A screw assembly system for reworking a circumferential screw hole

Abstract

The application provides a screw assembly system for circumferential screw hole reprocessing, a servo motor driven index plate is fixedly arranged on a rack, the index plate is connected with a fixed clamp, a reprocessing mechanism is arranged on the rack at one side of the index plate, a laser sensor probe is further arranged on the rack, the laser sensor probe is located between the included angle formed by the reprocessing mechanism and a screw locking mechanism and faces the fixed clamp, the servo motor, the reprocessing mechanism and the laser sensor probe are all connected to a programmable controller for action control. The structure of the application is integrally designed through the functions of thread passing and screw locking, so that the positioning actions of two processes are shared, the precision of screw locking is improved, the structure of the chuck type is designed to adapt to reprocessing workpieces of circumferential screw holes with various diameters, the structure adopts the combination of the diffuse reflection type laser sensor and simple data processing, is accurate in positioning, has a low failure rate, has a high work efficiency, can greatly save equipment cost and the like.

Description

Technical Field

[0001] This invention relates to a screw hole machining machine, and more particularly to a screw assembly system for remachining circumferential screw holes. Background Technology

[0002] Currently, small and medium-sized mechanical parts processing enterprises are still labor-intensive, with low levels of automation. Assembly processes still rely heavily on manual labor. The screw fastening process, in particular, involves numerous upstream and downstream assembly steps that are extremely resource-intensive. Existing technologies involve drilling screw holes and applying a coating to the workpiece before pre-assembling the screws. During screw assembly, for workpieces with screw holes distributed on the same plane, machine vision positioning combined with a screw fastening mechanism or a robotic arm can be used to complete the screw fastening process. Positioning is achieved by using an industrial CCD camera to capture real-time images of the workpiece, replacing human eyes. The camera then transmits the captured images to a computer for image processing. However, this method is costly and has limitations because the sample is prone to positional shifts during visual fastening. If the screw holes are not on a planar distribution, an automatic correction system is required, leading to low efficiency. Furthermore, the upstream process for screw fastening requires pre-processing to remove residual plastic powder from the screw holes. A tap is then used to re-screw the remaining plastic powder out of the screw holes. Therefore, the mainstream method for screw fastening workpieces with non-planar screw holes is still done manually; the saying "going to the factory to fasten screws" is not a joke. Summary of the Invention

[0003] To overcome the shortcomings of existing technologies, this invention provides a screw assembly system for reprocessing circumferential screw holes. For circumferentially machined parts, the screw hole is initially positioned during the thread penetration process, and the screw is re-attached using this positioning. The system completes two assembly actions while inspecting the sample, reducing machine dependence and improving work efficiency.

[0004] This invention is achieved through the following technical solution: a screw assembly system for reprocessing circumferential screw holes, comprising a screw fastening mechanism mounted above a frame, the screw fastening mechanism being connected to a programmable controller for motion control, a servo motor-driven indexing plate fixedly mounted on the frame, the indexing plate being connected to a fixing fixture, a reprocessing mechanism mounted on one side of the indexing plate on the frame, and a laser sensor probe mounted on the frame, the laser sensor probe being located between the reprocessing mechanism and the screw fastening mechanism and facing the fixing fixture, the servo motor, the reprocessing mechanism, and the laser sensor probe all being connected to the programmable controller for motion control.

[0005] In the above scheme, the reprocessing mechanism includes a two-axis drive device and a wire-penetrating electric screwdriver connected to the two-axis drive device. The two-axis drive device consists of a transverse movement mechanism and a longitudinal movement mechanism, and the wire-penetrating electric screwdriver is located on the transverse movement mechanism.

[0006] In the above scheme, the fixing fixture is a chuck type, the wire-penetrating electric screwdriver is located on one side of the circumference of the fixing fixture and intersects the axis of the fixing fixture horizontally, the screw fastening mechanism is located directly above the fixing fixture, and the laser sensor probe (8) is located at the 45-degree equidistant angle formed by the wire-penetrating electric screwdriver and the screw fastening mechanism.

[0007] In the above scheme, the fixing fixture is a three-jaw chuck.

[0008] In the above scheme, the screw fastening mechanism includes an N-type frame, which is mounted on the machine frame, and the laser sensor probe is fixed by a support arm hinged to the N-type frame.

