Safety detection and control method for automatic loading and unloading of workpieces by grinding machine

Abstract

This invention relates to a safety detection and control method for automatic workpiece loading and unloading on a grinding machine. The method involves detecting and controlling the automatic loading and unloading of workpieces on a grinding machine. A PLC receives position signals from motion position sensors of the grinding wheel head, worktable, headstock drive device, tailstock clamping device, workpiece support ejection device, center support stabilizing device, outer diameter measuring instrument, end face measuring instrument, workpiece thrust device, and protective door, as well as workpiece sensing sensor signals, to determine whether a robot arm can servic the grinding machine. This ensures that when the robot arm provides workpiece loading and unloading services to the grinding machine on an automated production line, there is no interference during the workpiece's vertical movement. Specifically, before the grinding machine issues a workpiece loading request, the robot arm and the gripped workpiece do not interfere with the internal components of the grinding machine; before the grinding machine issues a workpiece unloading request, the robot arm does not interfere with the internal mechanical components of the grinding machine except for contact with the workpiece; and during the upward movement of the gripped workpiece, the workpiece does not interfere with the internal components of the grinding machine.

Description

Technical Field

[0001] This invention relates to an electrical control method that provides absolute safety assurance for an automated production line, ensuring that the grinding machine is in an absolutely safe state before the robotic arm loads or unloads workpieces, and belongs to the technical field of automated intelligent factories. Background Technology

[0002] In actual processing, the mechanical motion components are controlled by hydraulic or pneumatic solenoid valves. However, when running the NC program, it is impossible to determine whether the mechanical components are truly in place. If they are not fully in place, the robot arm will collide with the workpiece during loading and unloading on the grinding machine, damaging the robot arm and the components inside the grinding machine.

[0003] If the coupling connecting the spindle of the servo motor and the ball screw is a spring-type coupling, and the servo motor is semi-closed-loop controlled, the coupling may slip during the operation of the servo motor. Due to long-term accumulation of deviation, the actual mechanical position deviates too much from the mechanical coordinate value displayed by the CNC. This causes the robot or the workpiece grasped by the robot to collide with the components inside the grinding machine during the process of loading and unloading workpieces on the grinding machine.

[0004] A contactless inductive sensor is installed inside the grinding machine to detect the presence of a workpiece. During NC programming, the program uses logical judgments to determine whether to load or unload a workpiece, and this signal is collected for this judgment. If the sensor malfunctions and fails to send a signal, or if metal shavings inside the grinding machine cover the sensor, causing it to send an incorrect signal, the grinding machine might not send a loading request signal to the robot even when there is no workpiece, or it might send a loading request signal even when there is a workpiece inside. This would affect the efficiency of the automated production line or damage mechanical components.

[0005] The main components installed on the workbench are the headstock rotating device and the tailstock clamping device. In actual processing, due to excessive hydraulic pressure, the headstock or tailstock may slide to both sides; or due to prolonged use, the fasteners of the headstock and tailstock mounting bases may loosen and slide to both sides. As a result, after processing, the position of the workpiece pulled out of the headstock tip will be deviated, and the workpiece may not be completely detached from the headstock tip after processing. When the robot arm picks up the workpiece later, it will damage the headstock tip and the workpiece.

[0006] After the grinding machine finishes processing, the hydraulically driven components pull the workpiece out from the headstock. However, during the pulling process, there are cases where the workpiece is pulled out too far or not in place. This can damage the mechanical components inside the grinding machine when the robot arm grabs the workpiece and affect the positioning of the workpiece during the subsequent loading process.

[0007] During the operation of a CNC program, the protective door of the grinding machine is normally closed. However, in practice, some operators, for convenience, remove the latch of the protective door and insert it into the electromagnetic lock hole, creating the illusion that the protective door is closed. This can result in serious injury. Summary of the Invention

[0008] This invention aims to enable automated production line robots to load and unload workpieces onto grinding machines, while avoiding potential interference between the robot and the grinding machine and preventing injury to operators. To prevent accidents, extremely high safety requirements are placed on safety assurance. This invention provides a safety detection and control method for the automatic loading and unloading of workpieces onto grinding machines. It utilizes a large number of non-contact sensing sensors to detect the position status of each moving part, and employs a control method that combines NC and PLC programs. The two programs are connected and communicate to exchange data, ensuring the safe and efficient operation of the automated production line.

[0009] The technical solution of this invention is: a safety detection and control method for automatic workpiece loading and unloading on a grinding machine, used to detect and control the automatic loading and unloading of workpieces on a grinding machine, including a robot arm, a grinding wheel head, a worktable, a headstock drive device, a tailstock clamping device, a workpiece carrier ejection device, a center rest stabilizing device, an outer diameter measuring instrument, an end face measuring instrument, a workpiece sensing sensor, a workpiece thrust device, and a protective door. A PLC receives data from the grinding wheel head, worktable, headstock drive device, tailstock clamping device, workpiece carrier ejection device, center rest stabilizing device, outer diameter measuring instrument, end face measuring instrument, workpiece thrust device, and protective door. The position sensor detects the position signal and the workpiece sensing sensor detects the signal to determine whether the robot can servic the grinding machine. This ensures that when the robot provides workpiece loading and unloading services to the grinding machine on the automated production line, there will be no interference in the up and down movement of the gripping workpiece. That is, before the grinding machine issues a workpiece loading service request, the robot and the gripped blank do not interfere with the internal components of the grinding machine; before the grinding machine issues a workpiece unloading request, the robot does not interfere with the mechanical components inside the grinding machine except when in contact with the workpiece, and does not interfere with the internal components of the grinding machine during the upward movement after gripping the workpiece.

