Application of Capacitive Sensor in Flame Cutting Machine

In many large equipment manufacturing companies and shipbuilding industries, flame cutting machine is widely used to cut steel plates. Capacitor height and low regulators are essential components in cutting machines. The main function of this equipment is to ensure the cutting torch head of the cutting machine. The workpiece to be cut always maintains the optimum cutting distance, thereby eliminating the machining accuracy error caused by the unevenness of the workpiece being cut and ensuring the cutting quality.

The capacitance C of the plate capacitor is determined by the working area of ​​the plate S. The dielectric constant e of the dielectric between the plates and the distance S11 between the plates. The relationship between these parameters is as follows: the sensor circuit is a crystal oscillator, high frequency detection And comparison op amp components. The crystal oscillator generates a frequency of 6M Hz, which is divided into two channels, one is sent to the high frequency upper detector composed of R4D and 05R6, and the other is sent to the capacitance probe and the high frequency lower detector composed of R5邙 and 6R7. After the high frequency detection, the frequency signal is amplified by the differential voltage, and an amplified slow voltage is output. This voltage is changed because the capacitor ring is fed back to the 06R7 from the capacitor ring during the high and low movement of the metal plate. The signal of the detector at high frequency is a high-frequency voltage signal that changes. The DC signal that is output through the detection is also a slow signal. When the change signal at the positive end of A1 is compared with the constant signal voltage at the negative end of A1, the capacitor ring is used. The change signal induced to the steel plate is converted into a slow DC voltage output signal by A1. Prepare for the comparison amplifier circuit (see).

The probe circuit 3 amplifies the comparison circuit. The DC signal voltage from the capacitance sensor circuit and the DC voltage at the midpoint of the VRZ potentiometer are superimposed on the opposite end of A2. Through the linear amplification of A2, the DC voltage is output at the output of the A2. Potentiometer V2 midpoint voltage, the actual output voltage is sent to the forward end of A4, the other end is sent to the inverting input of A5, adjust the midpoint voltage of VR3 potentiometer, you can change the reverse voltage of A4 and A5 at the same time The forward voltage, E5 acts as the clamp voltage. When the A2 output voltage falls between the E5 clamp voltages, there is no output voltage between A4 and A5. When the A2 output voltage is greater than the A4 reverse voltage, the A4 output is high. Ping, the upper is to change the actual detection distance of the capacitance probe from the steel plate, hAublisp LED is bright when the output 蔌 is less than vA5 positive. The net adjustment has higher priority than the automatic up and down adjustment. Therefore, in the actual work site, when it is in the automatic state, if it encounters an emergency state, manual manual emergency intervention can be performed. Press the up button or the down button to avoid accidents caused by steel plates or obstacles. Occurs (see) 4 Photoelectric coupling and motor drive circuit The high and low adjustment signal from the amplification comparison circuit (see) is sent to the power drive circuit through the apertures G1 and G3. The function of the aperture is to drive the motor drive circuit part and the amplification comparison circuit part. Through the optical isolation, the strong electric and weak electricity are separated, so that the motor interference and the on-site interference will not enter the amplification comparison circuit.

When the rising signal passes through G1, the LED of D10 turns on and illuminates, and a voltage is established on the resistor of R27, which is applied to the 12-pin terminal of the 2-legged gate and the tri-state gate of the tri-state gate S, at the same time, 03 No signal, D12 LED is cut off, no voltage can be established on the R29 resistor. The low level signal passes through the tri-state gate and is output to the S1 tri-state gate control terminal, and the S tri-state gate strobe. While S1 is turned on, the gated output signal is applied to the S tristate gate control terminal to block the S tristate gate conduction. This state is S, S, S strobe.

When the falling signal passes through 03, the LED of D12 turns on and illuminates, and a voltage is established on the R29 resistor, which is applied to the 9-pin of the tri-state gate S and the 5-pin end of the tri-state gate S. At the same time, since there is no signal, the D10 LED is turned off, and no voltage can be established on the R27 resistor. The low level signal is gated; while the S2 is turned on, the gated output signal is added to the S. The tri-state gate control terminal, blocking S. This state is the S3S4 strobe.

Now let's look at the case where the DC motor M is reversing. When S1S2S4 is strobed, T, T, and T6T4To are turned on; T, T3T and T9 are turned off. At this time, since TS and To are turned on, the rectified DC 110V voltage is directly applied to both ends of the motor, the motor rotates forward, and the capacitance probe is lifted; When S2S and æ±¾ are strobed, T and T7T3T8T are turned on; T, T5T6T, and T are cut off. At this time, since T and T7 are turned on, the rectified DC voltage of 110V is directly applied to both ends of the motor, the motor is reversed, and the capacitance probe is lowered; This circuit is inevitably subject to external electromagnetic interference or mis-operation while pressing the "up" and "down" buttons. At this time, it is possible to cause 1 and 3 simultaneous gating, but since the 74LS125 tri-state gate has protection, it is only allowed to rise. A signal or a falling signal passes through a signal, and the circuit is interlocked to avoid burning out the subsequent drive tube. When the current of the motor exceeds the rated current of T6T or T, T drive tube, it is possible to burn the drive tube. In order to avoid burning the drive tube, this circuit uses 74LS25 three-state door interlock, and the second is at T7 and To. The emitter plus the sampling resistor, when the sampling voltage exceeds the on-voltage of the aperture, the output of the aperture is output to the tri-state gate. The end of the three-state bli will short-circuit the signal g voltage, so that the signal voltage can not pass. Net optical coupling and motor drive circuit 5 Conclusion Capacitive sensor has many advantages in the CNC flame cutting machine cutting steel plate. It can automatically detect the unevenness of the steel plate and adjust the distance between the torch and the steel plate through the closed loop feedback loop. Thereby reducing the labor intensity of the operator, improving the cutting precision and automation, safe and reliable.

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