A forming device for forging pipe fittings
By designing forging and forming equipment and molds, the problems of low material utilization and low production efficiency in traditional cutting processes have been solved, achieving efficient and precise pipe joint forming and internal channel processing, thereby improving production efficiency and heat dissipation performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DONGGUAN YAOTENG HARDWARE PRODUCTS CO LTD
- Filing Date
- 2025-07-03
- Publication Date
- 2026-07-03
AI Technical Summary
Traditional cutting processes suffer from low material utilization, low production efficiency, and difficulty in meeting high precision requirements when machining pipe joints, especially when forming complex-shaped pipe joints and their internal channels. Existing forging technology has not yet been able to effectively solve these problems.
A forging and forming device including an upper die assembly and a lower die assembly is adopted. By utilizing the punch forming block and the die forging cavity structure, the metal pre-pressed part is plastically deformed in the die through the drive of the forging equipment, directly forming the pipeline joint and its internal channel. Combined with special die design such as forming groove, square protrusion and inclined protrusion, accurate forming and convenient demolding are ensured.
It improved material utilization, shortened processing cycle, accelerated production efficiency, ensured the accuracy of pipe joint shape and internal channels, optimized heat dissipation, and reduced production costs.
Smart Images
Figure CN224444463U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the technical field of metal forging, and in particular to a forming device for forging pipe joints. Background Technology
[0002] In modern industrial production, piping systems are widely used in various fields. Pipe fittings, as key components connecting pipelines, directly affect the operational stability of the entire piping system. Taking the connection structure of a large metal heat dissipation cavity as an example, metal pipe fittings, such as copper or aluminum fittings, are typically used. One end of these metal fittings connects to the liquid pipeline, and the other end connects to the heat dissipation metal plate. Internal channels are provided to allow coolant to flow between the liquid pipeline and the heat dissipation metal plate, thus achieving the heat dissipation function.
[0003] Traditionally, machining of the internal channels of pipe joints has been carried out using processes such as cutting. However, these processes have many drawbacks. From a material utilization perspective, cutting processes generate a large amount of metal debris, resulting in low material utilization and significant resource waste. In terms of machining efficiency, the cutting process is relatively cumbersome, requiring multiple clamping and cutting operations, leading to long machining cycles and low production efficiency. Moreover, the surface quality and dimensional accuracy after cutting are greatly affected by factors such as tool wear and cutting parameters, making it difficult to meet the increasingly demanding high-precision requirements.
[0004] To overcome the shortcomings of traditional processes, research on forging directly forming metal parts using forging technology has been increasing in recent years. Forging technology offers advantages such as high material utilization and high production efficiency. It can simultaneously form the overall shape of pipe fittings and attempt to form internal channels, reducing the use of cutting processes, thereby lowering production costs and improving efficiency. However, current forging technology still needs improvement. Many challenges remain in forming complex-shaped pipe fittings and ensuring the precision and quality of internal channels. For example, designing a reasonable mold structure that allows the metal pre-pressed part to deform uniformly during forging, accurately forming a pipe fitting with a cylindrical pipe connection end and a cubic cavity connection end, and directly forming the internal channel at the cavity connection end while ensuring the dimensional accuracy and surface quality of the channel, are urgent problems to be solved. Utility Model Content
[0005] To overcome the shortcomings mentioned above, this utility model aims to provide a technical solution that can solve the above problems.
[0006] This utility model provides a forging device for forging pipe fittings, including an upper die assembly and a lower die assembly arranged opposite to each other. The lower die assembly is installed on the worktable of the forging equipment, and the upper die assembly is installed on the slide beam of the forging equipment. The slide beam drives the upper die assembly to move to the lower die assembly, performing a forging operation on the metal pre-compression part placed in the lower die assembly. The lower die assembly is provided with a lower die clamping plate and a concave die plate fixed to each other. A forging die cavity is formed in the concave die plate, allowing the metal pre-compression part to be placed in the forging die cavity in advance. The upper die assembly is provided with an upper die pad plate and a convex die plate fixed to each other. A convex die forming block is provided at the end of the convex die plate facing the forging die cavity. The convex die forming block cooperates with the forging die cavity. Under the drive of the forging equipment, the metal pre-compression part is forged and formed, thereby forging and forming the corresponding metal fitting.
