Press Machine Pressure Detection Method

Abstract

The present invention discloses a method for detecting the pressure of a punching machine, which includes: A) establishing the corresponding relationship between the detected pressure of a hydraulic sensor and the punching machine pressure when the slider moves downward, and storing it in a programmable controller; B) setting the angle at which the crankshaft rotates to the bottom dead center as the reference angle, and setting the crankshaft rotation angle range within a certain range before and after the reference angle as the measurement range; within the measurement range, every time the angle encoder detects that the crankshaft rotates by one unit angle, the programmable controller immediately collects a pressure value through the hydraulic sensor and stores it; C) the programmable controller converts the pressure values collected by the hydraulic sensor each time within the measurement range into the punching machine pressure according to the corresponding relationship between the detected pressure of the hydraulic sensor and the punching machine pressure when the slider moves downward, and takes the maximum value among them as the punching machine working pressure for the current downward movement of the slider; the present invention can detect the current punching machine pressure in real time and accurately, and has good repeatability and reliability.

Description

Technical Field

[0001] The present invention relates to a method for detecting the pressure of a punching press, especially a method for detecting the pressure of a crankshaft-slider punching press. Background Art

[0002] The detection and display of the punching press pressure have always been key indicators in the stamping field. It is related to the qualification rate of stamped workpieces, the maintenance cycle and service life of the punching press, and is an indispensable sensing and monitoring equipment for 21st-century numerically controlled intelligent punching presses.

[0003] Currently, the relatively mature method for detecting the punching press pressure is to use an electronic stress gauge, which is attached to the body of the punching press to detect the stress deformation of the metal material and obtain the pressure through conversion. However, this method will have an increasing error with the fatigue deformation of the material, and it needs to be calibrated frequently to ensure accuracy, resulting in poor detection accuracy and reliability. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for detecting the pressure of a punching press in view of the above deficiencies of the prior art. It can detect the current punching press pressure in real time and accurately, and has good repeatability and reliability.

[0005] To achieve the above purpose, the punching press pressure detection system used in the present invention includes a crankshaft, a ball screw connected to the crankshaft, a slider, a hydraulic cylinder and a piston arranged in the slider. The ball head is connected to the slider and cooperates with the piston. The hydraulic cylinder is connected to a hydraulic pump through an oil pipe, and the oil pipe is provided with a hydraulic sensor for detecting the pressure inside the pipe. The crankshaft is provided with an angle encoder for detecting its rotation angle. One end of the crankshaft is connected with a pulley mechanism, and the angle encoder is arranged on the driven wheel of the pulley mechanism; both the hydraulic sensor and the angle encoder are connected to a programmable controller, and the programmable controller is connected to a touch screen.

[0006] As a preference of the punching press pressure detection system, the oil pipe is provided with a three-way joint, and the hydraulic sensor is arranged on the three-way joint; it is convenient for the installation of the hydraulic sensor;

[0007] The punching press pressure detection method of the present invention for the above system is characterized by including the following steps: A) Establish the corresponding relationship between the detected pressure of the hydraulic sensor and the punching press pressure when the slider moves downward, and store it in the programmable controller; B) Set the angle when the crankshaft rotates to the bottom dead center as the reference angle, and set the crankshaft rotation angle range within a certain range before and after the reference angle as the measurement range; within the measurement range, every time the angle encoder detects that the crankshaft rotates one unit angle, the programmable controller immediately collects a pressure value through the hydraulic sensor and stores it; C) The programmable controller converts the pressure values collected by the hydraulic sensor each time within the measurement range into the punching press pressure according to the corresponding relationship between the detected pressure of the hydraulic sensor and the punching press pressure when the slider moves downward, and takes the maximum value among them as the punching press working pressure when the slider moves downward this time;

[0008] The present invention utilizes the change in the oil pressure within the hydraulic cylinder caused by the punching press pressure each time the slider descends and punches. By means of an angle encoder in cooperation with a hydraulic sensor, the oil pressure is detected in sections and multiple times in the vicinity of the bottom dead center of the crankshaft rotation, avoiding the problem of large detection errors caused by the fast descending speed of the slider, short punching time, large pressure change, and the inability of the programmable logic controller's operation speed to meet the requirements of continuous detection and operation. It can detect the current punching press pressure in real time and accurately, and has good repeatability. Compared with electronic stress gauges, hydraulic detection has no fatigue deformation error and good reliability;

