What Is a Gusset Bag?

A gusset bag, often called a “block-bottom bag” or “side-fold bag,” is a type of packaging bag with folded pleats on both sides. When filled, these pleats expand outward. This gusset structure increases the bag’s capacity and allows the bag to stand upright on flat surfaces. Gusset bags are widely used for packaging granules, powders, coffee, rice, pet food, chemicals, and industrial materials.

Comparison With Other Bag Types

Three-side-seal/Four-side-seal bags: Fixed capacity with limited flexibility. Gusset bags can expand and offer stronger load-bearing capability.
Stand-up pouches: Better for retail display, but gusset bags offer larger volume and more stable stacking.

Working Principle of a Gusset Bag Packing Machine

A gusset bag packing machine automatically completes bag forming, opening, filling, side gusset (fold) shaping, sealing, and discharge.

Core Workflow

1.Bag Picking
A robotic arm with vacuum suction cups picks up a single pre-made, flat bag from a magazine or stack.

2.Bag Opening
The same arm, sometimes assisted by clamps or air blowers, opens the bag mouth to create a wide entry for filling.

3.Product Filling
The opened bag is positioned under a filling nozzle. Different filling systems are used based on product type:

• Powders: Auger (screw) fillers for accurate dosing
• Granules: Linear weighers or multi-head weighers for high-speed portioning
• Liquids: Pumps or piston fillers

The system is synchronized with the machine to ensure accuracy and prevent spills.

4.Gusset Forming (The Key Differentiator)
This is the defining step. Mechanical forming plates and guides precisely fold the side pleats inward, shaping the gussets that create a flat, stable base and structured sides.

5.Sealing

• Side Sealing (for pre-made bags): May be used to secure the gusset area.
• Top Sealing: Heat sealing closes the bag after filling.

6.Discharge
The finished, filled, and sealed gusseted bag is released onto a conveyor belt or collection table for further steps like boxing or palletizing.

Types of Gusset Bag Packing Machines

Pre-made Gusset Bag Packing Machines

Available in rotary or horizontal designs.
Ideal for high-speed, hygienic, and flexible production environments.

Comparison With Vertical FFS Machines

Both can increase package volume, but:

• Gusset bags are suitable for large and heavy packaging.
• Stand-up pouches are better for smaller retail items.

Comparison With Pillow Packing Machines

Pillow packing machines form bags from roll film but cannot create stable side gussets. They are more economical but cannot handle heavy or large products.

Material Compatibility

Common laminates include:

• PET/PE
• PET/AL/PE
• Kraft paper laminates

Gusset bags require films with good stiffness to maintain the folded shape.
Flat pouches do not require such stiffness.

Application Scenarios

Gusseted bags are ideal for:
Food: Coffee beans, rice, grains, sugar, flour, nuts
Pet Care: Dry pet food, bird seeds
Chemicals & Industrial: Laundry detergent, fertilizers, construction materials (sand, grout)
Agriculture: Seeds, animal feed

While stand-up pouches dominate retail shelves for smaller goods, gusseted bags remain the workhorse for bulk, industrial, and heavy-product packaging.

Summary

A gusset bag packing machine automates forming, opening, filling, side gusset folding, and sealing. Compared with flat pouch machines, gusset bag machines contain more complex folding modules but deliver higher output, better stability, and stronger stacking performance.

If you’re looking for a reliable solution for high-capacity gusset bag packaging, contact us today to learn more about our Gusset Bag Packing Machine and get a customized quotation for your production line.