Engineering truck bucket accessory forging process

Abstract

The invention relates to the technical field of part forging, in particular to an engineering van bucket accessory forging process which comprises the following steps: cutting a steel raw material into round steel sections according to the size, heating to a forging temperature, ensuring the plasticity of the material, horizontally putting the heated round steel into a pre-forging cavity of a forging and forming machine tool, carrying out primary forging, turning over by 90 degrees, and forging again, and a wedge-shaped blank with one thick end and one thin end is formed, the thin end of the pre-forged blank is vertically placed into a finish forging cavity of a forming machine tool, and a wedge-shaped punch is used for carrying out split extrusion forging forming. According to the forging device, through the arrangement of the shaping device and the sliding connection of the embedded seat and the forging head seat, after the blank is filled with the embedded seat, the forging head seat continues to move downwards to cut off excess materials at the top end of the blank, the mounting hole of the blank is punched through the punching assembly while the forging head seat moves downwards, and when the mounting hole is punched, one end of the embedded seat is filled in the blank; therefore, blank deformation is avoided, and mounting hole forming is facilitated.

Description

Technical Field

[0001] This invention relates to the field of parts forging technology, specifically a forging process for engineering vehicle bucket parts. Background Technology

[0002] Bucket teeth are one of the components of engineering vehicle buckets. Forged bucket teeth are made by applying pressure to special metal billets using forging machinery, extruding and forming them at high temperatures, refining the grains in the forging, and causing plastic deformation to obtain certain mechanical properties. After forging, the metal's microstructure is improved, which can ensure that forged bucket teeth have good mechanical properties, are more wear-resistant, and have a longer service life. In the existing bucket tooth forging process, round steel is heated to a high temperature and then forged into bucket teeth by a forging forming machine. Subsequently, the billet is subjected to edge removal and mounting hole punching. Edge removal and mounting hole punching are performed on different forming machines, which increases the turnover steps of the parts and thus affects the forging efficiency of bucket teeth. Summary of the Invention

[0003] The purpose of this invention is to provide a forging process for engineering vehicle bucket parts to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A forging process for a component of an engineering vehicle bucket, the specific steps of which are as follows: Step 1: Cut the steel raw material into round steel segments according to the dimensions, and heat them to the forging temperature (1100±50℃) to ensure the plasticity of the material; Step 2: Place the heated round steel horizontally into the pre-forging cavity of the forging forming machine, perform the first forging, then rotate it 90 degrees and forge it again to form a wedge-shaped billet that is thick at one end and thin at the other. Step 3: Place the thinner end of the pre-forged billet vertically into the final forging cavity of the forming machine tool, and use a wedge punch to perform splitting and forging. After 4-5 forgings, it will be formed. Step 4: Place the formed blank into the shaping device to remove flash and punch the mounting holes; Step 5: Perform heat treatment on the stamped parts, including normalizing, quenching and low-temperature tempering, to improve hardness and wear resistance.

[0005] Furthermore, the pre-forging cavity in step two is designed to be flat, with the aim of making the billet close to the final shape of the bucket teeth and reducing the subsequent machining allowance.

[0006] Furthermore, the shaping device includes: A base plate is provided with a mold assembly mounted on top. The mold assembly includes two bases with grooves mounted on the bases. Two unit molds are mounted on the two grooves. One of the unit molds is fixedly mounted to the groove, while the other unit mold is slidably mounted between the two grooves. A push rod is mounted on one end of the base plate. The moving end of the push rod is fixedly mounted to the other unit mold. Through holes are provided on both sides of the unit mold. The forging machine body is installed at the other end of the base plate. A hydraulic rod is installed at the top of the forging machine body, and a forging head seat is installed at the bottom of the hydraulic rod. An embedded seat is slidably installed on the forging head seat, and a round hole is opened on the embedded seat. Unloading assembly one is installed on the forging machine body, and the unloading assembly one is used to clear the inside of the circular hole; A punching assembly is mounted on a base plate, the base plate being used to punch mounting holes; The second unloading assembly is installed on the base plate and located between the two bases. The second unloading assembly is used to loosen and unload the parts.