[0010] Furthermore, the grinding wheel holder is driven forward and backward by a servo motor X-axis. After the grinding wheel dressing or processing is completed, the grinding wheel holder retracts to a designated safe position and sends a positioning signal to the PLC. The worktable is driven left and right by a servo motor Z-axis. After the grinding wheel dressing or processing is completed, the worktable moves to a designated safe position and sends a positioning signal to the PLC.

[0011] Furthermore, the headstock drive device is installed on the left side of the worktable. During the grinding of the workpiece, it drives the workpiece to rotate. To ensure that the workpiece does not interfere with other components during the unloading process after processing, the workpiece must stop at a pre-set safe angle position. The position is determined by a contactless sensor switch, and a confirmation signal is sent to the PLC. The tailstock clamping device is installed on the right side of the worktable. The workpiece is placed on the bracket, and the tailstock hydraulic cylinder drives the center to move towards the headstock. Finally, the headstock center and the tailstock center lift the workpiece. At this time, the workpiece can rotate freely under the drive of the headstock drive device. Before the robot arm loads and unloads the workpiece, the tailstock center must be retracted to the retracted position to leave space for the robot arm to grasp the workpiece. The retracted position of the tailstock center needs to be confirmed by the contactless sensor switch before a position signal is sent to the PLC for logic processing.

[0012] Furthermore, the workpiece bracket ejection device is installed on the worktable, one near the headstock and one near the tailstock. After the workpiece is processed, the tailstock tip retracts to the retracted position, and the bracket hydraulic cylinder drives to the right, thereby ejecting the workpiece from the headstock tip. This is one of the conditions for unloading the workpiece. When it is necessary to load the workpiece, in order to prevent the workpiece from interfering with the bracket, the bracket hydraulic cylinder drives to the left. The left and right positions need to be confirmed by a contactless sensor switch before a signal is sent to the PLC. The center frame stabilizing device is installed near the tailstock. During grinding, it pushes the workpiece forward. After grinding, the center frame clamping structure retracts and sends a signal to the PLC indicating that it has retracted to the correct position.

[0013] Furthermore, the outer diameter measuring instrument is installed on the worktable near the tailstock, directly facing the workpiece at the grinding position. After grinding is completed, the measuring instrument jaws retract, completely leaving the workpiece at a certain distance. The retraction position is confirmed by a non-contact sensor switch to confirm whether it is in position. If it is in position, the position signal is sent to the PLC.

[0014] Furthermore, the end face measuring instrument is mounted on the spindle housing of the grinding wheel head. Before grinding, it rests against the end face of the workpiece to measure the positional offset of the workpiece's axial position caused by the size of the center hole. This offset is then read and compensated in the Z-axis workpiece coordinate system, thereby compensating for the axial position deviation of the workpiece caused by the error in the workpiece's center hole. After the measurement is completed, the end face measuring instrument is lifted and sends a positioning signal to the PLC. Simultaneously, the end face measuring instrument is used to detect the slippage of the headstock drive device and the tailstock clamping device. The specific measurement steps are as follows:

[0015] (1) Inspect the slippage of the head frame drive device

[0016] Step 1: The worktable is pre-stopped at a safe position, that is, the end face measuring instrument will not interfere with the parts on the worktable when it moves forward. Then, the grinding wheel frame is driven forward by the X-axis of the servo motor, and the worktable is moved left and right by the Z-axis of the servo motor until the spherical end of the end face measuring instrument contacts the right vertical surface of the headstock drive device when the worktable moves.

[0017] Step 2: Drive the worktable to the right using the servo motor Z-axis so that the right vertical end face of the headstock contacts the end face measuring instrument until the end face measuring instrument sends a signal. At the same time, the Z-axis stops running and the mechanical coordinate value Z4 of the Z-axis is read. This value is regarded as the reference value.

[0018] Step 3: In the subsequent verification of whether the headstock has slipped, repeat the methods of steps 1 and 2, read the mechanical coordinate Z5 of the Z-axis, and then calculate the difference between the two Δ1 = |Z4-Z5|. When the absolute difference between the two Δ1 ≤ 0.1mm, it is within the required range.

[0019] (2) Sliding of the tailstock clamping device

[0020] Step 1: The worktable is pre-stopped in a safe position, that is, the end face measuring instrument will not interfere with the parts on the worktable when it moves forward. Then, the grinding wheel frame is driven forward by the X-axis of the servo motor, and the worktable is moved left and right by the Z-axis of the servo motor until the spherical end of the end face measuring instrument contacts the left vertical surface of the tailstock clamping device when the worktable moves.

[0021] Step 2: Drive the worktable to the left using the servo motor Z-axis, so that the left vertical end face of the tailstock contacts the end face measuring instrument until the end face measuring instrument sends a signal. At the same time, the Z-axis stops running and the mechanical coordinate value Z6 of the Z-axis is read. This value is regarded as the reference value.

