A high-frequency thin-wall waveguide precision drawing equipment

Abstract

The present invention discloses a high-frequency thin-wall waveguide precision drawing device, which relates to the field of communication technology; it comprises a base, the top of which is fixedly connected with a lifting platform and a servo motor arranged on the left and right, the top of which is fixed with an outer mold, the outer mold is provided with a mold core with a tube blank on the outside, the left output end of the servo motor is fixedly connected with a screw, and is movably connected with a movable plate through the screw, and a drawing chuck is installed on the movable plate. The present invention enables the drawing chuck to perform horizontal linear motion through a screw and a slide rail, thereby ensuring the motion accuracy of the device during the drawing process, and at the same time, the outer mold covers the tube blank and locks it, so that the outer mold squeezes the outer wall of the tube blank, and when the mold core moves, its spherical structure squeezes the inner wall of the tube blank, thereby ensuring the accuracy of the outer diameter and the inner diameter, and when drawing, the outer mold, the tube blank, and the mold core are sequentially connected to fully cover the tube blank, so that the pressure on the inside and outside of the tube blank is uniform, thereby avoiding the phenomenon of uneven tube wall.

Description

Technical Field

[0001] The invention relates to the field of communication technology, in particular to a high-frequency thin-wall waveguide precision drawing device. Background Art

[0002] At present, the thin-walled waveguide tubes in the industry are all processed using conventional tube profile drawing equipment. Although conventional profile drawing equipment can meet the drawing requirements of waveguide tubes with lower transmission frequencies within 4-11GHz. However, due to the characteristics of microwave transmission, the higher the transmission frequency, the smaller the inner diameter of the waveguide tube and the stricter the tolerance requirements, and the tolerance is generally within 0.02mm. When producing waveguide tubes with higher transmission frequencies within 13-80GHz, the tube wall thickness is 1-2mm and the inner diameter is 2.5-16mm. The traditional inner and outer mold core drawing equipment is difficult to debug, the tube wall is uneven, and the roundness and concentricity are poor, so that most of the produced waveguide tubes are of low precision and large errors, resulting in low yield. Summary of the invention

[0003] The technical problem solved by the present invention is to overcome the defects of the prior art such as low production precision and provide a high-frequency thin-wall waveguide precision drawing device. The high-frequency thin-wall waveguide precision drawing device has the characteristics of high production precision and the like.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a high-frequency thin-wall waveguide precision drawing device, comprising a base, the top of the base is fixedly connected with a lifting platform and a servo motor arranged on the left and right, the top of the lifting platform is fixed with an outer mold, the outer mold is equipped with a mold core with a tube blank on the outside, the left output end of the servo motor is fixedly connected with a screw rod, and is movably connected with a movable plate through the screw rod, and a drawing chuck is installed on the movable plate;

[0005] The outer mold is in a rectangular shape, and a through hole is provided on the outer mold. An extrusion seam extending to the front side of the outer mold is provided on the front side of the through hole. The tube embryo is inserted in the through hole, and both ends extend to the outside of the outer mold. The mold core is inserted in the tube embryo, and both ends extend to the outside of the tube embryo. The outer mold is provided with a plurality of evenly distributed mounting holes, and is fixed to the top of the lifting platform through the mounting holes and bolts. An insertion hole is provided on the outer mold above the extrusion seam, and a butterfly bolt is inserted in the insertion hole. A first threaded hole threadedly connected to the butterfly bolt is provided on the outer mold below the extrusion seam.

[0006] The top of the base is located at both the front and rear sides of the lifting platform and is fixedly connected with first vertical plates. The right side of the lifting platform is provided with a first fixed plate fixedly connected with the two first vertical plates. The first fixed plate is provided with a slot on the left side and an opening connected with the slot on the right side. A positioning block is fixedly connected in the slot by bolts. A groove is provided on the left side of the positioning block and a through hole is provided on the right side of the groove. The right end of the tube blank is inserted in the groove, and the right end of the mold core passes through the groove and the through hole and extends into the opening.

