector mechanism plane template of a combined cap-shaped thermoplastic composite end cover hot stamping forming die of the application;

[0021] Figure 3 It is a top view of the upper die of a combined cap-shaped thermoplastic composite end cover hot stamping forming die of the application;

[0022] Figure 4 It is a top view of the lower die of a combined cap-shaped thermoplastic composite end cover hot stamping forming die of the application;

[0023] Figure 5 It is a metallographic morphology schematic diagram of the end cover fillet transition of the target part obtained by the die of the application;

[0024] Figure 6 It is a porosity image schematic diagram of the end cover fillet transition of the target part obtained by the die of the application.

[0025] The drawings are as follows: upper die 1, heating channel 2, temperature monitoring channel 3, elastic element 4, target part 5, limiting step 6, adjusting nut 7, die fixing structure 8, guide column 9, boss 10, plane template 11, lower die 12, spring positioning recess 13, threaded blind hole 14. DETAILED DESCRIPTION

[0026] The technical solutions of the application will be described in further detail below in combination with the specific embodiments and the drawings:

[0027] Obviously, the described embodiments are only part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0028] Reference Figures 1-4 A combined cap-shaped thermoplastic composite end cover hot stamping forming die, comprising: a matched upper die 1 and lower die 12, the upper die 1 is provided with at least two spaced cap-shaped bosses 10, a retractable ejector mechanism is arranged between the bosses 10, the position of the ejector mechanism is higher than that of the bosses 10, and the ejector mechanism is stretched out of the working plane of the upper die 1 in the open die state, the lower die 12 is provided with a cavity matched with the target part 5 and a thickness limiting step 6, wherein when the die is closed, the ejector mechanism first contacts the molten composite material and forms clamping with the lower die 12, and finally forms a continuous closed forming space together with the upper die 1.

[0029] In this embodiment, the target part 5 is a combined cap-shaped thermoplastic composite end cover, which has two round cap-shaped features. The bosses 10 and the cavity of the lower die 12 respectively match the inner profile and the outer profile of the round cap-shaped features.

[0030] The reinforcing fiber of the thermoplastic composite material includes but is not limited to carbon fiber (CF) and glass fiber (GF), and its reinforced forms include but are not limited to unidirectional continuous fiber, fiber fabric, and discontinuous long fiber. The thermoplastic resin matrix includes but is not limited to polyether ether ketone (PEEK), polyaryletherketone (PAEK), and polyphenylene sulfide (PPS) and other high-performance resins.

[0031] The upper die 1 has a number of not less than two, and the projection profile shape thereof includes but is not limited to a hat-shaped boss 10 in the shape of a circle, an ellipse, a trapezoid, etc. There is a groove between the bosses 10 that can allow the ejection mechanism to be completely pressed in. The part of the bottom surface of the upper die 1 corresponding to the groove has a stepped hole for the movement of the ejection mechanism.

[0032] In the initial stage of the clamping process, the ejection mechanism first contacts the composite material plate in a molten state, and forms a local clamping area by cooperating with the lower die 12. At this time, the boss 10 has not yet contacted the material, and the material outside the clamped area still maintains the ability to flow. As the clamping process advances, the boss 10 gradually presses into the material inside, forcing the molten material in the unclamped area to slide directionally into the cavity. When the clamping action is completed, the ejection mechanism is completely retracted into the upper die 1, together with the boss 10 to form a continuous molding surface, ensuring that the material completely fills the corners of the cavity. The thickness limiting step 6 continuously restricts the sliding direction of the material during this process, avoiding the phenomenon of over-thickness or under-thickness in local areas. It effectively solves the bridging defect and shear fracture problem in the molding process of combined hat-shaped parts. The pre-clamping area formed by the ejection mechanism delays the solidification speed of the material surface, creating a time window for the subsequent material sliding; the interval layout of the boss 10 cooperates with the guiding effect of the thickness limiting step 6 to realize the ordered filling of the material in the cavity; the finally formed continuous closed molding space ensures the contour accuracy and thickness uniformity of the part, significantly improving the molding qualification rate of complex structure parts.

[0033] The mold fixing structure 8 includes four pressing block grooves provided on the side surface of the upper die 1, which are used to fix the mold on the table surface of the hot press using pressing blocks and screws.

[0034] The ejection mechanism includes: a flat template 11 whose contour matches the gap between the bosses 10; at least two guide columns 9, one end of which is fixed to the flat template 11 and the other end of which penetrates the upper die 1; and an elastic element 4, which is sleeved on the guide column 9 to provide a pre-tightening force in the opening direction.