[0009] In the above scheme, a linear feeder is also provided on one side of the screw fastening mechanism, and the linear feeder uses a vibratory feeder to feed the screws.

[0010] The positioning principle of circumferential screw holes:

[0011] ① Drive: Servo motor driven electric indexing table can provide circumferential rotation force for the workpiece. In automatic control systems, it is often used as an actuator. It can convert the received electrical signal into angular displacement or angular velocity output on the motor shaft. It is commonly used in high-precision position control applications. The indexing table is a machine tool accessory that clamps the workpiece on the chuck or between two centers and makes it rotate, index, and position.

[0012] ② Adjusting the sensor position and output status: The laser sensor is extremely sensitive to changes in position. The laser emitted by the sensor will form a red spot with a size of approximately 1mm on the workpiece surface. By adjusting the position of the laser sensor probe, it is essential to ensure that the light spot formed by the sensor on the workpiece surface is on the same plane as the center of the circumferentially distributed holes. Adjust the output status of the laser sensor probe so that it is normally open when the light spot illuminates the ring wall, at which point the sensor status is low.

[0013] ③ Indexing and Hole Position Detection: Assuming the programmable controller needs to send 36,000 pulses to make the motor rotate one revolution, and the reduction ratio of the indexing plate is 1:10, each pulse can rotate the workpiece by 0.001 degrees. To make the workpiece rotate one revolution, the programmable controller needs to send 360,000 pulse signals, so it has extremely high positional accuracy.

[0014] When the indexing plate rotates, and the laser sensor probe shines from the hole wall onto the edge of the hole, the sensor's photosensitive value changes abruptly. Its output state changes from normally open to normally closed, and it simultaneously sends a rising edge signal to the programmable controller (PLC). This signal causes the PLC to record the total number of pulses sent to the servo motor, denoted as D1. Similarly, if the workpiece has six holes around its circumference, during one rotation, the sensor will shine into the hole from the circumference six times. The PLC will record the total number of pulses emitted when the rising edge is triggered at each of these six holes, denoted as D1, D2, D3, D4, D5, and D6 respectively.

[0015] D1 to D6 are only the pulse values ​​when the sensor detects the edge of the hole. To know the pulse value corresponding to the center of the hole, the programmable controller needs to perform inverse trigonometric function calculations. Connect the upper and lower edges of the screw hole. From a frontal view, this line is equivalent to a chord of the circle containing the outer wall of the workpiece. Draw a perpendicular line from the midpoint of the chord to the center of the circle. This perpendicular line, the radius of the circle, and half of the chord form a right triangle ABC. Given the radius of the workpiece and the hole diameter (i.e., the chord length), the angle of the vertex of this right triangle can be calculated using the inverse trigonometric function ARCSIN. This angle is the angle between the edge of the hole and the center of the hole. Then, convert the angle value into a pulse count (0.001 degrees is one pulse), denoted as E. Add E to the pulse count at the edge of each hole to obtain the pulse count corresponding to the center of each hole, denoted as P(x), i.e., (D1+E=P1, D2+E=P2, and so on).

[0016] The P value represents the number of pulses that the programmable controller needs to send when the axis of the circle containing each screw hole rotates from its initial position to coincide with the light from the sensor. Since the angle between the sensor installation position and the tap axis of the horizontal reprocessing module is 45 degrees, in order to enable each hole to rotate to the horizontal direction, the number of pulses corresponding to 45 degrees needs to be added to F(x). The resulting value B(X) is the number of pulses that the programmable controller needs to send when the axis of each screw hole rotates from its initial position to the axis of the horizontally placed wire-penetrating device tap, i.e., B(X) = P(x) + 45000.

[0017] In this way, the number of pulses required by the programmable controller to rotate the workpiece from the center of each screw hole at the origin to the position of the horizontally placed tap axis is determined. The indexing plate reverses back to the origin, i.e., the original clamping position of the workpiece. The programmable controller sends B1 pulses, at which point the axis of the first screw hole coincides with the axis of the horizontal reverse tap, and the wire threading process can begin.