[0007] Furthermore: the central area of the punch forming block is provided with a forming groove, one end of which is provided with a semi-circular groove for forming a cylindrical pipe connection end of the connector, and the other end of which is provided with a square groove for forming a cubic cavity connection end of the connector; and the bottom of the square groove is provided with a square protrusion. During forging, the square protrusion squeezes the metal pre-pressed part, causing the material to flow to all sides, thereby forming a square channel with an opening size larger than the bottom at the cavity connection end.
[0008] Furthermore: the square protrusion is set with a bottom dimension larger than the top dimension, thereby forming an inclined angle along the demolding direction.
[0009] Furthermore, the top of the square protrusion is provided with a semi-circular protrusion. During forging, the semi-circular protrusion squeezes the metal pre-pressed part to form a semi-circular channel at the bottom of the square channel.
[0010] Furthermore: the central area of the forging die cavity is set as a forging cavity, which is used to accommodate the pre-pressed part and form the pre-pressed part into a connector; wherein, one end of the forging cavity is provided with a square cavity, which is used to form a cubic cavity connection end of the connector; the other end of the forging cavity is provided with a semi-circular cavity, which is used to form a cylindrical pipeline connection end of the connector.
[0011] Furthermore, a sloping protrusion is provided on the inner wall of the opening of the forging cavity, with one side forming the inner wall of the forging cavity and the other side inclined towards the periphery of the forging die cavity.
[0012] Furthermore: the four corners of the concave template are provided with guide protrusions, and the four corners of the convex template are provided with guide notches. The guide protrusions and guide notches cooperate with each other to guide the process during the forging operation.
[0013] Furthermore: the top of the guide protrusion is provided with a guide post, and the bottom of the guide notch is provided with a guide hole. The guide post and the guide hole cooperate with each other to guide the concave template and the convex template to be aligned at the center.
[0014] Compared with the prior art, the beneficial effects of this utility model are:
[0015] 1. Improved material utilization: This utility model uses the forging power of forging equipment to cause the metal pre-pressed parts to undergo plastic deformation in the mold, directly forming the pipe joint and its internal channels. Compared with the traditional cutting process, it greatly reduces material waste and significantly improves material utilization.
[0016] 2. Increased production efficiency: The forging process, which involves one-time forming, eliminates the need for multiple clamping and cutting operations as required by the machining process. This effectively shortens the processing cycle, significantly increases production efficiency, and facilitates large-scale industrial production.
[0017] 3. Precise forming of pipe joint shape: By setting forming grooves corresponding to the shape of the joint in the central area of the punch forming block of the punch template, including a semi-circular groove for forming the pipe connection end and a square groove for forming the cavity connection end, and setting matching forging cavities in the forging die cavity of the lower die assembly, including a semi-circular cavity and a square cavity, the metal pre-pressed parts can be precisely formed into the required pipe joint shape, ensuring the dimensional accuracy and shape accuracy of the product.
[0018] 4. Direct Forming of Internal Channels: A square protrusion is set at the bottom of the square groove. During forging, the square protrusion squeezes the metal pre-pressed part, causing the material to flow to all sides. This directly forms a square channel with an opening size larger than the bottom at the cavity connection end, reducing the subsequent machining process of the internal channel, further improving production efficiency, and ensuring the quality and precision of the channel.
[0019] 5. Facilitates demolding: The square protrusion is set with a bottom dimension larger than the top dimension, forming an inclined angle (such as 1°~5°) along the demolding direction. This makes it easy for the cavity connection part of the joint to be removed from the square groove after forging, effectively preventing the square protrusion from getting stuck in the square groove, eliminating the "locking" phenomenon caused by the vertical wall, and ensuring smooth demolding.
[0020] 6. Optimized channel structure: The semi-circular protrusion on the top of the square protrusion can compress the metal pre-pressed part during forging, forming a semi-circular channel at the bottom of the square channel. This semi-circular channel connects with the circular channel of the pipe connection end formed by subsequent processes, which is more conducive to the flow of heat dissipation liquid in the channel, optimizes the heat dissipation effect, and improves the performance of the product.
