Electronic cam automatic calibration method suitable for mechanical press

Abstract

The invention discloses an electronic cam automatic calibration method suitable for a mechanical press. A mechanical press control system PLC is used for recording the angle of the press when signals of a mechanical cam switch of the press change every time, the angle recorded during operation every time is permanently stored in the PLC, and when an electronic cam system is shut down abnormally and faults are repaired, the press operates for one circle in a micro-motion mode, and the angle is not changed. The angle of the press machine can be calibrated through the historical triggering angle value of the mechanical cam recorded in the PLC when the switching signal of the mechanical cam at the current stroke frequency changes, and therefore automatic calibration of the electronic cam of the mechanical press machine is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of control of position measurement of mechanical presses, and in particular to an automatic calibration method of an electronic cam suitable for mechanical presses. Background Art

[0002] Mechanical presses are high-end products in the sheet metal stamping industry. Due to their high efficiency and reliability, they are particularly well-suited for automated assembly lines, producing high-strength, lightweight parts. Currently, mechanical presses are most widely used in high-speed automotive manufacturing, where production lines demand extremely high efficiency and reliability, with lower mean time between failures (MTBF) and mean time to repair (MTTR) than in other metal forming industries.

[0003] The electronic cam of a mechanical press typically refers to a rotary encoder that measures the press's stroke angle. It's primarily used to calculate the current angle or position of the press's slide. Without this data, the press will be unable to start and stop according to the required input angles. To ensure the authenticity and reliability of the electronic cam data, a set of mechanical cams is often used to verify and validate it.

[0004] The mechanical cam is a set of independently installed cam switches. When the press runs to a pre-set angle, the cam switch will trigger a signal change.

[0005] Because the mechanical cam is fixed, once the cam is installed and debugged, a fixed relationship exists between the cam switch signal changes and the press angle. Therefore, the press angle corresponding to the cam switch signal changes can be recorded during each press operation. Under normal circumstances, the angle recorded during each operation has minimal error and is consistent with the angle pre-set upon debugging.

[0006] Currently, when a mechanical press's electronic cam shuts down due to a broken shaft, anomaly, malfunction, or damage, manual recalibration of the cam is required after the malfunction is repaired. Recalibrating the press's bottom dead center using a dial indicator is a common practice, and the process takes approximately 30 to 60 minutes.

[0007] Therefore, it is possible to consider using a fixed correspondence between the signal change of the mechanical cam switch and the angle of the press to realize automatic calibration of the electronic cam, thereby replacing the traditional fault recovery method of using a dial indicator to recalibrate the bottom dead point of the press, thereby significantly reducing equipment downtime. Summary of the Invention

[0008] In order to solve the deficiencies of the above technical solutions, the object of the present invention is to provide an automatic calibration method for an electronic cam suitable for a mechanical press.

[0009] The purpose of the present invention is achieved through the following technical solutions.

[0010] An automatic calibration method for an electronic cam of a mechanical press, comprising the following steps:

[0011] Step 1: Debug the angle of the mechanical cam of the mechanical press, including the angle triggered by the top dead center signal and the angle triggered by the bottom dead center signal;

[0012] Step 2: The mechanical press is running to determine whether there is a fault in the mechanical press:

[0013] If there is a fault, the fault will be output and the machine will be shut down;

[0014] If there is no fault, when the mechanical press rotates forward, the mechanical cam angle is triggered when the output signal of the mechanical cam switch changes. The mechanical press control system reads and records the signal of the mechanical cam angle collected by the electronic cam, and verifies the data validity of the mechanical cam angle when the mechanical press is operating normally. The valid mechanical cam angle is stored in the retentive storage area of ​​the control system to obtain the storage array history data. The invalid mechanical cam angle is output as a fault and shuts down. The output signal of the mechanical cam switch changes to the falling edge of the top dead center signal and the falling edge of the bottom dead center signal.

[0015] Step 3, the mechanical press is inching. If the electronic cam fails, the control system reads the bottom dead point signal value or the top dead point signal value in the historical data of the storage array. When the mechanical press rotates forward, the bottom dead point or the top dead point of the currently running mechanical cam angle is determined according to the read signal, and the electronic cam automatic calibration program command in the control system is executed. The press is manually controlled to inching back to the top dead point or the bottom dead point, and it is determined whether the top dead point signal or the bottom dead point signal of the mechanical cam angle collected by the electronic cam after the automatic calibration program command is normal. If not, the machine is shut down for inspection.

