A molding method for single PCS shipment of circuit boards without internal positioning

Abstract

The present invention provides a molding method for a circuit board without internal positioning and shipped in single PCS, comprising the following steps: S1: First, the step of adding auxiliary positioning holes to the edge of the board. The present invention provides a molding method for a circuit board without internal positioning and shipped in single PCS, by adding auxiliary positioning holes to the edge of the board, in addition to the tool hole, a positioning hole is added every 100 mm to assist in force, and each step in the entire process is closely connected and coordinated with each other, from increasing the auxiliary positioning holes to improve the processing accuracy, to reasonable typesetting spacing to improve production efficiency, to strict testing and careful gong plate operation, and finally cleaning and sorting. Each link is carefully designed and strictly controlled to ensure the production of high-quality PCB boards, avoid burrs on the surface during V-CUT, avoid the situation where the burrs on the board edge after being broken open cause large dimensional deviations, and meet customer needs and high market standards.

Description

Technical Field

[0001] The present invention relates to the field of circuit board processing, and in particular to a forming method for circuit boards without internal positioning and shipped in single PCS. Background Art

[0002] V-CUT burrs may be caused by tool wear, improper cutting speed, uneven cutting pressure, etc. The presence of burrs will affect the appearance quality of the PCB board and may cause electrical problems such as short circuits during the subsequent assembly process, or hinder the installation of components.

[0003] Size deviation may be caused by factors such as insufficient equipment precision, inaccurate positioning, incorrect process parameter settings, etc. Size deviation may cause the PCB board to not match accurately with other components, affecting the performance and reliability of the entire product. In order to reduce the risk of V-CUT burrs and size deviation, measures such as regular inspection and replacement of tools, optimization of cutting parameters, improvement of equipment precision and positioning accuracy, and strengthening of quality monitoring during the production process can be taken.

[0004] The original method for cutting circuit boards is V-CUT. V-CUT (V-shaped cutting) is a common process in PCB production, which is used to facilitate the subsequent separation of PCB boards. However, during the V-CUT process, there may be risks of V-CUT burrs and dimensional deviations.

[0005] Therefore, it is necessary to provide a circuit board molding method for single PCS shipment without internal positioning to solve the above technical problems. Summary of the Invention

[0006] The present invention provides a circuit board molding method for single PCS shipment without internal positioning, which solves the problem of V-CUT burrs and the risk of dimensional deviation that may occur during the V-CUT process.

[0007] To solve the above technical problems, the present invention provides a circuit board molding method for single PCS shipment without internal positioning, comprising the following steps:

[0008] S1: The first step is to add auxiliary positioning holes to the edge of the plate. In addition to the original tool holes, a positioning hole is added every 100mm. These auxiliary positioning holes play a vital role. They can provide more accurate positioning and more uniform force distribution in the subsequent processing, helping to reduce processing deviations caused by uneven force and improve the stability and accuracy of the entire production process.

[0009] S2: The next step is to set the PCB layout spacing. Based on the delivered PCS, the panels are assembled with a spacing of 2mm. This paneling method fully considers production efficiency and material utilization. Reasonable spacing can ensure that there is enough space between each PCS for separation and processing, and can arrange as many PCS as possible on a large board, thereby reducing production costs.

[0010] S3: Before the PCB board is formed, flying probe testing is used for quality inspection. Flying probe testing is an advanced and efficient testing method. By quickly contacting the flying probe with the test points on the PCB board, it can accurately detect whether there are short circuits, open circuits and other problems in the circuit. This step can detect potential defects in time and prevent problematic boards from entering the subsequent processing process, thereby saving time and cost and improving the qualification rate of the final product;

[0011] S4: Then comes the first rouging, which routes out the two long sides corresponding to the PCS. After this operation, the board will pass through the finished product cleaning machine, which can effectively remove impurities such as debris, dust, and oil generated during the routing process, keeping the board surface clean and providing good basic conditions for subsequent processing steps;

[0012] S5: Next is the second gong. Apply high-temperature glue on the surface of the board and rub it tightly. Then, gong the two short sides corresponding to the board. The high-temperature glue here plays a role in protecting the surface of the board to prevent scratches and damage during the gong process.