[0021] Therefore, this utility model reduces cutting and improves material utilization and production efficiency through forging and forming. Furthermore, it utilizes the mold structure to precisely form the shape of the pipe joint and the internal channel, thereby optimizing the forming effect and production benefits.
[0022] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0024] Figure 1 This is a schematic diagram of the overall structure of this utility model;
[0025] Figure 2 This is a cross-sectional schematic diagram of the upper mold assembly and the lower mold assembly of this utility model;
[0026] Figure 3 This is a structural schematic diagram of the concave template and pre-compression component of this utility model;
[0027] Figure 4 This is a schematic diagram of the forging die cavity and the inclined protrusion of this utility model;
[0028] Figure 5 This is a schematic diagram of the structure of the punch forming block and the forming groove of this utility model;
[0029] Figure 6 This is a schematic diagram of the square channel and semi-circular channel of the connector of this utility model;
[0030] Figure 7 This is a structural schematic diagram of the pipe connection end and cavity connection end of the connector of this utility model.
[0031] The reference numerals and names in the figure are as follows:
[0032] 10 Upper die assembly; 11 Upper die pad; 12 Punch plate; 13 Guide notch; 14 Guide hole; 20 Punch forming block; 21 Forming groove; 22 Semi-circular groove; 23 Square groove; 24 Square protrusion; 25 Semi-circular protrusion; 30 Lower die assembly; 31 Lower die clamping plate; 32 Concave plate; 33 Guide protrusion; 34 Guide post; 40 Forging die cavity; 41 Flash groove; 42 Forging cavity; 43 Inclined protrusion; 44 Square cavity; 45 Semi-circular cavity; 50 Pre-pressed part; 60 Connector; 61 Pipe connection end; 62 Cavity connection end; 63 Square channel; 64 Semi-circular channel. Detailed Implementation
[0033] The technical solutions in the embodiments of this utility model will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0034] Please see Figures 1 to 7 In this embodiment of the present invention, a forming device for forging pipe fittings includes an upper die assembly 10 and a lower die assembly 30 arranged opposite to each other. The lower die assembly 30 is installed on the worktable of the forging equipment, and the upper die assembly 10 is installed on the slide beam of the forging equipment. The slide beam drives the upper die assembly 10 to move to the lower die assembly 30 to perform forging operations on the metal pre-compression part 50 placed in the lower die assembly 30. The lower die assembly 30 is provided with a lower die clamping plate 31 and a concave template 32 fixedly connected to each other. A forging die cavity 40 is formed in the concave template 32, so that the metal pre-compression part 50 can be placed in the forging die cavity 40 in advance. The upper die assembly 10 is provided with an upper die pad plate 11 and a convex template 12 fixedly connected to each other. A convex forming block 20 is provided at one end of the convex template 12 facing the forging die cavity 40. The convex forming block 20 cooperates with the forging die cavity 40. Under the drive of the forging equipment, the metal pre-compression part 50 is forged and formed, thereby forging and forming the corresponding metal fitting 60.
[0035] Specifically, in the connection structure of some large metal heat dissipation cavities, metal pipe fittings, such as copper or aluminum fittings, are typically required. One end of the metal fitting 60 is usually used to connect to the liquid pipeline, and the other end is used to connect to the heat dissipation metal plate. A channel is formed inside the metal fitting to allow coolant to flow between the liquid pipeline and the heat dissipation metal plate. Traditional solutions typically use machining processes to process the internal channels of the pipe fitting, but machining processes have low material utilization, significant waste, and low processing efficiency. Therefore, it is necessary to utilize forging technology to directly forge the metal parts, forming both the overall shape of the pipe fitting and the internal channels, reducing the use of machining processes, thereby improving material utilization, avoiding material waste, and accelerating production efficiency.