[0022] Step 3: In the subsequent verification of whether the headstock has slipped, repeat the methods of steps 1 and 2, read the mechanical coordinate Z7 of the Z-axis, and then calculate the difference between the two Δ2=|Z6-Z7|. When the absolute difference between the two Δ2≤0.1mm, it is within the required range.

[0023] Furthermore, the workpiece sensing sensor is installed on a bracket on the side of the carriage. When the workpiece is placed on the carriage of the grinding machine, the workpiece sensing sensor will detect a signal and send it to the PLC for corresponding logic judgment. The workpiece thrust stop device is installed at a certain distance from the right end face of the workpiece when the tailstock tip lifts the workpiece. This distance ensures that when the carriage pulls out the workpiece and the left end face of the workpiece is completely away from the headstock tip, there is a certain distance, and at the same time, it ensures that the right end face of the workpiece is a certain distance from the tailstock tip when it retracts to the rearward position.

[0024] Furthermore, the grinding machine protective door is divided into a front protective door and a top protective door. The front protective door is operated by a manual switch. Before the grinding machine starts running, the protective door is closed and locked. It is closed and locked throughout the entire process of grinding and loading / unloading workpieces by the robot arm and cannot be opened manually. The closing and locking signal is sent to the PLC for processing. Before the robot arm loads / unloads workpieces for the grinding machine, the top protective door must be fully opened to the correct position and send the position signal to the PLC.

[0025] Furthermore, the method for controlling the robot arm to load and unload workpieces on the grinding machine is as follows: After powering on the grinding machine, check all accessories of the machine tool to ensure they are working properly. Then, turn on the hydraulic system and ensure there are no alarms. Close and lock the front protective door, then start the grinding wheel. Then, call up and run the system main program. By running the NC program, control the operation of the grinding wheel head, worktable, headstock drive device, tailstock clamping device, workpiece carrier ejection device, center rest stabilizing device, outer diameter measuring instrument, end face measuring instrument, workpiece sensing sensor, workpiece thrust device, and protective door inside the grinding machine, thereby meeting the conditions for the robot arm to load and unload workpieces on the grinding machine. The specific steps are as follows:

[0026] Step 1: Run the X-axis positioning program to stop the grinding wheel head in the safe retraction position and trigger the grinding wheel head safe retraction position detection sensor to send a signal;

[0027] Step 2: Run the Z-axis positioning program to stop the worktable at a position where the robot can load and unload workpieces, and trigger the worktable loading and unloading safety position detection sensor to send a signal.

[0028] Step 3: Run the headstock spindle motor on the headstock drive device, and then stop it. The stopping position should be such that the headstock stop sensor sends a signal.

[0029] Step 4: Execute the M command to lift the end face measuring instrument, so that the end face measuring instrument moves upward and the sensor on the end face measuring instrument sends a signal.

[0030] Step 5: Execute the M command to move the outer diameter measuring instrument backward, so that the outer diameter measuring instrument sends a signal from the rear sensor;

[0031] Step 6: Execute the M command to move the center frame backward, so that the center frame moves backward and the rear sensor sends a signal.

[0032] Step 7: Execute the M command to move the tailstock tip backward, causing the tailstock tip to move backward, so that the sensor at the rear of the tailstock tip will send a signal.

[0033] Step 8: Execute the M command to move the left and right brackets to the left, so that the left bracket sends a signal to the left sensor and the right bracket sends a signal to the left sensor at the same time.

[0034] Step 9: Execute the M command to open the protective top door, causing the sensor to send a signal when the protective top door is fully opened to the correct position;

[0035] After executing steps 1 to 9, the conditions for the robot to load and unload workpieces from the grinding machine are met.

[0036] Furthermore, if there is no workpiece inside the grinding machine, when the main program is executed, it jumps to the workpiece loading subroutine based on program logic. The grinding machine sends a workpiece loading request to the robot. After the workpiece is loaded, the program returns to the main program, which then jumps to the workpiece grinding subroutine based on logic. The tailstock center automatically lifts the workpiece and calls the grinding subroutine. After grinding is completed, the program returns to the main program again, and the main program jumps to the workpiece unloading subroutine based on program logic. The grinding machine sends a workpiece unloading request to the robot. The workpiece unloading subroutine executes step 1 above. In step 9, step 8 becomes: Execute the M command to move the left and right supports to the right, causing both supports to move to the right simultaneously, so that the left support sends a signal to the right sensor and the right support sends a signal to the right sensor at the same time; at this time, there is a workpiece in the grinding machine and a grinding completion signal will be sent after the previous grinding is completed. When the main program is executed, the grinding machine sends a workpiece unloading request to the robot arm through the program's logical judgment, and so on; when no processing is needed, select the "empty" button on the grinding machine's operation panel, and finally the workpiece is picked up. The program jumps to the end of the program through logical judgment, and the loop ends.