[0035] The elastic element 4 includes but is not limited to a cylindrical spring, which is sleeved on the guide column 9 and compressed by the flat template and the upper die 1 at both ends, respectively.

[0036] The ejection mechanism further includes an adjusting nut 7 that threadedly cooperates with the guide column 9 to control the extension amount of the guide column 9.

[0037] Both ends of the guide column 9 have threaded structures, the lower end of the guide column 9 is detachably connected with the flat mold plate 11 through the threaded structure, and the upper end of the guide column 9 is detachably connected with the adjusting nut 7 through the threaded structure, for adjusting the length of the guide column 9 extending out of the upper mold 1, so as to adjust the relative height of the flat mold plate 11.

[0038] The edge shape of the flat mold plate 11 matches the contour of the boss 10, the flat mold plate 11 is located between the two bosses 10 and is axisymmetric with the two bosses 10, and the flat mold plate 11 is attached to the boss 10 after being pressed into the plate of the upper mold 1.

[0039] The height H1 of the boss 10 is less than the length L4 of the guide column 9, and the length L4 of the guide column 9 is less than the thickness H2 of the upper mold 1.

[0040] In the open mold state, the flat mold plate 11 is higher than the boss 10, and the extension height thereof can be adjusted by the screwing depth of the nut above the guide column 9; when there are multiple ejection mechanisms, the extension height of the flat mold plate 11 in the ejection mechanism can be adjusted as needed according to the distribution of the cap features.

[0041] In the initial stage of the mold closing action, the flat mold plate 11 extends out of the working plane of the upper mold 1 under the action of the elastic element 4, preferentially contacts the molten composite material, and forms a local clamping. As the mold closing pressure increases, the guide column 9 moves axially to compress the elastic element 4, causing the flat mold plate 11 to gradually retract into the upper mold 1, at which time the boss 10 begins to intervene and push the material to slide into the cavity. In this process, the guiding action of the guide column 9 can prevent the flat mold plate 11 from deflecting, and the pre-tightening force of the elastic element 4 can balance the pressure state of different regions of the material, thereby preventing the material from being sheared and broken due to local stress concentration. The above scheme can ensure that the molten composite material is uniformly clamped in the early stage of forming, avoiding the conflict of sliding paths caused by multiple points being pressed at the same time. The pre-tightening force adjustment function of the elastic element 4 can adapt to the forming needs of materials of different thicknesses, and the guide structure of the guide column 9 can maintain the movement precision of the ejection mechanism, thereby significantly improving the forming integrity and size consistency of the combined cap-shaped parts.

[0042] In the mold closing process, the adjusting nut 7 changes the axial position of the guide column 9 by rotating, thereby controlling the relative height of the flat mold plate 11 of the ejection mechanism and the working plane of the upper mold 1. For example, when it is necessary to increase the sliding resistance of the material, the guide column 9 can be extended outward by rotating the adjusting nut 7 clockwise, thereby increasing the extension height of the flat mold plate 11; when it is necessary to reduce the sliding resistance of the material, the extension amount of the guide column 9 can be shortened by rotating the adjusting nut 7 counterclockwise, thereby reducing the extension height of the flat mold plate 11. The adjustment process can be completed during the mold assembly stage, or it can be dynamically controlled through an online adjustment mechanism. The purpose is to realize accurate control of the working height of the ejection mechanism, ensure that the molten material forms a uniform pre-clamping area in the initial contact stage, avoid the resin matrix from cooling too early due to excessive pressure in local areas, and thereby reduce the shear crack defects caused by the blocking of the material sliding path during the forming process of the cap features.

[0043] Referring to Figure 2 The upper die 1 is provided with a stepped hole, and the aperture change forms a stroke limit of the guide pillar 9. The flat die plate 11 is provided with a positioning structure matched with the shape of the end of the elastic element 4, and the positioning structure includes a spring positioning hole 13 and a threaded blind hole 14. The segmented aperture design of the stepped hole makes the guide pillar 9 be mechanically limited by the stepped surface during movement, so as to accurately control the extension height of the ejection mechanism. The spring positioning hole 13 and the threaded blind hole 14 fix the mounting seat of the elastic element 4 through threaded connection, preventing the elastic element 4 from being radially displaced during dynamic compression.