[0036] This invention utilizes the forging power of a forging press to move the punch plate 12 of the upper die assembly 10 downwards, causing the punch forming block 20 to be pressed into the forging die cavity 40. This results in plastic deformation of the pre-pressed metal part 50, ultimately forming a pre-designed pipe joint. The pre-pressed metal part 50 is a transitional metal part obtained by controlling the metal flow after pre-pressing the metal blank using a pre-pressing die in the prior art, resulting in a material distribution state close to the final forging shape. This step employs a specially designed die cavity structure with a larger fillet radius (typically increased by 2-5 mm) and forging draft angle than the final forging die cavity, to reduce metal flow resistance.
[0037] The central area of the punch forming block 20 is provided with a forming groove 21. One end of the forming groove 21 is provided with a semi-circular groove 22, which is used to form a cylindrical pipe connection end 61 of the connector 60. The other end of the forming groove 21 is provided with a square groove 23, which is used to form a cubic cavity connection end 62 of the connector 60. The bottom of the square groove 23 is provided with a square protrusion 24. During forging, the square protrusion 24 squeezes the metal pre-pressed part 50, causing the material to flow to all sides, thereby forming a square channel 63 in the cavity connection end 62.
[0038] Specifically, the central area of the punch forming block 20 of the punch template 12 is provided with a forming groove 21, which includes a semi-circular groove 22 and a square groove 23. This forming groove 21 cooperates with the forging cavity 42 of the lower die assembly 30 to form the connector 60. Since one end of the pipe connector of the final product is cylindrical and mainly used to connect liquid pipes, it can be set as the pipe connection end 61 of the connector 60. The other end of the pipe connector is cubic and mainly used to connect heat dissipation metal plates, so it can be set as the cavity connection end 62 of the connector 60.
[0039] Secondly, in order to form the pipe connection end 61, a semi-circular groove 22 is preferably provided at one end of the forming groove 21, so as to cooperate with the forging cavity 42 to form a cylindrical pipe connection end 61. And in order to form the cavity connection end 62, a square groove 23 is preferably provided at the other end of the forming groove 21, so as to cooperate with the forging cavity 42 to form a cubic cavity connection end 62.
[0040] Furthermore, in order to directly form the internal channel at the cavity connection end 62, a square protrusion 24 is preferably provided at the bottom of the square groove 23. Under the forging action of the forging equipment, the square protrusion 24 extends towards the die forging cavity 42, thereby directly forming the corresponding square channel 63. This can reduce the intervention time of the cutting process, reduce material waste, and improve production efficiency.
[0041] The square protrusion 24 is set with a bottom dimension larger than the top dimension, thereby forming an inclined angle along the demolding direction.
[0042] Specifically, to facilitate the removal of the cavity connection portion of the forged connector 60 from the square groove 23, a certain inclination angle (e.g., 1°~5°) is preferably provided on the side wall of the square protrusion 24, making the bottom dimension of the square protrusion 24 larger than the top dimension. This prevents the square protrusion 24 from getting stuck in the square groove 23, facilitating demolding. It also eliminates the "locking" phenomenon caused by the vertical wall surface, ensuring that the square protrusion 24 can be smoothly demolded from the square groove 23.
[0043] Secondly, from the perspective of the molding effect of the connector 60, the square protrusion 24 with the draft angle will form a square channel 63 with an opening size larger than the bottom size. Since the channel size inside the pipe connection end 61 is smaller than the channel size of the cavity connection end 62, the aforementioned square channel 63 with special size also meets the above channel characteristics, making it easier for the heat dissipation liquid to flow in the channel.
[0044] The top of the square protrusion 24 is provided with a semi-circular protrusion 25. During forging, the semi-circular protrusion 25 extrudes the metal pre-pressed part 50, forming a semi-circular channel 64 at the bottom of the square channel 63.
[0045] Specifically, at the pipe connection end 61 of the connector 60, a corresponding circular channel (not shown in the figure) needs to be forged or machined in a subsequent process to allow the heat dissipation liquid to flow between the liquid pipe and the heat dissipation metal plate through the circular channel. Therefore, at the bottom of the square channel 63 of the cavity connection end 62, corresponding to the axial position of the pipe connection end 61, a corresponding semi-circular channel 64 can also be forged, so that the semi-circular channel 64 and the circular channel of the pipe connection end 61 formed in the subsequent process can be connected to each other to facilitate the flow of heat dissipation liquid.
