Rapid molding system and method for thermoplastic composite material

Abstract

The invention provides a thermoplastic composite material rapid forming system and method, and belongs to the technical field of composite material forming. The system comprises a lamination laying device, a three-dimensional positioning device, a rapid preheating device, a special-shaped stamping device and a cutting post-processing device which are sequentially arranged in the conveying direction of a conveying track. A plane base tray moving along the conveying track is arranged on the conveying track; the plane base tray comprises an edge frame and a central plane, and the central plane is formed by splicing a plurality of framework rod bodies capable of being pulled away; the three-dimensional positioning device comprises a clamping and fixing strip and an upper and lower surface pre-tightening device; the special-shaped stamping device comprises an upper die and a lower die, and the upper die and the lower die are located above and below the conveying rail correspondingly and can move oppositely. Through the linkage design of the plane base tray, the conveying track and the special-shaped stamping device, rapid automatic forming is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material molding, and in particular relates to a thermoplastic composite material rapid molding system and method. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] High-performance fiber composite materials and special-shaped materials are increasingly used in transportation, power facilities, oil extraction and other industrial fields. Due to the characteristics of the resin matrix, thermosetting resin-based composite materials can only be processed once and their products cannot be recycled. Therefore, with the continuous research and development of fiber composite resin matrices, thermoplastic resin-based composite materials are gradually being recognized by people. Their resin matrices can be repeatedly plasticized and molded, and have many characteristics such as fast molding speed, recyclability, and excellent comprehensive mechanical properties. Their products are increasingly used in plate processing, special-shaped material molding, etc.

[0004] At present, the molding of thermoplastic composite materials mainly uses prepreg intermediates for product processing. The links in the molding process are relatively discrete and have not yet formed the level of assembly line operation. The product processing efficiency is lower than that of thermosetting composite materials. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a system and method for rapid prototyping of thermoplastic composite materials, to realize a continuous integrated assembly line equipment system with multiple processes linked including laying, positioning, preheating and rapid stamping, and to provide a technical basis for the rapid processing and preparation of thermoplastic fiber composite materials.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] In a first aspect, a thermoplastic composite material rapid prototyping system comprises a stacking device, a stereo positioning device, a rapid preheating device, a special-shaped stamping device and a post-cutting processing device which are sequentially arranged along a conveying direction of a conveying track;

[0008] A plane base tray is arranged on the conveying track and moves along the conveying track; the plane base tray includes an edge frame and a center plane, and the center plane is formed by splicing a plurality of detachable skeleton rods;

[0009] The stereo positioning device comprises a clamping and fixing strip and an upper and lower surface pre-tightening device, wherein the clamping and fixing strip can be clamped at the edge frame position of the planar base tray, and the upper and lower surface pre-tightening device covers and clamps at the central plane position of the planar base tray;

[0010] The special-shaped punching device comprises an upper die and a lower die, wherein the upper die and the lower die are respectively located above and below the conveying track and can move toward each other.

[0011] Optionally, the conveying track includes a first track and a second track, the first track sequentially connects the stacking laying device, the stereo positioning device, the rapid preheating device and the special-shaped stamping device, and the second track connects the special-shaped stamping device and the post-cutting processing device.

[0012] Optionally, a planar base tray moving along the conveying direction is arranged on the first track, and a lower mold moving along the conveying direction is arranged on the second track.

[0013] Optionally, the stacking device includes a first manipulator and a grabbing suction cup, and the grabbing suction cup is arranged at the end of the first manipulator.

[0014] Optionally, the rapid preheating device includes an upper heating module, a lower heating module and a thermal cycle device, the upper heating module is located above the conveying track, the lower heating module is located below the conveying track, and the thermal cycle device is located on the side of the conveying track.

[0015] Optionally, the upper heating module, the lower heating module and the thermal cycle device are located in a preheating cavity, and the conveying track passes through the preheating cavity.

[0016] Optionally, the post-cutting processing device includes a second robot and a cutting device, and the cutting device is arranged at the end of the second robot.

[0017] Optionally, the cutting device is a water jet.