[0037] The beneficial effects of this invention are:

[0038] This invention enables the safe and efficient operation of grinding machines on automated production lines. Before or after processing, the grinding machine sends a workpiece loading / unloading request to the central control system on the automated production line. The automatic workpiece loading / unloading method utilizes positioning confirmation signals from relevant moving mechanical components within the grinding machine, along with safety interlocks between these components. This ensures no interference between moving parts before or after movement, and guarantees no interference when the robotic arm loads or unloads workpieces after each component has reached its designated position, thus guaranteeing the absolute safety of the operator, the grinding machine, and the robotic arm. This invention addresses the issue of ensuring all moving parts are in position, preventing false positioning of mechanical parts, and mitigating damage caused by sensor failure or slippage of the fixing device. Furthermore, it prevents forced operation by the operator. Attached Figure Description

[0039] Figure 1 This is a top view of the grinding machine in an embodiment of the present invention;

[0040] Figure 2 This is a diagram showing the safe positions of the grinding wheel frame and the worktable before loading and unloading workpieces in an embodiment of the present invention.

[0041] Figure 3This is a diagram showing the installation location of the sensor for detecting whether there is a workpiece inside the grinding machine in an embodiment of the present invention;

[0042] Figure 4 This is a diagram illustrating the anti-slip detection of the head frame driving device in an embodiment of the present invention.

[0043] Figure 5 This is a diagram showing the anti-slip detection of the tailstock clamping device in an embodiment of the present invention;

[0044] Figure 6 This is a diagram showing the installation position of the workpiece thrust device in an embodiment of the present invention;

[0045] Figure 7 This is a flowchart illustrating how a robotic arm loads and unloads workpieces onto a grinding machine, according to an embodiment of the present invention.

[0046] In the diagram: 1. Bed; 2. Worktable; 3. Headstock drive device; 4. Headstock stop sensor; 5. Left support on the left sensor; 6. Left support; 7. Left support on the right sensor; 8. Workpiece sensing sensor; 9. Worktable loading and unloading workpiece safety position detection sensor; 10. Center support in front sensor; 11. Center support in rear sensor; 12. Center support stabilizing device; 13. Outer diameter measuring instrument in front sensor; 14. Outer diameter measuring instrument in rear sensor; 15. Outer diameter measuring instrument; 16. Right support on the left sensor; 17. Right support on the right sensor; 18. Right support; 19. Tailstock clamping device; 20. Servo motor Z-axis; 21. End face measuring instrument; 22. Grinding wheel head retraction safety position detection sensor; 23. Servo motor X-axis; 24. Grinding wheel head; 25. Workpiece; 26. Workpiece thrust device sensing sensor; 27. Workpiece thrust device. Detailed Implementation

[0047] To make the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0048] The layout of various components of the grinding machine, such as Figure 1As shown, the components include a grinding wheel head 24, a worktable 2, a headstock drive device 3, a tailstock clamping device 19, left and right brackets 6, a right bracket 18, a center support stabilizing device 12, an outer diameter measuring instrument 15, and an end face measuring instrument 21. The movement of each mechanical component is controlled by hydraulic solenoid valves. During CNC program execution, it cannot be determined whether a mechanical component is truly in position. If it is not in position, the robot arm may collide with the workpiece 25 during loading and unloading, potentially damaging the robot arm and components within the grinding machine. Therefore, the position of each mechanical component is determined by sensors. When a mechanical component is issued by the CNC program, the program segment remains in a waiting state until the position sensor of that component detects its arrival. Only then does the CNC program execute the next program. This prevents interference in the pre-programmed sequence due to the mechanical component's incomplete movement in the previous program segment. The robot arm is only allowed to enter the grinding machine for service after all mechanical components within the grinding machine have reached their pre-set positions.

[0049] The safe positions of the grinding wheel holder and worktable before loading and unloading workpieces, such as... Figure 2 As shown, the grinding machine uses a servo motor X-axis 23 to control the forward and backward movement of the grinding wheel head, and a servo motor Z-axis 20 to control the left and right movement of the worktable 2. The CNC program controls the movement of the geometric axes using the workpiece coordinate system. The zero point of this coordinate system changes due to the establishment of the workpiece coordinate system and the need for grinding wheel dressing. Before loading and unloading the workpiece, the safe position of the robot arm is the actual position of the machine, which is the machine coordinate value of each axis. Therefore, it is necessary to convert the machine coordinates into workpiece coordinates.

[0050] When running a CNC program, a conversion needs to be performed within the program. The conversion formula is as follows:

[0051] X=X1+X2-X3 Z=Z1+(X1 / 2)*sinθ+Z2-Z3

[0052] Where X: workpiece coordinates on the X-axis; X1: mechanical coordinate value set when loading and unloading workpieces on the X-axis; X2: offset when establishing the X-axis workpiece coordinate system; X3: cumulative dressing amount in the X-axis direction during grinding wheel dressing; Z: workpiece coordinates on the Z-axis; Z1: mechanical coordinate value set when loading and unloading workpieces on the Z-axis; Z2: offset when establishing the Z-axis workpiece coordinate system; Z3: cumulative dressing amount in the Z-axis direction during grinding wheel dressing; θ: angle between the X-axis of the grinding wheel head and the perpendicular line of the Z-axis of the worktable.

[0053] Before loading and unloading workpieces, the position positioning program segment of the CNC program is run to stop the grinding wheel frame 24 and the worktable 2 at the preset mechanical coordinate values ​​X1 and Z1.

