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PP Woven Bags Manufacturing Process: How Sack Production Works

PP Woven Bags Manufacturing Process: How Sack Production Works

As the demand for durable and eco-friendly packaging solutions continues to rise, understanding how versatile PP woven sacks are crafted has never been more crucial.

So, join us as we delve into the PP woven bags manufacturing process and how they’re meeting the on-demand needs of modern consumers and industries.

Interested in our PP woven bags manufacturing process?

Our PP woven bags manufacturing process involves using premium polypropylene (PP) resin to create durable woven fabric, which is then printed, cut, and stitched into bags of various styles and sizes.

We prioritize quality control and sustainability, and our bags are reusable, recyclable, and made from eco-friendly materials.

Through this process, our promise to you is utilizing our advanced technology, skilled craftsmanship, and commitment to producing high-quality, environmentally responsible BOPP bags.

Our 10 step PP woven bag production process

Our manufacturing process of PP woven bags is a carefully orchestrated series of steps that result in the production of durable and versatile bags.

While we always seek continual improvement in our processes, these are the current steps we undertake to ensure we deliver the highest quality to you:

1. PP woven bags raw material

The first step in the PP woven sacks manufacturing process is ensuring we source only the highest-quality polypropylene (PP) resin, which is well-known for its strength and durability.

We still need to use additives to ensure these properties extend through to the final product and aren’t weakened during manufacturing.

With this in mind, the following additives may be used:

  • UV stabilizers: We add UV stabilizers to reduce the impact of exposure to sunlight during transportation, storage, or outdoor use, which can cause the bags to degrade and become brittle.
  • Antioxidants: Antioxidants prevent the degradation of the polypropylene resin due to exposure to heat, oxygen, and other environmental factors.
  • Slip agents: These reduce the friction of the woven polypropylene bags, making them smoother and easier to handle during production, transportation, and storage. Ultimately, it stops the bags sticking together and allows for easy stacking and handling.
  • Anti-block agents: In addition to slip agents, anti-block agents also prevent any sticking together but especially in high humidity conditions, improving bag separation and handling.
  • Colorants provide color and appearance via the use of pigments and dyes.
  • Flame retardants reduce flammability and make ensure our bags are more resistant to ignition and burning.

2. Melting the PP resin

We feed the PP resin pellets into an extruder, which is a machine that heats the resin to its melting point and then forces it through a die to form long, continuous flat tapes.

Melting the PP resin

During extrusion, we typically heat the PP resin pellets to a temperature that is above the melting point of PP, usually around 180-220°C (356-428°F). The exact temperature used may depend on factors such as the type of PP resin being used, the extrusion equipment, the desired properties of the final product, and the production speed.

We ensure careful control of the temperature to melt the PP resin uniformly and consistently, without overheating or causing degradation.

If this occurs, color changes, reduced strength, or increased brittleness can occur, while inadequate heating may result in incomplete melting and poor extrusion performance.

3. Forming & weaving the fabric

After melting the PP resin in the extruder, we force it through a die to form long, continuous flat tapes, which we then weave together. We may further control the temperature during the weaving process, depending on the specific loom and settings being used.

Forming & weaving the fabric

A weaving machine is then used to interlace the fabric in a criss-cross pattern. We do this by passing the tapes through a series of looms that interlace them, forming a tight, weave pattern.

This is achieved via the following process:

  1. Warping: We wind a PP tape or flat yarn onto a warp beam to create the warp, which is the set of parallel yarns that runs the length of the fabric.
  2. Shedding: The warp then passes through a shedding device, creating an opening or “shed” between the warp’s upper and lower layers. This allows the weft yarns to be inserted.
  3. Weft yarn insertion: We insert weft yarns or tapes through the shed using shuttles or circular looms. They’re inserted perpendicular to the warp yarns, passing through the shed and interlacing with the warp yarns to create the woven polypropylene pattern.
  4. Beating-up: A comb-like device called—the “reed”—then pushes the weft yarns tightly together. This “beating-up” process helps to create a tightly woven fabric.
  5. Repeat: We repeat steps 2 to 4 to create the desired fabric width and length.

Through this process, we use state-of-the-art circular loom machines to ensure minimal defects & lower energy consumption while maximizing productivity so we can keep costs down and pass on this benefit to our customers.

Ultimately, this step provides us with our PP woven fabric, which is the launchpad and foundation for our BOPP/woven bags.

4. Treatment, coating & printing

After production, the PP woven fabric can undergo additional treatment or coating to enhance its properties.

This is where we apply a layer of BOPP (biaxially oriented polypropylene) lamination film on one or both sides of the fabric. It is a thin, transparent, and high-strength material that allows for printing and customization, including branding.

We use advanced printing techniques that allow for customization with logos and other design elements to meet our clients’ specifications.

