I. Types of woven bag production lines. Woven bags are a type of plastic packaging, typically made from various chemical resins such as polyethylene and polypropylene. Plastic woven bags are primarily manufactured from polypropylene resin, which is extruded and stretched into flat filaments, then woven and formed into bags.

Overseas production is dominated by polyethylene (PE), while domestic production is primarily polypropylene (PP). Polyethylene is a thermoplastic resin obtained through the polymerization of ethylene; in industrial practice, it also encompasses copolymers of ethylene with small amounts of other olefins. Polyethylene is odorless, feels waxy to the touch, and exhibits excellent low‑temperature performance—its service temperature can reach as low as −70 to −100°C. It possesses good chemical stability and resists corrosion by most acids and bases (though it is susceptible to oxidizing acids). At room temperature, it is insoluble in common solvents and has low water absorption. However, polyethylene is highly sensitive to environmental stresses—both chemical and mechanical—and shows poor resistance to thermal aging. Its properties vary considerably depending on the grade, primarily determined by molecular structure and density. Different production methods yield products with distinct densities, ranging from 0.91 to 0.96 g/cm³. Polyethylene can be processed using standard thermoplastic molding techniques. It has a wide range of applications, chiefly in the manufacture of films, containers, pipes, monofilaments, wires and cables, and everyday consumer goods; it is also used as a high‑frequency dielectric material in television and radar systems. With the development of the petrochemical industry, polyethylene production has expanded, accounting for approximately one quarter of total plastic output. In 1983, global polyethylene production capacity stood at 24.65 million tonnes, with an additional 3.16 million tonnes under construction.

II. Process Flow of the Woven Bag Production Line. Compared with the plastic bag or blown‑film industries, the production process for plastic woven bags is somewhat more complex, and the return on investment is considerably higher. The manufacturing of plastic woven bags requires multiple pieces of equipment and a series of processing steps; each step is relatively straightforward to operate and master. The woven bag production equipment manufactured by Shuangda Machinery boasts excellent stability, easy maintenance, and enhanced safety.

The production process of plastic woven bags comprises several key stages, arranged in the following sequence: pelletizing, filament drawing, weaving, coating, printing, bag sewing, and packaging. Although a wide variety of woven fabrics are available on the market today, their manufacturing processes are largely similar.

III. Stages of the woven bag production line.

1. Plastic pelletizing process: The raw material for woven bags is first crushed by a shredder and then dried in a dryer. Next, the virgin plastic is fed into a pelletizing machine for extrusion, cooling, and pelletizing, ultimately producing plastic pellets—this constitutes the pelletizing stage.

2. Filament‑drawing stage: The molded plastic pellets are fed into a flat‑filament extruder, where they are processed into flat plastic filaments. These filaments are then wound up by a winding machine, completing the plastic filament‑drawing process.

3. Weaving Stage: Using circular knitting machines—available in four-, six-, eight-, and ten-shuttle configurations—plastic flat filaments are knitted into tubular plastic fabric; this constitutes the weaving stage.

4. Coating Process: Using a coating laminator, the resin is applied in its molten state onto the base woven fabric. Once the hot‑melt resin cools, a two‑in‑one laminated woven fabric is produced. In the production process of woven bags, this coating step ensures that the finished product provides practical benefits during use, such as moisture resistance, dust protection, and thermal insulation.

5. Printing Stage: Following the laminating process for plastic woven fabrics, the printing stage begins. The purpose of this step is to apply high-quality graphics, text, or advertising information onto the woven bags. Different models of plastic printing machines vary in the number of colors they can print, resulting in significant price differences.

6. Cutting, Seaming, and Bagging Stage: In the production process of woven bags, this stage involves cutting the continuous roll of woven fabric into lengths of specified dimensions, followed by seaming. At this point, the entire manufacturing process is complete, and the bags become finished products. Refer to the features of fully automatic cutting and seaming machines.

7. Packaging Stage: Finished woven bags are sold in bulk, and the packaging process involves placing them into standardized packages to reduce their volume, facilitating transportation and warehouse management.