[0044] The boss 10 has a gradually decreasing cross-sectional size from the bottom to the top, and its shape includes but is not limited to a circular cone and an ellipse. Its side surface and bottom surface are smoothly transitioned, and the distance L1 between adjacent bosses 10 is greater than or equal to 0.5 times the minimum width W1 of the boss 10. During the clamping process, the tapering feature of the circular cone structure causes the molten material to expand radially when it contacts the boss 10, and the smooth transition avoids shear fracture of the material at the corner. When the distance between adjacent bosses 10 satisfies L1≥0.5W1, the material forms a continuous sliding channel between adjacent bosses 10, preventing local thickness unevenness caused by blocked sliding. During the molding stage, the tapering structure of the boss 10 cooperates with the spacing constraint to make the material form a uniform thickness distribution in the cavity, while avoiding the bridging defect between multiple cap features.

[0045] Compared with the prior art, the traditional mold uses an equal-section boss 10 and the spacing is not considered for the material sliding requirement, which causes the molten material to rapidly cool and form a hard shell after contacting the boss 10, hindering the material deformation and sliding. The present scheme optimizes the geometric shape and spatial layout of the boss 10 to complete the filling of the molding space when the material still maintains the sliding property, effectively solving the bridging and breaking problems of the multi-cap part during molding. The controllable sliding of the molten composite material between multiple bosses 10 is realized, the material solidification caused by rapid local cooling during the molding process is eliminated, the contour accuracy and wall thickness uniformity of the combined cap-shaped end cover are ensured, and the molding qualification rate of the complex structure thermoplastic composite part is significantly improved.

[0046] The side wall and bottom surface of the cavity are connected by a continuous curved surface, which has an equal gap fit with the boss 10, and the working surface of the thickness limiting step 6 is parallel to the parting surface of the upper die 1. A material sliding guide slope is arranged between the cavity and the thickness limiting step 6. During the clamping process, the molten material is first subjected to the pre-clamping action of the ejection mechanism, and then the boss 10 gradually enters the cavity. The continuous curved surface transition of the cavity side wall can avoid shear fracture of the material at the corner, and the equal gap fit ensures that the thickness of the material is uniform during sliding. When the material contacts the thickness limiting step 6, the sliding guide slope guides the material to the end of the cavity, and the parallel arrangement of the step working surface and the upper die 1 parting surface ensures that the material forms accurate thickness control in the closing stage. Through the cooperation of the continuous curved surface and the guide slope, the material can complete the filling according to the predetermined path, avoiding the bridging or local accumulation between multiple cap features.

[0047] The above technical solution eliminates stress concentration through a continuous curved surface, improves the sliding path through a guide slope, and realizes size control through the thickness limiting step 6, solving the problem of uneven sliding during the molding process of the combined cap-shaped part. The bridging phenomenon that occurs when multiple cap-shaped features are molded at the same time is effectively avoided, the sliding resistance of the material in the complex cavity is reduced, and it is ensured that the molten material can fully fill each area of the cavity, ultimately obtaining a combined cap-shaped part with clear contours, uniform thickness and no cracking defects.

[0048] The upper die 1 is provided with a heating channel 2 perpendicular to the main stress direction of the mold, and the lower die 12 is provided with a temperature monitoring channel 3 corresponding to the position of the boss 10, and the detection end is close to the surface of the cavity. The upper die 1 and the lower die 12 are provided with symmetrical distribution of mold fixing structures 8 at the edges of the respective parting surfaces.

[0049] The heating channel 2 and the temperature monitoring channel 3 are respectively provided with at least two electric heating pipes and thermocouples in the upper die 1, and the thermocouples and the electric heating pipes are installed in the upper die 1 through the heating channel 2.

[0050] The heating channel 2 refers to a through hole in the mold for arranging heating elements, which can be realized by a cylindrical hole extending perpendicular to the stress direction of the mold. Its function is to provide installation space for the electric heating pipe and guide the heat to diffuse uniformly along the main body of the mold. The temperature monitoring channel 3 refers to a through hole for arranging temperature sensors, which can be realized by an elongated hole distributed parallel to the heating channel 2. Its detection end is close to the surface of the cavity, and its function is to monitor the temperature change of the contact area between the mold and the material in real time. The electric heating pipe refers to a rod-shaped heating element that converts electrical energy into heat energy. Its function is to transfer controllable heat to the mold through the heating channel 2 to maintain the temperature of the mold and keep the temperature difference between the material and the mold. The thermocouple refers to a sensor that measures temperature based on the thermoelectric effect. Its function is to collect mold surface temperature data through the temperature monitoring channel 3 and feed back to the control system.