A typical process is as follows:

  1. Pre-press preparation: Specialized graphic design software is utilized to create text, images, and logos for printing on the PP woven bags. After finalizing the design, it is converted into a format suitable for printing, such as a digital file or a plate.
  2. Plate creation: If using traditional flexographic or gravure printing, we need to create plates. The design is then transferred onto plates, usually made of metal or other materials, through engraving or etching. We then mount the plates onto the printing press.
  3. Ink prep: We mix ink according to the required color and viscosity specifications.
  4. Printing: We then feed the woven bags into the press, transferring the ink onto the bags using the plates or other cylinders. We repeat this process until we apply all the different colors or layers of ink.
  5. Dry-cure: We cure or dry the ink after each application, depending on the method used.
  6. Post-press finishing: After printing we use heat-setting to cure the ink and improve its durability and apply a varnish or coating for added protection or glossiness.
  7. Quality control: Throughout this process, our QC measures ensure that the printed PP woven bags meet the desired color accuracy, print clarity, and other specs.We identify and address any defects or issues to ensure a high-quality finished product.

5. Cutting

Cutting the material can be done by either hot or cold cutting:

Heat Cutting

Heat cutting melts and seals the PP woven fabric edges to create clean and sealed cuts. The general heat-cutting process for PP woven bulk bags is:

  1. Preparation: We first lay out the woven fabric in multiple layers, aligning the bag panels according to the desired bag size and shape. We stack and securely hold the layers together to prevent movement during cutting.
  2. Tool setup: We set up and adjust a heat cutting tool, such as a hot knife or a heated wire, for the desired temperature and cutting depth. We control the temperature to ensure precise cutting without causing excessive melting or scorching of the fabric.
  3. Cutting: The heat melts and seals the fabric as it cuts through, creating clean and sealed edges. The cutting tool follows the desired cutting line, guiding along the fabric edges to create the bag shape. We take care to ensure uniform cutting and proper sealing of the edges to prevent fraying or unraveling.
  4. Cooling and setting: After cutting, we leave the heated fabric edges to cool and set. This process solidifies the melted edges, ensuring they are properly sealed and bonded. The cooling time varies due to the fabric thickness and cutting temperature.
  5. Quality control: We ensure that the cuts are accurate, clean, and free from defects. This involves checking for proper cutting depth, sealing quality, and bag integrity.
  6. Finishing: Finally, we trim excess threads.

Cold Cutting

The preparation, finishing and QC elements of cold cutting is the same as with heat cutting.

The biggest difference between the two processes is the elimination of heat during cutting. Instead, one uses a knife or blade to mechanically cut through the fabric without applying heat.

One of the benefits of cold cutting over using heat is the reduced energy consumption for the manufacturer. However, one can only apply this to coated material.

Cold cutting also reduces the risk of fraying, which can compromise the bag’s strength and durability. Even so, this doesn’t mean that heat cutting causes a weakness, since we ensure all our bags maintain the same integrity levels.

6. Sewing

The sewing process can differ greatly depending on the bag construction style (e.g., u-panel, 4-panel, or circular), bottom and top design, as well as the desired loops.

However, a typical process for sewing the bags is:

  1. Folding: The fabric is folded along the edges to form the sides and bottom of the bag, securing them in place with clips or pins.
  2. Stitching the sides: Sewing starts at the top, runs down the sides, with backstitching at the beginning and end for added strength.
  3. Stitching the bottom: After stitching the sides, we reinforce the bottom seam with multiple stitches or a double stitch for added durability.
  4. Handles or flaps: If handles or flaps are needed, we sew them securely according to the desired design and specifications.
  5. Finishing: We trim excess threads, QC the bag for loose stitches or flaws, and make necessary adjustments or repairs.

7. Inspection

Despite continuous inspections during the bag’s construction, a final check is essential to ensure the delivery of top-quality products to our customers.

This involves checking for proper stitching, reinforced stress points, handle alignment, absence of defects, and overall appearance.

8. Packaging

Once the bags pass inspection, we pack them in our secure and controlled environment. This includes stacking, bundling, or packing bags in boxes, bales, or pallets based on customer requirements.

Proper packaging is crucial to shield bags during transport and storage, ensuring they are ready for distribution or sale.

9. Labeling

Based on specific requirements or regulations, we label bags with essential information, including product details, brand, size, weight, and safety instructions for clear identification and traceability.

10. Storage

We then store your bags in our environmentally controlled, safe and secure facilities until they’re ready for shipment or distribution.

Our storage processes safeguard bags from environmental factors like moisture, heat, or sunlight, preserving their quality and durability.

Looking for an on demand PP woven bag supplier?

Need polypropylene woven bags on demand? As a leading supplier, Palmetto Industries excels in providing on-demand solutions for your woven polypropylene sacks needs.

With our state-of-the-art facilities and quick turnaround times, we efficiently fulfill custom orders of various sizes, designs, or quantities.

Our commitment to quality, reliability, and exceptional customer service sets us apart. Partner with us for hassle-free, reliable, and prompt supply.

tags: 1 Ton Builders Bags: Convenient Solution for Heavy-Duty Material Handling

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