Nov 25, 2020
Application of frequency converter on metal wire drawing machine
1. Introduction to the system scheme
The double-frequency wire drawing machine can realize the step-by-step drawing of various wires and quickly wind the finished product. It is generally used for the processing of wires above 0.1mm. The metal wire is put into the drawing box after the wire is paid off, and is gradually drawn through various molds to achieve the required specification of the wire, and then the finished metal wire is evenly wound on the spool through the wire guide wheel motor.
2. Process introduction
·Pay-off: The pay-off process of the wire of the drawing machine does not require high-precision control for the entire drawing machine link. The drawing machine with double frequency conversion control uses the wire tension in the drawing link to stretch through the disc, that is, through The tension of the subsequent process drawing is automatically paid off.
Wire drawing: different metal materials, different product precisions and requirements, the drawing link is very different, the drawing part is controlled by a main motor (called the host), the metal wire is guided by the internal tower wheel, and passes through the molds at all levels And gradually stretch to achieve the required specifications of the wire. At the same time, when drawing, turn on the coolant to cool the mold.
Rewinding: Rewinding is the most critical link of the double-frequency wire drawing machine, which has a decisive influence on the performance of the wire drawing machine and is also an important basis for testing the electrical system of the wire drawing machine. Rewinding is driven by a rewinding motor to rewind the reel. The wire comes out of the drawing part and passes through the tension pendulum rod. The function of the tension pendulum rod is to feed back the current tension signal to the slave machine. The slave machine adjusts the output frequency according to the deviation of the feedback signal. , In order to ensure a constant tension during the winding process. The wire rises to a guide wheel through the tension swing rod, and then is drawn to the guide wheel of a wire winding machine. The wire winding machine is driven by a single small motor for reciprocating motion. The function is to arrange the wire evenly on the winding reel and wind it. The motor drives the reel to rotate, and the wire guided by the wire arranging machine is automatically wound onto the reel. This completes the entire winding process. When the winding is abnormally disconnected, the system needs to automatically stop and open the brake to quickly stop the winding reel.
Three, the advantages of frequency converter in the application of wire drawing machine
1. Excellent control of the swing lever in the winding part. The pendulum rod reflects the consistency of the synchronous operation of the stretching part and the winding part and the stability of maintaining the tension on the line. Generally, when the rewinding speed is faster than the stretching speed, the pendulum rod will rise, otherwise the pendulum rod will sag. Because the inverter has built-in advanced PID calculation and has 2 groups of PID parameters at the same time, the PID parameters can be selected as a single parameter group or two groups of parameters can be automatically adjusted according to the operating frequency. It can solve the oscillation of the swing rod caused by the change of the winding diameter of the reel. It also takes advantage of the inverter's fast torque response and high speed stabilization accuracy, ensuring that no matter the current position of the pendulum rod at startup, it can reach the equilibrium position without oscillation at one time, and the pendulum rod is stable and free of vibration regardless of the current speed during operation.
2. Smooth operation when inching through the mold. Before starting the whole machine, the front end of the raw material must be polished manually and passed through the mold step by step. Due to frequent jogging when threading the mold, the stretching motor is switched repeatedly under the state of static, acceleration, low-speed operation, deceleration, and static. Our inverter has large torque and stable running speed when starting and running at low speed, and the motor does not reverse rotation when decelerating to stop. Automatic calculation of roll diameter. The double frequency conversion wire drawing machine can choose the method of calculation according to the line speed. For materials with a fixed material thickness and a stable roll diameter increasing rate, the material thickness can also be calculated. The feedforward value is adjusted through the change of the winding diameter, so that the entire winding process is accurately pre-adjusted, so as to ensure the stability of the entire winding process of the wire drawing machine.
3. Multiple relay outputs. The inverter relay (FB.FC) of the wire drawing host is a disconnection fault alarm output, and the relay (KA, KB) is the output of the low-frequency brake when the system decelerates and stops to realize the low-speed braking of the winding motor. The coiling motor inverter relay (FB, FC) is the disconnection fault alarm output, and the relay (KA, KB) is the start-stop circuit of the winding motor. Make the design of the control circuit simple and convenient, and ensure the safety and continuity of the operation system that stops due to an abnormality.
to sum up
The host of this system adopts open loop vector speed control and outputs the current running speed of the host to the AI terminal of the winding inverter through the AO analog terminal as the main speed setting of the winding part. PID adjustment is performed through the feedback of the position swing lever, and the result of the PID adjustment is given as the auxiliary speed of the winding part. Realize the stepless speed regulation of the stretching stage and the constant tension control of the coiling. After optimizing the parameter values, the maximum linear speed of the equipment is very stable. This system solves the problems of high cost, complex system, difficult maintenance, high maintenance cost, and poor system control response caused by the previous use of PLC or industrial computer control.