[0007] The top of the base is fixedly connected to a support plate near the right side, the servo motor is fixedly connected to the right side of the support plate, and an opening is provided on the support plate, and the top of the base is located between the lifting platform and the support plate and is fixedly connected to two left and right fixed seats, the screw is located between the two fixed seats, and both ends are movably connected to the fixed seats through bearings, the right end of the screw passes through adjacent bearings and openings, and is fixedly connected to the servo motor, the screw is sleeved with a movable block with a second threaded hole, and is threadedly connected to the movable block, the movable plate is fixedly connected to the top of the movable block, the top of the movable plate is fixedly connected to a second vertical plate set front and back, the left side of the second vertical plate is fixedly connected to the second fixed plate, a pneumatic clamp is provided on the right side of the second fixed plate between the two second vertical plates, the left side of the pneumatic clamp passes through the second fixed plate, the drawing chuck is fixedly connected between the two jaws of the pneumatic clamp, the left side of the drawing chuck is inserted in the opening, and clamps the right end of the mold core.

[0008] Preferably, the left end of the mold core is conical, and the connection between the left end and the middle part is a mirror-polished spherical structure. An annular groove is opened on the circumference of the mold core near the right end, and the clamping part of the drawing chuck on the mold core is located in the annular groove.

[0009] Preferably, the front and rear sides of the screw rod are both provided with slide rails fixedly connected to the top of the base, and the tops of the two slide rails are both provided with two sliding blocks with two left and right sliding blocks, and the sliding blocks are fixedly connected to the movable plate.

[0010] Preferably, the pulling chuck consists of two clamping blocks arranged upper and lower, and the two clamping blocks are respectively fixedly connected to the inner sides of the two clamping jaws on the pneumatic clamping jaws, and the two clamping blocks are both U-shaped, and the openings of the two clamping blocks are arranged opposite to each other. The side of the two clamping blocks close to each other is located on the left side and is clamped with the annular groove, the bottom of the clamping block located above is provided with a protrusion near the right side, and the top of the clamping block located below is provided with a slot matching the protrusion near the right side.

[0011] Preferably, two third fixing plates are fixedly connected to the left side of the second fixing plate, a fixing rod is fixedly connected between the two third fixing plates, and sliding holes are provided on the two clamping jaws of the pneumatic clamp and the two clamping blocks of the pulling chuck, and the fixing rod passes through the sliding hole.

[0012] Preferably, two left and right photoelectric sensors are embedded on the top of the base, and the two photoelectric sensors are located below the screw rod and close to both ends of the screw rod.

[0013] A high-frequency thin-wall waveguide precision drawing device comprises the following steps:

[0014] S1: First, fix the outer mold on the top of the lifting platform with bolts, and adjust the height of the lifting platform so that the through hole on the outer mold is aligned with the through hole on the positioning block;

[0015] S2: Then, the servo motor is started to make the movable plate drive the drawing chuck to move to the initial position above the left photoelectric sensor, triggering the photoelectric sensor signal to make the pneumatic clamping jaws move to open the drawing chuck;

[0016] S3: Then, the tube embryo is inserted into the through hole of the outer mold from the left side, and the mold core is inserted into the tube embryo from the left side, the right end of the mold core is inserted into the opening, and the butterfly bolt is screwed to clamp the tube embryo with the outer mold;

[0017] S4: Then, the pneumatic clamp is started to close the drawing chuck, clamp the right end of the mold core, and the servo motor is started to move the movable plate to the right through the screw and the movable block, and drive the drawing chuck to pull the mold core to the right to draw the tube blank;

[0018] S5: Then, when the movable plate moves to above the right photoelectric sensor, the right photoelectric sensor is triggered. At this time, the servo motor drives the screw to reverse, so that the movable plate moves back to its original position, triggering the left photoelectric sensor, so that the pneumatic clamping claw moves to open the drawing chuck;

[0019] S6: Finally, the mold core and the tube blank after precision drawing are taken out in turn to obtain a thin-walled waveguide tube.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention enables the drawing chuck to perform horizontal linear motion through a screw rod and a slide rail, thereby ensuring the motion accuracy of the device during the drawing process. At the same time, the outer mold covers the tube embryo and locks it, so that the outer mold squeezes the outer wall of the tube embryo. When the mold core moves, its spherical structure squeezes the inner wall of the tube embryo, thereby ensuring the accuracy of the outer diameter and the inner diameter. During drawing, the outer mold, the tube embryo, and the mold core are sequentially sleeved to fully cover the tube embryo, so that the pressure inside and outside the tube embryo is uniform, thereby avoiding the phenomenon of uneven tube wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a stereogram of the present invention;

