작성자: Simin Xiang
Sewing is one of the most critical steps in the fibc bags manufacturing process — it is where a bag either holds its load or fails at the seam. Most fine powder leakage and tearing starts at poorly sewn seams, not the fabric itself. This article explains how thread specifications, stitch density, and seam construction work together to prevent that failure.
You will learn how sewing stages fit into the wider build. You will also see how thread weight, stitches per inch, and defect checks protect your product.
Woven polypropylene fabric is strong. The weak point is usually where two panels meet.
When a bag is filled, lifted, and stacked, load transfers through the seams. Poor stitching concentrates that stress and creates gaps. Fine powders like flour, cement, or lithium carbonate then sift out through those gaps.
A controlled sewing setup solves this. Correct thread, correct stitch count, and correct seam type keep the seam tight under pressure. This is why the sewing step defines real-world performance in the fibc manufacturing process.
Thread choice sets the baseline for seam strength. The wrong thread fails long before the fabric does.
Most FIBC seams use polypropylene or polyester sewing thread. Thread weight is measured in denier or tex. Heavier thread carries more load but needs matched needles and tension.
Tensile strength shows how much force the thread holds before breaking. Seam strength must align with the bag’s Safe Working Load. If the thread is weaker than the seam design, the stitch line fails first.
| Thread Factor | What It Controls | Practical Effect |
| Denier/Tex | Thread thickness | Higher load capacity |
| Tensile strength | Break resistance | Seam holds under lift |
| Material (PP/PE) | Chemical + UV resistance | Suits product type |
| Stitch tension | Thread tightness | Prevents puckering or gaps |
Stitch density means stitches per inch, often written as SPI. It directly controls how tight and sealed a seam becomes.
Too few stitches leave wide holes between thread points. Too many stitches perforate the fabric and weaken it. Most FIBC seams sit in a balanced SPI range that seals without tearing the weave.
Higher stitch density helps contain fine powders. Lower density suits coarse, heavy materials. Matching SPI to the product is a core part of proper fibc bag construction.
Sewing is not one action. It is a sequence of controlled stages performed on a dedicated fibc sewing machine.
Overlocking joins panels and wraps the edge to lock the weave. Single needle overlocking suits standard seams. Double needle overlocking adds a second stitch line for higher-stress joints and better load spread.
A filler cord is inserted along the seam during stitching. It fills the gap where fabric layers meet. This creates a leak-resistant seam and blocks fine powder from sifting through the needle line.
Lifting loops and base seams carry the heaviest stress. These joints use reinforced stitching and precise placement. Correct loop stitching supports safe lifting, which links closely to bag design choices like stevedore straps for FIBC handling.
Defect checks confirm that each seam meets its spec before shipment. This stage protects both the product and the buyer.
Inspectors watch for skipped stitches, loose tension, uneven SPI, and frayed thread. They also check seam alignment and loop attachment strength.
Manufacturers run visual checks and sample-based testing. Drop tests and load tests confirm seam performance against the rated Safety Factor. These controls are essential across the fibc bags manufacturing process, where seam integrity decides safety.
Large-scale buyers need proof, not promises. Traceability turns sewing quality into documented evidence.
Each bag can carry a QR code that records its production history. This links raw material, weaving, coating, and sewing data to a single unit.
Traceable production lets buyers audit quality and trace any issue to its source. It reduces risk in food, pharma, and chemical supply chains. Matching bag type to application also matters, so reviewing the FIBC 백의 종류 helps buyers specify correctly.
Strong FIBC seams come from matched thread, correct stitch density, filler cord sealing, and consistent defect checks. Traceability then proves the quality to every buyer.
XIFA 그룹 is a packaging manufacturer producing PP woven fabric, BOPP bags, FIBC big bags, and PE film bags. With a 72,000 m² facility, 800-plus skilled workers, and QR traceability on every bag, XIFA supports food, chemical, agricultural, pharmaceutical, and industrial packaging needs. Certifications include BRCGS, ISO9001, ISO14001, OHSAS18001, and food-safety standards such as FDA, FSA, and ISO22000.
우리의 탐색 FIBC collection to specify the right bag for your product.
FIBC bags usually use polypropylene or polyester sewing thread. The thread must match the fabric strength and the bag’s Safe Working Load to keep seams intact during lifting and stacking.
Stitch density controls how tightly a seam is sealed. Correct stitches per inch stop fine powder leakage without perforating the fabric, balancing seam strength and containment for the intended product.
A filler cord is a thread inserted into the seam during stitching. It fills the gap between fabric layers, creating a leak-resistant seam that blocks fine powders from sifting through.
