Factors Affecting Yarn Splitting Uniformity of Yarn Splitter Machine
Uniformity is the core quality index of finished yarn processed by yarn splitter machine. Whether it is used for weaving, knitting or making industrial textiles, uneven split yarn will bring a series of continuous problems in the subsequent process: uneven fabric density, local thin and thick spots, unstable dyeing color absorption, frequent yarn breakage on loom. Many textile factory technicians spend a lot of time debugging the yarn splitter machine, but the splitting uniformity still cannot reach the expected standard. In fact, the splitting uniformity is affected by multiple factors, which can be divided into four dimensions: raw material factor, equipment structure factor, process parameter factor and workshop environment factor. Only by sorting out all influencing factors one by one can the stability of production be improved systematically.
The first influencing factor comes from the raw mother yarn itself. The yarn splitter machine carries out splitting processing on the basis of the original strand structure of the mother yarn. If the mother yarn itself has uneven strand arrangement, inconsistent internal twist and local thickness difference, even the most stable yarn splitter machine cannot process perfectly uniform split yarn. For example, the mother yarn wound on the large package has loose and tight winding layers. When the yarn is unwound and fed into the splitting area, the unwinding tension will fluctuate periodically. This fluctuation will be directly transmitted to the splitting blade group, resulting in inconsistent stress of each sub-strand after splitting. Therefore, incoming inspection of mother yarn is a necessary process before splitting production. The factory can test the twist variation, package hardness and strand integrity of each batch of mother yarn, and formulate different splitting schemes for raw yarn with different quality grades.
The second factor is the manufacturing accuracy and assembly state of the yarn splitter machine. The core splitting unit is composed of yarn guide wheel, tension roller and splitting blade group. The coaxiality of the main shaft, the parallelism between the blades and the roundness of the guide wheel will all act on the yarn. If the yarn guide wheel has eccentric rotation, the yarn will periodically shake left and right when passing through, so that the position of the yarn entering the blade changes constantly, and the splitting boundary is blurred. If the blade group is not installed in parallel, the gap between adjacent blades is inconsistent, the yarn strands at the wide gap are loose, and the strands at the narrow gap are excessively squeezed, which eventually leads to different fineness of each split yarn. In addition, the dynamic balance of the rotating parts of the yarn splitter machine cannot be ignored. Unbalanced rotating parts will produce periodic vibration during operation, and the vibration will disturb the stable tension state of the yarn. This kind of vibration problem is more obvious when the equipment runs at high speed.
The setting of process parameters is the most adjustable part in daily production. The main adjustable parameters of the yarn splitter machine include feeding speed, front and rear tension, blade pressure and unwinding resistance. The matching relationship between these parameters is very important, and cannot be adjusted independently. If the feeding speed is increased blindly without adjusting the tension synchronously, the yarn cannot pass through the splitting area stably, and the probability of strand crossing and wrong splitting increases. If the tension is set too large, the yarn is in a tight stretching state, the elastic recovery space is reduced, and the yarn is easy to retract unevenly after splitting, which changes the actual fineness. Different fiber materials have different response to tension. Polypropylene yarn is soft and has large elongation, so the tension setting should be low; polyester industrial filament has small elongation, which can bear relatively higher tension. Experienced technicians usually take the method of gradient test, fix other variables first, adjust a single parameter in a small range, and test the uniformity index of the split yarn after each adjustment.
Workshop environmental factors are easy to be ignored by many production teams. Temperature and humidity will change the physical properties of fiber materials. In a low-humidity environment, synthetic filament yarn is easy to generate static electricity. Static electricity will make the split yarn strands attract and adhere to each other, cannot be separated neatly, and the yarn is prone to disorder and winding. When the humidity is too high, some yarns will absorb moisture and expand, the friction coefficient between yarn and metal parts increases, and the feeding resistance changes. The suitable humidity range for most yarn splitter machine workshops is controlled between 55% and 70% relative humidity. At the same time, the workshop shall avoid strong air flow blowing directly on the splitting area of the yarn splitter machine. The wind generated by the fan or air conditioner will blow the light yarn strand to shift, destroying the stable splitting state. The ground foundation of the equipment installation also matters. If the foundation is not firm, the vibration of adjacent looms and twisting machines will be transmitted to the yarn splitter machine, interfering with the splitting accuracy.
The operation behavior of the operator also belongs to the human factor affecting uniformity. When loading the yarn package, the coaxiality between the yarn bobbin and the unwinding frame is not adjusted properly, the yarn will swing during unwinding. When threading, the yarn is not embedded into the yarn guide groove and blade gap according to the standard route, and the yarn is offset, which will cause continuous defective products. Therefore, standardized SOP operation documents shall be formulated for the yarn splitter machine, and the threading steps, yarn loading requirements and parameter confirmation items shall be clearly written. Each shift needs to sample the split yarn regularly, use the yarn fineness tester and microscope to check the strand separation state, and record the test data. Once the uniformity exceeds the tolerance range, stop the machine in time to check the cause, instead of waiting for a large number of defective products to be produced.
It should be noted that there is no absolute zero-error splitting in the actual production. The factory needs to formulate a reasonable tolerance standard of splitting uniformity according to the downstream customer’s requirements. For ordinary woven fabrics, the tolerance can be appropriately relaxed; for high-end industrial yarn products, the control limit of deviation should be stricter. Clarifying the acceptable range can guide technicians to judge whether the state of the yarn splitter machine is normal, avoid repeated useless debugging and affect the production efficiency.
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