[0054] If the coupling connecting the spindle of the servo motor's geometric axis to the ball screw is a spring-type coupling, and the servo motor is under semi-closed-loop control, the coupling may slip during operation. Over time, this accumulates into a deviation, resulting in a significant discrepancy between the actual mechanical position and the CNC-displayed mechanical coordinates. This can cause the robot arm or the workpiece it grips to collide with internal components of the grinding machine during workpiece loading and unloading. To address this, a non-contact sensor is installed at the retraction position of the grinding wheel head and at the worktable loading / unloading position. These are the grinding wheel head retraction safety position detection sensor 22 and the worktable loading / unloading safety position detection sensor 9, respectively. Figure 2 As shown, before the robot arm is ready to load or unload workpieces onto the grinding machine, it should theoretically reach this position and check its signal status. If no signal is received, it is considered that the conditions for loading or unloading workpieces by the robot arm are not met. The grinding machine will not send a request instruction to the robot arm to load or unload workpieces, and the grinding machine's CNC system will trigger an alarm to prompt technicians to check.

[0055] Check if there is a workpiece inside the grinding machine, such as... Figure 3 As shown, a contactless inductive switch-type workpiece sensing sensor 8 is installed inside the grinding machine to detect whether there is a workpiece inside. During CNC program operation, the program uses logical judgment to determine whether to load or unload a workpiece, and this signal is collected for this judgment. If the sensor malfunctions and fails to send a signal, or if metal chips inside the grinding machine cover the sensor, causing it to send an incorrect signal, the result is that even if there is no workpiece inside, the grinding machine will not send a loading request signal to the robot, or it will send a loading request signal to the robot even if there is a workpiece inside. This affects the efficiency of the automated production line or damages mechanical components. Therefore, the program is modified to check that this sensor must send a signal after loading or grinding, and that it should not send a signal after unloading. If these checks are not performed, the CNC system issues a corresponding alarm, prompting technicians to check whether the sensor is functioning correctly.

[0056] Headframe drive device anti-slip detection, such as Figure 4 As shown, the headstock drive device 3, mounted on the left side of the worktable, slides to the left during actual machining due to excessive hydraulic pressure. This results in a deviation in the position of the workpiece after machining, preventing it from completely detaching from the headstock tip. Consequently, the headstock tip and workpiece are damaged during subsequent robotic arm gripping. To avoid this, the headstock end face is periodically inspected using an end face measuring instrument 21, and the Z-axis mechanical coordinate value is read at this time. The method is as follows:

[0057] Step 1: The worktable is pre-stopped at a safe position, that is, the end face measuring instrument 21 will not interfere with the parts on the worktable when it moves forward. Then, the grinding wheel frame is driven forward by the servo motor X axis 23, and the worktable is driven left and right by the servo motor Z axis until the spherical end of the end face measuring instrument 21 can contact the right vertical surface of the headstock drive device 3 when the worktable moves.

[0058] Step 2: Drive the worktable to the right by the servo motor Z-axis 20, so that the right vertical end face of the headstock contacts the end face measuring instrument 21 until the end face measuring instrument 21 sends a signal. At the same time, the Z-axis stops running and the mechanical coordinate value Z4 of the Z-axis is read. This value is regarded as the reference value.

[0059] Step 3: In the subsequent verification of whether the headstock has slipped, repeat the methods of steps 1 and 2, read the mechanical coordinate Z5 of the Z-axis, and then calculate the difference between the two Δ1=|Z4-Z5|. When the absolute difference between the two Δ1≤0.1mm, it is considered to be within the required range.

[0060] Tailstock clamping device anti-slip detection, such as... Figure 5 As shown, the tailstock clamping device 19 mounted on the right side of the worktable sometimes slides to the right due to excessive hydraulic pressure during actual machining. This results in the workpiece not being fully lifted before machining. To avoid this, the left vertical surface of the tailstock clamping device 19 is periodically checked using an end face measuring instrument 21, and the mechanical coordinate value of the Z-axis is read at this time. The method is as follows:

[0061] Step 1: The worktable is pre-stopped at a safe position, that is, the end face measuring instrument 21 will not interfere with the parts on the worktable when it moves forward. Then, the grinding wheel frame is driven forward by the servo motor X axis 23, and the worktable is driven left and right by the servo motor Z axis until the spherical end of the end face measuring instrument 21 can contact the left vertical surface of the tailstock clamping device 19 when the worktable moves.

[0062] Step 2: Drive the worktable 2 to the left by the servo motor Z-axis 20, so that the left vertical end face of the tailstock contacts the end face measuring instrument 21 until the end face measuring instrument 21 sends a signal. At the same time, the Z-axis stops running and reads the mechanical coordinate value Z6 of the Z-axis at this time. This value is regarded as the reference value.

[0063] Step 3: In the subsequent verification of whether the headstock has slipped, repeat the methods of steps 1 and 2, read the mechanical coordinate Z7 of the Z-axis, and then calculate the difference between the two Δ2=|Z6-Z7|. When the absolute difference between the two Δ2≤0.1mm, it is considered to be within the required range.