[0018] Working principle of screw fastening mechanism:

[0019] In existing technologies, dual-axis robots for screw fastening modules typically use an X-axis motor to drive a Z-axis manipulator to move laterally to directly above the screw feed port to pick up the screw. The Z-axis motor then starts, driving a servo electric screwdriver to move downwards towards the screw. As the screwdriver descends, its internal hexagonal head inserts into the screw's internal hexagonal hole, successfully picking up the screw. The Z-axis robot then carries the screwdriver upwards. Because the screwdriver bit is magnetic, the screw will not fall out during the Z-axis robot's upward movement after screw pickup, due to the magnetic force. Once the Z-axis reaches its destination, the X-axis motor starts, carrying the Z-axis robot back to its origin position, directly above the screw hole. The Z-axis robot then descends, and the screwdriver, carrying the screw, approaches the screw hole. The screwdriver slowly rotates, and the screw's threads engage with the threads in the hole, screwing the screw into the screw hole. When the screwdriver bit, carrying the screw, contacts the clamp, the resistance increases to the servo electric screwdriver's preset torque value, causing the screwdriver to stop rotating. The Z-axis manipulator then moves upwards, returning to its initial position.

[0020] Compared with the prior art, the screw assembly system for reprocessing circumferential screw holes of the present invention has the following advantages:

[0021] 1. The integrated design of the wire-penetrating function and screw fastening function allows the positioning actions of the two processes to be shared, improving the accuracy of screw fastening;

[0022] 2. By designing a chuck-type structure, it can adapt to the reprocessing of workpieces with circumferential screw holes of various diameters;

[0023] 3. This structure combines a diffuse reflection laser sensor with simple data processing, which can replace the currently mainstream machine vision. It has accurate positioning, low failure rate, extremely high work efficiency, and can also greatly save on the cost of supporting equipment. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a screw assembly system for reprocessing circumferential screw holes according to the present invention.

[0025] Figure 2 This is a schematic diagram illustrating the operating principle of a screw assembly system for reprocessing circumferential screw holes according to the present invention.

[0026] Figure 3 yes Figure 1 Status diagram of hole position detection in the middle part 2.

[0027] In the diagram: 1. Programmable Controller, 2. Circumferentially machined part, 3. Machining screw hole, 4. Frame, 5. Reprocessing mechanism, 6. N-frame, 7. Support arm, 8. Laser sensor probe, 9. Angle, 10. Screw fastening mechanism, 11. Fastening electric screwdriver, 12. Fixture, 13. Indexing plate, 14. Servo motor, 15. Guide groove, 16. Linear feeder, 17. Vibratory feeder, 18. Solenoid valve, 19. Screw, 501. Two-axis drive device, 502. Through-wire electric screwdriver, 5011. Longitudinal movement mechanism, 5012. Transverse movement mechanism. Detailed Implementation

[0028] The energy storage system for fitness equipment according to the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0029] Figure 1 This is a schematic diagram of a screw assembly system for reprocessing circumferential screw holes according to the present invention. Figure 2 This is a schematic diagram illustrating the operational principle of a screw assembly system for reprocessing circumferential screw holes according to the present invention. The screw assembly system for reprocessing circumferential screw holes includes a screw fastening mechanism 10 mounted above a frame 4, which is connected to a programmable controller 1 for operation control. A servo motor 14 drives an indexing plate 13, which is connected to a fixing fixture 12. A reprocessing mechanism 5 is mounted on one side of the indexing plate 13 on the frame 4. A laser sensor probe 8 is also mounted on the frame 4, located at the 45-degree bisector of the angle 9 formed by the reprocessing mechanism 5 and the screw fastening mechanism 10, and directly facing the fixing fixture 12. The laser sensor probe 8 is fixed by a support arm 7 hinged to an N-type frame 6. The fixing fixture 12 is a three-jaw chuck.

[0030] Servo motor

[0031] 14. Both the reprocessing mechanism 5 and the laser sensor probe 8 are connected to the programmable controller 1 for motion control. The reprocessing mechanism 5 includes a two-axis drive device 501 and a wire-penetrating electric screwdriver 502 connected to the two-axis drive device 501. The two-axis drive device 501 consists of a transverse movement mechanism 5012 and a longitudinal movement mechanism 5011. The wire-penetrating electric screwdriver 502 is located on the transverse movement mechanism 5012. The wire-penetrating electric screwdriver 502 is located on one side of the circumference of the fixed fixture 12 and intersects the axis of the fixed fixture 12 horizontally. The screw fastening mechanism 10 is located directly above the fixed fixture 12. A linear feeder 16 is also provided on one side of the screw fastening mechanism 10. The linear feeder 16 uses a vibratory feeder 17 to feed screws.