[0007] Furthermore, a frame is fixedly installed on one side of the forging head seat, and extrusion blocks are fixedly connected to both ends of the frame.

[0008] Furthermore, the punching assembly includes a mounting base mounted on a base plate. Fixed arms are fixedly mounted on both sides of the top of the mounting base. A punching rod is slidably sleeved on the top of each fixed arm. A wedge is mounted on one end of the punching rod. A return spring is installed between the wedge and the fixed arm. A limit frame is fixedly connected to the top of the fixed arm. The bottom end of the wedge is slidably connected to the limit frame. The punching rod is aligned with the position of the through hole.

[0009] Furthermore, the unloading assembly includes a fixed frame, which is fixedly installed on the forging machine body. Rollers are rotatably connected to the fixed frame, and a drive motor is fixedly installed at the bottom of the fixed frame. The output end of the drive motor is connected to one of the rollers. An arc-shaped frame is connected between the rollers, and the arc-shaped frame is used to insert into the round hole.

[0010] Furthermore, a slide rail is slidably connected to the groove rail, two slide rails are fixedly installed between the slide rail and another unit mold, and a slot is provided at the bottom of one unit mold, a push rod is slidably connected in the slot, and the unloading assembly is used to drive the push rod to move up and down.

[0011] Furthermore, the unloading assembly two includes a movable frame, which is fixedly installed at the bottom of the slot. An impact block is slidably connected to the movable frame. A sliding groove is provided on one side of the movable frame. A guide wheel is installed at the top of the movable frame. A protrusion is fixedly installed on one side of the impact block. A pull cable is fixedly connected to the top of the protrusion. A movable frame is slidably connected between the two slot rails. One end of the pull cable passes around the guide wheel and is fixedly installed with the movable frame. A limiting module is provided on one side of the movable frame.

[0012] Furthermore, the limiting module includes a push rod, a connecting rod is fixedly connected between the two slides, the top end of the push rod is fixedly installed with the connecting rod, a slide rail is installed on the base plate, the bottom end of the push rod is slidably connected to the slide rail, a broken rod is slidably connected on the slide rail, one end of the broken rod is rotatably connected to a connecting rod, one end of the connecting rod is rotatably connected to a stop block, and the stop block is slidably connected to the movable frame.

[0013] Furthermore, magnetic blocks are installed at the bottom of both the movable frame and the push rod, a positioning block is installed at one end of the groove rail, the positioning block is used to limit the stacking of the movable frame, and a shielding net is fixedly installed between the groove rails.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. By setting up the shaping device, the forming blank is placed between the cavities of the two unit molds. Then, the hydraulic rod drives the forging head seat and the insert seat to move down, so that the insert seat is embedded in the blank. Through the sliding connection between the insert seat and the forging head seat, after the insert seat fills the blank, the forging head seat continues to move down to remove the excess material at the top of the blank. At the same time as the forging head seat moves down, the punching assembly punches the mounting hole of the blank. The excess material formed by punching the mounting hole enters the round hole. Then, the forging head seat drives the insert seat to move up and reset. The unloading assembly pushes out and removes the excess material in the round hole. When punching the mounting hole, one end of the insert seat is filled in the blank, thereby avoiding the deformation of the blank, facilitating the forming of the mounting hole, facilitating the removal of excess material from the blank and punching the mounting hole, and improving processing efficiency. 2. With the setting of the unloading component two, after the mounting hole is punched and formed, the push rod drives another unit mold to move sideways, so that the two unit molds open. The broken rod drives the stop block to move down through the connecting rod. The stop block releases its contact with the push rod. When the moving frame moves outward, the impact block is pulled up through the cable, so that the push rod impacts the blank upward, so that the blank is disengaged from one of the unit molds. The blank falls onto the shielding net, which makes it convenient for workers to transfer and transport the parts with tools. After the two unit molds are opened, the parts are automatically peeled off from one unit mold without the need for manual knocking to remove them, which is convenient to use. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the location of the unloading component in this invention; Figure 3 This is a schematic diagram of the unloading assembly in this invention; Figure 4 This is a schematic diagram of the forging head seat structure in this invention; Figure 5 This is a schematic diagram of the punching assembly structure in this invention; Figure 6 This is a schematic diagram of the unit mold structure in this invention; Figure 7 This is a schematic diagram of the unloading assembly 2 and the carriage structure in this invention; Figure 8 This is a schematic diagram of the unloading component two in this invention; Figure 9 This is a schematic diagram of the movable frame structure in this invention.