[0064] The installation location of the workpiece thrust device, such as... Figure 6As shown, after the grinding machine finishes processing, the hydraulically driven components pull the workpiece out from the headstock. However, during the pulling process, there is a possibility of over-pulling or under-pulling. This can damage the mechanical components inside the grinding machine when the robot arm grasps the workpiece, and also affect the positioning during loading in subsequent processes. The workpiece thrust device 27 installed on the worktable ensures that the workpiece is not over-pulled out. When the workpiece is under-pulled out, the workpiece thrust device 27 will trigger an alarm if the workpiece sensor 26 does not detect the workpiece. The grinding machine will not send a unloading request signal to the robot arm, thus ensuring that the mechanical components and workpiece are not damaged and that the next process can proceed normally.

[0065] During CNC program operation, the front safety door of the grinding machine is normally closed. However, in practice, operators may remove the latch of the front safety door for convenience and insert it into the electromagnetic lock hole, creating the illusion that the safety door is closed. This can lead to serious injury during machining and when the robot arm loads or unloads workpieces, as the safety door could be opened intentionally. To address this, a position sensor is installed on the safety door. When the CNC program is running, the safety door is closed, and the sensor does not send a signal. If the safety door is opened even slightly, the position sensor immediately sends a signal and alarm, the program stops running, and the grinding machine will not send any workpiece loading or unloading requests to the robot arm.

[0066] The process of a robotic arm loading and unloading workpieces on a grinding machine, such as... Figure 7 As shown, after powering on the grinding machine, check all accessories to ensure they are working properly. Then, turn on the hydraulic system and ensure there are no alarms. Close and lock the front safety door, and then start the grinding wheel. Next, bring up and run the main system program. By running the relevant M instructions in the NC program, control the operation of various mechanical components inside the grinding machine, thereby meeting the conditions for the robot arm to load and unload workpieces from the grinding machine.

[0067] The operating sequence of each mechanical component is as follows:

[0068] Step 1: Run the X-axis positioning program to stop the grinding wheel head 24 in the safe retraction position and make the grinding wheel head safe retraction position detection sensor 22 send a signal;

[0069] Step 2: Run the Z-axis positioning program to stop the worktable 2 at a position where the robot can load and unload workpieces, and make the worktable loading and unloading safety position detection sensor 9 send a signal.

[0070] Step 3: Run the headstock spindle motor on the headstock drive device 3, and then stop it. The stopping position should be such that the headstock stop sensor 4 sends a signal.

[0071] Step 4: Execute the M command to raise the end face measuring instrument 21, so that the end face measuring instrument 21 is raised and the sensor on the end face measuring instrument 21 sends a signal;

[0072] Step 5: Execute the M command to move the outer diameter measuring instrument 15 backward, so that the outer diameter measuring instrument 15 moves backward and the rear sensor 14 of the outer diameter measuring instrument sends a signal.

[0073] Step 6: Execute the M command to move the center frame backward, so that the outer diameter measuring instrument sends a signal at the rear sensor 11, while the center frame cannot send a signal at the front sensor 10.

[0074] Step 7: Execute the M command for the tailstock tip to move backward, causing the tailstock clamping device 19 to move backward, so that the sensor with the tailstock tip at the rear will send a signal.

[0075] Step 8: Execute the M command to move the left and right brackets to the left, so that the left bracket 6 and the right bracket 18 move to the left at the same time, so that the left bracket sends a signal at the left sensor 5 and the right bracket sends a signal at the left sensor 16 at the same time.

[0076] Step 9: Execute the M command to open the protective top door, causing the sensor to send a signal when the protective top door is fully opened to the correct position;

[0077] After executing the above steps, the conditions for the robot to load and unload workpieces from the grinding machine are met. If there is no workpiece in the grinding machine at this time, when the main program is executed, the main program can jump to the workpiece loading subroutine through logical judgment, and the grinding machine sends a workpiece loading request to the robot. After the workpiece is loaded, the program returns to the main program, and the main program jumps to the workpiece grinding subroutine through logical judgment. The tailstock center automatically lifts the workpiece and grinding can begin. After grinding is completed, the program returns to the main program again, and the main program can jump to the workpiece unloading subroutine through logical judgment, and the grinding machine sends a workpiece unloading request to the robot. The workpiece unloading subroutine executes steps 1 to 9 above, with step 8 becoming: executing the M command to move the left and right supports to the right, causing the left support 6 and the right support 18 to move to the right simultaneously, so that the left support sends a signal at the right sensor 7 and the right support sends a signal at the right sensor 17 simultaneously; at this time, there is a workpiece in the grinding machine, and a grinding completion signal will be sent after the previous grinding is completed. When the main program is executed, the grinding machine sends a workpiece unloading request to the robot through logical judgment, and so on. When no processing is required, the "Evacuate" button can be selected on the operation panel of the grinder. Finally, the workpiece is picked up, and the program jumps to the end of the program through logical judgment, and the loop ends.

[0078] If an M-instruction remains stationary during the program loop, it indicates that the mechanical component controlling that action has not reached its intended position. In this case, the operator needs to check the corresponding indicator lights for confirmation. If an M-instruction from the grinding machine requesting the robot to load or unload a workpiece remains stationary, it is necessary to check whether all conditions for the robot to serve the grinding machine are met, as described in claim 9.