[0032] In use, first fix the circumferential workpiece 2, ensuring its inner diameter is horizontally clamped onto the fixing fixture 12. Then, activate the solenoid valve 18, and the three-jaw chuck of the fixing fixture 12 will externally support and fix the circumferential workpiece 2. Next, adjust the positioning position. The laser emitted by the laser sensor probe 8 will form a red spot with a size of approximately 1mm on the surface of the circumferential workpiece 2, ensuring that the laser irradiation point illuminates the non-threaded hole area on the outer wall of the workpiece. The moving support arm 7 adjusts the position of the laser sensor probe 8 so that the light spot formed by the laser sensor probe 8 on the workpiece surface is on the same plane as the center of the circumferentially distributed holes.

[0033] Start the indexing disk 13, such as Figure 3 The state diagram for hole position detection of part 2 shows that the laser emitted by the laser sensor probe 8 illuminates the edge of the hole from the wall of the machined screw hole 3. The laser sensor probe 8 sequentially records the total number of pulses as D1, D2, D3, D4, D5, and D6. The programmable controller 1 performs inverse trigonometric function calculations to determine the angle between the edge of the machined screw hole 3 and its center. This yields the number of pulses that the programmable controller 1 needs to send when the center of each screw hole in part 2 rotates from the origin to the axis of the horizontally placed through-wire electric screwdriver 502. The indexing plate 13 flips back to its initial position, i.e., the original clamping position of the workpiece. The programmable controller 1 sends B1 pulses. At this time, the axis of the first machined screw hole 3 coincides with the axis of the horizontal through-wire electric screwdriver 502. The machined screw hole 3 is now aligned with the cone of the through-wire electric screwdriver 502. The transverse movement mechanism 5012 moves forward, causing the through-wire electric screwdriver 502 to move closer to the machined screw hole 3. At the same time, the tap begins to rotate. As the transverse mechanism 5012 feeds axially, the wire-penetrating electric screwdriver 502 begins to penetrate the thread of the machined screw hole 3, scraping away residual plastic powder. When the tap of the wire-penetrating electric screwdriver 502 contacts the fixture and the resistance increases to the preset torque value of the transverse mechanism 5012, the wire-penetrating electric screwdriver 502 stops rotating forward. Then, the wire-penetrating electric screwdriver 502 begins to reverse and move backward, exiting the machined screw hole 3 and stopping 10mm from the outer surface of the workpiece 2. The programmable controller 1 continues to send pulse commands to the indexing plate. The indexing plate rotates, rotating the machined screw hole 3 corresponding to pulse number B2 to a horizontal position. After indexing, the transverse mechanism 5012 repeats the above steps, similarly completing the wire-penetrating process for all 6 holes.

[0034] Then, the screw fastening process begins. First, the fastening positioning is performed. At this point, the axis of the sixth machined screw hole 3 coincides with the horizontal direction. To proceed to the next screw fastening step, the axis of the first machined screw hole 3 must be aligned with the axis of the fastening electric screwdriver 11, i.e., the axis of the first machined screw hole 3 must be rotated to be directly above the workpiece 2. At this point, the angle between the axis of the first machined screw hole 3 and the axis of the sixth machined screw hole 3 is (D6-D1) / 1000, denoted as T. To determine the angle between the center of the first hole and the vertical direction, a judgment needs to be made: if T is greater than 90 degrees, the indexing plate needs to be rotated clockwise by T-90 degrees; if T is less than 90 degrees, the indexing plate needs to be rotated counterclockwise by 90-T degrees. This allows the axis of the first machined screw hole 3 to coincide with the axis of the locking electric screwdriver 11; the angle between the axis of the first machined screw hole 3 and the axis of the second machined screw hole 3 is [(D2-D1) / 1000], then the programmable controller 1 needs to send (D2-D1) pulses, which is counted as F1. The indexing plate 13 rotates clockwise to align the second machined screw hole 3 with the locking electric screwdriver 11; the angle between the axis of the third machined screw hole 3 and the axis of the second machined screw hole 3 is [(D3-D2) / 1000], the PLC needs to send (D3-D2) pulses, which is counted as F2, the indexing plate 13 rotates clockwise to align the third machined screw hole 3 with the axis of the locking electric screwdriver 11, and so on, for a total of F1-F5.