[0046] The central area of the forging die cavity 40 is set as a forging cavity 42, which is used to accommodate the pre-pressed part 50 and form the pre-pressed part 50 into a connector 60. One end of the forging cavity 42 is provided with a square cavity 44, which is used to form a cubic cavity connection end 62 of the connector 60. The other end of the forging cavity 42 is provided with a semi-circular cavity 45, which is used to form a cylindrical pipe connection end 61 of the connector 60.
[0047] Specifically, to facilitate the forging of the pre-pressed part 50 using the forming groove 21, a forging cavity 42 is preferably provided in the forging die cavity 40 corresponding to the forming groove 21. A semi-circular cavity 45 is also provided corresponding to the semi-circular groove 22, so that the semi-circular groove 22 and the semi-circular cavity 45 cooperate to form the pipe connection end 61 of the connector 60. Similarly, a square cavity 44 is also provided corresponding to the square groove 23, so that the square groove 23 and the square cavity 44 cooperate to form the cavity connection end 62 of the connector 60.
[0048] Secondly, the semi-circular groove 22 of the convex mold plate 12 and the semi-circular cavity 45 of the lower mold form an upper and lower mold closing structure. Through forging, the metal pre-pressed part 50 fills the semi-circular cavity to form a cylinder of the pipeline connection end 61. The square groove 23 and the square cavity 44 are similarly formed to form a cube of the cavity connection end 62.
[0049] An inclined protrusion 43 is provided on the inner wall at the opening of the forging cavity 42. One side of the protrusion forms the inner wall of the forging cavity 42, and the other side is inclined towards the periphery of the forging die 40.
[0050] Specifically, the inclined protrusion 43 is equivalent to the retaining lip of the flash groove 41. During forging, the overflowing metal flows along the inclined surface to the flash groove 41 on the periphery of the die cavity, preventing the overflow from accumulating and affecting the accuracy of the forging. The inclined protrusion 43 is located between the forging cavity 42 and the forging die cavity 40. One side of the inclined protrusion 43 corresponds to the forging cavity 42 and forms part of the inner wall of the forging cavity 42; the other side of the inclined protrusion 43 slopes towards the bottom of the forging die cavity 40, thereby guiding the overflow of the pre-pressed part 50 to extend to the peripheral area of the forging die cavity 40.
[0051] Secondly, since overflow of material with a certain width will appear around the pre-pressed part 50 on the forming surface during the forging process, in order to accommodate this overflow, it is preferable to set the inner sidewall at the opening of the forging cavity 42 to extend upward to a certain height to form a protrusion, and set the side of the protrusion facing the outer area of the forging die cavity 40 to be a slope, thereby forming a slope protrusion 43, so that after the overflow of the forging cavity 42, the overflow can extend to all sides and extend along the slope protrusion 43 to the outer area of the forging die cavity 40, so that the outer area of the forging die cavity 40 can accommodate the overflow.
[0052] The concave template 32 is provided with guide protrusions 33 at its four corners, and the convex template 12 is provided with guide notches 13 at its four corners. The guide protrusions 33 and guide notches 13 cooperate with each other to guide the forging process.
[0053] Specifically, in order to make the concave template 32 and the convex template 12 more accurately positioned during the forging process, guide protrusions 33 and guide notches 13 can be set respectively to guide the convex template 12 and assist in completing the forging action.
[0054] The top of the guide protrusion 33 is provided with a guide post 34, and the bottom of the guide notch 13 is provided with a guide hole 14. The guide post 34 and the guide hole 14 cooperate with each other to guide the concave template 32 and the convex template 12 to be aligned at the center.
[0055] Specifically, in order to further ensure that the concave template 32 and the convex template 12 can maintain center alignment during the mold closing and forging process, it is preferable to provide guide posts 34 and guide holes 14 respectively. The guide posts 34 are inserted into the guide holes 14 to form a limit, thereby guiding the upper mold assembly 10 and the lower mold assembly 30 to maintain center alignment during the mold closing process.