Claims

1. A safety detection and control method for automatic workpiece loading and unloading on a grinding machine, used for detecting and controlling automatic workpiece loading and unloading on a grinding machine, characterized in that: The system includes a robotic arm, grinding wheel head, worktable, headstock drive mechanism, tailstock clamping mechanism, workpiece ejector, center rest stabilizing device, outer diameter measuring instrument, end face measuring instrument, workpiece sensing sensor, workpiece thrust stop, and protective door. The PLC receives position signals from the motion position sensors of the grinding wheel head, worktable, headstock drive mechanism, tailstock clamping mechanism, workpiece ejector, center rest stabilizing device, outer diameter measuring instrument, end face measuring instrument, workpiece thrust stop, and protective door, as well as detection signals from the workpiece sensing sensor, to determine whether the robotic arm can servic the grinding machine. This ensures that when the robotic arm provides workpiece loading and unloading services to the grinding machine on an automated production line, it can effectively grasp and load workpieces. The unloading motion will not interfere with anything; that is, before the grinding machine issues a workpiece loading request, the robot arm and the gripped blank will not interfere with the internal components of the grinding machine. Before the grinding machine issues a workpiece unloading request, the robot arm will not interfere with the internal mechanical components of the grinding machine except for contact with the workpiece, and will not interfere with the internal components of the grinding machine during its upward movement after gripping the workpiece. The grinding wheel head is driven forward and backward by a servo motor on the X-axis. After the grinding wheel dressing or machining is completed, the grinding wheel head retracts to a designated safe position and sends a positioning signal to the PLC. The worktable is driven left and right by a servo motor on the Z-axis. After the grinding wheel dressing or machining is completed, the worktable moves to a designated position. The headstock drive device is installed on the left side of the worktable. During grinding, it rotates the workpiece. To ensure the workpiece doesn't interfere with other components during unloading, it must stop at a pre-set safe angle position, determined by a contactless sensor switch, which sends a confirmation signal to the PLC. The tailstock clamping device is installed on the right side of the worktable. The workpiece is placed on the support, and the tailstock hydraulic cylinder drives the center point towards the headstock. Finally, the headstock and tailstock centers lift the workpiece, allowing it to rotate freely under the drive of the headstock drive device. Before the robotic arm can load or unload workpieces, it must be moved to the retracted position to allow space for the robotic arm to grasp the workpiece. The tailstock tip must be confirmed to be in the retracted position by a contactless sensor switch before a signal is sent to the PLC for logic processing. The workpiece carrier ejection device is installed on the worktable, one near the headstock and one near the tailstock. After workpiece processing is complete, the tailstock tip retracts to the retracted position, and the carrier hydraulic cylinder drives to the right, thus ejecting the workpiece from the headstock tip. This is one of the conditions for workpiece unloading. When workpiece loading is required, to prevent interference between the workpiece and the carrier, the carrier hydraulic cylinder drives to the left. The left and right positions must be confirmed by a contactless sensor switch before a signal is sent to the PLC. The center frame stabilizing device is installed near the tailstock. During grinding, it pushes the workpiece forward. After grinding, the center frame stabilizing structure retracts and sends a signal to the PLC indicating that it has reached the correct position.The outer diameter measuring instrument is installed on the worktable near the tailstock, directly facing the workpiece at the grinding position. After grinding, the measuring instrument jaws retract completely away from the workpiece, maintaining a certain distance. The retraction position is confirmed by a contactless sensor switch. If it is in position, a positioning signal is sent to the PLC. The end face measuring instrument is installed on the grinding wheel spindle housing and rests against the end face of the workpiece before grinding. It measures the positional offset of the workpiece due to the size of the center hole. This offset is then read and compensated in the Z-axis workpiece coordinate system to compensate for the axial position deviation caused by the error of the workpiece center hole. After measurement, the end face measuring instrument is lifted and a positioning signal is sent to the PLC. Simultaneously, the end face measuring instrument is used to detect the slippage of the headstock drive device and the tailstock clamping device. The specific measurement steps are as follows: (1) Detect the slippage of the head frame drive device Step 1: The worktable is pre-stopped at a safe position, that is, the end face measuring instrument will not interfere with the parts on the worktable when it moves forward. Then, the grinding wheel frame is driven forward by the X-axis of the servo motor, and the worktable is moved left and right by the Z-axis of the servo motor until the spherical end of the end face measuring instrument contacts the right vertical surface of the headstock drive device when the worktable moves. Step 2: Drive the worktable to the right using the servo motor Z-axis so that the right vertical end face of the headstock contacts the end face measuring instrument until the end face measuring instrument sends a signal. At the same time, the Z-axis stops running and the mechanical coordinate value Z4 of the Z-axis is read. This value is regarded as the reference value. Step 3: To verify whether the headstock has slipped, repeat steps 1 and 2, read the Z-axis mechanical coordinate Z5, and then calculate the difference between the two. 1 = |Z4 - Z5|, when the absolute difference between the two is... If 1 ≤ 0.1 mm, then it meets the requirements. (2) Sliding of the tailstock clamping device Step 1: The worktable is pre-stopped in a safe position, that is, the end face measuring instrument will not interfere with the parts on the worktable when it moves forward. Then, the grinding wheel frame is driven forward by the X-axis of the servo motor, and the worktable is moved left and right by the Z-axis of the servo motor until the spherical end of the end face measuring instrument contacts the left vertical surface of the tailstock clamping device when the worktable moves. Step 2: Drive the worktable to the left using the servo motor Z-axis, so that the left vertical end face of the tailstock contacts the end face measuring instrument until the end face measuring instrument sends a signal. At the same time, the Z-axis stops running and the mechanical coordinate value Z6 of the Z-axis is read. This value is regarded as the reference value. Step 3: To verify whether the tailstock has slipped, repeat steps 1 and 2, read the Z-axis mechanical coordinate Z7, and then calculate the difference between the two. 2 = |Z6 - Z7|, when the absolute difference between the two is... If 2 ≤ 0.1 mm, then it meets the requirements. The grinding machine has two protective doors: a front protective door and a top protective door. The front protective door is operated manually. It is closed and locked before the grinding machine starts running, and remains closed and locked throughout the grinding process and the robot's loading and unloading of workpieces. It cannot be opened manually, and the closing and locking signal is sent to the PLC for processing. The top protective door must be fully opened before the robot loads or unloads workpieces from the grinding machine, and a signal indicating that it is in position is sent to the PLC. The method for controlling the robotic arm to load and unload workpieces on the grinding machine is as follows: After powering on the grinding machine, check all accessories to ensure they are working properly. Then, turn on the hydraulic system and ensure there are no alarms. Close and lock the front safety door. Then, start the grinding wheel, and then call up and run the system main program. By running the NC program, control the operation of the grinding wheel head, worktable, headstock drive device, tailstock clamping device, workpiece carrier ejection device, center rest stabilizing device, outer diameter measuring instrument, end face measuring instrument, workpiece sensing sensor, workpiece thrust device, and safety door inside the grinding machine. This satisfies the conditions for the robotic arm to load and unload workpieces on the grinding machine. The specific steps are as follows: Step 1: Run the X-axis positioning program to stop the grinding wheel head in the safe retraction position and trigger the grinding wheel head safe retraction position detection sensor to send a signal; Step 2: Run the Z-axis positioning program to stop the worktable at a position where the robot can load and unload workpieces, and trigger the worktable loading and unloading safety position detection sensor to send a signal. Step 3: Run the headstock spindle motor on the headstock drive device, and then stop it. The stopping position should be such that the headstock stop sensor sends a signal. Step 4: Execute the M command to lift the end face measuring instrument, so that the end face measuring instrument moves upward and the sensor on the end face measuring instrument sends a signal. Step 5: Execute the M command to move the outer diameter measuring instrument backward, so that the outer diameter measuring instrument sends a signal from the rear sensor; Step 6: Execute the M command to move the center frame backward, so that the center frame moves backward and the rear sensor sends a signal. Step 7: Execute the M command to move the tailstock tip backward, causing the tailstock tip to move backward, so that the sensor at the rear of the tailstock tip will send a signal. Step 8: Execute the M command to move the left and right brackets to the left, so that the left bracket sends a signal to the left sensor and the right bracket sends a signal to the left sensor at the same time. Step 9: Execute the M command to open the protective top door, causing the sensor to send a signal when the protective top door is fully opened to the correct position; After executing steps 1 to 9, the conditions for the robot to load and unload workpieces from the grinding machine are met.