[0013] S6: The last step is to remove the glue and sort out the PCB. After that, tear the board off the high-temperature glue, and then use an air gun to blow away the dust and debris that may remain. After this series of treatments, the PCB board is ready for shipment.

[0014] Preferably, in step S3 of the circuit board forming method for single PCS shipment without internal positioning, a flying probe test device is required for flying probe test, and the flying probe test device includes: a mounting table 1;

[0015] A support device, the support device is fixedly installed on one side of the top of the mounting platform, the support device includes a support plate and a limiting groove, and an adjustment device is fixedly installed on the top of the support device, the adjustment device includes a fixing block, a threaded rod and a first servo motor;

[0016] a moving device, the moving device being threadedly engaged with an outer surface of the threaded rod, the moving device comprising a connecting block, an extension block, and a first threaded block;

[0017] A driving device, the driving device is fixedly mounted on one side of the surface of the support plate, the driving device comprising a fixed plate, a movable slot, a reciprocating screw and a second servo motor;

[0018] Mounting devices, wherein the two mounting devices are respectively threadedly engaged with two sides of the outer surface of the reciprocating screw, and the mounting devices include a clamping plate, a mounting groove, a threaded hole and a second threaded block;

[0019] A limiting device is threadedly engaged with the interior of the mounting device, and the limiting device includes a threaded column, an adjustment block, and a limiting plate.

[0020] Preferably, a testing device is provided on the top of the mounting table surface, and the testing device includes a laser rangefinder, a probe and a positioning camera.

[0021] Preferably, a base is fixedly mounted on one side of the surface of the mounting platform, and a test camera is provided on one side of the base.

[0022] Preferably, the support plate is fixedly mounted on one side of the top of the mounting platform, and the limiting groove is opened on one side of the surface of the support plate.

[0023] Preferably, the two fixing blocks are fixedly mounted on both sides of the top of the support plate, respectively, the threaded rod is rotatably mounted on one side of the fixing blocks, and the first servo motor is fixedly mounted on one side of one of the fixing blocks.

[0024] Preferably, the connecting block is slidably mounted inside the limiting groove, the extending block is fixedly mounted on one side of the connecting block, and the first threaded block is fixedly mounted on one side of the outer surface of the extending block.

[0025] Preferably, the fixed plate is fixedly installed on the other side of the support plate surface, the movable groove is opened in the middle of one side of the fixed plate, the reciprocating screw is rotatably installed inside the movable groove, and the second servo motor is fixedly installed on one side of the outer surface of the fixed plate.

[0026] Preferably, the second threaded block is threadedly engaged with the outer surface of the reciprocating screw, the clamping plate is fixedly installed on one side of the outer surface of the second threaded block, the mounting groove is opened on one side of the clamping plate surface, and the threaded hole is opened on the other side of the clamping plate surface.

[0027] Preferably, the threaded column is threadedly engaged with the interior of the threaded hole, an adjusting block is fixedly mounted on one end of the threaded column, and a limiting plate is rotatably mounted on the other end of the threaded column.

[0028] Compared with related technologies, the present invention provides a circuit board molding method for single PCS shipment without internal positioning, which has the following beneficial effects:

[0029] The present invention provides a forming method for single PCS shipment of circuit boards without internal positioning. Auxiliary positioning holes are added to the edge of the board. In addition to the tool holes, a positioning hole is added every 100 mm to assist in force bearing. The delivered PCS is used as a unit and the board is assembled at a spacing of 2 mm. A flying probe test is adopted before the PCB board is formed. The two long sides corresponding to the PCS are all gonged out and then passed through a finished product cleaning machine. High-temperature glue is applied to the surface and then the two short sides are gonged. After gong is completed, the board is torn off the high-temperature glue and blown off with an air gun for shipment. Each step in the entire process is closely connected and coordinated with each other. From increasing the auxiliary positioning holes to improve the processing accuracy, to reasonable typesetting spacing to improve production efficiency, to strict testing and careful gonging operation, and finally cleaning and sorting, each link is carefully designed and strictly controlled to ensure the production of high-quality PCB boards, avoid burrs on the surface during V-CUT, avoid the situation where the burrs on the board edges after being broken open cause large dimensional deviations, and meet customer needs and high market standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic structural diagram of a circuit board molding method for single PCS shipment without internal positioning provided by the present invention;

[0031] Figure 2 for Figure 1 A schematic side view of the support device shown;

[0032] Figure 3 for Figure 2 Schematic diagram of the support device structure shown.