[0023] Figure 2 It is a right side stereogram of the present invention;

[0024] Figure 3It is a schematic diagram of the structure of the present invention;

[0025] Figure 4 It is a three-dimensional diagram of the outer mold and the drawing chuck of the present invention;

[0026] Figure 5 It is a cross-sectional view of the outer mold of the present invention;

[0027] Figure 6 for Figure 3 Enlarged view of point A in the middle.

[0028] Numbers in the figure: 1. base; 2. outer mold; 3. slider; 4. screw; 5. fixed seat; 6. support plate; 7. servo motor; 8. slide rail; 9. movable plate; 10. second vertical plate; 11. first fixed plate; 12. first vertical plate; 13. lifting platform; 14. pneumatic clamp; 15. mold core; 16. tube blank; 17. butterfly bolt; 18. second fixed plate; 19. positioning block; 20. pulling chuck; 21. third fixed plate; 22. movable block; 23. photoelectric sensor; 24. fixing rod. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] See also Figure 1-6 The present invention provides a technical solution: a high-frequency thin-wall waveguide precision drawing device, comprising a base 1, a lifting platform 13 and a servo motor 7 arranged on the left and right are fixedly connected to the top of the base 1, the lifting platform 13 is a scissor-type lifting platform with a self-contained driving motor, an outer mold 2 is fixed on the top of the lifting platform 13, a mold core 15 with a tube blank 16 is installed in the outer mold 2, a screw 4 is fixedly connected to the left output end of the servo motor 7, and a movable plate 9 is movably connected to the screw 4, and a drawing chuck 20 is installed on the movable plate 9;

[0031] The outer mold 2 is in a rectangular shape, and a through hole is provided on the outer mold 2. An extrusion seam extending to the front side of the outer mold 2 is provided on the front side of the through hole. The tube embryo 16 is inserted in the through hole, and both ends extend to the outside of the outer mold 2. The mold core 15 is inserted in the tube embryo 16, and both ends extend to the outside of the tube embryo 16. The outer mold 2 is provided with a plurality of evenly distributed mounting holes, and is fixed to the top of the lifting platform 13 through the mounting holes and bolts. A plug hole is provided on the outer mold 2 above the extrusion seam, and a butterfly bolt 17 is inserted in the plug hole. A first threaded hole threadedly connected to the butterfly bolt 17 is provided on the outer mold 2 below the extrusion seam.

[0032] The left end of the mold core 15 is conical, and the connection between the left end and the middle part of the cone is a mirror-polished spherical structure. An annular groove is provided near the right end of the mold core 15. The clamping part of the drawing chuck 20 on the mold core 15 is located in the annular groove. The spherical structure squeezes the inner wall of the tube embryo 16 when the mold core 15 moves to the right, and the outer surface of the spherical structure is mirror-polished, which reduces the friction between the mold core 15 and the tube embryo 16.

[0033] The top of the base 1 is located at both the front and rear sides of the lifting platform 13 and is fixedly connected with the first vertical plates 12. The right side of the lifting platform 13 is provided with a first fixed plate 11 fixedly connected with the two first vertical plates 12. The first fixed plate 11 is provided with a slot on the left side and an opening connected with the slot on the right side. A positioning block 19 is fixedly connected with the slot by bolts. The positioning block 19 is provided with a groove on the left side and a through hole on the right side of the groove. The right end of the tube blank 16 is inserted into the groove, and the right end of the mold core 15 passes through the groove and the through hole and extends into the opening.

