A numerically controlled steel pipe letter rolling machine

Abstract

This application relates to the field of rolling character machines, and in particular to a numerically controlled steel pipe rolling character machine, which includes a machine table, a rolling character die, and a lower die assembly installed on the machine table. It is characterized in that: a first driving assembly for driving the rolling character die to slide down is arranged on the machine table, and a second driving assembly for driving the rolling character die to horizontally slide is also arranged on the machine table; the rolling character die includes a rolling character guide plate and a die head installed on the rolling character guide plate. An installation groove is formed on the rolling character guide plate. The die head vertically slides in the installation groove, and a first spring is arranged between the die head and the inner wall of the installation groove. An adjusting rod is rotatably arranged in the installation groove, and an abutting block is fixedly arranged on the adjusting rod; a screwing assembly is arranged at one end of the adjusting rod extending out of the rolling character guide plate to facilitate driving the adjusting rod to rotate; during adjustment, the adjusting rod is driven to rotate so that the abutting block abuts against the die head and vertically moves down, thereby realizing fine adjustment of the die head.

Description

Technical Field

[0001] This application relates to the field of rolling character machines, and in particular to a numerically controlled steel pipe rolling character machine. Background Art

[0002] Torque wrenches have been widely used in tightening bolts. There is a split-type torque wrench with torque value markings on the steel pipe of the wrench. Some are made by a laser marking machine, but the engraving is very shallow, and the engraved lines of the force value markings are prone to wear, making them blurred. Most users prefer to permanently emboss the engraved lines on the steel pipe, which has high requirements for the clarity of the engraved lines and characters. Moreover, the hardness of the steel pipe materials in each batch is different, resulting in varying depths of the embossed characters and affecting the product quality.

[0003] During the known rolling process, the downward pressure values for steel pipes of different diameters are usually set as standard. During the rolling process, only the diameter of the steel pipe needs to be entered. Usually, the hardness of the steel pipe before rolling is also known. For steel pipes with different hardnesses, especially those with a hardness greater than that of the same batch, deeper embossing is usually achieved by adjusting the height of the rolling character die.

[0004] During the actual processing, it is known that the minimum unit for lowering the rolling character die may far exceed the actual height to be adjusted. Among the steel pipes of the same batch, the hardness of individual steel pipes does not vary greatly. Therefore, usually only a few millimeters of fine adjustment are required, but it is difficult to achieve this well in the existing rolling character equipment, which is an area that urgently needs improvement. Summary of the Invention

[0005] In order to make the downward pressure height of the steel pipe rolling character machine adjustable for fine-tuning and ensure consistent quality of the embossed steel pipes in the same batch, this application provides a numerically controlled steel pipe rolling character machine.

[0006] A numerically controlled steel pipe rolling character machine provided by this application adopts the following technical solutions:

[0007] A numerically controlled steel pipe rolling character machine includes a machine table, a rolling character die, and a lower die assembly installed on the machine table. A first driving assembly for driving the rolling character die to slide downward is provided on the machine table, and a second driving assembly for driving the rolling character die to horizontally slide is also provided on the machine table;

[0008] The rolling character die includes a rolling character guide plate and a die head installed on the rolling character guide plate. An installation groove is formed on the rolling character guide plate. The die head vertically slides in the installation groove, and a first spring is arranged between the die head and the inner wall of the installation groove. An adjusting rod is rotatably arranged in the installation groove, and an abutting block is fixedly arranged on the adjusting rod;

[0009] The twisting assembly is arranged at one end of the adjusting rod extending out of the roller guide plate, so as to drive the adjusting rod to rotate; when adjusting, the adjusting rod is driven to rotate, so that the abutting block abuts against the die head and moves vertically downward.

[0010] By adopting the above technical solution, the steel pipe is placed on the lower die assembly. When it is known that the hardness of the steel pipe is relatively large, fine-tuning is required to ensure clear engraving. The adjusting rod is rotated by twisting the assembly to rotate the adjusting rod and drive the abutment block to rotate. The abutment block abuts the die head to slide and at the same time, the first spring is stretched, thereby achieving the effect of fine-tuning. During the actual processing, the control box on one side of the machine controls the rolling die to move down to the specified position, and then the second drive assembly is used to drive the rolling die to slide in a direction perpendicular to the axial direction of the steel pipe, thereby achieving imprinting.