[0051] The upper mold 1 has two or more independently distributed heating channels 2, each equipped with an electric heating element. The uniform surface temperature of the mold is controlled by adjusting the heating power in different areas. Temperature monitoring channels 3 are spaced apart from the heating channels 2. After the thermocouples are installed, their sensing ends extend to the vicinity of the cavity surface, monitoring temperature changes in the material contact area in real time. The coordinated operation of the heating channels 2 and the temperature monitoring channels 3 allows the mold to dynamically adjust the heating power during mold closing, preventing excessively high or low temperatures that could lead to premature material curing or poor sliding.

[0052] This solution integrates multiple heating channels 2 and temperature monitoring channels 3 into the upper mold 1 to achieve real-time control of the mold temperature field during the molding process. It can precisely control the uniform temperature distribution on the working surface of the mold, ensuring that the molten material maintains uniform sliding properties when filling the cavity, thereby reducing the crystallization rate and cooling rate.

[0053] The boss 10 and the upper mold 1 have a rounded transition. The height H1 of the boss 10 is ≤ 1.5 × the minimum width W1 of the boss 10 projection. The bottom spacing L1 of the boss 10 is ≥ 0.5 × W1. 6 mm ≤ the diameter D1 of the heating tube blind hole is ≤ 10 mm. 0.85 × mold width W2 ≤ the depth L2 of the heating tube blind hole is ≤ 0.9 × mold width W2. 2 mm ≤ the diameter D2 of the temperature probe hole is ≤ 5 mm. The depth L3 of the temperature probe hole is ≈ 0.5 × mold width W1. The temperature probe hole is located above the boss 10.

[0054] A method for preparing thermoplastic composite end caps,

[0055] Includes: a) Pre-adjustment stage: setting the height difference between the working plane of the ejection mechanism and the forming surface of the upper mold 1;

[0056] b) Mold closing initialization stage: The ejection mechanism first contacts the material and forms a pre-clamping area;

[0057] c) Main forming stage: The boss 10 intervenes to make the material slide into the cavity along a preset path;

[0058] d) Cavity closing stage: The ejection mechanism resets to allow the material to completely fill the molding space;

[0059] e) Pressure holding and shaping stage: Maintain the clamping force until the material is completely solidified.

[0060] In step b), the pre-clamping force formed by the ejection mechanism and the lower mold 12 is less than the final mold closing pressure;

[0061] In step c), the material sliding direction forms an angle with the tapering direction of the boss 10;

[0062] In step d), the resetting speed of the ejection mechanism is coordinated with the material cooling rate.

[0063] The specific steps for using a hot stamping die for a combined cap-shaped thermoplastic composite end cap disclosed in this invention are as follows:

[0064] (1) Mold cleaning: Use fine sandpaper to clean the impurities on the mold surface, and then use a cleaning agent to soak a degreased cloth to wipe the inner surface of the mold to ensure that there is no oil or impurities on the mold surface.

[0065] (2) Mold treatment: Use a high-temperature resistant release agent to soak a degreased cloth, and then wipe the mold surface multiple times, with an interval of no less than 10 minutes each time, to ensure that the release agent coating on the mold surface is uniform and reliable.

[0066] (3) Mold assembly: First, screw the guide post 9 into the flat template 11, then insert the spring into the guide post 9, and then insert the other end of the guide post 9 into the stepped hole of the upper mold 1 from the surface direction of the upper mold 1. Next, press the flat template 11 inward so that the guide post 9 protrudes from the stepped hole. Finally, screw the nut on the end of the guide post 9 from the groove of the upper mold 1, and adjust the position of the nut 7 so that the flat template 11 is slightly higher than the boss 10 of the upper mold 1.

[0067] (4) Mold installation: Place the mold after mold closing into the corresponding position on the hot press table, then insert the pressure block into the side groove of the upper and lower molds 12, and then use screws to fix the mold on the hot press table in conjunction with the pressure block.

[0068] (5) Mold heating: Insert the heating tube and thermocouple into the corresponding holes of the mold and fix them. Then, heat the mold to the target temperature range while the mold is closed, and adjust the heating power in time according to the monitored temperature.

[0069] (6) Composite material heating: Cut the composite material into sheets, punch holes at the edges for hanging springs, and then hang the springs in the frame controlled by the robot. The robot is then controlled to extend the frame into the infrared heating furnace for heating.