2. The method for safety detection and control of automatic workpiece loading and unloading on a grinding machine according to claim 1, characterized in that: The workpiece sensing sensor is installed on a bracket on the side of the carriage. When the workpiece is placed on the carriage of the grinding machine, the workpiece sensing sensor will detect a signal and send it to the PLC for corresponding logic judgment. The workpiece thrust stop device is installed at a certain distance from the right end face of the workpiece when the tailstock tip lifts the workpiece. This distance ensures that when the carriage pulls out the workpiece and the left end face of the workpiece is completely away from the headstock tip, there is a certain distance, and at the same time, it ensures that the right end face of the workpiece is a certain distance from the tailstock tip when it is retracted to the rear position.

3. The method for safety detection and control of automatic workpiece loading and unloading on a grinding machine according to claim 1, characterized in that: If there is no workpiece in the grinding machine, when the main program is executed, the main program jumps to the workpiece loading subroutine through the program's logical judgment. The grinding machine sends a workpiece loading request to the robot. After the workpiece is loaded, the program returns to the main program. The main program jumps to the workpiece grinding subroutine through logical judgment. The tailstock center automatically lifts the workpiece and calls the grinding subroutine. After grinding is complete, the program returns to the main program. Based on the program's logic, the main program jumps to the workpiece unloading subroutine, and the grinding machine sends a workpiece unloading request to the robot. The workpiece unloading subroutine executes steps 1 to 9 above, with step 8 becoming: executing the M command to move the left and right supports to the right, causing both supports to move to the right simultaneously, so that the left support sends a signal to the right sensor and the right support sends a signal to the right sensor at the same time. At this time, there is a workpiece in the grinding machine, and a grinding completion signal will be sent after the previous grinding is completed. When the main program is executed, based on the program's logic, the grinding machine sends a workpiece unloading request to the robot, and so on. When no processing is needed, the "empty" button is selected on the grinding machine's operation panel, and finally the workpiece is picked up. The program then jumps to the end of the program based on the logic, and the loop ends.

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