[0011] Optionally, the first driving assembly includes a slide plate sliding on the machine platform, a bracket tube fixed on the upper end of the slide plate, a vertical planetary reducer fixed on the machine platform, a vertical lead screw coaxially fixed on the transmission shaft of the vertical planetary reducer, and a vertical servo motor fixed on the machine platform. The roller guide plate is installed on the slide plate, the vertical servo motor is transmission-connected to the vertical planetary reducer, and the vertical lead screw is threadedly connected to the bracket tube.

[0012] By adopting the above technical solution, when the rolling die is driven to move vertically downward, the rotation shaft of the vertical servo motor is controlled to rotate, and the vertical lead screw rotates synchronously under the transmission action of the vertical planetary reducer, thereby driving the bracket tube and the slide plate to move vertically downward.

[0013] Optionally, both sides of the machine are provided with embedding grooves, and a scale is embedded in the embedding grooves.

[0014] By adopting the above technical solution, the scale can enable the staff to clearly judge whether the downward height is correct, thereby further ensuring the rolling quality of the steel pipe.

[0015] Optionally, the second driving assembly includes a transverse servo motor fixed on the slide plate;

[0016] The transverse planetary reducer is fixed on the slide plate and is drivingly connected to the transverse servo motor;

[0017] The horizontal lead screw is rotatably connected to the slide plate and is connected to the horizontal planetary reducer through a coupling; the roller guide plate slides horizontally on the slide plate and is threadedly connected to the horizontal lead screw.

[0018] By adopting the above technical solution, the rotation of the shaft of the horizontal servo motor is controlled by the PLC control box, and the horizontal planetary reducer is used to transmit the transmission, so that the horizontal screw rotates synchronously, thereby driving the roller guide plate to move along the axial direction of the horizontal screw.

[0019] Optionally, the abutting block is spiral along the length direction of the adjusting rod, and the spiral abutting block is wound around the side wall of the adjusting rod, and the width of the abutting block gradually increases along the spiral direction.

[0020] By adopting the above technical solution, since the width continuously increases, the adjustment is made more precise.

[0021] Optionally, the twisting assembly includes a prism. A prism groove is provided at one end of the adjusting rod extending out of the rolling character guide plate, and the prism slides in the prism groove;

[0022] A circular plate is fixed to the end of the prism. A plurality of grooves are provided at one end of the circular plate facing away from the prism. A ejector rod slides in the grooves, and a second spring is further provided in the grooves for driving the ejector rod to extend out of the grooves;

[0023] A third spring is sleeved outside the prism;

[0024] A clamping plate is fixed to the side wall of the rolling character guide plate. In the initial state, the clamping plate presses part of the ejector rods and restricts the rotation of the circular plate.

[0025] By adopting the above technical solution, in the initial state, the clamping plate presses part of the ejector rods to restrict the rotation of the circular plate, and further makes it difficult for the adjusting rod to rotate; when it is necessary to adjust the downward displacement of the die head, the wrench first presses a plurality of ejector rods. A groove with the same shape as the end of the wrench is formed between the plurality of ejector rods and makes it difficult for the wrench and the circular plate to rotate relative to each other. The extrusion causes the clamping plate to disengage from the circular plate. At the same time, the wrench is twisted, and the wrench drives the circular plate and the adjusting rod to rotate, achieving the adjustment effect.

[0026] Optionally, a pointer is fixed to the side wall of the circular plate, and an annular scale bar is fixed to the side wall of the rolling character guide plate, and the pointer is used in cooperation with the annular scale bar.

[0027] By adopting the above technical solution, the staff can accurately twist the circular plate to adjust the height of the downward movement of the die head.

[0028] Optionally, the lower die assembly includes a carriage mounted on the machine table;

[0029] There are two idler wheels, and both idler wheels are rotatably connected to the upper surface of the carriage for supporting the steel pipe. The axial direction of the idler wheels is perpendicular to the sliding direction of the rolling character guide plate;

[0030] A positioning plate is fixed to one side of the carriage, and the end of the steel pipe can abut against the side wall of the positioning plate;

[0031] A positioning cylinder is fixed to the machine table;

[0032] A steel needle is vertically penetrated through the machine table, and the steel needle is fixedly connected to the piston rod of the positioning cylinder.

