Application and effect of Emerson frequency converter in lathe
Emerson Inverter in lathe applications And the effect, today, Shanghai Kuan Ying Automation Equipment Co., Ltd. to tell everyone.
First, the machine tool overview
This machine tool is a piston ring trapezoidal surface semi-automatic lathe developed by our factory to meet the needs of the piston ring industry. Double spindle; hydraulic drive longitudinal and horizontal feed; the spindle head is equipped with an electromagnetic chuck, equipped with a special clamp to clamp the piston ring; All actions of the entire machine are coordinated by PLC (Mitsubishi FX280MR). After pressing the auto start button, the machine can automatically complete the electromagnetic chuck excitation, the spindle start, the tool holder horizontal longitudinal fast forward, the horizontal work forward and other actions; after the cutting is completed, the machine tool can automatically complete the vertical and horizontal return of the tool holder, the suction cup demagnetization, the cylinder Push the nozzle to blow off the iron filings, the spindle stops and is accurately positioned. The machine tool has the following requirements for the main shaft: the main shaft must have six speeds (67r/min, 144r/min, 198r/min, 271r/min, 372r/min, 510r/min), and the higher five-speed speed is used for machining. Called the processing speed; the first speed is used to blow off the iron filings with the nozzle, so it is also called the chip removal speed. After the piston ring is turned, the spindle should be reduced from the machining speed to the chip removal speed, and the delay is a few seconds. After the chip removal is completed, the spindle brakes and is accurately positioned (the proximity switch detects the spindle position and sends a signal to the PLC) to remove the piston ring. Therefore, the spindle should be frequently started, slowed down, and braked during the working of the machine. If the conventional mechanical shifting is used, the electromagnetic clutch must be used. The gearbox is bulky, mechanically loud, and easily damaged. The frequency converter has the characteristics of being able to start, shift, and brake without frequent mechanical shocks. Therefore, we use the inverter to control the spindle motor, and the spindle motor output shaft directly drives the spindle through the belt.
Second, the selection of Emerson inverters
When the spindle motor runs at low speed, the speed of the cooling fan coaxial with the rotor of the motor is also reduced, resulting in a decrease in the heat dissipation capability of the motor. Therefore, although the piston ring has a small amount of turning, a certain power margin must be left in the selection of the motor. The 15kW, 6-pole ordinary motor is used, and the rated current is 397A.
The Japanese Mitsubishi A series 400V inverter is used, the model is FRA04415KP; the rated current of the inverter is 4A, which is greater than the rated current of the spindle motor. . This type of inverter is a high-performance small general-purpose inverter with the characteristics of an excavator. The frequency converter can also be controlled by the general vector control.
Third, control principle
The input side uses an air circuit breaker with an overcurrent release rated current of 15A for short-circuit protection. The multi-stage speed function of the inverter is used to achieve the required five-stage machining speed and chip removal speed. The five-stage machining speed is selected by the band switch on the button station. The five contacts of the band switch are used as the five input points of the PLC. The output points of the PLC control relays KA0, KA1, KA2, and KA3 normally open contacts are open! close! . KA0 controls the start and stop of the inverter; KA1, KA2, KA3 contacts open! close! Different combinations of
can select one of the multi-speed speeds of the inverter.
Each speed of the multi-speed can be set with its corresponding parameter.
The parameter Pr26 corresponds to the chip removal speed.
When the spindle is working, press the start button, the PLC controls KA0 to close, the inverter starts, and the spindle accelerates to a certain processing speed selected by the band switch. After the turning is completed, the tool holder enters the detection micro switch to send a signal to the PLC, the PLC control KA1, KA2 is closed, the cutting speed is selected, the inverter output frequency is quickly reduced from the machining frequency to the chip removal frequency, the spindle motor feedback brake, the spindle speed It also quickly drops from the machining speed to the chip removal speed. After the chip removal is completed, the nozzle in-situ micro switch sends a signal to the PLC. At the same time, the spindle position detection proximity switch also sends a spindle stop signal to the PLC. The PLC control KA0 is disconnected, the inverter output frequency is reduced, and the spindle motor feedback brakes. When the DC action value set by the inverter is reduced, the inverter outputs DC, the spindle motor consumes energy, and the spindle stops and positions quickly.
IV. Installation of Emerson Inverter
To prevent the inverter from interfering with the PLC, the inverter and PLC are installed in two boxes. The control signal output by the PLC is isolated by the relay and then introduced into the inverter installation box through the metal hose. The output line of the frequency converter is introduced into the motor via a separate metal hose. Because the inverter uses high-frequency carrier modulation output, the skin effect reduces the effective cross-sectional area of the wire, and the input and output lines of the inverter use 25mm2 copper core wire.
V. Debugging and parameter setting
There are many parameters to be set before the inverter runs. Only the main parameter settings are explained here.
1The base frequency Pr3 and the base voltage Pr19 are set to the rated frequency of the spindle motor 50Hz and the rated voltage 380V respectively.
2 Multi-speed setting Pr4=21Hz, Pr5=30Hz , Pr6=40Hz, Pr24=55Hz, Pr25=75Hz, Pr26=10Hz.
The required speed is achieved by adjusting the main pulley diameter of the transmission.
3 Torque boost setting The Pr0 torque boost should be set so that the inverter does not exceed the rated output current when it is running at low frequencies. Convert the operation mode to the parameter unit operation mode, make the inverter run at 10Hz, and then convert the frequency display on the parameter unit to the output current display. If the output current exceeds the rated output current, increase the torque boost setting value. .
4 acceleration and deceleration time setting Pr7, Pr8 acceleration time should not be too short, the motor starting current does not exceed the rated output current of the inverter is appropriate; deceleration time should not be too short, the inverter when decelerating The output frequency is reduced, the spindle motor feedback brake, the deceleration time is too short, and the voltage fed back to the inverter by the motor is too high, which will cause the inverter DC intermediate circuit to overvoltage and trip.
5 DC braking parameter setting refers to the setting of the DC braking action frequency Pr10, the setting of the DC braking voltage Pr11, the setting of the DC braking action time Pr12. These three parameters Properly set up can improve the positioning accuracy of the spindle.
VI. Concluding remarks
In the equipment with small adjustment range, small quantity and tight manufacturing period, the general frequency converter can be used instead of the traditional mechanical gearbox to save the gearbox. The time of mold making and box processing is convenient to adjust the rotation speed during the trial production process, which can greatly save the trial production time; mechanical noise, mechanical shock and other problems can also be solved; it is a better solution. The inverter with closed-loop vector control can match the dynamic and static performance with the DC speed control system. The speed range can even reach 1000, which is widely used in papermaking machinery printing machinery and elevators where high requirements are required.
