How is Variable Frequency Technology Applied to Wire Drawing Machines?

How is Variable Frequency Technology Applied to Wire Drawing Machines?

Wire drawing machines can be divided into straight drawing and tank drawing methods, and can also be classified into large, medium, thin, and micro wire drawing machines based on the diameter and thickness of the wire. These machines consist of two parts: stretching and winding, and are generally converted to dual or multi-variable frequency constant tension control to improve production efficiency, quality, and reduce cable costs. However, most variable frequency synchronous controls currently use external PID controllers. The disadvantage of this method is that PID controller tuning is difficult, expensive, and easily damaged. There are also attenuation and drift problems with analog signals during transmission, resulting in relatively high maintenance costs. But using a wire drawing machine inverter is more convenient in terms of operation.

A straight wire drawing machine is a small continuous production equipment composed of several drawing heads. By step-by-step drawing, the steel wire can be cold-drawn to the required specifications at once, with relatively high work efficiency. However, since the wire diameter changes after each drawing stage, the working linear speed of each drawing head also needs to change. Its characteristics are multiple drawing heads, multiple variable frequencies, and multiple PID adjustments.

The working principle of a straight wire drawing machine is to control the metal flow of each spool to be equal at all times. Using displacement sensors to detect wear on the drawing die, motor speed fluctuations, and thickness variations, PID algorithms are used for compensation. The speed of the last spool is the main setpoint, and the setpoints of the other spools are calculated through the area reduction rate and the transmission ratio.

The requirements for variable frequency speed control technology in wire drawing machines include ultra-low frequency torque, fast dynamic response characteristics, stable precision, no shaking, and trembling. All tension control algorithms are integrated into the VFD, and the special functions of the wire drawing machine are also integrated into the VFD, which can realize all control functions of complex wire drawing machines without the need for peripheral control circuits. When the host starts and stops, it must not cause any broken wires. When disconnected, an alarm should be issued, and emergency stop should be performed.

During normal operation, the swing arm should not collide with the upper and lower limits, and the drawing flow rates of each stage can be kept constant simultaneously. During shutdown, synchronization should be maintained continuously, and the proportionality relationship between the linear speeds of each stage should always be maintained. The VFD integrates multiple special parameters of the wire drawing machine, and corresponding parameters can be called directly without the need for customers to set them one by one.

When the feedback value of the tension balance bar is connected to the special model of the wire drawing machine, the direction of the tension bar swing should move towards the winding direction, while monitoring the PID feedback signal. Its value should change from small to large, generally ranging from 0.0% to 100.0%. If it is not within this range, the position of the tension potentiometer needs to be changed, so that the center point is around 50.0%. The tension potentiometer should be a 360° high-precision potentiometer. If the adjustment of the electric mode is troublesome, the drawing rod can be directly lifted to the physical middle height position of the winding tension guarantee, and then the feedback value of the potentiometer can be set to 50.0%. This setting method is to ensure that when the tension produces deviation, both positive and negative deviations can be buffered and stored at the same position distance through the drawing rod.

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