Custom Bulk Bags (CBB) products are made from woven polypropylene and the manufacturing process is the same, regardless of the end-user. Our bulk bags can be ordered with many optional extras to make them ideally suited to your industry and needs. The production process starts with polypropylene (PP) pellets and follows a multi-stepped procedure to create high-quality, customised bulk bags for a variety of clients.
Step 1: Extrusion
The raw materials (PP, calcium and UV-inhibitors) are mixed and melted together, then passed through an extrusion machine which creates long ribbons of PP tapes. These tapes are wound around industrial-sized bobbins and sent to the next stage.
Step 2: Weaving
The bobbins of PP tapes are loaded onto large weaving looms where the main body of the bulk bag is woven into shape. This woven fabric of PP tape is incredibly durable and strong, weighing between 65 grams per square metre and 240 grams per square metre. The fabric is also breathable, which means that moisture can pass through the weave. Additional loading and discharge spouts are woven in the same manner.
Step 3: Optional splash proofing
If a customer requires their bulk bags to be splash-proof, then the woven fabric is sent through an additional process where a special laminate coating is applied to the bulk bag. This coating protects water-sensitive granular products from spoiling due to moisture penetration.
Step 4: Cutting and trimming
Whether the woven PP fabric is treated for moisture or not, it is fed into the cutting machine where it is cut to specific sizes, depending on the bill of materials for the job. All the different components are cut using this automatic cutting machine, which utilises a ‘hot knife’ cut methodology. The cutting machines facilitate extremely precise cutting of components.
Step 5: Printing and finishing
Once the PP fabric has been cut to size, it is fed into a printing press. If a customer requires their logo, contact details or any other safety data to be printed onto the bag, we are able to print this directly onto the cut pieces using our four-colour inline flexographic printing presses. We are also able to match Pantone colours to suit the customers’ requirements. Bags can also be finished with slits, marks and folds, depending on the client’s needs.
Step 6: Loops and handles
All bulk bags have some sort of handle or loop attachment that allows the bag to be carried with a forklift. Heavy-duty tapes of PP fabric are woven into webbing belts. Strips of this strong belt are then cut to the right size and turned into loops and handles. Our loops are skillfully attached, by method of sewing, onto the predetermined position of each bulk bag, depending on the design.
Step 7: Sewing
This is the stage where all the pieces that make up the bulk bag are joined together by industrial sewing machines. This is the most labour-intesive part of the entire process. A highly-trained team of seamstresses sews the pieces together and the supervisors inspect each seam to make sure that it is tight, secure, straight and free from creases. This quality control is vital and allows us to manufacture world-class bulk bags with 5:1 safety ratings.
Step 8: Quality control and testing
Once the bulk bags have been inspected for quality by the supervisors, selected bags from each batch undergo testing for strength, durability and safety. This process ensures that each and every bag meets the high standards and requirements of our customers. Any defects or sub-quality bags are removed from the production line and sent to be deconstructed so that the materials may be reused in this manufacturing process.
The bulk bags that meet quality control standards are then compressed and grouped into batches for packing. A baling press squeezes the bags into a tight formation and they are bundled up, ready for shipping. Once received by the customer, the bales can be opened and the bulk bag removed easily for use.
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Custom Bulk Bags is a South African manufacturer of woven polypropylene bags for various industries, such as mining, chemicals and food. We are able to produce over 3.5-million bulk bags per year, keeping our customers in stock at all times. Our bags adhere to the highest levels of quality as a result of our stringent in-house testing and quality control programmes.
Custom Bulk Bags holds ISO 9001 certification and we currently have a number of UN-certified designs. We are a Level 3 B-BBEE manufacturer and supplier and fall under the ownership structure of Deneb Investments Limited. For more information on our products, contact sales@custombulkbags.co.za. Follow us on Facebook for our latest news and industry insights.