[0034] A support plate 6 is fixedly connected to the top of the base 1 near the right side, and a servo motor 7 is fixedly connected to the right side of the support plate 6. An opening is provided on the support plate 6. The top of the base 1 is located between the lifting platform 13 and the support plate 6 and is fixedly connected to two fixed seats 5 arranged on the left and right. The screw 4 is located between the two fixed seats 5, and both ends are movably connected to the fixed seats 5 through bearings. The right end of the screw 4 passes through the adjacent bearings and openings and is fixedly connected to the servo motor 7. A movable block 22 with a second threaded hole is sleeved on the screw 4 and is connected to the servo motor 7. The movable block 22 is threadedly connected, the movable plate 9 is fixedly connected to the top of the movable block 22, the top of the movable plate 9 is fixedly connected to the second vertical plate 10 arranged in front and behind, the second vertical plate 10 is fixedly connected to the left side thereof, the second fixed plate 18 is fixedly connected, the right side of the second fixed plate 18 is provided with a pneumatic clamping jaw 14 located between the two second vertical plates 10, the left side of the pneumatic clamping jaw 14 penetrates the second fixed plate 18, the drawing chuck 20 is fixedly connected between the two clamping jaws of the pneumatic clamping jaw 14, the left side of the drawing chuck 20 is inserted into the opening, and clamps the right end of the mold core 15;

[0035] The front and rear sides of the screw rod 4 are both provided with slide rails 8 fixedly connected to the top of the base 1, and the tops of the two slide rails 8 are both slid with two sliders 3 arranged on the left and right, and the sliders 3 are fixedly connected to the movable plate 9 to support the movable plate 9 and prevent the movable plate 9 from deflecting to one side when moving;

[0036] The drawing chuck 20 is composed of two clamping blocks arranged up and down, and the two clamping blocks are respectively fixedly connected to the inner sides of the two clamping jaws on the pneumatic clamping jaw 14. The two clamping blocks are both U-shaped, and the openings of the two clamping blocks are arranged opposite to each other. The side of the two clamping blocks close to each other is located on the left side and is clamped with the annular groove. The bottom of the clamping block located at the top is provided with a protrusion near the right side, and the top of the clamping block located at the bottom is provided with a slot matching the protrusion near the right side, which can clamp the right end of the mold core 15. Two third fixing plates 21 are fixedly connected to the left side of the second fixing plate 18, and a fixing rod 24 is fixedly connected between the two third fixing plates 21. Sliding holes are provided on the two clamping jaws of the pneumatic clamping jaw 14 and the two clamping blocks of the drawing chuck 20, and the fixing rod 24 passes through the sliding holes to limit the movement of the two clamping blocks to prevent the clamping blocks from being offset by external influences.

[0037] Two left and right photoelectric sensors 23 are embedded on the top of the base 1. Both photoelectric sensors 23 are located below the screw 4 and close to the two ends of the screw 4 to detect whether the movable plate 9 drives the drawing chuck 20 to move into place.

[0038] A method for using a high-frequency thin-wall waveguide precision drawing device comprises the following steps:

[0039] S1: First, the outer mold 2 is fixed to the top of the lifting platform 13 by bolts, and the height of the lifting platform 13 is adjusted by the built-in driving motor so that the through hole on the outer mold 2 is aligned with the through hole on the positioning block 19;

[0040] S2: Then, the servo motor 7 is started, the servo motor 7 drives the screw 4 to rotate, and drives the drawing chuck 20 to move to the initial position above the left photoelectric sensor 23 through the movable block 22 and the movable plate 9, triggering the photoelectric sensor 23 signal, so that the pneumatic clamping jaw 14 drives the clamping block of the drawing chuck 20 to open;

[0041] S3: Then, insert the tube embryo 16 into the through hole of the outer mold 2 from the left side, and insert the mold core 15 into the tube embryo 16 from the left side, so that the right end of the mold core 15 is inserted into the opening, and the butterfly bolt 17 is screwed to make the upper and lower parts of the outer mold 2 close to each other at the extrusion seam, so as to clamp the tube embryo 16 and extrude the outer wall of the tube embryo 16 to ensure the accuracy of the outer diameter;