[0018] Optionally, the upper mold and the lower mold are arranged in a heat-insulating box, and a heating device is provided in the heat-insulating box.

[0019] Optionally, the post-cutting processing device is located in an operating room.

[0020] In a second aspect, a thermoplastic composite material rapid prototyping method based on the above-mentioned thermoplastic composite material rapid prototyping system comprises the following steps:

[0021] S1, the stacking device stacks the prepreg fabric on the flat base tray, and the flat base tray moves along the conveying track to the stereo positioning device;

[0022] S2, in the stereo positioning device, the clamping fixing strip clamps the prepreg fabric located at the edge frame position, the upper and lower surface pretensioning devices clamp the prepreg fabric at the center plane position and then release it, and the flat base tray moves to the rapid preheating device;

[0023] S3, in the rapid preheating device, the prepreg fabric is heated to the preheating temperature, and the flat base tray moves to the special-shaped stamping device;

[0024] S4, in the special-shaped stamping device, the prepreg fabric is moved from the upper surface of the flat base tray to the upper surface of the lower mold, and the upper mold completes the stamping and forming. After the clamping and fixing strips are removed, the lower mold supports the stamped product to be cut and moves it to the post-cutting processing device;

[0025] S5, in the post-cutting processing device, the thermoplastic prepreg is cut into products after stamping.

[0026] Optionally, in S1, in the stacking device, a single-layer thermoplastic prepreg fabric cut to a set size is fixed at multiple points by a grabbing suction cup and then pushed to the surface of a flat base tray by a first manipulator. A manipulator repeats grabbing and pushing according to a set stacking sequence to obtain a set stacking structure.

[0027] Optionally, in S2, the upper and lower pre-tightening devices are released after the exhaust and pre-tightening fixing process of the pre-impregnated fabric are synchronously realized in a pulse plus pressure relief manner.

[0028] Optionally, in S4, after the skeleton rod body of the plane base tray is pulled out from the plane base tray, a gap is formed at the center plane position, and the lower mold rises from the gap in the center plane to a height flush with the edge frame.

[0029] Optionally, in S5, the second robot uses a water jet to cut along the edge of the lower mold.

[0030] Optionally, the tightening of the clamping and fixing strips at the edge frame position in S2, the extraction of the skeleton rod body of the plane base tray in S4, the removal of the clamping and fixing strips and the installation of the skeleton rod body are manually completed by the operator.

[0031] The beneficial effects of the present invention are:

[0032] The present invention provides a thermoplastic composite material rapid prototyping equipment, which specifically includes five parts: a stacking device, a stereo positioning device, a rapid preheating device, a special-shaped stamping device, and a post-cutting processing device. Among them, the plane base tray includes a detachable skeleton rod body, which is further positioned by an edge frame and a clamping fixing strip after being disassembled. The cavity position after the disassembled skeleton rod body can be used for the mold closing of the upper mold and the lower mold. After the mold closing is completed, the product transformed from the prepreg fabric is transferred to the lower mold for further transportation. Rapid automated molding is achieved by designing the relative positions of the plane base tray, the conveying track, and the special-shaped stamping device and the linkage design between them. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0034] Figure 1 It is a schematic diagram of the structure of the flat base tray in Example 1 of the present invention from a top view.

[0035] Figure 2 It is a schematic diagram of the structure of the flat base tray in Example 1 of the present invention from a top view.

[0036] Figure 3 It is a schematic diagram of the structure of the transmission track in Example 1 of the present invention.

[0037] Figure 4 It is a schematic structural diagram of the lamination laying device in Example 1 of the present invention.

[0038] Figure 5 It is a schematic diagram of the structure of the rapid preheating device in Example 1 of the present invention.

[0039] Figure 6 It is a schematic structural diagram of the special-shaped stamping device in Example 1 of the present invention.

[0040] Figure 7 It is a structural schematic diagram of the post-cutting processing device in Example 1 of the present invention.

