How Are Bulk Bags Manufactured?

Bulk bags or flexible intermediate bulk containers (FIBC) are a common type of container used to store and transport dry bulk materials such as agriculture products, sand, gravel, and cement. These bags are typically made from woven polypropylene fabric and can range in size from cubic yard bags to large bags that hold hundreds or thousands of pounds. In order for bulk bags to meet certain specifications, it must be made appropriately. For example, to be able to hold 4,000 lbs safely, the manufacturing process to build the fabric has to be stringent to be able to withstand the immense force which it will be subjected to. Also, certain reinforcements have to be sewn in to ensure seams or lift loops do not fail. Below we discuss all the steps needed to during the bulk bag manufacturing process from the beginning to the end. Also, quality control inspectors are reviewing each step of the manufacturing process to ensure nothing is missed.

Polypropylene extrusion

is where the solidified resin is fed into an opening device where it is drawn into long thin strands called “filaments.” These filaments are then brought together and intertwined to form a “yarn.” These yarns will be used to make circular shaped bags, U-panel, four panel or baffle bags.

Polypropylene weaving

is the process where the yarn is then woven on a loom to create woven pp material for the bulk bag. The number of yarns used and the way they are woven together will determine the strength and weight of the fabric. This is an important step to ensure the bag is using the correct fabric weight to hold the amount of weight intended for the bulk bags. Many industries such as sand load 4,000 lbs or more in these bags, so they must be able to withstand extreme weights.

Optional Coating

is the next step and not all FIBC bags will have a coating applied during the manufacturing process to create laminated bulk bags. This is only if the bag will be utilized for a powdery product where the product could sift through the fabric.

Coating is used in industries like Pharmaceuticals for batching in bulk bags and Food Grade companies loading flour or sugar in bulk bags, This step applies another coat of polypropylene to further laminate coated bulk bags to close off any imperfections in the weave.

Bulk bag cutting

is the next step, and this is where the polypropylene fabric will be cut to size via the automatic cutting machine according to the specification of the bags being manufactured. Most manufacturers are heat-cutting the fabric to ensure there is no fraying when cutting to create quality fibc bulk bags.

Industries such as pharma and food grade load products which are ingested by humans. When working with these types of industries, it is important to ensure there are not foreign particles in the bags after production.

Heat cutting the fabric eliminates the fraying which is possible when cutting.

Bulk bag sewing

is when the fabric is gathered to make the actual bulk bag. This is a manual process, and it is very time-consuming. A worker will use a needle and thread to sew the fabric together. The bulk bag will then be turned inside out so that the seams are not visible.

The next step is to add the handles. Handles are usually made from polypropylene webbing. They are sewn onto the bulk bag so that they can be used to lift it.

The final step is to add a label to the bulk bag. This label will contain information about the size of the bag, instructions on handling the bags, and how much weight it will safely transport.

Pre-Shipping

is where the bags are complete and will be blown out to remove any remnants of thread or any other foreign materials. They will also be inspected one last time for any imperfections. Then, they will be highly compressed and loaded onto a pallet for shipping the packed bulk bags.

Shipping

is where the bags are loaded into the container for shipping overseas to the respective customer. This is done by either bulk loading or piecemeal. The bags are usually stacked on top of each other in the container. Once it is loaded the container is sealed and is ready to load on the cargo ship.

As you have seen by watching some of the steps in the bulk bag manufacturing process, producing these Fibc bags is a very manual process. This is why many ISO processes are enforced from the beginning where there is just raw materials to the end of the bag assembly process.

Most bulk bags are made overseas where manual labor is cheaper, as there are many different Fibc bag styles to make each day. They may be making duffle top bags one day and spout top bags the next, so the bag manufacturing is random and takes many controls to ensure they are made correctly.

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We source many containers of bulk bags for a number of companies, so call us if you would like us to quote your business.

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