[0016] In the above technical solution, in step 1, when the trigger angle of the bottom dead point is 175°-185°, the bottom dead point signal is triggered, and when the trigger angle of the top dead point is 355°-5°, the top dead point signal is triggered.

[0017] In the above technical solution, in step 2, the electronic cam is a rotation angle absolute encoder installed on the crossbeam of the mechanical press.

[0018] In the above technical solution, in step 2, the bottom dead point of the currently running mechanical cam angle is determined based on the median or average of the read bottom dead point signal value, or the top dead point of the currently running mechanical cam angle is determined based on the median or average of the read top dead point signal value.

[0019] In the above technical solution, in step 2, the step of verifying the data validity is: calculating the median M and the absolute median difference MAD of the data currently stored in the retentive storage area.

[0020] Based on the median and absolute median difference, the standard deviation S = 1.4826 × MAD was estimated, and the threshold LU = M ± 3 × S was set;

[0021] According to the set threshold, if the new data stored in the retentive storage area is within the threshold range, the current data is overwritten; otherwise, the new data is discarded and an alarm is issued.

[0022] In the above technical solution, the control system is a PLC or controller, and the PLC or controller has a system cycle scanning period of no more than 10ms. The advantages and beneficial effects of the present invention are:

[0023] 1. The present invention can effectively reduce the time required to repair and recalibrate a mechanical press electronic cam system failure, realize automatic identification and calibration of the electronic cam, and significantly improve the automation and intelligence of the mechanical press control system.

[0024] 2. The present invention uses the PLC of the mechanical press control system to record the angle of the press each time the signal of the mechanical cam switch of the press changes, and permanently stores the angle recorded during each operation in the PLC. When the electronic cam system stops abnormally and the fault is repaired, the press runs one circle in the micro-motion mode, and the historical value of the mechanical cam trigger angle recorded in the PLC can be used to calibrate the angle of the press when the mechanical cam switch signal changes in the current stroke, thereby realizing automatic calibration of the electronic cam of the mechanical press. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic flow chart of step 2 of the present invention;

[0026] Figure 2 Schematic diagram of the process of step 3 of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further described below with reference to specific embodiments.

[0028] The following embodiment is an automatic calibration control method of an electronic cam proposed based on a mechanical press control system equipped with a mechanical cam and an electronic cam, and is applicable to existing single mechanical presses or automated press lines composed of mechanical presses in series.

[0029] An automatic calibration method for an electronic cam of a mechanical press, comprising the following steps:

[0030] Step 1, mechanical press ( Figure 1 and Figure 2 The angle of the mechanical cam of the press (referred to as the press in Chinese) is debugged. The debugged angles include the angle of the top dead point signal triggering and the angle of the bottom dead point signal triggering. When the trigger angle of the bottom dead point is 175°-185°, the bottom dead point signal is triggered. When the trigger angle of the top dead point is 355°-5°, the top dead point signal is triggered.

[0031] like Figure 1 As shown, in step 2, the mechanical press is running to determine whether there is a fault in the mechanical press:

[0032] If there is a fault, the fault will be output and the machine will be shut down;

[0033] If there are no faults, when the mechanical press rotates forward, the mechanical cam angle is triggered when the output signal of the mechanical cam switch changes. The mechanical press control system reads and records the mechanical cam angle signal collected by the electronic cam, verifies the data validity of the mechanical cam angle during normal operation of the mechanical press, stores the valid mechanical cam angle in the control system's retentive storage area, and obtains the storage array historical data. For invalid mechanical cam angles, a fault is output and the machine is shut down. In this embodiment, the output signal of the mechanical cam switch changes to the falling edge of the top dead center signal (when the slide of the mechanical press reaches the top dead center, the signal output by the mechanical cam switch changes from a high level to a low level) and the falling edge of the bottom dead center signal (when the slide of the mechanical press reaches the bottom dead center, the signal output by the mechanical cam switch changes from a high level to a low level).

[0034] like Figure 2As shown, step 3, the mechanical press is inching operation. If the electronic cam fails, the control system reads the bottom dead point signal value (or top dead point signal value) in the storage array history data. When the mechanical press rotates forward, the bottom dead point (or top dead point) of the currently running mechanical cam angle is determined according to the read signal, and the electronic cam automatic calibration program command in the control system is manually activated. The press is manually controlled to inching back to the top dead point (or bottom dead point). It is judged whether the mechanical cam angle triggered by the top dead point signal collected by the electronic cam is normal (or whether the mechanical cam angle triggered by the top dead point signal collected by the electronic cam is normal). If it is abnormal, the machine is shut down for inspection. Specifically, in this embodiment, the top dead point signal trigger angle historically stored in the retentive storage area is used to judge whether the mechanical cam angle triggered by the top dead point signal collected by the electronic cam after the automatic calibration program command is normal. When the error between the two angles does not exceed 1°, it is judged to be normal.