[0041] Among them: 1. prepreg fabric; 2. flat base tray; 21. slider; 22. edge frame; 23. center plane; 231. skeleton rod; 3. stamping product; 4. first manipulator; 5. grabbing suction cup; 6. second manipulator; 7. clamping fixing strip; 71. clamping positioning guide rail; 8. cutting device; 9. upper surface pre-tightening device; 91. pre-tightening hydraulic power system; 10. lower surface pre-tightening device; 101. pre-tightening suction cup; 11. first track; 12. second track; 13. upper heating module; 131. pre-heating cavity; 14. lower heating module; 15. thermal cycle device; 16. operating room; 17. lower mold; 18. upper mold; 19. insulation box; 20. molding heating device. DETAILED DESCRIPTION

[0042] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0043] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0044] Example 1

[0045] A thermoplastic composite material rapid prototyping system comprises a stacking laying device, a stereo positioning device, a rapid preheating device, a special-shaped stamping device and a post-cutting processing device which are sequentially arranged along the conveying direction of a conveying track.

[0046] The conveying track includes a first track 11 and a second track 12. The first track 11 is connected in sequence to a stacking device, a stereo positioning device, a rapid preheating device and a special-shaped punching device, and the second track 12 is connected to the special-shaped punching device and a post-cutting processing device.

[0047] like Figure 1As shown, a plane base tray 2 moving along the conveying track is arranged on the conveying track; first tracks 11 are respectively arranged on both sides of the plane base tray 2, and the plane base tray 2 is slidably connected with the first tracks 11 through multiple sliders 21 on both sides, and can move along the direction of the first tracks 11; the plane base tray 2 includes an edge frame 22 and a center plane 23, and the center plane 23 is spliced ​​by multiple detachable skeleton rods 231, and the upper surfaces of the multiple skeleton rods 231 constitute the center plane 23, and the center plane 23 has holes arranged in a matrix and penetrating from top to bottom, and the skeleton rods 231 can be pulled out from the plane base tray 2;

[0048] like Figure 2 As shown, a flat base tray 2 moving along the conveying direction is arranged on the first track 11, and a lower mold 17 moving along the conveying direction is arranged on the second track 12; in the special-shaped stamping device, the moving ranges of the first track 11 and the second conveying track 12 overlap, so that the flat base tray 2 and the lower mold 17 can overlap from the top and bottom directions. Figure 1 After the plurality of skeleton rods 231 of the flat base tray 2 are drawn out, the central plane 23 becomes a cavity, so that Figure 2 The lower mold 17 can rise from the central plane 23 to a height flush with the edge frame 22 , and at this time the prepreg fabric 1 is moved from the upper surface of the flat base tray 2 to the upper surface of the lower mold 17 .

[0049] like Figure 3 As shown, the stacking device includes a first manipulator 4 and a grabbing suction cup 5. The grabbing suction cup 5 is arranged at the end of the first manipulator 4. When the unloaded flat base tray 2 moves to the stacking device along the first track 11, the single-layer thermoplastic prepreg fabric cut to a set size is fixed at multiple points by the grabbing suction cup 5 and then pushed to the surface of the flat base tray 2 by the first manipulator 4. The first manipulator 4 repeats grabbing and pushing according to the set stacking sequence to obtain the prepreg fabric 1 with a set stacking structure.

[0050] like Figure 4As shown, the stereo positioning device includes a clamping and fixing strip 7, an upper surface pre-tightening device 9 and a lower surface pre-tightening device 10. The clamping and fixing strip 7 can be clamped at the edge frame 22 position of the flat base tray 2. After the clamping and fixing strip 7 is moved to the set position through the clamping and positioning guide rail 71, it is tightened with a pre-tightening spring to ensure the edge clamping force; the upper surface pre-tightening device 9 and the lower surface pre-tightening device 10 can cover and clamp at the center plane 23 position of the flat base tray 2; the upper surface of the lower surface pre-tightening device 10 is provided with a plurality of pre-tightening suction cups 1 01, the pre-tightening suction cup 101 provides a pre-tightening force on the lower surface of the prepreg fabric 1 by vacuum adsorption through the holes that pass through the upper and lower parts of the center plane 23. The upper surface pre-tightening device 9 is driven by the pre-tightening hydraulic power system 91. The hydraulic power system can drive the square pressure head of the upper surface pre-tightening device 9 to apply an adjustable pre-tightening force of 0.1 to 1.0 MPa to the prepreg fabric 1 below. The entire upper and lower pre-tightening device can realize the simultaneous implementation of the exhaust and pre-tightening fixing process between the layers of the prepreg fabric 1 in a pulse plus pressure relief manner.

