Transformation of Constant Tension Control System on the Dual- frequency Wire Drawing Machine Winding

Abstract: 

With the increasing process requirements and human costs in cable industry, requirements on wire drawing machines are also becoming tougher and tougher. Original inverter control winding system, which needs human assistance to start, has too large acceleration and can’t cut line to stop in emergency, fails to satisfy current process needs. The article introduces a winding program combining V360 high performance inverters and drawing machine expanding cards developed by Shenzhen Simphoenix Electric Technologies Co., Ltd. The program is applied to dual-frequency wire drawing machines in eastern China. It improves greatly the efficiency of the labor of workers at site, reduces the rate of disconnection in operation and enhances product quality.

Keywords: Inverter; Wet wire drawing machine; Tension control

Introduction

Electrical wire and cable industry is the second largest industry, only second to the automotive industry and its products are used in many industries. Wire drawing machines are important equipments in metal wire production. Its main function is to draw wire rods into fine wires of various specifications. Based on the working mode and mechanical structure, they can be divided into the direct type, the looping type, the tank type (also called dual-frequency wire drawing machine) and so on. Wire drawing machines of different specifications are selected to produce products of different accuracy, specification and metal. Dual-frequency wire drawing machines are used widely in wire and cable manufacturers of copper and aluminum, while direct wire drawing machines are used in most steel production companies due to the characteristics of steel.

The transformation customer is a manufacturer producing both wire drawing machines and wires in eastern China. Electrical control program is optimized on the base of optimizing the mechanical structure and its performances can be compared with those of original program effectively.

1. Introduction of dual-frequency wire drawing machine process

Tank dual-frequency wire drawing machine system usually consists of pay-off, drawing and winding, shown in Figure 1.

Pay-off: Accuracy requirement of wire pay-off process is not quite high in the wire drawing machine. Dual-frequency wire drawing machine uses wire tension disc for drawing, which is to pay off automatically by the tension pay-off stand.

Drawing: Drawing differs a lot in different metal, product accuracy and requirements. It is controlled by a main motor (called the hose).Metal wire is guided by internal wheel and drawn gradually by molds of each level to produce required wires. When drawing is started, cooling liquid is open to cool molds.

Winding: Winding is of great importance in dual-frequency wire drawing machines, plays a decisive role in performances and is also a vital basis for evaluating electrical performances. Winding is realized by a winding motor. The winding motor (slave machine) drives the winding plate to wind wires. After getting out of drawing, wires go through the tension swing bar, which feeds current tension signal back to the slave machine. Then the slave machine adjusts output frequency on that signal to ensure constant tension.

1. Introduction of site process and adjustment program

1. Requirements of Site Processes

The system is a tank wire drawing machine with 19 molds, a 1.5mm in-wire and a 0.15mm out-wire. Its requirements are as follows:

① Stable start acceleration. Iron wires of 0.15mm are required be stable and not to break in starting winding, acceleration, deceleration and other processes;

② The stable operation speed is 900m/Min.(Inverter operation frequency without plate is 42HZ, with full plate is 21HZ);

③ During the operation, range of the swing bar is small and operate stably.(Frequency change resulting from winding changes is within 1HZ);

④ It should have emergency shut-down function (the whole system should be able to be shut down in 2S, being broken lines);

⑤ It should have the function of automatic broken line detection (detect broken lines automatically on the position of swing bar without external signals).

2. Transformation program overview

Original system program: main drawing and winding use dedicated inverters for wire drawing machines

Transformation program: main drawing: V360 series inverters winding: V360 series+ dedicated cards for wire drawing machines

3. Features of transformation program

The program is developed based on a new vector control platform. There are four core control algorithms, namely a closed-loop vector, an open-loop vector, V/F and torque control. Combining site wire drawing machine processes, expanding cards of wire drawing machines adopts an intelligent control algorithm to achieve winding performance requirements of an 80% start torque, overshoot of the swing bar within 10% in acceleration and deceleration and steady-state wave motion less than 5%.

The system program has following features:

1)  Flexible recipe convenient for installation, replacement and upgrade;

2)  Own intelligent CPU control system for more precise and faster control;

3) With a variety of compensation functions to ensure smooth acceleration and deceleration and stable operation;

4)  According to working environment of wire, winding diameter is calculated on special calculation and compensation methods. It tracks current actual winding diameter in time to reduce PID adjustment and maximize swing bar stability;

5)  Provide several blank winding settings for flexible selection. Current winding diameter can be eliminated automatically or manually. Automatic memory is realized in power failure or power down;

6)  There two groups of PID for continuous switch, satisfying requirements of smooth start in blank plate and full plate.

7) Provide various methods on setting system wire speed and winding diameter calculation, which can be set easily;

8) Standard configured keyboard has the parameter copy function to avoid repetitive function set.

1. System debugging and specification

1. System Wiring Diagram:

Common wiring diagram of dual-frequency wire drawing machine is shown in Figure 2:

Figure 2 System Wiring Diagram

1).  Main drawing and winding are in parallel connection and started simultaneously;

2).  Jog signal of main drawing is used when main drawing wires;

3).  Main winding signal is given by AI2. AI2 signal source is main drawing AO1 (operation frequency); feedback of the swing bar is given by AI1;

4).  Winding is responsible for broken line detection and send emergency shut-down signal to main drawing.

2. System control diagram

Schematic of drive system in dual-frequency wire drawing machines is shown if Figure 3:

Figure 3 System block diagram

Main drawing motor is main active force in the system. Its conversion frequency is usually set by analog signals (or communication, etc.). Winding, as the slave system, is responsible for tension control. Winding frequency signals are divided into two parts. The first part is determined by frequency signals of main drawing and current calculated winding diameter. The second part is determined by PID adjustment done by swing bar feedback. Superpose these two parts to ensure constant tension and stability in the system.

1. Debugging parameters:

Main parameters of winding system are as follows:

4. Debugging summary

Common solutions to problems in debugging

(1) Winding response speed:

① Start frequency (3HZ) is set through main drawing to avoid delay resulting to lack of low-frequency torque in full plate start; ② Adjust initial winding diameter of wire drawing machine cards. The smaller the initial winding diameter is, the faster the response is; ③ Set equilibrium transition position on wire drawing machine cards and increase the transition for faster response; ④ Increase P of PID properly.

(2) Smoothness in operation:

It is basically related to two groups of parameters: the first group is P and I in PID; smoothness can be improved by decreasing P and increasing I; the second group is smoothness in transition position; smoothness can be improved by decreasing transition position (not recommended for more than 20%).

IV. Comparison before and after transformation

Conclusion

After transformation, on the premise of reducing system costs, the faster the system response is, the lower the human labor is and work efficiency is enhanced greatly. High stable operation state reduces broken line rate and improves product quality. Practice has proved that transformation program is a high stable and reliable wire drawing machine winding driving program, which can satisfy modern requirements.

References:

1. JB/T 7910-1999 Standards of Drawing Machine in National Machinery Industry

2. Metal, Sinosteel Zhengzhou Research Institute of Steel Wire Products

3. Specifications of V360 Series High Performance Vector Inverters, Shenzhen SIMPHOENIX Electric Technologies Co., Ltd.

4. Specifications of Dual-Frequency Wire Drawing Machine Expanding Card, Shenzhen SIMPHOENIX Electric Technologies Co., Ltd.