[0033] It is known that steel pipes are mainly used for processing wrenches. Therefore, during the blanking process, a through hole is usually opened at one end of the steel pipe. By adopting the above technical solution, the steel pipe is placed between two idler wheels, and the end of the steel pipe with the hole is abutted against the positioning plate. By controlling the piston rod of the positioning cylinder to extend, the steel needle is inserted into the hole, thereby realizing the positioning and placement of the steel pipe.

[0034] In summary, the present application includes at least one of the following beneficial technical effects:

[0035] It is possible to perform engraving processing on steel pipes with different hardnesses. During the processing, only by finely adjusting the downward moving die head, the quality of engraving can be guaranteed; the adjustment is convenient. Description of the Drawings

[0036] Figure 1 It is the front view of the overall structure of this embodiment.

[0037] Figure 2 It is the side view of the overall structure of this embodiment.

[0038] Figure 3 It is the schematic diagram of the overall structure of the rolling letter die in this embodiment.

[0039] Figure 4 It is the schematic diagram of the rolling letter die in this embodiment, mainly used to show the abutting block and the twisting component.

[0040] Figure 5 It is the exploded view of the twisting component part in this embodiment.

[0041] Reference numerals: 1, machine table; 2, rolling letter die; 3, lower die assembly; 4, first driving component; 5, second driving component; 6, rolling letter guide plate; 7, die head; 8, installation groove; 9, first spring; 10, adjusting rod; 11, abutting block; 12, twisting component; 13, sliding plate; 14, support cylinder; 15, vertical planetary reducer; 16, vertical lead screw; 17, vertical servo motor; 18, embedding groove; 19, scale; 20, horizontal servo motor; 21, horizontal planetary reducer; 22, horizontal lead screw; 23, prism; 24, prism groove; 25, circular plate; 26, groove; 27, ejector rod; 28, second spring; 29, third spring; 30, clamping plate; 31, pointer; 32, annular scale bar; 33, idler wheel; 34, positioning plate; 35, positioning cylinder; 36, steel needle. Detailed Description of the Invention

[0042] The following will further elaborate on the present application in conjunction with the attached Figures 1-5 for a more detailed description.

[0043] The embodiment of the present application discloses a numerical control steel pipe rolling letter machine.

[0044] In the actual blanking process of the steel pipe used to produce wrenches, a through hole is opened at one end of the steel pipe; at the same time, it is also necessary to emboss scales on the outer side of the steel pipe to indicate the applicable torque size.

[0045] Referring to Figure 1 and Figure 2 , a numerical control steel pipe rolling letter machine includes a machine table 1, and a lower die assembly 3 is arranged on the side wall of the machine table 1, and a rolling letter die 2 is arranged above the lower die assembly 3. A first driving component 4 for driving the rolling letter die 2 to slide down is arranged on the machine table 1. During the actual processing, the first driving component 4 drives the rolling letter die 2 to move down, so that the steel pipe is located between the lower die assembly 3 and the rolling letter die 2. A second driving component 5 for driving the rolling letter die 2 to horizontally slide is also arranged on the machine table 1, and rolling letter embossing can be realized through the second driving component 5.

[0046] Referring to Figure 1 , in order to realize accurately adjusting the downward displacement of the rolling letter die 2 in a numerical control manner, the first driving component 4 includes a sliding plate 13 which slides vertically on the machine table 1, and also includes a support cylinder 14 which is arranged vertically. The lower end of the support cylinder 14 is fixedly installed on the upper surface of the sliding plate 13.

[0047] Referring to Figure 1 , the first driving component 4 further includes a vertical servo motor 17, a vertical planetary reducer 15 and a vertical lead screw 16. The vertical servo motor 17 is also fixedly installed on the side wall of the machine table 1, and the vertical planetary reducer 15 is fixedly installed on the side wall of the machine table 1.

[0048] Referring to Figure 1 , the vertical servo motor 17 is electrically connected to the PLC controller outside one side of the machine table 1. The drive shaft of the vertical servo motor 17 is coaxially and fixedly connected to the transmission shaft of the vertical planetary reducer 15. The vertical lead screw 16 is rotatably connected to the side wall of the machine table 1 and is arranged vertically. The upper end of the vertical lead screw 16 is coaxially and fixedly connected to the power output shaft of the vertical planetary reducer 15. The vertical lead screw 16 is threadedly connected to the support cylinder 14. When driving the rolling letter die 2 to vertically move down, the rotation shaft of the vertical servo motor 17 is controlled by the PLC controller to rotate. After being transmitted by the vertical planetary reducer 15, the vertical lead screw 16 rotates synchronously, so as to drive the rolling letter die 2 to vertically slide down.