[0016] In the diagram: 100, Forging machine body; 110, Hydraulic rod; 120, Forging head seat; 121, Embedded seat; 122, Round hole; 123, Frame; 124, Extrusion block; 200, Punching assembly; 210, Mounting seat; 220, Fixed arm; 230, Limiting frame; 240, Punching rod; 241, Inclined block; 250, Return spring; 300, Die assembly; 310, Unit die; 311, Through hole; 312, Slot; 320, Base; 330, Track rail; 331, Positioning block; 340, Shielding net; 350 360. Top rod; 361. Slide carriage; 370. Interval rod; 380. Slide rail; 400. Push rod; 410. Unloading assembly one; 420. Fixed frame; 430. Drive motor; 440. Roller; 500. Arc frame; 600. Base plate; 611. Unloading assembly two; 612. Movable frame; 613. Slide groove; 614. Guide wheel; 625. Impact block; 626. Protrusion; 630. Cable; 640. Moving frame; 650. Limiting module; 651. Push rod; 652. Broken rod; 653. Connecting rod; 654. Abutment block. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Please see Figures 1-6 In this embodiment of the invention, a forging process for engineering vehicle bucket parts is described, and the specific steps of the forging process are as follows: Step 1: Cut the steel raw material into round steel segments according to the dimensions, and heat them to the forging temperature (1100±50℃) to ensure the plasticity of the material; Step 2: Place the heated round steel horizontally into the pre-forging cavity of the forging forming machine, perform the first forging, then rotate it 90 degrees and forge it again to form a wedge-shaped billet that is thick at one end and thin at the other. Step 3: Place the thinner end of the pre-forged billet vertically into the final forging cavity of the forming machine tool, and use a wedge punch to perform splitting and forging. After 4-5 forgings, it will be formed. Step 4: Place the formed blank into the shaping device to remove flash and punch the mounting holes; Step 5: Perform heat treatment on the stamped parts, including normalizing, quenching and low-temperature tempering, to improve hardness and wear resistance; The pre-forging cavity in step two is designed to be flat, in order to make the billet close to the final shape of the bucket teeth and reduce the subsequent machining allowance.

[0019] The shaping device includes a forging machine body 100, a punching assembly 200, a first unloading assembly 400, a base plate 500, and a second unloading assembly 600. A mold assembly 300 is mounted above the base plate 500. The mold assembly 300 includes two bases 320, with a channel rail 330 mounted on each base 320. Two unit molds 310 are mounted on the two channel rails 330. One unit mold 310 is fixedly mounted to the channel rail 330, while the other unit mold 310 is slidably mounted to the channel rail 330. A push rod 380 is mounted at one end of the base plate 500, and the moving end of the push rod 380 is fixedly mounted to the other unit mold 310. Both sides of the unit mold 310 have through-holes. Hole 311, forging machine body 100 is installed at the other end of base plate 500, hydraulic rod 110 is installed at the top of forging machine body 100, forging head seat 120 is installed at the bottom of hydraulic rod 110, embedded seat 121 is slidably installed on forging head seat 120, embedded seat 121 has a round hole 122, unloading assembly 400 is installed on forging machine body 100, unloading assembly 400 is used to clear the round hole 122, punching assembly 200 is installed on base plate 500, base plate 500 is used to punch the mounting hole, unloading assembly 600 is installed on base plate 500 and located between two bases 320, unloading assembly 600 is used to loosen and remove parts.

