Running off of steel strip is the most common faults in color coating machine. Wear of rollers is caused by slight running of steel strip, and color mixing occurs on both sides of the coating plate. Heavily, the tension on on both sides of the strip is
uneven or the wear deformation is caused by severe friction between the steel strip and the rack. When serious, it is necessary to stop the machine to deal with the steel strip correctly. The problem of deviation is related to the normal operation
of the whole production system.
In fact, there is only one common reason for strip deviation, that is, the strip is subjected to a transverse force at the same time at a certain speed. How does this transverse force come into being? As shown in Figure 35, assuming that a steering roll passed by the strip is not vertical to the center line of the unit during installation, the strip moves forward. The steering roll is given a forward traction F, which is decomposed into a force F that rotates the steering roll and a transverse force F. This transverse component causes the steering roll to move axially. Since the fixed support of the steering roll can not move axially, it will inevitably produce some reaction force F on the steel strip, which causes the steel to move to the other side, leading to deviation.
It is not difficult to understand the reason of steel strip deviation when the steering roll is deflected. The method of adjustment is also clear. The best way is to process the growing holes on both sides of the steering roll in order to adjust. The specific adjustment method is shown in Figure 3-6. When adjusting, which side of the steel strip deviates, which side of the steering roll will move forward towards the steel strip of the unit, or the other side will move backward.
In addition to the transverse force caused by the installation of rollers or racks, the following phenomena of deviation are caused by the external transverse force on the steel strip, but ultimately the causes and treatment methods can be found through the analysis of the force.
A deviation phenomenon
(1) The strip shape is not good, the thickness of both ends is not uniform, resulting in uneven tension at both ends of the strip, and the strip always deviates from the side with high tension. In view of this situation, it can be eliminated by adjusting the driving roll or improving the tension on on both sides of the roll. If the adjustment is not possible, the strip joint must be reconnected.
(2) The center line of the unit is skewed. The skew of the frame includes the skew of the center line of the frame and the high and low inclination of both sides of the frame, which will cause serious deviation and is difficult to adjust. This belongs to the installation quality problem of the unit. The installation quality has the greatest impact on the strip deviation, and the strip deviation caused by the installation error is the most difficult to deal with. A kind of
(3) he uneven pressure of the buffer roll of the tension device results in the inconsistency of the running resistance on both sides of the strip and the deviation of the strip. It is relatively easy to deal with this situation, as long as the pressure of all the buffer rolls and the roller of the unit is re-detected and adjusted.
(4) Running deviation caused by vibration in operation. The mechanical vibration of the unit is unavoidable in operation. The faster the speed of the steel strip is, the greater the vibration is, and the more serious the deviation of the steel strip is. During the operation of the production line, the vibration caused by the radial runout of all rollers in contact with the strip may cause the strip to run off.
(5) If the tension of steel strip is too large or too small, the tension value of each section of the unit should be recalculated and adjusted.
(6) The bearing of the steering roll is stuck, which causes the roll not to rotate, and the friction between the steel strip and the roll surface increases.
(7) The shape of steel strip is poor and there are too large sickle bends or wave edges.
(8) Processing errors on the outer surface of the roll are conical, sticky with dirt or uneven wear, resulting in different diameters, and the steel strip will run to the side with larger diameters. The force acting on the strip is shown in Fig. 3-7. The traction of the strip is F. It produces a moving component F toward the large side of the diameter, and under the action of the component F, the steel strip produces offset.
Processing method for deviation of B steel strip
In view of the reasons of steel strip deviation, the corresponding countermeasures should be adopted to adjust the deviation caused by installation errors. Firstly, the installation errors should be eliminated. The serious skew of the frame must be re-installed. Only on the premise of ensuring no installation errors can the adjustment plan be implemented for the running deviation.
(1) Clean up the dirt on the surface of the steering roll. If the processing error and uneven wear are not uniform, it is necessary to replace it and reprocess the coating treatment.
(2) The unit requires steady acceleration, no sudden acceleration or shock, and proper tension.
(3) Adding deviation correction rollers. This method can prevent the deviation caused by various reasons, especially by the absence of correcting rollers for long distance steel strip, but it will increase the cost.
(4) Tension adjustment. The adjustment of tension roll is a very important part of the unit deviation adjustment.
(5) Tighten the frame of the roll to prevent vibration caused by tension and acceleration.
In a word, as long as we strengthen routine inspection, clear up all kinds of factors causing strip deviation in time and grasp the law, we can find out the corresponding solutions to the phenomenon of strip deviation.
The working principle and forms of several kinds of deviation correction rolls are introduced in detail in Chapter 7 of this book.