How to Apply Variable Frequency Technology on Drawing Machines?

Wire drawing machine can be divided into straight-line type and water tank type according to the drawing method, and it can also be classified into large wire drawing machine, medium wire drawing machine, thin wire drawing machine and micro wire drawing machine according to the diameter and thickness of the wire. They are all composed of stretching and winding parts. In order to improve production yield and quality, and reduce cable costs, wire drawing machines are generally converted to dual-frequency or multi-frequency constant tension control. However, most of the current variable frequency synchronous control generally uses external PID controllers. The disadvantages of this method are: difficult adjustment of control parameters of PID controller, expensive price, and easy to damage. In addition, there are attenuation and drift problems in the transmission process of analog signals, and the maintenance cost is relatively high. However, using a wire drawing machine frequency converter is more convenient in operation.  

1. The Straight-line Wire Drawing Machine is a Small Continuous Production Equipment Composed of Several Wire Drawing Heads

By step-by-step drawing, the steel wire can be cold-drawn to the required specifications once, and the working efficiency is relatively high. However, because the diameter of the wire changes after each wire drawing stage, the working line speed of each wire drawing head must also change. Its characteristics are multiple wire drawing heads, multiple frequency converters, and multiple PID adjustments.

Principles of Straight Line Wire Drawing Machine:

1) The working principle of the straight-line wire drawing machine is to control the metal flow of each coil to be always equal.

2) Utilize displacement sensors to detect the wear of the wire drawing die, the fluctuation of the motor speed, and the disturbance of the uneven wire thickness, and compensate using the PID algorithm.

3) Take the speed of the last coil as the main given value, and calculate the given values of other coils through the area reduction rate and transmission ratio.

2. Requirements for Wire Drawing Machine Frequency Conversion Speed Regulation Process

1) Ultra-low frequency torque, fast dynamic response characteristics, stable precision and stability, without shaking and trembling.

2) Integrate all tension control algorithms into the VFD, and integrate the special functions of the wire drawing machine into the VFD, so that all control functions of complex wire drawing machines can be realized without peripheral control circuit.

3) The main engine must not allow a break when starting and stopping. When disconnected, an alarm should be issued and emergency stop should be initiated.

4) Stable operation. During normal operation, the swinging rod should not collide with the upper and lower limits, and the drawing and pulling flow rate of each stage can be kept constant at the same time.

5) When stopping, maintain synchronous continuity, and always maintain the proportional relationship between the linear velocities of each level.

6) VFD integrates multiple special parameters of the wire drawing machine, and directly calls the corresponding parameters without requiring the customer to set the parameters one by one.

After connecting the feedback value of the tension balance rod to the special model of the wire drawing machine, when the tension rod swings towards the winding, monitor the PID feedback signal, and the value should change from small to large, generally from 0.0% to 100.0%. If it is not within this range, it is necessary to change the position of the tension potentiometer to make the center point around 50.0%. The tension potentiometer should be a 360° high-precision potentiometer. If the adjustment of the electric method is troublesome, you can also directly lift the drawing rod to the physical middle height position of the winding tension guarantee, and then set the feedback value of the potentiometer to 50.0%. This setting method is to ensure that when tension produces deviation, both positive and negative deviations can be buffered and stored with the same position distance deviation through the drawing rod.