[0051] like Figure 5 As shown, the rapid preheating device includes an upper heating module 13, a lower heating module 14 and a thermal cycler 15, the upper heating module 13 is located above the conveying track 1, the lower heating module 14 is located below the first track 11, and the thermal cycler 15 is located on the side of the first conveying track 1; and the upper heating module 13, the lower heating module 14 and the thermal cycler 15 are located in a preheating cavity 131, and the first track 1 passes through the preheating cavity 131; the upper and lower heating modules include infrared radiation heating elements for heating the prepreg fabric 1 to a set preheating temperature in the preheating cavity 131, and the thermal cycler 15 is used to ensure that the temperature of each position in the preheating cavity 131 is relatively consistent; the thermal cycler 15 is a blast thermal cycler, and the blast direction avoids blowing air between the layers of the prepreg fabric 1.

[0052] like Figure 6 As shown, the special-shaped stamping device includes an upper mold 18 and a lower mold 17, the upper mold 18 is located above the second track 12, the lower mold 17 can move along the second track 12, and the upper mold 18 and the lower mold 17 can move toward each other to complete the mold closing action, so that the prepreg fabric 1 clamped between the upper mold 18 and the lower mold 17 is transformed into a stamping product 3 to be cut, the upper mold 18 and the lower mold 17 are arranged in an insulation box 19, and the insulation box 19 is provided with a molding heating device 20. Since the force of the mold closing action is relatively large, a supporting device is arranged under the lower mold 17, and the supporting device is connected to the ground to limit the position of the lower mold 17. After the stamping is completed, the lower mold 17 is separated from the supporting device and moves along the second track 12 to the post-cutting processing device.

[0053] The upper mold 18 and the lower mold 17 are molded and stamped at the cavity position of the central plane 23, and then the clamping and fixing strips 7 on the flat base tray 2 are removed; the formed prepreg fabric 1 is completely separated from the flat base tray 2. Figure 2 The edge frame 22 of the flat base tray 2 is opened in the direction in which the second conveying track 12 continues to move ( Figure 2 The upper side of the middle edge frame 22 has an opening, so it will not block the lower mold 17 from moving out of the cavity of the center plane 23.

[0054] like Figure 7 As shown, the post-cutting processing device includes a second manipulator 6 and a cutting device 8. The cutting device 8 is arranged at the end of the second manipulator 6, and the post-cutting processing device is located in the operating room 16; the cutting device 8 is a water jet, which is used to cut along the edge of the lower mold 17 to obtain the cut stamping product 3.

[0055] The thermoplastic composite material rapid prototyping method based on the thermoplastic composite material rapid prototyping system of this embodiment includes the following steps:

[0056] S1, such as Figure 3 As shown, in the stacking device, a single-layer thermoplastic prepreg fabric cut to a set size is fixed at multiple points by a grabbing suction cup 5 and then pushed to the surface of a flat base tray 2 by a first manipulator 4. The first manipulator 4 repeatedly grabs and pushes according to a set layering sequence to obtain a prepreg fabric 1 with a set layering structure. The flat base tray 2 moves along a first track 11 to a three-dimensional positioning device;

[0057] S2, such as Figure 4 As shown, in the stereo positioning device, the clamping and fixing strip 7 clamps the prepreg fabric 1 located at the edge frame 22, and the upper and lower surface pre-tightening devices clamp the prepreg fabric 1 at the center plane 23. The upper and lower pre-tightening devices simultaneously realize the exhaust and pre-tightening process of the prepreg fabric 1 in a pulse plus pressure relief manner and then release, and the flat base tray 2 carries the clamping and fixing strip 7 and moves to the rapid preheating device;