[0033] Numbers in the figure: 1. Mounting table, 2. Support device, 21. Support plate, 22. Limiting groove, 3. Adjusting device, 31. Fixed block, 32. Threaded rod, 33. First servo motor, 4. Moving device, 41. Connecting block, 42. Extension block, 43. First threaded block, 5. Driving device, 51. Fixed plate, 52. Moving groove, 53. Reciprocating screw, 54. Second servo motor, 6. Mounting device, 61. Clamping plate, 62. Mounting groove, 63. Threaded hole, 64. Second threaded block, 7. Limiting device, 71. Threaded column, 72. Adjusting block, 73. Limiting plate, 8. Laser rangefinder, 9. Probe, 10. Positioning camera, 11. Base, 12. Test camera. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments. Example

[0035] A molding method for a circuit board without internal positioning and single PCS shipment includes the following steps:

[0036] S1: The first step is to add auxiliary positioning holes to the edge of the plate. In addition to the original tool holes, a positioning hole is added every 100mm. These auxiliary positioning holes play a vital role. They can provide more accurate positioning and more uniform force distribution in the subsequent processing, helping to reduce processing deviations caused by uneven force and improve the stability and accuracy of the entire production process.

[0037] S2: The next step is to set the PCB layout spacing. Based on the delivered PCS, the panels are assembled with a spacing of 2mm. This paneling method fully considers production efficiency and material utilization. Reasonable spacing can ensure that there is enough space between each PCS for separation and processing, and can arrange as many PCS as possible on a large board, thereby reducing production costs.

[0038] S3: Before the PCB board is formed, flying probe testing is used for quality inspection. Flying probe testing is an advanced and efficient testing method. By quickly contacting the flying probe with the test points on the PCB board, it can accurately detect whether there are short circuits, open circuits and other problems in the circuit. This step can detect potential defects in time and prevent problematic boards from entering the subsequent processing process, thereby saving time and cost and improving the qualification rate of the final product;

[0039] S4: Then comes the first rouging, which routes out the two long sides corresponding to the PCS. After this operation, the board will pass through the finished product cleaning machine, which can effectively remove impurities such as debris, dust, and oil generated during the routing process, keeping the board surface clean and providing good basic conditions for subsequent processing steps;

[0040] S5: Next is the second gong. Apply high-temperature glue on the surface of the board and rub it tightly. Then, gong the two short sides corresponding to the board. The high-temperature glue here plays a role in protecting the surface of the board to prevent scratches and damage during the gong process.

[0041] S6: The last step is to remove the glue and sort out the PCB. After that, tear the board off the high-temperature glue, and then use an air gun to blow away the dust and debris that may remain. After this series of treatments, the PCB board is ready for shipment.

[0042] The working principle of the circuit board molding method for single PCS shipment without internal positioning provided by the present invention is as follows:

[0043] When working, the first step is to add auxiliary positioning holes on the edge of the plate. In addition to the original tool holes, a positioning hole is added every 100mm. These auxiliary positioning holes play a vital role. They can provide more accurate positioning and more uniform force distribution in the subsequent processing, which helps to reduce the processing deviation caused by uneven force and improve the stability and accuracy of the entire production process.

[0044] The next step is to set the PCB layout spacing. Based on the delivered PCS, the panels are arranged with a spacing of 2mm. This paneling method fully considers production efficiency and material utilization. Reasonable spacing can ensure that there is enough space between each PCS for separation and processing, and can arrange as many PCS as possible on a large board, thereby reducing production costs.

[0045] Before PCB board forming, flying probe test is used for quality inspection. Flying probe test is an advanced and efficient testing method. By quickly contacting the flying probe with the test points on the PCB board, it can accurately detect whether there are short circuits, open circuits and other problems in the circuit. This step can detect potential defects in time and prevent problematic boards from entering the subsequent processing process, thus saving time and cost and improving the qualification rate of the final product.