[0070] (7) Stamping: The composite material heated to above the melting temperature is quickly transferred to the corresponding position between the upper and lower molds 12, and then the mold is quickly closed. During the hot stamping process, the flat template 11 of the ejector mechanism first contacts the composite material, and then cooperates with the lower mold 12 to clamp the composite material. As the mold closes, the composite material shrinks and deforms inward under the action of the boss 10 of the upper mold 1 to form the target part 5.

[0071] (8) Mold opening and shaping: After the hot stamping of the composite material parts is kept warm and pressed in the mold for a period of time, the hot stamping mold is opened, the stamped thermoplastic composite material parts are taken out, and then the thermoplastic composite material parts are machined to the target size.

[0072] In this embodiment, a carbon fiber reinforced polyaryletherketone thermoplastic composite end cap with two round cap-shaped features is prepared. The layup of the carbon fiber reinforced polyaryletherketone thermoplastic composite is [0° / 90°]. 5s The thickness is approximately 1.4mm. The specific process is as follows:

[0073] Step 1: Use a jet water jet cutting device to cut the composite material laminate into rectangular composite material sheets with a size of 280mm×180mm.

[0074] Step 2: Drill holes around the perimeter of the sheet, with 5 holes evenly distributed along the long side and 3 holes along the short side. The hole diameter is 3mm, and the distance between the round holes and the edge of the sheet is 5mm.

[0075] Step 3: Use 2000-grit sandpaper to clean impurities from the mold surface, and then use anhydrous ethanol or acetone to soak a degreasing cloth and wipe the inner surface of the mold to ensure that the mold surface is free of oil and impurities.

[0076] Step 4: Soak a degreased cloth with a commercially available high-temperature resistant mold release agent (temperature resistance > 400℃), and then wipe the mold surface 3 times, with an interval of no less than 10 minutes between each wipe to ensure that the mold release agent coating on the mold surface is uniform and reliable.

[0077] Step 5: Screw the guide post 9 into the flat template 11, then insert the spring into the guide post 9. Next, insert the other end of the guide post 9 into the stepped hole of the upper mold 1 from the surface direction of the upper mold 1. Then press the flat template 11 inward so that the guide post 9 protrudes from the stepped hole. Finally, screw the nut onto the end of the guide post 9 from the groove of the upper mold 1, and adjust the position of the nut 7 so that the flat template 11 is 1~6mm higher than the boss of the upper mold 1.

[0078] Step 6: Place the mold after mold closing into the corresponding position on the hot press table, then insert the pressure block into the side groove of the upper and lower molds 12, and then use screws to fix the mold on the hot press table with the pressure block. Then insert the heating tube and thermocouple into the corresponding hole of the mold and fix them. Then heat the mold to 240℃ in the mold closing state and keep the temperature constant in the range of 235℃~245℃.

[0079] Step 7: Hang one end of the high-temperature resistant spring on the composite material sheet and the other end on the frame controlled by the robot arm. Select a spring of appropriate length and stretch it slightly to ensure that the tension is about 0N~10N.

[0080] Step 8: Control the robot to extend the frame into the infrared heating furnace for heating. The composite material sheet should be 15cm away from the upper and lower heating modules. Set the infrared furnace temperature to 540℃ and the heating time to 1min~3min.

[0081] Step 9: Quickly transfer the composite material sheet heated to above the melting temperature to the corresponding position between the upper and lower molds 12, and then quickly close the mold. During the hot stamping process, the flat template 11 of the ejection mechanism first contacts the composite material, and then cooperates with the lower mold 12 to clamp the composite material. As the mold closes, the composite material shrinks and deforms inward under the action of the boss 10 of the upper mold 1 to form the target part 5. Then close the mold and keep it warm for 5 to 10 minutes.

[0082] Step 10: After the heat preservation and pressure holding time is completed, open the hot stamping mold, take out the stamped thermoplastic composite material parts, and then cut off the waste material at the edge of the composite material layer to process the thermoplastic composite material parts to the target size.

[0083] The carbon fiber reinforced polyaryletherketone thermoplastic composite end caps were tested after molding, and the results are shown below:

[0084] Appearance inspection: The outer surface of the end cap is smooth, without obvious scratches, dents and wrinkles, without obvious resin accumulation and glue deficiency, and the fibers are not obviously bent or broken; the cap-shaped indentation on the inner surface is smooth, without obvious scratches, dents and wrinkles, the plane area of ​​the inner surface in contact with the ejection mechanism is basically smooth, and the plane template of the ejection mechanism causes slight indentations.

