Texturing is an important means of producing differentiated fibers, and the most common variety is drawn textured yarn. The common characteristics of this type of fiber are softness, stretchability, curlability and fluffiness. The packages wound after stretching and deformation are basically used as factory packaging and sent to knitting factories or weaving factories for use. Therefore, a series of necessary steps need to be taken in the winding mechanism of the stretching and deformation machine. Measures are taken to produce a package with high stability and good unwinding performance. This article focuses on issues such as overlap, shortening of stroke, convex edges, and bulging edges of stretched and deformed packages, and further analyzes the relevant issues mentioned in the literature.
1 Overlap problem
At present, the winding speed of texturing machines has reached 1000m/min, and is developing towards more than 1500m/min. In the winding mechanism of the stretch deformation machine, the package is frictionally driven by a friction roller, and the traverse device is driven by an independent motor. According to the winding speed relationship formula: α is the winding lift angle; V1 is the package surface speed; V2 is the traverse speed; H is the winding stroke; m is the number of traverses per minute; dk is the winding diameter; n is the package speed; i=n/m is the winding ratio.
Because V1 and V2 of the texturing machine are constants, the winding lift angle α remains unchanged. This is a kind of constant lift angle winding . As the winding proceeds, the winding diameter dk continues to increase, and the winding ratio i must gradually decrease and several positive integers inevitably appear. Whenever a positive integer occurs, the rear layer of wire loops is stacked on the front layer of wire loops, forming a so-called overlap.
In order to avoid overlapping, special anti-overlapping measures must be taken. It can be mechanical, that is, the stroke position is slowly moved axially in a small amount, and the winding position of the wire coil is constantly changed; it can also be electrical, such as superimposing an interference frequency on the transmission frequency to make the traverse speed faster. Change slowly to alleviate overlapping symptoms, among which the triangle wave disturbance signal is most commonly used.
The graphics above Figure 1 and Figure 2 in the literature are triangular wave disturbance signals that are not placed to prevent overlapping. It is a periodic non-stop triangular wave (it can also be a sawtooth wave, etc.) . However, the use of triangular wave disturbance signals is not enough “to achieve the best motion correction effect.” This can be seen not only from the intermittent and paused trend of the stroke correction in the graph below, but also from the ordinate in the graph, because DH is exactly the trave motion speed (Trave motion speed) or double stroke rate ( Double strike rate) means.
2 The problem of gradually shortening stroke
Low stretch yarn is a soft and stretchable filament. The tension during winding should not be too high, and it cannot be allowed to become loose in the package. In a completely tensioned state, it will affect the crimping performance of the silk. Therefore, if it is made into a straight-sided package, the stability of the reversing wire loops at both ends will be poor, which can easily cause spider webs or de-looping. If the two end surfaces of the package are made into inclined planes with an inclination angle between 5 and 15°, that is, the traverse stroke gradually changes from long to short from empty tube to full tube, the situation will be greatly improved.
The mechanism with gradually shortening stroke is composed of the following parts: (1) L-shaped pendulum – the rotor in the center of the pendulum is embedded in the spiral groove of a cylindrical cam, and reciprocates with the rotation of the cam Movement; the long arm of the swing bar is equipped with a wire guide to guide the filament to move back and forth; the wheel on the short arm of the swing bar is embedded in a swing guide rail, and the stroke of the wire guide changes with the different rotation angles of the guide rail. In order to beautify the appearance of the package, the guide rail angle is usually the largest when the tube is empty, and the winding stroke also reaches the maximum value. At this time, the reciprocating movement of the filament is not completely constant. When the bobbin is full, the guide rail is in a horizontal state, the winding stroke is the shortest, equal to the cam stroke, the filament moves back and forth at the same speed, and the filament is laid out most evenly. (2) The guide rail swing device can use a spatial linkage mechanism or a planar cam mechanism; when the winding diameter dk continues to increase and the bobbin swings, the angle of the guide rail gradually decreases and the guide wire stroke shortens.
It should be pointed out that the size of the inclination angle is directly related to the capacity of the package. The smaller the inclination angle is, the larger the packaging capacity is; the larger the inclination angle is, the smaller the packaging capacity is.