[0009] A preferred embodiment of the method of the present invention is that in step A), the corresponding relationship between the detected pressure of the hydraulic sensor and the punching press pressure when the slider descends is established by setting a tonnage meter on the punching press; that is: the tonnage meter is placed on the workbench below the slider. The slider descends multiple times, and the descending depths of the slider each time have different degrees of coincidence with the tonnage meter (simulating the role of the workpiece) in the longitudinal height. Therefore, the working pressures each time are different. The tonnage meter can display the working pressures each time. By cooperating with the hydraulic sensor, the accurate corresponding relationship between the detected pressure and the punching press pressure when the slider descends can be obtained, and this corresponding relationship is converted into a relationship curve and stored in the programmable logic controller;

[0010] A preferred embodiment of the method of the present invention is that in step B), the crankshaft rotation angle range within 15° before the reference angle and 5° after the reference angle is set as the measurement range; the unit angle is set as 1°; a reasonable measurement range can cover the maximum pressure rotation angles of various working conditions, and a smaller unit angle can improve the detection accuracy;

[0011] A preferred embodiment of the method of the present invention is that in step C), the punching press working pressure of the current slider descent is displayed through a touch screen; the current punching press pressure can be displayed in real time;

[0012] In summary, the present invention can detect the current punching press pressure in real time and accurately, and has good repeatability and reliability. Description of the Drawings

[0013] Figure 1 It is the front view of the punching press pressure detection system used in the embodiment of the present invention. Detailed Embodiment

[0014] The following combines with the embodiments to further elaborate on the present invention in detail.

[0015] Such as Figure 1As shown in the figure, the punch pressure detection system used in this embodiment includes a crankshaft 1, a ball head screw 2 threadedly connected to the crankshaft 1, a synchronous pulley mechanism 3 connected to one end of the crankshaft 1, a slider 4, a hydraulic cylinder 5 and a piston 6 provided in the slider 4. The ball head is connected to the slider 4 and cooperates with the piston 6. The hydraulic cylinder 5 is connected to a hydraulic pump 8 through an oil pipe 7. A three-way joint 9 is provided on the oil pipe 7, and a hydraulic sensor 10 for detecting the pressure in the oil pipe 7 is provided on the three-way joint 9. An angle encoder 11 is provided on the driven pulley of the synchronous pulley mechanism 3. Both the hydraulic sensor 10 and the angle encoder 11 are connected to a programmable controller 12, and the programmable controller 12 is connected to a touch screen 13.

[0016] The punch pressure detection method for the above system includes the following steps: A) Establish the corresponding relationship between the detected pressure of the hydraulic sensor 10 and the punch pressure when the slider 4 moves downward by setting a tonnage meter on the punch, and store it in the programmable controller 12; B) Set the angle of the crankshaft 1 rotating to the bottom dead center as the reference angle, and set the crankshaft rotation angle range within 15° before the reference angle and 5° after the reference angle as the measurement range; within the measurement range, every time the angle encoder 11 detects that the crankshaft 1 rotates 1°, the programmable controller 12 immediately collects a pressure value through the hydraulic sensor 10 and stores it; C) The programmable controller 12 converts the pressure values collected by the hydraulic sensor 10 during each measurement into the punch pressure according to the corresponding relationship between the detected pressure of the hydraulic sensor 10 and the punch pressure when the slider 4 moves downward, and takes the maximum value among them as the punch working pressure when the slider moves downward this time, and displays it through the touch screen 13.