[0042] S4: Then, the pneumatic clamp 14 is started to bring the clamps closer together to close the drawing chuck 20, so that the clamp block is engaged with the annular groove at the right end of the mold core 15 to clamp the right end of the mold core 15, and the servo motor 7 is started. The servo motor 7 moves the movable plate 9 to the right through the screw 4 and the movable block 22, and drives the drawing chuck 20 to pull the mold core 15 to the right to draw the tube embryo 16. At this time, the spherical structure of the mold core 15 moves in the tube embryo 16 and squeezes the inner wall of the tube embryo 16 to ensure the accuracy of the inner wall of the tube embryo 16. At the same time, the outer mold 2 fully covers the tube embryo 16, and the screw 4 and the slide rail 8 make the drawing chuck 20 move horizontally and linearly, so that the mold core 15 moves linearly in the tube embryo 16, so that the force inside and outside the tube embryo 16 is uniform, so that the tube wall thickness of the tube embryo 16 is uniform during drawing;

[0043] S5: Then, when the movable plate 9 moves to above the right photoelectric sensor 23, the right photoelectric sensor 23 is triggered and generates a signal, so that the servo motor 7 drives the screw rod 4 to reverse, so that the movable plate 9 moves back to its original position, and the left photoelectric sensor 23 is triggered again, so that the pneumatic clamping jaw 14 moves to open the drawing chuck 20;

[0044] S6: Finally, the mold core 15 and the tube blank 16 after precision drawing are taken out in turn to obtain a thin-walled waveguide tube.

[0045] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-frequency thin-wall waveguide precision drawing device, comprising a base (1), characterized in that: The top of the base (1) is fixedly connected to a lifting platform (13) and a servo motor (7) arranged on the left and right, the top of the lifting platform (13) is fixed to an outer mold (2), the outer mold (2) is equipped with a mold core (15) with a tube blank (16) on the outside, the left output end of the servo motor (7) is fixedly connected to a screw rod (4), and is movably connected to a movable plate (9) through the screw rod (4), and a drawing chuck (20) is installed on the movable plate (9); The outer mold (2) is in the shape of a rectangular parallelepiped and is provided with a through hole. An extrusion seam extending to the front side of the outer mold (2) is provided on the front side of the through hole. The tube blank (16) is inserted into the through hole, and both ends extend to the outside of the outer mold (2). The mold core (15) is inserted into the tube blank (16), and both ends extend to the outside of the tube blank (16). The outer mold (2) is provided with a plurality of evenly distributed mounting holes and is fixed to the top of the lifting platform (13) through the mounting holes and bolts. An insertion hole is provided on the outer mold (2) above the extrusion seam, and a butterfly bolt (17) is inserted into the insertion hole. A first threaded hole threadedly connected to the butterfly bolt (17) is provided on the outer mold (2) below the extrusion seam. The top of the base (1) is located at both the front and rear sides of the lifting platform (13), and is fixedly connected to the first vertical plates (12). The right side of the lifting platform (13) is provided with a first fixed plate (11) fixedly connected to the two first vertical plates (12). The first fixed plate (11) is provided with a slot on the left side, and an opening connected to the slot on the right side. A positioning block (19) is fixedly connected to the slot by bolts. The positioning block (19) is provided with a groove on the left side, and a through hole on the right side of the groove. The right end of the tube blank (16) is inserted into the groove, and the right end of the mold core (15) passes through the groove and the through hole and extends into the opening. A support plate (6) is fixedly connected to the top of the base (1) near the right side, the servo motor (7) is fixedly connected to the right side of the support plate (6), an opening is provided on the support plate (6), the top of the base (1) is located between the lifting platform (13) and the support plate (6) and is fixedly connected to two fixed seats (5) arranged on the left and right, the screw rod (4) is located between the two fixed seats (5), and both ends are movably connected to the fixed seats (5) through bearings, the right end of the screw rod (4) passes through the adjacent bearings and the opening, and is fixedly connected to the servo motor (7), the screw rod (4) is sleeved with a movable block (22) with a second threaded hole, and is connected to the servo motor (7), and the screw rod (4) is sleeved with a movable block (22) with a second threaded hole. The movable block (22) is threadedly connected, the movable plate (9) is fixedly connected to the top of the movable block (22), the top of the movable plate (9) is fixedly connected to a second vertical plate (10) arranged in front and behind, the left side of the second vertical plate (10) is fixedly connected to a second fixed plate (18), the right side of the second fixed plate (18) is provided with a pneumatic clamp (14) located between the two second vertical plates (10), the left side of the pneumatic clamp (14) passes through the second fixed plate (18), the drawing chuck (20) is fixedly connected between the two clamping jaws of the pneumatic clamp (14), the left side of the drawing chuck (20) is inserted into the opening, and clamps the right end of the mold core (15).

