With the continue development on the popularize and promote of the smart phone and tablet PC applications.glass fiber cloth, as one of the main upstream raw materials in PCB field , is also increasingly development to the thin, ultra-thin type, And the requirements on the quality of the fiberglass cloth are getting higher and higher,In the air-jet loom weaving process of the fiberglass cloth , the relaxation of the warp yarns on both sides((Hereinafter referred to as loose edge) is a long-standing and troublesome problem in production. This article will address this issue on Analysis of Relevant Causes and Countermeasures.
Loose Edge Phenomenon
The loose edge phenomenon of glass fiber cloth refers to the fiberglass cloth weaving process, on the front of the machine, there has 5 or 8 counts warp yarn of the cloth edge is loose, the length direction is relaxation, the warp yarn is relaxation on the edge of the machine ,the most serious is the side of cloth ,So the yarn tension on both sides of the weaving yarn becomes smaller and the falling of the menstrual-stopping sheet causes the phenomenon of stopping.Usually, workers will be cut off the warp and butt the yarn in the processing of production,This will not only increase the fabric defects, but also increase the labor intensity .At the same time, due to the tension of the warp yarns becomes small, due to the insufficient tension of the warp yarn ,shrinkage defects can be easily produced in the weaving process.
Analysis for the Causes of Loose
The reasons for the shaft itself
In the whole pulp and by the process,The warp tension at the edge of the weave is less than the tension in the middle warp,Leading to loosening of the weaving yarn .
The bad tune in the production process,So that the diameter of the weaving shaft edge is slightly larger,when weaving, the length of the yarn to be sent increased, resulting in the relaxation of the side yarn .
In the first round of the shaft when the shaft bottom of the pad is too thick.
The weaving disc is deformed to change the shape of the side of the weaving shaft,In the weaving to form a lotus leaf edge, the tension of the edge warp while littler while larger, resulting in the relaxation of side yarn .
Glass fiber properties
Fiberglass yarns are made of hundreds of continuous glass monofilaments bundled together with very small twist and trace amounts of sizing agent (see Figure 1),as the characteristics of the glass monofilament itself are extremely smooth surface, and basically no flexibility, no elongation. In addition, Electronic cloth is mainly plain weave structure , Warp density is relatively thin (currently the most densely distributed in the industry by the density of 27. 5 / cm), and the warp, weft, twisted yarn are all glass fiber yarn so that Warp and weft between the friction resistance is small, it is difficult to fully twist does not produce relative slip (see Figure 2)
In the weaving process (see Figure 3), after the beating finished, the weaving of the cloth is from the weaving mouth to the time of the movement of the breastplate of the loom, and Weaving is continuing. As the heald frame of the continuous up and down movement, The warp yarns continue to be subjected to the ever-changing warp tension. In the weaving mouth office, Woven weft is constantly under the influence of the warp movement up and down so that the weft yarn further contraction bending, Because the weft yarn is basically inelastic, can not be elongated, and both sides of the twisted yarn can not be fully grasp the weft, The degree of bending of the weft yarn near the cloth edge becomes large, and the weft yarns closing the middle of the cloth face received more and more resistant from warp and the degree of the ability to continue to bend becomes smaller and smaller. Meanwhile, As the weft of the cloth edge of the degree of warp is greater than the middle of the weft, the edge of the weft on the warp yarn force is less than the middle of the weft on the force of warp so that the warp yarns on both side edges of the electronic cloth are less curved in the cloth surface than the intermediate warp yarns, and the edge of the heald frame at the back of the continuous “extension”, eventually leading to side yarn relaxation.
Particularly for the glass fiber electronic tissue (2116, 2113, 3313, 1080, etc.) and the ultra-thin fabric (1067, 106, 103, etc.), as the warp and weft yarn is finer, the warp and weft yarns on the fabric point are less curved, friction between each other is also smaller, so that the warp of both side edges is more likely to be relaxed. This is also seen in the air-jet loom on the menopausal halo on both sides of the lower mid-high slightly arc-shaped reasons. The author believes that this is also one of reason that Electronic cloth industry is always the middle of the fabric permeability is greater than both sides.
In addition, the wear of the rubber roller (or piera) at the breast beam of the loom is also one of the causes of loosening of the side yarn during the weaving process.
Strengthen the preparation process of production management, to ensure the quality of weaving axis
Using a twisted edge way of which has greater grip force on the weft,At present main twist ways in the fiberglass cloth industry are the leno twist and planetary twist,Such as the Tsudakoma loom is used in three yarn leno twist way, the Toyota loom using the planet twist way, In contrast, to the weft grip ,the three yarn leno twist is stronger than the planetary twist, and seen from the actual data of the factory, the edge of the loose side of the yarn may appear Sex smaller.
Change the edge of the law, increase the density of edge warp cloth , such as change (2.2.1) wear method (4.2.1) , as shown in Figure 4, However, this method should be based on different types of cloth, different strains of the test.To prevent the Alice edge caused by the excessive tension ,Due to the cloth with too thick or too tight side when cloth walking in the later procedure.
According to the thickness of different types of cloth, warp and weft yarn thickness and density, to adjust the twist yarn thickness, twist and twist tension,To increase the grip force on the weft. Also be careful not to make cloth edge too thick
Increase the number of waste side of the warp yarn and tension, in order to increase the waste side of the warp yarn on the grip force.
Adjust the time of the twist edge, in the case without affecting the weaving ,So that it can weft the weft earlier before weft insertion (i.e., before weft cutting).
Adjust action time of the the clamping mechanism and the electric shear,So that the position of the presser as close to the reed, adjust the action time of electric shear,So that the weft yarn is pressed by the blank holder before cutting the weft yarn,So as to reduce the degree of bending of the weft yarns side before being cut.
In the pre-preparation process to further increase the weaving side tension of the warp,we take a different approach for different tensioner , but try not to increase the mechanical friction of the yarn.
In the front preparation, the side warp yarns will use finer yarns to reduce the amount of side yarns to be weaved and to reduce the side yarn slack.
From the factory’s actual situation, through the integrated use of the above methods, the relaxation problems of glass fiber edge warp can be better improved,But for some special cloth,Such as the weft yarn is much finer than the warp yarn,Or 106 series even more thinner cloth,There will be individual loom relaxation or the edge relaxation phenomenon of the warp, which is our direction for the fiberglass cloth counterparts need to work together .