[0017] During operation, the crankshaft 1 rotates one week, driving the slider 4 to move downward and upward to complete a stamping stroke; the maximum pressure value of the punch is related to the angle of the bottom dead center of the crankshaft 1. Theoretically, when the crankshaft 1 rotates to the bottom dead center (that is, the crankshaft rotates 180°), the punch pressure reaches the maximum. If it rotates one more degree (>180°), the pressure has started to decrease. If it rotates one less degree (<180°), the pressure has not reached the maximum value. However, due to the changes in the dimensions and mechanical properties of the upper die, lower die and workpiece during stamping, the maximum pressure value of the punch is usually not at the position when the crankshaft 1 rotates to the bottom dead center, and usually can only be determined within a certain angle range; if only the hydraulic sensor 10 is used to continuously detect the oil pressure, since the downward speed of the slider 4 is fast and the stamping time is short, usually the time to complete stamping is only a few tenths of a second. Within such a short time period, the oil pressure in the hydraulic cylinder 5 and the oil pipe 7 changes greatly. The operation speed of the programmable controller 12 cannot meet the requirements of continuous detection and operation, and the accuracy of instantaneous parameters is poor, resulting in large detection errors.

[0018] In the present invention, each time the slider 4 descends and stamping is performed, the pressure of the punching press causes a change in the oil pressure in the hydraulic cylinder 5. Within the measurement interval including the stamping process, every time the crankshaft 1 rotates by 1º, a start command is issued by the angle encoder 11. The hydraulic pressure sensor 10 detects the oil pressure in segments and multiple times in the area near the bottom dead center of the crankshaft rotation, avoiding the problem of large detection errors caused by the programmable logic controller due to a large amount of stored data and the inability of the operation speed to meet the requirements of continuous detection and operation. The accuracy of the instantaneous parameters is good, and the current punching press pressure can be detected in real time and accurately, and the repeatability is good. Compared with the electronic stress gauge, the hydraulic detection has no fatigue deformation error and good reliability. A smaller unit angle can improve the detection accuracy. It is also possible to set the angle encoder 11 to detect that the crankshaft rotates by 0.5º each time. The programmable logic controller 12 immediately collects a pressure value through the hydraulic pressure sensor 10 and stores it. The detection error of the punching press pressure in this embodiment is already lower than 1.5%, which can meet the accuracy requirements. The touch screen 13 can display the current punching press pressure in real time. The angle encoder 11 is arranged on the driven wheel of the pulley mechanism 3, which can eliminate the influence of the vibration of the crankshaft 1 during stamping on the detection of the rotation angle, improve the detection accuracy, extend the service life of the angle encoder 11 and facilitate installation.

Claims

1. A method for detecting the punching pressure, the punching pressure detection system used therein includes a crankshaft, a ball screw connected to the crankshaft, a slider, a hydraulic cylinder and a piston disposed within the slider. The ball head is connected to the slider and cooperates with the piston. The hydraulic cylinder is connected to a hydraulic pump through a hydraulic pipe, and a hydraulic sensor for detecting the pressure inside the pipe is provided on the hydraulic pipe. An angle encoder for detecting the rotation angle of the crankshaft is provided on the crankshaft. One end of the crankshaft is connected with a pulley mechanism, and the angle encoder is disposed on the driven wheel of the pulley mechanism; both the hydraulic sensor and the angle encoder are connected to a programmable controller, and the programmable controller is connected to a touch screen; it is characterized in that The steps include the following: A) Establish the corresponding relationship between the detection pressure of the hydraulic sensor and the press pressure when the slider descends, and store it in the programmable logic controller; B) Set the angle when the crankshaft rotates to the bottom dead center as the reference angle, and set the crankshaft rotation angle range within a certain range before and after the reference angle as the measurement range; within the measurement range, every time the angle encoder detects that the crankshaft rotates by one unit angle, the programmable logic controller immediately collects and stores a pressure value through the hydraulic sensor; C) According to the corresponding relationship between the detection pressure of the hydraulic sensor and the press pressure when the slider descends, the programmable logic controller converts the pressure values collected by the hydraulic sensor each time within the measurement range into press pressures, and takes the maximum value among them as the press working pressure when the slider descends this time.

2. The punch pressure detection method according to claim 1, characterized in that: In step A), the corresponding relationship between the detection pressure of the hydraulic sensor and the press pressure when the slider descends is established by setting a tonnage meter on the press.

3. The punching press pressure detection method according to claim 1 or 2, characterized in that: In step B), the crankshaft rotation angle range within 15° before the reference angle and 5° after the reference angle is set as the measurement range; the unit angle is set as 1°.

4. The punch pressure detection method according to claim 3, characterized in that: In step C), the press working pressure when the slider descends this time is displayed through the touch screen.

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