The causes of yarn leakage and insertion faults during the installation of large rolls of roving
As the size of the roving roll increases, it is easy to experience "yarn shedding" and "yarn insertion" faults during large yarn production.  
Mao Sha: The reasons for the occurrence of "Mao Sha" include:
(1) Improper adjustment of the winding tension of the roving (the winding tension must conform to the law of increasing tension from small yarn to large yarn, otherwise internal looseness and external tightness will inevitably cause yarn leakage faults. Using "constant tension spinning" to claim the "advanced" technology of roving tension control can easily lead to misunderstandings);
(2) The axial winding density of the roving is too low or too high;
(3) The yarn twist coefficient is too small;
(4) Roving shoulder detachment (forming angle too large or too small, failure to quickly and timely change the direction of the upper rib, lifting and stopping of the upper rib, excessive axial movement of the ingot wing pressure palm);
(5) The number of turns of the roving on the arc arm of the ingot wing pressing palm is insufficient;
(6) The steel pressure palm was deformed due to impact and not corrected in a timely manner;
(7) False twisting device failure or insufficient spinning tension, resulting in poor false twisting effect;
(8) The feeding amount of cotton strips is too light, and the winding tension decreases when spinning to medium and large yarns;
(9) The relative humidity is too low;
(10) Failure to connect the broken yarn in a timely manner: If more than two layers of yarn are connected, the winding tension of the ingot will significantly decrease.
In addition, the anti slip thread design of the tube should be male thread. If the tube is too old, the spinning and sliding threads at both ends will wear flat, lose their anti slip function, and also cause yarn leakage faults.
Insertion of yarn: Cotton spinning roving machines currently use tube guided winding method. The linear velocity of the roving winding point is greater than that of the yarn pressing point of the gripper, and the difference in speed is equal to or slightly greater than the output speed of the front roller roving. Therefore, it is impossible for the gripper to insert the roving during normal winding. But after the occurrence of yarn shedding, the diameter of the yarn winding at the shedding point becomes smaller, the yarn becomes loose, and the yarn guide mouth of the gripper is carried into the loose yarn layer by the yarn, forming "yarn insertion". In severe cases, it can cause deformation of the spindle wing yarn guide arm in the direction of rotation, and even lead to yarn guide arm breakage accidents. Therefore, the so-called 'pressing the palm to insert yarn' actually means that the yarn is inserted first and then inserted, and the yarn does not appear or insert.
When using aluminum pressure palm for the ingot wing, the thickness of the pressure palm leaves is relatively large, making it difficult to be hung into the coarse yarn after the yarn is blown; Aluminum pressure palm is prone to breakage, causing the "inserting yarn" to break, which has led some factories to believe that aluminum pressure palm is superior to steel pressure palm. Aluminum roller arm is not wear-resistant and prone to grooves. When the spinning variety changes and the number of turns of the yarn on the roller arm needs to be changed, the roller arm needs to be updated.
At present, almost all foreign roving machines use steel rollers. In response to the actual situation of spinning mills in China, the spinning of multi-component fibers (cotton, linen, wool, synthetic fibers) is increasing. When spinning linen, wool, and synthetic fibers, the aluminum roller arm is prone to wear and groove formation, while the steel roller has better wear resistance, anti shedding, and yarn insertion ability than the aluminum roller.