[0058] S3, such as Figure 5 As shown, in the rapid preheating device, the prepreg fabric 1 is heated to the preheating temperature by the upper heating module 13 and the lower heating module 14 in the preheating cavity 131, and the flat base tray 2 moves to the special-shaped stamping device;

[0059] S4, such as Figure 6As shown, in the special-shaped stamping device, the lower mold 17 moves to below the center plane 23 of the flat base tray 2, and after the skeleton rod 231 of the flat base tray 2 is pulled out from the flat base tray 2, a gap is formed at the center plane 23, and the lower mold 17 rises from the gap of the center plane 23 to a height flush with the edge frame 22. At this time, the prepreg fabric 1 is moved from the upper surface of the flat base tray 2 to the upper surface of the lower mold 17, and the upper mold 18 and the lower mold 17 are molded together in the gap of the center plane 23 to form a stamping product 3 to be cut. Then, the clamping fixing strip 7 on the edge frame 22 is removed, and the upper mold 17 is separated from the stamping product 3, and the stamping product 3 supported by the lower mold 17 moves along the second track 12 to the post-cutting processing device;

[0060] S5, such as Figure 7 As shown, in the post-cutting processing device, the second manipulator 6 uses a water jet to cut along the edge of the lower mold 17, so that the thermoplastic prepreg after stamping is cut into stamping products 3.

[0061] In S4, after the prepreg fabric 1 is moved from the upper surface of the flat base tray 2 to the upper surface of the lower mold 17, the flat base tray 2 is moved back to the stacking placement device along the first track 11, and the skeleton rod 231 is installed to form a center plane 23 to continue the next product molding work.

[0062] Among them, the tightening work of the clamping fixing strip 7 at the position of the edge frame 22 in S2, the extraction work of the skeleton rod body 231 of the plane base tray 2 in S4, the removal work of the clamping fixing strip 7 and the installation work of the skeleton rod body 231 are completed manually by the operator.

[0063] Example 2

[0064] The method for rapid prototyping of thermoplastic composite materials using the thermoplastic composite material rapid prototyping system of Example 1 is different from that of Example 1 in that: in S2, the upper preload device applies a preload force of 1 MPa, and in S4, the lower mold 17 and the upper mold are closed at a pressure of 10 MPa to complete the stamping process for 10 seconds.

[0065] Furthermore, since the stamping product 3 in this embodiment has a relatively large deformation degree, the clamping and fixing strips 7 are manually removed in S4 before the mold is closed.

[0066] Example 3

[0067] The method for rapid prototyping of thermoplastic composite materials using the thermoplastic composite material rapid prototyping system of Example 1 is different from that of Example 1 in that: in S2, the upper preload device applies a preload force of 0.5 MPa, and in S4, the lower mold 17 and the upper mold are closed at a pressure of 5 MPa to complete the stamping process for 12 seconds.

[0068] Example 4

[0069] The method for rapid prototyping of thermoplastic composite materials using the thermoplastic composite material rapid prototyping system of Example 1 is different from that of Example 1 in that: in S2, the upper preload device applies a preload force of 0.9 MPa, and in S4, the lower mold 17 and the upper mold are closed at a pressure of 4 MPa to complete the stamping process in 7 seconds.

[0070] Example 5

[0071] The method for rapid prototyping of thermoplastic composite materials using the thermoplastic composite material rapid prototyping system of Example 1 is different from that of Example 1 in that: in S2, the upper preload device applies a preload force of 0.8 MPa, and in S4, the lower mold 17 and the upper mold are closed at a pressure of 6 MPa to complete the stamping process in 8 seconds.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A thermoplastic composite material rapid prototyping system, characterized in that: It includes a stacking device, a stereo positioning device, a rapid preheating device, a special-shaped punching device and a post-cutting processing device which are sequentially arranged along the conveying direction of the conveying track; A plane base tray is arranged on the conveying track and moves along the conveying track; the plane base tray includes an edge frame and a center plane, and the center plane is formed by splicing a plurality of detachable skeleton rods; The stereo positioning device comprises a clamping and fixing strip and an upper and lower surface pre-tightening device, wherein the clamping and fixing strip can be clamped at the edge frame position of the planar base tray, and the upper and lower surface pre-tightening device covers and clamps at the central plane position of the planar base tray; The special-shaped punching device comprises an upper die and a lower die, wherein the upper die and the lower die are respectively located above and below the conveying track and can move toward each other.