[0035] Next, the screw fastening process begins. The screw fastening mechanism 10 is activated, driving the fastening electric screwdriver 11 to move directly above the feed port of the linear feeder 16. The screw fastening mechanism 10 drives the fastening electric screwdriver 11 downwards, approaching the screw 19. As the fastening electric screwdriver 11 descends, the hexagonal screwdriver tip inserts into the hexagonal hole of the screw 19, successfully picking up the screw. It then carries the screw 19 back to its original position directly above the screw hole. The fastening electric screwdriver 11 continues downwards, bringing the screw 19 closer to the first machined screw hole 3. Then, the fastening electric screwdriver 11 slowly rotates, and the threads of the screw 19 engage with the threads in the machined screw hole 3, screwing the screw 19 into the machined screw hole 3. Until the fastening electric screwdriver 11, carrying the screw 19, contacts the fixture, the resistance increases to the preset torque value of the screw fastening mechanism 10, at which point the fastening electric screwdriver 11 stops rotating and returns to its initial position to perform the same screw assembly process.

[0036] This invention integrates wire-penetrating and screw-locking functions into a single structure, allowing both processes to share positioning actions and improving screw-locking accuracy. The chuck-type structure adapts to workpieces with various diameter circumferential screw holes. This structure combines a diffuse reflection laser sensor with simplified data processing, enabling it to replace currently mainstream machine vision systems. It offers accurate positioning, a low failure rate, high work efficiency, and significant cost savings.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the methods and techniques disclosed above without departing from the scope of the present invention to create equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A screw assembly system for reprocessing circumferential screw holes, comprising a screw fastening mechanism (10) mounted above a frame (4), the screw fastening mechanism (10) being connected to a programmable controller (1) for motion control, characterized in that: A servo motor (14) drives an indexing plate (13) which is fixedly mounted on the frame (4). The indexing plate (13) is connected to a fixing fixture (12). A reprocessing mechanism (5) is located on one side of the indexing plate (13) on the frame (4). A laser sensor probe (8) is also mounted on the frame (4). The laser sensor probe (8) is located between the angle (9) formed by the reprocessing mechanism (5) and the screw fastening mechanism (10) and faces the fixing fixture (12). The servo motor (14), the reprocessing mechanism (5), and the laser sensor probe (8) are all connected to... The programmable controller (1) controls the operation; the reprocessing mechanism (5) includes a two-axis drive device (501) and a wire-penetrating electric screwdriver (502) connected to the two-axis drive device (501); the screw fastening mechanism (10) includes an N-type frame (6), which is mounted on the frame (4); the laser sensor probe (8) is fixed by a support arm (7) hinged to the N-type frame (6); a linear feeder (16) is also provided on one side of the screw fastening mechanism (10), which uses a vibratory feeder (17) to feed screws.

2. The screw assembly system for reprocessing circumferential screw holes according to claim 1, characterized in that: The dual-axis drive device (501) consists of a transverse movement mechanism (5012) and a longitudinal movement mechanism (5011), and the through-wire electric screwdriver (502) is located on the transverse movement mechanism (5012).

3. A screw assembly system for reprocessing circumferential screw holes according to claim 2, characterized in that: The fixing clamp (12) is a chuck type. The wire-penetrating electric screwdriver (502) is located on one side of the circumference of the fixing clamp (12) and intersects the axis of the fixing clamp (12) horizontally. The screw fastening mechanism (10) is located directly above the fixing clamp (12). The laser sensor probe (8) is located at the 45-degree bisector of the angle (9) formed by the wire-penetrating electric screwdriver (502) and the screw fastening mechanism (10).

4. A screw assembly system for reprocessing circumferential screw holes according to claim 3, characterized in that: The fixing clamp (12) is a three-jaw chuck.

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