[0020] Specifically, the forming blank is placed between the cavities of the two unit molds 310. Then, the hydraulic rod 110 drives the forging head seat 120 and the insert seat 121 to move downwards, causing the insert seat 121 to embed into the blank. Through the sliding connection between the insert seat 121 and the forging head seat 120, after the insert seat 121 fills the blank, the forging head seat 120 continues to move downwards to remove excess material from the top of the blank. Simultaneously, the forging head seat 120 moves downwards while the punching assembly 200 punches the mounting holes in the blank. The excess material formed by punching the mounting holes enters the round hole 122. Subsequently... The forging head seat 120 drives the insert seat 121 to move upward and reset. The unloading assembly 400 pushes out and removes the excess material in the round hole 122. The other unit mold 310 moves to the side, opening the gap between the two unit molds 310. When the other unit mold 310 moves to the side, the unloading assembly 600 pushes out the blank, allowing the blank to detach from the cavity in one unit mold 310, thus making it easier for the worker to unload the blank. When the mounting hole is punched, one end of the insert seat 121 is filled into the blank, thus avoiding the deformation of the blank and facilitating the forming of the mounting hole.

[0021] Example 1 like Figures 3-7 As shown, in this embodiment, a bracket 123 is fixedly installed on one side of the forging head seat 120, and extrusion blocks 124 are fixedly connected to both ends of the bracket 123. The punching assembly 200 includes a mounting base 210, which is mounted on the base plate 500. Fixed arms 220 are fixedly installed on both sides of the top end of the mounting base 210. A punching rod 240 is slidably sleeved on the top end of the fixed arm 220. A wedge block 241 is installed on one end of the punching rod 240. A return spring 250 is installed between the wedge block 241 and the fixed arm 220. A limit frame 230 is fixedly connected to the top end of the fixed arm 220. The bottom end of the wedge block 241 is slidably connected to the limit frame 230. The position of the punching rod 240 is aligned with the through hole 311. The unloading assembly 400 package The assembly includes a fixed frame 410, which is fixedly installed on the forging machine body 100. Rollers 430 are rotatably connected to the fixed frame 410. A drive motor 420 is fixedly installed at the bottom of the fixed frame 410. The output end of the drive motor 420 is connected to one of the rollers 430. An arc-shaped frame 440 is connected between the rollers 430. The arc-shaped frame 440 is used to insert into the round hole 122. A slide 360 ​​is slidably connected on the groove rail 330. Two slides 360 are fixedly installed between the slide and another unit mold 310. A slot 312 is opened at the bottom of the unit mold 310. A push rod 350 is slidably connected in the slot 312. The unloading assembly 600 is used to drive the push rod 350 to move up and down.

[0022] In this embodiment, when the forging head seat 120 moves downward, the extrusion block 124 extrudes the inclined block 241, causing the inclined block 241 to drive the stamping rod 240 closer to the blank, thereby stamping a mounting hole on the blank. The excess material formed in the mounting hole is pushed into the round hole 122 by the stamping rod 240. When the forging head seat 120 moves upward, the stamping rod 240 moves back under the elastic force of the return spring 250. After the inclined block 241 abuts against the limit frame 230, the stamping rod 240 stops, causing one end of the stamping rod 240 to retract into the through hole 311 and separate from the blank. This achieves stamping of the mounting hole of the blank while the insert seat 121 is filling the blank, reducing the deformation of the blank.

[0023] Example 2 like Figures 6-9 As shown, in this embodiment, the unloading assembly 600 includes a movable frame 610, which is fixedly installed at the bottom of the slot 312. An impact block 620 is slidably connected to the movable frame 610. A sliding groove 611 is provided on one side of the movable frame 610. A guide wheel 612 is installed at the top of the movable frame 610. A protrusion 621 is fixedly installed on one side of the impact block 620. A pull cable 630 is fixedly connected to the top of the protrusion 621. A movable frame 640 is slidably connected between the two slot rails 330. One end of the pull cable 630 passes around the guide wheel 612 and is fixedly installed with the movable frame 640. A limiting module 650 is provided on one side of the movable frame 610. The limiting module 650 includes a push rod 651 and two sliding... A spacer 361 is fixedly connected between the frames 360. The top end of the push rod 651 is fixedly installed with the spacer 361. A slide rail 370 is installed on the base plate 500. The bottom end of the push rod 651 is slidably connected to the slide rail 370. A broken rod 652 is slidably connected to the slide rail 370. One end of the broken rod 652 is rotatably connected to a connecting rod 653. One end of the connecting rod 653 is rotatably connected to a stop block 654. The stop block 654 is slidably connected to the movable frame 610. Magnetic blocks are installed at the bottom ends of the movable frame 640 and the push rod 651. A positioning block 331 is installed at one end of the channel rail 330. The positioning block 331 is used to limit the stacking of the movable frame 640. A shielding net 340 is fixedly installed between the channel rails 330.