2. The thermoplastic composite material rapid prototyping system according to claim 1, characterized in that: The conveying track includes a first track and a second track, the first track sequentially connects the stacking device, the stereo positioning device, the rapid preheating device and the special-shaped punching device, and the second track connects the special-shaped punching device and the post-cutting processing device; Optionally, a planar base tray moving along the conveying direction is arranged on the first track, and a lower mold moving along the conveying direction is arranged on the second track.

3. The thermoplastic composite material rapid prototyping system according to claim 1, characterized in that: The stacking device comprises a first manipulator and a grabbing suction cup, wherein the grabbing suction cup is arranged at the end of the first manipulator.

4. The thermoplastic composite material rapid prototyping system according to claim 1, characterized in that: The rapid preheating device comprises an upper heating module, a lower heating module and a thermal cycle device, wherein the upper heating module is located above the conveying track, the lower heating module is located below the conveying track, and the thermal cycle device is located on the side of the conveying track; Optionally, the upper heating module, the lower heating module and the thermal cycle device are located in a preheating cavity, and the conveying track passes through the preheating cavity.

5. The thermoplastic composite material rapid prototyping system according to claim 1, characterized in that: The post-cutting processing device comprises a second manipulator and a cutting device, wherein the cutting device is arranged at the end of the second manipulator; Optionally, the cutting device is a water jet; Optionally, the post-cutting processing device is located in an operating room.

6. The thermoplastic composite material rapid prototyping system according to claim 1, characterized in that: The upper mold and the lower mold are arranged in a heat preservation box, and a heating device is arranged in the heat preservation box.

7. A thermoplastic composite material rapid prototyping method based on the thermoplastic composite material rapid prototyping system according to claims 1 to 6, characterized in that: The following steps are involved: S1, the stacking device stacks the prepreg fabric on the flat base tray, and the flat base tray moves along the conveying track to the stereo positioning device; S2, in the stereo positioning device, the clamping fixing strip clamps the prepreg fabric located at the edge frame position, the upper and lower surface pretensioning devices clamp the prepreg fabric at the center plane position and then release it, and the flat base tray moves to the rapid preheating device; S3, in the rapid preheating device, the prepreg fabric is heated to the preheating temperature, and the flat base tray moves to the special-shaped stamping device; S4, in the special-shaped stamping device, the prepreg fabric is moved from the upper surface of the flat base tray to the upper surface of the lower mold, and the upper mold completes the stamping and forming. After the clamping and fixing strips are removed, the lower mold supports the stamped product to be cut and moves it to the post-cutting processing device; S5, in the post-cutting processing device, the thermoplastic prepreg is cut into products after stamping.

8. The thermoplastic composite material rapid prototyping method according to claim 7, characterized in that: In S1, in the stacking device, a single-layer thermoplastic prepreg fabric cut to a set size is fixed at multiple points by a grabbing suction cup and then pushed to the surface of a flat base tray by a first manipulator. A manipulator repeats grabbing and pushing according to a set stacking sequence to obtain a set stacking structure.

9. The thermoplastic composite material rapid prototyping method according to claim 7, characterized in that: In S2, the upper and lower pre-tightening devices are released after the exhaust and pre-tightening fixing process of the pre-impregnated fabric are synchronously realized in a pulse plus pressure relief manner.

10. The thermoplastic composite material rapid prototyping method according to claim 7, characterized in that: In S4, after the skeleton rod of the plane base tray is pulled out from the plane base tray, a gap is formed at the center plane position, and the lower mold rises from the gap in the center plane to a height flush with the edge frame.

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