[0085] Dimensional inspection: The thickness of the flat plate area of ​​the end cap is approximately 1.30mm~1.46mm, with a tolerance of no more than ±8%; the thickness of the bend radius (R area) of the end cap is approximately 1.27mm~1.44mm, with a tolerance of no more than ±10%; the depth of the indentation caused by the flat template of the ejection mechanism on the inner surface is ≤0.13mm; the unidirectional tape layup angle tolerance of the flat plate area is ≤±2°, and the layup fiber angle tolerance of the bend radius (R area) of the end cap is ≤±5°.

[0086] Quality inspection: The metallographic morphology of the rounded corner transition of the end cap is as follows: Figure 5 , Figure 6 As shown, the porosity is ≤2%.

[0087] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A combined cap-type thermoplastic composite end cap hot-stamping forming die, comprising: The target part, the upper die (1) and the lower die (12) are characterized in that: the upper die (1) is provided with at least two spaced hat-shaped bosses (10), and a retractable ejection mechanism is arranged between the bosses (10), which extends out of the working plane of the upper die (1) in the open die state, and the lower die (12) is provided with a cavity matched with the target part and a thickness limiting step (6), wherein when the die is closed, the ejection mechanism first contacts the molten composite material and forms clamping with the lower die (12), and finally forms a continuous closed molding space with the upper die (1), the ejection mechanism comprises: a flat die plate (11) whose contour is gap-matched with the bosses (10); at least two guide columns (9) whose one end is fixed to the flat die plate (11) and the other end penetrates the upper die (1); and elastic elements (4) which are sleeved on the guide columns (9) to provide pre-tightening force in the opening direction of the die, and the ejection mechanism further comprises: an adjusting nut (7) which is threadedly connected with the guide column (9) to control the extension amount of the guide column (9).

2. The combined cap type thermoplastic composite end cover hot-stamping forming die according to claim 1, characterized in that: The upper die (1) is provided with a stepped hole, and the hole diameter changing part forms the stroke limiting of the guide column (9); the flat die plate (11) is provided with a positioning structure matched with the shape of the end of the elastic element (4), and the positioning structure comprises a spring positioning recess (13) and a threaded blind hole (14).

3. The combined cap type thermoplastic composite end cover hot-stamping forming die according to claim 1, characterized in that: The boss (10) has a cross-sectional size gradually decreasing from the bottom to the top, and the side surface and the bottom surface are transitioned by a smooth curved surface, and the distance L1 between adjacent bosses (10) is greater than or equal to 0.5 times the minimum width W1 of the boss (10).

4. The combined cap type thermoplastic composite end cover hot-stamping forming die of claim 1, wherein: The side wall and the bottom surface of the cavity are transitioned by a continuous curved surface, the contour of which is gap-matched with the boss (10), the working surface of the thickness limiting step (6) is parallel to the parting surface of the upper die (1), and a material sliding guide slope is arranged between the cavity and the thickness limiting step (6).

5. The hot stamping die for a combined cap-shaped thermoplastic composite end cap according to claim 1, characterized in that: The upper die (1) is provided with a heating channel (2) perpendicular to the main stress direction of the die, and the lower die (12) is provided with a temperature monitoring channel (3) corresponding to the position of the boss (10), and the detection end is close to the surface of the cavity, and the upper die (1) and the lower die (12) are provided with symmetrically distributed die fixing structures (8) at the edges of the respective parting surfaces.

6. A combined cap type thermoplastic composite end cover hot press forming die according to claim 5, characterized in that: The heating channel (2) and the temperature monitoring channel (3) are at least two respectively, the upper die (1) is provided with an electric heating pipe and a thermocouple, and the thermocouple and the electric heating pipe are installed on the upper die (1) through the heating channel (2).

7. A method of manufacturing a thermoplastic composite end cap using the mould of any one of claims 1 to 6, characterised by It comprises: a) pre-adjustment stage: set the height difference between the working plane of the ejection mechanism and the molding surface of the upper die; b) die closing initialization stage: the ejection mechanism first contacts the material and forms a regional pre-clamping; c) main molding stage: the boss intervenes to make the material slide along the preset path to the inside of the cavity; d) cavity closing stage: the ejection mechanism resets to make the material completely fill the molding space; e) pressure maintaining and shaping stage: maintain the clamping force until the material is completely cured.

8. The method of claim 7, wherein: the pre-clamping force formed by the ejection mechanism and the lower die in step b) is less than the final clamping pressure. The angle between the material sliding direction and the taper direction of the boss is formed in step c; The reset speed of the ejection mechanism is coordinated with the material cooling rate in step d.

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