[0046] Then comes the first rouging, which routes the two long sides corresponding to the PCS. After this operation, the board will pass through the finished product cleaning machine, which can effectively remove impurities such as debris, dust, and oil generated during the routing process, keeping the board surface clean and providing good basic conditions for subsequent processing steps;

[0047] Next is the second gong board. Apply high-temperature glue on the surface of the board and rub it tightly. Then, gong the two short sides corresponding to the gong. The high-temperature glue here plays a role in protecting the surface of the board to prevent scratches and damage during the gong process.

[0048] The last step is to tear off the glue and sort out the parts. After that, tear the board off the high-temperature glue, and then use an air gun to blow away the tiny dust and debris that may remain. After this series of treatments, the PCB board is ready for shipment.

[0049] Compared with related technologies, the present invention provides a circuit board molding method for single PCS shipment without internal positioning, which has the following beneficial effects:

[0050] The present invention provides a forming method for single PCS shipment of circuit boards without internal positioning. Auxiliary positioning holes are added to the edge of the board. In addition to the tool holes, a positioning hole is added every 100 mm to assist in force bearing. The delivered PCS is used as a unit and the board is assembled at a spacing of 2 mm. A flying probe test is adopted before the PCB board is formed. The two long sides corresponding to the PCS are all gonged out and then passed through a finished product cleaning machine. High-temperature glue is applied to the surface and then the two short sides are gonged. After gong is completed, the board is torn off the high-temperature glue and blown off with an air gun for shipment. Each step in the entire process is closely connected and coordinated with each other. From increasing the auxiliary positioning holes to improve the processing accuracy, to reasonable typesetting spacing to improve production efficiency, to strict testing and careful gonging operation, and finally cleaning and sorting, each link is carefully designed and strictly controlled to ensure the production of high-quality PCB boards, avoid burrs on the surface during V-CUT, avoid the situation where the burrs on the board edges after being broken open cause large dimensional deviations, and meet customer needs and high market standards. Example

[0051] Please refer to Figure 1 、 Figure 2 and Figure 3 Based on the first embodiment of this application, which provides a method for forming circuit boards for single-piece shipment without internal positioning, the second embodiment of this application provides another method for forming circuit boards for single-piece shipment without internal positioning. The second embodiment is merely a preferred embodiment of the first embodiment, and the implementation of the second embodiment will not affect the independent implementation of the first embodiment.

[0052] Specifically, the second embodiment of the present application provides a molding method for a circuit board without inner positioning and shipped in a single PCS. The difference is that, in the molding method for a circuit board without inner positioning and shipped in a single PCS, a flying probe test device is required during the flying probe test in step S3 of the molding method for a circuit board without inner positioning and shipped in a single PCS. The flying probe test device includes: a mounting table 1;

[0053] A support device 2 is fixedly mounted on one side of the top of the mounting platform 1. The support device 2 includes a support plate 21 and a limiting slot 22. An adjustment device 3 is fixedly mounted on the top of the support device 2. The adjustment device 3 includes a fixing block 31, a threaded rod 32, and a first servo motor 33.

[0054] a moving device 4 , wherein the moving device 4 is threadedly engaged with the outer surface of the threaded rod 32 , and the moving device 4 includes a connecting block 41 , an extending block 42 and a first threaded block 43 ;

[0055] A driving device 5 , which is fixedly mounted on one side of the surface of the support plate 21 , and includes a fixed plate 51 , a movable slot 52 , a reciprocating screw 53 and a second servo motor 54 ;

[0056] Mounting devices 6, two of the mounting devices 6 are respectively threadedly engaged with both sides of the outer surface of the reciprocating screw 53, and the mounting devices 6 include a clamping plate 61, a mounting groove 62, a threaded hole 63 and a second threaded block 64;

[0057] The limiting device 7 is threadedly engaged with the interior of the mounting device 6 , and the limiting device 7 includes a threaded column 71 , an adjustment block 72 and a limiting plate 73 .

[0058] A testing device is provided on the top of the surface of the mounting platform 1 , and the testing device includes a laser rangefinder 8 , a probe 9 and a positioning camera 10 .

[0059] A base 11 is fixedly mounted on one side of the surface of the mounting platform 1 , and a test camera 12 is provided on one side of the base 11 .

[0060] The support plate 21 is fixedly mounted on one side of the top of the mounting platform 1 , and the limiting groove 22 is opened on one side of the surface of the support plate 21 .

