JT500 inverter application on straight-line wire drawing machine

I. Introduction of Wire Drawing Machine

The wire drawing machine, also known as a wire drawing bench, refers to a mechanical device that processes metal materials through pressure at room temperature using a drawing die. By stretching, the machine can process wire into various specifications needed. It is widely used in industrial applications, including mechanical manufacturing, metal processing, petrochemicals, plastics, wood and bamboo products, wire and cable industries, among others.

II. Process Introduction

1. Pay-off: In the wire drawing process, there is no high precision requirement for the pay-off of wire drawing machine lines. In a wire drawing machine controlled by dual-frequency, the wire is automatically paid off using the tension of the wire during the wire drawing process through the disc stretch, which is done automatically through the tension pay-off stand.

2. Drawing: The drawing process varies significantly depending on the metal material, product precision, and requirements. The drawing part is controlled by a main motor, and the metal wire is gradually stretched through the guidance of internal pulleys and various levels of dies to achieve the desired wire specifications. Cooling liquid is applied during drawing to cool the dies.

3. Take-up: Take-up is a critical part of the dual-frequency wire drawing machine, which has a decisive impact on the performance of the wire drawing machine and is an important basis for testing the electrical performance of the wire drawing machine. The take-up is driven by a take-up motor to wind the wire. The wire comes out of the drawing part, goes through a tension pendulum, and the role of the tension pendulum is to provide feedback on the current tension signal to the main machine. The machine adjusts the output frequency based on the deviation of the feedback signal to ensure constant tension during take-up.

4. Characteristics of the Wire Drawing Machine:

• The drawing part has stepless speed regulation, high starting torque, and stable operation.

• Ensure constant line speed when the take-up radius changes from small to large.

• The machine can be directly started at any position of the pendulum without manual assistance during startup.

• The tension pendulum remains stable throughout the operation. When a change in tension is detected, the take-up should respond quickly to return to a constant tension state.

• Ensure smooth transition during startup and shutdown and maintain a certain tension to prevent wire breakage.

• During threading, the drawing motor needs to run inching.

• In the event of a wire break, a brake signal is required to overcome the inertia of the take-up and prevent the originally wound wire from unraveling.

• Stop and start are possible at any time, regardless of the current take-up status (empty spool, half spool, full spool).

III. Working Principle of Dual-Frequency Wire Drawing Machine

The main drawing inverter actually performs a simple speed regulation but requires an output frequency change signal (i.e., analog AO output signal, with AO function selected as the output frequency) as the speed reference for the take-up inverter. The take-up wire drawing machine calculates and synchronously outputs the frequency based on the signal sent by the main machine and the feedback voltage signal of the tension pendulum. The calculation takes into account different speeds of the main machine, different diameters of the take-up spool, and different positions of the pendulum.

The pay-off motor and the take-up motor are controlled by two inverters, respectively. The pay-off inverter adjusts the speed through an external analog signal, and the take-up inverter is controlled by the frequency change output signal of the pay-off inverter and the feedback signal of the tension pendulum. After analog adjustment, it controls the take-up inverter. As the winding drum diameter changes during take-up, the feedback signal of the tension pendulum also changes. This signal, combined with the analog AO output signal of the pay-off inverter, constitutes two analog input signals. After auxiliary analog addition, the wire is kept at a constant line speed.

As the take-up motor is controlled in analog mode, it can automatically synchronize with the main drawing, and the position of the pendulum is generally kept in the middle position, which in a sense ensures the constant tension of the take-up.

IV. Parameter Description (Main Machine Part)

• F0.02: 1 (external start)

• F0.03: 2 (external potentiometer speed control)

• F0.17: 40 (acceleration time)

• F0.18: 40 (deceleration time)

• F2.00: 1 (forward operation)

• F2.01: 4 (forward jogging)

• F2.02: 9 (fault reset)

• F3.03: 2 (fault indication)

According to the solution provided based on the actual situation on the customer's site:

1. Pay-off: Free wire pay-off.

2. Drawing: Select a suitable inverter based on the actual motor power. After passing through multiple dies, the wire is gradually drawn to the required diameter.

3. Take-up: The asynchronous motor is driven by an inverter with suitable power. When the motor is in a stopped state, there is a brake action. The take-up device cannot rotate.

4. Tension Feedback: In the middle of the drawing and take-up process, there is a tension floating roller. The rear end of the floating roller is equipped with a single-turn potentiometer to provide feedback on the position of the floating roller, achieving the purpose of detecting tension.

V. Debugging Instructions

a. Calculate the required operating frequency of the main drawing inverter based on the line speed specified by the process.

b. Calculate the required frequency of the take-up based on the actual transmission ratio.

c. Set the default transmission ratio coefficient according to the mechanical rotation ratio when the take-up spool radius changes from small to large.

d. The acceleration and deceleration time of the main drawing inverter should be as long as possible (usually 40-60 seconds) for smooth acceleration and deceleration.

e. Adjust the balance position of the tension pendulum to ensure the mechanical midpoint corresponds to the feedback midpoint.

To facilitate the detection of wire breakage, during startup, first lift the pendulum to the balanced position. When the wire is tightened, release it to prevent the pendulum from being in the limit switch position, preventing the motor from starting. During debugging, first ensure that the open-loop vector mode of the main drawing and take-up inverters is normal. Calculate the required operating frequency of the take-up inverter based on the line speed specified by the process. Then, based on the actual transmission ratio corresponding to the main drawing frequency, ensure that the speed difference between the front and rear stages is not significant. Adjust the take-up inverter according to the analog signal feedback value of the tension pendulum.

VI. Debugging Precautions

1. The linear relationship between the voltage feedback signal of the pendulum position and the pendulum position must be correct. If incorrect, correct it by setting the external given amount characteristic curve.

2. Set a longer acceleration and deceleration time for the drawing motor to facilitate tracking by the take-up motor.

3. During normal operation, if the pendulum swings too much, check the meshing clearance between the two gears of the tension pendulum feedback signal and the pendulum.

4. During normal operation, if periodic sudden fluctuations occur, pay attention to the position of the traversing switch. If it is not in the correct position, uneven winding of the spool may occur, causing changes in the take-up diameter and further affecting the stability of the tension pendulum.

The successful transformation of the dual-frequency wire drawing machine application solution has reduced system costs, accelerated system response, simplified operation, and significantly improved work efficiency. The highly stable operating state has reduced wire breakage rates and improved product quality. In practice, the transformation solution introduced in this document is a highly stable, reliable, and practical wire drawing machine transformation solution that meets on-site requirements.