[0024] In specific implementation, after the mounting hole is stamped, the push rod 380 drives another unit mold 310 to move laterally, opening the gap between the two unit molds 310. When the other unit mold 310 moves laterally, it drives the two slides 360 and the spacer 361 to move outward. When the spacer 361 moves outward, it drives the push rod 651 to move outward. The push rod 651 attracts the broken rod 652 through the magnetic block, causing the broken rod 652 to slide outward on the slide rail 370. The broken rod 652 drives the abutment 654 to move downward through the connecting rod 653. The abutment 654 releases its contact with the top rod 350, and the top rod 350 moves downward under the action of gravity. Subsequently, after the slide 360 ​​contacts the moving frame 640, the moving frame 640 is pushed outward. When the moving frame 640 moves outward, it pulls the impact block 620 upward through the cable 630. When the impact block 620 moves upward, it contacts the top rod 350, thus... The push rod 350 moves upward, impacting the blank and disengaging it from one unit mold 310. The blank falls onto the shielding net 340, facilitating subsequent transfer and handling by workers using tools. When the other unit mold 310 resets, the intermediate rod 361 pulls the moving frame 640 inward until it is stopped by the through hole 311. The intermediate rod 361 continues to move inward, disengaging from the moving frame 640. The impact block 620 moves downward under gravity, disengaging from the push rod 350. The inward movement of the intermediate rod 361 causes the abutment block 654 to move upward, supporting and limiting the push rod 350. The leg push rod 350 fills the slot 312, preventing the bottom of the blank from embedding into the slot 312 when the forging head seat 120 is pressed downward.

[0025] 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.

[0026] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A forging process for engineering vehicle bucket parts, characterized in that, The specific steps of the forging process for this component are as follows: Step 1: Cut the steel raw material into round steel segments according to the dimensions, and heat them to the forging temperature (1100±50℃) to ensure the plasticity of the material; Step 2: Place the heated round steel horizontally into the pre-forging cavity of the forging forming machine, perform the first forging, then rotate it 90 degrees and forge it again to form a wedge-shaped billet that is thick at one end and thin at the other. Step 3: Place the thinner end of the pre-forged billet vertically into the final forging cavity of the forming machine tool, and use a wedge punch to perform splitting and forging. After 4-5 forgings, it will be formed. Step 4: Place the formed blank into the shaping device to remove flash and punch the mounting holes; Step 5: Perform heat treatment on the stamped parts, including normalizing, quenching and low-temperature tempering, to improve hardness and wear resistance.

2. The forging process for engineering vehicle bucket parts according to claim 1, characterized in that, The pre-forging cavity in step two is designed to be flat, with the aim of making the billet close to the final shape of the bucket teeth and reducing the subsequent machining allowance.

3. The forging process for engineering vehicle bucket parts according to claim 1, characterized in that, The shaping device includes: A base plate (500) is provided with a mold assembly (300) mounted on top. The mold assembly (300) includes two bases (320). A groove rail (330) is mounted on the base (320). Two unit molds (310) are mounted on the two groove rails (330). One of the two unit molds (310) is fixedly installed with the groove rail (330), and the other unit mold (310) is slidably installed with the groove rail (330). A push rod (380) is installed at one end of the base plate (500). The moving end of the push rod (380) is fixedly installed with the other unit mold (310). Through holes (311) are provided on both sides of the unit mold (310). The forging machine body (100) is installed at the other end of the base plate (500). A hydraulic rod (110) is installed at the top of the forging machine body (100), and a forging head seat (120) is installed at the bottom of the hydraulic rod (110). An embedded seat (121) is slidably installed on the forging head seat (120), and a round hole (122) is opened on the embedded seat (121). Unloading assembly 1 (400) is installed on the forging machine body (100) and is used to clear the hole (122); A punching assembly (200) is mounted on a base plate (500) for punching mounting holes; Unloading assembly 2 (600) is mounted on base plate (500) and located between two bases (320), said unloading assembly 2 (600) is used to loosen and unload parts.