[0061] The two fixing blocks 31 are fixedly mounted on both sides of the top of the support plate 21 , respectively. The threaded rod 32 is rotatably mounted on one side of the fixing blocks 31 . The first servo motor 33 is fixedly mounted on one side of one of the fixing blocks 31 .

[0062] The connecting block 41 is slidably mounted inside the limiting groove 22 , the extending block 42 is fixedly mounted on one side of the connecting block 41 , and the first threaded block 43 is fixedly mounted on one side of the outer surface of the extending block 42 .

[0063] The fixed plate 51 is fixedly installed on the other side of the surface of the support plate 21, the movable groove 52 is opened in the middle of one side of the fixed plate 51, the reciprocating screw 53 is rotatably installed inside the movable groove 52, and the second servo motor 54 is fixedly installed on one side of the outer surface of the fixed plate 51.

[0064] The second threaded block 64 is threadedly engaged with the outer surface of the reciprocating screw 53, and the clamping plate 61 is fixedly installed on one side of the outer surface of the second threaded block 64. The mounting groove 62 is opened on one side of the surface of the clamping plate 61, and the threaded hole 63 is opened on the other side of the surface of the clamping plate 61.

[0065] The threaded column 71 is threadedly engaged with the interior of the threaded hole 63 . An adjustment block 72 is fixedly mounted on one end of the threaded column 71 , and a limiting plate 73 is rotatably mounted on the other end of the threaded column 71 .

[0066] The flying probe test device is an existing device, which realizes flying probe testing of the circuit board by cooperating with the laser rangefinder 8, the positioning camera 10, the test camera 12 and the probe 9.

[0067] The connecting block 41 is adapted to the limiting groove 22 , and the connecting block 41 is connected to the fixing plate 51 , so that the driving device 5 can slide on the surface of the supporting plate 21 .

[0068] The working principle of the circuit board molding method for single PCS shipment without internal positioning provided by the present invention is as follows:

[0069] During operation, the reciprocating screw 53 is first rotated by the output shaft of the second servo motor 54 to rotate the threaded engagement of the two clamping plates 61 to clamp the circuit board close to each other. The user rotates the threaded column 71 to threadably engage the threaded hole 63 to push the limiting plate 73 to move. The limiting plate 73 moves inside the mounting groove 62 and presses the circuit board onto the surface of the mounting table 1.

[0070] The output shaft of the first servo motor 33 rotates to drive the threaded rod 32 to rotate, and the threaded rod 32 rotates to engage the first threaded block 43 to drive the fixed plate 51 to slide on the surface of the support plate 21, adjust the required detection position on the circuit board surface, and maintain the required detection position to move to the bottom of the probe 9.

[0071] Compared with related technologies, the present invention provides a circuit board molding method for single PCS shipment without internal positioning, which has the following beneficial effects:

[0072] The present invention provides a forming method for single PCS shipment of circuit boards without internal positioning. The reciprocating screw 53 is driven to rotate by the output shaft of the second servo motor 54 to threadably engage the two clamping plates 61 to clamp the circuit board close to each other. The limiting device 7 is adjusted to stably limit the circuit board on the surface of the mounting table 1 to maintain the stability of the circuit board during testing. At the same time, the position of the driving device 5 can be adjusted by the first servo motor 33 and the second servo motor 54, so as to be adjusted according to the test position on the surface of the circuit board, so that each required test position on the surface of the circuit board and the probe 9 are fully contacted for testing, thereby improving the practicality and flexibility of the device.