[0049] Referring to Figure 1 , in order to facilitate the staff to observe whether the downward height of the rolling letter die 2 is accurate, embedding grooves 18 are opened on both side walls of the machine table 1, and a scale 19 is embedded and installed in the embedding grooves 18. The scale 19 is marked with a height value for real-time displaying the falling height of the rolling letter die 2.

[0050] Referring to Figure 3 and Figure 4, the rolling character die 2 includes a rolling character guide plate 6 and a die head 7. The rolling character guide plate 6 is installed on the slide plate 13. An installation groove 8 is formed on the bottom surface of the rolling character guide plate 6. The die head 7 slides vertically in the inner cavity of the installation groove 8. In order to realize fine-tuning the downward movement amount of the die head 7, an adjusting rod 10 is rotatably arranged in the installation groove 8. An abutting block 11 is fixedly arranged on the adjusting rod 10, and the abutting block 11 is used to abut against the die head 7 to move downward.

[0051] Referring to Figure 4 , since the opening of the installation groove 8 is arranged downward, in order to make it difficult for the abutting block 11 to move downward under its own gravity, a first spring 9 is also arranged in the installation groove 8. One end of the first spring 9 is fixedly installed in the inner cavity of the installation groove 8, and the other end of the first spring 9 is fixed on the side wall of the die head 7.

[0052] Referring to Figure 4 , in order to make the fine-tuning range of the abutting block 11 large enough and not restricted by the minimum downward movement amount during the adjustment process, the abutting block 11 is arranged in a spiral shape. And the abutting block 11 is wound and fixed on the side wall of the adjusting rod 10 along the length direction of the adjusting rod 10.

[0053] Referring to Figure 4 , the width of the abutting block 11 is gradually increased along the spiral direction of the abutting block 11. Thus, when adjusting the downward movement of the die head 7, rotate the adjusting rod 10 and make the rotated adjusting rod 10 fixed. The downward movement amount of the die head 7 is fine-tuned by abutting the die head 7 with the spiral edge of the abutting block 11.

[0054] Referring to Figure 4 and Figure 5 , in order to facilitate the rotation of the adjusting rod 10 and limit the rotation of the adjusting rod 10 after adjustment. A twisting assembly 12 is arranged at the end of the adjusting rod 10 extending out of the rolling character die 2 plate. The twisting assembly 12 includes a prism 23, a circular plate 25, a third spring 29 and a clamping plate 30. A prism groove 24 is formed at the end of the adjusting rod 10 extending out of the rolling character guide plate 6. Specifically, the cross-sectional shape of the prism groove 24 can be pentagonal; the prism 23 slides in the prism groove 24, and the circular plate 25 is fixedly installed at the end of the prism 23 extending out of the prism groove 24. The third spring 29 is sleeved on the prism 23. One end of the third spring 29 is fixed on the side wall of the circular plate 25, and the other end of the third spring 29 is fixed on the end side wall of the adjusting rod 10.

[0055] Referring to Figure 5In order to ensure that the circular plate 25 can be fixed and limited after being rotated, a plurality of grooves 26 are provided on the side of the circular plate 25 away from the prism 23. The plurality of grooves 26 are evenly spaced, and a push rod 27 is slidably provided in the groove 26. A second spring 28 is also provided in the groove 26. One end of the second spring 28 is fixed to the inner cavity side wall of the groove 26, and the other end of the second spring 28 is fixed to the end side wall of the push rod 27.

[0056] Reference Figure 4 and Figure 5 The clamping plate 30 is fixed on the side wall of the character rolling guide plate 6. In the initial state, under the action of the second spring 28, the plurality of ejector pins 27 are pressed into the inner cavity of the groove 26 by the clamping plate 30. Thus, a groove for clamping the shape of the end of the clamping plate 30 is formed between the plurality of ejector pins 27. When the adjusting rod 10 needs to be turned, a wrench is used to contact the ejector pins 27, so that the shape of the end of the wrench is formed between the plurality of ejector pins 27, and the end of the wrench is clamped. When the wrench is turned, the circular plate 25 is usually pressed toward the direction of the character rolling guide plate 6, so that the circular plate 25 is separated from the clamping plate 30. At this time, the adjusting rod 10 is turned to realize the rotation of the abutment block 11.

