Manufacturing Process of Plastic Bottom-Sealed Bags

　　 Plastic Bottom-seamed pocket The weaving process consists of the following steps: yarn hanging, yarn threading, yarn shedding, lifting, winding, and unwinding. First, the warp yarns are drawn from beneath each spindle on the warp beam. For bottom-seamed bags, the warp yarns pass through the porcelain eyelets on the warp beam, then through a long vertical plate, a hemming roller, an unwinding guide roller, a grooved roller, a second long vertical plate, a tension roller, another porcelain eyelet, a pull rod, a jute cord, and a round steel buckle—each step requiring careful alignment to ensure proper fabric formation as the warp threads circulate. The weft yarns are loaded into the shuttle magazine. Once the machine is started, the shuttles move in a reciprocating motion driven by the shuttle-feeding mechanism. The warp-feeding system works in close coordination with the shuttle-feeding mechanism to produce cylindrical, flat fabrics. In the case of bottom-seamed bags, the woven fabric is lifted upward by the drawing-off device at the top of the loom, passes over guide rollers, and is then wound up by the winding device located behind the warp beam. When the diameter of the wound coil reaches approximately 1.2 meters, the yarn is released and sent on to the next processing stage (typically every 24 hours).

　　Plastic-seamed bottom bags: Factors affecting the knitting quality of seamed-bottom bags include the sizing ring, the warp and weft density adjustment mechanism, and yarn arrangement. Whether the ring size conforms to specifications directly determines whether the width of the grey fabric meets the standard. Typically, the deviation between the circumference of a standard-size ring and twice the standard fabric width should be within 3 mm. Warp and weft density is primarily controlled by the gearing system, with different weft yarns requiring different gear settings. Measurement is then based on the number of threads per 100 mm. The yarn arrangement in seamed-bottom bags must be uniform; unevenness can lead to yarn entanglement, resulting in fabric shrinkage, wrinkling, an unsightly appearance, and substantial waste.

　　Knitting technical specifications for bottom-seamed pockets:

　　The weaving density of a bottom-seamed pocket refers to the number of warp and weft yarns per 100 mm × 100 mm of woven fabric. The standard specifies both the weaving density and its tolerance. Commonly used woven fabric densities include 36 × 36 per 10 cm, 40 × 40 per 10 cm, and 48 × 48 per 10 cm.

　　Plastic Bottom-seamed pocket The unit area weight of woven fabrics, expressed in grams per square meter, is a key technical indicator for bottom-seamed bags. The weight per square meter is primarily determined by the warp and weft densities and the fineness of the flat yarns, which in turn affect the fabric’s tensile strength and load-bearing capacity; it is also a major factor that manufacturers focus on when controlling costs.

　　For woven fabrics, they can simultaneously withstand tensile loads in both the warp and weft directions, which are referred to as warp-direction and weft-direction tensile loads.

　　Plastic bottom-seamed bags: The width of various woven fabrics directly affects the bottom-seaming process. For tubular fabric, the width is expressed as the fold line; the meridian equals half the circumference.

　　Plastic Bottom-seamed pocket : Qualified bottom-seal bags produced in the preceding process are printed with product-related information by a printing machine, and then cut to the dimensions required by the customer using a bag-cutting machine. Loose edges are not permitted on bottom-seal bags, and printing is not required by the standard. Enterprises should establish their own printing standards based on customer requirements, taking into account factors such as the types of printing equipment available, the types of printing inks used, and the printing capacity. Since most enterprises use letterpress printing, their printing standards can be formulated in accordance with relevant standards and the specific requirements for letterpress printing. In the production of food-grade plastic bottom-seal bags, particular attention must be paid to controlling solvent residues in the ink.