Before reaching the spinning yarn, the roller jaws can be held stably without slipping, that is, without “hard ends” appearing. This seems to be difficult to achieve under the existing conditions. From the perspective of drafting theory, avoiding “hard ends” means properly handling the contradiction between holding force and drafting force or guiding force and control force. During the drafting process, as long as the minimum holding force is always greater than the maximum drafting force and the guiding force of floating fibers on the front jaw line is always greater than the control force, it is an ideal drafting state. High elasticity is the basis for low hardness of rubber rollers, otherwise plastic deformation will occur; however, according to current technology, nitrile rubber cannot achieve elastic recovery at a smaller hardness (currently unable to achieve lower than Shore A60). The hardness of the polyurethane rubber roller can reach Shore A55. The elastic recovery is better than the existing nitrile rubber roller and it is more wear-resistant. The regrinding cycle can be increased by 3 to 4 times. The surface roughness can be appropriately high without affecting the dryness. and anti-winding effect. For compact spinning, this performance requirement is higher, because the compact spinning equipment does not have a cleaning roller, so the winding has a greater impact on its yarn quality.
How to strengthen the grip between the front roller and the rubber roller in actual production?
At present, the widely used low-hardness and high-elastic rubber rollers can basically meet the requirements under flexible technology. However, some factories use excessively tight spacing to balance the drafting force, causing the front rubber roller to be over-pressurized, leading to the abnormal phenomenon mentioned in some papers that the thicker the paint ratio, the better the consistency. This kind of excessive increase in holding force does not increase the drafting force simultaneously, but causes poor elastic recovery of the rubber roller. The extension of the anti-enveloping arc changes the displacement of the speed change point, destroys the evenness CV value, and increases the spindle difference. In addition, the existing drafting device technology often has excessive feed ration and excessive draft multiple, resulting in a corresponding increase in yarn defects and hairiness; too small spacer blocks or spacer block control rods will also cause short and thick slubs. Increase.
The ideal holding state is to ensure that the front rubber roller is “smooth, smooth, cool and dry”, and the surface roughness can be controlled to be large. The roughness Ra value is less than 1.0μm, that is, the hardness of the rubber roller meets the elastic recovery requirements during drafting, such as using a low-hardness polyurethane rubber roller. In addition, if there is a breakthrough in the front roller manufacturing technology: the existing helical teeth will be changed to herringbone cross teeth to balance the friction transmission force of the front rubber roller left and right, or the working surface of the jaws will be covered with wear-resistant semi-elastic body to make the upper and lower elastic grips Holding, the front gear can be held reliably with less pressure. Another important condition for maintaining the stability of the front jaw is the stability of the upper and lower aprons to control the fiber. That is, using reliable equipment to ensure that the upper and lower aprons operate synchronously and without slippage can meet the spinning draft stability requirements. . </p
