**3.3 Working regime**

Once insured the threaded, the wrapping belts are completely removed, as can be seen in Figure 8, to look after the surface integrity of the strip. This action is performed by a pneumatic actuated scissor mechanism. Meanwhile, the spinning speed of the reel is reduced because during the threaded it was significantly higher; also, from this moment on, the dancer roller (8) can freely move in the vertical axis, and the tension sensor (13) is disposed as it is shown in Figure 8. From now on, the winder is at a working regime and we must proceed to the tension control of the roll.

The basic principle of the tension control is the small difference between the pinch roller´s speed and winding speed (represented by the tangential speed of the reel) which is slightly higher (He et al., 2010). The structure of the device for controlling the tension is shown in Figure 10. The tension measurement is used to tune up the spinning speed of the reel, by an asynchronous motor, variable frequency drive and encoder. The control set point establishes a tighter roll at the beginning and looser at the end, known as taper tension control (Good et al., 2008). With this system it is intended to obtain an optimum tension of the roll without inflicting any damage to the material.

A storage system is incorporated in order to prevent flaws on the tension control system, such as response time, slipping of the strip on the pinch rollers, lack of precision on electric

(main motor) is going to take most of the torque necessary for the winding, on the other hand the pinch rollers motor will be working almost as a brake because upstream it is a freetension zone and downstream the tension is provided by the main motor. This is why the power of the main motor is considered to take this torque times a service factor to make up for the startup situation. Taking into account these considerations and the dimensions of the

When the casting wheel starts throwing the first cuts of amorphous strip, the guiding belts (1) drag it towards the pinch rollers (2) where a first thread is done. At this point, it´s the first contact with the winding machine and it is found pure rolling friction between the strip and the pinch rollers, where these jog the strip forward with its own tangential speed. As a consequence, it is needed a high precision in the mounting of this rollers in order to preserve the clearance between them; if it is bigger than the designed one the strip would slip between them. But if it is smaller, the material would be damage by an operation similar to a laminate. Due to the constant contact between the strip and these rollers, it is recommended to pay close attention to the hardness during the material selection of the rollers in order not to damage the surface quality of the strip; several options appear like copper, brass or even PTFE (TEFLON®) inserts. Next to the pinch rollers (2) the strip is guided towards the winding reel (5) by the main deflector (4). The winding reel is spinning to a higher tangential speed than the speed of the strip in order to ensure the threaded. Additionally, the reel is surrounded by a wrapping belt (6) which guarantees the strip to follow the profile of the reel until there is enough friction between the successive wounds of strip, so to create a bond within the reel and the strip, but this won´t happen until several wounds of ribbon

Once insured the threaded, the wrapping belts are completely removed, as can be seen in Figure 8, to look after the surface integrity of the strip. This action is performed by a pneumatic actuated scissor mechanism. Meanwhile, the spinning speed of the reel is reduced because during the threaded it was significantly higher; also, from this moment on, the dancer roller (8) can freely move in the vertical axis, and the tension sensor (13) is disposed as it is shown in Figure 8. From now on, the winder is at a working regime and we

The basic principle of the tension control is the small difference between the pinch roller´s speed and winding speed (represented by the tangential speed of the reel) which is slightly higher (He et al., 2010). The structure of the device for controlling the tension is shown in Figure 10. The tension measurement is used to tune up the spinning speed of the reel, by an asynchronous motor, variable frequency drive and encoder. The control set point establishes a tighter roll at the beginning and looser at the end, known as taper tension control (Good et al., 2008). With this system it is intended to obtain an optimum tension of the roll without

A storage system is incorporated in order to prevent flaws on the tension control system, such as response time, slipping of the strip on the pinch rollers, lack of precision on electric

strip and the reel, it is needed a 5HP AC motor for the winding reel.

**3.2 Startup** 

had already been rolled over the reel.

must proceed to the tension control of the roll.

inflicting any damage to the material.

**3.3 Working regime** 

and electronic components. Every difference between the pinch rollers and the casting wheel speed, overcomes into an over-tension of the strip or an excessive storage of material, which may cause a possible detachment of the solidification meniscus.

Fig. 8. Wrapping belts and tension sensor at startup condition (3.1) in working regime (3.2).

Fig. 9. Stocking system at startup and during the working regime.

The mechanism is composed by 3 idle rollers (Figure 9), two of them (9) are fixed, while the centered one (8) can move along the vertical axis forcing the strip to take a larger profile instead of the straight line from the startup. Sensing the position of this roller, it is tuned up the pinch rollers speed, only when the stock is excessive or insufficient. So, this variation will be considered as a transitory regime for the tension control system, in order to assume the pinch rollers´ speed as a constant. With this system a little stock of ribbon is created in order to absorb every produced over-tension.

The winding reel (5) is provided with a mandrel for a quick demounting of the finished roll. Moreover, the reel along with the wrapping belt is mounted on a cross slide (7) which can be

Development of a Winding Mechanism for Amorphous Ribbon Used in Transformer Cores 287

crucial to prevent unwanted flaws (Saito, 2010; Marashi et al 2009) which include the absence of the formation of the strip on the casting wheel as can be seen in Figure 11. For this reason it is highly recommended to ensure the working conditions described along this

(a)

(b) Fig. 11. (a) Ejection of molten material on the wheel in a non-operational regime, (b) Ejection of molten material on the wheel in a operational regime; both photos on its own equipment

article.

in LSA.

moved over the sliding guides (12) in a cross direction, as can be seen in Figure 5 and 6. With this system several angular defects during the tuned-up before the startup of the equipment are corrected.

Fig. 10. Control System Structure: 1. Casting Wheel; 2. Encoder; 3. Position Sensor; 4. Tension Sensor; 5. Pinch Rollers; 6. Winding Reel; 7. Asynchronous Motor; 8. Variable Frequency Drive; 9. PLC.