[0057] Reference Figure 4 and Figure 5 In order to make the twisting adjustment more accurate, a pointer 31 is fixedly installed on the side wall of the circular plate 25. An annular scale bar 32 is provided on the side wall of the roller guide plate 6. The annular scale bar 32 is coaxially arranged with the adjustment rod 10. When the staff adjusts the die head 7 to move downward, the twisting can be adjusted by observing the scale indicated by the pointer 31.

[0058] Reference Figure 2 and Figure 3 , after placing the steel pipe to be processed between the lower die assembly 3 and the die head 7, it is necessary to drive the die head 7 to move along the axis perpendicular to the steel pipe, so as to achieve the effect of engraving. The second drive assembly 5 includes a transverse servo motor 20, a transverse planetary reducer 21 and a transverse lead screw 22. The transverse servo motor 20 is fixedly mounted on the end side wall of the slide 13, and the transverse planetary reducer 21 is also fixedly mounted on the side wall of the slide 13, and the transverse servo motor 20 and the transverse planetary reducer 21 are transmission-connected. The transverse lead screw 22 is rotationally connected to the side wall of the slide 13, and one end of the transverse lead screw 22 is fixedly connected to the output drive shaft of the transverse planetary reducer 21 through a coupling. The transverse lead screw 22 is threadedly connected to the roller guide plate 6.

[0059] Reference Figure 2 and Figure 3 The horizontal servo motor 20 is also connected to the PLC device by electrical connection, driving the shaft of the horizontal servo motor 20 to rotate. Under the transmission of the horizontal planetary reducer 21, the horizontal lead screw 22 rotates synchronously, thereby driving the roller guide plate 6 to move vertically along the axial direction of the steel pipe.

[0060] Referring to Figure 2 , in order to ensure clear engraving and accurate engraving positions, the lower die assembly 3 includes a bracket and a drag wheel 33. The bracket is fixedly installed on the machine table 1. There are two drag wheels 33, and both drag wheels 33 are rotatably connected to the bracket. During actual use, the steel pipe is placed between the two drag wheels 33.

[0061] Referring to Figure 1 and Figure 2 , at the same time, a positioning plate 34 is provided on one side of the bracket. The positioning plate 34 is used as a backing during the processing. A positioning cylinder 35 is provided on the machine table 1. Since one end of the steel pipe is provided with a hole, a steel needle 36 is fixed to the end of the piston rod of the positioning cylinder 35. During actual processing, the end with the hole is made to abut against the side wall of the positioning plate 34. The piston rod of the positioning cylinder 35 is driven to extend by the PLC device, and the steel needle 36 is inserted into the hole to achieve the positioning of the steel pipe, thus facilitating the actual processing.

[0062] The implementation principle of a numerically controlled steel pipe rolling letter machine in an embodiment of the present application is as follows: During the processing, the end of the steel pipe with a hole is abutted against the side wall of the positioning plate 34, so that the steel needle 36 is inserted into the hole. The rotation of the shaft of the vertical servo motor 17 is driven, so that the slide plate 13 slides vertically downward. When engraving a steel pipe with a relatively high hardness, the round plate 25 is pressed and rotated while being clamped, so that the adjusting rod 10 rotates synchronously, and thus the abutting block 11 presses the die head 7 to move vertically downward. After the adjustment is completed, the round plate 25 is released. Under the action of the second spring 28, the round plate 25 rebounds and is fixed to the clamping plate 30. At this time, the rotation of the shaft of the horizontal servo motor 20 is controlled, so that the rolling letter slide plate 13 moves along a direction perpendicular to the steel pipe, thereby achieving the engraving.

