The weaving process of PP woven bags requires multi-stage collaborative optimization to significantly improve its surface smoothness. This process involves systematic improvements from raw material handling and equipment adjustment to process parameter control. The core objective is to reduce problems such as twisting, loosening, and uneven density during warp and weft weaving, providing a stable substrate for subsequent printing or lamination processes.
Raw material selection is fundamental to improving smoothness. The melt index of PP resin directly affects the tensile properties of the flat yarns. Raw materials with moderate fluidity must be selected to ensure that the flat yarns form a uniform cross-section during stretching. If the raw material's fluidity is too poor, the flat yarns are prone to uneven thickness, leading to inconsistent warp and weft weaving density; if the fluidity is too high, the tensile strength of the flat yarns decreases, making them prone to breakage during weaving. Furthermore, adding antistatic agents can reduce electrostatic adsorption between flat yarns, avoiding surface unevenness caused by dust adhesion or yarn tangling; adding internal lubricants can reduce the coefficient of friction of individual filaments, improving the smoothness of the PP woven bag surface and providing a smoother base for subsequent printing.
Precise control of the yarn drawing process is crucial. By adjusting the speed ratio of the traction gears in the drawing machine, the tensioning speed of the flat yarn can be increased, resulting in more uniform stress on the monofilament during stretching and reducing loosening deformation caused by insufficient tension. Simultaneously, increasing the oven temperature stabilizes the molecular structure of the flat yarn after constant-temperature setting, enhancing the tensile strength and straightness of the monofilament. This step requires adjusting temperature parameters according to the raw material characteristics; for example, PP materials are typically controlled within a suitable temperature range to avoid material degradation due to excessively high temperatures or insufficient setting effect due to excessively low temperatures.
Optimizing the synchronization of weaving equipment is crucial. The speeds of the take-up machine, speed regulator, and drawing machine must be precisely synchronized to ensure consistent tension of the spindle rolls during take-up. If the take-up speed is too fast, the weft yarn will be overstretched and rub against the warp yarn, causing localized bulges; if the speed is too slow, the loose weft yarn is prone to forming "bulges." Furthermore, adjusting the diameter of the wound flat yarn and balancing the tension of the four shuttles' weft yarns can prevent uneven warp and weft interlacing caused by differences in tension between individual shuttles. The diameter and material of the springs on the circular loom also need optimization. Using high-elasticity alloy materials and standardizing specifications can enhance the spring's elasticity durability and prevent insufficient elasticity due to spring aging, which can lead to yarn twisting.
The precision of the fit between the cam and the comb teeth directly affects the warp and weft force balance. When the cam rotates, the contact pressure with the four combs (warp yarn combing components) must be evenly distributed. If the local pressure is too high, the warp yarns will be bent; if the pressure is too low, the warp yarns will easily shift, ultimately resulting in an uneven surface on the PP woven bag. By grinding the cam contact surface and adjusting the comb tooth spacing, consistent force can be achieved on each warp yarn, eliminating yarn twisting and misweaving. At the same time, the weaving track of the circular loom should be inspected regularly. If wear or deformation is found, it should be replaced or repaired promptly to prevent the shuttle from shifting due to uneven track, affecting the weft yarn interlacing accuracy.
The cleaning and lubrication of the guide yarn assembly are equally important. Dust accumulation or insufficient lubrication in components such as the guide holes and guide wheels can increase the frictional resistance of the flat yarn, causing "jamming" during monofilament operation and resulting in uneven stretching. Regular cleaning of the guide components and application of specialized lubricant are necessary to reduce friction between the monofilament and the equipment, ensuring stable tension of the flat yarn during weaving.
Tension control during the take-up stage is the final guarantee. By improving the gears and number of teeth on the take-up frame torque motor, the winding force is enhanced, balancing the warp and weft threads and ensuring smooth operation of the winding shaft. Insufficient winding tension can lead to loosening and deformation of the finished product; excessive tension may cause flat yarn breakage or overstretching of the PP woven bag surface. Therefore, the winding tension parameters must be dynamically adjusted according to the thickness and specifications of the PP woven bag.
Through systematic measures such as raw material optimization, improved drawing process, enhanced equipment synchronization, optimized cam comb tooth matching, maintenance of the guide assembly, and control of winding tension, the surface flatness of the PP woven bag can be significantly improved. This process not only requires advanced equipment but also relies on precise control of process parameters to ultimately achieve a comprehensive quality upgrade from monofilament to finished product.