[0073] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A molding method for circuit boards without internal positioning and single PCS shipment, characterized in that: The following steps are involved: S1: The first step is to add auxiliary positioning holes on the edge of the plate. In addition to the original tool holes, a positioning hole is added every 100mm. These auxiliary positioning holes can provide more accurate positioning and more uniform force distribution in the subsequent processing, which helps to reduce the processing deviation caused by uneven force and improve the stability and accuracy of the entire production process. S2: The next step is to set the PCB layout spacing. The layout is done based on the delivered PCS and the spacing is 2mm. S3: Before the PCB board is formed, a flying probe test is used for quality inspection. By quickly contacting the flying probe with the test points on the PCB board, it can accurately detect whether there are short circuits or open circuits in the circuit. This step can detect potential defects in time and prevent problematic boards from entering the subsequent processing flow, thus saving time and cost and improving the qualification rate of the final product. S4: Then comes the first rouging, which routes the two long sides corresponding to the PCS. After this operation, the board will pass through the finished product cleaning machine, which can effectively remove the debris, dust and oil impurities generated during the routing process, keep the board surface clean, and provide good basic conditions for subsequent processing steps; S5: Next is the second gong. Apply high-temperature glue to the surface of the board and stick it tightly. Then, apply the glue to the two short sides corresponding to the gong. The high-temperature glue here protects the surface of the board to prevent scratches and damage during the gong process. S6: The last step is to remove the glue and sort out the PCB. After the PCB is removed from the high-temperature glue, an air gun is used to blow away any remaining dust and debris. After this series of treatments, the PCB is ready for shipment. In step S3 of the circuit board forming method for single PCS shipment without internal positioning, a flying probe test device is required for flying probe test, and the flying probe test device includes: a mounting table; A support device, the support device is fixedly installed on one side of the top of the mounting platform, the support device includes a support plate and a limiting groove, and an adjustment device is fixedly installed on the top of the support device, the adjustment device includes a fixing block, a threaded rod and a first servo motor; a moving device, the moving device being threadedly engaged with an outer surface of the threaded rod, the moving device comprising a connecting block, an extension block, and a first threaded block; A driving device, the driving device is fixedly mounted on one side of the surface of the support plate, the driving device comprising a fixed plate, a movable slot, a reciprocating screw and a second servo motor; Mounting devices, wherein the two mounting devices are respectively threadedly engaged with two sides of the outer surface of the reciprocating screw, and the mounting devices include a clamping plate, a mounting groove, a threaded hole and a second threaded block; A limiting device is threadedly engaged with the interior of the mounting device, and the limiting device includes a threaded column, an adjustment block, and a limiting plate.

2. The molding method for single PCS shipment of circuit boards without internal positioning according to claim 1, characterized in that: A testing device is provided on the top of the mounting table surface. The testing device includes a laser rangefinder, a probe and a positioning camera.

3. The molding method for single PCS shipment of circuit boards without internal positioning according to claim 1, characterized in that: A base is fixedly mounted on one side of the mounting platform surface, and a test camera is provided on one side of the base.

4. The method for forming a circuit board without internal positioning and shipping a single PCS according to claim 1, characterized in that: The support plate is fixedly mounted on one side of the top of the mounting platform, and the limiting groove is opened on one side of the surface of the support plate.

5. The molding method for single PCS shipment of circuit boards without internal positioning according to claim 1, characterized in that: The two fixing blocks are respectively fixedly mounted on both sides of the top of the support plate, the threaded rod is rotatably mounted on one side of the fixing blocks, and the first servo motor is fixedly mounted on one side of one of the fixing blocks.

6. The method for forming a circuit board without internal positioning and shipping a single PCS according to claim 1, characterized in that: The connecting block is slidably mounted inside the limiting groove, the extending block is fixedly mounted on one side of the connecting block, and the first threaded block is fixedly mounted on one side of the outer surface of the extending block.

7. The method for forming a circuit board without internal positioning and shipping a single PCS according to claim 1, characterized in that: The fixed plate is fixedly installed on the other side of the support plate surface, the movable groove is opened in the middle of one side of the fixed plate, the reciprocating screw is rotatably installed inside the movable groove, and the second servo motor is fixedly installed on one side of the outer surface of the fixed plate.

8. The method for forming a circuit board without internal positioning and shipping a single PCS according to claim 1, characterized in that: The second threaded block is threadedly engaged with the outer surface of the reciprocating screw, the clamping plate is fixedly installed on one side of the outer surface of the second threaded block, the mounting groove is opened on one side of the clamping plate surface, and the threaded hole is opened on the other side of the clamping plate surface.

9. The method for forming a circuit board without internal positioning and shipping a single PCS according to claim 1, characterized in that: The threaded column is threadedly engaged with the interior of the threaded hole. An adjusting block is fixedly mounted on one end of the threaded column, and a limiting plate is rotatably mounted on the other end of the threaded column.

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