[0056] Secondly, the guide protrusions 33 at the four corners of the concave mold plate 32 are provided with guide posts 34 at their top, and the guide notches 13 at the four corners of the convex mold plate 12 are provided with guide holes 14 at their bottom. When the mold is closed, the guide posts 34 are inserted into the guide holes 14 to achieve center alignment and precise guidance of the upper and lower molds.
[0057] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention.
Claims
1. A forming device for swaging a pipe joint, characterized by The equipment includes an upper die assembly (10) and a lower die assembly (30) arranged opposite to each other. The lower die assembly (30) is installed on the worktable of the forging equipment, and the upper die assembly (10) is installed on the slide beam of the forging equipment. The slide beam drives the upper die assembly (10) to move towards the lower die assembly (30) to perform forging operations on the metal pre-pressed part (50) placed in the lower die assembly (30). The lower die assembly (30) is provided with a lower die clamping plate (31) and a concave plate (32) fixedly connected to each other. A forging die is formed in the concave plate (32). The cavity (40) allows the metal pre-pressed part (50) to be placed in the forging die cavity (40) in advance; the upper die assembly (10) is provided with an upper die pad (11) and a punch plate (12) fixed to each other. The punch plate (12) is provided with a punch forming block (20) at one end facing the forging die cavity (40). The punch forming block (20) cooperates with the forging die cavity (40) and, under the drive of the forging equipment, performs forging and forming operation on the metal pre-pressed part (50) to forge and form the corresponding metal connector (60).
2. A forming device for swaging a pipe joint according to claim 1, wherein The central area of the punch forming block (20) is provided with a forming groove (21). One end of the forming groove (21) is provided with a semi-circular groove (22) for forming a pipe connection end (61) of the connector (60) in the shape of a cylinder. The other end of the forming groove (21) is provided with a square groove (23) for forming a cavity connection end (62) of the connector (60) in the shape of a cube. The bottom of the square groove (23) is provided with a square protrusion (24). During forging, the square protrusion (24) squeezes the metal pre-pressed part (50) to make the material flow to all sides, thereby forming a square channel (63) with an opening size larger than the bottom at the cavity connection end (62).
3. A forming device for swaging a pipe joint according to claim 2, wherein The square protrusion (24) is set with a bottom dimension larger than the top dimension, thereby forming an inclined angle along the demolding direction.
4. The forming apparatus for forging pipe joints according to claim 2, characterized in that, The top of the square protrusion (24) is provided with a semi-circular protrusion (25). During forging, the semi-circular protrusion (25) squeezes the metal pre-pressed part (50) to form a semi-circular channel (64) at the bottom of the square channel (63).
5. The forming device for swaging a pipe joint according to claim 1, wherein The central area of the forging die cavity (40) is set as a forging cavity (42), which is used to accommodate the pre-pressed part (50) and form the pre-pressed part (50) into a connector (60); wherein, one end of the forging cavity (42) is provided with a square cavity (44) for forming a cubic cavity connection end (62) of the connector (60); the other end of the forging cavity (42) is provided with a semi-circular cavity (45) for forming a cylindrical pipeline connection end (61) of the connector (60).
6. A forming device for swaging a pipe joint according to claim 5, wherein An inclined protrusion (43) is provided on the inner wall at the opening of the forging cavity (42), one side of which forms the inner wall of the forging cavity (42), and the other side is inclined to the periphery of the forging die cavity (40).
7. The forming device for swaging a pipe joint according to claim 1, wherein The concave template (32) is provided with guide protrusions (33) at the four corners, and the convex template (12) is provided with guide notches (13) at the four corners. The guide protrusions (33) and guide notches (13) cooperate with each other to guide the forging process.
8. A forming device for swaging a pipe joint according to claim 7, characterized in that The top of the guide protrusion (33) is provided with a guide column (34), the bottom of the guide gap (13) is provided with a guide hole (14), and the guide column (34) and the guide hole (14) are matched with each other to guide the center alignment of the concave die plate (32) and the convex die plate (12).