[0035] Furthermore, the electronic cam is a rotation angle absolute encoder installed on the crossbeam of the mechanical press.

[0036] Furthermore, in step 2, the bottom dead point of the currently running mechanical cam angle is determined based on the median or average of the read bottom dead point signal values, or the top dead point of the currently running mechanical cam angle is determined based on the median or average of the read top dead point signal values.

[0037] Furthermore, the control system is a PLC or a controller, and the PLC or the controller has a system cycle scanning period of no more than 10ms.

[0038] Furthermore, the retentive storage area is a power-off retentive storage area.

[0039] Furthermore, the steps of verifying the validity of the data are as follows:

[0040] Calculate the median M and absolute median difference MAD of the data currently stored in the retentive storage area;

[0041] Based on the median and absolute median difference, the standard deviation S = 1.4826 × MAD was estimated, and the threshold LU = M ± 3 × S was set;

[0042] According to the set threshold, if the new data stored in the retentive storage area is within the threshold range, the current data is overwritten; otherwise, the new data is discarded and an alarm is issued.

[0043] Based on the automatic calibration method of the electronic cam of this embodiment, the calibration of the electronic cam can be completed within 5 minutes.

[0044] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A method for automatic calibration of an electronic cam for a mechanical press, characterized in that: The following steps are involved: Step 1: Debug the angle of the mechanical cam of the mechanical press, including the angle triggered by the top dead center signal and the angle triggered by the bottom dead center signal; Step 2: The mechanical press is running to determine whether there is a fault in the mechanical press: If there is a fault, the fault will be output and the machine will be shut down; If there is no fault, when the mechanical press rotates forward, the mechanical cam angle is triggered when the output signal of the mechanical cam switch changes. The mechanical press control system reads and records the signal of the mechanical cam angle collected by the electronic cam, and verifies the data validity of the mechanical cam angle when the mechanical press is operating normally. The valid mechanical cam angle is stored in the retentive storage area of ​​the control system to obtain the storage array history data. The invalid mechanical cam angle is output as a fault and shuts down. The output signal of the mechanical cam switch changes to the falling edge of the top dead center signal and the falling edge of the bottom dead center signal. Step 3, the mechanical press is inching. If the electronic cam fails, the control system reads the bottom dead point signal value or the top dead point signal value in the historical data of the storage array. When the mechanical press rotates forward, the bottom dead point or the top dead point of the currently running mechanical cam angle is determined according to the read signal, and the electronic cam automatic calibration program command in the control system is executed. The press is manually controlled to inching back to the top dead point or the bottom dead point, and it is determined whether the top dead point signal or the bottom dead point signal of the mechanical cam angle collected by the electronic cam after the automatic calibration program command is normal. If not, the machine is shut down for inspection.

2. The electronic cam automatic calibration method according to claim 1, characterized in that: In step 1, when the trigger angle of the bottom dead point is 175°-185°, the bottom dead point signal is triggered, and when the trigger angle of the top dead point is 355°-5°, the top dead point signal is triggered.

3. The electronic cam automatic calibration method according to claim 1, characterized in that: In step 2, the electronic cam is a rotation angle absolute encoder installed on the crossbeam of the mechanical press.

4. The electronic cam automatic calibration method according to claim 1, characterized in that: In step 2, the bottom dead point of the currently running mechanical cam angle is determined based on the median or average of the read bottom dead point signal values, or the top dead point of the currently running mechanical cam angle is determined based on the median or average of the read top dead point signal values.

5. The electronic cam automatic calibration method according to claim 1, characterized in that: In step 2, the step of verifying the data validity is as follows: calculating the median M and the median absolute difference MAD of the data currently stored in the retentive storage area; Based on the median and absolute median difference, the standard deviation S = 1.4826 × MAD was estimated, and the threshold LU = M ± 3 × S was set; According to the set threshold, if the new data stored in the retentive storage area is within the threshold range, the current data is overwritten; otherwise, the new data is discarded and an alarm is issued.

6. The electronic cam automatic calibration method according to claim 1, characterized in that: The control system is a PLC or a controller, and the PLC or the controller has a system cycle scanning period not higher than 10ms.

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