[0063] The above are all preferred embodiments of the present application. The protection scope of the present application is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A numerical control steel pipe rolling letter machine, comprising a machine table (1), a rolling letter die (2), and a lower die assembly (3) installed on the machine table (1), characterized in that: The machine platform (1) is provided with a first driving component (4) for driving the rolling die (2) to slide downward, and the machine platform (1) is also provided with a second driving component (5) for driving the rolling die (2) to slide horizontally; The character rolling die (2) comprises a character rolling guide plate (6) and a die head (7) mounted on the character rolling guide plate (6); a mounting groove (8) is provided on the character rolling guide plate (6); the die head (7) vertically slides in the mounting groove (8); a first spring (9) is provided between the die head (7) and the inner wall of the mounting groove (8); an adjusting rod (10) is rotatably provided in the mounting groove (8); and an abutment block (11) is fixedly provided on the adjusting rod (10); The twisting assembly (12) is arranged at one end of the adjusting rod (10) extending outside the character rolling guide plate (6) to facilitate driving the adjusting rod (10) to rotate; when adjusting, the adjusting rod (10) is driven to rotate so that the abutting block (11) abuts against the die head (7) and moves vertically downward.

2. The numerically controlled steel pipe rolling character machine according to claim 1, wherein: The first driving assembly (4) comprises a slide plate (13) sliding on the machine platform (1), a support tube (14) fixed on the upper end of the slide plate (13), a vertical planetary reducer (15) fixed on the machine platform (1), a vertical lead screw (16) coaxially fixed on the transmission shaft of the vertical planetary reducer (15), and a vertical servo motor (17) fixed on the machine platform (1); the character rolling guide plate (6) is mounted on the slide plate (13); the vertical servo motor (17) is transmission-connected to the vertical planetary reducer (15); and the vertical lead screw (16) is threadedly connected to the support tube (14).

3. A numerical control steel pipe rolling letter machine according to claim 2, characterized in that: Both sides of the machine platform (1) are provided with embedding grooves (18), and a scale (19) is embedded in the embedding grooves (18).

4. A numerically controlled steel pipe rolling letter machine according to claim 2, characterized in that: The second driving assembly (5) comprises a transverse servo motor (20) fixed on the slide plate (13); A transverse planetary reducer (21) is fixed on the slide plate (13) and is drivingly connected to the transverse servo motor (20); The horizontal lead screw (22) is rotatably connected to the slide plate (13) and is connected to the horizontal planetary reducer (21) through a coupling; the roller guide plate (6) slides horizontally on the slide plate (13) and is threadedly connected to the horizontal lead screw (22).

5. The numerically controlled steel pipe rolling character machine according to claim 1, wherein: The abutment block (11) is spirally shaped along the length direction of the adjusting rod (10), and the spirally shaped abutment block (11) is wound on the side wall of the adjusting rod (10), and the width of the abutment block (11) gradually increases along the spiral direction.

6. The numerically controlled steel pipe rolling letter machine according to claim 5, characterized in that: The twisting assembly (12) comprises a prism (23), one end of the adjusting rod (10) extending out of the roller guide plate (6) is provided with a prism groove (24), and the prism (23) slides in the prism groove (24); A circular plate (25) is fixed to the end of the prism (23); a plurality of grooves (26) are formed at one end of the circular plate (25) away from the prism (23); a push rod (27) is slidably disposed in the groove (26); a second spring (28) is also disposed in the groove (26) for driving the push rod (27) to extend out of the groove (26); A third spring (29), wherein the third spring (29) is sleeved outside the prism (23); The clamping plate (30) is fixed on the side wall of the rolling character guide plate (6). In the initial state, the clamping plate (30) presses part of the ejector rod (27) and restricts the rotation of the circular plate (25).

7. The numerically controlled steel pipe rolling letter machine according to claim 6, wherein: A pointer (31) is fixed on the side wall of the circular plate (25), and an annular scale bar (32) is fixed on the side wall of the rolling character guide plate (6). The pointer (31) is used in cooperation with the annular scale bar (32).

8. A numerical control steel pipe rolling character machine according to claim 1, characterized in that: The lower die assembly (3) includes a carriage mounted on the machine table (1). Two idler wheels (33) are provided, and both idler wheels (33) are rotatably connected to the upper surface of the carriage for supporting the steel pipe. The axial direction of the idler wheels (33) is perpendicular to the sliding direction of the rolling character guide plate (6). A positioning plate (34) is fixed on one side of the carriage, and the end of the steel pipe can abut against the side wall of the positioning plate (34). A positioning cylinder (35) is fixed on the machine table (1). A steel needle (36) is vertically inserted through the machine table (1), and the steel needle (36) is fixedly connected to the piston rod of the positioning cylinder (35).

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