4. The forging process for engineering vehicle bucket parts according to claim 3, characterized in that, A frame (123) is fixedly installed on one side of the forging head seat (120), and a pressing block (124) is fixedly connected to both ends of the frame (123).

5. The forging process for engineering vehicle bucket parts according to claim 4, characterized in that, The punching assembly (200) includes a mounting base (210) mounted on a base plate (500). Fixing arms (220) are fixedly mounted on both sides of the top end of the mounting base (210). A punching rod (240) is slidably sleeved on the top end of the fixing arm (220). A wedge (241) is mounted on one end of the punching rod (240). A return spring (250) is installed between the wedge (241) and the fixing arm (220). A limit frame (230) is fixedly connected to the top end of the fixing arm (220). The bottom end of the wedge (241) is slidably connected to the limit frame (230). The punching rod (240) is aligned with the through hole (311).

6. The forging process for engineering vehicle bucket parts according to claim 3, characterized in that, The unloading assembly (400) includes a fixed frame (410), which is fixedly installed on the forging machine body (100). Rollers (430) are rotatably connected to the fixed frame (410). A drive motor (420) is fixedly installed at the bottom of the fixed frame (410). The output end of the drive motor (420) is connected to one of the rollers (430). A curved frame (440) is connected between the rollers (430). The curved frame (440) is used to be inserted into the round hole (122).

7. A forging process for engineering vehicle bucket parts according to any one of claims 3 to 6, characterized in that, A slide frame (360) is slidably connected on the groove rail (330). Two slide frames (360) are fixedly installed between the slide frame (360) and another unit mold (310). A slot (312) is opened at the bottom of one unit mold (310). A push rod (350) is slidably connected in the slot (312). The unloading assembly (600) is used to drive the push rod (350) to move up and down.

8. The forging process for engineering vehicle bucket parts according to claim 7, characterized in that, The unloading assembly 2 (600) includes a movable frame (610), which is fixedly installed at the bottom end of the slot (312). An impact block (620) is slidably connected to the movable frame (610). A sliding groove (611) is provided on one side of the movable frame (610). A guide wheel (612) is installed at the top of the movable frame (610). A protrusion (621) is fixedly installed on one side of the impact block (620). A cable (630) is fixedly connected to the top of the protrusion (621). A movable frame (640) is slidably connected between the two slot rails (330). One end of the cable (630) passes around the guide wheel (612) and is fixedly installed with the movable frame (640). A limiting module (650) is provided on one side of the movable frame (610).

9. The forging process for engineering vehicle bucket parts according to claim 8, characterized in that, The limiting module (650) includes a push rod (651), a spacer (361) is fixedly connected between the two slides (360), the top end of the push rod (651) is fixedly installed with the spacer (361), a slide rail (370) is installed on the base plate (500), the bottom end of the push rod (651) is slidably connected with the slide rail (370), a broken rod (652) is slidably connected on the slide rail (370), one end of the broken rod (652) is rotatably connected with a connecting rod (653), one end of the connecting rod (653) is rotatably connected with a stop block (654), and the stop block (654) is slidably connected with the movable frame (610).

10. The forging process for engineering vehicle bucket parts according to claim 9, characterized in that, The bottom ends of the movable frame (640) and the push rod (651) are both equipped with magnetic blocks. One end of the groove rail (330) is equipped with a positioning block (331). The positioning block (331) is used to limit the stacking of the movable frame (640). A shielding net (340) is fixedly installed between the groove rails (330).

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