3 The convex edge problem
When the filament is wound, regardless of whether it is empty or full, it generally moves back and forth at a constant speed, and the winding density on the package is basically the same. However, when the package end is reversed, the reversing wire loop can be approximately regarded as an arc, and the winding density increases. Over time, more silk accumulates at the ends than in the middle of the package, forming convex edges. The gradual reduction of the package movement and the slight movement of the reversing position help to reduce the convex edge.
The best way to prevent the appearance of convex edges is to reduce the number of times the wire loop reaches the end of the package, and let the movement of part of the wire layer be indented by a certain value regularly. For example, in the FK6-700 machine, at the end The indentation value of the part is 10mm. When there is an appropriate ratio between the number of indented strokes and the number of non-indented strokes, the bulge condition can be eliminated. However, at the position where the stroke is retracted (such as 10 mm), a new convex ring appears because part of the reversing wire circle is transferred here, and the molding is still not ideal. This is the “first-level stroke correction” Condition. recently. Such as FK6-900 type, FK6-1000 type and 33H-1000 typeSome machines such as �� have been improved to “four-level stroke correction”, which disperses the indentation stroke in 4 positions (such as 13mm, 11mm, 9mm, 7mm), eliminating the possibility of convex rings appearing in the middle of the package. The new AFK2 type stretch deformation machine of Germany Barmag Company has further increased the stroke indentation to “six-level stroke correction”, and the anti-bulging effect is more ideal.
It can be seen that the indentation stroke is to prevent convex edges, but it cannot play the role of “preventing overlapping”, “ensuring the smoothness of the end face and surface, and increasing the density of the wire” .
4 Edge expansion problem
Although the winding tension when winding stretch textured yarn is not large, in order to obtain a well-formed package, it still needs to be under a certain winding tension. conduct. Moreover, during winding, there needs to be sufficient contact pressure between the package and the friction roller to drive the package to rotate normally. When the package is wound to a certain thickness, the centripetal pressure of the outer silk layer on the inner silk layer reaches a considerable level, causing the winding tension in a certain area inside the package to tend to disappear. Under the action of external centripetal pressure, the silk layer in this area has “no way to go” and can only expand outwards toward both ends along the axis of the package, forming a smooth drum shape or a stepped drum shape. As a result, the roll forming is damaged, and in severe cases, the length of the paper tube may even be exceeded. Therefore, during winding, the winding stroke near the easy-to-bulge area is preset to be shorter than the normal stroke. When the package is close to the full state, the inner silk layer is squeezed and bulges out. , so that the end face of the package is basically a slope, digesting the bulging edge, and improving the end face shape of the package.
For example, during constant-lift angle winding, the winding angle α remains unchanged. Even if various methods such as the swing frequency disturbance winding method to prevent overlap are used, the average value of the winding angle α should still be considered unchanged. Now, in order to overcome the edge swelling, a curve in which the winding angle α changes with the winding diameter dK is preset in the area prone to edge swelling. For the sake of simplicity, a fold line can be taken, and a number of folds can be taken from the empty tube to the full tube. point, as shown in Figure 1. In Figure 1, 6 points are taken between the winding diameter dk from the packaged empty tube diameter do to the full tube diameter dh. The starting point is slightly smaller than the empty tube diameter do, and the end point is slightly larger than the full tube diameter dH. The winding angle α modified by edge expansion changes within a small range (about 1°). The area “2~3” in Figure 1 is equiangular, but it can also be set to not be equiangular.
Therefore, the bulging of the package end face is solved by “hiding” the bulging method, rather than relying on “first-level stroke correction” or “fourth-level “Movement correction” to overcome.
5 Conclusion
Through the above discussion and analysis, it can be seen that:
Superimposing triangular wave disturbance signals is a method to prevent overlap, but does not prevent convex edges. Function;
The shortening of the winding stroke can prevent the occurrence of cobwebs, unwinding and defects;
Indenting the winding stroke and reducing the number of wire loops at the end of the package, It is an effective measure to prevent bulging. Multi-stage indentation is better than single-stage indentation. The surface of the package is smoother and the appearance is more beautiful.
The movement of the area with too small winding tension can be shortened and hidden. The bulging edge that appears on the package improves the shape of the end face of the package.
Therefore, the cause of the problem must be analyzed clearly and practical and effective measures must be taken to solve the actual problem of poor package forming. </p