2. A high-frequency thin-wall waveguide precision drawing device according to claim 1, characterized in that: The left end of the mold core (15) is conical, and the connection between the left end and the middle part of the cone is a mirror-polished spherical structure. An annular groove is provided on the circumference of the mold core (15) near the right end, and the clamping part of the drawing chuck (20) on the mold core (15) is located in the annular groove.

3. The high-frequency thin-wall waveguide precision drawing equipment according to claim 1, characterized in that: The screw rod (4) is provided with slide rails (8) fixedly connected to the top of the base (1) on both the front and rear sides, and the tops of the two slide rails (8) are provided with two sliding blocks (3) arranged on the left and right, and the sliding blocks (3) are fixedly connected to the movable plate (9).

4. The high-frequency thin-wall waveguide precision drawing equipment according to claim 2, characterized in that: The drawing chuck (20) is composed of two clamping blocks arranged up and down, the two clamping blocks are respectively fixedly connected to the inner sides of the two clamping jaws on the pneumatic clamping jaw (14), the two clamping blocks are both U-shaped, and the openings of the two clamping blocks are arranged opposite to each other. The two clamping blocks are close to each other and are clamped with the annular groove on the left side. The bottom of the clamping block located at the top is provided with a protrusion near the right side, and the top of the clamping block located at the bottom is provided with a slot matching the protrusion near the right side.

5. The high-frequency thin-wall waveguide precision drawing equipment according to claim 1, characterized in that: Two third fixing plates (21) are fixedly connected to the left side of the second fixing plate (18), a fixing rod (24) is fixedly connected between the two third fixing plates (21), and sliding holes are provided on the two clamping jaws of the pneumatic clamping jaw (14) and the two clamping blocks of the drawing clamp (20), and the fixing rod (24) passes through the sliding hole.

6. The high-frequency thin-wall waveguide precision drawing equipment according to claim 1, characterized in that: Two photoelectric sensors (23) arranged on the left and right are embedded on the top of the base (1), and the two photoelectric sensors (23) are both located below the screw rod (4) and close to the two ends of the screw rod (4).

7. A method for using a high-frequency thin-wall waveguide precision drawing device according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1: First, the outer mold (2) is fixed to the top of the lifting platform (13) by bolts, and the height of the lifting platform (13) is adjusted so that the through hole on the outer mold (2) is aligned with the through hole on the positioning block (19); S2: Then, the servo motor (7) is started to make the movable plate (9) drive the drawing chuck (20) to move to the initial position above the left photoelectric sensor (23), triggering the photoelectric sensor (23) signal to make the pneumatic clamp (14) move to open the drawing chuck (20); S3: Then, the tube blank (16) is inserted into the through hole of the outer mold (2) from the left side, and the mold core (15) is inserted into the tube blank (16) from the left side, the right end of the mold core (15) is inserted into the opening, and the butterfly bolt (17) is screwed so that the outer mold (2) clamps the tube blank (16); S4: Then, the pneumatic clamp (14) is started to close the drawing chuck (20) to clamp the right end of the mold core (15), and the servo motor (7) is started to move the movable plate (9) to the right through the screw (4) and the movable block (22), and drive the drawing chuck (20) to pull the mold core (15) to the right to draw the tube blank (16); S5: Then, when the movable plate (9) moves to above the right photoelectric sensor (23), the right photoelectric sensor (23) is triggered, and the servo motor (7) drives the screw (4) to reverse, so that the movable plate (9) moves back to its original position, triggering the left photoelectric sensor (23), so that the pneumatic clamp (14) moves to open the drawing chuck (20); S6: Finally, the mold core (15) and the tube blank (16) after precision drawing are taken out in turn to obtain a thin-walled waveguide tube.

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